Showing papers by "Robert M. Edwards published in 2015"

RF power density measurements for RF energy harvesting in automobile factories

Abstract: This paper presents RF power density measurements carried out at an automobile manufacturing plant in the UK. This measurement campaign was carried out in order to quantify the amount of ambient RF power available within the plant. Due to the location of the plant, low power density measurements were recorded in the base-station downlink. The dominant frequencies at the plant were GSM-1800 and 3G. Average input RF power density for horizontal and vertical polarizations showed few variations in amplitude compared to the maximum hold technique for the frequency band surveyed. The measurement campaign showed that at some locations at the plant, the input RF power density for 3G mobile transmit band was more than the base-station downlink.

A low profile PIFA antenna with a via-less square-ring artificial magnetic conductor at 5.8GHz

Abstract: A new low profile antenna comprised of a PIFA and an Artificial Magnetic Conductor (AMC) are presented. The PIFA antenna is placed at the edge of the AMC structure for bandwidth improvement. Use of a square-ring elementary element AMC without via is shown to maintain the PIFAs radiation efficiency with a low profile. The chosen AMC exhibits the required zero phase reflection coefficient for normally incident waves. Results suggest that additional directivity can be achieved for the combined PIFA/AMC system.

Human effect on twin antenna On-body for three diversity techniques at 2.4 GHz

Abstract: Since the user is generally in the near field On-body antennas are accepted as more complex to optimise than their free space counterparts. Use of the body as a platform for wearable electronics is a topical subject. Omnidirectional antennas are thought to be useful for antennas in body area networks. However, the desirable properties of omnidirectional radiation patterns close to humans are severely diminished due to the lossy load nature of biological matter and high levels of scattering due to shadowing and mismatch. To alleviate these problems two or more antennas can be used on the body. In this paper, two on body antennas are used with three different combination techniques in order to evaluate the diversity performance and then compared with their free space equivalents. Three diversity techniques are used - Selective, Maximal Ratio and Equal Gain. The frequency of operation was 2.4GHz.

Rohacell radomes for delicate antennas on the body at 2.4GHz

Abstract: This paper presents the use of two generic on-body antenna types, a probe and a magnetic dipole with and without a radome constructed of Rohacell. Its is shown that Rohacell minimally attenuates the electromagnetic signal transmitted or received by the antenna concluding to the cover being essentially transparent to radio waves at 2.4GHz and 5.8GHz. In on-body meaurements radomes can be used to protect the antenna surfaces from damage and protect nearby personnel from being accidentally struck by quickly rotating antennas. Performance of two on-body antennas is considered on and off the body by measurement and simulation. Results show that the Rohacell protection has negligible effect on the performance of the antenna systems regardless of loading by humans and polarity. This paper aims to enlighten use of Rohacell to protect antennas used for body centric experiments and experiments in body-centric settings.

User detection at the base station in a GSM 900 mobile phone system

Abstract: Typically mobile handsets are used in close proximity to the users head, hand and shoulder. The radio frequency energy received and produced by the handset interacts with biological tissue causing severe perturbations to the radio channel. Human tissue is both dispersive and lossy therefore both the frequency and amplitude of any wave interacting with a user either in the uplink or the downlink will be changed. Identification of the presence of humans can be achieved by comparisons between the channel impulse response with and without a human user. This paper presents measurements and analytical framework for the determination of human presence in a cellular communication system over the air channel comprising a human, a handset and base station. For this analysis the chosen bearer is GSM.