This work presents a liquid crystal (LC) based phase shifter in a dielectric waveguide (DW) topology consisting of core and cladding for the W-band. For continuous tunability, a part of the core material is replaced by liquid crystal. Furthermore, suggestions of materials for designing such a DW, i.e. for core and cladding, are given in this paper. In comparison to other topologies, the advantage of this topology is that the necessary electric biasing can be realized easily, by placing electrodes directly on the cladding. With an electric biasing of +-550V, a maximum differential phase shift of 430°, accompanied with insertion losses between 2.8 to 5.5 dB with standard WR10 connections, could be achieved. The maximum figure of merit is around 100 °/dB at 102 GHz.

This work presents an interference based W-band single-pole double-throw (SPDT) in rectangular waveguide and liquid crystal technology. In radiometers, this kind of SPDT can be used e.g. for switching to the calibration load for power calibration. The SPDT is designed with an E-plane power divider, two different paths for the phase shifting regions, being separated by 30mm to provide enough space for the used magnets for proof-of-concept, and a coupled line combiner, where the interference is taking place. Rexolite 1422 is serving as liquid crystal cavity. The matching is better than −12 dB between 88 GHz to 110 GHz, except a peak around 102 GHz. The insertion loss is less than 3 dB between 89GHz to 105 GHz, while exhibiting an isolation of at least 9 dB in this frequency range. From 90GHz to 100 GHz, isolation is even between 10 dB to 12 dB.

This paper presents an in-plane hollow waveguide crossover for W-band frequencies. It can be implemented e.g. into a Butler matrix, to simplify the fabrication process significantly. It is based on a partially dielectric filling of the waveguide, focussing the field in the center. The dielectric is placed in the center of a hollow waveguide crossing and has a star-shape. Inside the dielectric filled region, a higher order mode propagation is possible, which has no significant influence on the overall performance of the crossover. It shows an insertion loss between 0.8 dB to 1.0 dB in the frequency range of 100 GHz to 109 GHz, while the matching is better than −12 dB and even down to −30 dB at 108 GHz. The isolated ports show transmission coefficients better than −20 dB in the frequency range between 99 dB to 109 dB and even down to −40 dB around 107 GHz.

This paper proposes a low loss and self-packaged patch coupler based on substrate integrated suspended line (SISL) platform. Due to the benefit of self-packaging, the radiation loss of the patch can be reduced to the minimum. By cutting out the sub-strate as much as possible while ensuring mechanical strength, the dielectric loss will be further reduced. By connecting the metal layers on both sides of the substrate with via holes, the conductor loss can be further reduced. The measurement results and the simulation results of the fabricated SISL patch coupler at 6 GHz are well agreed. The measured insertion loss is only around 0.15 dB. From 5.5 GHz to 6.6 GHz, the measured phase imbalance is 90°±1° and the measured amplitude imbalance is smaller than 0.6 dB. The measured loss is much smaller than that of the previous designs.

This paper presents an air-filled substrate integrated waveguide (AFSIW) filter post-process tuning technique. The emerging high-performance AFSIW technology is of high interest for the de-sign of microwave substrate integrated systems based on low-cost multilayer printed circuit board process. However, to comply with stringent specifica-tions, especially for spatial, aeronautical and safety applica-tions, a filter post-process tuning technic is desired. AFSIW single pole filter post-process tuning using a capacitive post is theoretically analyzed. It is demonstrated that a tuning of more than 3% of the resonant frequency is achieved at 21 GHz using a 0.3 mm radius post with a 40% insertion ratio. For experi-mental demonstration, a fourth-order AFSIW bandpass filter operating in the 20.88 to 21.11 GHz band is designed. Due to fabrication tolerances, it is shown that its performances are not in line with expected results. Using capacitive post tuning, char-acteristics are improved and agree with optimized results.

In this paper, a K-band tunable cavity resonator filter is intro-duced. The tunable filter uses a dual TE211 mode cavity to reduce the size of the filter. To improve the tuning range of a pseudo-low pass filter that uses short irises, dummy iris is introduced. To enhance selectivity at band edge, additional cavity is introduced. A transmission zero generated by the additional cavity is con-trolled by only the cavity. To extend the rejection band, we use interaction between TE211 mode and adjacent modes. We fabri-cate and test the two-cavity, three-transmission zero tunable fil-ters to verify the design results.

This paper proposed a new scheme of switching high-Q waveguide iris bandpass filters into different bands without using bulky components. Instead of constructing the filter using only metal, our design presents an assemblage of individual waveguide resonant cavities and dielectric substrate laminates integrated with RF MEMS switches. As a demonstration of the concept, a two-pole filter with four switchable passbands centered from 12.4 GHz to 14.6 GHz (18% of tunable range) with equal bandwidth has been presented. An unloaded Q-factor better than 1700 has been achieved for each state. The switches, with three different dimensions, can be actuated by three different pull-in voltages. This allows biasing them, by a single bias signal, into various states where the characteristics of the inverters are reconfigured, resulting in shifts of the passband.

In this paper, a novel tunable filter with multiple tuning functions is proposed. The filter can be used as a 4th-order bandpass-to-bandstop reconfigurable filter for passband or stopband tuning, and also as a 2nd-order bandpass filter cascaded by a 2nd-order bandstop filter for passband tuning with controllable transmission zeroes. In each mode, both the frequency and bandwidth can be controlled within a wide range, demonstrating excellent tuning flexibility and capabilities. The filter topology is expected to find applications in modern wireless standards such as carrier aggregation and cognitive radios.

A new half-mode frequency-tunable SIW (substrate-integrated waveguide) bandpass filter with a constant absolute bandwidth is presented in this paper. For achieving the constant bandwidth, we have developed new external and internal coupling structures capable of exhibiting specified coupling values over the frequency tuning range of the presented filter. Hence, the presented filter employs no tuning components in the coupling structures and this avoids the insertion loss increase due to tuning components. For verification, a second-order filter has been designed, fabricated, and measured. The filter has the insertion loss smaller than 2.0 dB over the frequency tuning range from 1.85 GHz to 2.3 GHz. The bandwidth slightly varies from 136 MHz to 142 MHz.

This paper presents a high-Q tunable quasi-absorptive band-stop-to-all-pass filter in the 1.1 to 2 GHz frequency range. The filter can continuously tune from an all-pass response to an ab-sorptive bandstop response with high isolation (70 dB) across its entire frequency range. The insertion loss in its all-pass state var-ies from 2.27 to 3.14 dB. The filter topology requires only one tuning element per resonator. The filter topology is implemented with evanescent-mode cavity resonators and tuned with low-power piezoelectric actuators. The extracted unloaded resonator Q-factor is 400.

