Analysis of image frequency interference in altimeter front-end receiver

A major problem of the superheterodyne receivers is their response to the undesired frequencies, such as harmonic, image frequency signal. In this paper, special attention is paid to the image frequency interference. In order to analysis the effect of the image frequency signal to the superheterodyne, a behavioural model of a superheterodyne receiver of altimeter is presented and its electromagnetic compatibility is analyzed from the aspects of spectrum and power under the condition of image frequency interference. According to the simulation results, the methods of EMC reinforcement are given. The performance of the improved receiver is simulated and analyzed under the same condition. And the results based on the reinforcement system further verify the effectiveness of the method and the receiver achieves a higher image rejection ration.