Horn Aperture Research Articles

Effective method to design large‐size horn arrays with high gain and suppressed sidelobes using meta‐screens

This study presents a novel design of a high gain and suppressed sidelobes horn array covered with meta-screens. The meta-screens are composed of two layers of periodic slot structure that divide the large-size horn into an equivalent leaky-wave array. A synthesis procedure is therefore proposed to analyse the leaky-wave array, resulting in high gain and low sidelobes. The element pattern of the leaky-wave array is derived from the equivalent network of the corresponding leaky-wave antenna, and the element excitations are determined by the scattering results from the horn aperture field distribution. The synthesised pattern of a horn with the meta-screens is calculated by using the element pattern and excitations. Based on the synthesis procedure, the optimised horn and meta-screens with a uniform aperture field are achieved efficiently. Adopting the horn and meta-screens in an arbitrary N × N array, the array demonstrates a high gain and suppressed sidelobes. To verify the proposed method, a 2 × 2 array prototype is designed and fabricated. The prototype features the gain of 27.4 dB and the sidelobe level less than -10 dB. A good agreement between the predicted and measured results proves the effectiveness of the method.

A 18–40 GHz Substrate Integrated Waveguide H-Plane Horn Antenna

A 18-40 GHz wideband substrate integrated waveguide (SIW) H-plane horn antenna is proposed for applications on both the K- and Ka-bands. By employing a grating transition in front of the horn aperture, the impedance bandwidth (IBW) of the proposed antenna is broadened considerably. A broadband double-ridge waveguide (DRW)-to-SIW transition is also developed as the feeding structure for the proposed SIW H-plane horn antenna. The DRW is adopted to support a wider IBW as compared to that of a rectangular waveguide. A prototype of the proposed antenna is experimentally verified. The measured results show that the IBW for |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | ≤ -10 dB ranges from 18 GHz to more than 40 GHz, covering the entire Kand Ka-bands. The measured gain varies from 7.52 to 15.37 dBi with an average gain of 11.58 dBi. In addition, the endfire radiation patterns are observed and maintained within the IBW.

Quasi-corrugated substrate integrated waveguide H-plane horn antenna with wideband and low-profile characteristics

A wideband H-plane horn antenna based on quasi-corrugated substrate integrated waveguide (SIW) technology with a very low profile is presented in this article. Open-circuited microstrip stubs are applied to create electric sidewalls of the quasi-corrugated SIW structure. The quasi-corrugated SIW H-plane horn antenna shows high performance and simple structure. A specify-shaped horn aperture is utilized, so that the poor impedance matching owing to the structure restriction can be smoothened. The structure is simulated by ANSYS HFSS and a prototype is fabricated. The measured results match well with the simulated ones. An enhanced impedance bandwidth ranging from 5.3 GHz to 19 GHz (VSWR < 2.5) is achieved. The presented antenna also brings out stable radiation beam over the same frequency band.

Robust Design of 3D-Printed 6–18 GHz Double-Ridged TEM Horn Antenna

A robust design of a 3D-printed 6–18 GHz double-ridged TEM horn antenna is proposed in this paper. The designed TEM horn antenna has two parts: an adaptor and a horn aperture. The adaptor is realized using a double-ridged waveguide to extend the operating bandwidth of the dominant mode (TE10 mode). Meanwhile, the horn aperture section is implemented in an exponentially tapered configuration to match the impedance of the double-ridged waveguide with the intrinsic impedance. The performance of the initially designed antenna shows that the reflection coefficient and gain levels are less than −13 dB and greater than 5.5 dBi within the 6–18 GHz band, respectively. The initial design was well done, but the noise factors that may occur during the manufacturing process were not taken into account. To design an antenna considering these noise factors, the parameters of the initial design are optimized by a novel robust design method also proposed in this paper. The robustness of the antenna optimized by the proposed method is approximately 12.4% higher than that of the initial antenna. The validity of the proposed method was tested by fabricating the antenna. A prototype of the optimized antenna with the proposed robust design method is fabricated using a 3D printer with a stereolithographic apparatus attached, and the surface of the frame is covered by a nano-silver plating. The measured results of the fabricated antenna are in good agreement with the simulation results over the operating band. The measured −10 dB reflection coefficient bandwidth of the antenna can cover 6–18 GHz. In addition, the measured gain ranges from 4.42 to 10.75 dBi within the 6–18 GHz band.

