Tunable 1.3–2.1-GHz Parametric Notch Filtering on GaAs MMIC With Double Pump Q-Enhancement

This paper presents a tunable parametric notch filter based on a double-pump parametric-mixing architecture that enables on-chip Q-enhancement. A primary pump generates a frequency-dependent positive conductance at the signal frequency, producing a tunable absorption notch, while a secondary pump introduces negative resistance at the idler frequency to compensate resonator loss and enhance selectivity. This mechanism, referred to as parametric mixing, enables active control of the effective quality factor of the idler resonance without external high-Q components. The proposed architecture is implemented as a fully integrated GaAs MMIC and operates over a tuning range of 1.3-2.1 GHz. Measurements show that single-pump operation produces a tunable notch with 4.5-6 dB attenuation, while activation of the second pump increases the notch depth to 13.5-25 dB and reduces the fractional bandwidth to 5.5-6.5%, consistent with Q-enhanced behavior. The device also exhibits a low-loss through response when both pumps are disabled, enabling a true notch-off state. Measured S-parameters show that the double-pump operation substantially improves notch depth and fractional bandwidth, while simulation-based effective-Q extraction supports the interpretation that this improvement results from idler loss compensation, providing a compact and scalable solution for high-selectivity reconfigurable RF filtering.