Circular Polarization Properties Research Articles

A Compact Printed Monopole Antenna With Wideband Circular Polarization

In this paper, a novel compact circularly polarized (CP) monopole wideband printed patch antenna is proposed. The antenna consists of a hook-shaped branch connected at the partial rectangular ground plane and reversed unequal arm with an L-shaped microstrip-feed which helps the antenna achieve wideband circular polarization property. The measured results display that the proposed compact ( $44\times 44\times 1.6$ mm3) antenna acquires 3.12 GHz (56%, 2.25–4.0 GHz) at the 10-dB impedance bandwidth, and the axial ratio (AR) bandwidth at 3-dB is 3.48 GHz (63.61%, 2.38–4.60 GHz). A parametric study of different design parameters and measured and simulated results of the various characteristics of the designed antenna is presented to verify the performance of the radiation mechanism. Finally, by scaling only, the dimensions of the proposed antenna without changing another parameter, a wide impedance and AR bandwidth are achieved. On account of the simple planar structure and scaling dimension with broadband CP property, the proposed antenna does apply in a variety of wireless communication systems such as ISM, WiMAX, WLAN, satellite communications, cordless telephones, weather radar systems, and lower frequency bands CP type applications.

Efficient feeding geometries for rectenna design at 2.45 GHz

Efficient feeding geometries for rectenna design at 2.45 GHz are described. The proposed rectenna consists of two layers low cost FR-4 substrates in which circular polarisation and harmonic rejection properties are embedded. A voltage doubler rectifier with open stub matching network and the radial stub is designed at the bottom substrate to transform the ac signals to a dc voltage. A right triangular slot is designed in the ground plane to suppress second and third harmonics which improves the rectenna conversion efficiency to 75.043% at an input power of 20 dBm. The proposed rectenna design has the advantages of providing circular polarisation and harmonic rejection with a compact size and low cost which makes it a good candidate for microwave power transmission applications.

Compact circularly polarized inset-fed circular microstrip antenna for 5 GHz band

This paper proposes a compact circularly polarized microstrip antenna with Left-Hand Circular Polarization (LHCP) property for wireless communication system at 5.7GHz (U-NII 5GHz band). In this design, a tapered-slot is included and it can act as the second signal source of the antenna to generate circular polarization property and this can remove the need of the external second signal source. The axial ratio of ∼2 and the radiation pattern results prove that the designed antenna meets the LHCP criteria. Moreover, the inset feeder is selected and it demonstrates the improvement on bandwidth and input impedance of the antenna.

A Wide-Angle and Circularly Polarized Beam-Scanning Antenna Based on Microstrip Spoof Surface Plasmon Polariton Transmission Line

In this letter, a wide-angle beam-scanning antenna with circular polarization (CP) characteristic is proposed. The antenna consists of two layers. Microstrip spoof surface plasmon polariton (SPP) is introduced on the bottom layer as a slow-wave feeding line. A series of circular patches are placed on the top layer as radiating elements. Simulated and measured results indicate that beam-scanning angle of the proposed antenna is improved and CP beam-scanning ability is obtained by introducing perturbation on the radiating elements. In the operating band of 11–15 GHz, measured scanning angle of the fabricated antenna is from –32° to +34°. The antenna axial ratio (AR) is below 3 dB at the corresponding beam direction, and gain is above 12.8 dBi over the whole band. It has potential applications in radar and wireless communication systems for simple structure, low-cost fabrication, wide beam-steering, and CP properties.

Truncated Circular Cone Slot Antenna Array That Radiates a Circularly Polarized Conical Beam

A truncated circular cone slot array antenna that radiates a circularly polarized (CP) conical beam is presented. The direction into which the conical beam radiates depends mainly on the tilt angle of the outer conductor as well as the proper arrangement of the positions of its two slot arrays. The CP property is realized by introducing quasi-perpendicular slots that are cut into the outer conductor of a truncated circular cone. To illustrate the performance characteristics of this CP conical beam antenna, the tilt angle is set to 45° and the beam angle is pointed at 45° from boresight within the operating band. A prototype was fabricated and tested. The measured results demonstrate that its −10 dB impedance bandwidth ( $\vert S_{{11}}{\rm{\vert \, dB) is 720 MHz, from 5.05 to 5.77 GHz; and its 3 dB axial-ratio (AR) bandwidth is 500 MHz, from 5.5 to 6.0 GHz. Its realized gain over this AR bandwidth ranges from 4.84 to 5.8 dB. The designed beam direction can be easily changed to meet specific application requirements. Moreover, it can be readily reconfigured to be a conformal antenna mounted on the top of a high-speed mobile platform.