Broadband SIW Horn Antenna Loaded With Offset Double-Sided Parallel-Strip Lines

A novel substrate integrated waveguide horn antenna loaded with offset double-sided parallel-strip lines (DSPSL) is proposed in this letter. The severe mismatch between horn aperture and free space leads to narrow impedance bandwidth when the substrate thickness is much smaller than the wavelength (typically less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\lambda _0}$</tex-math></inline-formula> /6). Two groups of periodic offset DSPSL structure are placed in front of the horn aperture, which acts as an impedance transformer to realize smooth transition. Good impedance matching can be easily realized by modifying the constitutive parameters of the offset DSPSL structure. Measured results show that the impedance bandwidth can be improved up to 20.5% from 14 to 17.2 GHz with a low profile less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\lambda _0}$</tex-math></inline-formula> /13. Stable end-fire radiation patterns are obtained across the bandwidth.

Design and fabrication of compact 2 × 2 dual linear polarized wideband and high gain array for Ku-band satellite communication application

In this paper, the design of a planar array antenna for two-way satellite communication is presented. The antenna unit consists of four elements and two waveguide feeding networks used to connect the elements. The radiating elements are small horn apertures. Each element of the array includes two separate ports to radiate vertical and horizontal polarization, respectively. The feeding networks consist of power dividers and bends to connect the vertical and horizontal polarization ports of horns, separately. Radiating elements and feeding networks are designed to cover receive band (10.5–12.75 GHz) and transmit band (13.75–14.5 GHz) within Ku-band. The maximum gain for this type of antenna is 21 dBi.

Loop Excitation of a Conical Horn

A Green’s function technique is developed for the full-wave analysis of a loop excited conical horn, considering all excited modes. The technique avoids the need for discretization of the horn antenna structure into several cascaded sections or the imposition of unknown currents over the entire horn surface, thus reducing the computational burden significantly. The aperture fields of the conical horn are investigated for varying horn lengths. Reflection effects at the aperture is found to be minimal for horn lengths over $5\lambda $ , corresponding to a horn aperture diameter of more than $2\lambda $ . Analytical expressions used to represent the aperture fields over the conical cap at the aperture are provided from which the radiation fields are derived to characterize the aperture radiation. It is observed that the loop excitation can be appropriately located relative to the horn apex to couple to appropriate modes to generate broadside or monopole-like pattern characteristics. Also, in addition to the simplicity of the feed configuration, the loop position can be properly selected to couple to multiple modes that has a significant impact on the pattern directivity and sidelobe levels. The developed technique is also used to rigorously evaluate and characterize the contribution of each mode at resonance.

Design of Planar Leaky Wave Antenna Fed by Substrate Integrated Waveguide Horn

AbstractA metal strip grating leaky wave antenna (MSG-LWA) fed by substrate integrated waveguide (SIW) horn is proposed. The planar horn shares the same substrate with the MSG-LWA, which leads to a compact structure of the proposed antenna. Furthermore, through introducing phase-corrected structure by embedding metallized vias into the SIW horn, a nearly uniform phase distribution at the horn aperture is obtained, which effectively enhances the radiating performance of the MSG-LWA. Results indicate that the proposed antenna scans from –50° to –25° in the frequency band ranging from 15.3 GHz to 17.3 GHz. Besides, effectiveness of the proposed design is validated by comparing with a same MSG-LWA fed by an ideal rectangular waveguide.

Millimeter-Wave Substrate Integrated Dual Level Gap Waveguide Horn Antenna

Substrate integrated H-plane horn antenna design is introduced based on elevated substrate integrated gap waveguide (E-SIGW) configuration. The E-SIGW topology allows designing the horn from two substrates of different thicknesses. A thin substrate for the feed line to eliminate the radiation losses and a thicker one for the radiating aperture. The proposed configuration allows the H-plane horn aperture to be three times thicker than the feed line substrate, which is not possible with the conventional substrate integrated waveguide technology. The transition between the horn layers enhances the matching bandwidth without any aperture modification. The outer surface of the horn around its aperture is loaded with soft surfaces realized by transverse strips. As a result, more symmetric fan beam radiation patterns with suppressed back lobes are achieved.

Optimization of an Offset Receiver Optics for Radio Telescopes

The latest generation of Cassegrain radio astronomy antennas is designed for multiple frequency bands with receivers for individual bands offset from the antenna axis. The offset feed arrangement typically has two focusing elements in the form of ellipsoidal mirrors in the optical path between the feed horn and the antenna focus. This arrangement aligns the beam from the offset feed horn to illuminate the subreflector. The additional focusing elements increase the number of design variables, namely the distances between the horn aperture and the first mirror and that between the two mirrors, and their focal lengths. There are a huge number of possible combinations of these four variables in which the optics system can take on. The design aim is to seek the combination that will give the optimum antenna efficiency, not only at the centre frequency of the particular band but also across its bandwidth. To pick the optimum combination of the variables, it requires working through, by computational mean, a continuum range of variable values at different frequencies which will fit the optics system within the allocated physical space. Physical optics (PO) is a common technique used in optics design. However, due to the repeated iteration of the huge number of computation involved, the use of PO is not feasible. We present a procedure based on using multimode Gaussian optics to pick the optimum design and using PO for final verification of the system performance. The best antenna efficiency is achieved when the beam illuminating the subreflector is truncated with the optimum edge taper. The optimization procedure uses the beam’s edge taper at the subreflector as the iteration target. The band 6 receiver optics design for the Atacama Large Millimetre Array (ALMA) antenna is used to illustrate the optimization procedure.

