Reconfigurable antenna using photoconducting switches

This paper presents a design for an optically reconfigurable printed dipole antenna. A wideband coplanar waveguide (CPW) to coplanar stripline (CPS) transition is used to feed the balanced printed dipole. Two silicon photo switches are placed on small gaps in both dipole arms equidistant from the centre feed. Light from two infra-red laser diodes channelled through fibre optic cables is applied to the switches. With the gaps in the dipole bridged, the antenna resonates at a lower frequency. Measured return loss results that compare well to the simulated values are also presented, showing a frequency shift of nearly 40%. The change in bore-sight gain along with radiation patterns are also presented

Optically reconfigurable balanced dipole antenna

In this paper, a new design for an optically reconfigurable printed dipole antenna is presented. A wideband coplanar waveguide (CPW) to coplanar strip (CPS) transition is used to feed the printed dipole. Two optically activated silicon switches, controlled using fibre optic cables and near infra-red laser diodes, are placed on small gaps in the dipole arms. The switches enable the dipole length to be optically controlled, thus facilitating frequency switching. Measured return loss results that compare well to the simulated values are also presented, showing a frequency shift of 10.5%

Frequency and beam reconfigurable antenna using photoconducting switches

A design for an optically reconfigurable printed dipole antenna is presented. A wideband coplanar waveguide (CPW) to coplanar stripline (CPS) transition is used to feed the balanced printed dipole. Two silicon photo switches are placed on small gaps in both dipole arms equidistant from the centre feed. Light from two infrared laser diodes channelled through fiber optic cables is applied to the switches. With the gaps in the dipole bridged, the antenna resonates at a lower frequency. Measured return loss results that compare well to the simulated values are also presented, showing a frequency shift of nearly 40%. The change in bore-sight gain along with radiation patterns are also presented. Activating each switch individually results in a near 50 shift in beam nulls

Antenna frequency and beam reconfliguring using photoconducting switches

This paper presents the use of photoconducting switches in antennas for reconfiguring operating frequencies and radiation patterns. It has also been demonstrated that these switches can be used in optically controlled phase shifters. A frequency shift of 40% is achieved with a dipole antenna and an array of patch antennas show beam scanning covering 30deg

Low correlation multiple antenna system for mobile phone applications using novel decoupling slots in ground plane

A compact low profile multiple antenna system for multiple-input-multiple- output (MIMO) applications is proposed. The antenna system combines two monopole type printed antennas with a slotted ground plane for low correlation and high isolation characteristics. The main antenna covers the twelve wireless communication bands required for LTE, GSM, UMTS2110, Bluetooth, WiMAX and WLAN. The auxiliary antenna has a very small volume compared to the main one and covers the ultra-wideband (UWB) frequency range (3.74-12 GHz). The antennas are positioned at opposite ends of the system's ground in order to reduce the mutual coupling between them. The isolation maintained is better than 20 dB over the desired frequency bands, resulting in an envelope correlation coefficient of less than 0.08. The simulation results show good S-parameters, high gain and radiation efficiency, and relatively stable radiation patterns. Due to the compact size and the ultrawide bandwidth, the proposed multiple antenna system is suitable for communication handsets that have size limitations. Results are presented and discussed. © 2013 IEEE

The energy absorbed in the human head due to ring-type jewelry and face-illuminating mobile phones using a dipole and a realistic source

The effect of facial ring jewelry is investigated on the energy absorbed in the head when illuminated by communicationsenabled personal data assistant (PDA)-type devices. We study the relative changes in specific absorption rates in the head due to perturbing metallic rings in proximity to the face illuminated by a 1.8 GHz dipole and a monopole on a conducting box. Simple and complex head models used in a validated finite-difference time-domain (FDTD) simulation are compared with measurements from an industry standard DASY4 SAR measurement system. Both simulation and measurement are referred to the IEEE specific anthropomorphic mannequin head. Results show that metallic rings may alter specific absorption rates (SAR) level distributions within the head. Results are given for several common ring sizes

Effects of metallic spectacles on SAR when using communications enabled PDAs in front of the face

This paper presents simulated and measured results of a study examining the effects of metallic spectacles on the Specific Absorption Rate (SAR) inside a modified Specific Anthropomorphic Mannequin (SAM) head when using various RF sources. We consider dipole sources resonating at 900MHz and 1800MHz as well as three communications enabled PDAs operating in the GSM900 band

Frequency switchable dual-band branch-line coupler

In this paper, silicon switches are implemented in the design of frequency switchable dual-band branch-line coupler. Frequency switching is achieved by increasing the power of the laser applied to the highly resistive silicon wafer and changing the properties of silicon under optical illumination. The advantages of this approach are high-speed switching, electromagnetic transparency (no interference) and thermal and electrical isolation between the coupler and the control circuit. A frequency shift of 35% and 10% has been achieved from all switches off to all switches on in lower (900 MHz) and upper (1800 MHz) frequency bands, respectively

Effect of tongue jewellery and orthodontist metallic braces on the SAR due to mobile phones in different anatomical human head models including children

This paper has used the Finite-difference Time-domain (FDTD) computer simulation technique to investigate Specific Absorption Rates (SAR) in different human head models with metallic jewellery. A dipole excitation has been placed in front of the nose of 4 anatomical heads including a 5 year old and a 12 year old child’s head. Metallic tongue jewellery and orthodontist metallic braces were added to the models and the SAR was investigated over a range of communication frequencies

On the effects of straight metallic jewellery on the specific absorption rates resulting from face illuminating radio communications devices at popular cellular frequencies

This paper presents simulated and measured phantom results for the possible effects that head worn jewellery may have on the relative levels of energy absorbed in the human head with cellular enabled mobile communication devices. The FDTD electromagnetic code used with simple and complex anatomical mathematical phantoms was used to consider the interactions of metallic jewellery, heads and representative sources at 900 and 1800 MHz. Illuminated metallic pins of different lengths were positioned in front of the face. Initially, a homogenous phantom was used to understand the relative enhancement mechanisms. This geometry allowed the results to be validated with the industry standard DASY4 robot SAR measurement system related to the CENELEC head. Jewellery pins were then added to an anatomically realistic head. The relative increase in the 1 g and 10 g SAR, due to a pin with a length 0.4λ near the eyebrows of a complex, anatomically realistic head was approximately three times at 1800 MHz. Such pins increased the SAR averaged over a 1 g or 10 gmass by redistributing the energy absorbed inside the head and focusing this energy towards the area of the head nearest to the centre of the pin. Although, the pins increased the SAR, the SAR standards were not breached and the jewellery produced lower values than those of previous studies when the source was positioned close to the ear