Digital Fm Exciter Audio Signal Processing Method

With the development of science and technology, people's demand for high quality broadcast is increasing. Because of its many outstanding advantages such as low linear distortion, no crosstalk, high fidelity and high signal to noise ratio, and its ability to support stereo broadcast and multicast, FM radio gains rapid development. FM exciter, as the core of the FM radio transmitter, directly determines the merits of the FM radio's performance. With the development of digital processing technology and direct digital frequency synthesis technology and new requirements for broadcasting, because of its low distortion, high signal to noise ratio, digital FM exciter is gradually replacing analog FM exciter. However, there are few of digital exciter manufacturers in China, the products are imported. Therefore, for the development of the FM radio and the entire broadcasting industry, to study digital exciter and to manufacture high-quality products of ours have great significance.This paper uses the digital signal processor (DSP) to dedign the digital FM exciter. First, the characteristics of the DSP, the development steps and the chip selection based on the selection rules is introduced; Second, on the basis of familiar with the analog audio sampling technology and digital audio signal format, the AIC23B audio codec chip is used to complete analog audio signal acquisition; for the collected signal, the focus is put on using the DSP to achieve filtering, compression, storage and audio related algorithms; After some basic processing of the audio signal, an interpolation is maked and then a cosine lookup table is designed to complete the synthesis of the composite stereo baseband signal in accordance with the national standard. Finally, on the basis of introducing the modulation techniques and the working principle of the direct digital frequency synthesizer (DDS), the focus is put on the FM program of using DSP to control DDS and using the logic analyzer and the oscilloscope to verify the accuracy of the results. At the end of this paper, it summarises the total works and some of the problems encountered in the subject, and makes a certain outlook on future work.