An ultra-wideband, high-precision quadrature signal generation circuit based on self-coupling LC compensated quadrature all-pass filters with PPF

This article presents an ultra-wideband, high-precision quadrature signal generation circuit based on self-coupling LC compensated quadrature all-pass filters(QAFs). A novel self-coupling technical and layout design is introduced in traditional LC compensated QAFs to extend the operating bandwidth and make it a compact design. The resonant balance condition and resonant frequency of self-coupling LC compensated QAFs are derived by a detailed analysis of transfer functions and filter parameters. The polyphase filter is also cascaded as a corrector to suppress the I/Q imbalance. The proof-of-concept 20–60 GHz self-coupling LC compensated QAF with PPF is designed with a core area of 252 ×160 μm². The output I/Q amplitude error is less than 0.12 dB at 20–60 GHz, and the phase error is less than 2.1°at 10–60 GHz. The signal loss varies from 1.2 to 3.9 dB (not including 1:2 power splitting). The effective image rejection ratio calculated based on I/Q mismatch is higher than 40 dB at 20-60 GHz.