Design Of IF Filter With Image Rejection In GPS Receiver

Nowadays in China, the importance of IC industry in supporting and reinforcing domestic economy is becoming more and more widely appreciated, meanwhile recently it's also enjoying the prosperous bloom. The awareness of consolidating the foundation of Chinese IC industry and speeding the development of the industrial and academic research relating IC are commonly recognized. Currently, the research on wireless transceiver is a very popular subject. However, due to lag in initial start, the relevant technical situation in China is in still in the early stage, falling far behind from some advanced nations in the maturity of technological and industrial setup, which necessitates the urgency of filling the gap between home and abroad for us. As a branch of wireless transceiver technology, wireless location and navigation is a significant tendency, concerning the safety of national defense but also owning the favorable potential of civil applications. Therefore the topic of this paper is chosen as designing one of GPS receiver modules- IF active filter.The main content includes as follows: at first brief introduction on the fundamentals and theories of GPS RF receiver communication system, the current developing condition home and aboard will be put forward. Then a couple of key specifications in the RF front end will be introduced. After that, we will present in detail the theories on real filtering and complex filtering, compare the characteristics among different low pass filter prototypes, analyze the effects of circuit non-ideality on filtering performance, and investigate the mechanism of image interference while offering 2 feasible solutions. The 1st one will include thorough design process and simulation results, as well as detailed discussion. The 2nd one will cover the preliminary implementation and simulation statistics. In this paper the technology of 1P6M mixed signal SMIC0.18um process is adopted. With the technology, a 5th order Butterworth low pass filter, a 3-stage RC polyphase filter, and a complex bandpass filter are realized. The simulations manifest that for the 1st solution, the filter has cut off frequency at 7.8MHz, with the tuning range of 3MHz~20MHz. And the image rejection ration can achieve above 25dB. The equivalent output noise is within 200nV/sqrtHz, the IP3 in band can be dBm. The 2nd solution manages the performance of a complex bandpass filter, with the center frequency at 4M, and bandwidth of 2M.