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

Fangzheng Zhang,Shilong Pan,Qingshui Guo

doi:10.1038/s41598-017-14306-y

Fangzheng Zhang, Shilong Pan + Show 1 more

Open Access

https://doi.org/10.1038/s41598-017-14306-y

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Abstract

Real-time and high-resolution target detection is highly desirable in modern radar applications. Electronic techniques have encountered grave difficulties in the development of such radars, which strictly rely on a large instantaneous bandwidth. In this article, a photonics-based real-time high-range-resolution radar is proposed with optical generation and processing of broadband linear frequency modulation (LFM) signals. A broadband LFM signal is generated in the transmitter by photonic frequency quadrupling, and the received echo is de-chirped to a low frequency signal by photonic frequency mixing. The system can operate at a high frequency and a large bandwidth while enabling real-time processing by low-speed analog-to-digital conversion and digital signal processing. A conceptual radar is established. Real-time processing of an 8-GHz LFM signal is achieved with a sampling rate of 500 MSa/s. Accurate distance measurement is implemented with a maximum error of 4 mm within a range of ~3.5 meters. Detection of two targets is demonstrated with a range-resolution as high as 1.875 cm. We believe the proposed radar architecture is a reliable solution to overcome the limitations of current radar on operation bandwidth and processing speed, and it is hopefully to be used in future radars for real-time and high-resolution target detection and imaging.

Highlights

Real-time and high-resolution target detection and imaging is of great importance in civil and security applications such as capturing and tracking fast moving targets, which requires a radio-frequency (RF) radar to be operated at a high frequency and a wide bandwidth with real-time signal processing capability[1,2]
A continuous wave light from a laser diode is modulated by a dual-parallel Mach-Zehnder modulator (DPMZM) that is driven by a continuous-wave intermediate frequency (IF)-band linear frequency modulation (LFM) signal generated by a low-speed electrical signal generator
The DPMZM consists of two subMZMs (MZM-a and MZM-b), and each sub-MZM is embedded in one arm of the parent MZM (MZM-c)

Summary

Introduction

Real-time and high-resolution target detection and imaging is of great importance in civil and security applications such as capturing and tracking fast moving targets, which requires a radio-frequency (RF) radar to be operated at a high frequency and a wide bandwidth with real-time signal processing capability[1,2]. This requirement creates great challenges to the state-of-the-art electronics. We propose and demonstrate a photonics-based real-time high-range-resolution radar incorporating optical generation and processing of broadband LFM signals. Real-time radar detection with a very high range resolution can be realized

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