Study On Rf Front-end Technology For Dual-mode Mobile Phone

The wireless communication technology has been rapidly developing in various fields since the nineties of twentieth century, and it is gradually covering every aspects of individual life. The design and application of wireless terminal products are increasingly mature and forming large-scale. As the critical one of the wireless terminals, the mobile phone with single-mode is gradually unable to meet the practical needs. With the developments of wireless terminals, the dual-mode mobile phone with unique advantages which can work in two different standards and provide multiple services is increasingly predominating mobile market. The RF (radio frequency) front-end circuit of the phone, relating to the signal reception and transmission, has played a prominent role in the application of the products. The front-end performances directly determine the communication quality of the terminals and rational design determines whether the wireless devices can work normally and steadily. The high integration for RF front-end circuit and the antenna technology are demanded more compact and multi-band.This paper analyzes the basic structure of the wireless transceiver in detail and discusses the types of receivers and transmitters respectively. The structures of super-heterodyne, direct down-conversion, twice up-conversion, direct up-conversion and offset phase-locked loop are investigated. Combined with the solution of the dual-mode mobile phone RF front-end which offered by the chip manufacturers, the paper presents the GSM/WCDMA dual-mode RF frond-end circuit framework based on MTK platform. According to the requirements released by the 3GPP (Third Generation Partnership Project) for RF part specifications of GSM/WCDMA mobile phones, the chips for the RF circuit are selected and the performances of the chips are described in detail. Considering the EMC, decoupling and filtering problems in practical application, the schematic diagram of this dual-mode RF front-end circuit is proposed.In terms of the performance of mobile phone, a miniaturized and multi-band antenna is simulated and optimized, which covers GSM850/GSM900/DCS1800/PCS 1900/WCDMA2100 by coupling method. A new type of T-feed printed PIFA antenna, which achieves miniaturization is used in popular thin-profile mobile phone. The compact size of the antenna is only 15×33mm2, which achieve GSM850/GSM900/ DCS1800/PCS1900/WCDMA 2100 operation.Finally, the RF circuit of the dual-mode mobile phone is designed and tested. The problems such as the power issues of PA, the receiver sensitivity, TDD noise and the inner loop power control of WCDMA are analyzed in detail and resolved. The measured results indicate all specifications meet the requirements.