All-optical central-frequency-programmable and bandwidth-tailorable radar

Abstract

Radar has been widely used for military, security, and rescue purposes, and modern radar should be reconfigurable at multi-bands and have programmable central frequencies and considerable bandwidth agility. Microwave photonics or photonics-assisted radio-frequency technology is a unique solution to providing such capabilities. Here, we demonstrate an all-optical central-frequency-programmable and bandwidth-tailorable radar architecture that provides a coherent system and utilizes one mode-locked laser for both signal generation and reception. Heterodyning of two individually filtered optical pulses that are pre-chirped via wavelength-to-time mapping generates a wideband linearly chirped radar signal. The working bands can be flexibly tailored with the desired bandwidth at a user-preferred carrier frequency. Radar echoes are first modulated onto the pre-chirped optical pulse, which is also used for signal generation, and then stretched in time or compressed in frequency several fold based on the time-stretch principle. Thus, digitization is facilitated without loss of detection ability. We believe that our results demonstrate an innovative radar architecture with an ultra-high-range resolution.

Photonics-based real-time ultra-high-range-resolution radar with broadband signal generation and processing

“…In a previously reported photonics-based fully digital coherent radar 11 , the great potential of photonic technologies in future radar applications is demonstrated, but the signal processing in the sampling receiver is still a main limitation of the operation frequency and bandwidth. To down-convert the high-frequency RF signals, microwave photonic frequency conversion and time-stretched analog-to-digital conversion techniques have been proposed 12–15 , but it is still hard for a traditional radar receiver to process the down-converted baseband or intermediate frequency (IF)-band signals if a very large operation bandwidth is adopted.…”

Frequency-modulated microwave generation with feedback stabilization using an optically injected semiconductor laser

“…© 2016 Optical Society of America Photonic generation of microwave waveforms as a modulation on an optical carrier has been widely investigated due to the capabilities of low-loss delivery over optical fibers and the possibility of exceeding the bandwidth limitations of electronics [1][2][3][4][5]. Among the waveforms generated, frequency-modulated continuous-wave (FMCW) microwave signals in the form of sinusoids with time-varying microwave frequencies have received particular attention [6][7][8][9]. The instantaneous frequencies of an FMCW microwave signal measured at the source and the detector allow the determination of the round-trip delay of propagation.…”

“…The instantaneous frequencies of an FMCW microwave signal measured at the source and the detector allow the determination of the round-trip delay of propagation. Thus FMCW signals have been commonly utilized in ranging, imaging, and communication applications [6,9]. A number of approaches have been developed for generating photonic microwave FMCW signals.…”

Ultra-high range resolution demonstration of a photonics-based microwave radar using a high-repetition-rate mode-locked fiber laser

“…To take the advantages of photonics into radar systems, work was done with various architectures and schemes [10][11][12][13][14][15][16][17][18] . Heterodyning and dispersion techniques make significant use of the ultra-wide band of photonics, reaching very high resolutions [12] .…”

“…Its parameters are set as follows: the LFM frequency range is 0-8 GHz, the center frequency is 4 GHz, the period is 1 μs, and the duty-cycle ratio is 50%. A copy of the LFM pulse is directly recorded by the oscilloscope and utilized as the reference for the pulse-compression signal processing of the received echoes [13] . A single cycle of the LFM pulse that is generated by the AWG and recorded by the oscilloscope is depicted in Fig.…”