Broadband Circularly Polarized Research Articles

Broadband Circular Polarizer Based on Plasmon Hybridizations

This paper presents a broadband circular polarizer with a ring/disk cavity structure, which is a broadband application of plasmon hybridizations. The proposed design can convert a linearly polarized wave to a circularly polarized wave from 12.66 GHz to 17.43 GHz within a bandwidth of 30%. The broadband polarization conversion characterization results from the different plasmon hybridization modes induced in the ring/disk cavity. The proposed broadband circular polarizer is demonstrated by both full-wave simulation and measurement.

A Novel Broadband Circularly Polarized Monopole Antenna Based on C-Shaped Radiator

The design and implementation of a compact monopole antenna with broadband circular polarization is presented in this letter. The proposed antenna consists of a simple C-shaped patch and a modified ground plane with the overall size of 0.33 λ × 0.37 λ. By properly embedding a slit in the C-shaped patch and improving the ground plane with two triangular stubs, the measured broadband 3-dB axial-ratio bandwidth of 104.7% (2.05–6.55 GHz) is obtained, while the measured impedance bandwidth of 106.3% (2.25–7.35 GHz), defined by –10-dB return loss, is achieved. The performance for different parameters is analyzed. The proposed antenna is a good candidate for the application of various wireless communication systems.

Gain-Improved Broadband Circularly Polarized Antenna Array With Parasitic Patches

A broadband circularly polarized (CP) antenna array with improved gain is proposed. The antenna consists of a CP loop that provides sequential phase, a 2 × 2 patch array, and four parasitic rectangular elements. The square patches are capacitively coupled with four strips, which are connected to the loop feeding network. Moreover, four parasitic rectangular patches are introduced to enhance the gain in the lower band. The measured 10-dB impedance bandwidth is 15.9% (5.01–5.87 GHz), and the 3-dB axial-ratio bandwidth of 640 MHz (5.08–5.72 GHz) is also obtained. Besides, the proposed antenna array has a flat gain over the operating frequency and the maximum gain of 12.5 dBi is achieved at 5.3 GHz.

Broadband Circularly Polarized Crossed-Dipole Antenna With a Single Asymmetrical Cross-Loop

This letter presents a broadband cavity-backed circularly polarized (CP) crossed-dipole antenna encircled by a novel asymmetrical cross-loop. By using the single parasitic cross-loop, the antenna has a simple structure and a compact configuration. More importantly, it produces additional two CP modes. The suitable combination of the crossed dipole and the cross-loop provides broadband CP operation. The measured results show that the proposed antenna with an overall dimension of $1.1{\lambda _0} \times 1.1{\lambda _0} \times 0.28{\lambda _0}$ (in terms of the CP center frequency) features broadband CP characteristics of an impedance bandwidth with $S_{11}$ < –10 dB from 3.14 to 6.34 GHz (67.5%) and a 3 dB axial-ratio bandwidth from 3.83 to 6.62 GHz (53.4%). A unidirectional right-hand circular-polarized radiation pattern with a peak gain of 10.62 dBi is achieved over the CP operating band.

A Broadband Slot Antenna With Unidirectional Circularly Polarized Radiation Patterns

A novel circular slot antenna is proposed in this letter to generate a broadband circular polarization (CP) wave. This antenna consists of a Γ-shaped radiator and a circular ground with a cut of three ellipses. By adjusting the size and position of these ellipses, a CP wave can be realized. A chip resistor, which is used to receive the currents and decrease reflection, can significantly enhance the CP bandwidth. The study of the effect to antenna performance of different geometric parameters has been conducted. The results show that good performance of impedance bandwidth ( $S$ 11 < −10 dB) is approximately 106.1% (1.01 ∼ 3.29 GHz), and 3-dB axial-ratio bandwidth is approximately 89.7% (1.26 ∼ 3.31 GHz). Moreover, the antenna exhibits a stable average gain of about 6.0 dBic in the operating band, and the circularly polarized peak gain is about 7.6 dBic.

