Microstrip band‐pass filters without source/load inverters
School of Electronic Engineering,
University of Electronic Science and
Technology of China, Chengdu, Sichuan
Fei Xiao, School of Electronic
Engineering, University of Electronic
Science and Technology of China,
Chengdu, Sichuan, 611731, China
National Natural Science Foundation of
China, Grant/Award Number: 61671111
In radio frequency/microwave or even higher frequency range, various
transmission‐line filters have been proposed for frequency selection.
Specifically, there is a kind of transmission‐line filters not having source/load
inverters. To design them is somewhat difficult, if their physical mechanism
is not fully understood. In this paper, the concept of the distributed‐ to
lumped‐element equivalence is applied in the synthesis of several microstrip
band‐pass filters without source/load inverters. As demonstrated, it can help
to reveal the physical mechanism of the filters such as how the resonances
are created and coupled. In addition, the distributed‐ to lumped‐element
equivalence relations between filter specifications and structural parameters
are presented and good initial dimensions are calculated, which will facilitate
filter design. Several examples are presented for demonstration.
complex general Chebyshev filter, direct synthesis technique (DST), distributed‐ to lumped‐element
equivalence (DLEE), full‐resonance filter, resonance
1 | INTRODUCTION
In radio frequency/microwave or even higher frequency range, transmission‐line filters are usually used for frequency
selection, such as microstrip filters, coplanar filters, finline filters, and waveguide filters. Up to now, a great number
of transmission‐line filters have been proposed for practical application.
For example, parallel‐coupled microstrip
band‐pass filter formed by the connection of some parallel‐coupled two‐line sections is presented in Cohn.
microstrip band‐pass filter consists of an array of some transmission‐line sections, each of which is shorted‐circuited at
one end and open‐circuited at the other end with alternative orientation
; Wolff discusses a second‐order microstrip
band‐pass filter based on a microstrip ring with a perturbation
; Zhu et al presents an ultrawideband microstrip band‐
pass filter with 2 parallel‐coupled line sections at the both sides of a low‐impedance line section
; Rectangular waveguide
band‐pass filter composed of waveguide cavities coupled through thick inductive irises is introduced
; Vahldieck et al
presents a waveguide band‐pass filter with the thin metal fins inserted in the mid plane of waveguide resonators.
Wang et al,
a fourth‐order waveguide band‐pass filter is studied, in which 4 inner conductive posts are placed within
a single cavity. Miniature wideband band‐pass filters are proposed by using multilayer liquid crystal polymer technology
in Qian and Hong.
Band‐pass filters using end‐connected conductor‐backed coplanar waveguide are proposed in Xiao
Shim et al
present a continuously tunable lumped band‐pass filter fabricated on a Borosilicate glass substrate
using a surface micromachining technology.
These transmission‐line filters are quite different in forms and have different features. Some are suitable for
narrowband band‐pass operation while others could exhibit wideband band‐pass response. Some might have
transmission zeros at infinity, while others could have transmission zeros at finite frequencies to improve frequency
selectivity. Actually, to design them is quite difficult, because of their distributed‐element effect. Although optimization
Received: 7 May 2017 Revised: 1 August 2017 Accepted: 2 October 2017
Int J Circ Theor Appl. 2018;46:415–426. Copyright © 2017 John Wiley & Sons, Ltd.wileyonlinelibrary.com/journal/cta 415