Automating FM Noise Measurements

With the proliferation of spectrally pure RF sources the developers of RF test systems have been faced with the problem of verifying this spectral purity, particularly the FM-noise sideband power levels associated with these sources. The PLL discriminator is one possible solution; however, its major drawback is that is requires a frequency source with spectral purity characteristics which are better than the source to be measured. The delay-line discriminator technique is an alternate solution to the problem. The latter technique has been successfully implemented and integrated into an automatic test system; its success is measured not only by its demonstrated performance characteristics but also by its simplicity which ensures its reliability and ease of maintenance.