Physical Conditions and Variability Processes in AGN Jets through Multi-Frequency Linear and Circular Radio Polarization Monitoring

Radio polarimetry is an invaluable tool to investigate the physical conditions and variability processes in active galactic nuclei (AGN) jets. However, detecting their linear and circular polarization properties is a challenging endeavor due to their low levels and possible depolarization effects. We have developed an end-to-end data analysis methodology to recover the polarization properties of unresolved sources with high accuracy. It has been applied to recover the linear and circular polarization of 87 AGNs measured by the F-GAMMA program from July 2010 to January 2015 with a mean cadence of 1.3 months. Their linear polarization was recovered at four frequencies between 2.64 and 10.45 GHz and the circular polarization at 4.85 and 8.35 GHz. The physical conditions required to reproduce the observed polarization properties and the processes which induce their variability were investigated with a full-Stokes radiative transfer code which emulates the synchrotron emission of modeled jets. The model was used to investigate the conditions needed to reproduce the observed polarization behavior for the blazar 3C 454.3, assuming that the observed variability is attributed to evolving internal shocks propagating downstream.

Compact Multi-Band Circularly Polarized CPW Fed Antenna Based on Metamaterial Resonator

In this letter, a compact size multiband metamaterial based antenna with circular polarization property is presented. A metamaterial unit cell consist of four thin strips that constitute the modified square split ring resonator (MSSRR) which each of strips generate negative refraction index in antenna's resonant frequency modes. The proposed antenna operate at Bluetooth (2400---2484 MHz specified by IEEE 802.11b/g), WiMAX (3.3---3.6 GHz specified by IEEE 802.16) and C-band (4---8 GHz) while circular polarization feature is obtained at these operational bands. The total size of antenna is 20 × 20 × 1.5 mm3 and realized on FR4-epoxy substrate. The design concept was confirmed by fabrication of the antenna scheme and measuring its characteristics. The extracted results show the antenna exhibits good agreement with simulation ones.

Rectenna Designs for RF Energy Harvesting System: a Review

In this paper, a review of different types of rectifying antennas (rectennas), used for harvesting RF ambient signals, is presented. This work focuses on rectenna design as one important technique of wireless energy transfer. The most important parameters in rectenna design such as conversion efficiency, rectenna size, antenna gain and polarization, rectifier element, and overall performance of the rectenna are studied and compared. It is noted from studies that rectenna design suffers from low conversion efficiency and large size which limit their use in wireless applications. Therefore, to overcome the above mentioned limitations, some techniques such as microstrip antenna with, a metamaterial structure, harmonic suppression and circular polarization properties can be suggested. A voltage doubler rectifier can be used with the metamaterial microstrip antenna to improve the conversion efficiency of the rectenna. Hence, High efficiency and small size of the rectenna will enable the rectenna to produce sufficient DC voltage and current to charge batteries used in medical applications and wireless sensors applications as well.

Reconfigurable CP cavity back with ability to change polarisation diversity

A novel configuration of a circularly polarised (CP) reconfigurable aperture antenna is presented. In a number of recent studies, some new and promising designs for circularly polarised cavity-backed antennas with a parasitic patch have been proposed to obtain circular polarisation and unidirectional radiation properties. However, these designs still have the disadvantage of producing single polarisation. To overcome this disadvantage, a reconfigurable antenna using pin diodes is proposed. By combining the reconfigurable aperture antenna with a parasitic patch and a low profile cylindrical cavity and optimising the antenna parameters, a high gain antenna with significantly improved impedance and axial ratio bandwidths can be achieved.

