An Open-Loop Half-Quadrature Hybrid for Multiphase Signals Generation

In this paper, a passive half-quadrature hybrid (HQH) is presented for multiphase signal generation at radio frequencies. Utilizing capacitance ratios as the primary design parameters, the proposed hybrid exhibits excellent magnitude and phase balance even in the presence of process and temperature variations. Therefore, it is well suited for integrated-circuit designs with on-chip capacitive elements. Using a standard 0.18-μm CMOS process, the HQH circuit is integrated with a 5.6-GHz quadrature voltage-controlled oscillator (QVCO) and four down-conversion mixers for demonstration. As the QVCO oscillation frequency sweeps from 5.4 to 5.8 GHz, the measurement results indicate a root-mean-square (rms) magnitude error less than 0.5 dB and an rms phase error ranging from 4° to 7° at the half-quadrature outputs without any feedback correction.