Circularly Polarized Slot Antenna Research Articles

A High Gain Circularly Polarized Slot Antenna Array for 5G Millimeter-Wave Applications

An air-filled substrate-integrated waveguide (AF-SIW) circularly polarized (CP) 1 × 8 mm wave antenna array is presented for fifth-generation (5G) applications. The presented slot antenna array consists of three layers of PCB and one layer of aluminum, which serve as the AF-SIW feeding network and the metal cavity radiation element, respectively. The CP characteristic is achieved by the use of an S-shaped aluminum radiation cavity on the top of the AF-SIW feeding network. The air-filled substrate-integrated waveguide technique is unitized to achieve high radiation efficiency. A wide input impedance bandwidth of 18.4% is obtained for the proposed antenna scheme, ranging from 34.5 GHz to 41.5 GHz, with a peak gain of 18 dBic. As for CP characteristic, the proposed antenna possesses a wide 3 dB axial ratio (AR) bandwidth, which is 16.4% (36.5 GHz to 43 GHz). The antenna scheme is fabricated and measured to verify the potential application as well as the promising performance. The measured results of the 1 × 8 antenna array shows that the wide AR as well as the input impedance are simultaneously achieved, which coincide well with the simulated results. Also, the measured results indicate that the proposed antenna scheme might be a good candidate for future mobile applications.

Rotation insensitive implantable wireless power transfer system for medical devices using metamaterial-polarization converter

This article introduces an innovative approach for creating a circular polarization (CP) antenna-based rotation-insensitive implantable wireless power transfer (WPT) system for medical devices. The system is constructed to work in the industrial, scientific, and medical (ISM) frequency band of 902–928 MHz. Initially, a flexible, wide-band, and bio-compatible open-ended CP slot antenna is designed within a single-layer human skin tissue model to serve as the receiving (Rx) element. To form the implantable WPT link, a circular patch antenna is also constructed in the free-space to use as a transmitting (Tx) source. Further, a new metamaterial-polarization converter (MTM-PC) structure is developed and incorporated into the proposed system to enhance the power transfer efficiency (PTE). Furthermore, the rotational phenomenon of the Rx implant has been studied to show how the rotation affects the system’s performance. Moreover, a numerical analysis of the specific absorption rate (SAR) is conducted to confirm compliance with safety regulations and prioritize human safety from electromagnetic exposure. Finally, to validate the introduced concept, prototypes of the different elements of the proposed WPT system were fabricated and tested using skin-mimicking gel and porcine tissue. The measured results confirm the feasibility of the introduced approach, exhibiting improved efficiency due to use of the MTM-PC. The amplitude of the transmission coefficient (|S21|\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$|S_{21}|$$\\end{document}) has improved by 6.94 dB in the simulation, whereas the enhancement of 7.04 dB and 6.76 dB is obtained from the experimental study due to the integration of MTM-PC. As a result, the PTE of the proposed MTM-PC integrated implantable WPT system is increased significantly compared to the system without MTM-PC.

Novel CPW-Fed Gamma-Shaped Circularly Polarized Slot Antenna for UWB Applications

In recent years, ultra-wideband (UWB) technology has garnered significant attention for enabling exceptional precision in applications, such as positioning and radar systems. This letter presents a novel coplanar waveguide-fed circularly polarized slot antenna specifically designed for UWB applications. The proposed antenna incorporates innovative elements, including an asymmetric ground equipped with gamma-shaped slits for circular polarization and a gamma-shaped monopole to enhance reflection coefficients. The overall size of the proposed antenna is 18 mm × 18 mm × 1.2 mm (0.37λ<sub>0</sub> × 0.37λ<sub>0</sub> × 0.02λ<sub>0</sub>). The measurement results demonstrate a reflection coefficient that is consistently below -10 dB from 6.10 GHz to 10 GHz, and an axial ratio below 3 dB from 5.70 GHz to 8.50 GHz. Furthermore, the radiation patterns closely match the simulation results. Additionally, this study analyzes antenna and system fidelity factors using time-domain analysis.

