P. McEvoy

Mobile phone ‘talk-mode’ signal delays EEG-determined sleep onset

Mobile phones signals are pulse-modulated microwaves, and EEG studies suggest that the extremely low-frequency (ELF) pulse modulation has sleep effects. However, talk, listen and standby modes differ in the ELF (2, 8, and 217Hz) spectral components and specific absorption rates, but no sleep study has differentiated these modes. We used a GSM900 mobile phone controlled by a base-station simulator and a test SIM card to simulate these three specific modes, transmitted at 12.5% (23dBm) of maximum power. At weekly intervals, 10 healthy young adults, sleep restricted to 6h, were randomly and single-blind exposed to one of: talk, listen, standby and sham (nil signal) modes, for 30 min, at 13:30 h, whilst lying in a sound-proof, lit bedroom, with a thermally insulated silent phone beside the right ear. Bipolar EEGs were recorded continuously, and subjective ratings of sleepiness obtained every 3 min (before, during and after exposure). After exposure the phone and base-station were switched off, the bedroom darkened, and a 90 min sleep opportunity followed. We report on sleep onset using: (i) visually scored latency to onset of stage 2 sleep, (ii) EEG power spectral analysis. There was no condition effect for subjective sleepiness. Post-exposure, sleep latency after talk mode was markedly and significantly delayed beyond listen and sham modes. This condition effect over time was also quite evident in 1-4Hz EEG frontal power, which is a frequency range particularly sensitive to sleep onset. It is possible that 2, 8, 217Hz modulation may differentially affect sleep onset.

Low SAR Ferrite Handset Antenna Design

The benefits resulting from the inclusion of ferrite in material loaded antennas are investigated, initially through the use of a spherical analytic model and then through a transmission line matrix simulation tool applied to a rectangular slab geometry. It is observed that a material with equality of relative permittivity and permeability in combination with specific positioning of the antenna in relation to the head, can result in the definitive small-size, high efficiency and bandwidth, low specific absorption rate (SAR) antenna. The accuracy of the simulations is validated both through efficiency and SAR measurements of three material coated monopole samples. Further research into optimizing the above attributes and translating them into a handset antenna leads to a multiband antenna design covering the GSM 1800, 1900, UMTS and Bluetooth bands, with a SAR value reduced by 88% compared to conventional phones and an efficiency of 38% at 1.8 GHz. A tri-band antenna design is also presented, utilizing currently available lossy ferrite material and it is considered as the first step towards the feasibility of the ultimate low SAR multiband ferrite handset antenna, until further material development specifically for antenna applications takes place

A study of the validation of RF energy specific absorption rates for simulations of anatomically correct head FDTD simulations and truncated DASY4 standard equipment measurements

This paper presents results of a study concerning the modification of a generic DASY4 twin phantom SAR kit (designed for measurements of mobile phones held to the ear) to facilitate SAR measurements of personal data assistant mobile communications equipment held in front of the face. The source used was a half wavelength dipole illuminating a SAM phantom face. Two half heads bonded together were used and the effect of removing the rearmost part of the phantom head were considered. Results from FDTD simulations show the effects of the modification. When a 60mm section is removed from the back of the head, the 1g and 10g SAR values at 900MHz deviate by about 2.4% and at 1800MHz by about 0.3% from the values obtained with the full head.

Switching a Dual Band PIFA to Operate in Four Bands

The antenna presented in this paper is based on a small dual band PIFA with maximum dimensions 36 mm times 12 mm times 6 mm. This size is typical of a PIFA designed for a contemporary mobile phone. While versatile, at lower frequencies it is often difficult to completely cover the GSM850 and EGSM 900 bands simultaneously using a small antenna. In this paper, a PIFA is reported with switches to select between two sets of low and high resonance pairs. The antenna has been designed with the intention to operate in either of the GSM850/GSM1900 and GSM900/GSM1800 band pairs, while being manufactured with standard planar photolithography processes

L and S shape PIFA antenna for triple-band (DCS/PCS/UMTS) mobile handset

A compact antenna that operates at three frequency bands suitable for mobile handsets is proposed The antenna is a PIFA (planar inverted-F antenna) printed on a dielectric laminate board with a shorting pin and a coaxial cable for feeding. Measured results for the proposed antenna are compared to the simulation results and a significant agreement is observed. The proposed antenna has small dimensions, a rigid structure and relatively low profile compared to conventional PIFAs designs.

Quad-Band Handset Antenna for GSM900/DCS1800/PCS1900/UMTS Bands

1. Abstract An novel compact quadband internal planar inverted-F antenna (PIFA) for contemporary handsets covering the bands GSM-900, DCS-1800, PCS-1900 and UMTS is presented. The proposed antenna consists of a planar antenna element suspended parallel above the dielectric of a single sided PCB. By etching a section of the conducting ground plane below the radiating element, the antenna gains the merits of a planar monopole and consequently a wider bandwidth. The total volume occupied is 38mm x 25mm x 6mm and is suited as internal antenna due to its low profile, small size, wide bandwidth and multi-band behavior. The antenna structure, simulations, return loss measurements, radiation patterns and specific absorption rate (SAR) are also discussed.

Investigation into the realisation of a low-SAR, dual mode material coated antenna for mobile handsets

Previous theoretical and experimental work on material loaded antennas illustrated that choosing a material mix containing equal permittivity and permeability in combination with specific positioning of the antenna in relation to the head can produce the definitive small size, high efficiency, low specific absorption rate (SAR) antenna. Further results obtained from a TLM simulator indicate the antennas ability to operate in wideband dual mode and provide design guidelines for its realisation. New materials are tested and design-engineering techniques are explored, towards the ultimate aim of realising and integrating the antenna into the handset.

A theoretical and experimental study of dielectrically loaded antennas and their contribution towards low-SAR

This paper focuses on material loaded handset antennas and their performance with emphasis on the specific absorption rate. A TLM simulator package is used to verify the theoretical mathematical model, suggesting that a material that contains a mix of equal permittivity and permeability gives rise to the definitive low-SAR antenna whilst maintaining a high efficiency, small size, and broad bandwidth. The simulation results provide design rules for the prototype manufacture and measurement of such an antenna.

Laser-assisted manufacture for performance-optimized dielectrically loaded GPS antennas for mobile telephones

The use of ceramic cores of high dielectric constant is an essential part of a strategy to miniaturize GPS antennas for mobile telephones. The core reduces the guide wavelength of the conducting structures on the antenna, thereby creating a need for high-resolution imaging to maintain very accurate dimensions. It is for this principal reason that a novel laser imaging technology has been developed using a positive electrophoretic photoresist and UV excimer laser mask imaging to produce the conducting features on the surface of the antenna. Furthermore, a significant process challenge in producing this type of antenna concerns the reproducibility of the right-hand circular polarization performance and the bandwidth over which this can be achieved - which becomes progressively smaller as antenna size is reduce. It is therefore a vital requirement that the antennas have the point to be tuned by a laser trimming process at an automatic RF testing station. A galvanometer controlled Nd:YAG laser spot is used to trim the conductive pattern on the top of the antenna following an RF measurement to characterize the resonant frequencies of the four helical conductors. Results demonstrate the laser imaging and trimming techniques ensure a high-speed method of guaranteeing the antenna performance. The technique is appropriate for other antenna types such as GSM, Bluetooth and Wireless LAN.