Analysis on repeater jamming active cancellation for linear frequency modulated wave

A repeater jamming active cancellation method for linear frequency modulated (LFM) wave was proposed. Utilizing the coupling between time delay and frequency shift of matched filtering output, by phase and frequency modulating, the synthetizing output of cancellation and original wave can meet the cancellation conditions on time, amplitude and phase, consequently the filtering output decreases as well as the detection probability. Formulae for the output of the phase-only modulated wave and phase and frequency modulated wave were derived. Filtering output characteristics were analyzed theoretically. Simulation results show that, for the phase-only modulated wave, the cancellation effect is proportional to the product of repeating time delay and wave bandwidth, decrease of which resulting in a better cancellation effect but a higher demand on the accuracy of phase and amplitude controlling. For the phase and frequency modulated wave, the cancellation effect is decided by the division of repeating time delay and pulse width. Bandwidth of the wave has no influence on the cancellation effect. A wider bandwidth needs a higher accuracy of the frequency modulating.