Conventional Horn Research Articles

Transforming Linear to Circular Polarization on Horn Antennas by Using Multiple-Layer Frequency Selective Surfaces.

This article presents a technique for transforming the polarization of a pyramidal horn antenna by adding multiple layers of frequency-selective surfaces in front of the aperture, in order to rotate the direction of the electric field. Thus, two orthogonal components with the same magnitude, phase-shifted by 90°, are generated. Each frequency-selective surface consists of skewed λ/2 dipoles. Compared to other similar structures, our antenna system combines the field radiated from the horn aperture with the field scattered by parallel frequency-selective surface structures spaced on the same principle as that for designing a Yagi-Uda antenna array. The proposed horn antenna with multiple frequency-selective surfaces can be used as a feed element for a parabolic reflector antenna for maritime satellite communication systems in the X-band or in the lower part of the Ku band, or as part of a sensor for finding the direction of arrival of a wave, in order to orientate an antenna system. The concept was successfully validated on the basis of simulation and measurements. The proposed technique provides a close to unit axial ratio together with a 3 dB increase in gain compared to the conventional horn antenna, at low manufacturing costs.

Stable phase‐centre horn antenna using 3D printed dielectric rod for aperture efficiency improvement of space‐fed antennas

The design strategy to stabilise the phase centre (PC) of the conventional horn antenna using a shaped dielectric rod is presented for aperture efficiency improvement of space-fed antennas. In most practical horn antennas, PC location has significant variations with frequency leading to phase error loss and aperture efficiency reduction over the bandwidth of interest. To overcome this drawback, based on physical reasoning, shaped dielectric rods with appropriate excitation mode are designed and placed on the aperture of conventional rectangular and conical horn antennas. The simulation results show that using a shaped dielectric rod inside the horn antenna leads to a decrease in phase-centre variations versus frequency without disturbing the radiation pattern and reflection coefficient. To investigate the performance, a conical corrugated horn antenna loaded by a conical tapered dielectric rod is used as a feed of the transmitarray antenna. Using a shaped dielectric rod fabricated by 3D printing technology, the PC variations of the proposed horn decrease from 1.06 λ to 0.08 λ over the X-band (λ at 8 GHz). The measurement of the fabricated transmitarray antenna shows an improvement of maximum aperture efficiency from 55% to 64.7% at 10 GHz. The aperture efficiency bandwidth above 50% level is also increased from 1 to 2.2 GHz.

Gain enhancement of a SIW H-plane horn antenna using of metamaterial array

Abstract In this paper, a novel, compact and high gain H-plane horn antenna with Substrate Integrated Waveguide (SIW) technology is examined for X-band applications. To increase the gain, an array of metamaterials is used by cutting the gap in the aperture area of the antenna in high metallization. After examining the size and position of the metamaterial unit cell and several array elements, which act as a focusing structure, and in addition, by reducing the electric permittivity coefficient of the substrate and consequently reducing the losses, an increase in gain is achieved. The performance of the proposed SIW horn antenna with metamaterials has been compared with the SIW conventional horn antenna without metamaterials. To highlight this point, the proposed antenna was designed with CST software. Then, it was fabricated and measured. Measurements show that the gain of the modified antenna is 9.2 dBi, which is 6.2 dBi higher than a conventional antenna.

A multi-frequency sonochemical reactor utilizing a cylindrically focused acoustic wavefield for improved sonochemical efficiency

Sonochemistry involves several steps. First, an acoustic wave must be generated with sufficient energy to nucleate cavitation. This cavitation event must then be energetic enough to produce radicals through the sonolysis of the gas or vapor molecules in the bubble. Finally, these radical species must survive long enough to react with other chemical species to yield the desired product. The sonochemical efficiency (SE) is thus defined as the ratio of the product yield to the input acoustic power. Here, we put forward a novel approach to enhancing the SE by designing a multi-frequency (0.25 to 1MHz) sonochemical reactor that reflects a cylindrically spreading acoustic wave 180°. The reflected wave converges to cylindrically shaped high-intensity “hot zone” positioned along the axis of the reaction vessel. At modest power input, we detected noise with a passive cavitation detector in air-saturated water, suggesting the direct nucleation of cavitation. Using the Weissler reaction to determine the production of hydroxyl radicals, we determined the SE of our sonochemical reactor at various operation conditions. We also compared these values to conventional bath, horn, and plate sonochemical reactors. The comparison suggested that our reactor design had a better sonochemical efficiency for the Weissler reaction.

Shape optimization of acoustic horns for improved directivity control and radiation efficiency based on the multimodal method.

