Method and device for measuring frequency characteristics based on zero-intermediate-frequency quadratic orthogonal demodulation

Abstract

The invention discloses a device for measuring frequency characteristics based on zero-intermediate-frequency quadratic orthogonal demodulation. The device comprises an orthogonal frequency sweeping signal source, wherein a first output end of the orthogonal frequency sweeping signal source is connected with a first multiplying unit and a third multiplying unit; a second output end of the orthogonal frequency sweeping signal source is connected with a second multiplying unit and a fourth multiplying unit; an independent frequency sweeping signal source is connected with a measured network, the first multiplying unit and the second multiplying unit; the measured network is connected with the third multiplying unit and the fourth multiplying unit; the first multiplying unit, the second multiplying unit, the third multiplying unit and the fourth multiplying unit are respectively sequentially connected with a low-pass filter and an ADC (Analog to Digital Converter) module; the ADC module is connected with an MCU (Micro-programmed Control Unit) module; the MCU module is connected with a displayer. The invention also discloses a method for measuring the frequency characteristics based on the zero-intermediate-frequency quadratic orthogonal demodulation. By adopting the zero-intermediate-frequency quadratic orthogonal demodulation, the method and the device solve the problem of IQ mismatch in orthogonal demodulation and realize accurate measurement on frequency characteristics of the network (circuit).

Description

Technical field [0001] The present invention uses the zero-IF principle in the field of communication electronics to propose a frequency characteristic measurement method and device based on zero-IF secondary quadrature demodulation, which is mainly applied to the development and design of frequency characteristic testers. Background technique [0002] When testing the performance of an electronic device or network, its frequency characteristic test is essential. There are many existing frequency characteristic measurement methods, each with advantages and disadvantages. [0003] 1. Use discrete components. Mainly include sweep frequency signal source, amplitude frequency measurement module, phase frequency measurement module, frequency characteristic display module, such as figure 1 Shown. The measurement principle is that the frequency sweep signal source outputs a sinusoidal AC signal Acosωt, which is input to the measured network, amplitude-frequency measurement module, and p...

AI Technical Summary

Problems solved by technology

This method relies too much on the performance of the AD8302 chip. The amplitude measurement of this chip is relatively accurate, but the phase measurement has a large error, especially at the phase points of 0°, 180°, and -180°, which will produce a phase-frequency characteristic curve. mutations and distortions, which are the limitations of this scheme in phase-frequency measurements

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