Circularly Polarized Array Research Articles

High-Gain Circularly Polarized Array Antenna Based on High-Order Mode ESIC for 5G Millimeter-Wave Application

High-Gain Circularly Polarized Array Antenna Based on High-Order Mode ESIC for 5G Millimeter-Wave Application

Subarray Implementation via Phase Compensation in Circularly Polarized Arrays

Subarray Implementation via Phase Compensation in Circularly Polarized Arrays

Development of a Broadband and High-Gain Circularly Polarized Array of Multilayer Slot Antennas for X-Band Wireless Communication Networks

This paper presents a wideband cavity-backed slot antenna array designed for X-band wireless communication systems. The antenna element consists of a circular slot combined with a cross-slotted patch; both are fed by an L-shaped microstrip line through proximity coupling to extend the impedance bandwidth and gain. The reduction of beam squint in the radiation patterns, caused by the asymmetric feed line, is achieved through intelligent optimization of the dimensions and position of the cross slot on the patch. Additionally, a back cavity is included to provide unidirectional radiation and enhance gain. The antenna exhibits right-hand circularly polarized (RHCP) radiation patterns with high gain over a wideband frequency range. To further improve the axial ratio (AR) bandwidth and gain, the antenna is utilized in a 2 × 2 array configuration with a sequential rotation feed network. The overall dimensions of the proposed array are 1.42 λ 0 × 1.42 λ 0 × 0.45 λ 0 , where λ 0 represents the wavelength at the center frequency of 10 GHz. The fabricated array is then tested, and the measurements show an impedance bandwidth of 60% (7 GHz-13 GHz) with S 11 < − 10 dB, a 3 dB AR bandwidth of 42% (7.45-11.65 GHz), and a peak gain of 11.14 dB. The simulated and measured results exhibit good agreement, validating the effectiveness of the design.

Shared-Metasurface Antenna With Diverse Reflection, Radiation and Polarization Characteristics for Vehicular Communications

This paper presents a shared-metasurface antenna with frequency, directivity and polarization diversities for vehicular communications. The designed metasurface can be simultaneously used as the radiation source of a wideband metasurface antenna, the surface waveguide of a surface-wave antenna and the frequency selective surface (FSS) of a circularly-polarized (CP) array. By placing a printed dipole below the metasurface, the linearly-polarized (LP) broadside radiation in the frequency band of 3.65∼4.58 GHz is realized. Besides, surface waves are excited and supported within the metasurface. Dual quasi-endfire patterns are then generated at two edges from 5.70 to 5.96 GHz due to the discontinuousness. In addition, the broadside CP radiation performance can be realized from 19.45 to 21.85 GHz by placing a CP array below the printed dipole. The designed antenna is simulated and measured. Measured results indicate that the proposed shared-metasurface antenna can be simultaneously applied to the vehicular terrestrial 5G, vehicle-to-everything (V2X) and vehicle-to-satellite (V2S) communications.

Low-Profile Wideband Circularly Polarized Complementary Antenna and Arrays for Millimeter-Wave Communications

Low-profile millimeter-wave (mm-Wave) arrays using wideband complementary element combining circularly polarized (CP) electric and magnetic sources are proposed in this article. A pair of centrosymmetric printed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ {\Gamma }$ </tex-math></inline-formula> -shaped strips serve as a CP electric source, and a modified narrow slot with two etched centrosymmetric stubs can be treated as a CP magnetic source. The combination of them can provide a wide 3 dB axial ratio (AR) bandwidth. Operating mechanism of the proposed CP radiating element is investigated and provided. Two differently constructed CP arrays, i.e., a sequentially rotated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times4$ </tex-math></inline-formula> CP array and a full-corporate fed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> CP array, are then designed based on the proposed CP radiating element, to confirm the expandability of the proposed CP radiating element. Prototypes of these two arrays were fabricated and measured. According to the measured data, the sequentially rotated fed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times4$ </tex-math></inline-formula> CP array exhibits an impedance bandwidth ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{11}\vert &lt; -10$ </tex-math></inline-formula> dB) better than 57.1% (i.e., 25–45 GHz), a 3 dB AR bandwidth better than 31.4% (i.e., 29–40 GHz), and a maximum gain of 16.4 dBic, while the corresponding results for the full-corporate fed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> CP array are 25.8% (i.e., 29–37.5 GHz), 19.1% (i.e., 29.8–36 GHz), and 24.3 dBic. These competitive performances together with merits, such as compact size, low profile, low cost, and direct integration ability, make these two arrays promising candidates for mm-Wave communications.

