A Low-Loss Broadband Quadrature Signal Generation Network for High Image Rejection at Millimeter-Wave Frequencies

This paper presents a broadband low-loss quadrature-hybrid-based network that enhances the phase and the amplitude matching of quadrature signals. The performance of this network is investigated, and a detailed theoretical analysis is provided. Several stages of this network can be cascaded to generate broadband balanced quadrature signals. Each stage has a loss of 0.5 dB and enhances the image rejection ratio (IRR) by approximately 8 dB. Compared with the conventional polyphase quadrature signal generation methods, the proposed network enables lower insertion loss, wider bandwidth, and reduced sensitivity to process variations. To verify the theoretical analyses, two proof-of-concept image-reject mixers are implemented in a 0.13-μm SiGe BiCMOS technology. The first mixer achieves an average IRR of 37.5 dB across 40-76 GHz, whereas the second mixer achieves an average IRR of 33.5 dB across 40-102 GHz. The proposed network is a promising solution for broadband quadrature signal generation at millimeter-wave frequencies, as it eliminates the need for calibration and tuning.