A compact ultrawideband bandpass filter with ultrafine 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, Krnfelt, Camilla, Ma, Shiwei, Wang, Xu, Meng, Linqin, Zirath, Herbert
• Format: Journal Article
• Language: English
• Published: Emerald Group Publishing Limited 06.02.2009
• Subjects: Electronic equipment and components; Liquid crystal polymers; Plasma physics; Substrates
• ISSN: 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 ultrawideband bandpass filter UWB BPF with ultrafine conductor traces working over 22 to 29GHz is fabricated on LCP substrates. Designmethodologyapproach 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 sputterdeposited onto the substrate. Findings The measured and the simulated results agree well. The measured insertion loss is about 8dB in the passband of the bandpass filter, which is a little high compared to the simulated result 5dB. The out of band performance at both the high frequency and low frequency is very good, almost higher than 35dB. Originalityvalue This paper presents the realization of UWB BPF working over 22 to 29GHz 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.