Research On Nonlinearity In Repeater Jamming System Of Satellite Communications

Satellite communications is more and more important in the future war, whether the enemy’s communication be interfered, will largely determine the victory or defeat of a local war. Several kinds of anti-interference techniques have been introduced in the third-generation of defense satellite communications system (DSCSIII). Such techniques possess high quality in anti-interference, which makes DSCSIII successfully deal with the conventional interfering methods.To interfere the enemy’s signal, repeater jamming system of satellite communications converse the frequency of the enemy’s signal received by the base station then amplify-and-forwards it to the enemy’s satellite. A mathematical model is established for the system in this thesis. The forms of the signals, especially the form of the interference signal transmitted from the base station, are analyzed. The emphasis of the analysis is put on the non-linear property of the high power amplifier (HPA) and the effect of the non-linearity of HPA to the performance of the interference signal. Simulate how the closed-loop gain, local oscillator frequency offset (local oscillator frequency deviation between the terrestrial and satellite oscillator), noise and other factors interfere the system when the HPA are non-linear. Simulation results show that with the increase of the loop gain, the interference effect first increases and then decreases; smaller the frequency offset, the better the interference effect; the higher the down link noise power is, the poorer the effect will be; while the up-link noise power goes high, the effect first increases and then decreases.