Ultra-low phase noise frequency synthesizer based on surface acoustic wave filter

Abstract

The invention provides an ultra-low phase noise frequency synthesizer based on a surface acoustic wave filter, which is characterized in that a microwave signal generated by a constant-temperature crystal oscillator is divided into a plurality of paths through a frequency distributor, one path is used as a main frequency signal, and the other path is used as a reference clock signal to be output to a direct digital frequency synthesizer to generate a secondary frequency signal; frequency mixing is performed on the primary frequency signal and the secondary frequency signal through a frequency mixer, and band-pass filtering is performed on an output radio frequency signal through a surface acoustic wave filter to obtain a sum frequency signal; a sum frequency signal is sent to the phase discriminator after being subjected to power amplification, the sum frequency signal and a radio frequency signal which is output by the medium oscillator and passes through the frequency divider are subjected to phase comparison, an error signal is obtained, an output signal of the phase discriminator is input into the voltage control end of the medium oscillator through the loop filter, the frequency of the medium oscillator is locked in a local oscillator, and finally the needed target frequency is obtained. The ultra-low phase noise frequency synthesizer is simple in structure, the phase noise is close to the theoretical frequency multiplication noise limit, and the ultra-low phase noise frequency synthesizer is suitable for small and miniaturized microwave atomic clocks.

Description

technical field [0001] The invention belongs to the field of microwaves and atomic clocks, and in particular relates to a frequency synthesizer technology, which can realize an ultra-low phase noise microwave source and is applied to miniaturized and miniaturized coherent layout trapping (CPT) atomic clocks. Background technique [0002] Coherent Layout Trapping (CPT) based on the principle of quantum interference can realize miniaturized atomic clocks, and it is currently the only atomic clock that has realized chips. Miniature atomic clocks are ideal for applications where volume, weight, and power consumption are limited and precision time is required, such as micro-nano satellites, drones, portable GNSS receivers, submarines, etc. [0003] At present, the small coherent layout trapping (CPT) atomic clock in the world has a short-term frequency stability of 10 -11 τ -1 / 2 order of magnitude, chip CPT atomic clock at 10 -10 τ -1 / 2 The phase noise of the microwave is an ...

AI Technical Summary

Problems solved by technology

[0008] In order to overcome the existing OCXO-based microwave frequency synthesizer's complex structure and poor phase noise, the present invention provides a surface acoustic filter-based ultra-low phase noise frequency synthesizer applied to coherent population trapped (CPT) atomic clocks , the system structure is simple, the phase noise is close to the limit of the theoretical multiplier noise, and it is suitable for small and miniaturized microwave atomic clocks such as CPT

Images