Study On Automatic Gain Control Technology In Anti-Jamming Receiver

Automatic gain control (AGC) circuit is always to be designed to keep the input level of analog-to-digital converter (ADC) constant in electronic warfare so as to eliminate jamming influencing ADC and to avoid limiting distortion and loss of signal-noise-ratio (SNR). This dissertation focuses on the algorithm of digital control AGC system and its implementation in the navigation anti-jamming receiver. The technique studied has been successfully employed in certain national engineering model item. The major work is as following:In the first place, redefine the targets such as dynamic range, steady-state error according to the noise figure of receiver. Keep the dynamic range of AGC and the noise figure meet the demand of receivers by designing the amplifiers of RF circuits and the structure of AGC system.In the second place, the loss of SNR of ADC is discussed. The relation between loss of SNR and the power of input is analyzed in theory. The optimal power of input with the minimum loss of SNR is the important parameter of digital control AGC system.In the third place, the theory of adaptive filtering is put into designing the algorithm of digital control AGC system. The iterative algorithm of gain adjusting is put forward. And the parameters which subject to the characteristic of convergence, extra error, dynamic range are decided to keep the capability of anti-jamming receivers.In addition, the application of Newton iterative algorithm in the design of all digital AGC system in anti-jamming receiver is studied. The simple function of design is offered. The results of simulation indicate: the algorithm is suit to the demand of dynamic range and control precision.In the fourth place, aiming to the operations such as logarithm, division which are difficult to implement, the performance of digital controlled AGC system is studied which is made up of look-up table and shifting. The results of simulation and test prove: the measures of implement are right and fit applying in projects.