This paper audits FM demodulation using discriminator circuits, and the FM–AM conversion using a conventional single-tuned, double-tuned and staggered-tuned circuit is discussed. The demodulation capabilities of the double- and staggered-tuned circuits are audited in the time domain. It is observed that the conventional single- and double-tuned circuit outputs are highly distorted, in particular, the single-tuned circuit output is rich in second harmonics, and a balanced slope detection technique is proposed which reduces the output THD. A novel method of dynamically controlling the center frequency of the tuned circuit is proposed, and an excellent demodulation capability with a reduction in output THD by controlling the feedback loop gain is reported. This dynamically controlling action is applied to a conventional Foster–Seeley discriminator, and it is found that for higher values of feedback gain, the output THD decreases. It has been established that by judiciously controlling the center frequency of the tuned circuit, the effective modulation index has been reduced. The maximum permissible value of input modulation by the dynamic BPF has been derived. Experimental findings coupled with analytical results are presented and are shown to be in good agreement.

中文翻译：

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使用带通滤波器动态控制动作的 FM 解调

本文审核了使用鉴别器电路的 FM 解调，并讨论了使用传统单调谐、双调谐和交错调谐电路的 FM-AM 转换。双调谐和交错调谐电路的解调能力在时域中进行审核。观察到传统的单、双调谐电路输出失真度很大，特别是单调谐电路输出富含二次谐波，提出了一种平衡斜率检测技术，降低了输出THD。提出了一种动态控制调谐电路中心频率的新方法，并报告了通过控制反馈环路增益降低输出 THD 的出色解调能力。这种动态控制动作应用于传统的 Foster-Seeley 鉴别器，并且发现对于较高的反馈增益值，输出 THD 减小。已经确定，通过明智地控制调谐电路的中心频率，有效调制指数已经降低。已推导出动态 BPF 输入调制的最大允许值。实验结果与分析结果相结合，显示出良好的一致性。