Photonic Radio-frequency Arbitrary Waveform Generation Research Articles

W-Band Photonic Pulse Compression Radar With Dual Transmission Mode Beamforming

Millimeter wave (MMW) sensing systems have potential for enhanced range and angular resolution in comparison to lower radio frequencies. This article employs photonic-assisted radio-frequency arbitrary waveform generation to implement a high-bandwidth multi-target MMW radar. The presented sensing system operates in the W-band using chirped RF signals, with spectra between 80 and 95 GHz at the 10 dB points. We implement sum- and difference-mode beamforming using a two element transmitter array to perform azimuth angle sensing in addition to target ranging. Photonics-based waveform generation with programmable optical pulse shapers provides for incorporation of approximately uniform phase shifts across the entire bandwidth, which in turn enables control of the far-field interference patterns of the broadband waveforms. Our approach has analogies with monopulse tracking radar techniques, in which target angle information is revealed through sum- and difference-mode processing of the receiving antennae, but with the dual-mode processing implemented at the transmitter side via photonic radio-frequency arbitrary waveform generation. Experiments with a single target demonstrate unambiguous sensing of target angle with an estimated root-mean-square error of 0.18 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> over a ±4 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> angular range. We also demonstrate independent sensing of the angles of two targets that are resolved in range.

Integrated Photonic Chip Enabled Simultaneous Multichannel Wideband Radio Frequency Spectrum Analyzer

Radio frequency (RF) spectrum analysis is an essential technique for monitoring signal quality in ultrahigh-speed optical transmission, broad bandwidth photonic RF arbitrary waveform generation, and for characterization of high repetition rate optical pulse sources. Whereas the intrinsic bandwidth of electronics limits its use for RF spectrum measurement of high-speed signals, a photonic approach based on ultrafast Kerr nonlinear effects can readily measure the RF spectrum of optical signals having a bandwidth beyond 1 THz. The majority of fiber-based or integrated photonic RF spectrum analyzers reported to date can monitor only one channel at a time. We demonstrate how to harness mode-selective excitation of nonlinear optical effects to perform simultaneous multichannel RF spectrum analysis using a single integrated silicon photonic device. This approach, which can be scaled to a higher number of channels, opens up a new degree of freedom for realizing multichannel signal characterization using a single integrated photonic device.