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A dual-band dual-polarization horn antenna array is proposed for Ku-band satellite communication (SATCOM) in this article. A miniaturized orthomode transducer (OMT) using the mutually perpendicular multistep waveguide transition and coupled transition to transmit TE10 mode and TE01 mode, respectively, is integrated into the radiation element. The high isolation characteristic of horizontal polarization in the transmitting band (Tx) and vertical polarization in the receiving band (Rx) desired for SATCOM is realized. Moreover, the sinusoid-tapered horn antenna and the radiating cross-shaped cavity are employed as the shared-aperture element to radiate orthogonal waves simultaneously, having the potential of wide bandwidth, low sidelobes, and high radiation efficiency. With the facility of the 3-D metal printing technology, a horn antenna array consisting of the proposed 4 $\times4$ radiation elements and feeding networks is demonstrated and fabricated. The gains up to 26.48 and 26.51 dBi with radiation efficiencies of around 94% and 90% are obtained at Tx- and Rx-bands, respectively. Benefitted from the advantages of compact size, high gain, and high efficiency, the proposed horn antenna array is suitable to tackle the high-throughput demand in Ku-band SATCOM systems. [ABSTRACT FROM AUTHOR]

In this communication, a high-order-mode (HOM)-fed open-ended rectangular waveguide antenna with high gain and broadband is proposed for fifth-generation (5G) applications. A miniaturized HOM cavity with four slots introduces hybrid modes of $TE_{340}$ and $TE_{140}$ , which act as a low loss feeding network. Furthermore, an open-ended waveguide is loaded above the HOM cavity to widen the impedance bandwidth. Compared with $TE_{340}$ HOM, hybrid modes of $TE_{340}$ and $TE_{140}$ HOM provide more compact size and higher gain. For the proof of concept, a $4\times $ 4 antenna array is designed and fabricated. The measured impedance bandwidth is 28.1% from 32.85 to 43.6 GHz. The measured peak gain is 21.7 dBi. Great compatibility between simulated and measured results is achieved. [ABSTRACT FROM AUTHOR]

In this letter, a compact wideband circularly polarized patch antenna array is proposed to cover the 57–71 GHz band. The antenna array is constructed by 45 $^\circ$ inclined slits loaded circular radiating patches with rectangular back cavities, two-layer sequential rotation feed networks, and a waveguide transition. Novel self-sequential rotation technology is introduced using a dual-high-order-mode cavity to improve the axial ratio (AR) and impedance bandwidths of the subarray. Compared with conventional sequential rotation feed networks, the proposed feeding scheme provides higher aperture efficiency. A 4 × 4 patch antenna array is fabricated using standard printed circuit board technology. Measured results show that the $-$ 10 dB impedance and 3 dB AR overlapped bandwidth is 23.8%(57–72.3 GHz). The measured peak gain is 20.5 dBic with an aperture efficiency of 87.7% at 66 GHz. [ABSTRACT FROM AUTHOR]

In this article, a novel structure of the high-order-mode cavity fed sequentially rotated patch antenna array is proposed for diverse polarizations. The diverse polarizations, including right-hand circular polarization (RHCP), left-hand circular polarization (LHCP), −45° linear polarization (LP), 0° LP, 45° LP, and 90° LP, are achieved based on the current distribution on the patches and different electric field modes in the high-order-mode cavity by adjusting the phase and amplitude of the two orthogonal feeding ports. Furthermore, from the electric field distribution in the high-order-mode cavity with different feeding schemes, arbitrary polarizations were analyzed and obtained. An $8\,\times \, 8$ dual-circularly polarized (dual-CP) antenna is demonstrated. Good agreement between the simulated and measured results is obtained, validating the design. The experimental results show that the impedance bandwidths (<−10 dB) for the two ports are 14.2% and 13.3%. The 3 dB axial ratio (AR) overlapping bandwidth is 10.5%. The maximum gain is 25 dBic. Attributed to its compact size, high gain, and high efficiency, the presented array is a good candidate for millimeter-wave applications. [ABSTRACT FROM AUTHOR]