Compact Dual-band CPW-fed Circularly Polarized Slot Antenna for GNSS Applications

Compact Dual-band CPW-fed Circularly Polarized Slot Antenna for GNSS Applications

An ultra‐wideband dual circularly polarized slot antenna with high isolation

SummaryAn ultra‐wideband dual circularly polarized (CP) slot antenna with high isolation is presented. Two L‐shaped probes are on the upper layer, both a ladder strip outside and a bent strip in the center on the bottom layer. The L‐shaped probes and the ladder strip result in four impedance resonance modes, and the bent strip moderates real and imaginary impedances to achieve an ultrawide impedance bandwidth. Furthermore, two L‐shaped strips on the ladder strip make two linear polarized Modes 1 and 2 into two CP modes at the low‐ and mid‐frequency bands. Meanwhile, the bent strip combined with the L‐shaped probes creates the third CP resonance mode at the high‐frequency band. The cutting corner and bent slots on the ladder strip change the amplitude and the phase of the electric fields Ex and Ey to realize ultra‐wideband CP radiation. In addition, the port–port isolation is enhanced because the currents are concentrated on the bent strip, and the coupling current path is cut off with the bent slot. The fabricated antenna achieves a −10‐dB impedance bandwidth of 111% (1.7–5.94 GHz), a 3‐dB axial ratio bandwidth of 101% (1.7–5.2 GHz), and a port–port isolation of better than 20 dB. Besides, our antenna obtains a high peak gain of 8.1 dBi and a lower profile of 0.004 λL, where λL is the lowest frequency wavelength of the operating bands in vacuum. These performances make the proposed design competitive for wireless communications.

An Inductively Coupled CP Slot Antenna Based on Intrinsic 90° Phase Difference and its Flexible Application in Wideband CP Radiation

In this article, a design concept to take advantage of two coupled slots and their inductive coupling to provide the necessary <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$90^{\mathrm {\circ }}$ </tex-math></inline-formula> phase difference for circular polarization (CP) realization is presented. Initially, two individual identical slots are arranged in coupling to each other in a perpendicular position, thus acquiring a pair of orthogonal linear polarization (LP) with equal amplitude. Simultaneously, an inherent <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$90^{\mathrm {\circ }}$ </tex-math></inline-formula> phase difference is naturally produced by the inductive coupling between two slot radiators. In order to clearly illustrate the evolution principle of this proposed CP realization method, the whole structure is in general modeled as an equivalent three-port network for efficient study. Based on these two achieved conditions, a CP slot antenna with one minimum AR point of 4.7% AR bandwidth (ARBW) is satisfactorily realized. After that, based on this proposed design concept, an additional slot is introduced to construct a new inductive coupling, thus facilitating two AR points under triple-mode resonance. With this arrangement, a wideband CP slot antenna with an improved ARBW of 14.1% is successfully implemented, which in turn validates the effectiveness and flexibility of this CP design approach. Finally, both the CP slot antenna element and the wideband CP antenna are implemented, fabricated, and tested. The measured results of the antenna prototypes are found in good agreement with the simulated results, thereby confirming the design concept.

Bandwidth-Enhanced Circularly Polarized Slot Antenna and Array Under Two Pairs of Degenerate Modes in a Single Resonant Cavity

A novel design concept of bandwidth-enhanced full-metal circularly polarized (CP) cavity-backed slot antenna and array based on two pairs of degenerate modes in a single cavity is proposed in this paper. Conventional CP antenna based on one pair of degenerate modes only has one axial-ratio (AR) minima and causes a narrow AR bandwidth. Two pairs of degenerate modes in a proposed multimode cavity resonator can initially produce two separate CP operating bands. Then, a pair of metal prisms is introduced to allocate the two bands in proximity to each other, thus obtaining a wide operating bandwidth with two AR minima. As the radiation slots are directly fed by the electric field of the cavity modes, 2 × 2 cross slots are placed on the top wall so as to comprise a CP array. As such, a very simple wideband CP antenna array is realized by virtue of a single multiple-mode resonator without needing extra power dividers. Finally, the 2 × 2 wideband CP antenna array is fabricated and measured. Measurement shows that the proposed antenna array can achieve 15% bandwidth, a peak gain of 11.8 dBic, and a peak total efficiency of 96%.

