Cross-coupled Substrate Integrated Waveguide Filter Research Articles

New negative coupling structure and its application on substrate integrated waveguide bandpass filters

To design cross-coupled substrate integrated waveguide (SIW) bandpass filters (BPFs) with high performance, a new negative coupling structure is proposed, which is constructed by two coupled lines with shorted ends. The negative coupling structure is analyzed in detail. The stracture which can realize both relatively weak and strong negative coupling strength. The optimization method based on characteristic polynomials and reference zeros and poles of scattering parameters is realized for the filter design. To verify the proposed negative coupling structure, two fourth-order cross-coupled SIW BPFs with the center frequency of 10 GHz based on the optimized coupling matrixes are designed. The first one has a normalized bandwidth of 3% with a negative coupling in one cross-coupling path to illustrate the realization of weak negative coupling strength, and the second one has a normalized bandwidth of 8% with a negative coupling in one main coupling path to illustrate the realization of strong negative coupling strength. Finally, the two BPFs are fabricated and measured. Simulation and measurement results are in good agreement, which demonstrates the feasibility of the proposed negative coupling structure and its application on cross-coupled SIW filters with high performance. The influence of weak disperse cross coupling on locations of transmission zeros is also discussed.

Design and optimization of cross-coupled substrate integrated waveguide filters using space mapping method

This work presents an efficient method for the design of substrate integrated waveguide SIW filters. The proposed design approach is based on a combined use of equivalent circuit model of a filter and a space mapping technique. A reduced number of full-wave evaluations are needed, leading to a reduced optimization time. A novel SIW filter with improved stop-band characteristic using cross-coupling has been proposed. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:360-366, 2014.

Cross-Coupled Substrate Integrated Waveguide Filters With Improved Stopband Performance

In this letter, two $K$ -band cross-coupled substrate integrated waveguide (SIW) filters with improved stopband performance are proposed. To implement the negative coupling, ${\rm TE}_{201}$ -mode response is used in the first cavity, which is also used to implement cross-coupling with ${\rm TE}_{101}$ mode for generating additional transmission zeros (TZs) in the stopband of the filters. For each filter, two additional TZs are introduced and the stopband performance is then improved. The TZ provided by the first cavity can be introduced either below or above the passband, while the TZ provided by the fourth cavity can only be introduced above the passband. The two novel SIW filters are designed at the same center frequency of 20 GHz with the same bandwidth of 600 MHz. The measured data agree well with the simulated results.

Analytical design of novel dual-band cross-coupled substrate integrated waveguide filter

A dual-band substrate integrated waveguide (SIW) filter is presented in this article. The dual-band cross-coupled design procedure is based on the frequency transformation from the normalized frequency domain to the actual frequency domain, which can calculate the coupling coefficients and the external quality factors analytically. The cross-coupled SIW filter has the flexibility to achieve different kinds of filtering characteristics with the same coupling structure. To validate the method, a practical SIW dual-band filter operating at 5.85–5.95 GHz and 6.05–6.15 GHz is designed and fabricated. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1609–1612, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26908