A novel differential coupling structure for tunable evanescent-mode cavity resonators is presented in this paper. The coupling structure is very simple and compact, and presents no design or fabrication challenges relative to a comparable single-ended coupling structure. This new coupling structure is used to realize a high-performance 3-pole tunable balun bandpass filter, which integrates the functionalities of a tunable bandpass filter and a balanced-to-unbalanced transformer (balun). The filter tunes from 3.2 to 6.1 GHz, and has a nominally 2.4% 3-dB fractional bandwidth. It demonstrates state-of-the-art measured amplitude and phase balance among tunable balun filters, with less than 0.2 dB and 0.9 degrees of in-band amplitude and phase imbalance across its entire tuning range.

This paper presents two Vanadium Oxide (VO2)-based RF switches – one series switch and one parallel switch. A copper-based fabrication process used for fabricating the switches is described in details. The VO2 films of the fabricated switches are characterized with X-ray diffraction and atomic force microscopy to ensure optimal film quality. Simulations results are presented for both switches up to 75 GHz. The measured results demon-strate an insertion loss of better than 0.4 dB and an isolation close to 30 dB up to 20 GHz.

Due to their extremely low static current consumption, varactors based on BST are perfect devices for realization of tunable and re-configurable components. This work presents fully screen-printed MIM thick-film BST varactors used to tune the load impedance of GaN HEMTs. The varactor tuning voltage is supplied in discrete steps using a high-speed GaN-based modu-lator. Modulated measurements with LTE and WCDMA signals show, for the first time, the functionality of a BST-based load modulation system and the power consumption of the load-modulation in dynamic operation. Using discrete dynamic load modulation, an average PAE of 27.3% was measured for the LTE signal with an ACLR below -45 dB.

Recent progress in device fabrication and characterization of GeTe-based phase-change RF switches has yielded switches with tens of thousands of switching cycles and μs-level switching times, bringing these switches one step closer to practical implementation into re-configurable MMICs and systems.

A novel half mode waveguide based ferrite isolator design is presented in this work. For the first time, tunability of the isolation band is demonstrated for a ferrite isolator. Instead of using the conventional antisymmetric bias isolator requires a single direction of magnetic bias field. YIG is used as the substrate for the device. The metallic walls of the waveguide are realized using inkjet printing. The magnetic biasing applied to the waveguide causes the RF waves to experience negative permeability in one direction of propagation hence providing isolation for this direction. For an applied bias of 3000 Oe, the device provides a maximum IFM of 76.7 dB at 7.5 GHz. The isolation band can be controlled by changing the applied magnetostatic bias. As the bias is varied from 1500 Oe to 3500 Oe the center frequency of the isolation band varies from 4.45 GHz to 9 GHz.

The dependence of on-state Germanium Telluride (GeTe) RF power handing as a function of device cycling is presented. The data is also compared to computer based models in order to determine a possible method of failure at high RF input powers. The device is thermally actuated by an embedded Tungsten heater and tested at 1.8GHz. The measurements are compared to a computer based model. The data shows the power handling improves as the device is continually cycled. The results suggest the devices fail due to limiting the current's cross sectional area causing current crowding and excess heat generation.

Intrinsically switchable thin film bulk acoustic resonator (FBAR) based on Ba0.5Sr0.5TiO3 is designed and fabricated for a high Qm×Kt2 at the fundamental resonance mode. High Qm×Kt2 BST FBARs can be used to design low insertion loss switchable BAW filters. Measurement results for a BST FBAR show a resonator mechanical quality factor (Qm) of 360 at the series resonance frequency of 2 GHz with a mechanical coupling coefficient (Kt2) of 8.6%. Qm×Kt2 is calculated to be 30.8, and to the best of authors’ knowledge, it is the highest value among the previously reported switchable BST resonators. The measured temperature coefficients of frequency (TCF) for the series and parallel resonance frequencies are -65 and -68 ppm/C, respectively. The negative TCF of the BST FBAR is partially compensated by addition of a SiO2 layer to the FBAR structure.

A general approach for in-line filters that contain a set of frequency-variant couplings is presented in this work. By utilizing an absolute matrix transformation process, the synthesis is distinctive from all other similar literatures because no optimization is required. In result, it is shown that multiple transmission zeros can be individually generated by the frequency-variant couplings. Moreover, some unique topologies where in-line frequency-variant couplings are connected with traditional extracted-pole sections and cross-coupled structures are introduced. For validation of the proposed approach, a group of examples with practical results are demonstrated.

This paper presents a novel dual-wideband bandpass filter comprising of composite series and shunt resonators and its direct synthesis and design theory. The composite series and shunt resonators can produce a transmission pole (TP) as well as a transmission zero (TZ) flexibly. A shunt capacitor at input/output (I/O) port is introduced to contribute an extra TP. A dual-wideband response with high skirt-selectivity can be achieved by appropriately arranging the TPs and TZs. To synthesize the lumped element prototype of filter, the filtering function is firstly obtained by iteratively solving a deterministic linear problem and the circuit model is found by a circuit extraction procedure. As an example, a dual-wideband bandpass filter with fractional bandwidths of 40% and 20% at center frequencies of 1 GHz and 2 GHz is directly synthesized, fabricated and measured. An expected characteristic is obtained.

The implicit space mapping technique is implemented as the optimization algorithm for the reflected group delay method in designing a 6-pole microstrip hairpin filter. A technique is proposed to reduce simulation points by matching a few selected group delay points. A computer-aided EM based design approach is proposed for the integration of the implicit space mapping technique and the reflected group delay method. The design steps are summarized and the filter is designed in Sonnet. By using the proposed method, the computation time and space mapping iterations are significantly reduced.

This paper addresses the application of stub-loaded planar circuits to the realization of dual-band bandpass filters and extended-upper-stopband broad-band bandpass filters with quasi-elliptic transfer function. To this aim, different classes of homogeneous- and stepped-impedance parallel-type open-ended stubs are exploited. Analytical design formulas for the transmission zeros (TZs) generated by these stubs are provided. Furthermore, for experimental-validation purposes, two multi-pole microstrip prototypes are manufactured and characterized.

In this paper, an ultra-wideband (UWB) Wilkinson power divider with ultra-narrow dual-notched bands is proposed. The multi-mode UWB characteristic is achieved using stepped-impedance open-circuited stub (SIOS) and broadside-coupled microstrip/CPW (BCMC) transition. Then, to cancel the interferences from existed wireless local-area network (WLAN) signals (i.e., 5.2 and 5.8 GHz), two pairs of embedded CPW resonators are employed. To verify the mechanisms mentioned above, a UWB power divider with dual-notched bands is implemented and fabricated. The measurement exhibits dual-notched bands with center frequencies of 5.28 and 5.86 GHz, which has merits of 10-dB notched FBW of 1.5% and 0.68%, respectively.