In this letter, an 8 × 8 dual-polarized antenna array with high gain and broad bandwidth is proposed for $Q$ -band millimeter-wave (mm-wave) application. Metallic pillars and cavities act as magnetoelectric dipoles fed by a 1 to 4 backed cavity with cross-shaped slots. The cross-shaped slots are adopted to excite two orthogonal linear polarizations. A feeding network with shared vias is designed to construct the antenna array. An 8 × 8 dual-polarized antenna is fabricated and measured. The measured impedance bandwidths are 13.4% from 34.7 to 39.7 GHz and 14.4% from 34.6 to 40.1 GHz for the two ports, respectively. The 3 dB gain fluctuation bandwidth is 8% for the two ports. The maximum gain is up to 24.8 dBi due to less substrate loss in the radiation structure. Attributed to its high gain and high efficiency, the proposed antenna is a promising candidate for mm-wave applications. [ABSTRACT FROM AUTHOR]

The authors propose a 4 × 4 circularly polarized (CP) antenna array with wide impedance bandwidth and axial‐ratio (AR) bandwidth and design the same for 60‐GHz applications. The overall structure of the proposed antenna array consists of a cavity‐back circular patch array and two layer feed‐networks. The upper feed‐network is with four TE340 high‐order mode substrate integrated cavities (SIC). Fed with SIC, circular patches with a pair of 42°‐inclined slits can achieve circular polarization. In order to improve the AR bandwidth and gain performance, the substrate integrated waveguide (SIW) sequential rotation feeding technique is utilized in the lower feed‐network. For proof of concept, the 4 × 4 array is fabricated and measured. Measured results show that −10‐dB impedance bandwidth of the proposed antenna array is 27.2% from 52 to 68.4 GHz and 3‐dB AR bandwidth is 18.9% from 55.7 to 67.3 GHz. Furthermore, the 3‐dB gain bandwidth is 26.2% from 53 to 69 GHz with a peak gain reaching 19.3 dBic at 62 GHz. [ABSTRACT FROM AUTHOR]

The authors propose a 4 × 4 circularly polarized (CP) antenna array with wide impedance bandwidth and axial‐ratio (AR) bandwidth and design the same for 60‐GHz applications. The overall structure of the proposed antenna array consists of a cavity‐back circular patch array and two layer feed‐networks. The upper feed‐network is with four TE340 high‐order mode substrate integrated cavities (SIC). Fed with SIC, circular patches with a pair of 42°‐inclined slits can achieve circular polarization. In order to improve the AR bandwidth and gain performance, the substrate integrated waveguide (SIW) sequential rotation feeding technique is utilized in the lower feed‐network. For proof of concept, the 4 × 4 array is fabricated and measured. Measured results show that −10‐dB impedance bandwidth of the proposed antenna array is 27.2% from 52 to 68.4 GHz and 3‐dB AR bandwidth is 18.9% from 55.7 to 67.3 GHz. Furthermore, the 3‐dB gain bandwidth is 26.2% from 53 to 69 GHz with a peak gain reaching 19.3 dBic at 62 GHz. [ABSTRACT FROM AUTHOR]

In this article, a broadband beam scanning antenna array is proposed in Q‐band attributed to miniaturized size, wideband and high integration. A patch antenna element is utilized with a back cavity, which is formed by metallic via holes and ground plane. A 1 × 4 series fed sub‐array is implemented by the patch element using multilayer PCB. Four symmetrical sub‐arrays and Butler matrix feeding network are used to form the antenna array with high gain and decrease side lobes. The Butler matrix is implemented by substrate integrated coaxial line, which provides low loss of around 0.09 dB/mm from 40 to 50 GHz. The measured antenna array bandwidth is 9.8 GHz (21.8%) under the condition of voltage standing wave ratio less than 2. The main beam of the antenna array in azimuth direction is tilted to −28.5°, −14.1°, 18.4° and 35.6° and the gains are 13.11, 13.88, 14.02 and 11.78 dBi at 45 GHz, respectively. Both the measured and simulated results agree well. [ABSTRACT FROM AUTHOR]

