Dual Reflector Antenna Research Articles

Amplitude and Phase Synthesis at Cylindrical Apertures of Omnidirectional Dual-Reflector Antennas for Uniform Coverage

Amplitude and Phase Synthesis at Cylindrical Apertures of Omnidirectional Dual-Reflector Antennas for Uniform Coverage

The Active Compensation Technique for Large Reflector Antennas Based on Quadratic Curve Fitting

Active reflectors are often used to compensate the surface distortion caused by environmental factors that degrade the electromagnetic performance of large high-frequency reflector antennas. This is crucial for maintaining high gain operation in antennas. A distortion compensation method for the active reflector of a large dual-reflector antenna is proposed. A relationship is established between the surface deformation and the optical path difference for the primary reflector by geometric optics. Subsequently, employing finite element analysis, a polynomial fitting approach is used to describe the impact of adjusting points on the reflector surface based on the coordinates of each node. By standardizing the positions of various panels on the reflector, the fitting ns can be applied to the reflector panels of similar shapes. Then, based on the distribution characteristics of the primary reflector panels, the adjustment equation for the actuators is derived by the influence matrix method. It can be used to determine the adjustment amount of actuators to reduce the rms of the optical path difference. And, the least squares method is employed to resolve the matrix equation. The example of a 110 m aperture dual-reflector antenna is carried out by finite element analysis and the proposed method. The results show that the optical path difference is reduced significantly at various elevation cases, which indicates that the proposed method is effective.

A review: Performance of multibeam dual parabolic cylindrical reflector antennas in LEO satellites

The characteristics of multibeam dual parabolic cylindrical reflector antennas are summarized in this article. They can generate an arbitrary number of beams with arbitrary tilt angles for each beam. They can be remotely controlled to cover any arbitrary area, of any shape and size, even if the antenna was mounted on a quasi-stationary platform. Their performance in Low-Earth Orbit (LEO) satellites and ground stations (terminals) have been presented. A simple beam tracking technique was developed. For any specific satellite orbit, the orientation of the ground-station antenna could be adjusted such that its beams are parallel to the satellite's beams and directed toward them. The ground-station antenna can simultaneously communicate with multiple satellites in different orbits. A single antenna can cover the whole mm-band (17.8-30 GHz), which is one of the most widely used bands in LEO satellites. The overall size of a mm-wave antenna, generating 20-24 dB gain, is 14.8x10.4x3.7 cm3 and its weight is 0.37 kg.

A Pattern Reconfigurable Antenna for Ka-band Application

In this paper, we present an easy and systematic design approach to realize a dual beam reflector antenna at Ka-band which produces a narrow beam and a wide beam in the boresight. These two beams can be independently selected mechanically or by means of an electronic switching circuit. An exclusive systematic design approach has been presented. Simple mathematical expressions have been used for the design of the reflector and feed horns. The complete antenna has been realized with aluminum and its performances were experimentally validated. It yields ≈11.44% impedance bandwidth. It produces ≈ 35.4 dBi gain in the narrow beam mode with a half power beamwidth of ≈ 4.4° × 3.7° and about ≈ 11.3 dBi gain in the wide beam mode with a 3 dB beamwidth of ≈ 46.5° × 46° at 28 GHz. In this present work, the patterns are swapped between a narrow-beam and a wide-beam in the broadside. The ratio of the wide-beamwidth to the narrow-beamwidth is about 11:1, which is substantially different from all earlier investigations.

Low-Cost 3-D Millimeter-Wave Concealed Weapons Detection Using Single Transceiver Affine Synthetic Arrays

The problem of detecting concealed weapons with a low-cost 3-D imaging radar system is addressed. The concept of affine phase center translations to generate a synthetic array is proposed as an alternative to conventional synthetic aperture and multistatic imaging radars. This enables the generation of a synthetic 2-D array with a dynamic dual reflector antenna system and a single transceiver. The dual reflector antenna is composed of a 3-D printed ellipsoidal sub-reflector and a conic main reflector. The phase front of the horn feed is shown to be translated to different locations by controlling the relative positions of the two reflectors. The reflectors are fabricated using a simple protocol that keeps the cost very low but introduces significant phase aberrations. These phase aberrations are corrected by developing a novel geometrical optics based optimized calibration routine. The imaging system is tested using a 76.5–84.5 GHz stepped frequency transceiver in different concealed weapons detection scenarios. As a demonstration, a metallic handgun and a nonmetallic pipe-bomb are concealed on a mannequin which serves as a human surrogate with similar skin reflectivity. At a target distance of 2.8 m the achieved depth resolution and lateral resolution are 2 and 1.5 cm, respectively. The 3-D images constructed using back-projection are of high enough quality to successfully identify the weapons while maintaining the privacy of the individual.