A 6-way planar ring for combining/dividing signals is presented. Conventional planar power combining/dividing structures use derivatives of the Wilkinson combiner in a ladder structure, or radial combiners. The ring combiner is smaller, provide higher port isolation, improved harmonic suppression and a single isolation port (e.g., delta output port), allowing energy harvesting in outphasing applications. The pre-sented ring combiner achieves a measured insertion loss of < 1dB from 5.5-5.8 GHz, while achieving > 25 dB isolation. The isolation notch is tunable by adjusting a static phase offset be-tween the inputs. When linearly combining six, 26 dBm amplifi-ers, measurement results show 31dBm output. A 5-MHz, 64QAM LTE uplink signal is amplified without DPD and achieves an average output power of 25 dBm with an ACLR of >35 dBc. The power handling capability of the ring is only lim-ited by the trace width and dielectric material, hence higher powers are achieveable.

A novel microstrip Wilkinson power divider with separate paths for the even and odd modes is presented in this paper. The proposed divider has a single quarter wavelength impedance transformer section and a reduced dimension in the transverse direction. This is achieved by etching a longitudinal slot in the ground plane of the microstrip where the isolation resistor is added. To develop a design procedure for the proposed divider, an equivalent circuit model for the slotted microstrip cross junction is also proposed. The model is validated by implementing a two-way band-pass filter. The proposed divider has a typical Wilkinson power divider performance of 0.2 dB insertion loss within 72% fractional bandwidth (15 dB return loss) and -24 dB isolation at the operating frequency. Meanwhile, it has the advantage of short lateral dimensions compared to its counterparts.Theoretical predictions have been verified by EM simulations and measurements.

In this paper, a design method of an ultra-wideband multi-section power divider on suspended stripline(SSL) is presented. A clear design guideline for ultra-wideband power dividers is provided. As a design example, a 10-section SSL power divider is implemented. The fabricated divider exhibits the minimum insertion loss of 0.3 dB and the maximum insertion loss of 1.5 dB from 1 to 19 GHz. The measured VSWR is typically 1.40:1, and the isolation between output-port is typically 20 dB.

This work reports copper/cobalt (Cu/Co) metaconductor based coplanar waveguide (CPW) transmission lines, featuring excellent signal integrity at K-bands and millimeter wave frequencies such as low conductor loss, reduced signal dispersion, and low noise figure. CPW transmission lines consisting of 10 pairs of Cu/Co thin film metaconductors with each layer thickness of 150 nm/25 nm, respectively, have been designed, fabricated and characterized. Experimental results show an RF resistance reduction of up to 50 % (Max.) in 7 GHz – 30 GHz, 25.5 % delay performance improvement, and 30 % thermal noise voltage reduction compared with reference copper based CPWs. Compared with devices from other literatures, the presented device shows the best signal integrity performance in Ku, Ku, and Ka bands.

New approach to enhance phase-shifting nonreciprocity of microstrip-line-based metamaterials with normally magnetized ferrite materials is proposed by using a combination of curvature of the line and asymmetric insertion of shunt inductive stubs. Numerical simulation and measurement results clearly show that the nonreciprocity for the case where the shunt inductive stubs are asymmetrically inserted to the inner side of the curved line was greater than that for another case where the shunt stubs are inserted to the outer side of the curved line. Decrease in radius of the curvature increases the geometrical asymmetry resulting in enhancement of the nonreciprocity.

A novel type of substrate integrated waveguide (SIW) tapers in a multilayer stackup is presented. A simple and fast synthesis method is developed. Where the taper is modeled as a nonuniform transmission line with varying waveguide characteristics. These are determined using an transverse resonance method (TRM), which is extended to calculate a characteristic impedance. The syntheses procedure is explained and the results are compared to full-wave simulation. Measurement results of a compact, ultra-wideband, and low-loss taper at K/Ka-band validate the concept.

Substrate integrated suspended line (SISL) and air-filled sub-strate integrated waveguide (AFSIW) technological platforms have been recently reported. They are both of high interest for the design of high-performance integrated millimeter-wave systems based on low-cost multilayer printed circuit board (PCB) technologies. This has been confirmed through simula-tions and experiments when comparing the insertion loss at Ka-band of the SISL and AFSIW with other conventional transmis-sion lines. To take advantage of both platforms and interconnect SISL and AFSIW structures and circuits, a broadband SISL to AFSIW transition is reported. For demonstration purpose, a back-to-back transition operating over the Ka-band has been designed and fabricated. It achieves a matching of better than -15 dB and an insertion loss of 0.27 ±0.22 dB (0.11 ±0.06 dB for the transition) over the Ka-band.

As applications in E-band (60 - 90 GHz) are gaining increasing commercial interest, a full-band, low-cost and high performance microstrip to rectangular waveguide standard (WR12) transition is desired. The presented design covers a bandwidth from 55 GHz to 95 GHz thanks to smooth impedance transitions. A dielectric tip is machined at the end of the microstrip line to couple with a double ridged waveguide section, which is then linearly tapered to a standard WR12 section. Measurements on back-to-back transitions confirm wideband operation beyond E-band with a 3.6 dB insertion loss (1.8 dB per transition) and return loss lower than 10 dB (18 dB per transition) in the 55 to 95 GHz frequency range. Additionally, group delay is measured showing broadband operation in line with simulation.

Hybrid integration often requires to connecting components with different connector footprints, typical examples being MMICs and larger drop-in devices. In microstrip technology this calls for different line widths and substrate thicknesses. This paper proposes a novel transition between two microstrip lines of different width and height. The basic concept of the multilayer approach is to gradually adapt the field distribution along the transition while keeping the impedance constant. In simulation the optimized transition exhibits an impedance match in excess of 20 dB from DC to 20 GHz. For verification a back-to-back transition is fabricated and measured. It features more than 20 dB input match and an insertion loss below 0.74 dB in a bandwidth of 16.9 GHz, the results being in good agreement with simulation.

In this paper, we intend to design of a wide band dual-band filter with dispersive couplings for improved selectivity. The proposed approach consists to use this novel filter synthesis technique, taking advantage of the frequency variation of coupling values, for generating additional transmission zeroes. The dispersive coupling behavior is demonstrated and em-ployed to design a four pole filter with three transmission ze-ros. The design is validated by a prototype and a six-pole dual-band bandpass filter based on the same concept is pro-posed for 5G millimeter-wave bands.

This paper presents a new broadband external coupling structure for tunable evanescent-mode cavity resonator-based bandstop filters. This coupling method has low parasitics, which when combined with the wide spurious-free range of evansecent-mode cavities enables the implementation of a 3 to 6 GHz tunable bandstop filter which has a measured low-loss upper passband with less than 3-dB of insertion loss up to 28.5 GHz.

