The Design Of Stereo Encoder In FM Transmitter

Audio broadcasting emerged at the end of the 1930's. This appearance added a new dimension to media, allowing news and information to reach the world immediately, making the world a smaller place. Broadcasting has become an important tool in people getting information, so more and more people do studies about FM broadcasting to improve audio quality. From mono to stereo broadcasting, people are always striving to achieve a better sound. Transmission directly affects the sound quality, so it is important to make sure that the audio transmission is good. On the encoder board, the stereo encoder is the key to having a good transmission. This paper focuses on the very important stereo encoder.First, the structure of FM broadcasting and the basic concepts of the frequency modulation transmitter are introduced along with the place and function of the stereo encoder. Then, the paper looks at the principles of stereo encoding, analyzes the spectrum and bandwidth of the FM signal by Bessel function, and simulates the output of the base band signal by MATLAB. After that, the paper analyzes the following stereo encoders: Matrix encoder, DSM, Soft-switching encoder. The circuit of the soft-switching encoder is given, and conclusions are made about the encoder. There are two kinds of LPF to study because they affect the performance of the stereo encoder. As an IC product, its yield has to be considered. The paper addresses yield analysis in order to improve the work efficiency of the encoder board. Finally, the FMSTC23E02 stereo encoder is developed in the FM broadcasting transmitter. Good separation performance is achieved based on the technical specifications of GY/T 169-2001. The paper concludes by showing the future direction of study for the stereo encoder board.The fundamental theories of stereo guide frequency and models of the stereo encoder were used to develop this paper. The conclusions drawn by the paper are verified by practical circuit design and debugging.