Rydberg RF Receiver Operation to Track RF Signal Fading and Frequency Drift

Significant progress has been made in recent years demonstrating an all-optical high sensitivity Radio Frequency (RF) sensor exploiting the Electromagnetically Induced Transparency (EIT) effect in an atomic vapor. Rydberg RF sensors have previously been shown to exhibit excellent lab-based performance in measuring electric field properties. As a commercial network operator we wish to exploit these capabilities to produce a rugged high-sensitivity receiver for 5G signals, so we seek simple planning rules applicable to readily available low cost components. We present a simple analytic model for the operation of a sensitive Rydberg RF receiver to predict the optical modulation in response to an RF signal. We focus on maximizing the contrast in the optical response to a modulated RF signal rather than to a constant RF field. We show that the optical modulation depth can be maximized using an optimum coupling intensity. The optical modulation depth drops off rapidly as the RF source is detuned away from resonance. By detuning the coupling frequency to compensate for the RF detuning we demonstrate that the useful RF bandwidth of the receiver can be significantly extended. We measure this variation in optical response using a Rubidium vapor at a 15 GHz RF carrier frequency. Using readily available optical components we obtain good agreement with our model. This convenient analytic approach will simplify the design and operation of Rydberg RF receivers as sensitive components in future 5G mobile communications, particularly for the power-limited uplink from mobile device to base-station.