The Design And Realization Of Short-wave Receiver Base On Software Defined Radio

With the continuous development of social scientific, technological level and economic, the signal is more and more crowded because of a significant increase of the short-wave radio communications equipment. The electromagnetic environment of short-wave radio communications is increasingly complex. Due to the short distance, when multiple radio work simultaneously, they will interfere with each other, and what’s even worse, they do not work because of the blocking of shortwave receivers. Therefore, the design of anti-noise, anti-jamming, anti-decay, anti-multipath by strong short-wave receiver has a very important significance.According to the introduction of the idea of software radio, the content of the paper is that design and achieve a shortwave receiver with strong anti-interference ability, good noise figure and the receiver is based on CNC high-frequency and intermediate frequency front-end circuit with high anti-interference ability. The basic idea of software radio is a common, standard, modular hardware platform based on software programming to achieve the various functions of the radio station, freed from the hardware-based, purpose-oriented radio station traditional design methods. Its purpose is to construct a common platform of open, standardized and modular, the working frequency band, modulation and demodulation type, data format, encryption mode, the communication protocol are completed by software, we use software to achieve the function of the mixing of analog circuits, filtering, modulation and demodulation. The application of software radio technology in the short-wave communication make the short-wave communication universal, automated, modular, combined with the high-frequency and intermediate frequency front-end signal processing circuit, making the design of short-wave receiver with software radio universal, flexible features, along with traditional analog receiver high anti-noise advantage, which is the basic idea of this project design.The specific content of the study of this subject is that, short-wave radio signals who received by antenna pass the front-end protection and CNC attenuator. Then track the selected frequency by the preselected tracking filter, to eliminate interference and noise out of band. After the gain controllable amplifier with low noise, then select frequency by preselected tracking filter again, the interference and noise are eliminated further. After mixed by local oscillator constituted by the direct digital frequency synthesizer3times, the1.5～30MHz signal is converted into the low-IF signal, then the low-IF signal is sent into DSP for band-pass filtering and digital demodulation algorithm processing followed by sampling by ADC, and finally, the signal is sent into DAC to recover the modulation signal.The shortwave receiver of this paper has high anti-interference, low noise characteristics of traditional receiver, and also has the universal, modular characteristics of software defined radio.The final test shows the indicators of the short-wave receiver meet the design requirements fully.