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In this work, we present a bilateral reflectionless filter topology. A low‐pass filter prototype and its theoretical frequency responses are given. The frequency responses are obtained by means of ABCD matrices, thereby showing that the proposed prototype is reciprocal, symmetrical, and reflectionless at both ports. A first‐order bandpass filter with the reflectionless characteristic has been designed by applying the conventional low‐pass‐to‐bandpass transformation to the proposed low‐pass filter topology. It is verified by measurement results that the proposed bandpass filter can have less than −20 dB reflection coefficient over the passband and stopband at both ports with the same transmission response of a conventional first‐order bandpass filter. [ABSTRACT FROM AUTHOR]

This Letter proposes a balanced hybrid substrate‐integrated waveguide (SIW)–coplanar waveguide (CPW) bandpass filter, which combines a hybrid SIW–CPW filter and a balanced structure for the first time. High performance common mode suppression can be achieved with high quality factor, compact size, and quasi‐elliptic differential mode response. [ABSTRACT FROM AUTHOR]

A simple method for a Q-band planar triple-mode filter with quasi-elliptic function response is proposed in this letter. This filter is implemented using a high-order mode cavity with substrate-integrated waveguide (SIW) technology and standard printed circuit board (PCB) process. By adopting an orthogonal input and output feed-line and introducing some perturbation, transmission zeros are generated on both sides, which have significantly improved filter selectivity and out-of-band rejection. This triple-mode resonator is then combined with a circular dual-mode cavity to obtain a highly selective filter in Q-band with better stopband rejection. Both of the two filters are fabricated and measured. Low insertion loss and sharp sideband characteristic are observed, which is in good agreement with simulation. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 600–603, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24114 [ABSTRACT FROM AUTHOR]