A microwave photonics instantaneous frequency measurement receiver was conceived and practically demonstrated. The system is based on phase modulation inside a Sagnac loop and therefore needs no bias voltage, resulting in no DC bias drifts. The system provides a DC output whose amplitude is a function of input signal frequency, and thus no high-frequency photo-detector is required. Furthermore, the system exhibits a very good sensitivity without the aid of any sort of electrical noise cancellation techniques, such as lock-in amplification. This makes the system response faster, which would be another benefit for electronic warfare applications. Less than 6% measurement error was achieved over a 0.01–40 GHz frequency range for $-30\mathrm{dBm}$ RF level. Also, a 10% error was achieved at $-51\mathrm{dBm}$ RF power level.

中文翻译：

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基于Sagnac回路的微波光子瞬时频率测量接收机

构思并实际演示了微波光子瞬时频率测量接收机。该系统基于Sagnac环路内的相位调制，因此不需要偏置电压，因此不会产生DC偏置漂移。该系统提供一个直流输出，其幅度是输入信号频率的函数，因此不需要高频光电检测器。此外，该系统在没有任何类型的电噪声消除技术（例如锁定放大）的帮助下，显示出非常好的灵敏度。这使得系统响应更快，这将是电子战应用程序的另一个好处。在0.01–40 GHz频率范围内，对于$-30\mathrm{分贝}$射频电平。此外，在$-51\mathrm{分贝}$ 射频功率水平。