Horn Antenna Array Research Articles

Horn array antenna with high aperture efficiency and suppressed grating lobes

AbstractIn the design of horn array antennas, usually there is a challenge with the grating lobe problem and consequently quite low aperture efficiency. A new configuration for horn array antennas is presented which introduces high aperture efficiency with suppressed grating lobes in both E‐& H‐plane radiation patterns. The proposed array unit cell is a dual‐mode horn loaded by two corrugations in E‐plane. A sample 4 ⨯ 4 array of the proposed unit cell is designed to operate at Ku band. The simulation and measurement results show 13.3% operating bandwidth over which the grating lobes are totally suppressed and the aperture efficiency is above 70%. The antenna measured gain is also 27 dBi with 2 dB variation over the bandwidth. The results show that the aperture efficiency of 98% is achievable making use of the proposed topology.

Development of axion haloscopes for high-mass search at CAPP

The axion offers a well-motivated solution to two fundamental questions in modern physics: the strong CP problem and the dark matter mystery. Cavity haloscopes, exploiting resonant enhancement of photon signals, provide the most sensitive searches for axion dark matter in the microwave region. However, current experimental sensitivities are limited to the O(100)μeV range, while recent theoretical predictions for the axion mass favor up to O(102)μeV, suggesting the need of new experimental approaches that are suitable for higher mass regions. CAPP has developed/proposed several haloscopes effective for high-mass axion searches based on new cavity concepts and practical tuning mechanisms. They are characterized by large detection volumes and/or high quality factors at high frequencies, achieved by partitioning a single cavity into multiple cells, exploiting higher-order resonant modes, and constructing dielectric photonic crystal structures. Improving on the dish antenna haloscope scheme, a horn antenna array has also been proposed for volume-efficient broadband search in the THz region. We review these haloscope designs for sensitive search in the high-mass regions and discuss their impacts on future experiments.

Review of Terahertz Antenna Technology for Science Missions in Space

The utilization of terahertz (THz) band in the electromagnetic spectrum has great potential value both in scientific research and practical applications, therefore reasonable design of antenna system for radiating and receiving THz wave is especially critical. This article reviews the THz antenna technology toward atmospheric remote sensing, radio astronomy, and deep space exploration over the past three decades. Some typical scientific and engineering applications in space are discussed, which include the specifications, design issues, and the performance of various space THz antenna systems. Horn array antennas (synthetic aperture radiometry), reflector antennas fed by quasi-optical networks and traditional microwave networks have been widely applied in the designs for science missions. Finally, some promising THz antennas for future missions are introduced, and viewpoints on research challenges and future directions are given.

W-Band Beam-Tilted H-Plane Horn Array Antenna with Wideband Integrated Waveguide Feed Network Based on MMPTE

A W-band H-plane horn array antenna with tilted radiation beam based on waveguide structure is proposed in this paper. The designed antenna array consists of four H-plane antenna elements and a broadband feed network. The distribution of excitations is determined by the theory of maximum power transmission efficiency (MMPTE). A multiple branch coupler, two T-junctions and three fixed phase shifters are employed to construct the feed network, which can generate the required amplitude and phase in broadband frequency range from 80 GHz to 100 GHz. The computer numerical control (CNC) milling machines technology is employed to machine the feed network and antenna. All measured and simulated results are in good agreement, which verify the feasibility of the theory of MMPTE to generate a radiation beam directed to any angle from -35° to 35° with suitable excitation provided by the proposed feed network in this paper.

A MODEL OF REFLECTIONS OF PULSED RADIO SIGNALS FROM THE EARTH'S SURFACE AND ITS PRACTICAL USE IN ASSESSING THE ACCURACY OF AMPLITUDE DIRECTION FINDERS

The description of a mathematical model of reflections of pulse radio signals from the underlying Earth's surface and results of its practical use for estimation of accuracy of amplitude direction finders with horn antennas and antenna arrays of Vivaldi elements are presented. It is shown that the use of the proposed multipoint model of reflections from the ground surface allows an analysis of distortions of received pulse signals and estimation of errors of direction finding of radio emission sources by a monopulse amplitude direction finder on surface traces of radio wave propagation of different lengths.

