On-body communication channels are of increasing interest for a number of applications, such as medical-sensor networks, emergency-service workers, and personal communications. This paper describes investigations into channel characterization and antenna performance at 2.45 GHz. It is shown that significant channel fading occurs during normal activity, due primarily to the dynamic nature of the human body, but also due to multipath around the body and from scattering by the environment. This fading can be mitigated by the use of antenna diversity, and gains of up to 10 dB are obtained. Separation of the antenna's performance from the channel characteristics is difficult, but results show that for many channels, an antenna polarized normal to the body's surface gives the best path gain. Simulation and modeling present many challenges, particularly in terms of the problem's scale, and the need for accurate modeling of the body and its movement.

On-body propagation channel measurements using two microstrip patch antennas for various links are presented and statistically analyzed. The attenuation attributed to factors such as the body, head and clothing are: 19.2, 13.0, and 1.7 dB, respectively, when measurement performed in the anechoic chamber. Measured cumulative distribution function (CDF) of data in the chamber and lab fits to lognormal distribution with deviation factors comparable in both cases. The results demonstrate that the human body is a major shadowing contributor in body area network (BAN) radio systems. The performance of potential radio systems under the measured channel variations is also investigated. Excellent system performance is achievable with power levels as low as 0.01mW. These results support the significance of channel characterization and modelling in producing suitable wireless systems for ultra low power BANs

A novel ultrawideband (UWB) microstrip monopole antenna with reconfigurable multiband function is presented. Reconfigurability is achieved by using GaAs field effect transistor (FET) switches to connect multiple stubs of different lengths to the main feed line of the monopole. The antenna is compact and flexible in terms of the availability of different reconfiguration bands and, most importantly, the simple biasing of the GaAs FET switches will not have a severe effect on the antenna performance. Using GaAs FET switches did not degrade the antenna radiation patterns due to the simple biasing technique and the few external biasing components needed, besides these switches did not degrade the antenna gain and efficiency due to their low insertion loss and low on resistance. When the antenna was reconfigured from UWB to work into multiple frequency bands, the total peak gain improved by 20% compared to the UWB case. In addition, the total efficiency of the antenna has not been significantly reduced in any reconfigured band, whereas the out-of-band total efficiency is hugely reduced, which highlights the filtering role of the reconfiguration process. The total dc power consumption of the antenna switches is still very low (<; 33 μW), and this will lead to simple integration of the antenna in some portable communication systems or future cognitive radio front ends.

This paper presents the design, fabrication and performance evaluation of a flexible millimeter-wave (mm-wave) antenna array for the fifth generation (5G) wireless networks operating at Ka-band (26.5-40 GHz). The single element antenna is comprised of a coplanar-waveguide (CPW)-fed rectangular patch tapered at its sides with two vertically oriented slots. The ground is designed with L-shaped stubs to converge the dispersed radiation pattern for improving the directivity and gain. The antenna fabrication is accomplished by two advanced methods of laser-milling and inkjet printing on a thin film of flexible liquid crystal polymer (LCP). A novel and time-efficient method for post-printing sintering is also proposed in this work. The design is extended in a two-element array for the gain enhancement. Measurements have validated that the proposed antenna array exhibits a bandwidth of 26-40 GHz with a peak gain of 11.35 dBi at 35 GHz, and consistent high gain profile of above 9 dBi in the complete Ka-band. These features recommend the proposed antenna array as an efficient solution for integration in future flexible 5G front-ends and mm-wave wearable devices.

This paper presents transient characterization of ultrawideband (UWB) body-worn antennas and on-body radio propagation channels for body-centric wireless communications. A novel miniaturized CPW-fed tapered slot antenna is proposed and used for transient measurements of UWB radio channels for body area network (BAN) and personal area network (PAN) scenarios. Unlike conventional UWB CPW-fed antennas, the proposed antenna employs two diverging tapered slots to provide smooth and stable impedance matching. Fidelity analysis is applied to evaluate the time-domain behavior of body-worn antennas and it is found that average fidelity obtained is 88% and 86% for the conventional coplanar waveguide fed antenna and the tapered slot antenna, respectively. However, the tapered slot antenna shows a significant size reduction and hence is suited for body-centric wireless communications.

Given the trend towards a user-centric concept in mobile communications, body area networks have received increasing attention within the wireless personal area community. Researchers and designers have been investigating radio propagation characterisation and modelling owing to its importance in developing and designing efficient and reliable radio systems. The paper presents an experimental investigation of ultra-wideband (UWB) on-body radio propagation. Channel models with respect to large scale and delay analysis have been derived from measured parameters. Effects of different antenna types on channel behaviour are also demonstrated. Results and analyses highlight the consequences of changes in body postures and positions in addition to antenna orientations on the communication channels. Measurement data are also used in predicting the performance of potential UWB wireless systems and their applications in body-centric networks. It is indicated that bi-phase modulation for UWB body-centric networks performs better than pulse position modulation systems. The study also concludes that the use of hybrid antenna types for different on-body links will provide better system performance.