Transmission line modelling of cylindrical cavity loaded with a slotted dielectric rod

© 2015 IEEE. This paper examines the effect of loading a microwave cylindrical cavity with radially slotted dielectric rod. Although, methods for the computation of the resonant frequency of dielectric loaded cavity have been presented in the literatures, the effect of placing radial slots on axisymmetric dielectric load in relation to the cavity resonance has not been studied. The study was carried out using a cylindrical TLM solver developed in MATLAB. A parametric check on the effect of varying the slot depth and width shows that the slot width has greater effect on the cavity resonance than the slot depth. It was also discovered that multiple narrow slots on the load affects the resonance frequency of the cavity more than a single wide slot. The effect of periodicity of the slots on the resonance frequency was also investigated

Investigating the effects of control lines on a frequency reconfigurable patch antenna

The objective of the paper is to investigate the effects of metallic control lines on a frequency reconfigurable patch antenna. The designed antenna resonates at 3 different frequencies in range of 3-4GHz. Simulation and measurement results of return loss with and without control lines are presented. We have also discussed the challenges of implementing the bias lines

Intermodulation distortion in a photoconductive microwave switch

Single-tone harmonic and two-tone intermodulation distortion measurements are presented for a photoconductive microwave switch. The switch consists of a lightly doped die of silicon mounted over a gap in a transmission line. The switch is controlled via near infra-red light delivered by a fiber optic cable. Whilst under constant illumination, the third order intercept for a 2 GHz CW signal is extrapolated to be 74 dBm. Under a 1 MHz spaced two-tone signal, the extrapolated intermodulation intercept point is 58 dBm

Patch antenna directivity analysis using an equi-area method

The widespread exploitation of mobile cellular phones and use of wireless devices such as PDAs, in-vehicle Global Positioning System (GPS) receivers, and the future deployment of mobile satellite digital audio and video has developed a re-energized interest in efficient and accurate measurement techniques for antennas. This paper demonstrates directivity analysis of a patch antenna using a new fast, rotation-invariant spherical near-field antenna measurement technique. The method is based on an equi-area surface partitioning algorithm. The paper evaluates the sampling technique’s performance when compared with a normal spherical near-field measurement technique using equal angle sampling

Polarisation dependent EBG surface with an inclined sheet via

This paper presents a novel polarisation dependent EBG (PDEBG) surface which makes use of sheet vias. The performance of the surface is analysed whilst varying the length, thickness and inclination of the vias. It is observed that the phase difference between the x-polarised and y-polarised component of the reflected wave can be controlled by varying these parameters. Furthermore, the surface exhibits a polarisation conversion property with potential use in a variety of antennas

Stitched transmission lines for wearable RF devices

A novel stitched transmission line for wearable devices has been manufactured and tested to measure its scattering parameters from 0.04 to 4GHz. The stitched transmission line which is 150mm long consists of an inner conductor surrounded by a tubular insulating layer. For shielding purpose, the structure is stitched onto a denim material with a conductive thread with the aid of a novel manufacturing technique using a standard hardware. The S-Parameters were investigated with three different stitch angles 85°, 65° and 31° through simulation and experiments, demonstrating that the stitched transmission line can work usefully and consistently from 0.04 to 4GHz

Textile-to-rigid microstrip transition using permanent magnets

A novel transition between a rigid-substrate and a flexible-substrate microstrip for use in wearable devices is described. The contact force between the conductors of the two microstrips is supplied by a pair of rectangular magnets. A simulation and measurement study carried out on a test jig comprising a back-to-back pair of such transitions demonstrated an insertion loss of better than 0.5 dB/transition can be achieved in the range of 0-3 GHz

Design and operation influences regarding rise and fall time of a photoconductive microwave switch

This paper evaluates the effect switch design and control method have on the rise and fall time of a photoconductive microwave switch at 2GHz. The effects of switch dimensions, switch fabrication methods and light intensity of the control mechanism are investigated. Switch rise time is affected by switch dimension and optical illumination intensity. Switch fall time is dependent on passivation of the silicon - which is a fabrication step often used to improve the conductivity within photoconductive devices

Investigating factors affecting photoconductive microwave switch performance using 3D em simulation

A series of 3D EM simulation models are presented in order to determine the effect that conductivity profile, passivation layer and connection method have on the transmission performance of a photoconductive microwave switch. The use of 3D EM simulation can help quantify the benefit and impact of different approaches before the manufacture stage. The aim is to find methods to reduce insertion loss of the switch to provide maximum efficiency when the device is integrated into reconfigurable applications. Results show improvement to the transmission is possible by altering passivation thickness and designing optical feed to maintain signal planarity

Embroidered metamaterial antenna for optimized performance on wearable applications

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim In this work, an embroidered metamaterial monopole antenna based on a split ring resonator electromagnetic bandgap shielding structure is designed, simulated, and tested. This work investigates the impact of different types of embroidering metamaterial patterns on the antenna performance, shielding effect in terms of human safety through specific absorption rate analysis and degree of material wearability, in comparison with the standard antenna topologies. The proposed antenna design presents a full compact embroidered metamaterial device manufactured in felt textile substrate and requires a 85 × 70 mm2area, operating at 2.45 GHz. On-voxel analysis reveals that specific absorption standards are satisfied for both public and occupational sector with a significant safety margin whereas the antenna performance in terms of gain and directivity are significantly optimized with regard to standard wearable materials