Semifractal antenna with dual‐bands filtering and circular polarization properties using SCBP and MDGS structures

ABSTRACTThis article proposes the novel design of a coplanar waveguide fed (CPW‐Fed) monopole ultra wideband (UWB) semifractal antenna with dual band‐notched specification and circular polarization (CP) attributes at ITU‐R (7.725–8.5 GHz). The semifractal patch of antenna is composed of unitcell which unitcell patterns form branchs of tree. The fractal geometry in radiator leads to have an effective impedance matching over the UWB spectrum. The Dual‐band filtering property can be adjusted finely by embedding a pair of L‐strips length inside the slotted conductor‐backed‐plane (SCBP) and mirrored defected ground structure (MDGS). Beside that, the length and position of L‐strips have great role in achieving CP in ITU‐R band. The actual size of the miniature and fabricated antenna is limited to 15 × 15 × 1 mm3 and it operates across 2.2–12.52 GHz for S11<−10dB, except the bandwidths of 3.1–3.6 for WiMAX and 5–6 GHz for WLAN. The antenna has CP bandwidth from 7.5 to 8.5 GHz for axial ratio less than 3 dB. The antenna's parameters were investigated to fully understand their affects. Main parameters achieved from this analysis enabled the optimization of the antenna's entire performances. The prototype was fabricated, to validate the performance of antenna, through simulations and measurements. The measured results certify the antenna radiates omnidirectionally and has a large impedance bandwidth, dual‐band rejection and CP property. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2483–2487, 2015

Slot multi‐arm helix antenna with simple and efficient feeding network

A slot helix antenna with a simple and efficient feeding network for satellite communications and global positioning system (GPS) applications is presented. Rectangular slotted openings, ended with fan-shaped slots, are designed for the helix-shaped slot radiating arms so as to obtain excitation from the circular microstrip feeding line. By adjusting the coupling, the four or more slot radiating elements can obtain appropriate excitation, which leads to the good circular polarisation properties of the antenna.

Exciton spin dynamics and photoluminescence polarization of CdSe/CdS dot-in-rod nanocrystals in high magnetic fields

The exciton spin dynamics and polarization properties of the related emission are investigated in colloidal CdSe/CdS dot-in-rod (DiR) and spherical core/shell nanocrystal (NC) ensembles by magneto-optical photoluminescence (PL) spectroscopy in magnetic fields up to 15 T. It is shown that the degree of circular polarization (DCP) of the exciton emission induced by the magnetic field is affected by the NC geometry as well as the exciton fine structure and can provide information on nanorod orientation. A theory to describe the circular and linear polarization properties of the NC emission in magnetic field is developed. It takes into account phonon mediated coupling between the exciton fine structure states as well as the dielectric enhancement effect resulting from the anisotropic shell of DiR NCs. This theoretical approach is used to model the experimental results and allows us to explain most of the measured features. The spin dynamics of the dark excitons is investigated in magnetic fields by time-resolved photoluminescence. The results highlight the importance of confined acoustic phonons in the spin relaxation of dark excitons. The bare core surface as well as the core/shell interface give rise to an efficient spin relaxation channel, while the surface of core/shell NCs seems to play only a minor role.

Miniaturized Circularly Polarized Loop Antenna for Biomedical Applications

A novel circularly polarized antenna is proposed at 902-928 MHz Industrial, Scientific, and Medical band for implantable applications. By properly positioning the feed and shorts, either right-hand circular polarization property or left-hand circular polarization property can be realized. Slow wave concept is utilized by loading patches to the radiated loop antenna to achieve miniaturization. Thus, a compact size of 13 mm × 13 mm × 1.27 mm is obtained. Compared to the unloaded loop antenna of the same size, the centre frequency shifts from 1.93 GHz to 882.5 MHz, which suggests a miniaturization of 54.4%. The simulated results show that a wide bandwidth of 18.2% can be realized with |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | below -10 dB and axial ratio below 3 dB. The simulated realized gain is -32 dBi at 915 MHz. The measurement is carried out in both skin-mimicking gel and pork, and a bandwidth of 27.8% and 29.4% can be achieved with |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | below -10 dB, respectively. The measurement of |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> | reveals that circular polarization can be obtained for the proposed configuration.

A New Kind of Circular Polarization Leaky-Wave Antenna Based on Substrate Integrated Waveguide

A new kind of circular polarization leaky-wave antenna with N-shaped slots cut in the upper side of substrate integrated waveguide (SIW) is investigated and presented. The radiation pattern and polarization axial ratio of the leaky-wave antenna are studied. The results show that the width of N-shaped slots has significant effect on the circular polarization property of the antenna. By properly choosing structural parameters, the SIW based leaky-wave antenna can realize circular polarization with excellent axial ratio in 8 GHz satellite band.

