A Complex Filter With Adjusting I/Q Imbalance For GPS Receiver

With the rapid development of wireless communication systems, GPS,Wifi,Bluetooth technology has widespread in all aspects of life. Widely use of advanced technology not only is a microcosm of science, but also reflects the pursuit of convenience, efficiency and fine living desire of people. In the communication system, the filter is an indispensable module, which plays an important role in selecting the desired signal and suppressing interference signals. In this study, the main task is to design a complex filter for low-IF GPS receiver with adjusting I / Q imbalance and programming gain and bandwidth.Firstly, this paper talks about the structure of the navigation system and automatic gain control theory, followed by analyzing how the low-IF receiver architecture works, which leads to the problem of image disturbance and several image-rejection schemes for baseband signal. Then, filter theory are presented with details.Next, the flow of complex filter design under the specification is discussed. Three difficult problems are solved, including how to make tunable gain and bandwidth, how to conpensate the non-linearity of OPAMP, and how to correct the input signals'imbalance.Finally, the simulation result and analysis of comlex filter are proposed, which shows that the design of complex filter meets the requirement of GPS Low-IF receiver.