The multimodal method is used to develop an approach for optimizing the shape of axisymmetric acoustic horns for both well-controlled directivity and high radiation efficiency over a wide frequency range. A horn with an arbitrary profile can be efficiently modeled with the multimodal method by projecting the wave field over transverse modes in connected short cylinders; the radii of the cylinders are used directly as design variables. Many design variables are employed in the optimization process to ensure design flexibility and computational accuracy. The relative weights for the design objectives of constant directivity, high radiation efficiency, and acceptable shape smoothness are adjusted by two coefficients in the objective function. The optimization problem is solved with a gradient-based algorithm, which takes advantage of algebraic gradient expressions. Numerical experiments demonstrate that the optimization procedure generates smooth horn contours that exhibit considerably improved performance over the target frequency band. Interestingly, a high-quality horn produced with moderate weight coefficients is similar in shape to constant-directivity horns invented earlier while having good low-frequency loading properties. The proposed method provides an attractive alternative to conventional horn design approaches.

Improvement of sectoral horn nanoantenna based on arc directors for point to point communications

This paper presents directivity and gain enhancement of sectoral horn nanoantenna (NA) with arc directors for point to point communications systems. The effect of adding three directors to the sectoral horn NA is investigated. The directors pull the NAs radiation toward its axis which concentrates the electromagnetic waves and increases the directivity. This in turn improves the radiation characteristics of the NA especially the gain and directivity. The suggested structure is simulated using finite integration technique (FIT) in terms of gain, directivity, efficiency and electric field distribution. In this regard, the directivity of the NA is increased from 13.8 to 20.7 with an enhancement of 50% at λ = 1550 nm by adding the arc directors. Further, an improvement of 82.2% is also accomplished in the NA gain. Moreover, the total efficiency has an enhancement of 10% compared to the conventional horn NA without directors. The proposed design is also used to construct optical wireless nanolink. It is found that the transmission power in the optical wireless nonalink with directors is improved. Additionally, 6 dB enhancement is attained over the nanolink based on horn NA without directors at wavelength of 1550 nm. The reported wireless nanolink covers the communications applications in the optical c-band.

Flat lens design using phase correction technique for horn antenna applications

A design of a flat dielectric lens is presented in this study to enhance directivity of a pyramidal horn antenna. The horn antenna is proposed to cover frequency of medical imaging system, which is between 5 and 6 GHz, and dielectric lens is designed based on phase correction techniques. The spherical waves produced by conventional horn antenna is being transform to planar waves by resorting flat lens in order to achieve a highly directive radiation in the farfield region. This is done by drilling numerous holes with different diameters through the dielectric material to produce different phase delay. The radiation characteristics of the lens are simulated using CST Microwave Studio and then compared with measured results. The results showed a good performance for radiation pattern when the lens is attached. This proposed design shows a significant increment of sidelobe level and 3-dB beamwidth between 5 and 6 GHz.

Wide-band gain enhancement of a pyramidal horn antenna with a 3D-printed epsilon-positive and epsilon-near-zero metamaterial lens

AbstractIn this article, we present a simple, low-cost solution for the gain enhancement of a conventional pyramidal horn antenna using additive manufacturing. A flat, metamaterial lens consisting of three-layer metallic grid wire is implemented at the aperture of the horn. The lens is separated into two regions; namely epsilon-positive and epsilon-near-zero (ENZ) regions. The structure of the ENZ region is constructed accounting the variation of relative permittivity in the metamaterial. By the phase compensation property imparted by the metamaterial lens, more focused beams are obtained. The simulated and measured results clearly demonstrate that the metamaterial lens enhances the gain over an ultra-wide frequency band (10–18 GHz) compared to the conventional horn with the same physical size. A simple fabrication process using a 3D printer is introduced, and has been successfully applied. This result represents a remarkable achievement in this field, and may enable a comprehensive solution for satellite and radar systems as a high gain, compact, light-weighted, broadband radiator.

Compact High-Gain Si-Imprinted THz Antenna for Ultrahigh Speed Wireless Communications

A low-profile and high-gain Gaussian beam antenna (GBA) operating at 1 THz is demonstrated for the first time. Imprint and dry etching technologies in silicon are employed. A complementary antenna feed based on the magnetoelectric dipole is proposed for enhancing the radiation characteristics of the antenna. The microfabrication technologies are compatible with the Si-based integrated circuit manufacturing process. The terahertz (THz) antenna is realized with over 20 dBi in antenna gain. With high-precision fabrication technologies, a highly efficient THz GBA with smooth morphology and much lower profile than conventional horn and lens antennas is developed. Moreover, the antenna has the characteristic of low sidelobe levels which is advantageous in many wireless applications.