The paper presents a novel approach for realizing a compact filtering structure composed of single-mode low-loss rectangular waveguide cavities able to implement high-selectivity transfer functions of elliptic type. The creation of transmission zeros is obtained by disposing the cavities in a suitable geometrical configuration and exploiting the properties of the selected resonant mode (TE102). The proposed approach is employed in the design of a four-pole elliptic filter at Ka-band. This is the basic building block for the extension to a 6-pole filter with 2 transmission zeros that can be used in low-loss high-power and high-selectivity diplexers required by modern multibeam payload of last generation satellites operating at Ka-band and above

This paper introduces a new design methododology for multiband waveguide filters based on a manifold approach. The new design algorithm is based on a subtle modification of the well-known multiplexer design algorithm. Transmission zeros, enhancing the overall performance, are also shown to be naturally produced. In addition to theory, the measured performance of a multiband filter is shown indicating very good agreement with the simulated response thereby fully validating the new design methodology.

This paper presents a novel triple-band bandpass filter employing dielectric loaded resonators that support three operating modes. The proposed design employs dielectric resonators shaped in a way to have independent control of the resonant frequencies of the three modes and to facilitate inter-resonator coupling. The proposed triple-band dielectric filter offers high Q and is miniature in size in comparison to previously reported multi-band filter designs. A 3rd order C-band triple-band dielectric filter is designed, manufactured, and tested to validate the proposed concept. To the best of authors’ knowledge, this is the first triple-band filter realized with dielectric resonators.

This paper presents a detailed approach to the design and dimensioning of coaxial filters with fully canonic elliptic response. In order get a compact configuration the extracted-pole in-line configuration with non-resonating nodes (NRN) is adopted. First the synthesis of a low-pass prototype is carried out and the generalized coupling coefficients together with the resonant frequencies are computed as outlined in the literature. A suitable de-normalized equivalent circuit is then derived with reference to the specific filter configuration here considered. Finally, the dimensioning of the structure is carried out suitably exploiting full wave simulations for imposing the parameters of the equivalent circuit obtained from the synthesis to the physical structure. The proposed methodology has been validated by the design and fabrication of two high selectivity filters to connect in cascade for realizing a band pass filter easily tunable both in center frequency and bandwidth

This paper proposes a varactor-based reflection-type phase shifter that allows for 360-degree relative phase-shift range and reduced insertion-loss variation over the entire frequency tuning range. In particular, a novel and compact reconfigurable 90-degree coupler is devised and it is, theoretically, able to achieve perfect return loss and isolation at each tuning state. Thus, when this 3-dB coupler is terminated with two reflective loads, the phase shifter can operate at a wide range of center frequencies. Moreover, a tunable transformation network is proposed to optimally reduce the insertion-loss variation within the 360-degree continuous phase-shift range for any operational frequency. Experimental results show that the fabricated phase shifter, in a frequency range of 1.5-2.5 GHz, can realize 360-degree relative phase-shift range with greater than 16.5 dB in return loss and less than 3.8 dB in insertion-loss variation.

In this paper, we suggest the use of a cold plasma as tunable material inside a microstrip resonant cavity. Plasma dielectric constant can indeed be moved to values below $1$ to tune its resonant frequency. DC plasma analysis were conducted and integrated into classic electromagnetic solvers to investigate tuning abilities. Numerical simulations are consistent with experimental results and make this original tuning techniques viable for high power applications.

Tunable matching networks are important for agile RF circuits. To optimally design such networks the overall coverage needs to be determined. In this work, analytical formulas for the coverage area within the Smith chart of a three-element tunable-network are derived. It has been found that up to sixteen circles bound the coverage area. Analytical expressions for the centers and radii of these circles have been derived and verified by circuit simulation as well as measured data. The formulas in this work can be readily integrated into CAD tools, thus provide a valuable tool for the design of tunable circuits. The analyzed network favors the first and fourth quarters while the other quarters can be targeted with the dual of this network.

One method used for designing RF and microwave impedance matching networks is based on tapered lines. This paper shows a simple method to design smooth tapers that take into account the dispersion of the line and the required design bandwidth simultaneously. The taper is designed through optimization of very few parameters. As a result, the reflection coefficient of the taper can be optimally adapted to a given specific mask using the prescribed value of physical length. Experimental results are included for validation of the proposed design method.

This paper presents a millimeter-wave variable attenuator using vanadium dioxide (VO2)-based variable resistors. The thin films VO2 are integrated monolithically with a 0-dB coupler to realize the variable attenuator. A 30 GHz variable attenuator is designed, fabricated, and tested to verify the concept. It exhibits a continu-ous maximum attenuation tuning range of 13 dB, and a return loss of 15 dB over a bandwidth of 5 GHz. The proposed VO2 based variable attenuators have a great potential to be used in a wide range of millimeter-wave applications.

A transfer-function-adaptive quasi-elliptic-type microwave bandpass filter is presented. The devised fully-reconfigurable filter is based on a resonator-cascade structure with static impedance inverters and only exploits the tuning of its resonating nodes to achieve all its reconfiguration properties. They include center-frequency, bandwidth, and transmission-zero (TZ) control for bandpass-type responses, as well as the intrinsic switching-off (i.e., without RF switches) of the filter. Moreover, it features less in-band insertion-loss levels and improved linearity behavior (specially for narrow-band states) when compared to more-classic bandwidth-tunable filters that use inter-resonator coupling variation. The operational foundations of the engineered fully-reconfigurable filter architecture are theoretically expounded in a coupling-matrix framework. Besides, a tunable three-pole microstrip filter prototype in the range 1.2-1.7 GHz is developed and tested for experimental-demonstration purposes.

In this paper, a prototype of reconfigurable dualband bandpass filter is proposed. It features independently frequency-controllable quasi-elliptic-type passbands with stopband transmission zeros that can be intrinsically switched on/off. Tunable dual-resonance (i.e., f1 and f2) is introduced in this filter by the half-wavelength (λ/2) folded-resonator with series varactor-loaded open-stub. To verify the operational mechanism above, a tunable dual-band bandpass filter with added passband-switching capability is fabricated and measured. It exhibits frequency-tuning ranges of 38.2% and 33.1% for the dual-band, respectively.

In this paper, design of a tunable dual-mode dual-band microstrip bandpass filter is presented. The designed filter is constructed by using two nested dual-mode resonators (DMRs) having two patch capacitances located at the lateral arms of the resonators as reference elements. Varactor diodes are used in-stead of perturbation elements in order to excite the degenerate modes. Linear phase and quasi elliptical filtering characteristics can be independently obtained in each passband and the band-widths can also be tuned at both filtering characteristics. For the experimental verification of the designed structure, a dual-mode dual-band microstrip bandpass filter was fabricated and meas-ured. Center frequencies of the passbands were adjusted to 1.78 - 2.65 GHz and 1.83-2.7 GHz for linear phase and quasi elliptical filtering characteristics, respectively. Insertion losses in each passband were observed as better than 3 dB in measurements.

