Research-based Teaching System For Digital Broadcasting In The Fm-cdma Mode

The teaching broadcasting system generally exists in each campus in our country. It mainly serves for the foreign language teaching. The existing teaching broadcasting system adopts analog mode, which works between FM85-87MHz, it offers a set or several sets of foreign program in the range of 2MHz, but it can not meet the needs of different languages and different layers of students. Against this existing state, we put forward a new FM-CDMA mode based system of digital teaching broadcasting, which applies the technology of CDMA in broadcasting system, and it will not use the mode of traditional FDMA to divide channels but the mode of CDMA , in the range of 2MHz, we can send 32 sets of program signals by one transmitter.In this article, on the foundation of FM-CDMA system, we mainly do the profound analytical study on the technology of modulation and demodulation, spread spectrum and dispread spectrum and spectral structure of the output system. We get lots of test data and simulation graphs. The analysis of simulation result indicates that the CDMA system has much more superior performance on noise-immune; the continuous processing in the part of signal modulation can not improve the efficiency of spectrum in CDMA system; under the situation , making sure that the proximity of the reliability of information transmission to the unsmoothed system, the power of the transmission can decline to 90.5% of the unsmoothed system, the bandwidth of -50dB will decline to almost one half of the unsmoothed system in spread spectrum and dispread spectrum by using continuous WALSH codes. This method is good for decreasing the disruption to the approach wave band and increasing the efficiency of spectrum.