Ultra-sensitive electromagnetic metrology

Start date 01 November 2021

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Client University of Cambridge
Investigator

Dr David Nugent
david.nugent@elucidare.co.uk

 


Abstract

Can astronomy and the science of detecting electromagnetic waves created at the dawn of the universe accelerate the commercialisation of modern wireless communication systems? This question is addressed by Elucidare in a translational research assignment with astrophysicists and engineers at the University of Cambridge.

Over the last decade, Cambridge researchers have built up expertise in the design, characterization and operation of the most sensitive electromagnetic sensors ever made. Astrophysicists and Quantum Sensor engineers specialize in such measurements, typically performed in environments much less controlled than commercial test facilities, such as radio telescopes in desert regions or space-based telescopes.

Projects such as the Square Kilometre Array telescope, where some of the faintest signals in the sky are measured against much brighter noise levels, and for which the Cambridge team and its collaborators have developed the low noise radio sensors, showcase the expertise at the University.

Elucidare welcomes feedback from scientists and engineers working in the field of electromagnetic metrology with regards the application of this world-leading research base to problems emerging from the development and proliferation of low-power wireless devices.

 Image credit: SKA ObservatoryImage credit:  SKA Observatory

 

Ultra low-noise and UWB receiver technology

The Cambridge team has developed ultra-wideband (UWB) low-noise receivers (noise floor ~ 0.2-0.4 dB) operating from ~30 MHz up to 2 GHz, alongside high resolution (~5-10 KHz) FPGA-based spectrometers, LPDA antennas and low noise amplifiers (LNAs).

These technologies could be incorporated into EM metrology settings such as anechoic chambers (e.g. beam measurements), reverberation chambers (e.g. noise figure measurements of active systems) and UAV-based outdoors measurements (e.g. cross-section/beam/emission measurements of very large radiating structures).

Alternatively, aspects of the amplifier, antenna and spectrometers designs could be applied with modification to a growing number of consumer and industrial UWB applications. In 2019, Apple added UWB with the U1 chip to the iPhone 11 and iPhone 11 Pro. Originally intended to allow the precise location of other U1‑equipped Apple devices, analysts expect UWB could extend to other functionalities, such as determining the orientation of the handset.

Image credit: NewAer

 

Calibrating sensors to levels of mK

Cambridge astrophysicists have developed techniques to calibrate radiometers across large bandwidths (Fmax/Fmin~5). The result is a smooth system response with RMS residual error of approximately 20 mK. These techniques can be applied to the calibration of metrology facilities, such as anechoic chambers, reverberation chambers and low noise measurement laboratories.

Proliferation of low-power wireless sensors and communication devices such as NB-IoT may spur demand for next-generation EM metrology, as manufacturers and standards bodies study the interplay between and within dense transceiver networks and background EM noises.

 

Image credit: Royal Academy of Engineering

 

Advanced analysis techniques to disentangle target signals from noise

Making sense of faint electromagnetic waves generated during the Epoch of Reionization around 13 billion years ago required the Cambridge researchers to develop advanced signal processing techniques. Methods such as Bayesian analysis allow signals to be extracted despite the presence of much brighter noise sources (~60 dB higher) and over wide bandwidths (Fmax/Fmin~5).

We envisage the adaptation of these techniques to the measurement of EM emissions well below the apparent environmental noise floor. Such methods may become increasingly useful when measuring microwave levels in anechoic and reverberation chambers as well as low-noise laboratories.

 

 

Full wave electromagnetic modelling tool for the resolution of Maxwell equations

Simulation software allows engineers to evaluate, optimise, and compare product designs by modelling real world events in a computer generated environment. Such tools are especially useful in RF design where the production and testing of prototypes is expensive and time consuming.

Optimised for very large antenna networks such as phased arrays and sensing networks, the algorithms developed by Cambridge and its collaborators is around 10,000 times faster than commercial simulators - without compromising accuracy. This means simulation runs can be completed in minutes compared to tens of hours - a huge productivity boost.

This tool can also tackle much larger problems due to the way in which data products are treated, e.g. up to thousands of antenna elements. This is especially suitable for radio and microwave systems such as radars.

We envisage this tool supporting measurements services in anechoic chambers, reverberation chambers and UAV facilities, as well as accelerating RF product development and testing

 

In situ characterisation of large radiating and receiving systems (e.g. radiotelescope beams) using UAVs to an accuracy of ~0.5 dB

The Cambridge team has developed a UAV-based measurement system capable of mapping the emitted field both in the near- and far-field of a large antenna systems and arrays. Proprietary near- to far-field transformation techniques enable the measurement of antennas installations many wavelengths in size.  

 

 

Documents available for download

SKALA, a log-periodic array antenna for the SKA-low instrument: design, simulations, tests and system considerations
SKA LFAA Station Design Report
A general Bayesian framework for foreground modelling and chromaticity correction for global 21 cm experiments download here
Understanding the HERA Phase I receiver system with simulations and its impact on the detectability of the EoR delay power spectrum download here
Array Element Coupling in Radio Interferometry I: A Semi-Analytic Approach
Plane-wave spectrum methods for the near-field characterization of very large structures using UAVs: The SKA radio telescope case download here