Low-Profile Circularly Polarized Research Articles

A Low-Profile Circularly Polarized Millimeter-Wave Broadband Antenna Analyzed with a Link Budget for IoT Applications in an Indoor Scenario.

Broadband antennas with a low-profile generating circular polarization are always in demand for handheld/ portable devices as CP antennas counter multipath and misalignment issues. Therefore, a compact millimeter-wave antenna is proposed in this article. The proposed antenna structure comprises two circular rings and a circular patch at the center. This structure is further embedded with four equilateral triangles at a 90° orientation. The current entering the radiator is divided into left and right circular directions. The equilateral triangles provide the return path for current at the differential phase of ±90°, generating circular polarization. Structural development and analysis were initially performed through the characteristic mode theory. It showed that Modes 1 to 4 generated good impedance matching from 20 to 30 GHz and Modes 1 to 5, from 30 to 40 GHz. It also demonstrated the summation of orthogonal modes leading to circular polarization. The antenna-measured reflection coefficient |S11| > 10 dB was 19 GHz (23-42 GHz), and the axial ratio at -3 dB was 4.2 GHz (36-40.2 GHz). The antenna gain ranged from 4 to 6.2 dBi. The proposed antenna was tested for link margin estimation for IoT indoor conditions with line-of-sight (LOS) and non-line-of-sight (NLOS) conditions. The communication reliability with co- and cross-polarization was also studied under these conditions, and the results proved to be satisfactory.

Low-profile Circularly Polarized Dual-beam Holographic Antenna

Low-profile Circularly Polarized Dual-beam Holographic Antenna

A Low-Profile Circularly Polarized Antenna with Hemispherical Axial-Ratio Beam Coverage by DualMode Radiation Patterns Merging

A Low-Profile Circularly Polarized Antenna with Hemispherical Axial-Ratio Beam Coverage by DualMode Radiation Patterns Merging

A Novel Characteristic Mode Method to Enhance Axial-Ratio Bandwidth of Low-Profile Circularly Polarized Planar Antennas

A Novel Characteristic Mode Method to Enhance Axial-Ratio Bandwidth of Low-Profile Circularly Polarized Planar Antennas

Low-profile Circularly Polarized Conformal Antenna Array with Side Lobe Suppression for Vehicular SATCOM Applications

A circularly polarized microstrip antenna array with low side lobe levels is proposed for Vehicular Satellite Communication. The suppression of side lobe levels is accomplished by the non-uniform power distribution utilized to feed the individual patch elements. Impedance matching is ensured by the incorporation of a quarter-wave transformer via a microstrip line fed to the edge of the patch. When the proposed amplitude-weighted feed is compared to the conventional corporate feed, simulation results indicate a reduction in side lobe levels of 8.9 dB. The proposed antenna is constructed out of RT/DUROID 5880 material, which is lighter, more flexible, and less expensive than ceramic materials. The radiation characteristics of the proposed antenna are compared when the antenna is planar versus when it is made to conform to the roof of the vehicle. The measured results indicate a reflection coefficient at the resonant frequency of -31.5 dB and -27.7 dB when conformal, an impedance bandwidth of 410 MHz and 180 MHz when conformal, an axial ratio bandwidth of 140 MHz and 170 MHz when conformal, and a peak gain of 15.719 dB and 14.335 dB when conformal. The measured results validate the simulation results that this proposed antenna is appropriate for a variety of Vehicular Satellite Communication applications.

A Low-Profile Compact Broadband CP DRA for RF Energy Harvesting Applications

In this letter, a low-profile circularly polarized (CP) chamfered rectangular dielectric resonator antenna (RDRA) is designed and investigated for radio frequency energy harvesting (RFEH) applications. The proposed modified RDRA comprises of dielectric resonator (DR) made up of Alumina material (ε r = 9.9) mounted on the PEC ground plane. Dual unequal triangular-shaped vertical slits are engraved on the rectangular DR for generating the orthogonal modes with CP characteristics. The optimized antenna offers an impedance bandwidth (IBW) of 51.4% (2.25–3.81 GHz) and axial ratio bandwidth (ARBW) of 14.8% (3.25–3.77 GHz), respectively. The peak realized gain and maximum radiation efficiency are 7.18 dBi and 97.8% in desired frequency bands. Due to the wide impedance and AR bandwidths with realized gain and radiation efficiency, the optimized antenna is suitable for integration with a rectifier circuit for RF energy harvesting applications. A rectifier circuit with a single shunt diode topology is also designed for rectification purposes. The rectifier achieved 67.16% RF-DC power conversion efficiency (PCE) at 3.5 GHz and 5dBm input power. At 0dBm input power, the rectifier achieved 60.26% PCE. The effective input power range, during which the PCE maintains above 50%, is calculated to be 15.2 dBm from −3.5 to 11.7 dBm.

