Circular Polarization Properties Research Articles

Improved Wheeler Cap Method Based on an Equivalent High-Order Circuit Model

The conventional Wheeler cap method usually produces accurate radiation efficiency of small antennas when the antennas under test (AUTs) operate as a simple series or a parallel RLC resonance circuit. However, this method often gives unreliable radiation efficiency if the AUT has a complicated operating principle such as circular polarization (CP), multiple resonances, or broad-band properties. In this paper, we propose an improved Wheeler cap method based on the equivalent high-order circuit model including transformers to provide accurate radiation efficiency, although the AUT does not operate as a simple resonance circuit. For building equivalent high-order circuit models, a method for estimating the initial values of a genetic algorithm (GA) is also proposed, which effectively reduces the searching space and improves the convergence of the optimization. To verify the proposed method, we measure the radiation efficiency of a CP microstrip antenna, a UHF RFID tag antenna, and a triple-resonance microstrip antenna.

INVESTIGATION ON USING CPSS ELEMENTS IN DUAL CIRCULAR POLARIZATION REFLECTARRAY ANTENNAS

In this paper, properties of three types of Circular Polarization Selective Surface (CPSS) cells including Pierrot, Morin, and Tilston, for using in dual circular polarization reflectarray antenna design are investigated. First they are designed for a center frequency about 10GHz, and circular polarization properties including Reflection Loss, Transmission Loss, Reflected Axial Ratio, and Transmitted Axial Ratio are calculated and presented. Finally, reflection phase curves are presented, and the comparison between simulated properties is accomplished. Simulations show that Tilston cell is more optimum in dual circular polarization reflectarray antennas.

Compact Circularly Polarized Multiband Antennas for RFID Applications

This paper presents multiband circularly polarized (CP) antennas for radio frequency identification (RFID). A coax-fed and a microstrip-line-fed antennas having optimized cross-slots in their patches are first designed for dual-band CP operation. The microstrip-line-fed design is then modified, by incorporating a U-shaped slot in its partial ground plane, to achieve additional operation band with a CP characteristic. Simulation and measured results of the presented designs are reported. The measured results are in accordance with the computed ones. The compact size and CP property make these designs suitable for RFID applications.

Circularly Polarized Proximity-Fed Microstrip Array Antenna for Micro Satellite

Design of circular polarization microstrip antenna array was developed to support micro-satellite technology. Circular polarization antenna array used for data transmission applications operating in the S band frequencies from the satellite to the ground station . In this study of the patch array using proximity coupling techniques in this study to obtain high gain and wide of bandwidth. The structure of the antenna array design consists of four identical square patch elements and to use the concept of corporate transmission line fed power divider network uses three transformers quarter-lambda T-junction. Bandwidth impedance matching for resonance between two patches is ¾ l antenna system for center frequency of 2.25 GHz. The antenna is designed using the method of moments through simulation with microwave office software applications. The results of simulations and measurements obtained antenna parameters, such as: bandwidth of return loss <-10 dB above 100 MHz resonant frequency shifted to 1.75%, VSWR (1 to 2), the bandwidth of axial ratio <3 dB is 1.6% (narrowband) and the maximum directivity (gain) is 9.128 dB. Overall study results showed good performance antenna array with circular polarization properties, high gain and operates in the S band frequency micro satellite system.

Temperature dependence of the dynamics of optical spin injection in self-assembled InGaAs quantum dots

We report the temperature dependence of the dynamics of optical spin injection from GaAs barriers into self-assembled quantum dots (QDs) of In0.5Ga0.5As. Transient circular-polarization properties of photoluminescence (PL) from excited states in QDs depend strongly on the temperature (T) and rate-equation analysis shows the T-dependent dynamics of spin injection. The filling for the majority spin states is strongly suppressed as T increases above 100 K, enhancing the circular polarization degree of PL. This suppression originates from thermal redistribution of electrons from the excited states in the QDs to the barrier. In contrast, spin relaxation during the injection becomes significant at T ≥ 150 K.

