A compact ultra-wideband bandpass filter with ultra-fine conductor trace based on liquid crystal polymer substrates

• Published in: Circuit world Vol. 35; no. 1; pp. 16 - 21
• Main Authors: Zhang, Xia, Liu, Johan, Kärnfelt, Camilla, Ma, Shiwei, Wang, Xu, Meng, Linqin, Zirath, Herbert
• Format: Journal Article
• Language: English
• Published: Bradford Emerald Group Publishing Limited 01.01.2009
• Subjects: Copper; Electronics; Heat resistance; Liquid crystal polymers; Mechanical properties; Moisture absorption; Plasma etching; Plasma physics; Studies; Substrates; Titanium; Plasma physics; Electronic equipment and components; Liquid crystal polymers; Substrates
• ISSN: 0305-6120; 1758-602X; 0305-6120
• DOI: 10.1108/03056120910928680

Purpose - Liquid Crystal Polymer (LCP) materials are considered to be promising substrates for wireless applications because of their excellent properties. The purpose of this paper is to describe now a novel and compact microstrip ultra-wideband bandpass filter (UWB BPF) with ultra-fine conductor traces working over 22 to 29 GHz is fabricated on LCP substrates.Design methodology approach - Using standard processing technology, such as photolithography, plasma pretreatment, sputter deposition and wet etching, a microstrip UWB BPF is fabricated on LCP substrates. In order to obtain better adhesion between LCP substrate and copper, the oxygen plasma pretreatment of the LCP substrate surface and a thin titanium adhesion layer are introduced before a copper layer is sputter-deposited onto the substrate.Findings - The measured and the simulated results agree well. The measured insertion loss is about 8 dB in the passband of the bandpass filter, which is a little high compared to the simulated result (∼5 dB). The out of band performance at both the high frequency and low frequency is very good, almost higher than 35 dB.Originality value - This paper presents the realization of (UWB BPF) working over 22 to 29 GHz based on an LCP substrate, which demonstrates the feasibility of the application of the LCP substrate in RF wireless systems and also gives some useful information for later research.