Cross-polarization Level Research Articles

Design of a Dual-Mode Waveguide CP Antenna with a Symmetric Beamwidth Using Short Stub for Low-Orbit Satellite TC&R

In this study, a dual-mode waveguide circularly polarized antenna for TC&R (telemetry, command, and ranging) was proposed for the communication between a low-orbit satellite and a ground station. The proposed antenna required both a wide -10 dB bandwidth and axial ratio bandwidth of 7.1–7.3 GHz and 8.0–8.4 GHz. The antenna was designed with a stepped septum inside a square waveguide to obtain circular polarization and the axial ratio wide bandwidth. Next, a dual-mode synthesis method was adopted for link budgeting by combining square and circular waveguides. The requirement was that the co-polarization level with a symmetric -3 dB beamwidth of 39° must be -5 dBic or higher at ±76.5°, and the cross-polarization level must average -15 dBic or lower at ±76.5°. Finally, the corrugate structure attached to the outside of the extended circular waveguide was offset in multiple steps to suppress the back lobe of the crosspolarization As a result, the axial ratio maintained an average of 1.8 dB at 0° within each band of the required frequency. In addition, the co-polarization obtained an average of -4.52 dBic in the 7.2 GHz band and -5.31 dBic in the 8.2 GHz band at ±76.5°. Finally, in the case of the cross-polarization pattern, the back lobe level was suppressed by 9.89 dB at 7.2 GHz by the corrugate structure, and an average value of -19.9 dBic or less was obtained at ±76.5°. The proposed antenna was confirmed to be effective as a Korean low-orbit satellite TC&R antenna with a radiation pattern of a symmetric beamwidth.

An I-Shaped Slot Grid Antenna Array with Substrate Integration and Enhanced Bandwidth

Aimed to transmit electromagnetic energy in wireless power transfer, a planar substrate-integrated grid antenna array with four I-shaped slots was designed. A transverse stub was added to the microstrip line to produce additional resonance; hence, the impedance bandwidth was enhanced from 1.9% to 6%. Four I-shaped slots were formed on a perfect electric conductor (PEC) sheet to realize boresight radiation. Four gaps were etched to refine and compress the in-band impedance property. Furthermore, characteristic mode theory was adopted to analyze the working mechanism. Finally, the measurement results showed that the antenna had an operating bandwidth of 5% (|<i>S</i><sub>11</sub>| < -10 dB from 5.67 GHz to 5.96 GHz). In the operating band, the boresight gain varied from 9.3 dBi to 11.3 dBi. The cross-polarization level was lower than -30 dB on the boresight. Therefore, the proposed array is suitable for use in wireless power transfer systems and other related applications.

Two-Bit Planar Coding Reconfigurable Array Antenna for Dual-Polarized Wide-Angle Beam Scanning

In this communication, a dual-polarized coding reconfigurable array antenna with the characteristics of being low-profile, low-cost, relatively low-sidelobe and wide-angle beam scanning is proposed. By exciting the array via different feeding ports, horizontal and vertical polarized scanning beams can be generated. By adjusting the PIN diodes integrated on the feeding lines, the element presents four different phase states of -270°, -180°, -90°, and 0°, labeled as “00”, “01”, “10”, and “11”. An eight elements array antenna is designed based on the element. With the introduction of elaborately designed two groups of fixed phase delay, the sidelobe level at different scanning angles can be effectively reduced in two polarized directions and the gain are also improved. The simulated and measured results of the fabricated prototype indicate that dual-polarized ±60° wide-angle beam scanning, moderate array gain, relatively low sidelobe level, and low cross polarization level can be achieved. The proposed array antenna, which according to our best knowledge, is the first dual linear polarized wide angle beam scanning coding reconfigurable array without the feeding horn, might have good applications in base station and fully polarimetric radar.

A Differential Slot-type Dual-polarization Ultra-wideband Antenna

A differentially fed dual-polarization slotted antenna with an ultra-wide bandwidth and low cross polarization is presented in this paper. The antenna is composed of a radiation patch and a ground plane, both of which are printed on the top of the dielectric substrate. The ground is extended toward the radiation patch to form a slotted coplanar structure. In order to expand the bandwidth, a cross-shape symmetrical slotted structure is loaded into the radiation patch. Differential feed is adopted to realize 0∘/90∘ linear polarizations and suppress the cross polarization. Simulation and measurement results show that the proposed antenna with dimensions of 0.53λ0× 0.53λ0 × 0.0135λ0 (λ0is the wavelength at 4 GHz) has a differential mode impedance bandwidth of 82.25% (2.27-5.56 GHz), a differential feed port isolation of higher than 28 dB, and a cross polarization level of less than −30 dB, which achieves the characteristics of ultra-wideband, high isolation, and low cross polarization level.