A Low-Profile Quad-Beam Transmitarray

In this letter, a novel method is proposed to design a low-profile multibeam transmitarray. Instead of a conventional horn feed, a slot array (SA) feed is used to illuminate uniformly same size transmitarray aperture (TA) in near field with a plane wave excitation, and TA is designed to transform plane wave to high gain multibeam pattern. The separation between SA feed and TA is independent of aperture size, so a very small separation is selected to achieve a low-profile transmitarray. A quad layer 3-dipole unit cell with 360° phase shift range is used as a transmitarray element. A modified intersection approach is used to optimize distribution of transmitarray elements on aperture to synthesize multibeam pattern. Finally, a prototype of Ku-band quad-beam transmitarray antennais fabricated and tested. The designed transmitarray shows good quad-beam performance with reduced profile and good match has been observed between simulated and measured results.

Reconfigurable Dual-Fed Horn With Pattern Switchability Realized by SIW Technology

A novel multihorn antenna using the substrate integrated waveguide (SIW) technology is discussed in this communication. Conventional SIW-inspired horns, being the extensions of planar H-plane horn antennas, portray a fan-shaped beam, with a narrow H-plane and a wide E-plane radiation characteristics. The present design employs this feature to produce a crossed horn, in which both E- and H-plane radiations can be realized by individually exciting the two sectoral horns, while terminating the other port to a matched load. When both the ports are excited, a spot beam is realized, representing a pattern similar to that of a pyramidal horn. Such an antenna should find its potential applications in systems requiring radiation switchability/pattern diversity from a single embodiment.

Creating a Gain Improvement Technique for a Horn Antenna using a Metamaterial Structure Inserted with a Thin Dielectric Sheet

Objective: This paper proposed a new technique for the metamaterial on the structure of the curved-woodpile Electromagnetic Band Gap (EBG) inserted with a dielectric slab for gain improvement in a conventional rectangular horn antenna. Methods: We described a method to enhance gain by transferring the electromagnetic fields from the aperture of a horn through the EBG structure. Furthermore, we present the design procedures for inserting a dielectric slab into two layers of the EBG structure for the reduction of distance between the horn and proposed EBG structure. Results and Conclusions: Such a proposed technique not only has the advantage of decreasing the total length of the antenna system but also providing higher gain with a low profile structure. This idea has been verified by both simulation and experimental results. The fabricated antenna can achieve 23.9 dBi of gain or higher than the gain, which is obtained using a conventional rectangular horn antenna at around 7 dBi at an operating frequency of 10 GHz. It is apparent that a good qualitative agreement between the measurements and simulations was achieved.

Development a new wideband substrate integrated waveguide H-plane horn antenna loaded with periodically diamond patches

This paper presents a new wideband Substrate Integrated Waveguide (SIW) H-plane horn antenna. A few rows of diamond patches are printed on the top and bottom side of the dielectric slab at front of the radiating aperture of a conventional horn to improve impedance matching. The proposed antenna is numerically investigated using a software package and a prototype of the antenna is made to validate the obtained simulated results. The measured results show that the introduced antenna provides 22.7% impedance bandwidth, which covers from 20.8 GHz to 26.15 GHz with stable end-fire radiation patterns, while Side Lobe Level (SLL) is lower than −10 dB over the operating bandwidth.

Designing of Ultrasonic Horns to Improve Amplitude Uniformity in Ultrasonic Metal Welding

The ultrasonic metal welding has been used extensively in many fields because it can weld thin layers of highly conductive and dissimilar materials with high reliability. In particular, one-wave length horns with four welding tips on both sides of the horn are widely used for welding positive and negative electrodes and tabs of rechargeable lithium ion batteries. As the vibrational amplitude of each tip is known to be non-uniform, this causes some problems in welding performance. In this study, the one-wave length horn which has four welding tips on both sides of the horn is newly designed to improve amplitude uniformity of each tip. The design of experiment technique is employed to determine the optimum configuration of the horn. The modal analysis and harmonic response analysis are repeatedly conducted to obtain the uniform amplitude of horn tips, and stress distribution in the horn is analyzed finally. It is shown that the uniformity of amplitude can be improved by making appropriate grooves on both sides of the conventional horn.

A 60 GHz Wideband Switched-Beam Dipole-Array-Fed Hybrid Horn Antenna

This letter presents a wideband switched-beam dipole-array-fed hybrid horn antenna presented for the 60 GHz unlicensed band. Compared to a dipole array, a 6.7 dB gain improvement was achieved, and the 6.5 GHz bandwidth is further improved from 7.6 GHz by forming additional resonance, which is caused by the gap between the dipole array and horn structure. Furthermore, compared to the outcome of a conventional horn antenna, the radiation angle can be varied widely. The proposed antenna exhibits wideband characteristics with a 24.3% overlapped bandwidth of the impedance and a 3 dB gain, a 13.4 dBi peak gain, and a beam-switchable range of 105°. To the best of the authors’ knowledge, the proposed antenna exhibits the widest bandwidth and coverable range from among the reported 60 GHz switched-beam arrays.