Electrically large aperture horn array antenna with low side lobe level for Ku‐band frequency

AbstractUsing electrically large antennas for array applications may cause grating lobes and this can change the array pattern. To achieve a low side lobe level for boresight pattern for linear or planar array antennas, in the literature it is seen that the common method is the use of feeding each antenna with some amplitude distribution and keeping the distance between the antennas less than a wavelength. However, in this study the distance between the antennas is chosen to be greater than a wavelength. Therefore, the common methods cannot be used. To achieve a low side lob level in the radiation pattern for an array of antennas composed of antennas with a distance greater than one wavelength. The aperture length of each antenna is chosen to be variable and an analytical solution method is used to calculate the amplitude of each aperture field of the horn antennas. Thus, the determination of unit horns' optimal aperture lengths Li can be considered a multivariable optimization problem. This challenging problem was achieved using a novel meta‐heuristic optimization algorithm called the differential evolutionary algorithm (DEA), where the aperture lengths of each array element are taken as inputs to find the optimal side lobe level (SLL). Based on the obtained solutions, a 4 × 1 horn array antenna design alongside its feed network was designed for Ku‐band applications. The design of the array is simulated in CST simulation software, and the obtained simulated results had been compared with experimental results and counterpart designs in the literature.

Dual-Band Dual-Polarization Horn Antenna Array Based on Orthomode Transducers With High Isolation for Satellite Communication

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times4$ </tex-math></inline-formula> 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.

A novel near field radiation shaping technique by using data driven surrogate based optimization for nondestructive hyperthermia

AbstractHerein, a novel and computationally efficient near field shaping technique for nondestructive hyperthermia applications is presented. The aim of nondestructive hyperthermia studies is to treat cancer cells in the body without damaging the healthy cells using the focused near‐field characteristic of the antenna array. However, optimal near field shaping requires an optimization process for having accurately focus the energy into the desired coordinates, which is, a computational expensive and inefficient task due to the nature of full‐wave electromagnetic (EM) analysis. To enable computationally efficient, and accurate near field shape optimization, a surrogate model is required. To achieve this, the near field radiation of the designed horn antenna array in free space is obtained by using a fast and reliable technique, analytical regularization method (ARM). After that, by using Artificial Neural Network based regression algorithm, a data driven surrogate model is created using the data samples generated by ARM. By this means, near field shaping optimization for focusing the energy to the region where the tumor is located can be achieved, as a multi‐objective optimization problem to be solved via data driven surrogate model assisted optimization techniques. The performance results of K‐fold validation and hold‐out data sets for proposed data driven surrogate model are calculated using Mean Absolute Error metric which are obtained as 0.9 × 10−3 and 1.4 × 10−3 respectively. By observing the presented study case scenario, after 10 min of illumination with antenna array with optimally selected configurations, the targeted area (position of tumor) had reached to the critical temperature of 43 Celsius. Thus, it can be said that the proposed method is an efficient method, both in terms of (1) destroying tumor cells by heating without damaging the healthy cells, and (2) being a computationally efficient method.

Additively Manufactured Amplitude Tapered Slotted Waveguide Array Antenna With Horn Aperture for 77 GHz

In this work, a combined frontend of horn and slotted waveguide array antenna serving as feeding subsystem is presented. This setup allows to implement an amplitude taper in one plane while using the horn aperture to shape the far field radiation characteristics in the perpendicular plane independently and tailored to the individual demand of the application. Moreover, the feeding system is implemented as a loop resulting in a standing wave distribution for a wide frequency range in order to increase the antenna bandwidth. Two specimens with different horn apertures are additively manufactured in slotted waveguide technology from UV curable photopolymer resin using a digital light processing 3D printer and subsequently metal coated by electroless silver plating. A relatively large bandwidth of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{B}_{-10\text {dB}} = 7.2$ </tex-math></inline-formula> GHz and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{B}_{-15\,\text {dB}}$ </tex-math></inline-formula> of 4.9 GHz is achieved in measurements indicating a relative bandwidth of 9 % and 6 % respectively. Antenna Gain is characterized as 17.5 and 20.17 dBi in measurements while maintaining a sidelobe level of 20–22.5 dB at 77 GHz and exhibiting a radiation efficiency of 78.9 and 79.4 %. The proposed antenna architecture provides a flexible approach for beam shaping in applications where azimuth and elevation planes exhibit different or contrary requirements, e.g. broad vs. narrow field of view - especially suitable for automotive MIMO-radar sensors.