This paper presents a novel reconfigurable dual-band bandstop filter with independently controlled stopbands and constant absolute bandwidths (ABWs). The fundamental structure is based on λ/4 varactor-loaded resonators, and the key to constant ABW is choosing proper coupling regions between resonators. Theoretical analysis and calculation are carried out to determine physical parameters of the coupling regions. For demonstration, a second-order dual-band bandstop filter is implemented with 23.6% fractional tuning range of the first stopband from 1.27 to 1.57 GHz and 18.1% of the second stopband from 1.98 to 2.34 GHz, and 3-dB ABWs are 60 ± 3 MHz and 103 ± 5 MHz, respectively.

A balanced two-pole dual-band filter with reconfigurable center frequencies is constructed in this letter for the first time. By incorporating varactor diodes into the doubly short-ended resonator loaded with two short-ended stubs, flexible tuning capabilities are thus enabled. According to stub-loaded theory, by properly selecting positions of two short-ended stubs on the doubly short-ended resonator, the first differential-mode passband center frequency could be independently manipulated, without affecting the other passband. Besides, source-load coupling is introduced to improve the differential-mode frequency selectivity by creating two finite transmission zeros close to each passband. For validation, a tunable balanced dual-band filter is implemented and good agreement between simulation and measurement results indicates the feasibility of proposed design methodology.

This paper presents a varactor-tuned diplexer with four reconfigurable channel frequencies. To reduce size and enable flexible control of the two passbands at the same output, novel dual-mode resonators are proposed where the even- and odd-mode resonances are, respectively, applied to the higher and lower passbands and can be easily excited at different resonator locations. Moreover, the distributed coupling feed lines are used to generate transmission zeros in the passbands of the other output, leading to high isolation. Experimental results show that the four channels of the fabricated diplexer can be tuned from 1.2 to 1.47 GHz, 1.56 to 1.9 GHz, 2 to 2.45 GHz, and 2.55 to 3.16 GHz with constant absolute bandwidth, greater than 14.4 dB in return loss, and greater than 30 dB in isolation. The diplexer occupies a compact footprint of 0.13 lambda_0 × 0.17 lambda_0, where lambda_0 is the free-space wavelength at 1.2 GHz.

In this work, a mode composite waveguide (MCW) based dual-mode filter is proposed and studied. This filter uses the inner waveguide of MCW as the input and output feedings, and the outer waveguide of MCW as the dual-mode resonator. The two degenerate modes in the outer waveguide resonator are used for the dual-mode filter operation, which generates two transmission poles and one finite transmission zero. The two transmission poles are used to control the filter bandwidth, and the finite transmission zero is used to improve the out of band selectivity. The generated finite transmission zero can be placed at either the left or right vicinity of the passband by adjusting the feeding parameters. Two types of dual-mode filter are designed at 10 GHz with 2% fractional bandwidth. Type I filter exhibits a transmission zero at the left vicinity of the passband while type II filter exhibits one at the right.

A novel dual-band bandpass filter based on the multimodes in a single perturbed substrate integrated waveguide (SIW) cavity is proposed. Metallized via-holes are introduced to serve as perturbations to shift and control the first four resonant modes and divide them into two groups. The perturbed TE101 and TE102 modes lead to the first passband while the perturbed TE201 and TE202 modes constitute the second passband. Furthermore, by moving the via-holes along the diagonal line of the SIW cavity, the first passband can be tuned independently while the second passband is fixed. A prototype filter operating at 9.22 GHz and 11.30 GHz is designed and fabricated. Measured and simulated results are presented to validate the proposed design concept of the dual-band filter.

A kind of substrate integrated waveguide (SIW) dual-band bandpass filters (DB-BPF) with flexibly allocated center frequencies (CFs) and fractional bandwidths (FBWs) is presented based on TE101 and TE201 modes in SIW rectangular cavities. Emphasis is placed on filters design to simultaneously realize the external quality factors Qe and coupling coefficients Mij required for both passbands by determining proper offset positions and coupling structural dimensions of the feeding ports and coupling windows, respectively. Consequently, both the CFs and FBWs of the two passbands can be specified and allocated freely over wide ranges.

This paper presents an ultra-wide stopband selfpackaged quasi-lumped-element low pass filter (LPF) based on substrate integrated suspended line (SISL) technology. Interdigital capacitor and spiral inductor are utilized in the 1GHz quasilumped-element LPF. The measured results shows that the proposed LPF can achieve a wide stopband from 1.36 fc to 24 fc with 20dB stopband rejection. And the filter has advantages of self-packaging, low loss, compact size, and low cost by using SISL Technology.

In this paper, a joint feeding network within a triple layer topology is described and studied for mode composite waveguide (MCW). MCW consists of inner and outer dual waveguides, and this feeding network can independently excite the outer waveguide from the top and bottom layers, and the inner waveguide from the middle layer. The outer waveguide feeding structure consists of a multilayer power divider in series with a dual taper structure while the inner waveguide feeding structure consists of a right angle bend in series with a taper. This joint feeding scheme completely isolates the inner and outer waveguide feeding structures from each other, thus allowing an independent design and optimization of each feeding structure. The prototyped feeding network experimentally exhibits good matching within its operation bands from 6.9 to 11.8 GHz for the outer waveguide, and from 13.5 to 24.1 GHz for the inner waveguide.

Characterization of a wide-band transformer balun with low amplitude and phase imbalance is presented in this paper. Excellent balance over a large bandwidth is achieved by adopting two new techniques for the transformer balun design, resulting in a very low amplitude imbalance of 0.12 dB and phase imbalance of less than 1deg over 30 to 60 GHz. The tradeoff between the insertion loss and the balance of the balun is investigated. First, the appropriate width of the primary and the secondary coils is selected for a reasonable insertion loss. Secondly, the radii of the primary and secondary coils were offset to reduce the parasitic coupling capacitance, thereby improving the balance of the differential signal. The balun is fabricated in 0.13 um SiGe technology. The balun is very compact with chip size of 0.2 mm x 0.145 mm.

This paper presents a 60-GHz six-pole quasi-elliptic bandpass filter (BPF) realized in silica-based post-wall waveguide (PWW). We also propose a novel feeding mechanism that can control external quality factor. The mechanism has several parameters for the control. The BPF with a 8.1% fractional bandwidth and a 1.1-dB insertion loss at 60 GHz is presented. The dimension of the BPF is 3.6mm by 5.4mm.

