Measurement of AM noise in pulsed gallium arsenide avalanche diode oscillators

A novel technique has been developed for the measurement of amplitude modulated (AM) noise in pulsed oscillators. The same technique is also extended to pulsed amplifier AM noise measurements. Basically, a wide-band measuring system allows steady state conditions to be reached in a time less than the pulse duration. In practice this time has been less than 1 µsec. Such a system allows noise measurements to be made on devices which cannot be operated continuosly due to heat dissipation limitations. It also permits pulsed noise measurements in devices at higher current densities than would otherwise be possible if the device were only operated cw. Noise measurements have been performed on X-band pulsed silicon and gallium arsenide avalanche diode oscillators. When operated at current densities over 2000 amps/cm²the gallium arsenide avalanche diode oscillators were found to have AM noise as how as a klystron, 20 db less noise than silicon avalanche diode oscillators and 10 dg less noise than Gunn diode oscillators. The double sideband AM noise level of the gallium arsenide avalanche diode oscillators was found to be 150 db below the carrier measured 1.5 and 30 MHz from the carrier in a 100 Hz bandwidth.