Wide-locking-range multi-phase-outputs regenerative frequency dividers using even-harmonic mixers and CML loop dividers

This paper presents a divide-by-4 (D4) and divide-by-8 (D8) regenerative frequency dividers (RFDs) with the quadrature and the octet outputs. The topologies of the D4 and D8 RFDs use the even-harmonic mixers and the current-mode-logic (CML) loop dividers to achieve high division ratio and wide locking ranges. The modified Gilbert cells with quadrature- and octet-phases local-oscillator switching transistors are adopted to perform 2\times and 4\times subharmonic mixing with good conversion efficiency. The divide-by-2 and D4 CML loop dividers are used to obtain wide frequency range and the quadrature and the octet outputs. The D4 and D8 RFDs were fabricated by using a 90-nm CMOS process. With consuming 10.8 and 17.8 mW of dc power, the measured locking ranges of the D4 and D8 dividers are 13.2-18.4 and 16.8-26 GHz, respectively. Over the whole locking range, the two dividers with the phase deviation between the quadrature and the octet signals to be less than 2.2^\circ and 4.4^\circ, respectively. The proposed circuits achieve wide locking ranges and accurate output phases, making them very attractive for application into a multi-phase generator.