Low-Cost Broadband Circularly Polarized Array Antenna with Artificial Magnetic Conductor for Indoor Applications

In this paper, we report a sequential-phase fed broadband circularly polarized array antenna loaded with an artificial magnetic conductor-reflecting surface. Our proposed antenna is a two-part group. The upper structure is a sequential-phase fed circular wide-slot antenna. The lower part is an artificial magnetic conductor structured reflective surface. The overall antenna size is 106 × 106 × 14.9 mm3, both adopting 1.6 mm thick FR4 material. The thickness of the air layer sandwiched between the antenna and the artificial magnetic conductor reflective surface is 14 mm. The antenna consists of four circular wide-slot antenna units with a sequential rotation technique. To broaden the axial ratio bandwidth, three L-shaped branches and four metal plates are attached to the circular wide-slot antenna unit and around the artificial magnetic conductor-reflecting surface, respectively. To verify the accuracy of the simulation, we fabricated the sample and then tested it in an anechoic chamber. The measured results demonstrate that the proposed broadband circularly polarized array antenna realizes an impedance bandwidth of 77.67% (2.74–6.22 GHz) and an axial ratio bandwidth of 65.16% (3.00–5.90 GHz) with a peak gain of 11.1 dBi. The design can be used in space-constrained environments, such as indoor and dense building areas.

Analysis and Simulation of a Sequential Rotationally Excited Circular Polarized Multi-Dipole Array for a Bi-Static Antenna GPR for Deep Exploration

As an effective active remote sensing technology for the exploration of shallow underground targets, ground-penetrating radar (GPR) is a detection method that can be used to obtain information about the characteristics of underground targets by transmitting an electromagnetic wave from an antenna and analyzing the propagation of the electromagnetic wave underground. Due to the frequency (1 MHz–3 GHz) of GPRs, the depth of geological exploration is shallow (0.1–30 m). In order to penetrate the deeper Earth, it is necessary to increase the size of the antenna in accordance with the wavelength ratio and, thus, reduce the radiation frequency. For most bi-static antenna GPRs, a dipole antenna is used as the transmitting antenna and another antenna device is used as a receiving antenna, with both being horizontally linearly polarized (LP) antennas. In some cases, such a design can cause problems, such as the multi-path effect and polarization mismatching. When a GPR is used for deep exploration, increased numbers of errors and greater signal attenuation during data reception and processing often occur. In contrast, at the radiation source, with the use of large-aperture multiple-dipole antennas and multi-channel sequential rotational excitation, the electromagnetic wave can radiate in the form of circular polarization at a low frequency. In the receiving antenna, the issues caused by the multi-path effect and polarization mismatching can be addressed, even if LP antennas are used. A novel sequential rotationally excited (SRE) circularly polarized (CP) multiple-dipole array for a bi-static antenna GPR for deep exploration is proposed in this paper. A large-aperture CP multiple-dipole array is used instead of a small-size LP dipole antenna. The analysis and simulation results demonstrated that, comparing circular polarization and linear polarization with the premise of the same transmitting power, the SRE CP multiple-dipole antenna array radiation source achieved a significant enhancement (about 7 dB) in the signal-to-noise ratio (SNR) as the radiant energy was collected at the receiving antenna. More importantly, by reducing the exploration frequency to 10 KHz, the exploration depth could also be greatly increased by about tenfold.

