一种模数兼容的调幅广播系统

An Compatible Analog and Digital AM Broadcasting System

给出一种复合调制系统,实现兼容模拟调幅(AM)广播的数字化传输。该系统发送端采用具有低旁瓣功率谱的MPPSK调制信号取代正弦载波对模拟音频广播信号进行幅度调制;接收端将所接收的复合调制信号分为两路:一路直接沿用现用收音机中的包络检波即可复现模拟音频信号,实现了向下兼容;另一路则经过冲击滤波后先乘以相干载波,利用频谱差异分离出数字信号,再进行相关匹配解调出发送数据。该系统对于现有模拟AM广播发送设备稍加改动,即可在现行的AM广播系统传输体制内,同时传输模拟音频与数据信号。

This paper presents a composite modulation system to realize the digitalized transmission which is compatible with the analogue amplitude modulation (AM) broadcast. At the transmitter of this system, the M-ary phase position keying (MPPSK) modulated signal with low sidelobe of power spectrum, is adopted to replace the sine carrier to bear the amplitude modulation by analogue au-dio. While at the receiver the composite modulated signal received is divided into two parts: one part directly follows the envelope detector used in current radio sets to reproduce the analogue audio and to achieve the backward compatibility;and the other part passes the signal through an impact filter and then multiplies its coherent carrier, where the spectral difference is utilized to separate the analog audio and the digital signal and the transmitted data are demodulated by the matched correlation. The system can transmit analogue audio and data signal simultaneously within the existing AM broadcasting transmission scheme, except for a slight modification to cur-rent analogue AM broadcasting transmitters.