Design Approach for a Dual-Band Circularly Polarized Slot Antenna With Flexible Frequency Ratio and Similar In-Band Gain

This letter presents an effective approach to design a dual-band circularly polarized (CP) slot antenna with flexible frequency ratio (FFR) and similar in-band gain under the 0.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</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">$\it\lambda$</tex-math></inline-formula> -mode radiation. Initially, a CP slot antenna is realized in virtue of two orthogonal slot radiators. Then, by folding both slot radiators at a 1/4 length position from the short-circuited terminal, a CP slot antenna operating at two distinct bands is successfully realized based on the 0.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\it\lambda$</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">$\it\lambda$</tex-math></inline-formula> -mode, where stable gain with similar level for the dual working bands is achieved. After that, two pairs of slot stubs are properly introduced to effectively reallocate the higher band based on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\it\lambda$</tex-math></inline-formula> -mode, thus acquiring for a wide frequency ratio ranging from 1.85 to 1.26. Finally, for experimental validation purposes, two specific CP slot antennas with distinctive frequency ratios of 1.85 and 1.26 are implemented and tested. A similar-level gain within their dual operating bands can be achieved as another merit in addition to the FFR.

Simple Slot Antenna With Polarization Diversity

In this letter, a dual-feed circularly polarized slot antenna with polarization diversity is proposed. The proposed antenna consists of a circular slot that acts as a radiator, a dual-microstrip line as a feeding structure, a slit applied to a ground plane (GND), and a protruded stub. The circular polarization (CP) is easily obtained by protruding stub because it acts as perturbation in circular slots. The good isolation between two ports is achieved by the protruding stub and the slit applied to ground plane. From the measured results, the CP operating bandwidth is 22.4&#x0025;. The isolation is less than &#x2212;15 dB within the operating bandwidth.

S-Band Full-Metal Circularly Polarized Cavity-Backed Slot Antenna With Wide Bandwidth and Wide Beamwidth

In this communication, an S-band wide-bandwidth and wide-beamwidth full-metal circularly polarized (CP) cavity-backed slot antenna is proposed. A pair of triangular prisms placed at the corners of the cavity is introduced to produce TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">011</sub> modes with orthogonal electric fields. These two modes are used to achieve the CP radiation and radiate the energy through a single-circular slot. By simultaneously varying the prisms' size and slot radius, the axial ratio (AR) bandwidth (ARBW) improves. The ARBW is further improved by replacing the circular slot with an elliptical slot. As a result, the ARBW increases from 1.0% to 10.3% without complicating the antenna structure and without enlarging the antenna size. Besides, the antenna still operates at two degenerate modes to introduce stable radiation gain and pattern. In addition, the proposed CP slot antenna features a wide ARBW. The final measurement shows that the proposed CP antenna can achieve a 9.5% bandwidth, a stable gain of 7.65 dBic ± 0.15 dBic, and higher than 140° ARBWs in a wide frequency range. The peak total radiation efficiency and aperture efficiency are about 97% and 91%, respectively.

Hexagonal ring electromagnetic band gap‐based slot antenna for circular polarization and performance enhancement

AbstractIn this article, a hexagonal ring electromagnetic band gap (HREBG) structure‐based circularly polarized (CP) slot antenna for improving performance is proposed. The proposed antenna has a compact structure with a low profile of 0.517λo × 0.517λo × 0.055λo (λo stands for the free space wavelength at 5.10 GHz), is coplanar waveguide fed, and comprises of a circular microstrip patch with a T‐shaped slot. An inclined coupling slot loaded feed line is used on the ground for the generation of CP. Furthermore, eight HREBG's are implemented on the substrate to enhance the performance of the antenna, thereby achieving a measured impedance bandwidth of 18%, 3‐dB axial ratio bandwidth of 6.4%, and a peak gain of 5.93 dBi in the operating bandwidth. A close agreement is reached between the experimental results and the simulated results to verify the proposed antenna's performance.

