A General Group Delay Ripple Automated Test Method

Abstract

The invention relates to an automatic test method for general group delay ripple. A test signal source generates two paths of baseband signals, one path of baseband signal is sent to a digital oscilloscope to be directly sampled as a reference, the other path of baseband signal is used for frequency modulation on a high-frequency carrier, the frequency modulation wave is changed to intermediate frequency from variable frequency by a test spectrometer after passing through a satellite transponder and then is sampled by the digital oscilloscope to obtain group delay curve data to be tested in a frequency range; the obtained group delay curve data is fitted according to a least square method to obtain fitting curve data reflecting overall trend; and the two groups of curve data before and after fitting are compared, and the maximum difference value in an index frequency range is found out, namely group delay ripple. According to the method, the curve is fitted by the least square method, an approximate curve is taken from the minimum angle of total deviation, a rule is found out from a large number of given data, a curve is constructed to reflect the general trend of data points, the local fluctuation of the curve is eliminated, and thus, the group delay ripple reflecting global characteristic is obtained.

Description

technical field [0001] The invention is suitable for the field of spacecraft ground testing, especially for automatic testing of communication satellite transponder group delay ripple, and belongs to the technical field of radio frequency testing. Background technique [0002] Group delay is an important parameter to describe the phase-frequency characteristics of a transmission system. Group delay ripple describes the fluctuation and fluctuation of group delay, and is an important indicator to measure the phase linearity of a continuous signal passing through a transmission system. [0003] Group delay ripple not only determines the fluctuation of signal transmission delay generated by the system, but also is closely related to signal transmission distortion and has a great impact on signal transmission quality. It is a major technical indicator of the current satellite communication system. Once the group delay ripple characteristics of the system are not good, it will cau...

AI Technical Summary

Problems solved by technology

Once the group delay ripple characteristics of the system are not good, it will cause signal phase distortion, reduce the signal-to-noise ratio, and increase the bit error rate

[0004] The traditional communication satellite transponder channel group delay characteristic test uses the modulator to modulate the signal, after being forwarded by the satellite transponder and then demodulated by the demodulator, it is sent to the frequency discriminator for comparison with the reference signal, so as to obtain the group delay characteristic data, but did not analyze the fluctuations and ups and downs of the group delay curve data, so it is impossible to deeply understand the group delay ripple characteristics of the satellite transponder channel, so that it is impossible to fully understand the impact of the satellite transponder channel on the quality of the transmitted signal

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