Design Of Complex Filter In GPS Receiver

With the rapid development of portable wireless transmission systems such as wireless networks, mobile phones, GPS and so on, people keep studying and improving the structure of various communications systems, and trying to integrate RF and IF function blocks in the same chip, so as to reduce the power consumption and the cost of a chip. In the communication system, filters play an important role of getting through the useful signal and rejecting signal interference. The main task in this paper is to design a frequency auto-tuning complex filter with programmable bandwidth and gain in SMIC CMOS 0.18μm process. The complex filter is used in GPS low-IF receiver.Firstly, this paper talks about the navigation system and image interference problem in receivers. Then the high integrated zero-IF and low-IF receiver architectures are introduced. Several image-rejection schemes are presented for GPS low-IF receivers.Then the paper describes the basic theories of filter function and the high order filter design. The specification of the complex filter used in GPS receivers and the signal flow graph design method is presented in the following section. The frequency response and stability of the integrator and the effect on filter performance due to the non-ideality of the integrator are analyzed. The layout design of the complex filter is proposed. The simulation results are given finally.