A wide Bandwidth Pyramidal Horn Antenna with Enhanced Gain Using Metasurface layer

A new design of a pyramidal horn antenna operating at 8-18 GHz based on the waveguide structure is presented in this paper. A metasurface layer, which consists of a set of periodic unit cells, is employed on the E-plane walls of the horn antenna. This is to enhance the realised gain and bandwidth. The unit cell shape is chosen based on the cavity resonator theory. The design method of the unit cells is analyzed and presented here using the Computer Simulation Technology (CST) microwave studio. The scattering parameters of a single unit cell are optimised in order to operate it at the designed operating frequencies. Compared to a conventional pyramidal horn, the proposed horn antenna gain improves up to 10 dBi. The peak gain is 23.7 dBi and the reflection coefficient at S11= -10 dB is 5%. The radiation patterns are well shaped, and are stable over a large operating frequency range. The proposed pyramidal horn antenna is relatively low profile and may be of interest in satellite communication systems. References ABDULKARIM, Y. I., AWL, H. N., MUHAMMADSHARIF, F. F., KARAASLAN, M., MAHMUD, R. H., HASAN, S. O., IŞıK, Ö., LUO, H. &amp; HUANG, S. 2020. A low-profile antenna based on single-layer metasurface for Ku-band applications. International Journal of Antennas and Propagation. ASL, A. N., YOUSIF, B. &amp; AL-ZALABANI, M. 2020. Design, modeling, and fabrication of a new compact perfect metamaterial X-band absorber. AIP Advances, 10, 025328. CHEN, H.-T., TAYLOR, A. J. &amp; YU, N. 2016. A review of metasurfaces: physics and applications. Reports on progress in physics, 79, 076401. CHEN, X. &amp; GE, Y. 2017. Enhancing the radiation performance of a pyramidal horn antenna by loading a subwavelength metasurface. IEEE Access, 5, 20164-20170. CHU, L. &amp; BARROW, W. 1939. Electromagnetic horn design. Electrical Engineering, 58, 333-338. ESSELLE, K. P. 2007. A low-profile compact microwave antenna with high gain and wide bandwidth. IEEE transactions on antennas and propagation, 55, 1880-1883. GE, Y., LIN, C. &amp; LIU, K 2018. A Metasurfaced Pyramidal Horn Antenna for Circularly-Polarized Applications. IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP), IEEE, 517-518. GE, Y., SUN, Z., CHEN, Z. &amp; CHEN, Y.-Y. 2016. A high-gain wideband low-profile Fabry–Pérot resonator antenna with a conical short horn. IEEE Antennas and Wireless Propagation Letters, 15, 1889-1892. LI, Y., GE, L., WANG, J., DA, S., CAO, D., WANG, J. &amp; LIU, Y. 2019. 3-D printed high-gain wideband waveguide fed horn antenna arrays for millimeter-wave applications. IEEE Transactions on Antennas and Propagation, 67, 2868-2877. LIER, E. &amp; SHAW, R. 2008. Design and simulation of metamaterial-based hybrid-mode horn antennas. Electronics letters, 44, 1444-1445. LIN, C., GE, Y., BIRD, T. S. &amp; LIU, K. 2018. Circularly polarized horns based on standard horns and a metasurface polarizer. IEEE Antennas and Wireless Propagation Letters, 17, 480-484. MARHEFKA, R. J. &amp; KRAUS, D. 2002. Antennas for all Applications. Antennas for all applications. MAYBELL, M. J. &amp; SIMON, P. S. 1993. Pyramidal horn gain calculation with improved accuracy. IEEE transactions on antennas and propagation, 41, 884-889. MORADI, A. &amp; MOHAJERI, F. 2017. Side lobe level reduction and gain enhancement of a pyramidal horn antenna in the presence of metasurfaces. IET Microwaves, Antennas &amp; Propagation, 12, 295-301. PAN, B., LI, Y., PONCHAK, G. E., PAPAPOLYMEROU, J. &amp; TENTZERIS, M. M. 2009. A 60-GHz CPW-fed high-gain and broadband integrated horn antenna. IEEE Transactions on Antennas and Propagation, 57, 1050-1056. WANG, P., WU, Q., HE, R.-B. &amp; LUO, W. 2019. Gain and radiation pattern enhancement of the H-plane horn antenna using a tapered dielectric lens. IEEE Access, 7, 69101-69107. WU, Q., SCARBOROUGH, C. P., GREGORY, M. D., WERNER, D. H., SHAW, R. K. &amp; LIER, E. Broadband metamaterial-enabled hybrid-mode horn antennas. 2010 IEEE Antennas and Propagation Society International Symposium. IEEE, 1-4. WU, Q., SCARBOROUGH, C. P., WERNER, D. H., LIER, E. &amp; SHAW, R. K. 2013. Inhomogeneous metasurfaces with engineered dispersion for broadband hybrid-mode horn antennas. IEEE transactions on antennas and propagation, 61, 4947-4956. WU, Q., SCARBOROUGH, C. P., WERNER, D. H., LIER, E. &amp; WANG, X. 2012. Design synthesis of metasurfaces for broadband hybrid-mode horn antennas with enhanced radiation pattern and polarization characteristics. IEEE transactions on antennas and propagation, 60, 3594-3604.

