A phase-shifting PLL frequency offseter
Publikation/Tidskrift/Serie: Journal of Physics E: Scientific Instruments
A phase-shifting PLL frequency offsetter has been developed for use in the comparison of near-equal frequencies by phase-time recordings. The input frequency is shifted by means of a phase-shifting phase-locked loop. Time-linear phase shifting is simply obtained by inserting an RC link in the loop. Continuous operation is obtained by polarity switching of the capacitor and the phase detector at suitable phase values. An experimental circuit working around 114 kHz is presented, providing offset frequencies in the range 1 mHz to 10 Hz. The circuit uses eight analogue ICs. The output frequency stability depends on the input frequency stability, the fractional frequency offset and the stability of the analogue circuit, and is, for the circuit presented, a few parts in 1010 at an offset frequency of 0.01 Hz if the input frequency is based on a Cs or Rb source. The method can be used for frequencies up to the MHz range.
- Technology and Engineering
- ISSN: 0022-3735