The Research And Implementation On Direct Conversion Receivers

With the rapid development of mobile communication, the mobile-phone is not only demanded to support basic voice service, but also support high-speed data service, multimedia application, global positioning system, Bluetooth and so on. Furthermore, the wireless terminal is required to be low cost, low power dissipation and high integration. Direct conversion receivers (DCR) reduce the image reject filter and IF filter, so they are excellent in cost, area and power dissipation. The DCR take on a large development potential. So people pay more and more attention to DCR. However, the effect of local oscillator leakage,DC offset,I/Q mismatch,flicker noise and even-order distortion restrict the performance improvement. Thereby it is necessary to take measures to overcome the shortcomings. With the progress of IC technology, the application of advanced disposal technique, the betterment of algorithmic, the DCR will have a wider foreground.The main parts of receivers are firstly introduced in the paper. And then four radio frequency topology structures are studied and compared in this paper, and the reasons for choosing DCR is expatiated. The design problems of DCR are stressed researched and the corresponding solution is also given. The total design block diagram is given. Choose suitable chips and construct hardware model according to system requirement, and then the system simulation is made basis on ADS. In the end, the hardware circuit of the receiving part and the phase locked loop is designed and the PCB of DCR is completed. The test result and next-step design advice is described.According to the test, the phase locked loop, which generates the local oscillator signal, works well. It is short in locking time, steady in frequency, high in amplitude. The receiver can work normally, the performance of which can achieve the design requirement.