Nanosecond phase coherent pulse generation at 94GHz at kW power levels

Next generation millimetre wave radars and pulsed electron spin resonance (ESR) instruments require complex pulse sequences consisting of very short, high power pulses that are pulse-to-pulse phase coherent. We have previously demonstrated 200mW coherent pulses at 94GHz with pulse lengths as short as 110ps, and showed how they can be used to make high range resolution radar measurements. We now report results where a commercial extended interaction klystron amplifier (EIKA) is used to amplify these pulses to kW power levels for use in advanced pulse ESR instrumentation. The instantaneous bandwidth of the EIKA now limits the minimum pulse length, but we demonstrate 1kW peak power pulses down to 1.5ns, dropping to 0.8kW at Ins and 0.25kW at 800ps. We demonstrate that complex high power pulse sequences can be used in a mm-wave pulse ESR system, and also report on the level of broadband noise or "dark noise" from the amplifier (when there is no input signal), which can limit receiver sensitivity. We also detail the average power handling characteristics of various quasi-optical components.