Investigations of AM and PM noise in X-band devices

The authors report on measurements of phase modulation (PM) and amplitude modulation (AM) noise in a variety of amplifiers, dielectric resonator oscillator (DRO) sources, and mixers at 10.6 GHz. Two-channel measurement systems and cross-correlation analysis were used. In amplifiers there are at least two random noise processes that generate equal levels of PM and AM noise when the amplifier is in the linear operating range. The noise processes correspond to a flicker noise process and a white noise process. In the DRO sources these noise mechanisms are shown to be present in the active components and determine the AM and PM characteristics of the oscillator. A noise model for oscillators incorporating Leeson´s PM noise model and a model for AM noise in which the active components have two common random noise processes are proposed. The authors report AM noise levels of 140 dB below the PM levels at 1 Hz and typical noise floors of -169 dBc/Hz at 10 MHz. Noise residuals in mixers from three different companies are reported. Typical 1 Hz intercepts vary from -110 to -127 dBc/Hz. Noise floors are typically ~-173 dBc/Hz