An Omnidirectional Circularly Polarized Slot Array Antenna With High Gain in a Wide Bandwidth

In this letter, a novel omnidirectional circularly polarized (CP) slot array antenna with high gain is proposed. The array is based on the coaxial cylinder structure. The omnidirectional radiation is realized by four perpendicular slot pairs surrounding the axis of coaxial cylinder in the outer conductor, which can be seen as a basic omnidirectional CP element. With four of these basic elements along the axis of the coaxial cylinder, the radiation slot array is constructed with desired omnidirectional CP property and particularly stable high gain in a wide bandwidth. To match the antenna, three cascade coaxial lines with the same outer radius but different characteristic impedance are connected to its input. Measured results show that the proposed antenna performs a $-10~\hbox{dB}$ impedance bandwidth ( ${ S}_{11} ) of 16.4% ranging from 5.05 to 5.95 GHz and a 3-dB axial-ratio (AR) bandwidth of 14.5% ranging from 5.1 to 5.9 GHz. Within the common band ranging from 5.1 to 5.9 GHz, the measured gain in the omnidirectional plane ( $xy$ -plane) is stable and higher than 5 dBic.

Dual Circularly Polarized Omnidirectional Antenna with Slot Array on Coaxial Cylinder

A dual circularly polarized (CP) omnidirectional antenna based on slot array in coaxial cylinder structure is presented in this paper. It is constructed by perpendicular slot pairs around and along the axis of the coaxial cylinder to realize the omnidirectional CP property, and two ports are assigned in its two sides as left hand circularly polarized (LHCP) port and right hand circularly polarized (RHCP) port, respectively. The proposed antenna achieves a bandwidth of 16.4% ranging from 5.05 to 5.95 GHz with an isolation higher than 15 dB between the two CP ports, and the return loss (RL) is higher than 10 dB within the bandwidth in both of the two ports. From the measured results, the average axial ratio (AR) of the proposed antenna in omnidirectional plane is lower than 1.5 dB.

Wave propagation in twisted metamaterials

Twisted metamaterials, i.e. arrays of identical planar metasurfaces stacked with a sequential rotation, offer new possibilities for manipulating and engineering wave propagation. This paper presents a generalized Floquet analysis to discuss wave propagation in these kind of structures. The authors show that the eigenmodes support specific circular polarization properties based on a lattice effect even when achiral inclusions are considered.

Frequency-tunable circular polarization beam splitter using a graphene-dielectric sub-wavelength film.

Manipulating the circular polarization of light is of great importance in chemistry and biology, as chiral molecules exhibit different physiological properties when exposed to different circularly polarized waves. Here we suggest a graphene/dielectric-stacked structure, which has both the properties of an epsilon-near-zero material and the high Hall conductivity of graphene. The proposed sub-wavelength structure demonstrates efficient manipulation of circular polarization properties of light. In a quite broad frequency range and at a large oblique incidence angle, the present magnetically active structure is transparent for one circularly polarized wave, and opaque for another. Such an effect can be further tuned by changing the magnitude of the applied magnetic field and chemical potential of graphene.

Su2013 Roles of Linear and Circular Polarization Properties and Effect of Wavelength Choice on Differentiation Between Ex Vivo Normal and Cancerous Gastric Samples Using Polarimetry Imaging

Su2013 Roles of Linear and Circular Polarization Properties and Effect of Wavelength Choice on Differentiation Between Ex Vivo Normal and Cancerous Gastric Samples Using Polarimetry Imaging

Roles of linear and circular polarization properties and effect of wavelength choice on differentiation between ex vivo normal and cancerous gastric samples.

Multispectral Mueller matrix imaging was performed over a spectral range from 470 to 632 nm on 4-μm unstained gastric tissue sections. A complete set of polarization parameters was derived. The combination of linear depolarization and linear retardance yields the highest accuracy in sample classification. When the depolarization of linearly polarized light due to scattering is independent of the orientation angle of the incident linear polarization vector, the derivation of linear polarization properties will require only 3×3 Mueller matrix, which would significantly reduce the complexity of the polarimetry imaging system. When additional parameters are needed to complement the two linear polarization parameters, retardance, circular depolarization, and depolarization can be included in classification in the order of preference. However, these additional parameters would require the measurement of 4×4 Mueller matrix. In addition, it appears that wavelength is not a critical factor in terms of classification accuracy for thin tissue sections in this study.