Self-adaptive orthogonal demodulation method

Abstract

The invention discloses a self-adaptive orthogonal demodulation method, which comprises the following steps of: establishing a C / V conversion circuit, and acquiring response signals to form a discrete sequence; estimating the length of a single-cycle sequence of a measured signal in the discrete sequence to obtain a group of in-phase factors and orthogonal factors; obtaining amplitude information and phase information of a group of measured signals according to the in-phase factor and the orthogonal factor; compensating the in-phase factor and the orthogonal factor to obtain a compensated in-phase factor and a compensated orthogonal factor; obtaining amplitude information and phase information of a group of measured signals again according to the compensation in-phase factor and the compensation orthogonal factor; and calculating compensation remainders of the in-phase factor and the orthogonal factor again according to the amplitude information and the phase information, obtaining a compensation in-phase factor and a compensation orthogonal factor, further obtaining a group of amplitude information and phase information again, and repeating the iteration process, when the difference between the amplitude information and the phase information obtained in two adjacent times is smaller than a set threshold value, stopping iteration, and recording a final result.

Description

technical field [0001] The invention relates to the technical field of signal processing, in particular to an adaptive quadrature demodulation method. Background technique [0002] The AC capacitance measurement circuit is widely used in measuring instruments. Many laboratory high-precision instruments are based on the AC capacitance measurement circuit. The equivalent circuit diagram is as follows: figure 2 As shown, when measuring, it is necessary to use a sinusoidal signal of a suitable frequency as the excitation signal V I , then the corresponding signal is When the circuit feedback is resistive feedback, the response speed of this link is better, and resistive feedback means that jωR 12 C 36 <<1, so the transfer function of this link is Then the amplitude characteristic and phase characteristic of the response signal can be obtained as Therefore, only the amplitude of the response signal is required to measure the measured capacitance value. Ideally, the ...

AI Technical Summary

Problems solved by technology

And when the frequency fluctuates in a small range, such as a fluctuation of 5%, this means that solutions such as fast Fourier transform and filters have no obvious effect

However, such frequency fluctuations are enough to have a more obvious impact on the demodulation results, resulting in a decrease in demodulation accuracy.

The method to solve the problem of demodulation accuracy decline is usually to use high sampling frequency, which is a method based on experience. High sampling frequency means using high-speed AD chips. Although it can improve demodulation accuracy to a certain extent, it will increase significantly. Under the premise of cost, the accuracy improvement is still limited, and the problem has not really been solved

Images