Natalia Leszczynska

A Substrate Integrated Waveguide (SIW) Bandpass Filter in A Box Configuration With Frequency-Dependent Coupling

This letter presents the design of a microwave bandpass filter with frequency-dependent coupling implemented in substrate integrated waveguide (SIW) technology. The proposed filter implements a four-pole generalized Chebyshev filtering function with two transmission zeros. Resonators are arranged in an extended box configuration with dispersive coupling on a main signal path, which produces an extra zero in comparison to classical approaches. The frequency-dependent coupling is implemented as a shorted stub with an additional septum made from via-holes. Such modification allows better control of the positions of the resonant frequencies of coupled SIW cavities, as well as of the position of the transmission zero. The filter was fabricated in SIW technology and good agreement was achieved between the simulated results and those measured.

A NOVEL SYNTHESIS TECHNIQUE FOR MICROWAVE BANDPASS FILTERS WITH FREQUENCY-DEPENDENT COUPLINGS

This paper presents a novel synthesis technique for microwave bandpass fllters with frequency-dependent couplings. The proposed method is based on the systematic extraction of a dispersive coupling coe-cient using an optimization technique based on the zeros and poles of scattering parameters representing two coupled resonators. The application of this method of synthesis is illustrated using two examples involving four and flve-pole generalized Chebyshev fllters implemented in substrate-integrated waveguide (SIW) technology. As a dispersive inverter, a parallel shorted stub with an additional septum was used. The septum lends greater ∞exibility to the dimensional synthesis, in that it increases the allowable range of the coupling coe-cients. The measured and simulated results are in excellent agreement, which conflrms the validity of the proposed approach.

Generalized Chebyshev Bandpass Filters With Frequency-Dependent Couplings Based on Stubs

This paper presents an accurate synthesis method for inline and cross-coupled generalized Chebyshev bandpass filters with frequency-dependent couplings implemented via open and short stubs. The technique involves the synthesis of a lumped-element prototype in the form of a coupling matrix with a frequency-dependent term and the conversion of this prototype to a distributed-element model composed of sections of TEM lines. This takes into account the impedance (or admittance) of the stubs, thus allowing compensation for the loading effect. The design equations are derived for the stub impedance in terms of a coupling coefficient and for the allowable frequency range in which the model is valid. Additionally, the proposed methodology allows the simultaneous application of frequency-dependent couplings with positive and negative dispersive parts within the same network. The validity of this method is confirmed by numerical tests and through experiments, including filters with dispersive couplings of the opposite signs.

Zero-Pole Space Mapping for CAD of Filters

In this letter, we propose a new space-mapping technique tailored to the CAD of microwave filters. The goal of space mapping is to achieve a satisfactory design with the minimal number of fine model evaluations. In our approach, the filter is represented by a rational function. To quickly align the coarse and fine models, and to speed up the direct optimization of the coarse model, we propose matching the zeros and poles of a rational function extracted from scattering parameters, rather than the frequency responses.

Dimensional Synthesis of Coupled-Resonator Pseudoelliptic Microwave Bandpass Filters With Constant and Dispersive Couplings

In this paper, we propose a novel technique for the dimensional synthesis of coupled-resonator pseudoelliptic microwave filters with constant and dispersive couplings. The proposed technique is based on numerical simulations of small structures, involving up to two adjacent resonators, and it accounts for a loading effect from other resonators by replacing them with terminations coupled through appropriately scaled inverters. The dimensions of the resonators and coupling elements are determined by an optimization process that matches the zeros and poles of the simulated response of a low-order circuit consisting of one or two coupled resonators connected to a source and to matched loads with the eigenvalues of a submatrix obtained from the coupling matrix of the lumped-element model of the filter. To assure high accuracy and rapid convergence, a zero-pole optimization algorithm was used. The application of this method is illustrated with four examples involving a simple fourth-order open-loop microstrip filter with two transmission zeros, through a triplet with one transmission zero, a quadruplet with two asymmetric transmission zeros located on both sides of the passband, to a fourth-order waveguide filter with three transmission zeros. The validity of the method is confirmed by an experiment involving a filter with dispersive coupling realized in substrate-integrated waveguide technology.

A Linear Phase Filter in Quadruplet Topology With Frequency-Dependent Couplings

This letter presents a design of a linear phase microwave bandpass filter. The filter is composed of four resonators arranged in the quadruplet topology. Making the cross and one direct coupling dispersive gives additional design flexibility. The first advantage of using frequency-dependent couplings is the possibility to chose an arbitrary location of a pair of complex transmission zeros (TZs) in the s-domain. The second one is the presence of an additional imaginary transmission zero that improves the filter selectivity. We provide a proof-of-concept design of a filter using substrate integrated waveguide (SIW) technology. The frequency-dependent couplings are implemented in SIW as a composition of both: an inductive part realized in a form of an H-plane iris and a capacitive part realized as a grounded coplanar waveguide (GCPW). The measured filter characteristics prove the validity of the model.

Fast Full-Wave Multilevel Zero-Pole Optimization of Microwave Filters

A new concept is proposed for the full-wave computer-aided design of microwave filters. The method consists of two stages and operates on the zeros and poles of the transfer function and their derivatives. These quantities are evaluated from the response computed by a full-wave electromagnetic solver with two levels of accuracy. The two stages make use of different models that are optimized using a low-accuracy electromagnetic solver. The design involves one coarse-level optimization in the first stage and a few iterations in the second stage, each requiring a single computation of a high-accuracy response. The effectiveness of the proposed technique is demonstrated with two examples, in which design closure was achieved with just three evaluations of the high-accuracy full-wave solutions irrespective of the quality of the initial design.

Design of substrate integrated waveguide filters using implicit space mapping technique

In this paper an automated procedure for design of substrate integrated waveguide filters based on the implicit space mapping technique is proposed. The space mapping method consists two major steps: a fast coarse model optimization to achieve an initial design and a parameter extraction procedure for aligning the approximate response with reference computations based on more accurate electromagnetic analysis. In this paper a mode matching solver is used for fast computation and the reference results are computed with the finite-difference frequency domain technique. The efficiency of the procedure is demonstrated on example of substrate integrated waveguide (SIW) filter.

Substrate-integrated waveguide (SIW) filter design using space mapping

In this paper, we present a fast technique for an automated design of microwave filters in substrate integrated wave (SIW) technology. The proposed methodology combines the space mapping technique with a cost function defined using the location of complex zeros and poles of filters transfer and reflection function and uses a rectangular waveguide as a surrogate model. The effectiveness of the proposed technique is presented with an illustrative example.

Automated design of linear phase filters

This paper presents a fast technique for an automated design of microwave filters with linear phase. The proposed method exploits the cost function defined using the location of complex zeros and poles of the filters transfer and reflection function. The effectiveness of the proposed technique is presented with two illustrative examples.