Research And Design Of A Fast AGC Circuit For TDD Communication

Receiver as the core of the wireless communication system, its performance will directly affect the quality of the communication, and even off. Many of the air wireless signal received by the antenna to the receiver, receiver use filter to check out useful signal, then by amplification, frequency conversion, filtering, amplitude adjustment, A/D conversion and so on into digital form, be handled by the digital terminal. In the process of wireless signal transmission, the transmission power and signal transmission distance is different, the signal propagation environment (such as rain attenuation, ground reflection, obstacle etc.) caused by different attenuation of signal, signal level range of receiver is great, especially in mobile communication, this situation is more prominent. At present, the received signal range is 0 dBm ?-120 dBm. In order to maintain the linearity and sensitivity of the receiving device in such large range of signal amplitude, ensure the reliability of results and the reduction of signal processing, the receiver will normally use automatic gain control (AGC) circuit, AGC control circuit are used in the IF circuit, according to the received signals of different sizes to adjust the gain in order to achieve the purpose of the intermediate frequency signal output.With the development of society, the requirement of signal transmission rate is higher and higher, the communication environment is more and more complex, so the performance requirements of the system to AGC circuit is also gradually increased. Not only requires dynamic range, but also requires a stable time, the loop output is stable, and the flatness is better, which makes people on the fast AGC circuit research more and more attention.This topic comes from the development of C band receiver module in a TDD communication system of the company ". The design of the IF AGC module is one of the important contents of the development project. In this paper, firstly introduce the existing AGC technology and its development process in communication system, and then introduce the basic composition, performance index, different types and their advantages and disadvantages. Based on practical application, in accordance with the requirements of the project, according to the design requirements of the receiver for TDD communication system, build a fast AGC design of a large dynamic range, through theoretical analysis and test application, verify the rationality and feasibility of the selected scheme, meet the design requirements, and the corresponding products in large company batch use.