﻿ 微波通信用高稳定本振源的设计

# 微波通信用高稳定本振源的设计Design of High Stable Local Oscillator for Microwave Communication

Abstract: Optoelectronic oscillator (OEO) can be used as local oscillator for microwave communication system because of its ultra low phase noise. In order to solve the problem of poor stability of OEO, the feedback loop was used to control the working point of the electro-optic intensity modulator, and the pilot method was also applied to control the stability of the oscillating loop, so the long-term stability has been obviously improved. A low frequency pilot signal was introduced into the mi-crowave optical link and its phase deviation information was extracted, then came back to the OEO loop, and a good stable signal output was achieved. Finally, the Allen variance was about 2.7 × 10−12 in 1 s.

1. 引言

2. 微波光链路

Figure 1. Typical microwave optical link structure and its matching control circuit

3. 光电振荡器

3.1. 原理

$\begin{array}{l}{V}_{1}={A}_{1}\mathrm{cos}\left(\omega t+{\phi }_{1}\right)\\ {V}_{2}={A}_{2}\mathrm{cos}\left(\omega t+{\phi }_{2}+\Delta \phi \right)\end{array}$ , (1)

${V}_{1}$${V}_{2}$ 分别为反馈支路移相后支路信号； $\omega$ 为导频信号频率； ${\phi }_{1}$${\phi }_{2}$ 分别为两支路到达混频器前端信号的相位； $\Delta \phi$ 为OEO环路的相位波动。两支路信号混频后为

Figure 2. Optoelectronic oscillator and its pilot control circuit

${V}^{\prime }\left(t\right)=\frac{1}{2}{A}_{1}{A}_{2}\left[\mathrm{cos}\left(2\omega t+{\phi }_{1}+{\phi }_{2}+\Delta \phi \right)+\mathrm{cos}\left({\phi }_{1}-{\phi }_{2}-\Delta \phi \right)\right]$ . (2)

$V\left(t\right)=\frac{1}{2}{A}_{1}{A}_{2}\mathrm{cos}\left({\phi }_{1}-{\phi }_{2}-\Delta \phi \right)$ , (3)

$V\left(t\right)=±\frac{1}{2}{A}_{1}{A}_{2}\mathrm{sin}\Delta \phi$ . (4)

$V\left(t\right)={K}_{\phi }\Delta \phi$ .(5)

${K}_{\phi }$ 是鉴相因子，其值为 $±\text{0}\text{.5}{A}_{1}{A}_{2}$ 。从上式可以看出，延时波动引起的相位变化最终转换为电压信号，反馈给长环OEO的压控移相器，通过改变环路相位调节振荡信号频率，实现长环OEO的稳定性控制。一般而言，电光调制器与光电探测器均为宽带器件，微波放大器也易于实现宽带，基于上述条件，可采用低频探测信号来对微波光子链路的整体延时波动进行提取。

3.2. 实验

Figure 3. Long-term stability test results

4. 结论

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