Beam-switching planar parasitic antenna array

This paper presents a planar parasitic antenna array that achieves beam switching operation by using the Yagi-Uda principle. The treatment of the Yagi-Uda principle in this paper employs closely-spaced directors as opposed to the traditional inter-director spacing, and this shows advantages in terms of the front-to-back ratio (F/B) and size. The beam switching has been realized in 3 principal beam directions through the selective switching of 4 PIN Diodes on the antenna structure. A fully functional antenna using PIN Diodes with an optimized biasing line arrangement and circuitry has been fabricated, and the results obtained through measurement show good agreement with simulation results. The antenna shows good impedance match and beam-switching characteristics in the Wi-Fi frequency band, opening up the possibility of the antenna's use in practical applications

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%

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

Characterisation of an antenna system implanted into a limb phantom for monitoring of bone fracture healing

An antenna system consisting of two implanted monopoles has been investigated. The proposed structure has been simulated in a cylindrical three layer limb phantom and the S11 andS21 responses of the system have been evaluated for the 0.5 to 5 GHz frequency range. This process occurred as the bone fracture that was introduced in the middle of the phantom gradually healed turning from blood to bone marrow and bone cortical in five discrete steps

Conductivity and permittivity measurements of children and adult’s hands covering mobile communications frequency bands

This paper investigates the use of a simple open-ended coaxial line probe for measuring in vivo the relative permittivity and conductivity of human hands at microwave frequencies. In particular, we investigate how these properties are affected by the force with which the probe is pushed into the skin and the time over which the probe is in contact with the skin. Results show these two variables have a large influence on the measured results. We identify a suitable test procedure for use on a large scale volunteer study and present initial relative permittivity and conductivity results from more than 150 volunteers, ranging from ages 11 to 65

Printable windscreen quad-band GSM antenna

The design and simulation of a suitable GSM antenna for integration with the rear windscreen of a car is presented in this paper. A bent asymmetric dipole antenna was chosen to minimise the surface area and thus cause minimal effect to the aesthetics of the car as well as to the driver’s visibility. The antenna has been simulated on a realistic three-layered windscreen. Parasitics were added to the design to improve the bandwidth at 900 and 1800MHz at both European and American bands. The bent asymmetric dipole was advantageous compared to a straight asymmetric dipole because i) the radiation pattern was more omnidirectional and ii) the parasitics at each band could be designed to work independently of each other

Focusing effects of metallic rim-less spectacles at mobile communication frequencies on the energy absorbed in the head

This paper presents simulated and measured results from a study looking at the Specific Absorption Rates (SAR) inside the head due to metallic rim-less spectacles, when the head is irradiated by a dipole source in front of the face. The study concentrates on the GSM1800, PCS1900 and UMTS 2100MHz frequency bands. Simulations were carried out using the homogeneous Specific Anthropomorphic Model (SAM) phantom and a heterogeneous head model developed from the Visible Human Project. SAR measurements were carried out using a DASY4 with the modified rear-entry Loughborough SAM head. The measurements and both sets of simulations show that the metallic crossbar can increase the peak 1g SAR inside the head by approximately 5 times in the GSM1800 uplink frequency band

Design and characterization of a three material anatomical bone phantom for implanted antenna applications

This work presents the development and testing of a three layer anatomical human body phantom suitable for microwave applications. The proposed phantom consisted of bone marrow, bone cortical and muscle layers. The ingredients used for each tissue along with the calculation of the mean square error of the dielectric properties showed good agreement with the dielectric properties of real life tissues and the IEEE SAR measurement standard for tissue mimicking phantoms. The geometrical characteristics of the bone layer can be adjusted to fit the geometry of any desired bone in the human body. The suitability of the phantom has been tested using an implanted antennas application, which has yielded comparable simulation and measurement results

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

Use of a block hand phantom for mobile phone specific absorption rate measurements

Recent studies have shown when using a mobile phone in the talk position, the spatially averaged Specific Absorption Rate (psSAR) inside the head may increase due to the hand. As a result, the use of an anatomically correct hand phantom has already been proposed for psSAR compliance testing. This paper investigates an alternate solution which is more flexible and easier to implement. We test the hypothesis that a dielectric slab placed at the back of the phone during psSAR measurements may provide an acceptable conservative estimate. Measurements conducted on thirteen phones show that different size dielectric slabs can increase the psSAR but may not be representative of the large variations caused by a real hand