A novel lumped design approach for complex impedance transforming baluns is presented in this paper. It is shown that a relaxation of symmetry in the T-networks of the out-of-phase-compensated-power-splitter enables complex impedance transformation. Design equations are analytically derived for a total of 4 component values, of which 2 values depend upon the 2 other, which are free variables. The two free component values are used independently for adjustment of input reflection loss, further keeping the balance parameter maximally flat and independent of the load impedance. For Q-values of source and load, not being excessively high, the balun can be realized with only 8 components. A demonstrator is fabricated, transforming 26.9+j11.1 Ohm to 73.8+j38.6 Ohm. An amplitude balance of +/-0.7 dB and phase balance better than +/-5 deg is achieved over a 20 % bandwidth. The return loss is higher than 20 dB.

This paper presents a dual-band −90 degree/+90 degree transmission line for the miniaturization of dual-band rat-race couplers. This line was constructed using two diagonally end-shorted coupled-line sections tapped by open stubs at their center. The proposed structure has the advantages of −90 degree/+90 degree electrical lengths at two arbitrary frequencies and high equivalent characteristic impedances, enabling the creation of small couplers that have a large power-split ratio of up to 1:32. Using the proposed structure, a rat-race coupler operated at 2.4/5.1 GHz with a power-split ratio of 1:4 was fabricated for demonstration. This circuit occupies only 44% of the area of existing dual-band rat-race couplers.

This paper presents, for the first time, a new tuning technology based on bi-directional MEMS actuators for high-quality all-silicon evanescent mode cavity filters. Such bi-directional tuna-bility provides a feasible solution to restore frequency tunability from degradation caused by aging effects such as creep and stress relaxation. The fabricated proof-of-concept filter demon-strates a measured tuning range from 18.9 to 39.6 GHz, in which the forward (main) actuation tunes from 21.3 to 39.6 GHz with 120 V and the reverse (corrective) actuation tunes from 21.3 down to 18.9 GHz with 2 V. The measured filter insertion loss varies from 3.14 to 0.78 dB and its instantaneous bandwidth from 0.31 to 1.81 GHz. The unloaded quality factor is extracted as 265-510 which is comparable to the state-of-the-art filter of this type employing conventional uni-directional tuners.

This paper introduces a new fabrication process for the realization of cavity resonators and band pass filters, using additive micro fabrication. 3D air-filled structures with a 200 µm thickness are obtained by using successive electroplating. Thanks to this fabrication process, a 140 GHz cavity resonator with an unloaded quality factor of 512 has been fabricated. A Four-pole band pass filter at 140 GHz, with a 3.1% bandwidth at -3 dB, and measured 3.7 dB in-band loss. Measurements are in good agreement with HFSS simulations without any post-processing tuning.

This paper presents a novel approach to tunable delay lines to address the demand for high resolution tunable delay lines for full duplex transceivers. The proposed design is capable to utilize minimum number of switches to achieve a group delay resolution of 33 picoseconds. Simulation and meas-urements are in close agreement and their negligible discrepancies are justified. The proposed design has wide applications in ana-log RF interference cancelation, analog signal processing (ASP), and antenna beamforming.

Reference oscillators are crucial hardware components of radio-frequency receivers as their performance directly affects the system performance. In GHz applications, e.g., 4G/5G, a low error-vector magnitude is required, which is strongly affected by the phase noise of the reference oscillator. This paper reports the design, simulation, and measurement of a MEMS oscillator with very low phase noise, which is suitable for use as reference oscillator in RF receivers. While the MEMS device is a plate-shaped contour-mode resonator in an aluminium-nitride-on-silicon technology, the active part of the oscillator is implemented in 180nm CMOS. By adding the parasitic effects of the assembly, gained from measurements of the submodules, the simulation and measurement results show good agreement: 3dB deviation in the noise floor of -142dBc/Hz. The phase-noise level of the oscillator at an offset of 1kHz from the operating frequency of 256MHz is -112dBc/Hz, among the lowest values reported for MEMS-based RF oscillators.

This paper presents the first radio frequency (RF) voltage controlled MEMS oscillator (VCMO) using a high Q Lithium Niobate (LiNbO3) micromechanical resonator. The resonator has a quality factor of 650 in air with a motional impedance of 262 Ω. The oscillator’s measured phase noise is -84.4 dBc/Hz and -146 dBc/Hz at 1 kHz and 1 MHz offsets respectively from a 149.13 MHz carrier with an output power of -8.6 dBm. The oscillator consumes less than 1 mA with a tuning range of 0.42 MHz. Such VCOs are envisioned for low power, and low phase noise RF signal synthesis for Internet of Things applications.

In this paper, a waveguide bandpass filter applied to the terahertz frequency band is developed by using a high precision silicon-based Micro Electromechanical System (MEMS) fabrication process. The 420 GHz Iris Inductive Window Coupled Wave-guide Filter uses a circular resonator structure, solves the processing problem of the critical dimension of this type of filter. The measured results show that the insertion loss of the 420 GHz waveguide filter is 1.9 dB with the bandwidth 22 GHz.This circular resonant structure reduces the process requirements and improves the tolerance. The 420 GHz waveguide filter is simple and reliable, and can be applied to various terahertz circuits.

We present a microfabricated sub-THz WR-3.4 bandpass filter using dual-mode circular cavity resonators. The filter operates at the center frequency of 270 GHz with fractional bandwidth of 1.85%; transmission zeros are introduced in the upper and lower stopband using a negative coupling. The microchip filter is significantly more compact than any previous designs at comparable frequencies, occupying less than 1.5 mm2. In contrast to any previous micromachined filter work, due to its axially arranged interfaces it can be directly inserted between two standard WR-3.4 rectangular-waveguide flanges, which vastly improves system integration as compared to previous micromachined filters; in particular no custom-made split-block design is required. The measured average return loss in the passband is –18 dB and worst-case return loss is –15 dB; an insertion loss of only 1.5 dB was measured. xcellent agreement between measured and simulated data is facilitated by fabrication accuracy, design robustness and micromachined self-alignment geometries.

This paper presents a compact 55-65 GHz single-ended-to-balanced bandpass filter in CMOS technology. The balanced bandpass filters is designed based on three coupled-line stepped-impedance microstrip line to obtain differential output phases and incorporated with the grounded pedestal stepped-impedance microstrip line to minimize the circuit size. For in-band rejection, it using the stepped-impedance open stub to generation high passband transmission zero. The measured insertion loss is less than 4.7 dB and the return loss is larger than 9 dB in 55-65 GHz. The power imbalance is less than 0.7 dB and the phase imbalance is less than 2˚. The chip size without pad is 0.293×0.136 mm2.

Two millimetre-wave filters (a Chebyshev 4-pole and a quasi-elliptical 6-pole 2 zeroes) centred at 39 GHz are presented in this paper. They are both obtained by laser machining Alumina substrates and metallized with an electroless Copper plating technique. Laser etching is finally used again to etch the different patterns required for their input and output as well as other features. Despite the simplicity of this method, good agreements are obtained between full wave simulations and measurements, validating the proposed approach.