Reconfigurable Full-Metal Circularly-Polarized Cavity-Backed Slot Antenna and Array With Frequency and Polarization Agility

In this brief, reconfigurable circularly-polarized (CP) cavity-backed slot antenna (CBSA) and antenna array with frequency and polarization agility are proposed. Two degenerate modes TE101 and TE011 are respectively perturbed by the metal posts along y-axis (named as MP-1) and x-axis (named as MP-2), and independent frequency tuning is obtained. Then, two crossed slots are placed on the top wall to radiate the electromagnetic energy of TE101 and TE011 modes, respectively. In this context, circular polarization can be realized by setting different lengths of MP-1 and MP-2. Besides, reconfigurable polarization between left-hand and right-hand circular polarization can be realized by exchanging the lengths of MP-1 and MP-2. Meanwhile, reconfigurable operating frequency can be realized by simultaneously increasing or decreasing the lengths of MP-1 and MP-2. In addition, a reconfigurable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4{\times }4$ </tex-math></inline-formula> CP array without introducing power dividers and without increasing the number of tuning metal posts is further investigated. Finally, the reconfigurable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4{\times }4$ </tex-math></inline-formula> CP array is fabricated and tested. Reconfigurable frequency, reconfigurable polarization, high total efficiency, and stable radiation pattern are simultaneously obtained. Good agreement between measured and simulated results well validates the proposed design concept.

A Novel Decoupling Feeding Network for Circularly Polarized Patch Arrays Using Orthogonal Mode Decomposition

A new decoupling feeding network (DFN) is proposed for circularly polarized (CP) patch arrays with an arbitrary number of elements. Different from linearly polarized (LP) patch arrays, a dual-feed structure is adopted for each element to enhance the CP performance. The dual-feed structures should be integrated into the DFN, and hence the coupling paths become very complicated. An orthogonal mode decomposition (OMD) method is established to analyze the coupling mechanism between the CP patch elements. Based on the OMD, a network model of the mutual coupling between the CP patch elements is established, which can be used to assist design of the DFN. To verify the decoupling effect, a prototype of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times $ </tex-math></inline-formula> 2 CP patch array for a satellite navigation system is fabricated and measured. After applying the DFN, mutual coupling between all ports is reduced to below −33 dB at the center frequency of 1.26 GHz, and the decoupling effects reach 15–23 dB. The CP patch array maintains stable radiation patterns with a realized gain of ~9.4 dBi. The proposed OMD approach is applicable to other CP arrays with an arbitrary number of elements.

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%.

Wideband High-Gain Circularly Polarized Substrate Integrated Cavity Antenna Array for Millimeter-Wave Applications

A wideband high-gain circularly polarized (CP) substrate integrated cavity (SIC) antenna array is presented for millimeter-wave applications. The proposed antenna element is simply composed of a slot-coupled high-order-mode resonant square SIC and a pair of obliquely placed strip-shaped parasitic patches on the top surface of the SIC. The parasitic patches are used to adjust the aperture electromagnetic field distribution and phase of the two orthogonal resonant modes of TM211 and TM121 in the SIC to achieve a high-gain CP radiation and meanwhile introduce an additional cavity-backed slot-dipole CP radiation to extend axial ratio (AR) bandwidth of the proposed antenna element. By combining the above two high-gain CP radiation mechanisms, a wideband high-gain CP SIC antenna element is achieved. The simulated results of the proposed antenna element show an overlaid bandwidth of 20.36% from 26.20 to 32.14 GHz, while considering the −10 dB reflection coefficient, 3 dB AR, 3 dB gain bandwidths properties, and a maximum right-hand CP gain of 10.53 dBi at 29.40 GHz. On this basis, a wideband high-gain 8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 8 CP array fed by a full-corporate substrate integrated waveguide (SIW) network is designed and fabricated. The measured results show that the proposed array has an overlaid bandwidth of 21.72% from 25.85 to 32.15 GHz and a measured gain of up to 26.10 dBic at 29.00 GHz.

