The RF Signal Analysis Of GSM Mobile Telephone And The Hardware Design On The Basis Of Digital Low IF Technology

At present, the main personal terminal product of the mobile communication market is a GSM mobile telephone in our country. But with the rapid growth of subscriber's quantity, the problems of GSM mobile telephone's RF system have become serious day by day. For instance: The sensitivity of receiving signal descended, The power of launch deviated from the normal working range, Bit error rate was high, The phase error was large, the area of radio frequency circuit was too large and so on.The article further investigated the process of RF's signal and the theory of RF circuit first. On the basis of such theories, this article compared and analyzed three kinds of GSM mobile telephone's RF system on principle and application. The analog components are the main part of Superheterodyne system, which has two times of frequency conversion. Superheterodyne system had a low level of integretion, and took a large area of PCB board. At the same time, Superheterodyne system aroused the image interference in the conversion of frequency. The zero intermediate RF system appeared recently. The level of integration made progress than that of Superheterodyne system. But the zero intermediate RF system can't avoid the DC offset, low frequency interference and non-linear interference. Be about to cope with such difficult problems, the digital low IF technology was applied to design the RF system. In this article, the design of hardware circuit with the technology of digital low intermediate frequency has following characteristics. On the module of key circuit, the chip adopted has already realized digital low intermediate frequency technology. In the module of power amplification, the design method that was adopted made the systematic integrated level improved, and put the module working efficiency of the circuit improved. Through analyzing the high-frequency characteristic of the primary component, it designed the circuit of antenna switch, this reduced the high frequency interference from baseband. In the match circuit of antenna, it took the optimal match method by analyzing the theory and simulating the circuit with software, which reduced the period of design. In the design of EMC, it analyzed the system with three respects of power management, baseband and RF, and tested the system.Finally, article expounded the weak point of signal analysis and the digital low intermediate frequency hardware design that must be improved.