Phase noise performance of analog frequency dividers

Measurements are reported of the spectral performance of two types of analog dividers: 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 =f_in2. Prototype dividers were constructed utilizing abrupt junction varactor diodes and were designed without the need for the critical tuning or the input and output trap circuits normally used. At the specified 20 dBm drive, 6 dB conversion loss was obtained. Lowest 1/f noise was obtained with the varactor biased to insure nonconduction over the entire cycle of the RF waveform. Unlike the parametric divider, a regenerative-type divider can be operated over a wide range of drive levels and over a much wider bandwidth. The use of the regenerative-type divider appears especially attractive because it provides low 1/f noise and noise floor performance