频率计数器在航天器信号频率测量中的适用性分析

从频率计数器的工作原理出发,分析了航天器测控通信中常用的调相信号、调频信号和相移键控信号的频率测量误差,给出了调相信号和调频信号的测量误差表达式。使用频率计数器对上述3种航天器信号进行了频率测量试验。理论分析和试验结果表明,频率计数器适用于航天器调相信号和调频信号的频率测量,不适用于相移键控信号的频率测量。在实际使用中,为保证测量精度,应根据被测信号的调制方式选择适当的测量方法。

Applicability Analysis of Frequency Counters in Frequency Measurement for Spacecraft Signals

The fundamental of frequency counters is introduced. The frequency measurement errors of phase-modulated signals, frequency-modulated signals and phase-shift keying signals applied in spacecraft TT＆C and communications are analyzed. The expressions of measurement errors of phase-modulated signals and frequency modulated signals are demonstrated. Frequency measurements of three types of spacecraft signals are made by experiments using frequency counters. Theoretical analysis and experimental results show that frequency counters are applicable to phase-modulated signals and frequency-modulated signals, but not applicable to phase-shift keying signals. In practical applications, the measurement method should be used properly according to modulation mode of the signal to be tested to ensure measurement accuracy.