A single-chip 15 to 30 GHz six-port demodulator for multi-Gb/s communication

A six-port circuit based on lumped passive components, i.e., R, L, and C, is proposed. Its size is much smaller than that of a conventional six-port circuit made of a power divider and 90° hybrid couplers. Consequently, the proposed circuit is suitable for fabrication on a MMIC die. The six-port circuit is designed and manufactured in a 65 nm CMOS technology together with power detectors, differential amplifiers, and a transformer balun, to build a demodulator. The measured quadrature output signal has an amplitude imbalance less than 2 dB and a phase error less than ±5° for a RF frequency from 15 to 30 GHz. Moreover, this demodulator chip was tested successfully to detect a 2.5 Gb/s QPSK signal modulated on a 15 GHz carrier.