Compact Millimeter-Wave Array With Wide-Angle Scanning for Mobile Phones

This paper describes a compact four-element wide-angle scanning millimeter-wave array for mobile phones. The wide-angle scanning array with four elements is achieved with a small element spacing of 0.3λ0. Two critical difficulties for the compact array with 0.3λ0 spacing are the realization of the small element and the mutual coupling reduction between each element. For the small antenna element, a modified quarter-wavelength shorted patch antenna element working at the 25.5-27.5 GHz is designed. The coupled shorted structure and coupled feeding structure of the element is designed to reduce the H-plane cross-polarization level (XPL) which is a key drawback of quarter-wavelength shorted patch antenna. For the mutual coupling of the four-element array with 0.3λ0 spacing, three compact neutralization lines (NLs) are applied to reduce the mutual coupling to better than -15 dB. Finally, the proposed compact four-element array only occupies a small size of 1.14λ0 × 0.3λ0, which is the smallest mm-wave four-element array in the open literature. Also, the proposed array can scan from -60° to 60° with a peak gain of 9 dBi, a gain fluctuation less than 1.3 dB, a good sidelobe level, and an acceptable cross-polarization level. The proposed mm-wave array with the superior performance of a small array size and wide beam scanning is promising for modern mobile phones.

Mechanically Controlled, Wide-Angle Scanning, Series-Fed Antenna Array With Low Profile for High-Power Radar Systems

This paper presents the design and implementation of a mechanically-controlled, series-fed antenna array featuring wide-angle beamsteering at the X-band. A theoretical model of a series-fed array, including phase shifters inserted between consecutive elements, is initially developed to derive design rules and gain insight into crucial performance trade-offs. Subsequently, a mechanically-controlled, reflection-type phase shifter consisting of a branch line coupler and two Pi-network reflective loads is presented. A movable metallic overlay tunes the impedance of the reflective loads, thus effectively modifying the output phase. While requiring a minimal linear displacement of only 0.06λ0, this topology provides a maximum phase shift of 300° with an average insertion loss of 1 dB and is exploited for synthesizing a series-fed patch array. Based on simulations and measurements, the proposed antenna offers an almost constant realized gain of about 15 dBi within a wide scanning range of ±50°, and the side lobe level is better than -12 dB. The average total efficiency is 50%, and the cross-polarization levels are at least 11 dB below the maximum realized gain. The main weaknesses are the narrow bandwidth of 2.5% and the slight beam squint as the frequency varies. The proposed design is ideal for radars due to its excellent performance and high power-handling capability.

Compact Additively Manufactured Conformal Slotted Waveguide Antenna Array

In this work we present the design and fabrication in metallic 3D-printing of a compact conformal slotted waveguide antenna array operating in the Ku-band. The application objective, although not limited only to this, is the optimisation of an antenna element which by stacking will be able to form a quasi-cylindrical sector. A beamforming network will be used for beam-steering in the elevation plane as coverage in the azimuthal plane is guaranteed by the conformal geometry. The compact design of the antenna element is therefore of great significance. For this reason, a direct feeding scheme by a coaxial connector is adopted. The antenna has been optimized following multiple parametric analyses of its geometrical parameters for the enhancement of the bandwidth, return losses and realized gain. The antenna was fabricated with Selective Laser Melting in aluminium and the experimental results agree well with the numerically calculated ones. The proposed CSWAA exhibits a reflection coefficient below -10 dB, realized gain above 14 dBi, as well as good cross-polarization and side-lobe level over a relative bandwidth of 8%.

A Millimeter-Wave Antipodal Linearly Tapered Slot Antenna Array for 5G Wireless Communication

This paper presents an antipodal linearly tapered slot antenna (ALTSA) array with the newly emerging substrate-integrated coaxial line (SICL) technology. Each element of the proposed array consists of two vertically stacked antipodal tapered slot antennas (TSA) with the inner conductor of a SICL as the shared fin. The vertical symmetry of this radiating element structure significantly suppresses the cross-polarization level. By employing a SICL-based power splitter with differential outputs, a two-element array with horizontal symmetry is formed. With the inner conductors of two parallel SICLs combined as the flaring metal shared by adjacent tapered slots, the main beam squint is effectively suppressed. Experimental results show an actual −10-dB impedance bandwidth (BW) of 24.5∼34.4 GHz, and the realized gain range measured is 16.1∼18.7 dBi. The cross-polarization levels are −39.4 dB/−40.7 dB at 30 GHz for the E-/H-planes. The measured results agree well with the simulated data which demonstrates the feasibility of the proposed SICL-based ALTSA scheme in the potential 5 G·millimeter-wave (mmWave) applications.

