提出了一种基于光电振荡器结合电选频腔产生线性调频信号的方案,其中电选频腔由电放大器、电衰减器和移相器组成。通过调节电选频腔中移相器的偏置电压,利用光电振荡器输出信号与电选频腔输出信号间的频率牵引效应,能够产生中心频率为8.3 GHz的线性调频信号,频率变化范围约为550 MHz,调谐率约为5.5 MHz/μs,时间带宽积为5.5×10 4(带宽550 MHz,持续时间100 μs),其相位噪声由光电振荡器的相位噪声决定,其频率变化范围由移相器的偏置电压范围决定。与已有方法相比,该方案的系统结构较为简单,产生的线性调频信号具有较高的频谱纯度,相位噪声低至-116 dBc/Hz@10 kHz。

A scheme of linear frequency-modulated signal generation based on optoelectronic oscillator combined with electrical frequency-selected cavity is proposed. The electrical frequency-selected cavity is composed of the electrical amplifier, attenuator, and phase shifter. By adjusting the bias voltage of the phase shifter in the electrical frequency-selected cavity and utilizing the frequency pulling effect between the output signal of optoelectronic oscillator and the output signal of electrical frequency-selected cavity, the linear frequency-modulated signal with a central frequency of 8.3 GHz can be produced, for which the frequency range is as large as 550 MHz, the tuning rate reaches about 5.5 MHz/μs, and the time-bandwidth product is up to 5.5×10 ⁴ (bandwidth 550 MHz, duration 100 μs). Its phase noise depends on phase noise performance of the optoelectronic oscillator, and the frequency range depends on the bias voltage range of the phase shifter. Compared with current methods, the system structure is relatively simple. Linear frequency-modulated signal generated by this scheme has high spectral purity, and its low phase noise is -116 dBc/Hz@10 kHz.