The Rydberg atom cell nonlinear distortion in the demodulation amplitude modulation (AM) microwave is analyzed in this paper. We use the total harmonic distortion (THD) to quantitatively describe this nonlinear distortion. Simulation suggests that THD can be efficiently depressed by adjusting the coupling laser Rabi frequency and the AM microwave Rabi frequency static operation point. Numerical analysis shows that the THD can reach the minimum 0.14%, when the coupling laser Rabi frequency is 2×107（rad/s）, the AM microwave Rabi frequency static operation point is 2.5×104(rad/s) and the baseband microwave Rabi frequency is 2×103(rad/s).
The Rydberg atom cell nonlinear distortion in the demodulation amplitude modulation (AM) microwave is analyzed in this paper. We use the total harmonic distortion (THD) to quantitatively describe this nonlinear distortion. Simulation suggests that THD can be efficiently depressed by adjusting the coupling laser Rabi frequency and the AM microwave Rabi frequency static operation point. Numerical analysis shows that the THD can reach the minimum 0.14%, when the coupling laser Rabi frequency is 2×107（rad/s）, the AM microwave Rabi frequency static operation point is 2.5×104(rad/s) and the baseband microwave Rabi frequency is 2×103(rad/s).
Abstract The Rydberg atom-based receiver, as a novel type of antenna, demonstrates broad application prospects in the field of microwave communications. However, since Rydberg atomic receivers are nonlinear systems, mismatches between the parameters of the received amplitude modulation (AM) signals and the system’s linear workspace and demodulation operating points can cause severe distortion in the demodulated signals. To address this, the article proposes a method for determining the operational parameters based on the mean square error (MSE) and total harmonic distortion (THD) assessments and presents strategies for optimizing the system’s operational parameters focusing on linear response characteristics (LRC) and linear dynamic range (LDR). Specifically, we employ a method that minimizes the MSE to define the system’s linear workspace, thereby ensuring the system has a good LRC while maximizing the LDR. To ensure that the signal always operates within the linear workspace, an appropriate carrier amplitude is set as the demodulation operating point. By calculating the THD at different operating points, the LRC performance within different regions of the linear workspace is evaluated, and corresponding optimization strategies based on the range of signal strengths are proposed. Moreover, to more accurately restore the baseband signal, we establish a mapping relationship between the carrier Rabi frequency and the transmitted power of the probe light, and optimize the slope of the linear demodulation function to reduce the MSE to less than 0.8 × 10 −4 . Finally, based on these methods for determining the operational parameters, we explore the effects of different laser Rabi frequencies on the system performance, and provide optimization recommendations. This research provides robust support for the design of high-performance Rydberg atom-based AM receivers.
With the advancement of quantum physics and deeper exploration of atomic systems, the integration of atoms into communication systems has garnered significant attention. Among these efforts, the use of Rydberg atoms as a communication receiver has emerged as a prominent area of research. In this work, we introduce a new mathematical modeling approach to more accurately establish the input-output relationship of a Rydberg atomic receiver. We categorize this relationship into three segments: one linear region and two nonlinear regions, facilitating a comprehensive analysis of the nonlinear challenges associated with Rydberg atomic receiver. Our findings indicate that adjusting the Rabi oscillation frequency of the coupling laser can effectively extend the linear operating range of the receiver. Furthermore, focusing on complex quadrature amplitude modulation, we propose a digital nonlinear distortion compensation method specifically designed for Rydberg atomic receiver. This method demonstrates a significant improvement in performance, enhancing the demodulation bit error rate compared to conventional linearization techniques.
The Rydberg atom cell sensitivity on the incoherent detection microwave is analyzed as the probe laser noise is considered. First, the probe laser noise transfer characteristic is theoretically derived. Second, the minimum detectable microwave electric field intensity is obtained by simulation at different signal noise ratio of the input probe laser. These simulation results suggest that the microwave detection sensitivity of the Rydberg atom cell can be improved by two ways. One is to increase the input probe laser signal noise ratio. The other one is to decrease the Rabi frequency of the coupling laser. As the coupling Rabi frequencyΩc=2×108(rad/s)and the probe signal to noise ratio is 20.5dB, the minimum detectable microwave electric field intensity is1.976(μV/cm).
