Improving signal reliability in outdoor body-to-body communications using front and back positioned antenna diversity

It has previously been shown that human body shadowing can have a considerable impact on body-to-body communications channels in low multipath environments. Signal degradation directly attributable to shadowing when one user's body obstructs the main line of sight can be as great as 40 dB. When both people's bodies obstruct the direct line of sight path, the communications link can be lost altogether even at very short distances of a few metres. In this paper, using front and back positioned antennas, we investigate the utility of a simple selection combination diversity combining scheme with the aim of mitigating human body shadowing in outdoor body-to-body communications channels at 2.45 GHz. Early results from this work are extremely promising, indicating substantial diversity gains, as great as 29 dB, may be achieved in a number of everyday scenarios likely to be encountered in body-to-body networking. © 2012 IEEE.

SIW slot antenna for E-band communications

The paper proposes novel substrate integrated waveguide (SIW) slot antenna for E-band communications. The antenna is designed at a two-layer low temperature co-fired ceramic (LTCC) substrate in 71-76 GHz frequency band. The proposed antenna demonstrates a gain better than 11.3 dBi and efficiency of 85% and can be used as a standalone antenna or as an element of a larger array.

Millimetre wave dielectric characterisation of multilayer LTCC substrate

The paper reports on the mm-wave characterization of a low temperature co-fired ceramic (LTCC) substrate. A substrate integrated resonator (SIW) method is presented for robust extraction of both permittivity and loss tangent of the substrate. The data obtained allow full characterization of the substrate in the 71 GHz – 95 GHz frequency range suitable for accurate modelling of E-and W-band printed circuits.

Circular polarisation frequency selective surface operating in Ku and Ka band

A double layer circular polarization (CP) frequency selective surface (FSS) for use as a dual-band quasi-optical diplexer suitable for deployment in reflector antenna systems is described. The FSS was designed to reflect Ku band signals (11.7–12.75 GHz) while transmitting Ka band signals (17.3–20.2 GHz) and conserving CP in each of these bands. The simulated/measured reflection loss over the Ku band was less than 0.05/0.1 dB for both TE and TM polarizations, while the simulated/measured axial ratio was less than 0.2/0.75 dB. Over the Ka band, the simulated/measured transmission loss for both polarizations was below 0.25/0.4 dB and the simulated/measured axial ratio was less than 0.25/0.75 dB. To the best of our knowledge, this is the first report of a metallo-dielectric FSS that simultaneously operates in CP for an oblique angle of incidence in both Ku and Ka bands.

A Low Radar Cross Section Dipole Antenna Simulation

This paper reports a new method for reducing theRadar Cross-Section (RCS) of a metal backed dipole antenna. Numerical simulations are used to show that when the Perfect Electrical Conductor (PEC) is replaced by a carefully designedFrequency Selective Surface (FSS), the electromagnetic performanceof the antenna is similar in band, but the RCS of the structure is significantly lower out of band. The design of the FSSand the return loss, radiation patterns and RCS are presentedfor an antenna which operates at a center frequency of 4 GHzand the results are compared with a conventional metal backed arrangement

2-bit polarisation agile antenna with high port decoupling

A practical method to achieve both decoupling and six polarisation states by employing the mode-based approach for a four-element antenna is presented. The eigenmode theory as well as a practical implementation scheme are presented. The resulting approach can operate with vertical, horizontal, slant +45°, slant -45°, right-hand circular polarisation, or left-hand circular polarisation. A prototype has been manufactured and measured results show good agreement with simulations.

Robust implantable antenna for in-body communications

A compact implantable printed meandered folded dipole antenna with a volume of 101.8 mm3 and robust performance is presented for operation in the 2.4 GHz medical ISM bands. The implant antenna is shown to maintain its return loss performance in the 2360???2400 MHz, 2400???2483.5 MHz and 2483.5???2500 MHz frequency bands, simulated in eleven different body tissue types with a broad range of electrical properties. Bandwidth and resonant frequency changes are reported for the same antenna implanted in high water content tissues such as muscle and skin as well as low water content tissues such as subcutaneous fat and bone. The antenna was also shown to maintain its return loss performance as it was moved towards a tissue boundary within a simulated phantom testbed.

High-Resolution Microwave Near-Field Imaging Using Resonance Probes

A novel microwave high-resolution near-field imaging technique is proposed and experimentally evaluated in reflectometry imaging scenarios involving planar metal-dielectric structures. Two types of resonance near field probes-a small helix antenna and a loaded subwavelength slot aperture are studied in this paper. These probes enable very tight spatial field localization with the full width at half maximum around one tenth of a wavelength, λ, at λ/100-λ/10 standoff distance. Importantly, the proposed probes permit resonance electromagnetic coupling to dielectric or printed conductive patterns, which leads to the possibility of very high raw image resolution with imaged feature-to-background contrast greater than 10-dB amplitude and 50° phase. In addition, high-resolution characterization of target geometries based on the cross correlation image processing technique is proposed and assessed using experimental data. It is shown that printed elements features with subwavelength size ~λ/15 or smaller can be characterized with at least 10-dB resolution contrast.