Circular Polarization Modulation for Digital Communication Systems

Conventional approaches of digital modulation schemes make use of amplitude, frequency and/or phase as modulation characteristic to transmit data. In this paper, we exploit circular polarization (CP) of the propagating electromagnetic carrier as modulation attribute which is a novel concept in digital communications. The requirement of antenna alignment to maximize received power is eliminated for CP signals and these are not affected by linearly polarized jamming signals. The work presents the concept of Circular Polarization Modulation for 2, 4 and 8 states of carrier and refers them as binary circular polarization modulation (BCPM), quaternary circular polarization modulation (QCPM) and 8-state circular polarization modulation (8CPM) respectively. Issues of modulation, demodulation, 3D symbol constellations and 3D propagating waveforms for the proposed modulation schemes are presented and analyzed in the presence of channel effects, and they are shown to have the same bit error performance in the presence of AWGN compared with conventional schemes while provide 3dB gain in the flat Rayleigh fading channel.

Circular polarisation frequency selective surface operating in Ku and Ka band

Single and double layer frequency selective surfaces (FSS) for Circular polarization (CP) operation were designed. The designed FSS provide reflection in the Ku-band (11.7 – 12.75 GHz) and transmission in the Ka-band (17.3 – 20.2 GHz). CP is conserved in each of the bands. For the double layer design over the Ku-band the reflection loss was less than 0.05 dB for TE and TM polarizations while the axial ratio was below 0.2 dB. Over the Ka-band transmission loss and axial ratio were each less than 0.25 dB.

Linear to Circular Polarization Reflector with Transmission Band

A frequency selective surface (FSS) which can be utilized as a diplexer for circular polarization (CP) applications is proposed. The structure consists of two dipole-based FSS placed parallel to each other. The dipoles in one array are rotated by 90° with respect to those in the other. For an angle of incidence of 45° at one frequency band the structure allows a CP signal to be transmitted while at a further band it converts a linearly polarized (LP) signal to CP upon reflection. Full-wave simulation results validated the concept.

Near-monochromatic high-harmonic radiation from relativistic laser-plasma interactions with blazed grating surfaces

Intense, femtosecond laser interactions with blazed grating targets are studied through experiment and particle-in-cell (PIC) simulations. The high harmonic spectrum produced by the laser is angularly dispersed by the grating leading to near-monochromatic spectra emitted at different angles, each dominated by a single harmonic and its integer-multiples. The spectrum emitted in the direction of the third-harmonic diffraction order is measured to contain distinct peaks at the 9th and 12th harmonics which agree well with two-dimensional PIC simulations using the same grating geometry. This confirms that surface smoothing effects do not dominate the far-field distributions for surface features with sizes on the order of the grating grooves whilst also showing this to be a viable method of producing near-monochromatic, short-pulsed extreme-ultraviolet radiation.

Linear-to-Circular Polarization Reflector With Transmission Band

A new class of polarizing surface is proposed that in a given frequency band can reflect incident linearly polarized waves with circular polarization (CP) while at other frequencies is transparent allowing incident waves to transmit unaffected. The proposed structure consists of two parallel anisotropic frequency selective surfaces (FSSs) that independently interact with TE or TM waves, respectively. The FSSs are designed to, respectively, transmit TE and TM waves within the same transmission frequency range, so that the combined structure is transparent to all polarizations in this band. Likewise, the two arrays are designed to, respectively, reflect TE and TM incident waves in a common reflection band, so that all polarizations are fully reflected in this range; if the separation of the two arrays is such that the TE and TM components of an incident wave polarized at slant 45° experience a 90° phase shift, reflection will occur in CP. The concept and performance limitations are theoretically investigated using transmission line theory as well as full wave results. The predicted performance is validated by means of experimental results on a fabricated prototype. The proposed structure is pertinent for employment as a quasi-optical diplexer in CP dual-band systems such as reflector antennas.

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.

MEMOIR OF THE LIFE, CHARACTER, AND PUBLIC SERVICES OF THE LATE HON. HENRY WM. DE SAUSSURE, PREPARED AND READ ON THE 15th FEBRUARY, 1841, AT THE CIRCULAR CHURCH, CHARLESTON, BY APPOINTMENT OF THE SOUTH CAROLINA BAR ASSOCIATION.

A special meeting of the Association was held as it was resolved that Chancellor Harper was requested to prepare a memoir of the late Chancellor De Saussure.

An Analysis of Local Wind and Air Mass Directions and Their Impact on Cladosporium Distribution Using HYSPLIT and Circular Statistics

Ecological studies that examine species-environment relationships are often limited to several meteorological parameters, i.e. mean air temperature, relative humidity, precipitation, vapour pressure deficit and solar radiation. The impact of local wind, its speed and direction are less commonly investigated in aerobiological surveys mainly due to difficulties related to the employment of specific analytical tools and interpretation of their outputs. Identification of inoculum sources of economically important plant pathogens, as well as highly allergenic bioaerosols like Cladosporium species, has not been yet explored with remote sensing data and atmospheric models such as Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT). We, therefore, performed an analysis of 24 h intra-diurnal cycle of Cladosporium spp. spores from an urban site in connection with both the local wind direction and overall air mass direction computed by HYSPLIT. The observational method was a volumetric air sampler of the Hirst design with 1 h time resolution and corresponding optical detection of fungal spores with light microscopy. The atmospheric modelling was done using the on-line data set from GDAS with 1° resolution and circular statistical methods. Our results showed stronger, statistically significant correlation (p ≤ 0.05) between high Cladosporium spp. spore concentration and air mass direction compared to the local wind direction. This suggested that a large fraction of the investigated fungal spores had a regional origin and must be located more than a few kilometers away from the sampling point.