Performance Analysis of Incident Power Density Evaluation by Inverse Source Method for Compliance Assessment at Quasi-Millimeter and Millimeter Wave Bands

In modern communication systems including the fifth-generation mobile communication system (5G), quasi-millimeter, and millimeter wave frequencies above 6 GHz are utilized. At these frequencies, the incident power density is employed as a metric to assess the compliance of wireless devices to human exposure limits in international guidelines and national regulations. In this article, the performance of the inverse source method (ISM) for incident power density evaluation is investigated in terms of accuracy and operational costs, i.e., measurement and computational costs. The ISM is based on the surface equivalence theorem, and it reconstructs the incident power density close to the device under test from a field measured in a more distant region. The comparison of the performance between the ISM and the conventional plane-wave spectrum method by computational simulation shows that the ISM has an advantage over the conventional method in robustness to the truncation of the measurement region. The ISM reduces the number of measurement points to a quarter for the reconstruction of the spatially averaged incident power density in an error less than 0.4 dB. These findings in the computational simulations are also validated by the measurements of a standard horn antenna and array antennas operated at 28 GHz.

Four element three‐dimensional SIW horn antenna array for high‐frequency applications

A low-profile three-dimensional substrate integrated waveguide (SIW) horn antenna array with its novel feeding structure is proposed in this article. The feeding element is capable of transforming the wave from one plane to its orthogonal plane. Such type of three-dimensional SIW, H-plane horn antenna design is not available in the existing literature. The design is proposed to provide high gain for radar, 5G, and satellite communication applications. The single SIW horn antenna does not have significant gain at the desired frequencies. When the antenna element is loaded with dielectric the gain improves by 1.4 dB. The antenna elements are further arranged in a box shape, forming a three-dimensional array, which improves the gain significantly. Such structure shows dual band characteristics and provides gain of 11.3 dB at 28.26 GHz and 9.64 dB at 29.41 GHz. The same three-dimensional design when loaded with dielectric at the aperture end also show a dual band behavior and improve the gain further to 12.5 dB at 28.12 GHz and 12.55 dB at 29.28 GHz. The proposed three-dimensional antenna designs are compared to four element linear array designs, and it shows substantial improvement in gain for the desired frequency.