On-chip mm-wave dielectric resonator filters are presented. Low-loss alumina ceramic spheres resonating in a non-radiative mode are used as dielectric resonators. Accurate placement of the resonator spheres is ensured by precise etching of shallow crates in the back-end-of-line low-permittivity dielectric layers atop the semiconductor chip. The spheres are placed in and aligned by these crates. The multi-sphere filter is fed by on-chip microstrip lines. Coupling between microstrip line and sphere can be enhanced by quarter-wave on-chip microstrip resonators. A metallic plate atop the spheres and parallel to the chip holds the spheres in position and prevents radiation. Filters are fabricated on a standard silicon wafer with two metal layers on top, separated by BCB dielectric. Measurements of 3-pole filters at 65 GHz and 95 GHz show an insertion loss of 1.4 dB and 1.2 dB, for an impedance bandwidth of 3.5% and 3.9%, respectively.

A rectangular waveguide band-pass filter with very low sensi-tivity to fabrication tolerances is proposed. The novel filter exploits the inherent first passband replica of commensurate-line stepped-impedance low-pass filters. Waveguide width reduc-tion is also exploited to obtain a band-pass filter with a signifi-cant enhancement in the fabrication yield. This improvement is especially attractive for space applications in the millimeter-wave range. The validity of the novel design technique has been demonstrated with a 13th-order Chebyshev band-pass filter for Q-band payloads. The manufacturing yield of the novel filter has been dramatically improved when compared to the classical inductive-iris filter designed to fulfill the same frequency specifi-cations (92 % vs. 8 %, for a worst-case fabrication error of ± 25 µm). A prototype has been fabricated using milling tech-niques showing a very good agreement between simulated and measured results.

Massive MIMO technology and mm-wave band are effective solution of a high data rate for 5G. This paper presents a novel 28GHz wideband filter for that antenna unit. To realize 10% fractional bandwidth, a new terminal configuration of V-shape structure is proposed. TEM-TE mode transition function using the new structure was analyzed, and the shape was optimized. Applying the new terminal structure to an 8-pole with 2 trap quartz waveguide filter, high performances such as very low loss of 1.2 dB, wide relative passband of 10.4% and high attenuation of more than 50dB were obtained with small size and SMD structure.

This papers reports on the design of a new class of acoustic-wave-resonator-(AWR)-based bandpass filters (BPFs). Unlike conventional ladder- and lattice-type AWR architectures, it allows the realization of passbands with constant group delay (τg) and larger bandwidth (BW). The devised configuration makes use of N identical hybrid acoustic-wave lumped-element resonators (AWLRs)─each of them contributing to one pole and two transmission zeros (TZs)─and N+1 lumped-element imped-ance inverters. As an added benefit, it exhibits power transmis-sion response whose maximum realizable BW and τg flatness does not depend on the electromechanical coupling coefficient (kt2) of its constituent AWRs. For experimental-demonstration purposes, a UHF-band three-pole/six-TZ BPF prototype with in-band linear phase was designed, manufactured, and measured using commercially-available surface-acoustic-wave (SAW) resonators. Its measured characteristics are summarized as: BW of 0.3 MHz, insertion- and return-loss of 2.1 dB and 32 dB, respectively, effective quality factor Qeff of 9,000, and in-band τg between 1.78 ± 0.02 μs.

Bulk acoustic wave (BAW) filters operating at center frequency of 3.7GHz, utilizing single crystal aluminum nitride (AlN) piezoelectric films grown on silicon carbide (SiC) substrates are reported. Metalorganic chemical vapor deposition (MOCVD) growth was used to obtain single crystal AlN films on 150-mm diameter SiC substrates with X-ray diffraction (XRD) rocking curve full-width half-maximum (FWHM) of 0.025. Filters had a center frequency of 3.7GHz and 3dB bandwidth of 100MHz, and insertion loss of 2.0dB and narrow band rejection of 40dB and out-of-band rejection in excess of 37dB to 8GHz. Individual resonators show an electro-mechanical coupling as high as 7.63% and maximum Q-factor up to 1572 and survive high power 10W survival test. This is first demonstration of single crystal AlN-on-SiC based BAW technology at 3.7GHz and illustrates the potential for compact, high power and high performance filter solutions for high frequency mobile, Wi-Fi and infrastructure applications.

A Low insertion loss (IL) intrinsically switchable bulk acoustic wave (BAW) filter based on the barium strontium titanate (Ba0.5Sr0.5TiO3) thin film bulk acoustic resonators (FBARs) is presented. A 1.5 stage ?-network ladder type switchable BST filter is designed and fabricated. The measured IL of the filter is 2.25 dB at 2.08 GHz center frequency. The 3 dB bandwidth of the filter is 58 MHz, and the minimum rejection level is 12 dB. The filter provides more than 15 dB of isolation between the input and the output ports, in its OFF state. The switchable BST filter presented in this paper provides the lowest IL as compared to the previously reported BST filters.

Modern high-performance SAW filters utilize thin-film technolo-gy to optimize losses, temperate stability, filter bandwidth, and manufacturing sensitivity. Fast design of these complicated struc-tures calls for accurate and more general simulation tools. The versatility of the finite element method (FEM) makes it attractive for this purpose. However, the application of FEM in the SAW field has been hampered by the associated very large memory requirements and excessive computation times. Here, we describe frequency-domain FEM simulation of SAW devices with the hierarchical cascading algorithm, including thermal effects. The method utilizes the periodic block structure, which is typical to SAW devices, to eliminate redundant calculations from FEM. The approach has all the advantages of FEM, with—for structures with high degree of periodicity—drastically reduced memory consumption and computation time.

An innovative high-power mismatch measurement is performed to validate the operation of a high-performance band 41 Film Bulk Acoustic Wave Resonator (FBAR) filter. The results demonstrate the operation of an FBAR filter at +33dBm input power and 10:1 VSWR mismatch, thereby successfully fulfilling the power requirements of the LTE High-Power User Equipment (HPUE) standard, while simultaneously testing all worst-case scenario mismatch conditions that might be presented by the antenna.

This paper describes a novel workflow for the electromagnetic (EM) simulation of radio frequency (RF) filters and modules for 4G mobile applications. Its main advantage is the automatic creation of complex EM simulation models, including simulation settings, allowing for shorter design cycles. EM phenomena affect nearly every single aspect of the device performance, and can affect parameters isolation and cross-isolation, crucial for carrier aggregation. The simulation workflow and the achieved accuracy are illustrated by means of an example, a module for 4G LTE-Advanced CA. The good agreement between simulation and measurement is shown for isolation and cross-isolation, demonstrating that all relevant EM effects contributing to the stop band performance were accurately captured by the EM model. The progress done will allow the reduction of design cycles for RF modules, liberating the designer from tedious tasks, implementing the best practices for EM simulation and drastically reducing potential errors.

