In this paper, synthesis and design techniques of dual- and triple-passband filters with Chebyshev and quasi-elliptic symmetric frequency responses are proposed and demonstrated for the first time on the basis of substrate integrated waveguide technology. The inverter coupled resonator section is first investigated, and then a dual-passband Chebyshev filter, a triple-passband Chebyshev filter, and a dual-passband quasi-elliptic filter, which consist of the inverter coupled resonator sections, are synthesized from the generalized low-pass prototypes having Chebyshev or quasi-elliptic responses, respectively. Subsequently, theses filters with a symmetric response are designed and implemented using the substrate integrated waveguide scheme over the -band frequency range. The inverter coupled resonator sections composed of side-by-side horizontally oriented substrate integrated waveguide cavities are coupled, in turn, by post-wall irises. 50-Omega microstrip lines are used to directly excite the filters. Measured results are presented and compared to those simulated by Ansoft's High Frequency Structure Simulator (HFSS) software package. A good agreement between the simulated and measured results is observed, which has also validated the proposed concept of design and synthesis with the substrate integration technology.

Dual-Band and Triple-Band Substrate Integrated Waveguide Filters With Chebyshev and Quasi-Elliptic Responses

The concept of the conventional coupling matrix is extended to include designs of dual- and triple-band filters. The multiband response is created by either placing transmission zeros within the bandwidth of a wideband filter or using higher order resonances. Realizable topologies both in planar and waveguide technologies can be imposed and associated coupling coefficients enforced during optimization. The design process is verified by measurements and comparison with results of commercially available field solvers

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Coupling-Matrix Design of Dual and Triple Passband Filters

In this paper, a class of triple-band bandpass filters with two transmission poles in each passband is proposed using three pairs of degenerate modes in a ring resonator. In order to provide a physical insight into the resonance movements, the equivalent lumped circuits are firstly developed, where two transmission poles in the first and third passbands can be distinctly tracked as a function of port separation angle. Under the choice of 135° and 45° port separations along a ring, four open-circuited stubs are attached symmetrically along the ring and they are treated as perturbation elements to split the two second-order degenerate modes, resulting in a two-pole second passband. To verify the proposed design concept, two filter prototypes on a single microstrip ring resonator are finally designed, fabricated, and measured. The three pairs of transmission poles are achieved in all three passbands, as demonstrated and verified in simulated and measured results.

Compact Dual-Mode Triple-Band Bandpass Filters Using Three Pairs of Degenerate Modes in a Ring Resonator

A novel approach for designing tri-band bandpass filters with independently controllable center frequencies and improved stopband rejection characteristic is presented in this paper. The assembled resonator constructed by a stepped impedance resonator and a common half-wavelength resonator is employed to obtain tri-band response. The stepped impedance resonator is designed to operate at the first and third passbands and the other resonator is designed to operate at the second passband. Two kinds of filter configurations with cascaded and pseudointerdigital formats are proposed. Based on lossless lumped-element equivalent circuit, it is found that both filter structures can introduce transmission zeros between passbands. To verify the proposed approach, two filters are designed and fabricated, the measured results exhibit tri-band bandpass responses with high selectivity.

Design of Compact Tri-Band Bandpass Filters Using Assembled Resonators

This paper presents a novel approach to the design of tunable dual-band bandpass filter (BPF) with independently tunable passband center frequencies and bandwidths. The newly proposed dual-band filter principally comprises two dual-mode single band filters using common input/output lines. Each single BPF is realized using a varactor-loaded transmission-line dual-mode resonator. The proposed filter also offers switchable characteristics to select either of the passbands (either the first or the second passband only). To suppress the harmonics over a broad bandwidth, defected ground structures are used at input/output feeding lines without degrading the passbands characteristics. From the experimental results, it was found that the proposed filter exhibited the first passband center frequency tunable range from 1.48 to 1.8 GHz with a 3-dB fractional bandwidth (FBW) variation from 5.76% to 8.55% and the second passband center frequency tunable range from 2.40 to 2.88 GHz with the 3-dB FBW variation from 8.28% to 12.42%. The measured harmonic results of the proposed filters showed a rejection level of 19 dB, which is up to more than ten times of the highest center frequency of the first passband without degradation of the passbands.

Dual-Band Bandpass Filter With Independently Tunable Center Frequencies and Bandwidths

Directional ultra-wideband antennas in various planar technologies are described. All designs feature a parabolic-shaped ground plane to accomplish high directivity and gain. Moreover, in comparison with a simple corner-shaped ground plane, the parabolic ground plane enhances bandwidth and improves input return loss. It also contributes to antenna compactness and efficiency in radar tracking applications. The salient features of the UWB antenna designs are demonstrated through two different full-wave simulation packages in the time and frequency domains.

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Directional Ultra-Wideband Antennas in Planar Technologies

New ultra-wideband stepped-impedance resonator configurations are presented which, in cascaded and folded forms, are well suited for compact small-size filter applications. Compared to similar structures known hitherto, improved stopband performance is obtained by structural folding and source-load coupling. A variety of different filter configurations is presented with bandwidths up to 105 percent covering the 3.1-10.6 GHz range. Excellent stopband performance is obtained up to 16 GHz. The filters are designed for standard microstrip applications on commonly used substrate materials, and their responses are verified by different commercial electromagnetic software packages.

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Folded Compact Ultra-Wideband Stepped-Impedance Resonator Filters

This paper presents new configurations for dual-band filter designs. Stepped impedance resonators are used to implement the dual-band characteristics. Due to their tunable spurious response properties, the new filters feature two controllable passbands at desired frequencies, high out-of-band rejection as well as a wide stopband regions created by a zero-phase feed structure without input/output matching networks. Moreover, the new topologies occupy less circuit space in comparison with traditional designs. Several new dual-band filter configurations have been designed on RT-Duroid 6006 substrate. Performances are verified using commercially available field solvers.

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New Reduced-Size Step-Impedance Dual-Band Filters with Enhanced Bandwidth and Stopband Performance

Dual-band and triple-band filters in uni-planar technology are designed using cross-coupled networks represented by coupling matrices. The multiband response is created by placing transmission zeros within the bandwidth of a wideband filter. Realizable planar topologies can be imposed and associated coupling coefficients enforced during optimization. The design method is demonstrated using three different planar resonator configurations: hairpin, open-loop and quasi-dual-mode resonators. Designs are verified by commercially available software packages and, in principle, by measurements.

/pdf/coupling-matrix-design-of-dual-triple-band-uni-planar-1c96xtg5qu.pdf

M. Mokhtaari

Papers

Coupling-Matrix Design of Dual and Triple Passband Filters

Directional Ultra-Wideband Antennas in Planar Technologies

Folded Compact Ultra-Wideband Stepped-Impedance Resonator Filters

New Reduced-Size Step-Impedance Dual-Band Filters with Enhanced Bandwidth and Stopband Performance

Coupling-Matrix Design of Dual/Triple-Band Uni-Planar Filters