What is it about?
Originally, antennas were designed and characterised in free space. It is now recognised that the performance can be significantly changed by the operating environment. For on-body communications, the body introduces frequency detuning and impedance mismatch; hence, antennas must be characterised in situ on the body. This article reviews the historical development of on-body antenna measurements, then describes a study into the effect of using standard measurement equipment (such as coaxial cables and a vector network analyser) on the observed performance, compared to measurements taken using an embedded system representing the end-use device.
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Why is it important?
This paper demonstrates that the use of standard measurement techniques can introduce a bias in the results, such that differences in performance will be experienced in a real device. Whilst not suggesting that traditional methods be replaced, it is believed that embedded system measurements offer a complementary characterisation option for device performance optimisation and final design verification. The results in the paper are indicative of the potential differences that can occur.
Perspectives
By comparing embedded antenna measurement techniques to direct antenna measurements using standard techniques, both with and without the embedded system present, typical errors in measured performance are quantified. Whilst these errors can be relatively small, it is often the case that designers must maximise performance from low-gain systems operating in relatively noisy environments. In such cases, even a few dB improvement can be the difference between unreliable and reliable real-world operation. Although focussed on body-centric communications applications, this will also be an issue for small systems in other areas, such as environmental sensors and the Internet of Things. This paper reminds the designer to consider the final end-use, both during design (simulations) and validation (measurements).
Dr Robert N Foster
University of Birmingham
Read the Original
This page is a summary of: On-Body Channel Measurement Using Wireless Sensors, IEEE Transactions on Antennas and Propagation, July 2012, Institute of Electrical & Electronics Engineers (IEEE),
DOI: 10.1109/tap.2012.2196933.
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