A photonics method is proposed to generate a microwave linearly chirped signal with improved central frequency, doubling bandwidth, amplitude and phase modulation capability. In the scheme, a dual-polarization integrated modulator combined with an optical filter are utilized to generate an orthogonally polarized optical signal. Then, the optical signal is injected into a polarization modulator (PolM) to perform data modulation. By controlling the polarization state of the orthogonally polarized optical signal, amplitude or phase of the generated microwave linearly chirped signal will be changed according to the driving data sequence. The proposed scheme is verified by simulation. Linearly chirped signals with central frequency tuned from 14 to 29 GHz, bandwidth tuned from 4 to 10 GHz are generated. ASK linearly chirped signals with bit-rate tuned from 156.25 to 1250 Mbps are demonstrated. Generation of a PSK linearly chirped signal and its coherent demodulation are verified. Besides, 4ASK, 4PSK and QPSK linearly chirped waveforms are achieved, and time-bandwidth product improvement is confirmed. The proposed method features parameter tunability and modulation format agility, which can be potentially employed in radar and wireless covert communication systems.

提出了一种光子学方法来产生微波线性chi信号，该信号具有改善的中心频率，带宽加倍，幅度和相位调制能力。在该方案中，利用与光滤波器组合的双偏振集成调制器来生成正交偏振的光信号。然后，将光信号注入偏振调制器（PolM）中以执行数据调制。通过控制正交偏振光信号的偏振状态，所产生的微波线性chi信号的幅度或相位将根据驱动数据序列而改变。仿真结果验证了该方案的有效性。产生线性chi信号，中心频率从14到29 GHz调谐，带宽从4到10 GHz调谐。演示了ASK线性chi信号，其比特率从156.25 Mbps调谐到1250 Mbps。验证了PSK线性chi信号的产生及其相干解调。此外，获得了4ASK，4PSK和QPSK线性chi波形，并确认了时间带宽乘积的提高。所提出的方法具有参数可调谐性和调制格式敏捷性，可以在雷达和无线隐蔽通信系统中潜在地采用。