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The joint radar and communication (JRC) system providing both large-capacity transmission and high-resolution ranging will play a pivotal role in the next-generation wireless networks (e.g., 6G and beyond) and defense applications. Here, we propose and experimentally demonstrate a novel photonics-assisted millimeter-wave (mm-wave) JRC system with a multi-Gbit/s data rate for communication function and centimeter-level range resolution for radar function. The key is the design of the intermediate-frequency (IF) JRC signal through the angle modulation of the linear frequency modulation (LFM) radar carrier using orthogonal frequency division multiplexing (OFDM) communication signal, inspired by the idea of constant-envelope OFDM (CE-OFDM). This IF angle-modulated waveform facilitates the broadband photonic frequency (phase)-multiplying scheme to generate mm-wave JRC signal with multiplied instantaneous bandwidth and phase modulation index for high-resolution LFM radar and noise-robust CE-OFDM communication. It is with fixed low power-to-average power ratio to render robustness against the nonlinear distortions. In proof-of-concept experiments, a 60-GHz JRC signal with an instantaneous bandwidth over 10-GHz is synthesized through a CE-LFM-OFDM signal encoded with a 2-GBaud 16-QAM OFDM signal. Consequently, a 1.5-cm range resolution of two-dimension imaging and an 8-Gbit/s data rate are achieved for both radar and communication functions, respectively. Furthermore, the proposed JRC system is able to achieve higher radar range resolution and better anti-noise communication, when using higher-order photonic frequency multiplying.

In this paper, we propose a stable radio frequency(RF) transmission scheme for optical link based on Dual drive Mach-Zehnder modulator(DDMZM). By frequency mixing, the phase jitter of the output signal caused by environment variation has been automatically compensated. Different from other passive compensation schemes, the reference signal and the pre-compensation signal are modulated on one optical carrier by a DDMZM, and the crosstalk of two RF signals can be depressed by using dispersion compensation and adjusting the bias voltage of DDMZM, without multiple frequency multiplications and divisions. Meanwhile, the noises induced by Rayleigh scattering can be suppressed by using acousto-optic modulator. Our scheme is featured by single laser diode employed and no extra phase jitter induced by wavelength differences, with the advantages of simple structure and cost-effectiveness. In the experiment, we demonstrate 10 GHz RF signal stability transmission over 50 km single mode fiber, the phase jitter mean square error is 0.82 ps during 10 hours.

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