Circular polarization patch antenna design with diagonal periodic metallic via holes

Miniaturization is one of the prime motives in modern communication systems and can be achieved through size reduction of both components and their packages. Whereas passive components are fairly insensitive to packaging, this is certainly not the case for antennas, as the package is located in the nearfield. The paper focuses on the effects of the casing on the radiation characteristics of a miniaturized patch antenna for circular polarization. Different scenarios involving metallic and dielectric casings with planar dielectric overlays are investigated. A circularly polarized microstrip patch antenna has been designed and investigated with respect to effects introduced by the casing. It is found that a metallic casing severely influences the gain and the axial-ratio bandwidth. It also changes the direction of minimum axial ratio. By placing the patch asymmetrically in the casing, the minimum axial ratio can be improved. A dielectric casing has minimal effect on the radiation properties.

In this paper, a novel method to enhance axial ratio bandwidth of circularly polarized (CP) patch antenna using artificial magnetic conductor (AMC) structures with LTCC technology at Ka-band is proposed. In order to improve the axial ratio bandwidth, the traditional PEC plane is replaced by an AMC plane. The AMC is composed of periodic square unit cells with truncated opposite corners. The AMC structure and the antenna are simulated using a full-wave solver and the results show a 10 dB return loss bandwidth of 30% and a 3 dB axial ratio bandwidth of 12.7%, and gain is around 7.5 dB within this band, which compared with the traditional corner-cut square circular polarization patch antenna, the axial ratio bandwidth of proposed antenna increased by 9.5%.

Modern wireless communication devices desire antennas with enhanced performance and low profile. EBG (Electromagnetic Band Gap) surfaces are artificially engineered to improve antenna performance. The performance of a square patch antenna over a 2D-Mushroom EBG ground plane is investigated by comparing patch antenna with conventional ground plane. In this paper, a circular polarized patch antenna resonating at 2.4 GHz, for ISM band applications is designed, fabricated and tested. The antenna is a square patch with truncated edges, exhibiting Right Hand Circular Polarization (RHCP). Circular polarization is crucial to eliminate antenna orientation requirements. Band gap nature of mushroom EBG unit cells are investigated and loaded between patch and the ground plane to eliminate back lobe and improve antenna performance. The mushroom EBG is designed to resonate at 2.45 GHz, with a forbidden band gap of 450 MHz, in-phase reflection band gap of 390 MHz and a high impedance of 3475 Ω at resonance. The introduction of EBG ground plane enhanced the gain to 5.35 dB with an excellent axial ratio at resonance and an operating bandwidth of 7%, with reduction in patch dimensions. The design was simulated in HFSS and tested using VNA after fabrication, resulting in highly correlated results.

The design of dual-pin-fed circularly polarized patch antenna is operated at the microwave frequency of 2.45GHz for Wi-Fi applications. The antenna is designed with square patch. The substrate material used is FR4 and has the relative permittivity of 4.5. It is very difficult to achieve the circular polarization with single feed. However, Dual-Pin Feed is incredibly easy to construct and achieve the circular polarization by exciting at 2 points out of section by ninety degree. The antenna has been designed and simulated by using CADFEKO software. The simulation results show that the antenna resonates at 2.45 GHz with the return loss, impedance and voltage standing wave ratio of −20.7125 dB, 49.027 + i 29.157 and 1.20295 respectively.

A brief review of wideband circularly polarized (CP) patch antennas proposed by the authors' group is presented in this paper. Three kinds of feeding circuits are utilized to widen the bandwidth of CP patch antenna. Firstly, the tap- and coupled-line structures exhibit the intrinsic 90° phase difference. Each of them is connected with a half-wavelength resonator to feed the patch antenna and two axial ratio (AR) minima are achieved consequently. Secondly, λ/4 and λ/2 resonators are employed to design the feeding circuit of CP patch antenna. Two minima in the AR response come up to form wide bandwidth. Thirdly, the feeding circuit consists of one and two λ/2 resonators are designed to achieve three minima in the AR response, resulting in wider bandwidth.

