On-chip dual-band bandpass filter on a GaAs substrate

A dual-band bandpass filter in a millimetre-wave band that uses 0.5 μm GaAs pHEMT technology with two sets of stepped-impedance resonators, which results in a reduction in size, is presented. The two passband frequencies can be flexibly controlled by adjusting the lengths of the two sets of resonators. Two bandwidths can be tuned independently, using external quality factors and coupling coefficients. The fractional 1-dB bandwidths at 60 and 77 GHz are 8.6 and 4.1%, respectively. The measured S₂₁ values at 60 and 77 GHz are - 2.26 and - 3.9 dB. Good performance is obtained in terms of the excellent microwave properties of the semi-insulating GaAs substrate, which makes this system attractive for wireless communication applications.