A method to improve the finite surface roughness of an LCP-based microstrip filter at Q-Band

Abstract

In this paper, a 4-pole quasi-elliptic planar bandpass filter at Q-band on the liquid crystal polymer (LCP) is presented. The conventional design and development process of millimetre wave filters required to consider the surface roughness effects from the design stage for accurate development of filter at high frequency. Finite surface roughness of rolled copper and its impact on electrical performance are studied. Polishing is one of the methods to improve the conductor surface roughness. An improvement of 50% in surface roughness is reported for the rolled copper on the LCP, resulting in better than 1 dB insertion loss of the bandpass filter. Commensurate simulation and measurement results are presented.

KEYWORDS:

• Finite surface roughness (FSR)
• microstrip bandpass filter (MBPF)
• liquid crystal polymer (LCP)
• Q-band

Disclosure statement

No potential conflict of interest was reported by the author(s).