Ⅰ、引言早在1939年,参考文献(1)已介绍过将反馈式频率解调器(FMFB)用于减少无限幅器的鉴频器检波输出失真,但直到60年代才认为FMFB具有门限扩展能力。从那时起对其作为一种调频门限扩展设备的运用引起了许多争论,曾提出过大量的模型进行解释但看来没有在理论上能说得通的,也没有与实验结果完全符合的,尤其是在调制情况下。 I. INTRODUCTION As early as 1939, reference (1) introduced the use of a feedback frequency demodulator (FMFB) to reduce the detector output distortion of an infinite-amplitude discriminator, but it was not until the 1960s that the FMFB had a threshold spread ability. Since then, much controversy has arisen over its use as an FM threshold-extension device, a large number of models have been proposed for interpretation but it appears to have not been theoretically plausible nor fully consistent with the experimental results, Especially in the modulation case.