Wideband horn antenna array with microstrip feed based on multilayered dielectric substrate board

A wideband, high-gain planar millimeter-wave horn antenna array with low sidelobe has been proposed. The proposed design is based on the multilayered dielectric substrate board process and totally has 10-layer substrates, including the feeding network layer. The horn element is composed of the stratified dielectric material in the longitudinal direction to achieve a wide bandwidth. Simultaneously, the profiled wall of the horn can further enhance the bandwidth and stabilize the radiation performance. A 4 × 4 array prototype with triangular lattice is optimally designed, fabricated, and measured. The results show that the simulated impedance bandwidth ranges from 22 GHz to over 45 GHz, the measured bandwidth is from 21.9 GHz to over 40 GHz (limited by the experiment conditions). The simulated and measured peak gains are 21.86 dBi and 19.7 dBi, respectively. Besides, the sidelobe levels are lower than −17 dB from 21.9 GHz to 32 GHz. The proposed antenna is believed to be a good candidate for the millimeter-wave point-to-point communication links.

Broadband RF Phased Array Design with MEEP: Comparisons to Array Theory in Two and Three Dimensions

Phased array radar systems have a wide variety of applications in engineering and physics research. Phased array design usually requires numerical modeling with expensive commercial computational packages. Using the open-source MIT Electrogmagnetic Equation Propagation (MEEP) package, a set of phased array designs is presented. Specifically, one and two-dimensional arrays of Yagi-Uda and horn antennas were modeled in the bandwidth [0.1–5] GHz, and compared to theoretical expectations in the far-field. Precise matches between MEEP simulation and radiation pattern predictions at different frequencies and beam angles are demonstrated. Given that the computations match the theory, the effect of embedding a phased array within a medium of varying index of refraction is then computed. Understanding the effect of varying index on phased arrays is critical for proposed ultra-high energy neutrino observatories which rely on phased array detectors embedded in natural ice. Future work will develop the phased array concepts with parallel MEEP, in order to increase the detail, complexity, and speed of the computations.

A Dual-Wideband Structure-Shared Antenna With Self-Diplexing Property for High-Power Microwave Application

This communication proposes a dual-wideband antenna that is composed of a shared structure with self-diplexing capability. The antenna structure is a combination of a tapered slot antenna (TSA) operating in the range of S- to X-bands and a horn antenna array that operates in Ka-band. The structure-shared antenna has high design freedom for each band with controllable properties for a dual-wideband application. The back-lobe level is greatly reduced at both bands due to the implementation of shared structure. The isolation between two ports is enhanced without additional decoupling structures that develops the self-diplexing characteristic of the antenna. Moreover, the electric field distributions of the proposed antenna are analyzed through simulation, which proves its potential in high-power microwave (HPM) application.

Isolation Enhancement for W-Band Coplanar Array Antennas Based on Silicon Micromachining Technology

A W-band decoupling structure sandwiched between a pair of high-gain step-profiled horn array antennas using the silicon micromachining technology is proposed. To suppress the surface wave, 18 choke slots with a depth of one quarter wavelength at 94 GHz are arranged in a triangular-grid array and the isolation can be averagely improved by about 7 dB with a range of 2-20 dB. This decoupling structure and two W-band coplanar array antennas are fashioned and fully integrated together by the silicon micromachining technique. Five 400 μm thick and one 650 μm thick silicon wafers are utilized and the total thickness of the antennas is 2.65 mm. Thanks to this technology, light weight, compact size, and high integration of the decoupling structure and array antennas can also be achieved. Additionally, the two array antennas share a common ground plane within a small edge-to-edge spacing of 6.05 mm where TM surface waves exist. Experimental studies validate the performance of the proposed triangular-grid choke slot array.

Generating and Detecting Broad-Band Underwater Multiple OAMs Based on Water-Immersed Array

In this paper, we focus on the generation of broadband underwater vortex waves carrying multiple OAMs. Based on a wideband underwater antenna, a water-immersed horn antenna array is designed and tested. The experimental results, which are in agreement with the simulation ones, validate that the proposed antenna array can readily generate high-quality vortex waves. To further validate the performance of the proposed underwater antenna array, experimental verifications of 2-D underwater imaging for the targets of two corner reflectors have been carried out, and the result shows that the targets can be distinguished efficiently. Meanwhile, two generation methods and one detection method of the multiplexed OAMs are also presented, from which the multiplexed OAMs can be generated and detected efficiently. And the performances of two generation methods have also been compared and discussed, from which we can know that the first generation method with a smaller structure costs lower and is more efficient.