Circularly Polarized Elliptical Cavity-Backed Patch Antenna Array for Millimeter-Wave Applications

This work introduces cost-effective solution for a millimeter-wave (mmW) antenna array development. We suggest an elliptical cavity-backed patch antenna array to achieve a wideband and high-gain circularly polarized (CP) at mmW frequencies. The whole array only uses two PCBs and a metallic fixture to build. We introduce a new configurable subarray with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times $ </tex-math></inline-formula> 1 radiating elements that are formed by two partially overlapped elliptical cavities to generate the radiation together with the driven patches of the subarray. The subarray can produce a wide impedance bandwidth of 37%, a wide 3 dB axial ratio (AR) bandwidth of 29.6%, and a maximum gain of 11.6 dBic. Based on the result from the subarray, we design a 32-element antenna array by a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4 \times $ </tex-math></inline-formula> 4 antenna array configuration. The power distribution is realized by a 1-to-16 full-corporate feed network. The measured results show that the proposed CP array obtains an impedance bandwidth of 31.5% and a 3 dB AR bandwidth of 24%. In addition, the gain of the array is from 19.1 to 21 dBic within the 3 dB AR bandwidth. With wide impedance and AR bandwidths, the proposed antenna array can find potential applications in long-range mmW communications.

A low‐profile sequential‐phase fed circularly polarized array antenna with an irregular ground

Grooving or subtracting a projection of the antenna on the ground is one of the effective methods to both improve the axial-ratio (AR) bandwidth and impedance bandwidth of a circularly polarized (CP) antenna. A bidirectional radiation, meanwhile, can be produced. Unfortunately, these methods will result in a decrease in the gain of the antenna due to a reduction of its ground size. To solve this issue, a conductive plane or a cavity is usually introduced at the antenna's bottom, but it will lead to a high profile and destroy the bidirectional radiation of the design. In this article, a CP array antenna based on a sequential-phase (SP) feeding network is taken as an example. Only the projection of the feeding network is preserved, while other conductors on the ground are subtracted. The simulated peak gain of this design is only 5.04 dBic. In order to obtain an ultra-wideband, a wide AR bandwidth, a moderate gain and a low profile of the antenna, a method of etching a circle of ground around the edge of the substrate is presented to expand the ground into a large irregular area. The measured results show that the proposed design can exhibit a 90.9% 10-dB impedance bandwidth, a 42.4% (5.2–8 GHz) 3-dB AR bandwidth, a 7.17 dBic peak gain, and a very low profile of 0.006λL. This method is very simple to implement and does not need to modify the original antenna structure. It may be applied to conveniently improve the performance of the bidirectional radiation CP antenna.

A Novel Design of Flat-Top Beamforming Anti-Multipath Antenna

This article discusses a novel design method of wide-beam circular polarization array antenna for satellite navigation. For special applications such as satellite navigation guiding aircraft landing, high-performance ground reference station antennas are required. In the system of satellite navigation guiding aircraft landing, the antenna of satellite navigation receiver needs to have the following radiation characteristics: the shape of antenna pattern is close to an ideal hemisphere, the upper half of space has uniform right-hand circular polarization gain, and the beam has the characteristic of sharp cutoff below 5 degrees of elevation. Whether the GNSS reference station antenna can have a wider beam circular polarization characteristic to receive more navigation satellites signal; whether it can suppress the multipath effect to a greater extent to reduce the multipath error; and whether it can work in a wider frequency band, so that several major satellite navigation systems work together, the above factors directly affect the satellite navigation and positioning accuracy of the entire system. The beam of this antenna has the following feature: sharp cutoff near the horizon for multipath mitigation at low elevation angles. Comprehensive design thereby accelerates system design. It owns wide beam, good circular polarization characteristics, low elevation angle sharp cutoff, and ultralow sidelobe radiation characteristics that achieve the purpose of receiving satellite navigation signal and multipath. The low sidelobe characteristic of the antenna is beneficial to suppress multipath effect. According to the theoretical knowledge of the symmetrical dipole and the four-arm helical antenna, the simple structure of the symmetrical element is fully utilized, and the printed balun easily realizes the dual-frequency operation of the antenna. Combined with the wide-beam circular polarization characteristic of the four-arm helical antenna structure, the shaped beam array antenna is designed. The wide-beam circularly polarized antenna unit not only covers the frequency band of the satellite navigation system but also satisfies the system performance and key feature requirements of the array antenna for the unit; that is, it satisfies the wide-beam circular polarization characteristics of the upper half space. According to the linear array basic theory and array antenna synthesis theory, Woodward Lawson sampling synthesis algorithm is used to synthesize the array amplitude and phase weights corresponding to the specific antenna pattern required for the Ground-Based Augmentation System (GBAS) engineering. The shaped beam array antenna consists of 21 units, of which 11 antenna units are directly fed, and the feeding ports of the rest are dummy ports. It is an equally spaced array antenna. The spacing between antenna units is close to half wavelength. They are fed according to the value corresponding to the excitation function. The array antenna is simulated by HFSS (High-Frequency Structure Simulator). Compared with traditional satellite navigation antennas, the antenna in this paper has excellent front-to-rear ratio and flat-top beam pattern. The results show that the wide-beam circularly polarized array antenna meets the engineering requirements of GBAS applications and lays the solid foundation for GBAS engineering applications.

