RF Spectrum Analyzer for Pulsed Signals: Ultra-Wide Instantaneous Bandwidth, High Sensitivity, and High Time-Resolution

We report on the experimental demonstration of a multi-gigahertz bandwidth RF spectrum analyzer based on spectral hole burning in a 3 K-cooled rare-earth ion-doped crystal. We implemented the so-called “rainbow” architecture in which the optically carried spectral components of the incoming signal are angularly separated by the crystal, and are then acquired with a pixelated photo-detector. With this setup, we have been able to monitor and record the spectrum of complex microwave signals over an instantaneous bandwidth above 20 GHz, with a time resolution below 100 μs, 400 resolvable frequency components and a 100% probability of intercept. RF pulsed signals in the µs range are perfectly analyzed with this high time-resolved set-up. The best achievable sensitivity for pulsed signals is computed and compared with another spectral hole burning technique.