Rydberg sensors offer a unique approach to radio-frequency (rf) detection, leveraging the high sensitivity and quantum properties of highly excited atomic states to achieve performance levels beyond classical technologies. Nonlinear responses and distortion behavior in Rydberg atom receivers are critical to evaluating and establishing performance metrics and capabilities such as spur-free dynamic range and tolerance to unwanted interfering signals. We report here on the measurement and characterization of nonlinear behavior and spurious response of a Rydberg atomic heterodyne receiver. Single-tone and two-tone testing procedures are developed and implemented for measurement of harmonic and intermodulation distortion in Rydberg atomic receivers based on multiphoton Rydberg spectroscopy and radio-frequency heterodyne signal detection and demodulation in an atomic vapor. For a predetermined set of atomic receiver parameters and rf carrier wave in the super high frequency band near-resonant to a cesium Rydberg transition, we measure and characterize atomic receiver selectivity, bandwidth, roll-off, compression point (P1dB), second-order (IP2) and third-order (IP3) intercepts, and spur-free dynamic range. Receiver intermodulation distortion is characterized for the case of an interfering signal wave applied at two frequency offsets relative to the near-resonant reference local oscillator, Δ F / F = 10 − 4 at 6 dB and 10 − 6 at 22 dB single-tone bandwidths, respectively. We observe that under suitable operating conditions the atomic receiver can exhibit a suppression of harmonic and intermodulation distortion relative to that of classical receiver mixer amplifiers.
We have theoretically and experimentally studied the dispersive signal of the Rydberg atomic electromagnetically induced transparency (EIT) - Autler-Townes (AT) splitting spectra obtained using amplitude modulation of the microwave (MW) field. In addition to the two zero-crossing points, the dispersion signal has two positive maxima with an interval defined as the shoulder interval of the dispersion signal Δfsho. The relationship of MW field strength EMW and Δfsho are studied at the MW frequencies of 31.6 GHz, 22.1 GHz, and 9.2 GHz respectively. The results show that Δfsho can be used to character the much weaker EMW than the interval of two zero-crossing points Δfzeros and the traditional EIT-AT splitting interval Δfm, the minimum EMW measured by Δfsho is about 30 times smaller than that by Δfm. As an example, the minimum EMW at 9.2 GHz that can be characterized by Δfsho is 0.056 mV/cm, which is the minimum value characterized by frequency interval using vapour cell without adding any auxiliary fields. The proposed method can improve the weak limit and sensitivity of EMW measured by spectral frequency interval, which is important in the direct measurement of weak EMW.
Measurement sensitivity is crucial for the practical application of Rydberg atomic microwave superheterodyne receiver systems in communication, radar, and navigation. Based on laser-atom-microwave interaction mechanisms, the influence of laser powers and local-oscillator (LO) microwave field intensity on measurement sensitivity is systematically studied in this paper. Measurement sensitivity is analyzed through electromagnetically induced transparency (EIT) spectral characteristics, specifically EIT amplitude and full-width-half-maximum (FWHM),larger amplitudes and narrower FWHM indicate improved signal-to-noise ratios. For a 60D-state Rydberg atomic system with fixed probe and coupling laser beam waists (800 µm and 875 µm), optimal parameters are determined: probe laser power of 60 µW(Rabi frequency: 2π×7.02 MHz), coupling laser power of 40 mW (Rabi frequency: 2π×0.66 MHz), and LO microwave Rabi frequency of 2π×8.34 MHz. Experimental results demonstrate a 4.6 dB sensitivity enhancement, advancing from −137.5dBm/Hz to −142.1 dBm/Hz at 3.21 GHz microwave field. This improvement is attributed to precise alignment of laser-atom and microwave-atom interactions, bridging the gap toward quantum sensitivity limits.