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Photonic radar is a technique by which
Photonic radar is a technique by which radar
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
may be produced and analysed with the help of photonics
Photonics is a branch of optics that involves the application of generation, detection, and manipulation of light in form of photons through emission, transmission, modulation, signal processing, switching, amplification, and sensing. Though ...
rather than traditional RF engineering
Radio-frequency (RF) engineering is a subset of electronic engineering involving the application of transmission line, waveguide, antenna and electromagnetic field principles to the design and application of devices that produce or use signals w ...
techniques. The frequency of the radar is still in the RF, but lasers are used to create and analyse the RF signals with high precision.
The USA, China, and Russia have research programs to equip fighter aircraft
Fighter aircraft are fixed-wing military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air superiority of the battlespace. Domination of the airspace above a battlefield ...
with photonic radar. The potential benefits are longer range of detection, better position sensing, and 3D model target reconstruction.
In one study, a test device could resolve objects as small as 3 x 4 cm (1.2 x 1.6 in), much smaller than traditional radar.
Overview of operation
A laser diode is used to generate an optical signal that is modulated by a linearly-chirp
A chirp is a signal in which the frequency increases (''up-chirp'') or decreases (''down-chirp'') with time. In some sources, the term ''chirp'' is used interchangeably with sweep signal. It is commonly applied to sonar, radar, and laser system ...
ed low frequency signal. This modulated optical signal is then split, with one part immediately converted to an electronic signal at 4 times the frequency of the original modulating signal. This waveform is then amplified, emitted via a standard antenna, and then received again via another standard antenna. The second half of the modulated optical signal is further modulated by the reflected signal, and then converted to an electronic signal. This electronic signal is sent through a low-pass filter and finally digitized via an analog-to-digital converter. The resulting digital waveform can be processed to recover the delay between the transmitted and reflected signal, and thus the distance to the target. The entire system may be operated in real-time to allow high-speed target acquisition.
Applications
Novel potential applications include non-invasive patient vital sign monitoring using a photonic chip small enough to include in a phone.References
{{reflist Photonics