In this letter, a wideband circularly polarized reflectarray composed of 30 × 30 unit cells is proposed to generate dual-mode vortex beams. The element consists of two back-to-back semi-split-loop structures printed on the FR-4 substrate, an air layer, and a metal ground plane. The two back-to-back semi-split-loop structures provide the multiresonance property, which can effectively increase the bandwidth. A 360° phase range is achieved by changing the spatial orientations of the element. Based on the proposed element and the superposition design method of aperture field, a dual-mode square aperture vortex beams reflectarray is simulated, fabricated, and experimentally demonstrated. The measured results confirm that two vortex beams carrying +1 and –1 mode of orbital angular momentum are successfully generated in a wide range of frequencies from 5 to 8 GHz. The size of the proposed reflectarray is 75 cm × 75 cm, and the measured maximum gain is 22.2 dBic. The measured 1 dB gain bandwidth is 33.3%. [ABSTRACT FROM AUTHOR]

In this paper, a novel configurable loop array antenna based on resonator-loaded microstrip lines (RLML) is proposed to enlarge the interrogation zone of the reader antenna for near-field ultrahigh-frequency (UHF) radio frequency identification (RFID) system. The proposed loop array antenna is composed of a number of RLML loop units. By configuration of the RLML loop units sharing a common side with its adjacent RLML loop units which carry reverse-direction flowing current in the ${x}$ -axis and ${y}$ -axis directions, loop array antennas are created to generate a strong and uniform magnetic-field distribution over a large configurable interrogation area. As an example, loop array antennas with $1\,\times \,8$ and $2\,\times \,3$ RLML loop units implemented onto a piece of an FR4 printed circuit board (PCB) are designed, fabricated, and measured. The measured bandwidth ranges from 894 to 964 MHz for a $1\times 8$ array antenna with a reading area of $570 \,\,{\mathrm{ mm}}\times 150\,\,{\mathrm{ mm}}$ and 917–932 MHz for a $2\times 3$ array antenna with a reading area of $270 \,\,{\mathrm{ mm}}\times 240\,\,{\mathrm{ mm}}$. The reading distances of an $1\times 8$ array antenna for loop-like tag, dipole-like tag, and antimetal tag are achieved up to 22, 42, and 45 mm, respectively. For a $2\times 3$ array antenna, the reading distances of three tags are achieved up to 23, 43, and 40 mm. [ABSTRACT FROM AUTHOR]

A dielectric-slab-loaded hollow substrate-integrated waveguide (HSIW) $H$ -plane horn antenna with improved impedance matching is proposed based on printed circuit board material FR-4. HSIW is utilized to avoid high dielectric loss. Apart from that, a dielectric slab is added by directly extending the substrates for gain improvement. Moreover, two coupling lines are added above and below the horn aperture for better impedance matching. The proposed HSIW $H$ -plane horn antenna shows a maximum realized gain of 11.2 dBi with 77.6% radiation efficiency and 32.9% bandwidth (27.7–38.6 GHz). Based on the antenna element, a $1\times 4$ HSIW $H$ -plane horn antenna array is proposed. The array shows a maximum realized gain of 17.2 dBi with 66.5% radiation efficiency and 31.9% bandwidth (27.6–38.1 GHz). Good agreements of the measured and simulated results are achieved for both designs. The proposed antenna and array can be good candidates for low-cost millimeter-wave wireless communication systems. [ABSTRACT FROM AUTHOR]

A wideband vortex beam reflectarray is designed and fabricated to generate the orbital angular momentum (OAM) waves for an $\boldsymbol{l} = 2$ mode. A quarter-wavelength element is proposed to achieve a reflection phase of 360° at the designed frequency of 6 GHz. The element consists of a loop patch, a cross-dipole patch, and four square patches. The symmetric structure of the element makes it suitable for dual polarization. It is revealed that the OAM mode purity and operational bandwidth of the reflectarray are increased by using the quarter-wavelength element. The array size is $\text{50} \times {\text{50 cm}}^2$ , which achieves measured gain of 18.98 dBi at 6 GHz and operational OAM bandwidth of 42%. [ABSTRACT FROM AUTHOR]

In this paper, a novel compact magneto-electric (ME) dipole antenna with broad E-plane beamwidth is proposed for ultra-wideband (UWB) indoor positioning system. The ME dipole antenna is designed to obtain wideband and symmetrical radiation pattern. The angled dipole and loaded vertical metal plate are introduced to broaden the E-plane beamwidth. A 1 × 2 antenna array is designed for high gain in the H-plane. A measured −10 dB impedance bandwidth is 52% and the gains are round 5.9 ~ 7.5 dBi from 4.8 to 8.2 GHz. The measured 3-dB beamwidth in the E-plane of the ME dipole antenna array is 83° at 6.5 GHz and more than 100° at 7 GHz. The measurement results are in good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

