Modified maximally flat parallel‐coupled lines for band‐pass filter applications and miniaturizations

Abstract

The modified configurations of maximally flat parallel‐coupled lines (MF‐PCL) structure are introduced to improve the performance of the conventional MF‐PCL resonator. To obtain a higher rejection (−39 dB), symmetry response, wider band (BW about 32%), and less insertion loss (−0.4 dB) filters at central frequency 5.78 GHz, the modified MF‐PCL resonators by using enhanced coupling techniques are proposed herein. The size reduction of 50% is achieved. Results including surface current distributions and frequency responses are presented and discussed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 902–906, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23243

Parallel coupled CPW filters for spurious band suppression

“…Since the seminal article by Cohn [1], parallel coupled-line filters have been exhaustively used in microwave systems, but they are still an object of research even nowadays [2]. When nonhomogeneous transmission lines, such as microstrips or coplanar waveguides (CPWs), are used for this purpose, it is well known that the mismatching of the modal phase velocities causes an undesired spurious band that appears at twice the cen-tral frequency of the filter and thus degrading out-of-band rejection.…”

“…In this respect, there has been a lot of interest in planar inverted-F antenna (PIFA). Many literatures have studied and devoted for different PIFA designs [1][2][3]. The PIFA has many advantages, such as easy fabrication and low cost.…”