Broadband Circular Polarization Antenna Based on Inverted Suspended Circular Patch with Square Slot

In this paper, an inverted suspended circular patch with square slot design is proposed for broadband circular polarized antenna. The antenna was designed based on L-probe technique and air gap of 10 mm distance between substrate and copper ground. L-probe technique is used in this antenna design to feed the 50 Ohm SMA connector signal through the feedline to the antenna structure. The proposed antenna had been designed and simulated by using computer simulation technology (CST) software. This antenna design is targeted for wireless local area network (WLAN) application which operating frequency at 2.4 GHz. Antenna performances in term of return loss, resonant frequency, bandwidth, gain, axial ratio, directivity, total efficiency and radiation pattern at the design frequency are analyzed. Result of simulation show that the proposed antenna achieved axial ratio below 3 dB which is 0.62 dB with return loss -35.60 dB at targeted frequency. Comparison result of simulation and measurement show that the return loss bandwidth (RLBW) and realized gain of the antenna at 2.4 GHz frequency decreases from 556 MHz to 354 MHz with gain 7.76 dB to 4.54 dB. However, the proposed antenna covers a wider bandwidth of 2.4 GHz where both simulation and measurement bandwidth is over 350 MHz.

A Broadband Circularly Polarized Printed Monopole Antenna With Parasitic Strips

A novel printed monopole antenna is presented for circular polarization (CP) operation with broad axial-ratio (AR) bandwidth. The antenna is composed of a monopole, a ground plane, and two parasitic strips. By utilizing two spiral strips coupled by the monopole, broadband CP radiation is achieved. The measured results show the 10-dB impedance bandwidth is 2.75 GHz (1.75-4.5 GHz) and the antenna also has a 3-dB AR bandwidth of 64.7% (2.2 GHz, 2.3-4.5 GHz). The proposed antenna features simple structure and broad AR bandwidth, which is desirable for various wireless communication systems.

CPW-Fed Wideband Circularly Polarized Printed Monopole Antenna With Open Loop and Asymmetric Ground Plane

A wideband circularly polarized (CP) printed monopole antenna with coplanar waveguide feeding is proposed. The antenna is composed of a rectangular monopole, an asymmetric ground plane, and a square-ring with an open gap at the bottom. By utilizing the asymmetric ground plane, CP radiation could be achieved at the upper band first. Then, a rectangular open loop is introduced to obtain wide-impedance bandwidth and broadband CP characteristic. The measured results demonstrate that the 10-dB impedance bandwidth reaches 96.5% (2.76 GHz, 1.48-4.24 GHz) and the 3-dB axial-ratio bandwidth is 63.3% (1.9 GHz, 2.05-3.95 GHz). In addition, parameter studies are performed, and surface current analysis is also given to show the operating mechanism of CP operation.

A Broadband Circularly Polarized Crossed-Dipole Antenna

A unidirectional broadband circularly polarized (CP) crossed-dipole antenna is presented in this communication. This antenna has a simple feeding structure, which uses an unequal power network. It can simply realize 90° phase shift and four equal power divisions. The study of the antenna performance with different geometric parameters has been conducted. Working band of designed antenna covers the BeiDou Navigation Satellite System, GPS, and GLNOSS bands. An optimized antenna is designed and measured, the measured results agree well with the simulated results. The results show good performance of impendence bandwidth is approximately 66.2% (1.01–2.01 GHz), the 3-dB axial-ratio bandwidth (ARBW) of approximately 41.3% (1.21–1.97 GHz). Moreover, the measured bore-sight antenna gain is stable and varying not too much, which average value is 6.0 dBic with less than 1.5-dB variation within the 3-dB ARBW.

Compact broadband CP monopole antenna with tilted branch

A novel compact monopole antenna with wide circularly polarised (CP) bandwidth is designed, fabricated and measured. The wide impedance bandwidth and broadband CP characteristic are achieved based on a simple tilted monopole structure, which consists of a slotted rectangular patch and an improved ground plane. The measured impedance bandwidth with return loss better than 10 dB is 97.4% (1.10–3.19 GHz), the measured 3 dB axial-ratio bandwidth is 59.1% (1.11–2.04 GHz) and the measured peak gain within the operating band is 4.84 dBic, which indicates that it is a good candidate for the application of various global navigation satellite systems.