Wideband Dipole Array Loaded Substrate Integrated H-Plane Horn Antenna for Millimeter Waves

A novel dipole array loaded substrate integrated H-plane sectoral horn antenna with a simple three-layered geometry is proposed. The dipole array integrated into two extra dielectric strips is connected to the top and bottom edges of the horn aperture. Both the horn aperture and the dipole array are effectively radiated together. A wide impedance bandwidth of 44% for $\vert S_{11}\vert dB that can cover the entire Ka-band is verified by a fabricated prototype. Additionally, stable symmetrical radiation pattern with low cross polarizations, low backward radiation, and gain up to 12 dBi with a variation of 3 dB can also be obtained throughout the whole operating band. The proposed antenna provides a new mean to design wideband substrate integrated horns with excellent endfire radiation, which would be attractive for future wideband and multiband millimeter-wave wireless applications, including the fifth generation (5G) mobile communications and the WiGig system.

ALMA Band 1 Optics (35–50 GHz): Tolerance Analysis, Effect of Cryostat Infrared Filters and Cold Beam Measurements

The Atacama Large Millimeter/Sub-millimeter Array (ALMA) is currently the largest (sub-)mm wave telescope in the world and will be used for astronomical observations in all atmospheric windows from 35 to 950 GHz when completed. The ALMA band 1 (35–50 GHz) receiver will be used for the longest wavelength observations with ALMA. Because of the longer wavelength, the size of optics and waveguide components will be larger than for other ALMA bands. In addition, all components will be placed inside the ALMA cryostat in each antenna, which will impose severe mechanical constraints on the size and position of receiver optics components. Due to these constraints, the designs of the corrugated feed horn and lens optics are highly optimized to comply with the stringent ALMA optical requirements. In this paper, we perform several tolerance analyses to check the impact of fabrication errors in such an optimized design. Secondly, we analyze the effects of operating this optics inside the ALMA cryostat, in particular the effects of having the cryostat IR filters placed next to the band 1 feed horn aperture, with the consequent near-field effects. Finally, we report on beam measurements performed on the first three ALMA band 1 receivers inside test cryostats, which satisfy ALMA specifications. In these measurements, we can clearly observe the effects of fabrication tolerances and IR filter effects on prototype receiver performance.

Design of Low-Profile Metamaterial-Loaded Substrate Integrated Waveguide Horn Antenna and Its Array Applications

A metamaterial-loaded substrate integrated wave-guide (SIW) horn antenna and its array application are researched in this communication. The mushroom-type metamaterial is placed in front of SIW horn aperture, and much improvement in impedance matching is achieved on a 1/ $20~\lambda _{0}$ -thickness substrate. Due to the backward wave generated by the metamaterial, backward endfire radiation pattern is observed for the proposed antenna. Experimental results indicate that a fractional impedance bandwidth of 10.6% is obtained for a fabricated prototype. Furthermore, a shunt four-element array and a monopulse four-element array are designed based on the novel SIW horn element to further enhance the radiation performance. Results show that performances of wide operating bandwidth, low profile, and backward endfire radiation pattern are maintained for the designed two arrays.

Coaxial Feed Pyramidal Horn Antenna with High Efficiency

ABSTRACTIn this paper, a short pyramidal horn antenna with coaxial feed has been designed and fabricated with 52% bandwidth, which covers CDMA and GSM 900 bands. The total length of the antenna including coaxial feed is approximately 0.85λ at the lowest usable frequency. The effect of coaxial probe length, probe radius, and its location from the short wall of the waveguide on the resonance frequency, impedance matching, and bandwidth of the horn antenna have been analysed using CST Microwave studio software. Also, parametric analyses have been done by varying the horn length and aperture dimensions to study radiation characteristics of the horn antenna. The horn length has been optimized to obtain maximum efficiency for a fixed aperture. Simulation results show that as the frequency increases from 700 to 1130 MHz, the gain monotonically increases from 8.4 to 12.6 dBi with maximum efficiency of 80% at 850 MHz and it varies between 72% and 80% over this band. The pyramidal horn antenna has been fabricated and measured results are in good agreement with the simulated results.

