Design And Implementation Of HF Digital Receiver With High SNR

With the rapid development of wireless communications technology, short-wave band radio has become increasingly crowded, mutual interference has become increasingly serious. At the same time the wireless signal in the transmission process will be weak Rayleigh limit, which seriously affected the quality of the received signal; in this case, the traditional analog shortwave receiver has been difficult to meet the demand of users. Therefore, the premises of the existing channel how to receive high-quality short-wave signals becomes a very real problem. The digital realization of the receiver has become the focus of research in the field of wireless communications.This thesis has done as follows:(1) Describes the background and significance of this issue, and briefly introduces the basic principles used in this issue, and explains the structure of this paper. The basic design concept of this design is through the use of space diversity reception techniques and the best ratio-phase synthesis technology, traditional analog receiver for a reasonable digital transformation, which largely overcome the weakness of non-ideal Rayleigh channel and mutual interference between wireless signals and ultimately optimize the received signal to a large extent, improved the SNR of the received signal.(2) Determine the program of digital shortwave receiver. Carefully compare the various receivers'options, and analyzes their advantages and disadvantages. Finally give the solution of choosing a proper receiver. In the second chapter, by analyzing and comparing three different digital receiver realization of the program, chose IF broadband digital sampling structure as the design of digital implementations.(3) Complete the design and implement of a short-wave digital receiver hardware circuit and circuit board.And pay most attention to the analysis of the analog front-end circuit, AD/DA conversion circuit, FPGA circuit, and some of the key circuits. The original analog equipment running properly and the performance is good, so for the sustainable use of the original equipment, the design follows the original analog shortwave receiver as a signal receiver unit. The system includes four main modules short-wave receiver module, four gain control module and four analog-digital conversion modules, and FPGA synthesis module and several sub-set of analog conversion output module. This design is most characteristic of the original analog equipment in use, thus the premise of effective cost to the expected results.(4) The research projects focus on short-wave analog receiver with digital transformation of the design and spatial diversity synthesis FPGA. The fourth chapter elaborates the principles and the FPGA module approach and focuses on the spatial diversity to achieve the synthesis process.(5) Finally, under the laboratory conditions, simulate the HF digital receiver digital part of the circuit, and completed the short-wave digital receiver system test.