Wideband and low-phase noise local frequency synthesizing circuit and method

Abstract

The invention provides a wideband and low-phase noise local frequency synthesizing circuit. The wideband and low-phase noise local frequency synthesizing circuit includes a direct digital frequency synthesizer, frequency multipliers, low-pass filters, high-pass filters, a band-pass filter, a quadrature mixer, a mixer, amplifiers, an integer frequency divider, a phase discriminator, a loop filter, a voltage-controlled oscillator and a coupler. According to the wideband and low-phase noise local frequency synthesizing circuit of the invention, high phase discrimination frequency is adopted perform phase discrimination, and therefore, phase noise deterioration of a loop can be decreased; the loop adopts the integer frequency divider, and therefore, the effects of the mantissa of fractional frequency division on phase noises can be eliminated; baseband signals generated by the direct digital frequency synthesizer are subjected to quadrature up-conversion, so that high-resolution, low-phase noise and high-frequency signals can be generated, and the high-frequency signals and the output of the voltage-controlled oscillator are subjected to mixing down-conversion, and signals obtained after the down-conversion can become signals with large step. Since the output of the voltage-controlled oscillator and the high-resolution and low-phase noise signals are subjected to the down-conversion, the input frequency of the integer frequency divider can be reduced, and the frequency division ratio of integer frequency division can be decreased.

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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