Wide Bandwidth Axial Ratio Circularly Polarized Array Antenna based on External Resonator

This study introduces a wide bandwidth and wide axial ratio (AR), circularly polarised (CP), patch array antenna. By combining dual layers of a polarizer with dual layers of linearly polarized microstrip patch antenna, a novel method is created for generating circular polarization waves with a wide frequency range. The dual-layer 2 × 2 and 2 × 8 microstrip patch array antenna is employed to achieve linearly polarized waves and the external polarizer consists of a 3 × 3 and 3 × 12 four-layer dual rings polarizer that transforms linearly polarized (LP) waves into CP waves. The |S11| −10 dB bandwidth of small and large-scale circular polarized array antennas is 20% and 27.06% at 5 GHz, respectively, Simulations and testing show that the 3-dB axial ratio bandwidth (ARBW) at 5 GHz is 17%. The suggested antenna has a lot of potential for satellite communication applications because of its easy structure, wide ARBW, and wide impedance bandwidth.

A Low-RCS and Wideband Circularly Polarized Array Antenna Co-Designed With a High-Performance AMC-FSS Radome

In this letter, we investigate a low radar cross-section (RCS) wideband circularly polarized microstrip array antenna co-designed with a high-performance artificial magnetic conductor and frequency selective surface (AMC-FSS) radome. Compared with the absorbent frequency selective radome-based antenna, the proposed co-designed antenna can achieve a relatively low gain loss in an extremely wide frequency range with wideband in-band and out-of-band RCS reduction, due to the introduction of a novel AMC-FSS radome which can achieve low insertion loss and wideband transmission by combining a double-layer miniaturized bandpass FSS and a single-layer chessboard AMC surface. We demonstrate the effectiveness of the proposed AMC-FSS radome and co-designed antenna through simulations and measurements. The results show that the gain deterioration of the co-designed antenna is only 0.42 dB at the central frequency of 4.8 GHz and less than 1 dB in the wide frequency band, ranging from 4.23 to 5.38 GHz with a relative bandwidth of 23.9%. At the same time, the monostatic RCS for a normal incidence is greatly reduced from 4 to 18 GHz.

Broadband Millimeter-Wave Endfire Circularly Polarized Array With a Low-Profile Feeding Structure

In this communication, a broadband endfire circularly polarized (CP) antenna with a low-profile feeding structure is proposed for millimeter-wave (mmW) applications. The array element consists of a horizontally oriented printed electric dipole and a vertically aligned tapered slot radiator, exciting two orthogonal radiated electric-field components simultaneously. The amplitude and phase relationships between these two field components can be adjusted by balancing the response of the tapered slot and dipole radiators, thereby producing a CP radiated wave. Importantly, a parasitic director is introduced near the printed dipole to compensate for the gain degradation of the dipole element at higher frequencies, thus significantly expanding the axial ratio (AR) bandwidth of the CP element. Compared with other reported endfire CP antennas, the proposed antenna owns a lower profile of feeding substrate (0.508 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 0.056~\lambda _{0}$ </tex-math></inline-formula> ), making it amenable for convenient integration with planar front-end circuits. As a demonstration, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times8$ </tex-math></inline-formula> array prototype is designed and measured, exhibiting an impedance bandwidth of 42.1% (27.45–42.1 GHz) and a 3 dB AR bandwidth of 35.8% (27.5–39.5 GHz). The demonstrated CP array is a promising candidate for wideband mmW applications due to its advantages of wideband, ease of integration with planar circuits, and low fabrication cost.

