Extending the Dynamic Range of a Spectrum Monitor Using Comparison Switching and Spectral Averaging

The dynamic range of a spectrum monitor can be extended by incoherently averaging the difference between the spectrum from the antenna and the spectrum from a comparison load. We show that it is often advantageous to increase the attenuation to the spectrum analyzer, thereby lowering the maximum signal strength at the mixer and subsequently compensating for the added noise by incoherent spectral averaging. We analyzed the case of a conventional heterodyne analyzer as well as an analyzer using direct analog-to-digital conversion (ADC) sampling.