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当本振正在扫描时,利用比例积分控制滤波器捕获带噪声信号锁相环路的能力,是根据这种系统的低频General Electric Electronic System Evaluator模型的经验决定的。本文研究自然频率和阻尼系数对线性环路(与中频信号受限幅的环路不同)的频率捕获性能的影响。此外,还讨论了中频信号受到严格限幅的环路,也讨论了对给足的信噪比在捕获概率等于或大于90％的情况下为使扫描率最大而设计的环路。对输出信号中的均方根相位抖动进行了测量,作为验证,预测相位抖动的标准分析的方法。研究端果如下: 1)阻尼系数在0.5～0.85的范围内有接近于最佳的捕获性能。 2)对给定的(S/N)_IF来说,虽然降低环路增益会减小相位抖动,但却降低了环路捕获和跟踪信号的总能力。 3)中频的“严格”限幅器能有效地作为增益控制,以提高环路的性能。 4)若给出(S/N)_IF和环路参数时,可用由试验结果推导出来的经验公式准确地预测捕获概率为90％的压控振荡器扫描率。
The ability to capture phase-locked loops with noisy signals using proportional-integral control filters when the LO is scanning is based on the experience of this system’s low-frequency General Electric Electronic System Evaluator model. This paper investigates the effect of natural frequency and damping factor on the frequency acquisition performance of a linear loop, which is different from a loop with a limited intermediate frequency signal. In addition, a loop in which the IF signal is severely limited is also discussed, and a loop designed to maximize the scan rate for a given SNR at a capture probability equal to or greater than 90% is also discussed. The rms phase jitter in the output signal was measured as a method of standard analysis to verify and predict phase jitter. The research results are as follows: 1) The damping coefficient is close to the best acquisition performance in the range of 0.5 ~ 0.85. 2) Reducing the loop gain reduces phase jitter for a given (S / N) _IF, but reduces the overall ability of the loop to capture and track the signal. 3) IF “strict” limiters can effectively be used as gain control to improve loop performance. 4) Given the (S / N) _IF and loop parameters, the empirical formula derived from the test results can be used to accurately predict the voltage-controlled oscillator sweep rate with a capture probability of 90%.