Photonic technology enables real-time calculation of radio signal
correlation
Light-based approach can be used to locate phones and other signal-
emitting devices, outperforms digital methods
Date:
March 24, 2022
Source:
Optica
Summary:
Researchers have developed a new analog photonic correlator that
can be used to locate an object transmitting a radio signal. They
demonstrated its ability to identify the location of a radio
frequency transmitter, working faster than other methods. The
device is considerably simpler than today's analog or digital
correlators and uses off-the-shelf telecommunications components
to process a wide range of radio frequency signals in cell phones,
signal jammers, and more.
FULL STORY ========================================================================== Researchers have developed a new analog photonic correlator that can be
used to locate an object transmitting a radio signal. Because the new correlator is faster than other methods and works with a wide range of
radio frequency signals, it could be useful for locating cell phones,
signal jammers or a variety of tracking tags.
==========================================================================
"The photonic architecture we developed uses no moving parts and
enables real- time signal processing," said Hugues Guillet de Chatellus
from Universite' Grenoble Alpes-CNRS in France. "Real-time processing
helps ensure there isn't any downtime, which is critical for defense applications, for example." In Optica, Optica Publishing Group's journal
for high-impact research, Guillet de Chatellus and colleagues describe
the new photonic correlator and demonstrate its ability to identify the location of a radio frequency transmitter. The device is considerably
simpler than today's analog or digital correlators and uses off-the-shelf telecommunications components.
"Many of today's radio signals have large bandwidths because they carry
a great deal of information," said Guillet de Chatellus. "Our photonic
approach offers a simple method for correlating signals with bandwidths
of up to a few GHz, a larger bandwidth than is available from commercial approaches based on purely digital techniques." Using light to calculate correlation The new photonic correlator can be used to compute what is
known as a cross- correlation function for two signals emitted from one
source and detected by two antennas. This measures the similarity of the signals as a function of the displacement of one signal relative to the
other and provides information about their relative delay, which can be
used to calculate the location of the signal's source.
==========================================================================
"The photonic architecture we developed enables real-time calculation of
the cross-correlation function of two input signals for about 200 values
of relative delay simultaneously," said Guillet de Chatellus. "This is
much higher than any photonic technique has been able to accomplish
so far." The correlator works like a photonic processor by using
fiber optic components to turn two radio-frequency signals into optical signals. Once the cross- correlation function is calculated, a detection
and processing chain enables it to be converted into a digital format.
The most critical component of the new system is a frequency shifting
loop, which can generate and manipulate a large number of time-shifted
replicas for an input signal. This simple photonic component has enabled
many recent innovations in microwave photonics.
"We've been developing frequency shifting loops for some time, and a
deep understanding of their architecture led us to apply them to this new application," said Guillet de Chatellus. "This work shows that photonics
can offer efficient alternatives to solutions that are based on digital electronics." Precision location After testing their new device using high-power simple signals, the researchers tested it with more complex
signals and then moved to signals propagating through free space and
received by a pair of antennas. The researchers were able to demonstrate localization of a radiofrequency transmitter with a precision close to 10 picoseconds for a 100-millisecond integration time. This means that the
system could locate an emitter with a precision of about 3 millimeters.
The new analog photonic correlator can also be used in astronomy to
cross- correlate signals coming from several telescopes to create high-resolution images. In the coming months, the researchers plan
to work on a demonstration experiment in which signals emitted from
the sun at around 10 GHz will be collected by two remote antennas and cross-correlated using the new photonic device to create an image of
the sun at radio-wavelength.
If these experiments are successful, this device could initiate infrared applications in astronomy facilities, such as the Very Large Telescope Interferometer in Chile, using heterodyne interferometry. Heterodyne interferometry has been used for radio-interferometry but was previously limited to narrow correlation bandwidths.
The researchers are also performing experiments to find out if the new
photonic correlator can be used to correlate three signals, which would
enable 3D localization of transmitters by triangulation. They also plan
further work to miniaturize and fully integrate the correlator.
========================================================================== Story Source: Materials provided by Optica. Note: Content may be edited
for style and length.
========================================================================== Journal Reference:
1. Hughes Guillet de Chatellus, Guillaume Bourdarot, Jean-Philippe
Berger.
Multi-delay photonic correlator for wideband RF signal processing.
Optica, 2022; DOI: 10.1364/OPTICA.442906 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220324104549.htm
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