Electrical Performance Compensation of Reflector Antenna Based on Sub-Reflector Array

Large high-frequency reflector antennas typically operate outdoors and are impacted by environmental factors such as wind, rain, snow, solar radiation, etc. These conditions cause the antenna structures to distort, which, in turn, affects electrical performance. The observation performance of the antenna is seriously affected. To solve this problem, based on the active control of sub-reflector arrays, an optimization method for sub-reflector arrays and an active compensation method for electrical performance are proposed. Through real-time regulation of the phase plane of the distorted aperture field, the electrical performance of the antenna can be compensated for. The research object, a 65 m Cassegrain dual-reflector antenna, is designed in this work using a sub-reflector with an aperture of 6.1 m. The form and posture of the sub-reflector are comprehensively changed by adjusting the position of the sub-reflector panel and the overall movement of the sub-reflector, and the phase inaccuracy of the aperture field brought by the deformation of the main reflector is compensated for. The simulation results demonstrate that the maximum gain loss can be reduced from 0.44315 dB to 0.0803 dB and the maximum point error can be reduced from 0.00143° to 0.00047° under wind load with an average wind speed of 12 m/s using the active sub-reflector array adjustment strategy proposed.

Quadband Petal Reflector Antenna for Ground Communications: Combining four frequency bands into one innovative and reliable design

Future protected communications require soldiers on the ground to carry several antennas integrated with their manpacks to provide secure and reliable communications at a number of frequency bands. This article describes a novel quadband petal reflector antenna (QPRA) that combines four frequency bands into one using a quadruplexer. A dual-reflector antenna utilizing an axially displaced ellipsoid subreflector being fed with a quad-ridged horn provides communications at Ku-band transmit (Ku-Tx), Ku-band receive (Ku-Rx), K-band receive (K-Rx), and Ka-band transmit (Ka-Tx) frequencies simultaneously. The main reflector is made of six identical petals that can be quickly assembled and disassembled in the battlefield. The antenna is mounted on a lightweight gimbal to provide beam scanning over a hemispherical coverage. The antenna is mounted on a tripod structure for field operations and uses commercial off the shelf (COTS) components and 3D manufactured parts to minimize cost and mass. The novelty of the antenna presented in this article includes a wide bandwidth capability of 73%, the use of a petal reflector, a 3D manufactured quad-ridged horn, a high-performance quadruplexer, and the use of COTS gimbals for beam scanning. Antenna design, analyses, hardware, and test results are presented in this article. The measured results of the antenna agree well with the computed results validating the QPRA design.

Active Adjustment of the Subreflector Shape for the Large Dual-Reflector Antenna.

A shape adjustment method for subreflectors based on minimizing the residual wavefront error of the large dual-reflector antenna is presented. This method is used to compensate for the antenna structural deformation caused by environment loading. The shape of the subreflector is adjusted using actuators fixed under the panels. The shape adjustment response function for the subreflector shape and the actuators' adjustment amount is established, which is based on the inverse distance weighting function, and then the control function of the subreflector shape is obtained. The actuators' adjustment amount can be calculated using the least squares matrix transformation with the minimum residual wavefront error. Analysis of the experiment's results shows the residual wavefront error and primary aberration are greatly reduced under different elevation angles, and the effectiveness of the proposed method is verified.

Additive manufacturing in compact high-gain wideband antennas operating in mm-wave frequencies

A wideband dual-reflector 3D-printed antenna is proposed to operate in the mm-Wave band. The design is based on a Cassegrain reflector optics but including a dielectric piece for merging the feeding system and the support structure of the subreflector. The operational principle of this antenna is presented, as well as the design parameters. Then, a prototype to operate at Ka-band is manufactured combining a 3D-printed technique using PLA as printable material and a spray to coating the antenna, providing a low-cost affordable solution. The different pieces of the antenna are evaluated, and the antenna is also measured in a spherical compact range. An excellent agreement between simulations and measurements is obtained, resulting in a 48.2% of operational bandwidth. These results validate the use of coating procedures and the design technique at these demanding frequencies. Its operation shows a stable gain in the entire Ka-band (including 28 and 39 mathrm{GHz}), which makes the antenna as a suitable light, low-cost, and broadband solution for mm-Wave applications.

Planar metasurface sub-reflector based dual-reflector antenna for multi-directional beaming

This paper presents a novel planar metasurface subreflector (MSSR) array-based dual-reflector antenna inspired by Cassegrain arrangement for simultaneous beaming in far-field microwave wireless power transfer at f0=2.45 GHz for the first time. The MSSR unit cell exhibits 94.8% reflection and 0.0065λ0 thin geometry where λ0=122.45mm is the operating wavelength. The antenna exhibits optimum gain at focus F=0.93λ0, and with variation in F, required beamwidth and sidelobe levels can be easily achieved. The experimental studies show 15.8 dBi gain and 13.4°, 25.2° half power beamwidths in E- and H-plane, respectively in the main direction. When the MSSR array is placed at F, the measured electric field shows a nearly equal concentration in three directions. This is to be used to power small IoT devices at different angles simultaneously. This work may serve as a design guide for designing the planar MSSR-based dual-reflector antenna in the microwave domain.

