Design of 4th order cylindrical filter suitable for SU-8 micromachining

摘要

A 4^th order bandpass filter based on cylindrical resonators operating in W band is presented in this paper. The proposed filter was made of three copper-coated SU-8 layers with the nominal thickness of 0.5 mm. The cylindrical resonators operate in TM010mode, hence the resonator frequency is independent with the height of the resonator and this reduced the difficulty to control the thickness of the SU8 layers. This filter is designed to have a center frequency of 90GHz, a fractional bandwidth of 5% and a passband return loss of 20dB. This paper also analyzes the dimensional sensitivity of the filter from two aspects: the thickness of the resonator and the assembly between the SU-8 layers. The sensitivity of bandpass response shows low sensitivity to this tolerance and S11is below -15dB. The frequency shift does not exceed 114.5MHz (0.127% of the center frequency).