Circularly Polarized Array Research Articles

Low-Cost Millimeter-Wave Circularly Polarized Planar Integrated Magneto-Electric Dipole and Its Arrays With Low-Profile Feeding Structures

A low-cost millimeter-wave circularly polarized (CP) planar integrated magneto-electric dipole (ME-dipole) element with simple structure is proposed, which is fed by a low-profile feeding structure capable of being directly integrated with Ka -band front-end circuits. Two rotationally symmetrical L-shaped patches are adopted to replace the two straight arms of the original linearly polarized ME-dipole to generate a rotated electric field, thus radiating CP waves. Based on this CP ME-dipole element, CP array antennas containing 2 × 2 and 4 × 4 radiators with low-profile full-corporate feeding networks are developed without any additional dielectric layer. Prototypes of these two CP array antennas are fabricated and measured. Good agreement between the simulated and measured results is achieved, validating the correctness of these two designs. The 2 × 2 array exhibits a | S 11| Ka -band satellite communications, etc.

Low‐cost and wideband circularly polarized slot antenna array

A slot antenna with wideband circular polarization (CP) array, which operates on millimeter waves band, is proposed. A four-direction sequential rotation technique is used in the feed network to feed the 2 × 2 slot element based on waveguide. The shot element resonates at both the fundamental mode and the high-order mode. The slot element is studied in high order mode, and the radiation lobe can be redirected by changing the size of the slot element, thus improving the multi-lobe problem. A strong single lobe is formed in the +z-direction by using the ground edge diffraction characteristics of the slot element in the waveguide. The designed broadband characteristics are obtained through the appropriate combination of the feed network and CP antenna. The prototype of the antenna with an overall size of 137 mm × 137 mm × 0.6 mm3 is processed and verified by experiments. The prototype of the slot array is processed and examined. The test results display that the device has good performance of |S11| < −10 dB bandwidth of 3.72 to 6.56 GHz (2.84 GHZ, 55.25%), a 3 dB axial ratio bandwidth of approximately 4.39 to 5.43 GHz (21.18%).

Analysis and Design of Ultrawideband Circularly Polarized Antenna and Array

This article presents the design and analysis of an ultrawideband (UWB) circularly polarized (CP) antenna element and its array. First, an UWB CP antenna element using circular-arc-shaped monopole (CASM) with asymmetric ground plane is proposed. Characteristic mode analysis (CMA) is used to investigate its CP operating mechanism, providing physical insights into different modes (mode currents and characteristic radiation fields) at various frequencies. The CMA results show that the asymmetric ground plane makes great contribution to produce CP radiation in the lower frequency band, while another upper CP band is generated by CASM. Thus, the overall 3 dB axial ratio bandwidth (ARBW) of the element can be significantly expanded. Furthermore, a $2 \times 2$ UWB CP array is designed based on this element. A gradient artificial magnetic conductor (GAMC) with a metal cone is adopted to realize both a low-profile ( $0.1 \times \lambda $ , where $\lambda $ is the air-free wavelength at lowest frequency) and the high-gain radiation for the first time. To validate this novel configuration, this array is fabricated and measured. The measured bandwidth ( $\vert S_{11} \vert dB, AR < 3 dB) is approximately 92.3% (1.75–4.75 GHz). It also achieves a wide 3 dB gain bandwidth of 72.3%. Both the simulated and measured results demonstrate that this low-profile high-gain antenna array is promising for applications in wireless systems such as mobile satellite communication system.

A unidirectional ultra‐wideband circularly polarized spiral antenna array

AbstractThis paper studies a unidirectional ultra‐wideband circularly polarized (CP) spiral antenna array. The ultra‐wideband high‐gain CP operation is realized by implementing four‐element sequentially rotated spiral array antennas fed with an ultra‐wideband feeding network. Tapered multisections power dividers and broadband microstrip‐slot phase shifters are utilized to provide accurately equal power division and constant phase shifts of 90°. In order to further improve the CP operating bandwidth, foam of absorber is adopted between the radiating aperture and the feeding network substrate. The proposed CP array is designed, fabricated, and measured. Test results show that the impendence bandwidth of the proposed array covers 2.2 to 11.6 GHz (5.3:1) and 3 dB axial‐ratio bandwidth covers 2.3 to 13 GHz (5.65:1), demonstrating a stable CP array performance within an ultra‐wide working bandwidth.

