基于单光路偏振复用的微波瞬时频率测量方案

Microwave Instantaneous Frequency Measurement Based on Single Lightpath Polarization Multiplexing

提出一种基于单光路偏振复用技术的微波瞬时频率测量方案。该方案仅需要一个双偏振-双驱动的马赫-曾德尔调制器来提供受激布里渊散射所需的泵浦光与探测光。与现有的双路布里渊散射方案相比,本方案结构简单,系统体积明显减小,泵浦光与探测光干涉稳定且可控,且系统的稳定性增强了。待测微波信号经过载波抑制双边带调制后作为泵浦光,扫频探测信号经过相位调制后作为探测光,利用受激布里渊散射效应实现从相位调制到强度调制的转换。通过建立扫描频率与输出光功率的映射关系,实现了微波信号瞬时频率测量。此外,建立了理论模型和仿真模型来分析泵浦光波长抖动、直流偏置点漂移、电移相器相位漂移,以及泵浦光、探测光偏振状态偏移对频率测量精度的影响。研究结果表明,该方案可以实现30 GHz以上微波信号的频率测量,且最大绝对测量误差不超过30 MHz,相对测量误差低于2%。该方法通过增大扫频探测信号的扫描范围和调制器的调制频率范围,可进一步扩展频率测量范围,在低成本、宽频谱的雷达侦测领域具有良好的应用前景。

A microwave instantaneous frequency measurement scheme based on single lightpath polarization multiplexing technology was proposed.This technique requires only a dual-polarization dual-drive Mach-Zehnder modulator to provide the pump light and probe light needed for stimulated Brillouin scattering.Compared with the previous dual-channel Brillouin scattering technique,the proposed technique offers the advantages of a simple structure,compression system volume,stable and controllable pump light and detection light interference,and improved system stability.The unknown microwave signal was modulated using carrier suppression double sideband modulation as the pump light,and the swept-frequency detection signal was phase modulated as the scanning detection light.Moreover,the conversion from phase modulation to intensity modulation was realized using the stimulated Brillouin scattering effect.The microwave signal instantaneous frequency was measured by establishing a mapping relationship between the scanning frequency and the output optical power.Theoretical and simulation models were established to study the influence of the pump light wavelength jitter,DC bias point drift,phase drift of electric phase shifter,and polarization state shift of pump light and probe light on frequency measurement accuracy.Research results show that the proposed scheme can measure the frequency of microwave signals above 30 GHz.Furthermore,the maximum absolute measurement error does not exceed 30 MHz,while the relative measurement error is less than 2%.The frequency measurement range can be increased by increasing the scanning range of the frequency sweep detection signal and the modulation frequency range of the modulator.The proposed scheme has the advantages of a compact structure,stable performance,and simple operation and has a wide application prospect in low-cost and wide-spectrum radar detection.