Marjan Mokhtaari

Coupling-Matrix Design of Dual and Triple Passband Filters

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

Folded Compact Ultra-Wideband Stepped-Impedance Resonator Filters

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.

Directional Ultra-Wideband Antennas in Planar Technologies

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.

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

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

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

Dual-band and triple-band filters in uniplanar 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

Advanced Stepped-Impedance Dual-Band Filters With Wide Second Stopbands

Advanced dual-band stepped-impedance resonator filters are prototyped and their performances verified. The main advantages compared to traditional designs consist in two controllable passbands at desired frequencies, which is achieved by utilizing all-electric coupling, wide stopband regions towards higher frequencies and relatively small circuitry. Measurements over a wide frequency range verify the suitability of the resonator arrangements for advanced dual-band filter applications.

Dual-band stepped-impedance filters for ultra-wideband applications

New ultra-wideband planar dual-band filter designs are presented. Two broad passbands with up to 48 percent fractional bandwidths are obtained by utilizing quarter- wavelength coupled-line section to create additional reflection zeros within each passband. Parallel open-end high impedance segments in stepped-impedance resonators achieve passband separation as they provide attenuation poles between the passbands. Out-of-band rejection is improved by introducing source-load coupling, which produces attenuation poles in the lower and higher rejection bands. The basic design approach is discussed. Several different dual ultra-wideband filters are proposed. Two different professional EM software packages verify the individual responses.

Ultra-wideband and notched wideband filters with grounded vias in microstrip technology

In this paper, simple designs of UWB filters, with and without notching capability, are presented in microstrip technology. Section II describes the design procedures along with the proposed configurations. Section III reports the performances of the proposed filters and their verification using various electromagnetic-(EM)-field-based modeling tools.

Tunable notch characteristics in microstrip ultra-wideband filters

Tunable notch characteristics are introduced in microstrip ultra-wideband (UWB) filters. The UWB design concept is based on harmonic characteristics of a halfwavelength 50O transmission line (at the lowest resonance frequency), which is grounded on both sides. The notch performance is first created by additional capacitive-coupled open stubs. Subsequently, these stubs are replaced by a varactor and bypass capacitors which, in combination with the biasing transmission line, provide transmission zeros in the lower stopband. The basic filter layout exhibits flexibility and compactness. Three different commercial field solvers are used to verify the overall performances of the proposed filters and their tunable notch characteristics.

Initial design and optimization of broad-band and dual-band square-to-circular waveguide transitions

This paper presents guidelines for the design of square-to-circular waveguide transitions. Based on an algorithm developed for rectangular waveguide transformers, performances of initial and optimized transitions are presented. Although a direct transition from square to circular waveguide provides already a reasonable return loss, it is shown that more sections are required for broad-band and dual-band transitions. Verification of design and analysis procedures is provided through comparison with the commercially available field solver HFSS.