A Wideband Circularly Polarized Connected Parallel Slot Array in the Presence of a Backing Reflector

This paper presents a wideband circularly polarized (CP) connected parallel slot array that basing on the Wheeler’s infinite current sheet concept. The proposed wideband CP array composes orthogonally arranged equivalent magnetic currents with approximately 90° phase difference. Connected parallel slot structure is adopted here to obtain low active input impedance of the array unit cell and realizes good impedance matching without using any extra balun. Shorted microstrip lines and curved phase shift line are used as the feeding. Furthermore, to avoid the backing radiation and keep unidirectional radiation, a metal reflector is added below the array aperture. Then, the connected slot shapes were modified to expand both the impedance and axial ratio (AR) bandwidth. From simulation, the infinite array achieves approximately 3.18:1 impedance bandwidth (from 1.57 to 5 GHz) with active VSWR ≤ 3 and 2.4:1 AR bandwidth (from 1.64 to 3.93 GHz) with AR ≤ 3 dB. A $4 \times 4$ CP connected parallel slot array was designed, fabricated and measured to verify the design concept. The measured results reveal a wideband CP performance and unidirectional radiation. Benefiting from the utilization of the backing reflector, the front-back-ratio of the $4 \times 4$ array is larger than 15 dB and the realized gain approaches the ideal aperture directivity.

Pattern-Reconfigurable Array Based on a Circularly Polarized Antenna With Broadband Operation and High Front-to-Back Ratio

A design for single-fed circularly polarized (CP) antennas with broadband operation and high front-to-back ratio is first described. The antenna is mainly composed of a monopole slot, a dipole, and a metallic box. When the monopole slot is operated in its half-wavelength mode, the radiated fields of the slot and dipole have the same amplitudes and 90° phase differences; in addition, the two radiating elements are arranged in an orthogonal configuration. Consequently, a CP radiation is obtained. Then, the CP antenna is adopted as a radiating element of a 3-D array, and a feed network composed of power dividers is used to excite the array. Both the simulated and measured results prove that the CP array can give a nearly omnidirectional pattern, bidirectional patterns with 8 dBi directivity, and scanned beams with a directivity of 11 dBi. Moreover, the half-power beamwidth of the scanned beam can be changed among 48°, 124°, and 240°. The total size of the array is about $1.5\lambda _{0} \times 1.5\lambda _{0} \times 2.5\lambda _{0}$ . Details of the designs for the CP element and array are presented.

Low-Profile Circularly Polarized Array With Gain Enhancement and RCS Reduction Using Polarization Conversion EBG Structures

A planar antenna array based on checkerboard polarization conversion electromagnetic band-gap (CPC EBG) structures with wideband circular polarization and low radar cross section (RCS) is presented. The array is formed by $2\times 2$ circularly polarized (CP) element antennas fed with a sequential feeding network. On the one hand, CP radiation is obtained due to the polarization conversion characteristic of the metamaterials. A sequentially rotated feeding network is employed for wide operating bandwidth, polarization purity, and radiation pattern symmetry. The measured results show that the array has a wide usable bandwidth of 18.4%, the common part of an impedance bandwidth of 37.3% (4.80–7.00 GHz), a 3 dB axial ratio (AR) bandwidth of 22.5% (5.00–6.27 GHz), and a 3 dB gain bandwidth of 18.4% (4.94–5.94 GHz). On the other hand, the checkerboard arrangement of the EBG structure generates both an in-band and a partial out-band RCS reduction under normal incidence for both $x$ - and $y$ -polarizations. Besides, the proposed array achieves a significant gain enhancement compared to the traditional slot array. The experimental and simulated results are in good agreement.

Wideband High-Efficiency Circularly Polarized SIW-Fed S-Dipole Array for Millimeter-Wave Applications

A wideband high-efficiency millimeter-wave (mm-wave) circularly polarized (CP) array which is constituted by novel planar substrate integrated waveguide (SIW)-fed S-dipoles is presented in this communication. The proposed mm-wave CP S-dipole consists of two rotational symmetric curved arms and is fed differentially through aperture coupling, which features simple configuration and excellent performance. Detailed analysis is given to explain the operating principles of this element. It is noted that superior element performance including a wide impedance bandwidth of 43%, a wide 3 dB axial ratio (AR) bandwidth of 36%, and 1 dB gain bandwidth of 38% is achieved by the planar SIW-fed S-dipole. By feeding 64 in-phase S-dipole elements through a full-corporate SIW feeding network, a planar wideband highly efficient mm-wave $8 \times 8$ CP array is realized. To verify the design concept, a prototype operating at Ka-band is fabricated and measured. The measurement results indicate that the proposed array achieves a wide overlapped bandwidth of 27.6%, a high antenna gain of 25.2 dBic, and a high aperture efficiency of 89.9%. Attributed to the planar and robust array structure as well as its excellent performance, the presented array is a good candidate for various mm-wave applications.