Low-Profile circularly polarized substrate integrated array antenna

In this paper, a novel low-profile circular polarization (CP) substrate integrated array antenna is proposed which is designed as a multilayer printed circuit board (PCB) structure, consisting of a lower feeding part-substrate integrated waveguide (SIW) and an upper radiating element - sixteen hollow square patches (HSP) evenly distributed in a square array and divided into four groups. The circular polarization (CP) characteristic is realized by chamfering each HSP in the left and right corners, and the greatest common bandwidth of the return loss and the axial ratio (AR) is obtained by adjusting the top chamfer size of each HSP. Simulation results show that the overall usable CP bandwidth is 41.2 GHz-42.1 GHz, the gain in the operating frequency band and the radiation efficiency (RE) are up to 16.1dBic and 91%, respectively, and the low-profile of antenna is less than 0.1λ 0.

A Low Profile Circularly Polarized Microstrip Antenna with Equilateral Triangular Patch and Parasitic Elements for Dual Application Band

A Low Profile Circularly Polarized Microstrip Antenna with Equilateral Triangular Patch and Parasitic Elements for Dual Application Band

A Broadband Low-Profile Circularly Polarized Radial Line Slot Antenna

This article presents a circularly polarized corporate-fed radial-line slot antenna (CF-RLSA) operating in Ka-band and realized in low-cost, low-profile printed circuit board (PCB) technology. The radiating aperture is fed by a corporate feed network based on a broadband pillbox-like circular transition. The proposed feeding system results in a 67% gain bandwidth improvement compared to classical center-fed radial line slot antenna (RLSA) designs. Pattern stability versus frequency is also achieved. The bandwidth improvement provided by the corporate-feed topology is analytically derived for the general case of circular apertures with uniform amplitude illumination. This predicted improvement is confirmed by measurements. The prototype is optimized using a dedicated numerical tool, then fabricated and characterized. A good agreement is obtained between simulated and measured gain bandwidths, with a demonstrated relative bandwidth of 6.9% at 29 GHz for a maximum gain of 35.5 dBi and a 260 mm diameter for the radiating aperture.

A Low Profile Circularly Polarized Beam Scanning Patch Array Fed by Parallel Plate Waveguide

A low-cost, low-profile circularly polarized beam scanning patch array is presented. The patch array is fed by the coupling slots of parallel plate waveguide (PPW), which is excited by a substrate integrated waveguide-based plane wave line source generator. By suggesting a new impedance match method, the coupling slots and truncated patch array are combined for circularly polarized radiation. The beam scanning capability is achieved by the variable inclination method. In the PPW guiding wave layer, a circular plate is cut and separated from the main body of the PPW to make it rotatable around its axis. By rotating the assembly of the circular plate and the above patch layer, the phase difference between the adjacent radiation elements could be controlled. Thus, the circularly polarized beam scanning is realized. A Ku-band prototype array is fabricated and measured to verify the design. The measured peak gain is 19.6 dBi and the scanning range is ±40°, in which range the gain variation is below 2.7 dB and the axial ratio is less than 2.8 dB.

A Low-RCS and High-Gain Planar Circularly Polarized Cassegrain Meta-Antenna

Achieving highly directive radiation with broadband operation, low scattering, and thin profile for a circularly polarized (CP) antenna is particularly challenging and yet rarely reported. Here, we propose a strategy of a CP Cassegrain meta-antenna by combining a planar helical antenna, a metasurface main reflector, and a metamaterial subreflector. The main reflector is designed to achieve focusing for CP waves at 13 GHz. The subreflector is chessboard-configured chiral metamaterial slab composed of two different types of chiral meta-atoms, aiming to achieve spin- and direction-selective CP transmissions and reflections. The distance between two reflectors is half of focal length, which enables our antenna to be dubbed as a folded reflectarray. The low radar cross section (RCS) is achieved based on scattering cancellation technique by realizing near 180° reflection phase difference between two neighboring chessboard submeta-atoms. Thanks to the architecture of the two reflectors, the proposed antenna exhibits high gain and low profile simultaneously according to image theory. For verification, a planar CP Cassegrain antenna, excited by a left-handed CP (LCP) planar helical antenna, is numerically studied, fabricated, and experimentally measured. Numerical results are in good agreement with the experimental ones, showing a peak right-handed CP (RCP) gain of 26.6 dBi at 12.6 GHz. Furthermore, the backward monostatic RCS of the antenna is dramatically reduced over −10 dB in a broad bandwidth from 8.4 to 15.7 GHz when it is illuminated by an LCP planar wave. Our proposed Cassegrain antenna features simultaneously broadband, high gain, low profile, and low RCS, providing a new avenue to low-profile CP reflectarrays with invisibility.

