Phase noise measuring method based on wide frequency range, short response time and high resolution

Abstract

The invention discloses a phase noise measuring method based on a wide frequency range, short response time and high resolution. The phase noise measuring method comprises the following steps of: firstly, conditioning and shaping a tested signal and a reference signal respectively, wherein the tested signal is stabilized by the conditioning, and the reference signal is shaped to be a high-frequency pulse suitable for sampling; secondly, carrying out standard phase shifting on the high-frequency reference pulse, and densely sampling the tested signal in a zero passage part by adopting the phase-shifted pulse and an original phase as a clock of an AD (analog-to-digital) converter, then recovering information indicating that the phases are overlapped and the overlapping is subjected to deviation, and controlling and processing the phase detecting information; thirdly, controlling a measuring gate with the processed phase detecting signal which serves as a switching signal, and carrying out high-resolution zero-clearance gating time measurement on phase overlapping points, thus showing the strength of phase noises by the variation of gating time; and fourthly, processing the gating time measuring information to achieve the conversion between the gating time variation and the phase noises, thus displaying a single-side phase noise power spectrum density curve of the tested signal.

Description

technical field [0001] The invention relates to a phase noise measurement method with wide frequency range, fast response time and high resolution. Background technique [0002] Phase processing and phase noise measurement are of great significance in the characteristics of basic frequency sources, research, application and performance testing of frequency base standards. The method of phase processing not only determines the frequency conversion, the phase-locking accuracy of the phase-locked loop and the complexity of the system, but also affects the feasibility and cost of the entire phase noise measurement equipment. In recent years, with the continuous expansion of the market demand for crystal oscillators, my country has become the second largest producer of crystal oscillators in the world, and the production technology of crystal oscillators is relatively high, with great potential for development. However, based on the phase noise of crystal oscillators The technolo...

AI Technical Summary

Problems solved by technology

Direct measurement of phase noise with a spectrum analyzer has the following limitations: (1) The noise floor of the spectrum analyzer, that is, the sensitivity

Because the background noise of general spectrum analysis instruments is relatively large, it is neither suitable for measuring frequency sources with low phase noise, nor is it suitable for measuring phase noise at places where the deviation from the carrier frequency is less than 1KHz; (2) the spectrum analyzer cannot modulate the amplitude (AM) noise is distinguished from frequency modulation (FM) noise, and the measured result is a combined noise

In order to accurately measure the phase noise, not only the AM noise of the signal under test is required to be much smaller than the FM noise, but also the noise floor of the spectrum analyzer is required to be lower than the noise of the signal under test, and the dynamic range is large; (3) Noise characteristics of the reference signal From the input RF signal to the intermediate frequency, it is possible to introduce new noise during the conversion process, so the introduced noise may overwhelm the noise of the measured signal, so that the measured result is the superposition of the two noises; (4) the spectrum analyzer uses It is a narrow resolution bandwidth, and the scan time is longer, increasing the time span

If the spectrum drift of the measured signal within the span time is greater than 1 / 20 of the total frequency span of the analyzer, the error of the measurement result will be large, and even the correct phase noise cannot be obtained

[0007] 2. Difference frequency method

The lower the frequency of the greatest common factor, the more obvious this trend is. In contrast, the fluctuation of the phase noise has a very weak impact on the output, and it is very difficult to measure

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