Circularly Polarized High-Gain Fabry-Perot Cavity Antenna with High Sidelobe Suppression

The proposed design approach improves the circularly polarized Fabry-Perot cavity antenna (CP-FPCA) by increasing gain and sidelobe suppression (SLS) while reducing the axial ratio (AR) and cross-polarization levels. Conventional CP-FPC antennas have a high AR due to the lack of independent control over circular polarization conditions. The solution proposes a double-layered circularly polarized partially reflecting surface (CP-PRS) that independently controls the circular polarization conditions at the design frequency f0 (10 GHz) for equal magnitudes and at a ±90° phase difference between orthogonal components of the transmitted waves. The PRS and artificial magnetic conductor (AMC) unit cells are employed to satisfy Trentini’s beamforming condition, leading to increased gain and SLS and lowered AR and cross-polarization levels. Consequently, the proposed CP-FPCA provides a 15.4 dBi high gain with 25.3% aperture efficiency and more than 23.5 dB high SLS in each plane. Moreover, it achieves an AR lowered by 0.12 dB and a cross-polarization level below −42 dB. A strong correlation between the simulations and experiments proves the practicality of our proposal.

A circularly polarized phased array antenna with 60° scanning in the D-plane using a top-loaded patch

The requirements for circularly polarized (CP) phased array antennas are growing with the rapid development of electronic systems. To achieve a low-profile, wideband, and large scanning-angle CP, we constructed a novel CP unit cell with a two-layer folded coupling patch and a top-loaded patch. The design of the folded coupling patch was based on the principle of reverse current cancellation. Compared with the single-layer coupling patch, the folded coupling patch suppressed the occurrence of strong in-band resonance and obtained a wider axial ratio (AR) bandwidth. To solve the problem of AR performance deterioration in the D-plane scanning, we introduced the top-loaded patch to replace the thick wide-angle impedance matching layer, which improved the difference in co-polarization components and reduced cross-polarization level. Thus, a large scanning angle of more than 60° in the D-plane was obtained. An 8 × 8 planar array based on the proposed CP unit cell was designed. The array achieved a 3.9:1 (3.2–12.5 GHz) AR bandwidth and up to 60° scanning angle in the D-plane and 70° in the E-/H-plane; an AR smaller than 3 dB was demonstrated over the entire scanning range.

A Frequency Tunable Dielectric Resonator Antenna with Reduction of Cross Polarisation for Wi MAX and Sub 6 GHz 5G Applications

A frequency Tunable (mechanical tuning) Linearly Polarized (TLP) rectangular Dielectric Resonator Antenna(DRA) coupled with a horizontal/vertical-slot and excited with circular-ring type feed is investigated in this article.The frequency tunability (mechanical tuning) is achieved by the rotation of slot at different angles of the proposedstructure. Hence, two linearly polarized antennas have been proposed for different frequency bands such as Wi-MAX and Sub-6 GHz/5G, respectively, using slot variations (named as DRA-1 and DRA-2). TE 11δ mode has been excited in both the DRAs and confirmed by orientation of electric field inside the rectangular DRA. The measured -10 dB input impedance bandwidths of DRA-1 offer 21.60 % being centered at 2.87 GHz and the separation of co-polarized and cross-polarized field levels is above -24 dB in the broadside direction (xz-plane). Whereas DRA-2 offers measured -10 dB input impedance bandwidths of 23.03% being centered at 3.56 GHz having a separation of co-polarized and cross-polarized field levels are above -23 dB in the broadside direction (xz-plane). In addition, the proposed DRA-1 and DRA-2 show a maximum gain of 5.23 dBi and 4.75 dBi in broadside direction, respectively.

Low-Profile Millimeter-Wave Metasurface-Based Antenna with Enhanced Bandwidth.

A millimeter-wave broadband metasurface-based antenna with a low profile is proposed. In order to guide the mode excitation, the characteristic mode analysis (CMA) is used for the design and optimization of the proposed antenna. Four sets of coplanar patches with different dimensions on a thin printed circuit board are used to generate four adjacent broadside modes, which are directly fed by a coaxial probe. Then, to expand low-frequency bandwidth, a new resonant mode is introduced by etching slots on the parasite patch. Meanwhile, the extra mode introduced does not significantly change the radiation performance of the original modes. Moreover, dual slots are etched on the mid patch fed by the coaxial probe, which moves the orthogonal modes of the chosen modes out of the operating band to reduce cross-polarization levels. The proposed antenna realized 25.02 % (30-38.58 GHz) impedance bandwidth with dimensions of 1.423×1.423×0.029λ0 3 (λ0 is the wavelength at 34 GHz in free space), and the realized gain in the band is 8.35-11.3 dB.