Substrate Integrated Horn Antenna With Uniform Aperture Distribution

A new substrate integrated horn antenna with hard side walls combined with a couple of soft surfaces is introduced. The horn takes advantage of the air medium for propagation inside, while having a thickness of dielectric on the walls to realize hard conditions. The covering layers of the air-filled horn are equipped with strip-via arrays, which act as soft surfaces around the horn aperture to reduce the back radiations. The uniform amplitude distribution of the aperture resulting from the hard conditions and the phase correction combined with the profiled horn walls provided a narrow beamwidth and -13 dB sidelobe levels in the frequency of the hard condition, which is validated by the simulated and measured results.

Enhancing the Radiation Performance of a Pyramidal Horn Antenna by Loading a Subwavelength Metasurface

We present the detailed design and experimental demonstration of a low-sidelobe horn antenna based on controlling the amplitude and the phase distribution of the electromagnetic fields over the aperture of the horn antenna using a thin single-layer metasurface lens. The lens is composed of two identical subwavelength metallic square-ring arrays printed on the two sides of a single dielectric layer. By placing the metasurface lens inside a standard pyramidal horn, the electromagnetic fields over the horn aperture can be manipulated, resulting in low sidelobe radiation in both $E$ - and $H$ -planes. Both simulated and measured results demonstrate the tapered field distribution over the horn aperture and the significant reduction of sidelobes in the $E$ -plane as well as the reduction of the backlobes.

Substrate Integrated Horn Antenna Loaded With Open Parallel Transitions

The substrate integrated H-plane horn antenna has been struggling with very limited impedance bandwidth since its invention, which is coming from its natural aperture discontinuity. Apart from a variety of series transitions introduced so far, here, parallel transitions are applied to the antenna aperture in addition to narrow slots on the horn walls around the aperture to widen the antenna impedance bandwidth. It is shown that the depth of the transitions can easily determine the center frequency of the matching bandwidth. The new parallel transitions also reduce the antenna back radiation since they act as chokes around the horn aperture.

Substrate Integrated Waveguide Horn Antenna on Thin Substrate With Back-Lobe Suppression and Its Application to Arrays

A substrate integrated waveguide H-plane horn antenna on thin substrate with low back-lobe radiation is presented, and its application to arrays demonstrated. To suppress the back lobe, a pair of slots is employed in the top and bottom metallization. After size and position of the pair of slots are investigated, low back-lobe radiation is achieved. Moreover, the size of the horn aperture is approximately one wavelength, which is suitable for array applications. To highlight this point, the proposed horn antenna is used in a $1\,\times \,4$ planar array on a substrate as thin as one tenth of the wavelength. The array is designed, fabricated, and measured. Measurements show good agreement with simulations and suppressed back-lobe radiation with a 24 dB front-to-back ratio.

Phase Corrected ${H}$ -Plane Horn Antenna in Gap SIW Technology

This communication introduces a modified substrate integrated waveguide (SIW), the gap SIW, and deduces an approximate closed-form expression for calculating its effective width, taking into account the fringing and coupling fields around the gap. As an immediate application, this new structure is used to correct the phase distribution of an H-plane SIW horn antenna. The achieved quasi-uniform distribution results in a greatly enhanced antenna gain without deteriorating the bandwidth. To further improve both radiation and impedance matching, printed tapered-ladder transitions are introduced in front of the horn aperture. Software optimization confirms the possibility of simultaneously achieving an excellent phase correction (and hence increased gain) and a good impedance matching in a probe-excited horn antenna model. Measurements on a homemade prototype validate the design strategy. The final compact Ka-band planar horn antenna achieves an enhanced gain of 10.3 dBi at 34 GHz, with an impedance bandwidth of 20%.

A Low-Profile Wideband Surface-Mountable Substrate-Integrated Waveguide Horn Antenna

A low-profile surface-mountable substrate-integrated waveguide (SIW) horn antenna with wideband performance is proposed in this letter. In order to reduce the serious impedance mismatch at the SIW horn aperture resulting from the thin substrate (0.12 λ0), a semi-open SIW horn is designed by gradually detaching upper broadwall while maintaining another one. Furthermore, in order to realize wide bandwidth for the SIW horn antenna, air-vias are drilled into the semi-open horn to realize smooth transition from semi-open horn to free space. Finally, a fabricated prototype is measured, and results indicate that a 35.7% impedance bandwidth ranging from 19.1 to 27.4 GHz and a 31.8% 3 dB gain bandwidth ranging from 19.3 to 26.6 GHz are obtained, respectively. Stable end fire radiation patterns are observed across the operating band.