Low-Profile Circularly Polarized Staircase Curl Antenna Array With 2:1 Impedance and 50% AR Bandwidths for 5G mmW Communications

In this communication, a low-profile circularly polarized (CP) staircase curl antenna array with 2:1 impedance bandwidth and 50&#x0025; axial ratio (AR) bandwidth is proposed for fifth-generation (5G) millimeter-wave (mmW) communications. It overcomes a vital drawback of complex multilayer structure of the wideband CP antenna array. By fully taking advantage of 3-D staircase layout, the curl element achieves 2:1 impedance bandwidth, 57.9&#x0025; AR bandwidth, and a maximum gain of 7.4 dBic. Accordingly, benefiting from the tapered matching transformer, a single-layer full-corporate microstrip feeding network with 111.4&#x0025; impedance bandwidth is constructed. For demonstration, an <inline-formula> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> staircase curl antenna array is designed on three-layer PCB laminates. The proposed antenna array is measured with an impedance bandwidth of 76.9&#x0025; (20.0&#x2013;45.0 GHz) and an AR bandwidth of 53.6&#x0025; (23.1&#x2013;40.0 GHz), demonstrating a promising candidate to be used in 5G mmW communications.

Harmonic Suppression and Size Reduction of a Low-Profile CP Patch Antenna by Using Nondegenerate Modes

A novel design method of harmonic suppression and size reduction of a circularly polarized (CP) microstrip patch antenna (MPA) is presented by using nondegenerate modes. Based on a circular MPA, a pair of orthogonal modes could be generated between these undesired resonant modes. Then, by loading the shorting pins in a quarter fan-shaped patch, all these undesirable high-order modes could be suppressed between them. After that, the higher and lower modes are moved closer to each other by cutting a long slot at the angle bisector of the fan-shaped patch, providing the CP radiation pattern. Finally, a prototype of this proposed antenna has been designed, produced, and measured to verify the design concept. The experimental results show that the proposed antenna has an impedance bandwidth of 286 MHz (13 774–14 060 MHz), axial ratio bandwidth of 80 MHz (13 900–13 980 MHz), and a left-hand CP peak gain of around 4.8 dBi. Most importantly, the CP antenna has realized the harmonic suppression of about 15 GHz, which has an obvious advantage as compared to the traditional CP MPA. Moreover, the antenna still holds the primary low-profile, single-radiator, simple structure, and high-efficiency simultaneously.

A Novel Low-Profile Circularly Polarized Diversity Patch Antenna With Extremely Small Spacing, Reduced Size, and Low Mutual Coupling

A novel low-profile circularly polarized (CP) diversity patch antenna with extremely small edge-to-edge distance, reduced size, and low mutual coupling is proposed under dual modes. Initially, the single microstrip patch antenna (MPA) is theoretically investigated by using characteristic mode analysis. It demonstrates that a large number of radiative modes, i.e., CM1 to CM7, are excited for the traditional MPA. By selecting its quarter patch configuration with shorting pins, only a few modes, i.e., CM2 and CM7, could be resonated for the quarter patch antenna (QPA). Meanwhile, their nonbroadside radiated fields could be transformed into the broadside radiation. Particularly, the polarizations of CM2 and CM7 are maintained orthogonally with each other. Next, a linear slot is etched on the patch to reduce the magnitude ratio between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert E_{\mathrm {\theta }}\vert $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert E_{\varphi }\vert $ </tex-math></inline-formula> components. After that, the resonant frequency of CM7 is moved closely to that of CM2 for nearby 90° phase difference. With these arrangements, the compact CP performance is acquired by combining its CM2 and CM7. Furthermore, a pair of QPAs with CP diversity is deeply studied. The results prove that the antenna has successfully acquired both of left-handed CP (LHCP) and right-handed CP (RHCP) performances at dual ports. Moreover, the low mutual coupling between them is generated under extremely small spacing. In final, the proposed antenna is fabricated and tested. Both of LHCP and RHCP patterns are formed of around 4.785 GHz. Besides, the proposed antenna occupies the small overall volume <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.023\lambda _{\mathrm {g}}^{3}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{\mathrm {g}}$ </tex-math></inline-formula> is the guided wavelength), that is only half of the traditional patch ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.045\lambda _{\mathrm {g}}^{3}$ </tex-math></inline-formula> ), and maintains the isolation as high as about 24 dB under extremely small distance (0.3 mm).

Wideband Circularly Polarized Phased Array Antenna System for Wide Axial Ratio Scanning

This paper proposes the wideband circularly polarized (CP) phased array antenna system for wide axial ratio scanning. For mobile satellite communication, the low profile CP antenna with a wide axial ratio scanning region in wide frequency bandwidth is necessary, but the antenna with the required axial ratio performance is rarely reported. In this paper, the proposed CP phased array antenna system with an axial ratio control scheme has a wide axial ratio scanning region in the wide frequency bandwidth. In the proposed axial ratio control scheme, the amplitude and phase of the received signals are controlled to compensate for the difference between dual polarizations. The proposed antenna system is designed at 5.8 GHz and has a fractional frequency bandwidth of 20%. In a simulation, the axial ratio is under 1 dB at the elevation scanning region from -60∘ to 60∘ at every 360∘ azimuth angle in the operating frequency bandwidth. For validation, the 1x8 CP phased array antenna system was implemented. The measured axial ratio is under 2 dB at the elevation scanning region from -57∘ to 57∘ in the operating frequency bandwidth.