A corrugated G-shaped grounded ring slot antenna for wideband circular polarization

AbstractIn this paper, a wideband circularly polarized corrugated G-shaped grounded ring slot antenna is presented. The proposed antenna structure is excited using a coplanar waveguide-fed monopole antenna, which is placed inside a corrugated G-shaped grounded ring. Due to the asymmetry in the ground plane, two orthogonal modes, having equal magnitude and out of phase by 90° are excited, resulting in circular polarization (CP). The generation of the CP in the proposed antenna structure is explained using thin dipole current element approximation. A prototype of the proposed antenna is fabricated and tested. The measured results exhibit a 3 dB axial ratio bandwidth of 37.6% (2.22–3.25 GHz), and reflection coefficient bandwidth (|S11| ≤ −10 dB) of 47.91% (2.13–3.47 GHz). Additionally, the design guidelines are also presented for G-shaped grounded ring slot antennas.

Broadband Circularly Polarized Rectenna With Wide Dynamic-Power-Range for Efficient Wireless Power Transfer

This paper presents a circularly polarized (CP) rectenna with the advantage of achieving high efficiency in both wide operating power and frequency ranges. The proposed rectenna is composed of a high-efficiency rectifier and broadband CP antenna. In the proposed rectifier, a novel wideband resistance compression technique is presented, highly improving the matching performance of the circuit in a wide range of input power and frequency. The technique is achieved by an impedance manipulation network and a coupled-lines-based resistance compression network (RCN). Theoretical analysis is carried out and closed-form equations are derived for the design of the rectifier. Simulated and measured results show that over 60% (up to 76%) conversion efficiency is achieved for the input power range of 5-17 dBm and frequency band of 1.7-2.9 GHz (mobile, Wi-Fi and ISM bands). Subsequently, unlike the conventional half-wavelength slot antenna, a compact CP antenna with a side length of quarter wavelength is designed by using a 1-wavelength loop slot and a coupled-line-based phase shifter. It has wide axial-ratio bandwidth and good radiation pattern. At last, by integrating the proposed rectifier together with the CP slot antenna, a broadband CP rectenna is completed with higher efficiency by about 18.6% than that without wideband RCN.

A Wideband Circularly Polarized Slot Antenna Backed by a Frequency Selective Surface

A Wideband Circularly Polarized Slot Antenna Backed by a Frequency Selective Surface

A coplanar waveguide fed tilted fractal inspired slot antenna for wideband circular polarization

AbstractIn this article, a coplanar waveguide (CPW) fed 45° tilted fractal inspired slot antenna to achieve wideband circular polarization is presented. A fractal‐square slot is etched from the ground plane and rotated by 45°. The fractal slot is excited by the CPW fed monopole antenna. To achieve wideband circular polarization, asymmetric arm length of the fractal slot is used. The proposed antenna is fabricated and tested. The measured impedance bandwidth (|S11| &lt; −10 dB) is 22.5% (3.6‐4.57 GHz) for Band‐1 and 63.5% (5.1‐10.1 GHz) for Band‐2, and measured 3 dB axial ratio bandwidth is 34.7% (6.37‐9.05 GHz). Experimental results show that the proposed antenna generates right‐hand circular polarization in the +Z direction. Left‐hand circular polarization can be achieved by tilting the fractal slot by −45°.