In this paper, a miniaturized circularly polarized (CP) continuous wave Doppler radar system operating at 2.4 GHz is presented. The radar front end consists of one left-handed CP (LHCP) antenna and one right-handed CP (RHCP) antenna, which share a single patch antenna aperture. Orthogonal polarization is achieved through a modified ring-shaped quadrature hybrid coupler (QHC), and the resulting isolation between the two CP antennas is better than 30 dB. With 0 dBm input power to the transmitting antenna, the proposed radar system can accurately detect heartbeat and respiration movements of human test subjects under 1 m and over a wide angular range. The single dual CP antenna achieves 280% size reduction compared to a traditional two linear polarization patch antenna array with the same isolation level.

Characteristic mode theory provides valuable guidance for the mode analysis of a patch antenna. Theoretically, an antenna has infinite OAM modes. However, the practical realization of higher-order OAM antenna is always challenging. This paper presents the design of a sixth-order OAM mode circular polarized single patch ring antenna. A single patch antenna with a phase-shifted power divider network behaves as a multiple-element equivalent model based on its maximum current points. It can generate a higher-order OAM wave. Hence, two orthogonal OAM beams with opposite OAM states of sixth order can be generated from degenerate modes of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$TM_{71}$</tex> mode based on their maximum current points. The proposed antenna operates with good impedance in the frequency range of 5.8 GHz and suits well for RFID and IoT applications in sub-6GHz band.

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 reduced-size wideband single-feed circularly polarized microstrip patch antenna is presented for telemetry applications in S-band around 2.4 GHz. In this paper we compare the performance of microstrip patch antenna designed over two layer conventional substrate with different relative permittivity and different height and over a Reactive Impedance Substrate with slot, both of them being constituted with the same substrate layers. In particular we optimize the feeding position and number of reactive elements upon the antenna bandwidth and axial ratio. The proposed structure consists of a slot-loaded patch antenna printed over an optimized metamaterial-inspired reactive impedance substrate (RIS). We demonstrate, step by step, the main role of each antenna element by comparing numerically the performance of various antenna configurations, antenna over a single layer substrate or dual-layer substrate, patch without slot or slot-loaded patch, antenna with or without RIS. The final optimized structure exhibits an axial-ratio bandwidth of about 15% and an impedance bandwidth better than 10%, which is much wider than the conventional printed antenna on the same materials. The return loss pattern of different microstrip patch antenna with and without RIS arrangement is also compared using HFSS simulation software.

A novel metasurface (MS)-based method for broadband radar cross section (RCS) reduction of circularly polarized (CP) patch antennas is proposed. The RCS reduction is achieved in a much broader band than the operational band of the antenna. The simple technique is based on MS units on a grounded substrate in a checkerboard-like configuration. The broadband RCS reduction is achieved by combining two different destructive interference principles. In the high-frequency region, for a normal incident wave, the RCS is reduced by the phase cancellation generated by the MSs and the grounded substrate. In the low-frequency region, the RCS is reduced by the polarization conversion property of the MS. In this case, the fields reflected by two MS sections are in counter phase for a normal incident wave. The MS is combined with a CP patch antenna. It concerns a traditional corner-truncated square patch and four sequentially rotated surrounding MS cells. This dedicated MS allows two things: an additional resonant mode is excited resulting in a 3 dB AR bandwidth extension from 4.2% to 15.9% and a broadband RCS reduction of over 6 dB from 4.95 to 15.73 GHz (104.25% bandwidth) for both x- and y-polarized incident waves.

In this research, we utilized Ansoft's HFSS v13, which is a Finite Element Method (FEM) based electromagnetic (EM) simulator, to design and analyze two types of patch antennas: a 1x4 circular microstrip patch antenna and a 1x4 hexagonal microstrip patch antenna, operating at 5 GHz. The circular patch antenna was fabricated on a FR4 substrate with a dielectric constant of 4.4dB and a height of 1.6mm. Various antenna characteristics, such as return loss, radiation pattern, directivity, gain, return loss and radiation efficiency, were investigated. The designed 1x4 hexagonal patch antenna and 1x4 circular patch antenna achieved a bandwidth of 3.79% with return loss values well below -30dB. Additionally, a favorable directivity value of 4.5dBi and a gain of 2.7dBi for the 1x4 circular patch antenna and a gain of 3.9dBi for the 1x4 hexagonal patch antenna were obtained. Due to their C-band architecture, these microstrip patch antennas can be employed in various satellite communication applications, such as transponders.

