Continuously Tunable Ku-Band GaAs Bandstop Filter With Reconfigurable All-Pass Capabilities

A multiconfigurable monolithic microwave integrated circuit (MMIC) filter is reported. It exhibits three modes of operation, namely, a high-attenuation single-notch bandstop (BS) mode, a dual-notch BS mode, and an all-pass (AP) mode. It is based on a bridged-T network (BTN) using a minimum number of lumped elements and a signal cancellation technique to counteract the effect of the low on-chip quality factor. Transfer function tuning and bandstop-to-all-pass filter (BSF-to-AP) mode reconfigurability are readily obtained by tuning the frequency of two resonators. A prototype was manufactured using a pHEMT GaAs MMIC process exhibiting a BS mode with frequency tuning range (Δ f₀) of 16% and suppression up to 68.5 dB, a dual-notch BS mode withΔ f₀of 15% and 20% fractional bandwidth (FBW), and an AP mode with insertion loss <5.3 dB.