Differentially Fed Wideband Circularly Polarized Slot Antenna

This communication presents a novel design of a differentially fed wideband circularly polarized (CP) slot antenna. The CP antenna consists of two opposite-fed C-shaped radiating patches and a stub-loaded corner-truncated rectangular slot. With the slot designed to be antisymmetric with respect to the bisection plane and oppositely fed by two microstrip lines, good differential-mode (DM) performance was obtained. On the other hand, the radiations contributed by the corresponding parts of the antisymmetric CP antenna will be destructive when in common-mode (CM) operation. This results in high CM suppression without a preceding CM-rejection bandpass filter. Also, low DM axial ratios (ARs) were achieved by tuning the truncated corner length, the protruded stub length, and the coupling length and gap of the C-shaped radiating patches. The measurement shows that the designed CP antenna has a wide 10 dB DM impedance band of 5–6.49 GHz and a 3 dB DM AR band of 4.94–6.03 GHz, corresponding to a CP fractional bandwidth of 18.7%. Also, in 4.5–6.5 GHz, the proposed antenna can effectively reject CM input signals because the measured CM return loss is smaller than 2.91 dB, and can convert only very little DM input power into CM reflected power since the DM-to-CM conversion is less than −50 dB.

A flexible wide band single fed slot antenna with circular polarizing rotated elliptical ground and impulse response

AbstractIn this paper, a flexible single fed planar circular polarized slot antenna is proposed for Internet of Things wideband applications. The antenna flexibility is achieved by employing a mechanically bendable liquid crystalline polymer substrate. The overall antenna volume is 50 mm × 42 mm × 0.1 mm. The antenna design uses 45° rotated elliptical ground structure for generating circular polarized radiation over wideband spectrum. Two parametrical analyses targeting the slot ground are introduced in order to achieve the most efficient design. The final antenna design demonstrates a good matching in terms of reflection coefficient (&lt;−10 dB), semi-omnidirectional radiation patterns, average gain of 4 dB, and &lt;3 dB axial ratio over entire frequency band of operation. All antenna parameters are studied in both straight and bent antenna setup scenarios. Good agreement between simulation and measurement results of the antenna parameters are achieved. For both straight and bent antenna scenarios, the antenna receiving functionality in time domain is confirmed by retrieving highly correlated impulse responses.

Observation of type‐II kind of correlated photon generation from a classical circularly polarized slot antenna

AbstractIn this communication, an important observation on the generation of the Type II kind of correlated photons at the macroscopic regime is presented. In the optical regime, the entangled photon generation is well established. But, in the microwave (macroscopic) regime there is no any radiator which can radiate two photons of entangled spin states is reported. Accidentally, it is observed that a fundamental circularly polarized slot antenna could radiate photons with correlated spin states in the opposite spatial directions. It is simulated and experimentally observed. The dimensions of the same design could be scaled up or down to use this principle to be implemented at the other frequencies of the electromagnetic spectrum like millimeter waves, Tera Hertz waves, etc. also.

Dual-Band Dual-Sense Polarization Reconfigurable Circularly Polarized Antenna

This letter presents a novel dual-band circularly polarized slot antenna. The far-field polarization of the antenna can be switched electronically between left-hand circular polarization and right-hand circular polarization. A 50 Ω microstrip feed line is divided into four arms those excite a ground plane slot. The p-i-n diodes are introduced in the arms for polarization switching. A prototype dual-band dual-sense antenna with f 01 = 2.4 GHz and f 02 = 5.2 GHz is fabricated using a 1.6 mm thick FR4 substrate. The measured 3 dB axial ratio bandwidths are more than 16.6% and 5.7% at the lower and upper bands, respectively. The measured return loss is more than 10 dB over the wireless local area network (LAN) bands.

A Compact Broadband Circularly Polarized Slot Antenna With Two Linked Rectangular Slots and an Inverted-F Feed Line

In this communication, a broadband circularly polarized slot antenna with an inverted-F-shaped microstrip feed line and two linked rectangular slots in the ground plane is proposed. This antenna offers a wide 3 dB axial ratio (AR) bandwidth in a compact size (previously proposed slot antennas with a similar AR bandwidth are almost double in size) without employing vias or other passive components. Measured AR bandwidth is 83.5% (4.3 and 3–7.3 GHz) which is completely overlapped by the measured $S_{11}$ bandwidth of 92.6% (5 and 2.9–7.9 GHz).