Highly selective bandpass filter based on substrate integrated waveguide

Abstract

A novel highly selective six-pole elliptic filter based on a substrate integrated waveguide (SIW) is proposed for the first time. The filter is composed of two planar SIW extend doublets. The modular design approach based on cascading small building blocks is adopted to reduce the effect of manufacturing tolerance on the performance of the filter. The proposed filter can produce four finite transmission zeros, and has an excellent stopband rejection characteristic. Measured results are presented and compared with results simulated by a high frequency structure simulator. Good agreement between simulated and measured results is observed.Introduction: The rapid development of microwave and millimetrewave communication systems has greatly stimulated the demand for high performance microwave filters with compact size and low cost. Elliptic and pseudoelliptic filters offer optimal solutions to the filtering structure, having sharp cutoff skirts and low in-band insertion loss. Although canonical folded coupling schemes, possibly with additional diagonal coupling, to implement an elliptic and pseudoelliptic filter of arbitrary orders and with arbitrary positioned transmission zeros are known, they tend to be too sensitive to manufacturing tolerances, especially for high-order filters. Recently, a modular design approach based on cascading small building blocks has been proposed and tested, which can reduced the effect of manufacturing tolerance on the performance of elliptic and pseudoelliptic filters [1 -3].

Substrate integrated folded waveguide controllable mixed electric and magnetic coupling structure and its application to millimetre-wave pseudo-elliptic filters

“…Creating transmission zeros (TZs) to achieve pseudo‐elliptic filtering function is an efficient method for superior frequency selectivity. Therefore, a variety of SIW‐based microwave and mmW pseudo‐elliptic filters with high frequency selectivity have been successfully designed using standard printed circuit board (PCB) or low‐temperature co‐fired ceramic (LTCC) . Among these SIW filters, cross‐coupling, source‐load‐coupling, doublet, trisection, and non‐resonating nodes (NRNs) are the main topologies used to create TZs at finite frequencies, where electric or magnetic coupling usually individually exists between two adjacent resonators.…”

A Three-Pole Substrate Integrated Waveguide Bandpass Filter Using New Coupling Scheme

“…To realize a sharp transition band and improve selectivity of the filter, high order or multi-pole filters are needed. In [7], a planar SIW elliptic BPF is investigated by cascading two extend doublets. Multi-pole BPFs are realized by etching a multimode microstrip resonator on the top metal layer or on the bottom ground layer of a SIW resonator in [8] and [9].…”

Pseudo-elliptic substrate integrated waveguide filters with higher-order mode resonances

“…Elliptic and quasi-elliptic bandpass filters with cross coupling are standard solutions to filtering specifications involving sharp selectivity, low in-band insertion loss, and high out of band rejection [5,6]. However, both the unloaded Q-factor and the dimension of a SIW cavity decrease with increasing frequency.…”