Third-order intermodulation measurement method of spectrum analyzer and spectrum analyzer

Abstract

The invention provides a third-order intermodulation measurement method of a spectrum analyzer and the spectrum analyzer, the third-order intermodulation measurement channel is additionally arranged in the spectrum analyzer, the channel is only used for third-order intermodulation measurement, and the spectrum analysis channel and the third-order intermodulation measurement channel are switched through the first selector switch and the second selector switch; when spectrum analysis is carried out on a signal, the first selector switch and the second selector switch are controlled to connect the signal input end to the input end of the spectrum analysis channel, and the output end of the spectrum analysis channel is connected to the analog-to-digital conversion module for output; when three-order intermodulation measurement is carried out on the signal, the first selector switch and the second selector switch are controlled to connect the signal input end to the first input end of the three-order intermodulation measurement channel, and the output end of the three-order intermodulation measurement channel is connected to the analog-to-digital conversion module for output, so that signals do not need to pass through a three-level frequency conversion structure of the spectral analysis channel during three-order intermodulation measurement. And the third-order intermodulation performance of the spectrum analyzer is improved.

Description

technical field [0001] The invention relates to the technical field of spectrum analyzers, in particular to a third-order intermodulation measurement method of the spectrum analyzer and the spectrum analyzer. Background technique [0002] Third-order intermodulation is the spurious signal generated by the second harmonic component of one signal and the fundamental component of the other signal caused by nonlinear effects when two signals (frequency f1 and f2 respectively) pass through a nonlinear system (called third-order intermodulation products), whose frequencies are 2f1-f2 and 2f2-f1, respectively. The third-order intermodulation is a very important indicator in the communication system, which reflects the ability to interfere with adjacent channels and resist adjacent channel interference. [0003] The existing third-order intermodulation measurement methods basically use a spectrum analyzer for measurement, but the spectrum analyzer itself is a nonlinear system, whic...

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Problems solved by technology

[0003] The existing third-order intermodulation measurement methods basically use a spectrum analyzer for measurement, but the spectrum analyzer itself is a nonlinear system, which will deteriorate the third-order intermodulation of the signal to be measured (usually the spectrum analyzer is a three-stage frequency conversion structure, there are three mixers and at least three intermediate frequency amplifiers, and the third-order intermodulation will be deteriorated every time the signal to be tested passes through a mixer or amplifier), resulting in the limitation of the third-order intermodulation measurement

There is an adjustable attenuator inside the spectrum analyzer, increasing the attenuation of the adjustable attenuator can improve the third-order intermodulation measurement range of the spectrum analyzer, but the increase of the attenuation will deteriorate the noise figure, and the deterioration of the noise figure will make the spectrum analyzer The noise floor is raised. When the noise floor is higher than the amplitude of the third-order intermodulation product, the third-order intermodulation cannot be measured.

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