Circularly Polarized 2 Bit Reconfigurable Beam-Steering Antenna Array

In this communication, a circularly polarized (CP) reconfigurable 2 bit antenna array is proposed for beam-steering applications. The proposed antenna array utilizes a novel CP reconfigurable 2 bit patch antenna as radiation element. For a reconfigurable 2 bit element, there should be four phase states (i.e., 0°, 90°, 180°, and 270°). In the proposed radiation element, a corner truncated microstrip patch antenna is presented for CP radiation. Owing to the symmetry of the patch antenna, the 0° and 180° phase states are achieved by selecting feeding points of the patch instead of using complex feeding network. A 90° digital phase shifter is cascaded to realize the 90° and 270° phase states for the 2 bit reconfigurable element. Based on the novel 2 bit CP element, an eight-element CP reconfigurable 2 bit antenna array is fabricated and tested to verify the design strategy at 3.65 GHz. The measured results match well with simulation. By appropriately controlling the ON and OFF states of p-i-n diodes, the proposed CP array can be steered from −49° to +49°.

A high‐gain compact circularly polarized microstrip array antenna with simplified feed network

A broadband high-gain circularly polarized (CP) microstrip antenna operating in X band is proposed. The circular polarization property is achieved by rotating four narrow band linearly polarized (LP) microstrip patch elements in sequence. Since the conventional series-parallel feed network is not conducive to the miniaturization of the array, a corresponding simplified feed network is designed to realize the four-way equal power division and sequential 90° phase shift. With this feed network, the impedance bandwidth (IBW) of the CP array is greatly improved compared with that of the LP element, while maintaining a miniaturized size. Then, parasitic patches are introduced to enhance the axial ratio bandwidth (ARBW). A prototype of this antenna is fabricated and tested. The size of proposed antenna is 0.93λ0 × 0.93λ0 × 0.017λ0 (λ0 denotes the space wavelength corresponding to the center frequency 10.4 GHz). The measured 10-dB IBW and 3-dB ARBW are 13.6% (9.8-11.23 GHz), 11.2% (9.9-11.07 GHz) respectively, and peak gain in the overlapping band is 9.8 dBi.

A Wideband Circularly Polarized Array Antenna With Compact and High-Efficiency Feeding Network

A wideband circularly polarized (CP) waveguide array antenna is proposed in this article. The proposed array antenna consists of four antipodally ridged elements and a compact feeding network with two orthogonal septa inserted to a stepped cavity. Both the components are wideband and they can work independently or together. The proposed topology gives a good solution to feed a $2 \times 2$ waveguide subarray which is the basis of large-scale arrays. It exhibits a larger working bandwidth than the array antennas fed by high-order mode cavities. A prototype is fabricated using 3-D printing and milling technologies. Measured results demonstrate a bandwidth of 40.3% from 9.9 to 14.9 GHz, in terms of the reflection coefficients less than −15 dB and the axial ratios smaller than 3 dB. An expanded $8 \times 8$ CP array antenna is explored based on the proposed $2 \times 2$ subarray to show the potentials of our design, and a total efficiency over 78% within a bandwidth of 38.7% is obtained by simulation.

Millimeter-Wave Circularly Polarized Array Antenna Using Substrate-Integrated Gap Waveguide Sequentially Rotating Phase Feed

A substrate-integrated gap waveguide (SIGW) sequentially rotating phase (SRP)-fed 2 × 2 circularly polarized (CP) patch antenna array is presented for the wideband millimeter-wave application. The antenna element is composed of a truncated square patch, SIGW feedline with three layers of printed circuit board (PCB), and another layer of PCB with an air hole for supporting radiation patch. Each radiation patch is driven by an underneath coupling slot etched on SIGW. A wide axial-ratio (AR) bandwidth is achieved by deploying a 2 × 2 SIGW SRP feed network. Moreover, simple calculation expressions of the characteristic impedance and guide wavelength of SIGW are given for the design of SRP feed network. The fabricated prototype shows an impedance bandwidth of 25.6% covering 22.2–28.8 GHz, 3 dB AR bandwidth of 19% from 22.8 to 27.6 GHz, and peak gain of 11.53 dBic.

