Zero-Pole Approach to Computer Aided Design of in-Line Siw Filters With Transmission Zeros

Abstract

Abstract-This paper presents a design of a new type of in-line pseudo-elliptic filters implemented in substrate integrated waveguide (SIW) technology. To realize transmission zeros in in-line topology, frequency-dependent couplings were used. Such dispersive couplings were implemented as shorted stubs. The design process starts with the generation of a suitable starting point. To this end, an approximation of SIW as a rectangular waveguide is used and a fast electromagnetic solver based on mode-matching technique is utilized (µWave Wizard). The next step is the optimization process of a filter in a full-wave 3D EM simulator Ansoft HFSS. The Optimization routine employs a cost function involving zeros and poles of the rational functions approximating scattering parameters. To increase the speed of convergence, a built-in derivative calculation feature was used and zeros and poles and their derivatives with respect to design parameters were extracted using the vector fitting algorithm. Experimental validation of the method is demonstrated by a third-order filter with asymmetric response and a fifth-order filter with two transmission zeros in addition to an asymmetric response. The experimental results show good agreement between the simulated and measured data.

Design of Compact Dual-Band Filter in Multilayer LTCC With Cross Coupling

“…A triple-passband Chebyshev filter and a dual-passband quasi-elliptic filter on the basis of substrate integrated waveguide (SIW) technology were demonstrated in [2]. A compact SIW filter was presented in [3] with the type of evanescedmode, while [4] presented the design method of a type of in-linepseudo-elliptic SIW filters. These filters usually occupy a large circuit area because of the planar arrangement of the resonators.…”

New Negative Coupling Structure for Substrate-Integrated Cavity Resonators and Its Application to Design of an Elliptic Response Filter

“…Recently, studies on negative coupling structures have presented physical realization of frequency responses with transmission zeros that enhance the frequency selectivity. Shorted stub implemented in substrateintegrated waveguide (SIW) can be used to realize transmission zeros [9]. Asymmetric feeding transmission line can also create transmission zeros [10,11].…”

Flat-Passband Substrate Integrated Waveguide Filter With Resistive Couplings

“…Im (J) = 2R (1 + cos 2θ) R 2 (1 + cos 2θ) 2 + 4Z 2 0 sin 2 2θ = bm 13 F BW (11) where b is the susceptance slope parameter of the SIW resonator, which can be extracted at the tapped location as shown in Fig. 5(a) with the full-wave simulator, ANSYS HFSS.…”

“…In [10], a predistorted filter is designed with SIW resonators which have an unloaded Q-factor of 500, and it achieves passband flatness equivalent to its counterparts with the Q-factor of 2000. Based on SIW technology, the filter in [11] realizes transmission zeros in in-line topology by frequency-dependent couplings. A three-pole Chebyshev SIW filter is designed by the lossy matrix synthesis in [12], but the configuration is complicated with two additional nonresonating nodes and three surface mounted resistors.…”