A GaAs-Based Ultra-Wideband Common-Mode Filter Chip With Four Transmission Zeros and Equalization Integration

This article presents a novel circuit topology for ultra-wideband common-mode filter (CMF). The common-mode (CM) noise suppression stopband is enhanced by the capacitance coupling between two dual-mode LC tanks. Moreover, the RLC equalizers are integrated with the proposed CMF circuit topology to improve the signal integrity of the differential mode. Finally, the CMF chips are fabricated by the GaAs process for low-cost massive industry applications. For the CMF chip with equalizers, the measured differential-mode insertion losses are kept nearly constant at around -5 dB from dc to 8.1 GHz. The measured -10 dB CM stopband is from 2.2 to 9.4 GHz with a fractional bandwidth of 124%, which is the widest CM noise suppression stopband, compared with the other CMF chips based on the semiconductor process.