Miniaturized bandpass substrate integrated waveguide filter with frequency‐dependent coupling realized using asymmetric GCPW discontinuity

Abstract

An asymmetric GCPW discontinuity is proposed to provide frequency‐dependent coupling in microwave bandpass filters. Wider and narrow sections introduce, respectively, the capacitive and inductive component to the equivalent circuit representing coupling. By selecting the dimensions of the discontinuity and width of the inductive window in substrate integrated waveguide, an additional transmission zero can be introduced at prescribed positions. A distinct feature of the proposed structure is a small footprint and low loss. As an example, a bandpass filter with a central frequency of 4.6 GHz and a 200 MHz passband is designed, and its performance is measured. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1818–1821, 2015

Compact Quarter Mode and Eighth Mode Substrate Integrated Waveguide Bandpass Filters With Frequency-Dependent Coupling

“…To demonstrate the performance of the proposed FDC structure, QM and EM cavities are used to design SIW BPFs. Coupling matrix (CM) synthesis procedure in [4][5][6][7][8][9][10][11][12] serves as a theoretical guide to the filters design, where TZ is generated at upper stopband. Besides, broad stopband technique in [13][14][15] has been implemented to suppress higher parasitic modes for filter II (QMSIW).…”

“…With increasing demands for modern communication systems, miniaturization and high selectivity microwave bandpass filters (BPFs) have become urgently demanded. Substrate integrated waveguide (SIW) circuits [1][2][3][4][5][6][7][8][9] have attracted wide attention due to various advantages and characteristics, such as easy fabrication, high power handling capability, low insertion loss (IL), and easy integration with other circuits. However, conventional SIW filters still have relatively large circuit sizes.…”

“…Recently, half-mode (HM) [1], quarter-mode (QM) [2], and eighth-mode (EM) [3] SIW have been proposed, which decrease the dimension to 50%, 25%, and 12.5%, respectively, while maintaining the performance unchanged. To obtain high selectivity, FDC techniques [4][5][6][7][8][9][10][11][12][13] introduce additional finite transmission zeros without changing the topology and filter size. For SIW, due to its excellent coplanar properties, both constant and frequency-dependent couplings can be performed on it with positive effects.…”

“…In this paper, a coupling matrix (CM) synthesis procedure [9][10][11][12] is implemented to design second order filters: QMSIW and EMSIW. The detailed parameters of discontinuous structures containing FDC [4][5][6][7][8] are theoretically synthesized and simulated. As expected, one transmission zero is generated at the frequency point, where electric coupling cancels out with magnetic coupling for the designed BPFs by frequency dependent coupling between cavities.…”