Modification of metasurface‐based CP array antenna by using cascade feed network

In this work, a unique compact size high gain circularly polarised (CP) array antenna is proposed. The array is considered as a 2 × 2 metasurface-based CP patch antennas which fed by a cascade network. The single element consists of two different layers of substrate that metasurface layer excited by aperture slot on metallic ground layer in middle layer between metasurface cells and microstrip line, meanwhile this layer isolates destructive effects of feed lines on radiation layer. For achieving high gain at a compact size several techniques such as (i) use of broadband feed network, (ii) utilising of adjacent cells with unique structure as mutual coupling reducer, and etc. have been simultaneously applied. In order to validation of simulated parameters the proposed array has been fabricated and measured. The measurement results for the proposed compact size array antenna are the impedance bandwidth (| S 11 | <; -10 dB) of 4.22-7 GHz (49.55%), a 3-dB axial ratio bandwidth of 4.71 to 6.28 GHz (28.5%), and a peak gain of 16.57 dBic at 5.5 GHz.

A Versatile Triangular Patch Array for Wideband Frequency Alteration With Concurrent Circular Polarization and Pattern Reconfigurability

This paper focuses on the design with experimental verification of a circular polarization (CP) and pattern reconfigurable triangular patch array simultaneously operating at various tunable frequencies. The resonant frequency of the antenna can be altered from 1.97 to 2.54 GHz (25.3% tunable bandwidth) by varying the capacitance values from 4.27 to 1.15 pF of the six varactors fixed between the annular slots on the three triangular patches. A wideband phase shifting network with switching capability is also designed which facilitates the antenna to operate it in both types of CP and pattern reconfigurable modes at each frequency. The antenna is tested in receiving mode and it shows a maximum realized gain of 3.1 dBc when operated in any of the CP mode and 1.45 dB for pattern reconfigurability mode. It has a very wideband axial ratio (AR) value (<3 dB) at each reconfigured frequency and also covers the entire frequency agility bandwidth. Investigation confirms that the antenna produces circularly polarized radiation pattern with minimum AR beamwidth of 24° at all frequency bands for both types of CP radiation. It is also observed that the antenna pattern can be rotated at 120° angle in the complete azimuth plane with a wide 3 dB beamwidth of ±45° at its operating frequencies. The multifaceted reconfiguring ability of the antenna enables it to serve many futuristic communication system requirements such as supporting multiple radios and maintaining signal quality in diverse climatic conditions.

45 GHz Wideband Circularly Polarized Planar Antenna Array Using Inclined Slots in Modified Short-Circuited SIW

This paper presents a $Q$ -band planar circularly polarized (CP) antenna array with a wide bandwidth, in terms of both impedance matching and axial ratio (AR). A centered 45°-inclined slot in the broad wall of a substrate-integrated waveguide (SIW) with a modified short-circuited termination is first introduced to realize a wideband 45° linearly polarized radiation, incorporated with a pair of inductive vias for impedance matching. Then, orthogonally integrating two proposed slots with an SIW 90° directional coupler, a wideband CP element is designed and its beam exhibits a good AR over a relatively wide angular region in one direction. Following this, a two-layer SIW is employed to design a CP antenna array. Four CP elements are arranged in a rotational manner in the top layer, and they are sequentially fed by a four-way power divider in the bottom layer with an incremental phase delay of 90° to achieve a conical CP beam and higher gain. The performances of the power divider and cross-layer coupling slot are examined in the wide operating band. The proposed CP array antenna is prototyped at $Q$ -band, and measured results show that the antenna has $\vert S_{11}\vert dB, AR $\times \,\, 30$ mm $\times \,\, 1$ mm.

