Nicholas P. Lawrence

High spatial resolution microwave detection system for Brillouin-based distributed temperature and strain sensors

We present a microwave detection system for coherent detection of spontaneous Brillouin-based distributed temperature and strain measurements. The system was designed to overcome the existing bandwidth limitations of a previously used commercial spectrum analyser and provide a commercially practical solution to the detection of the Brillouin frequency shift and intensity for long range high spatial resolution measurements. The detection system bandwidth corresponds to a potential spatial resolution of ~60 cm. The system was demonstrated as a temperature sensor over a range of 30 km, with a temperature resolution of 1.6 °C and spatial resolution of ~2 m. It was also demonstrated as a combined temperature and strain sensor over a range of 6.3 km with ~1.3 m spatial resolution; temperature and strain resolutions of 3 °C and 80 µe respectively were achieved.

Analysis of millimetre-wave polarization diverse multiple-input multiple-output capacity

Millimetre-waves offer the possibility of wide bandwidth and consequently high data rate for wireless communications. For both uni- and dual-polarized systems, signals sent over a link may suffer severe degradation due to antenna misalignment. Orientation robustness may be enhanced by the use of mutual orthogonality in three dimensions. Multiple-input multiple-output polarization diversity offers a way of improving signal reception without the limitations associated with spatial diversity. Scattering effects often assist propagation through multipath. However, high path loss at millimetre-wave frequencies may limit any reception enhancement through scattering. We show that the inclusion of a third orthogonal dipole provides orientation robustness in this setting, as well as in a rich scattering environment, by means of a Rician fading channel model covering all orientations for a millimetre-wave, tri-orthogonal, half-wave dipole transmitter and receiver employing polarization diversity. Our simulation extends the analysis into three dimensions, fully exploiting individual sub-channel paths. In both the presence and absence of multipath effects, capacity is observed to be higher than that of a dual-polarized system over the majority of a field of view.

Tri‐orthogonal polarization diversity for 5G networks

Millimetre-waves offer the possibility of wide bandwidth and consequently high-data rate for wireless communications. For both uni-polarised and dual-polarised systems, signals sent over a link may suffer severe degradation because of antenna misalignment. Orientation robustness may be enhanced by the use of mutual orthogonality in three dimensions. Multiple-input multiple-output polarisation diversity offers a way of improving signal reception without the limitations associated with spatial diversity. Scattering effects often assist propagation through multipath. However, high-path loss is often considered to limit millimetre-wave propagation, thereby reducing any reception enhancement through scattering. We show that the inclusion of a third orthogonal dipole at a frequency of commercial interest provides antenna orientation robustness in this setting, as well as improved performance in a rich scattering environment, by means of a Ricean fading channel model. Copyright

Tri-orthogonal polarization diversity reception for non-geosynchronous satellite orbit ionospheric channels

Summary Electromagnetic signals propagating through the ionosphere are subject to path delay and the depolarizing effect of Faraday rotation. These are both dependent on global position and link geometry, which constantly vary for satellites in non-geosynchronous orbits. These effects introduce performance error and reduce range resolution of remote sensing polarimetric measurements. Communication with ground receivers may be severely degraded by these effects. In this paper, a tri-orthogonal approach at the receiver is introduced to enhance performance of conventional polarization diverse receive schemes. Performance is measured through a capacity metric. The work presented forms part of a large-field-of-view, non-geosynchronous satellite model exploiting tri-orthogonal receive polarimetry as a means to enhancing link performance in a field-of-view. Copyright

Planar Triorthogonal Diversity Slot Antenna

This communication proposes an easily manufacturable multifunction multiport planar slot antenna with triorthogonal pattern diversity. Distinct radiation patterns are emitted via a common square radiative slot by exploiting three orthogonal modes. These slot modes consist of a magnetic current loop mode with an omnidirectional linearly polarized (OLP) radiation pattern, and two degenerated linear slot modes radiating broadside with orthogonal linear polarizations (LPs). The triorthogonal patterns are obtained in an overlapping frequency band, and the mutual coupling between the ports is minimized through a differential feeding arrangement. This new concept of multiport diversity slot antenna is validated experimentally at a frequency of 5.9 GHz, successfully demonstrating the operation modalities of OLP and LP radiation patterns. A minimum triorthogonal overlapping impedance bandwidth of 2.3% is measured with interport coupling below −35 dB. The proposed antenna could be used as a pattern and polarization diversity antenna, where additionally, a linear combination of the primary triorthogonal patterns can be exploited to further enhance flexibility in pattern generation.

3-D Low Earth Orbit Vector Estimation of Faraday Rotation and Path Delay

An electromagnetic wave propagating through the ionosphere is subject to path delay and the depolarizing effect of Faraday rotation, both of which are dependent on global position and geometry. These effects introduce error and consequently reduce the range resolution of remote sensing polarimetric measurements. Satellite-to-ground communications may be adversely altered by these effects so as to inhibit signal reception. The work presented here introduces a simple vectorized model for a large-field-of-view, low-Earth-orbit, satellite system that yields Faraday rotation and path delay according to global position and geometric parameters. Comparison is made with current models, through the simulation of Faraday rotation and path delay. The presented work may extend the range over which Faraday rotation and path delay estimation are reliable. The work presented forms part of a large-field-of-view, low-Earth-orbit satellite model exploiting multiple-input multiple-output polarimetry in three dimensions.

5G Terrestrial Networks: Mobility and Coverage—Solution in Three Dimensions

The next generation of wireless communications, which is proposed to operate in the mmWave region of the electromagnetic spectrum, offers the potential of high-data rate and increased coverage in response to a rapid growth of mobile data traffic. Operation in an mmWave channel is subject to physical and current technical limitations compared with conventional terrestrial microwave channel propagation. In this paper, the effects of antenna misalignment are considered in an mmWave channel through polarization mismatch. Tri-orthogonal polarization diversity is suggested as a means for mitigating misalignment effects and offering increased link performance over a majority of antenna orientations. A known physically realized planar antenna design offering such diversity is highlighted.