Dual-Band Spiral Patch-Slot Antenna With Omnidirectional CP and Unidirectional CP Properties

A novel dual-band microstrip antenna with omnidirectional circularly polarized (CP) and unidirectional CP characteristic for each band is proposed in this communication. Function of dual-band dual-mode is realized based on loading with metamaterial structure. Since the fields of the fundamental modes are most concentrated on the fringe of the radiating patch, modifying the geometry of the radiating patch has little effect on the radiation patterns of the two modes ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> = 0, + 1 mode). CP property for the omnidirectional zeroth-order resonance ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> = 0 mode) is achieved by employing curved branches in the radiating patch. Then a 45 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> inclined rectangular slot is etched in the center of the radiating patch to excite the CP property for the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> = + 1 mode. A prototype is fabricated to verify the properties of the antenna. Both simulation and measurement results illustrate that this single-feed antenna is valuable in wireless communication for its low-profile, radiation pattern selectivity and CP characteristic.

Circular polarization patch antenna design with diagonal periodic metallic via holes

A circular polarization (CP) patch antenna is proposed for the first time in this article. The proposed antenna is developed based on a patch antenna combined with one row of diagonal periodic metallic via holes. By optimizing the location of the periodic metallic via holes, two orthogonal waves with 90° phase difference are excited using single feed and a CP patch antenna is obtained. A CP antenna is designed based on the proposed structure and simulated by Ansoft HFSS. The designed CP antenna is fabricated and measured. The measured results present return loss |S11| > 10 dB from 10.4 to 11.6 GHz. The radiation pattern is also measured, and it exhibits good circular polarization property with 3-dB axial ratio (AR) of 1.2 dB and gain of 4.02 dBic. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett1100, 2013; 1097 this 1100 online at wileyonlinelibrary.com. DOI 10.1002/mop.27529

Split-Ring FSS Spiral Phase Plate

This letter gives the first report of a planar phase plate structure based on frequency selective surface (FSS) technology for the generation of helical far-field radiation patterns with circular polarization properties. The unit cell of the structure comprises two orthogonal split-ring resonators designed to ensure 180 phase shift between orthogonal transmission coefficients. This property is exploited to obtain progressive rotational phase shift within the structure and thus synthesize 360 spiral phase profile. Measured far-field radiation patterns demonstrate spiral phase front generation for 10-GHz circularly polarized waves transmitted through the structure.

Optical transition of the charged excitons in InAs single quantum dots

Quantum dot (QD) samples studied in the experiment are grown by molecular-beam epitaxy on semi-insulating GaAs substrates. The photoluminescences (PLs) of the excitons in a single QD are measured at 5 K. The PL spectra of the excitons, biexcitons and charged excitons are identified by measuring and analyzing both PL peaks of the circular and linear polarization and power-dependent PL properties. The charged exciton emissions can be tuned by applying a bias voltage, i.e., negatively charged excitons are changed into positively charged excitons by changing the voltage from 1.0 to -1.0 V. It is shown that the electron-spin will slowly relax compared with that of the hole when they relax from wetting layer into the QD.

MINIATURIZED CROSSED-DIPOLE CIRCULARLY POLARIZED FRACTAL ANTENNA

A miniaturized crossed-dipole fractal antenna with circular polarization is presented in this letter. The radiating elements of the antenna were built as the Koch curve, and the antenna was mounted on a specially designed ground plane. The in∞uence of ground plane to beamwidth and axial ratio of fractal antenna is also experimentally studied. The bandwidth of the VSWR 6 1:5 : 1 within 3dB axial ratio for the fractal antenna is about 5.98%. The measured results show that the proposed fractal antennas have good circular polarization property, e-ciency and 23.4{33.5% size reduction comparing with the conventional crossed-dipole antenna. Furthermore, the comparison of the designed antenna and existing technique was also presented. The tested results are in good agreement with that of the simulations.

