A broadband low phase noise local oscillator frequency synthesis circuit and method

Abstract

The invention proposes a broadband low-phase noise local oscillator frequency synthesis circuit, comprising: a direct digital frequency synthesizer, a frequency multiplier, a low-pass filter, a high-pass filter, a band-pass filter, a quadrature mixer, a frequency mixer Amplifiers, Integer Frequency Dividers, Phase Detectors, Loop Filters, Voltage Controlled Oscillators, Couplers. The invention firstly adopts high phase detection frequency for phase detection to reduce the deterioration of the phase noise of the loop; secondly, the loop adopts an integer frequency divider to eliminate the influence of the mantissa of the fractional frequency division on the phase noise; the baseband generated by the direct digital frequency synthesizer is used. The signal is quadrature up-converted to generate a high-resolution and low-phase noise high-frequency signal, which is mixed with the output of the voltage-controlled oscillator and down-converted, so that the down-converted signal becomes a large-step signal; voltage-controlled oscillation The inverter output is down-converted with a high-resolution low-phase noise signal, reducing the input frequency of the integer divider and reducing the frequency division ratio of the integer divider.

Description

technical field [0001] The invention relates to the field of radio frequency and microwave, in particular to a broadband low-phase noise local oscillator frequency synthesis circuit, and also relates to a broadband low-phase noise local oscillator frequency synthesis method. Background technique [0002] Spectrum analysis technology is a very important analysis method in the field of radio frequency and microwave. In the design of modern spectrum analyzers, most of them adopt superheterodyne technology. Therefore, the local oscillator signal, especially the first local oscillator signal, directly determines the spectrum analysis. instrument performance. The use of phase-locked loop technology can greatly improve the noise performance of the local oscillator signal, thereby improving the test performance of the spectrum analyzer. [0003] The development of frequency synthesis technology is mainly composed of three stages: traditional analog direct frequency synthesizer, pha...

AI Technical Summary

Problems solved by technology

[0013] The prior art uses a multi-loop phase-locked frequency synthesizer to realize broadband low-phase noise local oscillator frequency synthesis. The circuit is divided into a sampling loop, a direct digital frequency synthesizer (DDS), a pre-tuning loop, and a main phase-locked loop. The complexity is very high, the cost is high, and the debugging is difficult, and the locking of each frequency point needs to control each part of the circuit, and switch the pre-tuning loop and the main phase-locked loop, the control is too complicated

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