Complex signal processing used in modern RF transceivers

This paper first describes the evolution of RF transceiver architectures, especially focusing on state-of-the-art CMOS system-on-a-chip (SoC) implementation and software-defined radios (SDRs). Because, in these modern RF transceivers, complex signal processing is indispensable for digital modulation/demodulation and side-band or image-signal rejection in frequency conversion processes, fundamentals of complex signal processing are reviewed. Finally, we propose a high-precision complex quadrature modulator suitable for modern RF transmitters using multi-symbol quadrature amplitude modulation (QAM), which features the inherent correction mechanism of local-oscillator (LO) phase and amplitude errors. Especially, a newly proposed "dual-LO-switching passive quadrature mixer" plays an important role in the LO-phase error correction.