Estimation of Break-Lock Conditions for Effective Jamming in Missile Borne Monopulse Receivers

–Missile borne Monopulse receivers invariably track the target in three domains, namely frequency, range and angle. For effective jamming of these receivers, it is essential that breaking of the track should be achieved in at least two domains. In frequency domain, so long as the monopulse receiver locks onto the radar echo frequency, the radar tracks the target. When there is a disturbance introduced either in form of deliberate noise or repeat jamming, the receiver loses the lock to the target and is misguided. In this paper, the monopulse receiver with third order PLL (Phase Locked Loop) is designed and the performance of the receiver is analyzed when sinusoidal CW (Continuous Wave) radar echo signal along with sinusoidal jammer signal is applied to the receiver. In addition, when FM (Frequency Modulation) CW jammer signal along with the radar echo signal is injected into the receiver, the value of modulation index for which break-lock occurs for different values of modulating signal voltage is estimated and an empirical relation is also obtained. The mathematical model for FM CW radar receiver is developed and implemented using Visual System Simulator. The model includes the generation of radar echo and jammer signal at the receiver input to achieve effective jamming. The effectiveness of noise jamming is also studied by injecting phase noise and White Gaussian noise signal into the receiver and break-lock condition of the receiver is also reported. It is shown that break-lock in the receiver occurs when the FM modulation index (Kf) exceeds 4x10 6 without exception with the carrier signal operating at40 MHz and when the modulating signal amplitude is 5 mV. Keywords––Monopulse, Radar echo, Repeat jamming.