论文部分内容阅读
在调幅、单边带、调频三种通讯方式共存的双波段战术电台中,为兼顾各通信方式,使电路简化,第二中频就应取的较低。因调频信道为数模兼容,使得甚高频段通频带变宽,而普通的相位鉴频器和比例鉴频器在较低的中频情况下要做到解调范围宽,线性好,就十分困难,由此还会带来严重的侧峰响应,使整机频率特性恶化。针对这种情况,我们采用了脉冲计数式鉴频器(Pul se—Count—detecter),简写为PCD。本文就PCD的鉴频噪声门限与普通鉴频器门限进行比较,得出了提高门限的量值,并给出了PCD实际电路和设计要点。
In the dual-band tactical radio station where AM, SSB and FM are coexisting, in order to take account of each communication mode and simplify the circuit, the second IF should be taken low. Since the FM channel is digital-to-analog compatible, the passband of the VHF band is broadened. However, it is very difficult for the ordinary phase discriminator and proportional discriminator to have a wide demodulation range and good linearity at a lower intermediate frequency , Which will also bring a serious side of the peak response, the machine frequency characteristics of deterioration. In view of this situation, we use a pulse counting frequency discriminator (Pulse-Count-detecter), abbreviated as PCD. In this paper, the frequency discrimination threshold of PCD is compared with the common frequency discriminator threshold. The threshold value is obtained and the actual circuit and design points of PCD are given.