A circularly polarized antenna with wide axial-ratio beamwidth is presented by placing two pairs of parallel dipoles in a square contour. Firstly, our study demonstrates that circular polarization can be achieved at the broadside by setting a 90° phase difference between the vertical and horizontal paired-dipoles. Secondly, the principle of wide-beamwidth circularly-polarized radiation is described under the similarity in polar and azimuthal radiation pattern for a pair of parallel dipoles. After the spacing between two parallel dipoles is studied, the similar radiation patterns in these two orthogonal planes are derived. As such, a wide-beamwidth circular polarization can be achieved by placing the two pairs of parallel dipoles vertically and horizontally while setting a 90° phase difference between them. In final, a circularly-polarized printed antenna is designed and fabricated on a single dielectric substrate. The two arms of its four dipoles are formed on the lower and upper interfaces of the substrate, and they are excited by a 1-to-4 probe-to-microstrip feeding network. Experimental results show good agreement with simulated ones in terms of radiation pattern/gain, axial ratio and returned loss. In particular, the 3-dB axial ratio beamwidth at the central frequency of 1.6 GHz has extended to 126 ° in an angular range from -63° to +63°. The fabricated antenna exhibits a low-profile property with the height of 0.0043 free-space wavelength.

In this communication, dual-fed wideband circularly polarized (CP) patch antennas based on the single-layer printed circuit board (PCB) process and the substrate integrated waveguide (SIW) technology are proposed. Firstly, a patch antenna fed by an SIW coupler is developed to achieve a measured 3 dB axial-ratio (AR) bandwidth of 21% (from 38 GHz to 47 GHz). Then, by introducing second-order inductive windows, an improved CP patch antenna is developed. The measured results show that the 1 dB gain bandwidth is expanded from 3 GHz to 9 GHz while the overlapped bandwidth of AR and reflect coefficient is maintained. Finally, a 2 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\times$</tex> </formula> 2 CP array is developed with a dual-polarized patch array. By carefully selecting the resonant frequency of the patches, a wide gain bandwidth is achieved. Moreover, by compensating the major error that deteriorates the AR bandwidth with a specially-designed coupler, the measured 3 dB AR bandwidth reaches as wide as 22.8%. The measured peak gain is 12.35 dBi.

Reduced-size single-feed circularly-polarized (CP) patch antennas are proposed and investigated based on the strategy of combining meta-surfaces and meta-resonators owning strong space-filling capability. They all comprise a slot-loaded square patch printed over a well designed reactive impedance surface (artificial meta-surface with magnetic response at the resonant frequency) for improved antenna performances and size reduction. The complementary crossbar fractal tree (CCFT) slot and three-turn complementary spiral resonators (TCSRs) with asymmetric gap orientation are employed as meta-resonators to render the antennas to radiate CP waves in single-band or dual-band operation and to facilitate further miniaturization. Numerical and experimental results indicate that these antennas owning a maximum size of 0.262λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.262λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> around 3 GHz exhibit a comparable impedance and axial ratio (AR) bandwidth over 1.05% and high gain of more than 4.15 dBic, predicting promising applications in portable and handheld communication systems.

Cross polarization ratio (CPR) analysis can be used to determine the quality of circular polarization of an antenna as compared to the commonly used axial ratio (AR) analysis. The analysis is independent of E-field left and right polarity measurement which requires two circular polarized reference antennas of left and right. Through CPR, the quality of circular polarization of an antenna can be measured from a reference linear polarity antenna. A low complexity 2.4 GHz circular polarized truncated corner patch antenna is designed and fabricated on printed circuit board (PCB) to show the simple process to analyse circular polarization quality of the antenna. Simulation result is compared to the theoretical considerations and measurement of ratio and E-field results.