The Design Of The RF Receiver System In Terminal For TD-SCDMA Comprehensive Test Instrument

Wireless communication terminal integrated test instrument in the wirelesscommunication industry chain has a very important position, is a wirelesscommunication terminal researching, production and testing equipment of repairinstrument, but TD-SCDMA integrated test instrument has been always is a weak linkin the development of TD-SCDMA industry, once the TD terminal industrializationbottleneck. With the issuance of 3G licenses, 3G operators on the communicationsystem presents more technical requirements, to enhance the market competitivenessof TD, MBMS, HSUPA and HSPA + enhancement technology is the latest TDdevelopment inevitable trend, therefore, also has proposed new demands ofTD-SCDMA integrated test instrument.Along with the electronic communication equipment increases ceaselessly, spaceelectromagnetic environment is increasingly complex, between each of theelectromagnetic interference becomes more and more serious, which means that thereceived signal is subjected to electromagnetic interference is more and more strong,corresponding ground capable of receiving the signal becomes more and more weak,so how to improve the TD-SCDMA receiver to the frequency selectivity andsensitivity in the RF system design process is becoming increasingly importantresearch direction, to improve and enhance the receiver RF front-end circuit structureand performance, can greatly improve the frequency selectivity and sensitivity.Therefore, the receiver RF front-end circuit design and simulation study has veryimportant significance.Based on the national major special project TD-SCDMA Integrated TestInstrument Researching, the broadband RF signal receiving conducted in-depth study.The main study is on traditional superheterodyne receiver, make the radio frequencysignal to conversion to an intermediate frequency, to provide modulation signal digitalprocessing. Common receiver types include superheterodyne receiver, mirror frequencysuppression receiver, digital intermediate frequency receiver and direct conversionreceiver. Based on the requirements of various indexes into consideration, this paperuse a superheterodyne receiver of well band rejection , relatively stable performance.In order to achieve a high mirror frequency rejection, and on this basis, as far aspossible to achieve high out-band rejection, this paper selects two under frequencyconversion mode. In front of the preselected filter design, use the microstrip filter,which is low cost and stable performance. The final output is a 96MHz intermediatefrequency signal.The experimental results show that, the channel of the receiver sensitivity canreach 140dBm/Hz, can be said to reach a higher level, the bandwidth of1.8GHz-2.4GHz, covers all the 3 TD band. Out-of-band rejection is high, and receiverintermodulation performance is good, TD mobile phone transmit power is from -65dBm ~ 24dBm, RF performance can fully meet the comprehensive measurementinstrument test mobile phone transmit power requirements, and has good applicationand mrket prospect .