New Frequency Divider with 8 Output Phases for Phase Switching Prescaler

A 5.6 GHz divided-by-7/8 prescaler is presented. A phase switching technique is used, and the prescaler has 8 pi/4 -spaced output phases. Two parallel divided-by-2 flip- flops are usually used to generate 8 output phases, but this architecture suffers from the uncertainty of its output phase patterns. In this paper we propose a novel circuit which has four serially connected differential latches and which can generate 8 output phases without any phase-pattern uncertainty. It decreases the logic complexity of phase switching prescalers and improves the noise immunity which is an important merit when the PLL integrated with noisy digital circuits and in low-voltage implementation.