CRLH 전송 선로 구조를 이용한 -1 모드 원형 편파 패치 안테나

본 논문에서는 composit right-left handed(CRLH) 전송 선로에서 발생하는 -1 모드를 이용하여 단일 급전을 갖는 소형 원형 편파 메타 물질 안테나를 제안한다. -1 모드는 일반적인 패치 안테나의 기본 모드인 +1 모드와 같은 성질을 가지고 있기 때문에, 원형 편파의 동작 원리를 동일하게 적용할 수 있다. 따라서 서로 수직하는 편파와 <TEX>$90^{\circ}$</TEX>의 위상차를 갖는 두 개의 -1 모드들을 이용하여 원형 편파 특성을 갖는 메타 물질 안테나의 설계가 가능하다. 두 개의 -1 모드를 얻기 위해서 삼각형의 형태를 갖는 4개의 버섯 구조를 이용하였고, 모드 간에 <TEX>$90^{\circ}$</TEX>의 위상차를 인가하기 위해서 삽입된 inter-digital gap의 크기를 최적화 하였다. 추가적으로 임피던스 매칭을 위해 coupled-fed 급전 구조를 사용하였다. 제안된 안테나의 4개로 배열된 버섯 구조의 면적은 <TEX>$0.161{\lambda}_0{\times}0.161{\lambda}_0$</TEX>이며, RT/duroid5880 기판에 설계되었다. 제작된 안테나의 중심 주파수는 2.845 GHz로 측정되었고, 2.830 GHz부터 2.850 GHz까지 동작하는 것을 확인하였다. 또한, 2.842 GHz부터 2.847 GHz까지 원형 편파의 특성이 확인되었고, 방사 효율은 46 %로 측정되었다. In this paper, a compact circularly polarized metamaterial patch antenna using the -1 mode that is induced by the composit right-left handed(CRLH) transmission line is proposed. Basically, since the -1 mode is the same properties with the +1 mode of the conventional patch antenna, the circular polarization(CP) is realized. If two orthogonal -1 modes are excited with <TEX>$90^{\circ}$</TEX> phase difference, the CP property can be obtained. In order to obtain two orthogonal modes and <TEX>$90^{\circ}$</TEX> phase difference, 4 mushroom structures having the shape of triangle are employed and the inter-digital gaps are optimized, respectively. The fabricated antenna is based on RT/duroid5880 substrate and the total area of the 4 mushrooms is <TEX>$0.161{\lambda}_0{\times}0.161{\lambda}_0$</TEX>. It is confirmed that the center frequency of the proposed antenna is measured as 2.845 GHz and it operates from 2.830 GHz to 2.850 GHz. In addition, the antenna maintains the CP property from 2.842 GHz to 2.847 GHz at the peak gain and the measured radiation efficiency is 46 %.

Wide aperture circularly polarized antenna for small telemetry satellites

This paper focuses on the design of a telemetry antenna system intended for small satellites. It provides an axial ratio (AR) lower than 3 dB over ±60° conical space angle with over 20% of bandwidth. The antenna consists of a multilayer patch element fed by a wideband feeding circuit. The latter is an appropriate adjustment of 90° hybrid couplers and 180° ring coupler. We show that this design provides high-quality circular polarization properties for agile small satellites without having to suspend their mission to download their data and also without sacrificing the antenna low profile and wide bandwidth. The antenna is fabricated and the experimental performance is presented and followed by a discussion.

Compact and efficient 2.45 GHz circularly polarised shorted ring-slot rectenna

A compact and efficient rectenna based on a printed shorted annular ring-slot antenna with circular polarisation properties has been designed and evaluated at 2.45 GHz. The rectifier part is localised at the back side and centred inside the radiating element, resulting in a more compact structure in comparison with most conventional devices where rectifying circuit and antenna parts are geometrically clearly separated. In addition, the printed annular ring antenna is mismatched at the 4.9 GHz second and 7.35 GHz third harmonics, thus avoiding the use of an input lowpass filter. The proposed antenna and rectifier circuit have been first simulated and optimised separately using electromagnetic and circuit analyses, and then connected together. A maximum efficiency of 69% and an output DC voltage of 1.1 V have been measured over an optimised 2500 Ω resistive load at a power density of 20 µW/cm2. This rectenna is particularly suitable for powering wireless sensors or sensor networks by recycling ambient RF energy because it exhibits a global efficiency of more than 50% for power densities more than 10 µW/cm2.