Dual-Polarized Communication Rectenna Array for Simultaneous Wireless Information and Power Transmission

A dual-polarized communication rectenna array with high isolation and low cross polarization for simultaneous wireless information and power transmission (SWIPT) is presented. It consists of a 2 × 2 element receiving antenna array and a high efficiency rectifier based on voltage doubler topology. The receiving element is corner-fed to achieve high isolation of more than 20 dB between the dual-polarized ports, which guarantees low mutual interference between the communication and the rectifying ports. To receive enough electromagnetic (EM) wave for rectifying and meanwhile meet the communication sensitivity, this 2 × 2 array uses its 2 × 2 vertical polarization ports and 1 × 2 horizontal polarization ports for power rectifying, and the rest 1 × 2 horizontal polarization ports for communication. For the communication port, the measured gain is 10.9 dBi and the cross polarization is less than -20 dB. The performance of the whole communication rectenna array has been measured, where a 2 × 4 circularly-polarized array with a gain of 17.5 dBi, settled 1 meter away is used as the transmitter. Measured results show that the system achieves a peak microwave - direct circuit (mw-dc) conversion efficiency of 74.9 % for the CW signal, and 67 % for the QPSK signal with 10 MHz channel bandwidth on the load of 345 Ω at 2.58 GHz operating frequency.

RCS Reduction and Gain Enhancement for the Circularly Polarized Array by Polarization Conversion Metasurface Coating

High-gain, low-profile circularly polarized (CP) array with low radar cross section (RCS) is proposed based on the ultrawide band (UWB) polarization conversion metasurface (PCM) coating. A chessboard-like coating is formed by a mess of arrow-shaped PCM elements that have UWB and high polarization conversion ratio. The coating is distributed beneath the dipoles, behaving as a reflector. With the PCM beneath each dipole, the CP radiation is achieved and enhanced in a low profile by the radiating wave and the reflected wave, which have equal amplitude and 90° phase difference. With the chessboard-like coating, the incident wave is converted into the equal amplitude and out-of-phase reflected waves, which will cancel each other to reduce the backward scattering. The performances of the array are validated by both simulations and measurements. The results show that the left-hand CP radiation is achieved in 11.25 to 12.31 GHz with the RCS being reduced for more than 4.8 dB in 10.5 to 35.1 GHz.

CPW-fed circularly-polarized antenna array with high front-to-back ratio and low-profile

Abstract A novel design of a coplanar waveguide (CPW) feed antenna array with circular polarization (CP) and a high front-to-back ratio is described. The proposed CP array is achieved by using a compact CPW–slotline transition network etched in the ground plane. The measured results show that this kind of feeding method can improve the impedance bandwidth, as well as the axial ratio bandwidth of the CP antenna array and provide adequate gain. The proposed array can achieve a 6.08% impedance bandwidth and a 4.10% CP bandwidth. Details of the antenna design and experimental results are presented and discussed.

User Effects on the Circular Polarization of 5G Mobile Terminal Antennas

User effects on a circularly polarized phased array for 5G mobile applications for frequencies around 28 GHz are studied in this communication. Two figures of merit are defined: the total scan pattern and coverage efficiency of the circular polarization (CP). The user effects on the performance of a CP phased array are studied via two defined parameters. The investigations are carried out in talk mode (with a hand and a head) and in data mode (with a homogeneous whole-body phantom). The scattering properties of the proposed phantom are verified via the measurement of an antenna with known radiation parameters and a human. The CP coverage efficiency is relatively less affected by biological tissues than by the conventional coverage efficiency, although the absolute value of the CP coverage efficiency depends on a specific design. When user effects are introduced, the axial ratio bandwidth becomes approximately 0.8 to 1.3 GHz narrower. To realize the optimal CP performance and reduce the user effects of the CP coverage efficiency, a CP array at the bottom short edge of the ground plane should be chosen in the talk mode, while the top short edge location should be chosen in the data mode.

60 GHz Wideband High-Gain Circularly Polarized Antenna Array With Substrate Integrated Cavity Excitation

This letter presents a new wideband high-gain circularly polarized (CP) substrate integrated cavity excited antenna array for the 60 GHz applications. First, a 2 × 2-element CP array is proposed with an aperture-coupled two-arm spiral antenna as its radiating element, which can exhibit good CP radiation performance. Instead of the conventional lossy and complicated feed network, a simple but efficient excitation structure based on higher-order-mode (TE340) cavity resonance is used to feed the array. The higher-order-mode cavity feeds all of the radiating elements in the same phase and magnitude, and the resonant mode is excited by a single slot aperture. Then, the proposed 2 × 2-element CP array is used as subarray to implement a sequential-rotationally fed 4 × 4-element CP array. Measured results show that the array has a wide axial-ratio bandwidth of more than 18.8% (53–64 GHz) with a peak gain reaching 20 dBic occurring at 61 GHz. The radiation patterns of the array are generally symmetrical with its main beam fixed at boresight.