Phase noise reduction technique for pulsed TWT

Summary form only given. Reduction of the phase noise and intrapulse phase modulation of TWTA in radar transmitters becomes imperative because strongly reflected stationary clutter can mask signal of moving target. As Doppler radar is, in general, operated in fully saturated power, causing the phase noise to govern overall noise behavior. The phase non-linearity has it roots on beam velocity variation with time domain voltage jitter of HVPS (High Voltage Power Supply), which disturbs synchronism between beam and RF. The disrupted electrical phase length, in turn, induces spurious ripples and raise noise floor in phase noise spectral density plot. In this paper, we propose two novel methods that can be complementary to further reduce the phase noise. First method is phase locking loop phase noise reduction in that the proportional phase difference between input and output signal is detected and converted into dc control voltage by a double balanced mixer. This dc voltage is used to control an electronic phase shifter set to TWTA input, compensating the respective phase fluctuation. Second strategy focuses on reduction for HVPS voltage jitter. Throughout the high voltage divider, low power signal clippers, integrator and comparator, the only jitter signal is discriminated and utilized as a control signal in an electronic phase shifter. This method is superior to the present complicating noise filtering devices because of its simplicity and independence of RF circuitry. The system implementation of both methods is less expensive and more compact than conventional filtering devices for phase noise reduction.