A wideband omnidirectional dipole antenna with parasitic loop based on multi-resonant modes

ABSTRACT A wideband omnidirectional dipole antenna with parasitic loop based on multi-resonant modes is proposed for WLAN, 5 G Sub-6 GHz, and RFID applications. The antenna is composed of a regular dipole with co-planar strips and a parasitic loop with four U-shaped branches. A regular dipole with co-planar strips is used to generate two resonant modes, and the parasitic loop around it generates another two resonant modes. By combining these four resonant modes, a wideband characteristic is achieved. In order to reduce the cross-polarization, four U-shaped branches are introduced, and then the cross-polarization levels are decreased from −2 dB to −13 dB. A prototype with a compact size of 0.6λ0 ×0.56λ0 ×0.012λ0 (λ0 is the wavelength in free space at center frequency) is fabricated and tested. Measurement shows that effective bandwidth is 1.8–5.6 GHz (102.7%), the measured gain variation is only 1.3 dBi, and omnidirectional radiation patterns are achieved over the operating band.

Near zero index Metamaterial-based SIW antenna for 6G Sub-Terahertz applications

This paper introduces a novel high-gain circularly polarized (CP) antenna that utilizes a NRZI (Near Zero Refractive Index) and MNG (Mu Negative) metamaterialslab. The antenna employs a substrate integrated waveguide (SIW) technique and loaded with compact square split ring resonator (SSRR) combined with a hexagonal-shaped structure by a 0.2 mm width slab as a unit cell to achieve high gain and circular polarization. The metamaterial characteristics were examined through material wave propagation in two main directions at the y and x-axis. For wave propagation at the y-axis, the MTM structure demonstrates mu-near-zero (MNZ) with more than 88 GHz bandwidth, NZRI, and Epsilon-Near-Zero (ENZ) properties. However, for x-axis wave propagation, it indicates a wide negative range of single mu metamaterial from 176 to 220 GHz, NZRI, and ENZ properties. By using six unit cells, the antenna acts as an aperture-efficient focusing metasurface lens and polarization converter for a primary source antenna. The NRZI-MNG enhances the gain of the suggested antenna by 6–7 dB, and converts the linearly polarized wave emitted by the patch antenna into circularly polarized waves. The designed antenna has an impedance bandwidth from 176.5 to 285 GHz, with a 3 dB axial ratio achieved from 177 to 204 GHz. The peak gain of the antenna is 11.3 dBi at 223 GHz, and a gain of around 10 dBi is achieved over the entire CP bandwidth with a good cross-polarization level. In addition, the transmittance of the suggested metamaterial antenna is between 80% and 90% in the operating band. These excellent performances make this antenna very promising for sub-THz 6G applications.

Dual-band filtering antenna with independent predetermined frequencies and low cross-polarization levels

In this paper, a dual-band filtering antenna with independent predetermined frequencies and low cross-polarization levels is proposed. In order to realize the independent control of frequencies of two radiation passbands, multiple additional structures such as rectangular slots, rectangular parasitic patches, and U-shaped slots are integrated on the traditional rectangular patch antenna to introduce new resonant modes and radiation nulls to the antenna, simultaneously. Since the generation structures of each frequency point are different, they do not affect each other. Besides, to obtain low cross-polarization levels, each additional structure is carefully adjusted such that the current vectors of each resonant frequency along the cross-polarized direction are quite weak. The proposed antenna operates in the 5G sub-6G (4050–4294 MHz) and the Wi-Fi 5.8 GHz band (5700–5920 MHz), and achieves cross-polarization levels of −37.8 and −36.8 dB in the lower and higher frequency bands, respectively. Compared to other multi-band filtering antennas, the proposed one has the advantages of independent predetermined frequencies and lower cross-polarization levels.