Low‐profile wideband circularly polarized asymmetric dipole antenna with artificial magnetic conductor

In this article, a novel low-profile asymmetric dipole antenna with artificial magnetic conductor (AMC) is presented for wideband circularly polarized operation. First, the asymmetric dipole is adopted to realize a wide impedance bandwidth. By modifying the shape of dipole arms and combing a rhombus-shaped arm with a quasi-triangle-shaped arm, three resonances are achieved by the asymmetric dipole, leading to a wide impedance bandwidth. Second, an AMC surface with square patch units is introduced to reduce the antenna profile to 0.11λ0, where λ0 denotes the lowest operation wavelength in free space. Finally, the presented wideband circularly polarized (CP) antenna design was fabricated and tested. Reasonable agreement between the measurements and simulations is obtained, demonstrating that this CP antenna achieves a 115% impedance bandwidth (1.45-5.4GHz) and a 97% axial ratio bandwidth (1.69-4.88GHz). Within the CP operation band, the presented antenna yields symmetrical and unidirectional radiation patterns with a 6.7-dBic average gain. Such a broadband and low-profile CP asymmetric dipole antenna can be a promising candidate for a wide variety of CP wireless applications.

Low-Profile Circularly Polarized Isoflux Beam Antenna Array Based on Annular Aperture Elements for CubeSat Earth Coverage Applications

This article presents an antenna array to produce a circularly polarized (CP) isoflux beam for CubeSat earth coverage applications. Distinguished from conventional arrays formed by identical elements, the proposed one is based on sequential rotation-fed concentric annular aperture elements. By adjusting the excitation phase, magnitude, and polarization of each annular aperture element, the radiation patterns of the array can be shaped to form isoflux beams. Radiation pattern modeling method is developed to obtain array radiation parameters. Besides, to effectively characterize the impedance matching of the radiators of the array with multiple excitations, an overall reflection coefficient is deduced from signal decomposition. A prototype operating at C-band (5 GHz) is designed, fabricated, and measured. It consists of a radiator and a feeding network. The radiator is formed by two annular aperture elements, of which the inner one is realized by a circular patch antenna while the outer one is formed by eight planar inverted-F antennas (PIFAs). The feeding network drives annular aperture elements in the manner of sequential rotation. In this way, a CP isoflux beam array with a low profile ( 0.078 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ), lightweight, and ease-of-integration for CubeSat is realized. The proposed array can also be extended to realize other shaped beams.

A low‐profile circularly polarized dielectric patch antenna with bandwidth expansion

A new technology for expanding the axial ratio (AR) bandwidth of the circularly polarized (CP) dielectric patch (DP) antenna while maintaining the low-profile characteristic is proposed for the first time. By making full use of the multimode characteristic of the DP resonator, two pairs of degenerate modes (ie, TM101 and TM011, TM121 and TM211) are selected for the broadband design. The key to the proposed technology is that according to the EM field distribution of the two pairs of degenerate modes, four air holes are introduced in the DP and their position and size are elaborately designed to discriminately control the frequency of the two pairs of degenerate modes. Then, these modes become close and are merged to effectively expanding the AR bandwidth of the low-profile CP DP antenna. For demonstration, a prototype centered at about 10 GHz is designed, fabricated, and measured. The measured results exhibit that the proposed CP DP antenna with a low profile of 0.07λ0 owns a 3 dB AR bandwidth of 9.7% and a peak gain of 7.66 dBic. Good agreement is observed between simulated and measured results.

AMC-Loaded Low-Profile Circularly Polarized Reconfigurable Antenna Array

In this letter, a low-profile circularly polarized (CP) reconfigurable printed antenna array employing switching circuits is reported. To realize low-profile design, an artificial magnetic conductor reflector is adopted and loaded at the bottom of the antenna element. Furthermore, in order to meet the high gain and wide bandwidth requirements of S -band satellite communication systems, a 2 × 4 antenna array is also designed. The proposed antenna array has advantages in three aspects: small size with low profile, polarization diversity, and high radiation efficiency. With this method, this antenna array is simulated, fabricated, and tested with reasonable agreement between measurement and simulation.

Fractal and Metasurface Based Low Profile Circularly Polarized Microstrip Antenna

Fractal and Metasurface Based Low Profile Circularly Polarized Microstrip Antenna