Phase Noise Performance of Analog Frequency Dividers

Abstract

The phase noise performance obtainable using TTL and ECL logic level, silicon and GaAs-based, digital frequency dividers is available in the literature. Measurement of the spectral performance of two types of analog dividers are reported: a parametric divider using varactor diodes and a regenerative type divider incorporating a double balanced mixer in the oscillator feedback circuit. Both dividers were configured for divide-by-two operation at VHF. The parametric divider typically requires a moderately high-input drive level and operates over relatively narrow bandwidth owing to the nature of the circuit constraints for generation of negative resistance at the output frequency. Phase-noise performance was characterized by £(100 HZ) ~-148 dBc/HZ and a phase noise floor level of -172 dBc/HZ. This compares favorably with corresponding values of -148 dBC/HZ (and -155 dBc/HZ noise floor) obtained using ECL dividers. Unlike the parametric divider, a regenerative type divider can be operated over a wide range of drive levels and over a much wider (mixer) bandwidth. This type of divider incorporates a frequency conversion in the oscillator feedback circuit. For divide-by-two operation, the oscillator operates atfout = fin/2 and contains a low pass filter to suppress the mixer sum frequency at 3 ft/2. Results obtained for prototype divide-by-two circuits using this technique and incorporating low 1/f noise modular amplifiers are characterized by £(100 HZ) ~ -157 dBc/HZ and noise floor levels of -174 dBc/HZ for dividers operated at +5 dBm 160 MHz input signal drive. The use of the regenerative type divider appears especially attractive since it provides low 1/f noise and noise floor performance. Because all circuit components except for the filter are ultra-broadband, the non-filter portion of the circuit could be packaged as a modular type component designed to perform over user-selected portions the entire HF-UHF range. © 1990 IEEE