Broadband Circularly Polarized Magnetoelectric Dipole Antenna and Array for K-Band and Ka-Band Satellite Communications

A circularly polarized (CP) magnetoelectric dipole (ME-dipole) antenna with a wide impedance bandwidth and 3 dB axial ratio (AR) bandwidth is proposed. The antenna is fed by a microstrip line and coupled through a modified cross-slot on the ground plane. Based on the conventional linearly polarized (LP) ME-dipole, the proposed electric dipoles and the coupling slots are modified to generate the CP radiation. Simulated results of the antenna element show an impedance bandwidth of 72.8% from 16.35 to 35.08 GHz and a 3 dB AR bandwidth of 39.2% from 21.53 to 30.07 GHz. To enhance the gain of the antenna for practical application, a 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 4 antenna array with full-corporate feeding network is designed, fabricated, and measured. The measured results show that an impedance bandwidth of 66.95% from 17.26 to 34.63 GHz and a 3 dB AR bandwidth of 41.1% from 19.25 to 29.25 GHz are achieved. The proposed antenna can be applied to K-band, Ka-band satellite communications or fifth-generation (5G) millimeter wave (mmWave) communications at n257 (26.5–29.5 GHz) and n258 (24.25–27.5 GHz) bands.

Wearable Wideband Circularly Polarized Array Antenna for Off-Body Applications

A wideband circularlypolarized (CP) wearable antenna for 5 GHz (5.15–5.825 GHz) wireless body area network is presented and analyzed. The emphasis of this work is on the additional resonance generated by the mutual coupling of a 2×2 compact patch array. As the proposed antenna is fed by a sequential-phase feeding network, the resonance can be used to achieve unidirectional radiation with improved CP bandwidth. To alleviate the loading effects of the human body, a modified strip feedline, comprising two pairs of arc-shaped slots cut on the bottom ground, is introduced. Moreover, the adoption of textiles as substrate and conductor provides flexibility and conformability, allowing the antenna to be integrated with garments. The prototype with the dimensions of 40 mm × 40 mm × 4 mm (0.73 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.73 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.07 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) was fabricated. The measured results indicate that a wide impedance bandwidth of 43% (4.25–6.63 GHz), a half-power beamwidth of 60°, and a 3 dB AR bandwidth of 34% (4.71–6.67 GHz) are achieved. Furthermore, the antenna performance is proved to be stable under structural deformation and human body loading. Finally, transmission losses and link budgets are evaluated, enabling the antenna to be a robust solution for off-body communications.

A Single-Layer Dual-Band Dual-Sense Circularly Polarized Patch Antenna Array With Small Frequency Ratio

A planar dual-band dual-sense circularly polarized (CP) microstrip array is proposed. This array is implemented on a single-layer substrate and easily extended to the design of a larger array. A new antenna element is exploited by symmetrically placing the nonradiative resonators on four side edges of a square patch. A quantitative design method is proposed based on the equivalent circuit model of the antenna element. For given two operating frequencies, the required design parameters of the patch and nonradiative resonators can be calculated. Theoretical magnitude ratio and phase difference responses of two far-field components, as well as axial ratio responses under different parameters, are presented to reveal the characteristics of the antenna element. Full-wave simulation results are found to agree well with the theoretical ones. To further validate the effectiveness, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 \times 2$ </tex-math></inline-formula> element dual-band dual-sense CP array operating at 2.40 and 2.68 GHz is designed, fabricated, and measured, where a small frequency ratio of 1.117 is achieved. The measured realized gains in the low and high bands are 11.7 and 11.8 dBi, respectively, which are approximately equal.