Nonuniform Broadband Circularly Polarized Antenna Array for Vehicular Communications

Road safety applications drive the development of vehicular communications as support to intelligent transport systems. The communications network necessary for this is supported by dedicated short-range communications (DSRC), which is based on roadside units (RSUs) and onboard units. In the RSU, the DSRC physical-layer standards, along with practical issues, require specific radiation patterns of the respective antenna, leading to the use of unusual arrays of antennas. This paper describes a new concept based on a binomial array structure, which simplifies the design of the antenna array while ensuring good performance. The new structure developed for this antenna enabled the design of a feed network using unbalanced power dividers in the same plane as that of the radiating elements, maintaining the favorable characteristics of microstrip antennas. The array thus obtained met the desired specification, in terms of a radiation pattern with a bandwidth greater than 1 GHz.

Tailoring Infrared Refractory Plasmonic Material to Broadband Circularly Polarized Thermal Emitter

Circularly polarized (CP) thermal emission possesses huge application value in the fields of infrared detecting and polarimetric thermal imaging; however, the naturally occurring infrared source is incoherent and unpolarized. In this paper, we designed a broadband CP source adaptive for high temperature in consideration of the collision frequency of the electrons increasing with temperature. Compared with the structure proposed before, “I”-shaped resonators based on refractory plasmonic material generate the linearly polarized (LP) emission and the dielectric quarter-wave plate enhances the degree of emitted CP by suppressing the parasitic radiation. More than 80 % right-handed circularly polarized (RCP) emissivity in wavelengths ranging from 3.28 to 4.81 μm within 706 to 884 K is theoretically achieved.

All-dielectric circular polarizer with nearly unit transmission efficiency based on cascaded tensor Huygens surface.

In this paper, we demonstrate a high-efficiency and broadband circular polarizer based on cascaded tensor Huygens surface capable of operating in the near-infrared region. The high efficiency originates from the simultaneous excitation of the Mie-type electric and magnetic dipole resonances within an all-dielectric rotationally twisted strips array. Due to the symmetry breaking of the structure in the light propagation, one state of the circularly polarized light can pass through freely, while the other state is largely blocked. The maximum polarization transmission reaches 0.97 with a polarization suppression ratio of 911:1, which represents a major advance in the performance compared with previously reported circular polarizers. The proposed metamaterial possessing the merits of high efficiency and simple inclusions has potentials for applications in biological detector, optical communication and sensor.

Broadband Circularly Polarized 2 × 2 Antenna Array with Sequentially Rotated Feed Network for C-Band Application

In this paper, a unique broad-band circularly polarized antenna array with sequentially rotated feed-network for C-band applications is proposed. In order to, implement presented array element, a novel and miniaturized square slot antenna, with one pair of attached L-shaped and a T-shaped strips at ground surface, for decreasing cross polarization purity, is presented. Two L-shaped strips with different length are inserted at slot antenna’s patch to enhance impedance matching. The symmetric coplanar waveguide is used for feeding the slot element. The antenna element obtains a 3 dB axial ratio bandwidth from 5.85 to 6.25 GHz. For further improving of radiation attributes, elements in 2 × 2 array are linked together by sequentially rotated feed to achieve wider axial ratio and impedance matching bandwidths. The main advantage of feed network is designed in a way that to have less coupling effect between elements. The axial ratio (AR) and impedance bandwidths of array is from 4.9 to 6.45 GHz (for AR <3 dB) and 4 to 8.1 GHz (for VSWR <2), respectively. Simulation and measurement results validated the proposed array design.

Broadband circularly polarizing dichroism with high efficient plasmonic helical surface

We propose and experimentally demonstrate a broadband and high efficient circularly polarizing dichroism using a simple single-cycle and single-helical plasmonic surface array arranged in square lattice. Two types of helical surface structures (partially or completely covered with a gold film) are investigated. It is shown that the circular polarization dichroism in the mid-IR range (3µm - 5µm) can reach 80% (when the surface is partially covered with gold) or 65% (when the surface is completely covered with gold) with a single-cycle and single-helical surface. Experimental fabrications of the proposed helical plasmonic surface are implemented with direct 3D laser writing followed by electron beam evaporation deposition of gold. The experimental evaluations of the circular polarization dichroism are in excellent agreement with the simulation. The proposed helical surface structure is of advantages of easy-fabrication, high-dichroism and scalable to other frequencies as a high efficient broadband circular polarizer.

