Retimed Phase-Selection Frequency Divider for Low-Jitter Switching

The retiming circuit generates retimed control signals in advance, before the phase selection switching occurs. By preparing the control signals beforehand with proper timing alignment to input signal voltage levels, the circuit ensures glitch-free switching without limiting the operational frequency. This preliminary preparation of control signals resolves the contradiction between high-speed operation and reliable glitch-free performance.

The invention extracts and eliminates the harmful modulus transition noise by using a different architectural approach. Instead of using dual-modulus or multi-modulus prescalers that inherently generate noise during modulus transitions, the patent employs a phase selection circuit with retimed control signals that achieves flexible frequency division ratios without the noise-generating modulus switching mechanism. This extraction of the noise-generating element resolves the contradiction between versatility and noise reduction.

The invention removes the inductor-based filtering requirement entirely by using a different high-speed frequency division approach. The phase selection circuit with retimed control signals achieves high-speed operation without requiring inductors for filtering out undesired mixed signals. This extraction of the inductor component resolves the contradiction between high-speed operation and compact circuit area.

The retiming circuit acts as an intermediary between the control signal generation and the phase selection switching. It introduces a timing alignment mechanism that ensures control signals are properly synchronized with input signal voltage levels, thereby improving system performance. While this adds some circuit complexity, the retiming function is a relatively simple timing adjustment circuit that enables high-speed glitch-free operation, making the performance improvement worthwhile.