A Dual-Band Microstrip Antenna with Omnidirectional Circularly Polarized and Unidirectional Linearly Polarized Characteristics Based on Metamaterial Structure

A novel single-feed dual-band microstrip antenna with omnidirectional circularly polarized (CP) and unidirectional linearly polarized (LP) characteristics for each band is proposed in this paper. The function of dual-band dual-mode is realized based on loading modified mushroom structure. By employing curved branches in the radiating patch, CP property for the omnidirectional zeroth-order resonance (n = 0 mode) is achieved. As the curved branches have little effect on the radiation pattern of patch mode, LP property for n = +1 mode stays the same. A prototype is fabricated to verify the properties of the antenna. Both simulation and measurement results illustrate that this antenna is valuable in practical application for its low-profile, radiation pattern selectivity and polarization diversity.

Leaky Coaxial Cable With Circular Polarization Property

A hybrid method of FDTD and far field integration is used to simulate and analyze the polarization properties of leaky coaxial cables with circumferential asymmetry slot structures. It is found that the LCX with circumferential asymmetry slots can excite both the circumferential and axial components of the radiation field, and the magnitude and phase differences between them change with the structural parameters of the asymmetry slot significantly. Based on the analysis, two novel designs of LCXs which can generate circular polarization wave within a corridor along the cables were proposed.

Artificial magnetic surface for circular polarization improvement

AbstractA novel approach to improve the circular polarization properties of a small elliptically polarized (EP) radiating element is presented. The enhancement in circular polarization is obtained by mounting the radiating element close to an artificial magnetic conductor (AMC). To explain the antenna operating principle, two different typologies of radiating element have been initially considered, i.e., a small spiral antenna and a dipole. Both antennas are EP, but the excited current distribution on the AMC screen are circular and linear, respectively. We inferred that only a circular current distribution determines the XPD improvement in correspondence of the AMC resonances. The prototype of the small spiral antenna in the vicinity (λ0/18) of the AMC screen has been manufactured and tested. Measurements confirmed a remarkable improvement in spiral cross polarization discrimination (XPD) in correspondence of the two AMC resonances. The dual‐band behavior of the AMC could be exploited in applications where multifrequency operation is required. The low profile structure is characterized by an overall thickness of 1.1 cm, which corresponds to ∼λ0/12 at the centre of the operating band. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1782–1786, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25345

Polarization Property of Leaky Coaxial Cable With Overlapped Triangle Slots

The polarization properties of the leaky coaxial cable (LCX) slotted by a pair of overlapped triangles are analyzed by a hybrid method involving software HFSS and far-field integration approach. The effect of the slot structural parameters and the operating frequency on the polarization property is studied by analyzing the magnitude and the phase differences of the two orthogonal components of the radiation field. The results show that it is possible to design a LCX that can radiate a circularly polarized wave by properly choosing the structural parameters of the slot. The experimental results also show that the LCX with circular polarization property can be realized. Using this kind of LCX, the detrimental fading caused by orientation effects in mobile communications can be effectively mitigated.

Compact cavity‐backed four‐arm slot spiral antenna

AbstractThis article introduces a miniaturized four‐arm slot spiral antenna on a ceramic dielectric substrate with a thin back cavity. The simulated and experimental results show that the proposed antenna is of good circular polarization and radiation pattern properties at 1.561 GHz, with measured gain of more than 6 dB at the zenith, and more than −4 dB for above 5° elevation angle. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2141–2143, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24534

Miniaturized compound spiral slot antenna

AbstractThis article introduces a miniaturized compound spiral slot antenna with a wideband balun and a back cavity. The simulated and experimental results show that the proposed antenna presents good circular polarization and wideband properties. Its measured return loss is less than −10 dB in the frequency range 0.75 to 8 GHz (10.7:1) and the axial ratio is less than 3.5 dB in the range 0.95 to 8 GHz. Comparing with the conventional spiral antenna, the proposed antenna diameter is only one fourth of that of the former, therefore the antenna size is significantly reduced. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2799–2801, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23801

Compact circular polarized patch antenna with harmonic rejection

AbstractDesign of circularly polarized antenna using circular patch with single feed is proposed. The circular polarization (CP) property with second harmonic rejection can be achieved by embedding two circular slots in the patch resonator. By changing the size and position of the slots, two orthogonal modes with equal amplitude and 90° out of phase are simultaneously excited. In the meanwhile, the embedded slots blocking the second harmonic signal is especially suitable for the circuits with nonlinear elements, such as rectify antenna (rectenna). Furthermore, the patch is simple and compact with 12% of the antenna area reduction. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 45–48, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23009