1,994 research outputs found
A 2.4-GHz low power polar transmitter for wireless body area network applications
A 2.4GHz low power polar transmitter is proposed in this paper. A dynamic biasing circuit, controlled by a digital envelope signal, is used as a direct digital-to-RF envelope converter. It effectively linearizes the input-output characteristic of the overdriven cascode class-C power amplifier used as the output stage, by dynamically adjusting the bias voltage of the cascode transistor. An equivalent baseband model of the transmitter is presented and used to optimize system parameters and give initial assessment of the achievable performance in terms of efficiency and linearity. Based on these simulations, parameters for transistor-level implementation of the bias circuit are derived. The transmitter is designed in a 65nm CMOS technology. The post layout simulations indicate that the transmitter successfully meets the requirements of the IEEE 802.15.6 standard for wireless body area networks. The simulated amplifier consumes 4.75mA from a 1.2V supply while delivering 1.45dBm of output power with a peak efficiency of 24%. The entire transmitter, including the PLL, consumes 7.5mA
Flexible dual-diversity wearable wireless node integrated on a dual-polarised textile patch antenna
A new textile wearable wireless node, for operation in the 2.45 GHz industrial, scientific and medical (ISM) band, is proposed. It consists of a dual-polarised textile patch antenna with integrated microcontroller, sensor, memory and transceiver with receive diversity. Integrated into a garment, the flexible unit may serve for fall detection, as well as for patient or rescue-worker monitoring. Fragile and lossy interconnections are eliminated. They are replaced by very short radiofrequency signal paths in the antenna feed plane, reducing electromagnetic compatibility and signal integrity problems. The compact and flexible module combines sensing and wireless channel monitoring functionality with reliable and energy-efficient off-body wireless communication capability, by fully exploiting dual polarisation diversity. By integrating a battery, a fully autonomous and flexible system is obtained. This novel textile wireless node was validated, both in flat and bent state, in the anechoic chamber, assessing the characteristics of the integrated system in free-space conditions. Moreover, its performance was verified in various real-world conditions, integrated into a firefighter garment, and used as an autonomous body-centric measurement device
Wireless body sensor networks for health-monitoring applications
This is an author-created, un-copyedited version of an article accepted for publication in
Physiological Measurement. The publisher is
not responsible for any errors or omissions in this version of the manuscript or any version
derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/0967-3334/29/11/R01
In situ characterization of two wireless transmission schemes for ingestible capsules
We report the experimental in situ characterization of 30-40 MHz and 868 MHz wireless transmission schemes for ingestible capsules, in porcine carcasses. This includes a detailed study of the performance of a magnetically coupled near-field very high-frequency (VHF) transmission scheme that requires only one eighth of the volume and one quarter of the power consumption of existing 868-MHz solutions. Our in situ measurements tested the performance of four different capsules specially constructed for this study (two variants of each transmission scheme), in two scenarios. One mimicked the performance of a body-worn receiving coil, while the other allowed the characterization of the direction-dependent signal attenuation due to losses in the surrounding tissue. We found that the magnetically coupled near-field VHF telemetry scheme presents an attractive option for future, miniturized ingestible capsules for medical applications
Antenna and radio channel characterisation for low‐power personal and body area networks
PhDThe continuous miniaturisation of sensors, as well as the progression in wearable electronics,
embedded software, digital signal processing and biomedical technologies, have led to new usercentric
networks, where devices can be carried in the user’s pockets, attached to the user’s body.
Body-centric wireless communications (BCWCs) is a central point in the development of fourth
generation mobile communications. Body-centric wireless networks take their place within the
personal area networks, body area networks and sensor networks which are all emerging
technologies that have a wide range of applications (such as, healthcare, entertainment,
surveillance, emergency, sports and military). The major difference between BCWC and
conventional wireless systems is the radio channels over which the communication takes place.
The human body is a hostile environment from a radio propagation perspective and it is therefore
important to understand and characterise the effects of the human body on the antenna elements,
the radio channel parameters and, hence, system performance. This thesis focuses on the study of
body-worn antennas and on-body radio propagation channels.
The performance parameters of five different narrowband (2.45 GHz) and four UWB (3.1-
10.6 GHz) body-worn antennas in the presence of human body are investigated and compared.
This was performed through a combination of numerical simulations and measurement
campaigns. Parametric studies and statistical analysis, addressing the human body effects on the
performance parameters of different types of narrowband and UWB antennas have been
presented. The aim of this study is to understand the human body effects on the antenna
parameters and specify the suitable antenna in BCWCs at both 2.45 GHz and UWB frequencies.
Extensive experimental investigations are carried out to study the effects of various antenna
types on the on-body radio propagation channels as well. Results and analysis emphasize the best
body-worn antenna for reliable and power-efficient on-body communications. Based on the
results and analysis, a novel dual-band and dual-mode antenna is proposed for power-efficient
and reliable on-body and off-body communications. The on-body performance of the DBDM
antenna at 2.45 GHz is compared with other five narrowband antennas. Based on the results and
analysis of six narrowband and four UWB antennas, antenna specifications and design guidelines
are provided that will help in selecting the best body-worn antenna for both narrowband and
UWB systems to be applied in body-centric wireless networks (BCWNs). A comparison between
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the narrowband and UWB antenna parameters are also provided. At the end of the thesis, the
subject-specificity of the on-body radio propagation channel at 2.45 GHz and 3-10 GHz was
experimentally investigated by considering eight real human test subjects of different shapes,
heights and sizes. The subject-specificity of the on-body radio propagation channels was
compared between the narrowband and UWB systems as well
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Assessment of a low-profile planar antenna for a wireless sensor network monitoring the local water distribution network
This paper presents an assessment on the suitability of a low-profi le planar antenna for a
Wireless Sensor Network (WSN) application monitoring the water supply at Fire Hydrants
(FHs). The antenna must have a low pro le so that it can be mounted on the FH lid; it must
have an omnidirectional radiation pattern so that it can communicate with base stations at
low elevations; and it must operate in the 2.4 GHz Industrial, Scienti c and Medical (ISM)
band. Measurements show that for the majority of the 2.4 GHz ISM band, the antenna has
a return loss of at least -10 dB and e ciency greater than 60 %.
For the FH WSN assessment, the antenna was deployed as a transmitter mounted on
the FH lid above the underground FH chamber and a vertically polarised monopole antenna
mounted on a mast at various speci ed heights above ground level was used to measure the
received power as a function of distance. The path loss results were compared with those from
a previous deployment, where the FH antenna was located in the FH chamber, and it is found
that using the low-pro le antenna reduced the path loss by at least 10 dB over the measured
transmitter and receiver separation.This paper is a postprint of a paper submitted to and accepted for publication in IET Wireless Sensor Systems and is subject to Institution of Engineering and Technology Copyright. The final version is available the IET Digital Library
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