This paper present for the first time all RF domain notch-feedback based 4th-order LC band-pass filter (BPF) system in 0.13 μm SiGe BiCMOS. The feedback BPF system achieves less than 1% fractional BW with 160-165 dB∙Hz normalized dynamic range (DR) at 2-4 GHz, breaking the inherent tradeoff between selectivity and DR in the Q-enhanced LC filters. With open-loop staggered tuning by disabling the feedback loop, BW is increased to 600 MHz with less than 200 ps group delay variation. The ultimate out-of-band rejection of the filter is > 65 dB and > 52 dB on the lower and upper side of the center frequency, respectively. The filter consumes 50-60 mW of DC power from 2.5 V supply voltage. The core chip size is 0.9×0.7 mm^2.

This paper presents a tunable active bandpass filter with bandwidth-adjustable notches close to the passband for wideband blocker suppression with high attenuation. The proposed filter is composed of a 3-pole N-path bandstop filter in cascade with an N-path bandpass filter, where the center frequency of the bandpass filter is offset from the bandstop filters. With proper tuning of the coupling capacitors in the bandstop filter, three adjacent notches can be created which provides a larger suppression bandwidth. An implementation of the filter in 65-nm CMOS exhibits a passband tunable between 0.1–1.1 GHz, with a 3-dB bandwidth of 12.4–14.2 MHz, a gain of 9.5–10.3 dB, a noise figure of 4.3–5.8 dB, and a total power consumption of 40–64.3mW. The blocker 1-dB compression point is 6.5 dBm and the out-of-band IIP3 is 18.4 dBm. The reported filter provides a promising solution to multi-standard, multi-frequency software defined radio applications.

A tunable 700- to 3000-MHz reflective-type N-path filter in 45-nm SOI CMOS is presented. The filter employs a reflective architecture in which two eight-phase passive mixers are combined with an external hybrid 90-degree coupler to realize a circuit that passes in-band signals and absorbs out-of-band signals. The filter achieves insertion loss 0.8 to 2.1~dB and noise figure of 0.9 to 3.9~dB over the entire tuning range, while consuming 4 to 8~mW from a 0.9-V supply. Input 1-dB compression point is +0~dBm; IIP3 is +10~dBm in-band and +22~dBm out-of-band.

An original silicon-integrated dual-band bandpass filter for GNSS bands is presented. The engineered filtering architecture consists of a two-path signal-interference transversal filtering section made up of a quadrature power coupler that is arranged in reflection mode. It allows a sharp-rejection dual-passband filtering response with out-of-band transmission zeros. Furthermore, to counteract the losses inherent to the integrated lumped-element realization, compensated active inductors are used. For experimental validation, a LNA+filter module based on the conceived approach is designed with 0.25μm BiCMOS process, fabricated, and tested. This circuit, which operates on the two spectral bands utilized by the GNSS system (1215–1300MHz and 1559–1610MHz), features measured in-band power gain and noise figure respectively equal to 14dB and 2dB with a 18mW power consumption. To the best of authors’ knowledge, it is believed to represent the first practical realization of a pure signal-interference dual-passband filter in integrated technology

Band 28 has wide bandwidth of 45MHz and narrow duplex gap of 10MHz in 700MHz band, and since digital terrestrial TV channels in some countries are overlapped with lower frequency range of the uplink band, two types of duplexer which have slightly shifted pass-bands need to be used. This paper describes a novel switchable SAW duplexer which can cover both bands in one duplexer. By using a filter design technique with unique switching circuit, and wideband and low temperature drift SAW resonator technology, high performance such as 2.6/3.0dB insertion loss and 55dB isolation could be achieved, in addition to more than 13/16dB near point attenuation only 5/8MHz apart from pass-band edge. The developed switchable duplexer can lead the reduction of 40% in mounting area on RF front-end circuit of mobile terminals.

In this paper, a controllable dual-band ban pass filter (DBBPF) for WLAN Applications is proposed based on the substrate integrated suspended line (SISL) technology. The proposed filter is firstly characterized by the feed lines on G5 which not only could excite the pass band formed by the circuits of the G6, but also could form a passband of the higher frequency band. And the second characteristic is that the bandwidth and the transmission zeros (TZs) are controllable by adjusting some parameters. The fractional bandwidth of the fabricated DBBPF are 39.74%/21.57% for two operation pass bands at 2.4/5.2 GHz. And the measured results are in good agreement with electromagnetic simulation.

In this paper, we proposed a compact quad-band bandpass filter (BPF) using multilayer substrate technique. The filter is de-signed to have quad-band at 1.8, 2.4, 3.5 and 4.2 GHz. The four passbands are simultaneously generated by controlling the im-pedance and length ratios of the stub-loaded stepped impedance resonators (SIRs). By using the stub-loaded SIRs, the filter with closed passbands can be easily achieved. The frequency re-sponse of wide stopband is generated by using the defected ground structure (DGS) and having around -30 dB stopband from 4.2 to 12 GHz. The filter can provide the multi-path prop-agation to enhance the frequency response and achieving the compact circuit size. The measured results are in favorable agreement with the full-wave electromagnetic (EM) simulation results.

Design of the fourth order microstrip filter with high selectivity is presented in this paper. Proposed microstrip filter circuit is carried out using the microstrip open loop resonators with a novel loading element consisting of interdigital unit cells. Dual mode is obtained by an open loop resonator with this type-loading element. Thus, the number of resonator is reduced and miniature and compact circuit is designed to be used in proposed structure. The interdigital loading element allows changing the frequency of the even mode and transmission zero, sensitive-ly. Also, the transmission zero is arbitrarily placed using this type loading element on both side of the passband without change in the surface area of loading element. Multi-mode filter is achieved by coupling of the open loop resonators with interdigital loading element. The proposed circuit has been fabricated to validate. The simulated and measured results are compared and they have shown good agreement.

A tri-band balanced bandpass filter (BPF) is presented based on novel multi-stub resonators, which are modified from the conventional multi-mode resonator. From the theoretical analysis, the first three resonance modes can be flexibly controlled under differential-mode (DM) operation. The extra stub-stub couplings are introduced to increase the degrees of freedom in extracting the coupling coefficients, helping to obtain controllable bandwidths. Different elements are loaded in the middle of the resonator to enhance the common-mode (CM) suppression across the given frequency range. To validate the design concept, a tri-band balanced BPF with controllable bandwidths and high CM suppression is designed, fabricated and measured. The measured result is in good agreement with the simulated result.