Transmission Of Mixed-signal On Single-Frequency Carrier

In today’s society, with the faster and faster development of science and technology, a lot more electronic products are improving toward the digitization, Commercialization’s directions. And a growing number of civilian infrastructures are developing in the direction of low-cost, high-efficiency. Residential district video-voice intercom system is on such kind of trend. At present, most of the the video-voice intercom systems in the residential district on the market are in accordance with the shunt transmission mode, this kind of design greatly increased the cost of the system, because a large number of transmission lines caused a lot of cost, control signal lines and voice signal lines are usually transmitted by multiple lines. But transmission of mixed-signal on single-frequency carrier technology provides a feasible solution to solve this problem.This paper firstly introduced the theory of transmission of mixed-signal in a single product carrier, including ASK, PSK, QPSK, QAM, and clock recovery algorithm. Then described the hardware architecture of the entire system, as well as simulation based on this architecture, and then introduced the final implement and test.Due to the complexity of the system functions, in the research phase, we used SX25in advanced Xilinx’s Virtex-4family of the FPGA to achieve full system control and signal processing, HDL language is Verilog language.In the course of the study, the modulation of the signal implemented through a digital amplitude modulation modulation (ASK), digital phase modulation (PSK) and quadrature phase modulation (QPSK). And demodulation used coherent demodulation, envelope detection method. The signal multiplexing used TDM which has highly channel multiplexing efficiency, including code multiplexing technology, and the code word multiplexing. And the system clock synchronization adopted the synchronization method, for example, we used data flow edge detection and DLL to recover the system clock. There are RS232serial signal and audio stereo signals, the two signals are successfully modulated and transmitted, which originally need4transmission lines in the actual system to achieve this function, but now we only need one transmission line on which signals can be transmitted. And the error rate is almost zero.