An Analysis of Metaheuristic Algorithms Used for the Recovery of a Failed Antenna Element in an Antenna Array

A ground-based synthetic aperture radar system (GB-SAR) comprising of 12 horn antennas in its transmitter section and 12 Vivaldi antennas in its receiver section is used for the monitoring of the Tessina landslide in Italy and the sinking of the Costa Concordia ship in Italy. Alternate 2×6 geometry of 12 coaxial cavity horn antennas have been proven to yield a higher half-power beamwidth and low peak sidelobe ratio resulting in a better quality of the image captured. This 2×6 planar array, when fed with power according to the Dolph Chebyshev weighting polynomial, removes side lobes entirely and results in an increase half-power beamwidth (HPBW) value. A failure of any single element in the 2×6 array could lead to the alteration of the radiation pattern thereby jeopardizing the monitoring activity. This paper explores the usage of metaheuristic algorithms in order to recover the weight of the principal antenna element of the 2×6 coaxial cavity horn antenna array. The algorithms explored are Gradient Descent, Simulated Annealing, Firefly algorithm, Bat algorithm, Flower Pollination algorithm, Cuckoo search algorithm, and Harmony Search algorithm. Among these ones, the Firefly algorithm performs the best in finding the weight of the failed antenna element of the 2×6 planar array.

Horn and lens antenna array with chevron‐shaped prism for 77‐GHz automotive radar with dual‐range sensing and a dual field of view

A transmitter antenna array composed of two horn and lens antennas sharing a novel chevron‐shaped prism and one horn and lens antenna without such a prism has been investigated for 77‐GHz‐band automotive radar with dual‐range sensing and a dual field‐of‐view (FOV). The horn and lens antenna without the prism is directed at boresight to produce a radiation pattern with a narrow FOV for long‐range detection. The portions of the prism output surface corresponding to the two antennas that share the prism are angled in opposite directions to tilt their radiation patterns to the left and right and thereby provide a wide FOV in azimuth for middle‐range detection. The prism created a smooth radiation pattern in the major lobe when the tilt angle was large enough to achieve an azimuth FOV of more than ±35°. A fabricated transmitter antenna array achieved a gain of 21.5 dBi and a half‐power beam width of 22° at boresight for long‐range detection and one of more than 15.5 dBi within azimuth angles of ±35° for middle‐range detection at 76.5 GHz. This antenna array for long‐ and middle‐range detection had reflection coefficients (S11) of less than −14 and −17 dB, respectively, from 76 to 77 GHz. The antenna array thus produces the beams required for dual‐range dual‐FOV radar. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Designing a Water-Immersed Rectangular Horn Antenna for Generating Underwater OAM Waves

In order to extend the applications of vortex waves, we propose a water-immersed rectangular horn antenna array for generating underwater vortex waves carrying the orbital angular momentum (OAM). Firstly, a single dielectric-loaded rectangular horn antenna with the central frequency of 2.6 GHz was designed for generating underwater electromagnetic (EM) waves. Due to the supplementing dielectric-loaded waveguide in this single antenna, the problems with difficult sealing and fixation of the feed probe could be solved effectively. The simulation results show that it has a good impedance characteristics (S11 &lt; −10 dB) and reasonable losses (less than 3.5 dB total for two antennas and a coaxial line) from 2.5 GHz to 2.7 GHz. Experiments on the single antenna were also carried out, which agree well with the simulations. Based on the designed single antenna, the water-immersed rectangular horn antenna array was proposed, and the phase gradient from 0~2π was fed to the horn antennas for generating underwater OAM waves. The simulation results demonstrate high fidelity of the generated OAM waves from the intensity and phase distributions. The purity of the generated OAM modes was also investigated and further verifies the high fidelity of the generated OAM waves. The generated high-quality OAM waves meet the requirements for underwater applications of OAM, such as underwater communication and underwater imaging.