Square slot antenna with two spiral slots loaded for broadband circular polarisation

A simple design of a broadband circularly polarised (CP) square slot antenna with two loaded spiral slots is proposed. The CP operation is realised by embedding a pair of inverted-L-shaped strips around two opposite corners of the square slot and can be markedly improved by loading two spiral slots in the ground plane. By using these modifications, the 3 dB axial ratio bandwidth (ARBW) of about 5 GHz, which is chiefly ascribed to the existence of two spiral slots and impedance bandwidth of larger than 111% are achieved. However, the overall size of the antenna is only 20 × 20 × 0.8 mm3, it covers wider ARBW than many of the designed slot antennas.

SCRLH-TL Based Sequential Rotation Feed Network for Broadband Circularly Polarized Antenna Array

In this paper, a broadband circularly polarized (CP) microstrip antenna array using simplified composite right/left-handed transmission lines (SCRLH-TLs) based sequential rotation (SR) feed network is presented. The characteristics of a SCRLH-TL are investigated initially. Then, a broadband low insertion loss 45o phase shifter is designed using the SCRLH-TL and the phase shifter is em- ployed in constructing a SR feed network for CP antenna array. To validate the design method of the SR feed net- work, a 2×2 antenna array comprising sequentially rotated coupled stacked CP antenna elements is designed, fabri- cated and measured. Both the simulated and measured results indicate that the performances of the antenna ele- ment are further enhanced when the SR network is used. The antenna array exhibits the VSWR less than 1.8 from 4 GHz to 7 GHz and the axial ratio (AR) less than 3 dB from 4.4 GHz to 6.8 GHz. Also, high peak gain of 13.7 dBic is obtained. Besides, the normalized radiation patterns at the operating frequencies are symmetrical and the sidelobe levels are low at φ = 0o and φ = 90o.

Coupling between core and cladding modes in a helical core fiber with large core offset

We analyzed the effect of resonant coupling between core and cladding modes in a helical core fiber with large core offset using the fully vectorial method based on the transformation optics formalism. Our study revealed that the resonant couplings to lower order cladding modes predicted by perturbative methods and observed experimentally in fibers with small core offsets are in fact prohibited for larger core offsets. This effect is related to the lack of phase matching caused by elongation of the optical path of the fundamental modes in the helical core. Moreover, strong couplings to the cladding modes of the azimuthal modal number much higher than predicted by perturbative methods may be observed for large core offsets, as the core offset introduces higher order angular harmonics in the field distribution of the fundamental modes. Finally, in contrast to previous studies, we demonstrate the existence of spectrally broad polarization sensitive couplings to the cladding modes suggesting that helical core fibers with large core offsets may be used as broadband circular polarizers.

COMPACT BROADBAND CIRCULARLY POLARIZED MONOPOLE ANTENNA FOR GLOBAL NAVIGATION SATELLITE SYSTEM (GNSS) APPLICATIONS

A compact monopole antenna with broadband circular polarization for global navigation satellite system (GNSS) applications is presented in this paper. The proposed antenna comprises a simple tilted radiator fed by 50-Ohm microstrip line and an improved ground plane. By embedding two isosceles right triangular slits and introducing an isosceles right triangular perturbation in the ground plane, the circularly polarized (CP) performance can be improved significantly. The impedance and circular polarization characteristics are studied by simulation and measurement. With a compact size of 79 × 79 × 1. 5m m 3 for the fabricated antenna, a measured 10-dB return loss bandwidth of 35.6% (1.13-1.62 GHz) and a 3-dB AR bandwidth of 35.4% (1.14-1.63 GHz) can be achieved.

A Broadband Circularly Polarized Waveguide Antenna Design for Low Cross-Polarization

An L-shaped probe with a surrounding aperture such as a waveguide can generate circular polarization (CP) waves. Circular waveguide antennas using an L-shaped probe have broadband characteristics both in axial ratio (AR) and in input impedance, however cross-polarization (XPOL) is easily generated due to its asymmetrical structure resulting in a radiation pattern that has narrow CP azimuth range. In this paper, design techniques to reduce the XPOL generated from a circular waveguide antenna using an L-shaped probe are proposed. As a result, XPOL is reduced by around 10 dB, and CP is radiated over a wide angle range of 120-150° covering frequencies from 7.35 to 9.75GHz.