A Research And Design Of Automatic Gain Control Circuit In Low-IF GPS Receiver

Global Positioning System, called GPS for short, is used to accurately locate the object on the ground or in the air. As the extensive application of this locating technology, it brings huge changes in people's daily life.In the GPS receiver, the signal strength level will be different due to the multi-path fading and different positions. The AGC is therefore used to adjust the received signal to a rated strength level.The target of this thesis is devoted to the analysis and designs of an automatic gain control circuit for GPS receiver. First we present the fundamental of AGC circuit and analyses correlative circuit design. Then we choose appropriate circuit to finish the design. We use TSMC 0.25μm CMOS process and design an exponential variable gain amplifier, a high resolution high speed comparator, a differential charge pump, a low output impedance buffer and a high resolution reference. Under 2.5V power supply, the simulation results show that our circuit provides 54dB dynamic range, maximal 79dB voltage gain in IF circuits, [2.5M,26M] bandwidth and 3.375mW power consumption; the test results show that our circuit provides 54dB dynamic range, maximal 70dB voltage gain in IF circuits, [3.8M,25M] bandwidth and 5mW power consumption.