2-D Scannable 40-GHz Folded Reflectarray Fed by SIW Slot Antenna in Single-Layered PCB

Folded reflectarray antenna features high gain, low profile, and low sidelobe level, but also faces several challenges in scannability, manufacturing, assembling, and integration with planar circuits, especially at millimeter-wave and terahertz frequencies. To alleviate these issues, this paper presents a slot antenna based on substrate integrated waveguide (SIW) to replace conventional horn. This SIW slot antenna is then inherently integrated with reflectarray elements in the same single-layered printed circuit board (PCB) for the first time. Moreover, this folded reflectarray is able to scan its narrow beams in 2-D, by controlling the polarizing grids. The whole reflectarray is fabricated by the commercial low-cost PCB process and can be highly integrated with planar active circuits. Measured results show that the proposed reflectarray achieves a 2-D scanning zone of 14° $\times$ 14°, a gain of 27.4 dBi, and a cross-polarization level less than −24 dB. The proposed folded reflectarray is promising for several application scenarios including millimeter-wave high-resolution imaging and fifth-generation communications.

Side lobe level reduction and gain enhancement of a pyramidal horn antenna in the presence of metasurfaces

In this study, the design method and experimental presentation of low-refractive-index metasurfaces have been reported. These metasurfaces are employed in the interior E-plane walls of a pyramidal horn antenna. The target is a linearly polarised horn antenna with low side lobe levels (SLLs) and symmetric radiation patterns in the Ku band (13–18 GHz) for satellite communications. Particle swarm optimisation algorithm has been applied to the design procedure to achieve low-loss dispersion-engineered metasurfaces with desirable surface impedance characteristics. The metasurfaces were fabricated using precise low-cost printed-circuit board technique. There was perfect agreement between the measurement and simulation results. The fabricated horn showed low SLLs and an increase in the gain across the entire bandwidth. The SLLs are reduced by 14–29 dB in the E-planes and the gain is improved by 1.2–2.3 dB compared with a corresponding conventional horn. The far field radiation patterns of the metahorn verify the metasurface design approach. Furthermore, this method assures a lighter horn with an easier manufacturing technique in comparison with the other conventional horns, such as corrugated horns.

Energy Transfer Using Gradient Index Metamaterial

The gradient refractive index structure in this paper is used to increase the quantum of energy transfer. This is done by improving the directive gain of the pyramidal horn antenna at a frequency of 10 GHz. A three-dimensional array of closed square rings is placed in front of the horn antenna aperture to form a gradient refractive index structure. This structure increases the directive gain by 1.6 dB as compared to that of the conventional horn antenna. The structure nearly doubles the wireless power transfer quantum between the transmitter and the receiver when placed at both ends. The increase in the directivity is achieved by converting the spherical wave emanating from the horn to a plane wave once it passes through the structure. This transformation is realized by the gradient refractive index structure being placed perpendicular to the direction of propagation. The gradient refractive index is constructed by changing the dimensions of a closed square ring placed in the unit cell of the array. The change in the refractive index gives rise to an improvement of the half power beam width and side lobe level compared to that of the normal horn. The design and simulation were done using CST Studio software.

L‐band horn antenna radiation enhancement for GPR applications by loading a wire medium

AbstractAn L‐band horn antenna with modified radiation pattern is customized for ground penetrating radar (GPR) applications. The conventional horn antenna is loaded by a metallic wire medium to enhance the antenna radiation pattern, directivity and gain with reduction of the side‐lobes level. These properties are strongly desirable for GPR applications.

Traffic flow detection and statistics via improved optical flow and connected region analysis

Moving vehicle detection plays an important role in intelligent transportation systems. One of the common methods used in moving vehicle detection is optical flow. However, conventional Horn–Schunck optical flow consumes too much time when calculating dense optical flows so that it cannot meet the real-time requirements. This paper proposes a novel improved Horn–Schunck optical flow algorithm based on inter-frame differential method. In our algorithm, optical flow field distribution is only calculated for pixels with larger gray values in the difference image, while for other pixels we applied the iterative smooth. The number of vehicles in the videos of traffic conditions is counted by setting the virtual loop and detecting optical flow information. To extract the moving vehicle as accurately as possible, we also propose a method to obtain moving vehicle minimum bounding rectangle based on the connected region analysis. Finally, we compare the improved optical flow with other four optical flow algorithms in moving vehicle extraction and vehicle flow detection, from which our method gives a much more accurate result.