Researchers have created a novel analogue photonic correlator that may be used to locate an object transmitting a radio signal. Because it is faster than current systems and operates with a wide spectrum of radio frequency signals, the new correlator could be useful for identifying cell phones, signal jammers, or a variety of tracking tags.
Hugues Guillet de Chatellus of the Université Grenoble Alpes-CNRS in France said, "We designed a photonic architecture that has no moving parts and allows for real-time signal processing." "Real-time processing eliminates downtime, which is critical in some applications, such as defence."
In Optica, the Optica Publishing Group's journal for high-impact research, Guillet de Chatellus and colleagues explain the novel photonic correlator and demonstrate its ability to locate the location of a radio frequency emitter. The gadget is made out of commercially available telecommunications components and is significantly simpler than today's analogue or digital correlators.
Guillet de Chatellus noted, "Today's radio signals have wide bandwidths because they contain a lot of data." "Our photonic approach provides a straightforward mechanism for correlating signals with bandwidths of up to a few GHz, much beyond commercial solutions based only on digital approaches."
Using light to calculate correlations
A cross-correlation function may be calculated for two signals originating from a single source and detected by two antennas using the innovative photonic correlator. This calculates the location of the signal's source based on the similarity of the signals as a function of their relative displacement and provides information about their relative delay. Guillet de Chatellus noted, "Today's radio signals have wide bandwidths because they contain a lot of data." "Our photonic approach provides a straightforward mechanism for correlating signals with bandwidths of up to a few GHz, much beyond commercial solutions based only on digital approaches."
The correlator works similarly to a photonic processor, turning two radio-frequency impulses into optical signals using fibre optic components. A detection and processing chain can be used to convert the cross-correlation function into a digital format once it has been determined.
The most essential component of the new system is a frequency shifting loop, which can generate and operate many time-shifted replicas for an input signal. This little photonic component has enabled several recent microwave photonic breakthroughs.
exact placement
The researchers began by testing their new device with high-power simple signals, then progressed to more intricate signals, and finally to signals travelling across free space and received by a pair of antennas. The researchers were able to demonstrate RF emitter localisation with precision close to 10 picoseconds during a 100-millisecond integration time. This means that the system may pinpoint an emitter's exact location to within 3 centimetres.
By cross-correlating signals from multiple observatories, the innovative analogue photonic correlator can be used in astronomy to create high-resolution images. In the coming months, the researchers intend to complete a demonstration experiment in which signals emitted by the sun at around 10 GHz are collected by two remote antennas and cross-correlated with the novel photonic device to create a radio-wavelength image of the sun.
If the testing go well, this technology might be utilised to begin infrared applications in astronomy facilities that utilise heterodyne interferometry, such as Chile's Very Large Telescope Interferometer. Heterodyne interferometry, which was formerly limited to tiny correlation bandwidths, has typically been used in radio interferometry.
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