This paper presents a radio-frequency identification (RFID) switch beam scanning antenna array for application in metal environment. Three 1 × 2 planar inverted-F antenna arrays are designed with a driven element and two parasitic elements. Three elements are controlled by a switch feeding network consisting switch and control module. The size is 300 × 600 × 11.6 mm3. The measured −10 dB impedance bandwidth is 50 MHz (895-945 MHz). The proposed antenna array is capable of steering the radiation pattern to −20°, 0°, and +25° in xoz-plane. The scanning beam direction gain reached 9.4 dBi. The measured and simulated results agree well. The reading rate achieves 100% in a metal environment. [ABSTRACT FROM AUTHOR]

This study presents a two‐dimensional (2D) scanning antenna array of ultra high frequency radio frequency identification system with high stability and reliability in metal cavity. The antenna array is composed of nine elements and a feeding network. The two‐shorting‐plate planar inverted‐F antenna is designed as antenna element with small dimension 10 × 10 × 1.5 cm3. The bandwidth of element is about 72 MHz (840–912 MHz) under the condition of voltage standing wave ratio (VSWR) <2. The feeding network consists of a butler matrix and three three‐way power dividers. Both the nine antenna elements and a feeding network are specified within 33 × 30 × 20 cm3 areas, where switches are used to change the connection of feeding network to obtain 2D scanning beam. The measured bandwidth is about 30 MHz (845–875 MHz) under the condition of VSWR <2, which covers Europe standard (865–868 MHz) completely. The scanning beam directions are ±60° with 10 dBi gain at the xz‐plane and ±50° with 10 dBi gain at the yz‐plane. The read rate of the proposed antenna array achieves 100% in the metal cavity with 18 dBm input power. [ABSTRACT FROM AUTHOR]

The multimode orbital angular momentum (OAM) radio waves can be used to multiplex multiple transmission channels to increase the capacity of communication system without adding additional bandwidth. However, the divergence of the OAM beams and beam inconsistency escalate by increasing OAM mode number. Moreover, the worse sidelobe level (SLL) always appears along with a better convergent beam. In this article, the fruit fly optimization algorithm (FOA) is proposed to suppress the SLL in multimode OAM scenario. Based on the concentric circular array antenna (CCAA), the feeding amplitudes and the radii of the array are synthesized simultaneously to realize less than −30 dB SLL of the multimode OAM patterns. When the main lobes with different OAM modes steered to a uniform azimuth of θ = 0°, the SLLs of these OAM modes are also suppressed to less than −21 dB. The advantages of FOA used in the OAM pattern synthesis are verified by comparing it with the genetic algorithm (GA). The FOA‐based synthesis has a simpler implementation flow diagram which reduces the time of synthesis to 39.5% of GA. [ABSTRACT FROM AUTHOR]

A broadband four-feed circular patch antenna is demonstrated to generate high-purity dual-mode vortex beams carrying orbital angular momentum (OAM) for the first time. The electric field formula of the circularly polarized (CP) component is derived for analyzing radiation characteristics of different OAM modes, such as the CP property, phase and amplitude distributions. Theoretical calculation and numerical simulation results show that the four-feed patch antenna operating in the TMn1 mode can generate ±n OAM waves. A prototype of a four-feed circular TM21-mode patch antenna is fabricated and measured to verify the effectiveness of the theoretical analysis. The proposed antenna consists of a four-feed patch with an air-coupled parasitic patch and a four-way phase-shifting feeding network. Experimental results show that the proposed antenna can generate a left-hand CP OAM with mode l = +2 and a right-hand CP OAM with mode l = −2. The OAM beams are generated in a wide band from 5.50 to 6.50 GHz with a mode purity over 90%. The proposed method is very suitable for the generation of wideband, dual-mode and high-purity OAM beams in the microwave and millimeter wave bands. [ABSTRACT FROM AUTHOR]