Adaptive Software Radio Receiver System
|Course||Circuits and Systems|
|Keywords||software radio electrically tunable filter VCO (voltage controlled oscillator) adaptive reception system digital quadrature demodulation|
The main ideas of software radio is to construct a general hardware platform which has the feature of open, standardization, modularization and Re-configurable. All of the functions such as operating frequency, modulation-demodulation type, data format, ciphering mode and communication protocol can be done with the software and every kind of wireless communication function with open architecture can be achieved by loading software. The bran-new design philosophy demands that the broad band modulus and ADC/DAC close to the antenna, and the functions of original wireless communication system can be digitized as much as possible, all of which achieved by the software. Not only higher request has been stated to microelectronic technology, but also the new Project of wireless communication system structure and digital signal processing algorithm has been taken because of the software radio.Along with the development of communications technology, the design and achievement of receiver trend to expand with high performance and high integration density. And it mainly develop as high-linearity large dynamic range, high sensitivity and high-resolution and so on in performance. Especially when it comes to the more and more complicated electromagnetic environment and the multiple change transmission signals, the existing receiving system shows incompetent for dealing with the messages. As a result people commence to search for a software radio system with self-adapting capacity. The radio owns the abilities of accommodating to working atmosphere and raising performance and efficiency by means of adaptive mode (No manpower intervention).In connection with afore-mentioned problems, the article research and offer a self-adapting receiving system proposal which base on software radio technology. The system owns self-adapting ability to signals and it can adaptively sets the receiving center frequency and bandwidth of the RF front-end preselected filter to those of input signal, in fact, it concludes pre-sorting and pre-filtering the input signals and eliminating signals which is useless to receiving system, and meanwhile automatic decreasing gain of the large signals as automatic increasing gain of small-signals, all of these do good to enhancing the dynamic range of the system and suppressing the undesired signal. The self-adapting receiver executing the signal filter of the system preceding stage and it greatly reduces the signal processing working pressure of back-end digitization receiving, the back-end signal processing nearly carry on the analysis of desired signal by which the processes signal time has been shortened greatly.The micro-comb line-electrically tunable filter is chosen to be front-end preselected filter in the system, after that it passes through preselected, enlarged and mixing with local oscillator, the variable local oscillator mixing is adopted in mixer circuit in order that the mixed signals ensure unified MF(Medium frequency) or allowable frequency coverage of A/D. Such receiving system makes the advantage of software radio higher degree of materialization, and it also to be some of the first exploration in terms of AT (Adaptive Technology) of software radio.