A dual‐layer polarisation rotating element for transmitarray designs

AbstractA transmitarray adopting dual‐layer polarisation rotating (PR) elements is proposed. The element comprises a pair of perpendicularly placed C‐shaped slots etched on the two sides of a single‐layer substrate and orthogonally rotates transmission wave polarisation with regard to the incidence. By adjusting C‐shaped slot's dimension as well as mirroring the bottom layer of the element, a 360° phase shift with a high transmission magnitude is achieved. Based on the proposed unit‐cell, a dual‐layer transmitarray composed of 529 elements is designed and developed. The experimental 1‐dB gain bandwidth and peak aperture efficiency are 13% and 44% respectively. Furthermore, sidelobe level of 20 dB and cross polarisation level of 26 dB are obtained at 10 GHz. These promising properties demonstrate the superiority of the element for transmitarray designs. In addition, this element can be also a good candidate for folded transmitarray designs.

A wideband magnetoelectric dipole antenna for 4G/5G communication

AbstractIn this letter, a wideband magnetoelectric (ME) dipole antenna for 4G/5G communication is proposed. The bandwidth of the antenna is greatly enhanced by loading two pairs of metallic circular loops on the planar electric dipole. With the loops, the antenna impedance bandwidth in terms of 10 dB is improved from 48.3% (1.98–3.24 GHz) to 86.8% (1.465–3.71 GHz), that is, 79.7% bandwidth enhancement is achieved. The surface current of the proposed antenna is analyzed in detail. It shows that when the length of the loops approaches half a wavelength, the loops contribute new resonant modes, thereby increasing the impedance bandwidth. A prototype is fabricated and measured. The measured results are in good agreement with the simulated counterparts. Meanwhile, the antenna gain ranges from 7.42 to 12.8 dBi across the operational frequency region. Stable radiation patterns with low crosspolarization levels are obtained in both E‐ and H‐plane.

Gain and Frequency-Selectivity Enhancement of Dual- Polarized Filtering IBFD Antenna Using PRS

A dual-polarized filtering Fabry–Perot antenna (FPA) with high selectivity and high isolation is proposed for in-band full-duplex (IBFD) applications. The proposed antenna utilizes a square patch as the feeding element, which is fed by a double differential-fed scheme for dual-polarized radiation with high isolation. The patch is loaded with a symmetrical cross-slot and four shorting pins for a broad passband filtering feature. To enhance broadside gain across a wide frequency range, the patch is incorporated with a partially reflecting surface (PRS), which is composed of two complementary cross-slot and patch arrays. Moreover, the frequency selectivity of PRS is exploited to improve the filtering characteristic. The double differential feeds are realized based on out-of-phase power dividers, which are combined with simple low-pass filters to further improve the out-of-band suppression. The final design was fabricated and measured. The measurement results show excellent results with a 10-dB return loss bandwidth of 21.5% (4.91–6.09 GHz), isolation of greater than 40 dB, peak gain of 13.7 dBi, out-of-band suppression level of better than 27 dB, and a cross-polarization level of less than –27 dB.

Millimeter-wave planar antenna array augmented with a low-cost 3D printed dielectric polarizer for sensing and internet of things (IoT) applications

A unique high gain antenna array with a 3D-printed dielectric polarizer is proposed. The packaging of the antenna array feeding structure is eliminated by aggregating the feeding network in between the antenna elements. This has a significant advantage in maintaining neat and symmetric radiation characteristics with low cross-polarization levels. The proposed structure combines two elements in one feeding point to reduce the array distribution feeding points of a 4 × 4 antenna array from 16 to 8 points. The proposed antenna array structure is extremely low in cost and can be used as either a linearly or circularly polarized one. The antenna array achieves a gain of 20 dBi/dBiC in both scenarios. The matching bandwidth is 4.1%, and the 3-dB Axial Ratio (AR) bandwidth is 6%. The antenna array uses a single substrate layer without the need for any vias. The proposed antenna array suits well various applications at 24 GHz, while maintaining high performance metrics, and low cost. The antenna array can be easily integrated with transceivers due to the use of printed microstrip line technology.

Isolation Improvement Using the Field-Circuit Combined Method for In-Band Full-Duplex MIMO Antenna Arrays

This paper proposes a field-circuit combined decoupling method for co-polarized in-band full-duplex multiple-input multiple-output (MIMO) antenna arrays. The proposed field-circuit combined method is composed of decoupling network and neutralization-based decoupling. An in-band full-duplex antenna with high isolation and low cross-polarization level is designed and extended to a 1 × 4 linear array. The decoupling network and ADS are applied for the array to alleviate the mutual coupling by rebuilding the neutralization wave paths in the circuit and field domains. Thus, low coupling (< −25 dB) among the transmitting/receiving antennas and high isolation (> 47 dB) between the transmitting and receiving antennas are achieved at 2.6 GHz, exhibiting a superior decoupling performance.