Influence and Correction of Wavefront Primary Aberrations for Radio Telescopes using Aberration Theory

Dual-reflector antennas are widely used in astronomical observations and satellite communication. Structural deformations of the reflectors for radio telescopes are inevitable in outside working conditions due to exterior environment loads, which will cause distortion in the surface of the primary reflector and displacement of the subreflector, then lead to gain degradation and misalignment. In this paper, the influence and correction of misalignment in a dual-reflector antenna have been studied. From the perspective of wavefront aberration, a method is proposed to correct the wavefront primary aberration by adjusting the subreflector position. The characteristics of wavefront errors caused by structural deformation of the reflector have been analyzed, and relationships between the position motions of the subreflector and the Seidel wavefront aberrations are derived. The adjustment quantities of the subreflector are also derived. The results show the appropriate positional change of the subreflector in the lateral and axial directions can effectively correct the effects of the tilt and defocus in the primary aberrations caused by antenna structural deformations.

A Dynamic Dual Reflector Antenna for 4-D Synthetic Aperture Radar Imaging Achieving a 0.4° Pencil Beam at 77 GHz

All existing state-of-the-art high-resolution millimeter-wave imaging systems experience a tradeoff between image acquisition time and transceiver array complexity. The proposed dual-reflector antenna breaks this tradeoff by drastically reducing the array formation time while maintaining the relative simplicity that comes with using a single transceiver element. It consists of a dual-mode horn feed, a rotating ellipsoidal subreflector, and a conic main reflector. The rotating subreflector creates a virtual phase center that rotates about an axis to produce a synthetic circular array with a diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$120\lambda $ </tex-math></inline-formula> . The main reflector redirects the beams from each of these virtual phase centers to overlap and illuminate the scene over a wide field of view (FOV). Two cases are simulated, one with a 14° FOV and another with 25° FOV in both azimuth and elevation. The former case is experimentally verified and achieves a measured half-power beamwidth of 0.4° over the entire scan range. The proposed system can reduce the image acquisition time to the order of milliseconds/seconds, which makes real-time SAR imaging a practical alternative to multiple-input–multiple-output (MIMO) and phased arrays at millimeter-wave and sub-millimeter-wave frequencies.

Adjustment Method of Coupled Dual-Surface Accuracy for Antennas Using Interval Model Updating

Affected by the uncertainties caused by cable cutting and assembly errors, material performance dispersion, and truss deformation, the dual-surface accuracy of a mesh antenna cannot satisfy the design requirements. However, the existing methods can only adjust the accuracy of a single surface. This paper studies a method for adjusting coupled dual-surface mesh antennas considering uncertainties. Dual-reflector mesh antennas use both the front and rear reflectors for sensing, and both surfaces have shape accuracy requirements. First, an interval model updating method based on sensitivity analysis is proposed to obtain an updated interval parameters model group, which can accurately represent the relationship between adjustment cable length and surface accuracy. Then, an interval optimization function for the coupled dual-surface accuracy is established to get optimal adjustment amounts, which is solved by using the fast elitist nondominated sorting genetic algorithm (NSGA-II). Meanwhile, a kriging model is introduced to improve the optimization efficiency. Finally, the AstroMesh antenna is taken as an example to verify the validity of the proposed method. The results show that both the front and back net accuracies can be improved after adjustment, proving the proposed method’s feasibility.

위성 SAR용 이중 반사판 검증을 위한 위상 배열 급전기 설계 및 제작

In this study, when developing a phased array feeder for the verification of dual reflector antennas for satellite synthetic aperture radar (SAR) applications, the main component test and performance verification of the feeder were considered. The performance was verified at the level of the component radiator, radiofrequency/control board, and integrated phased array feeder with specifications, including the bandwidth, polarization, directivity, beam width, and side lobe, required for the feeder. Accordingly, it was confirmed that the bandwidth was 19.18 % (H) and 16.07 % (V), directivity was 38.42 dBi (H), 38.32 dBi (V), HPBW Az/El 2.064° (H)/2.187° (H), 2.083° (V)/2.202° (V), and the side lobe was under −12.84 dB (H), −13.05 dB (V). Therefore, we verified that it can be adopted as a phased array feeder for the verification of dual reflector antennas for satellite SAR applications.

Low-Cost Ka-Band Satellite Receiver Data Preprocessing for Tropospheric Propagation Studies.

Satellite tropospheric propagation studies strongly rely on beacon receiver measurements. We were interested in performing a measurement campaign to characterize rain attenuation statistics. In this article, we outline some of the characteristics and drawbacks one faces when trying to perform a radio wave satellite beacon propagation experiment at the Ka-band with low-cost measurement equipment. We used an affordable beacon receiver consisting of a commercial low-noise block down-converter, an outdoor dual-reflector antenna, and a software-defined radio unit. To measure rain attenuation events, we needed to work out where the reference signal level was at all times. However, as we did not have a radiometer to remove the impact of gases and clouds, since it is a very expensive device, we used a procedure that involved the subtraction of a stable and reliable reference level (template) from the raw received beacon level. This template was extracted from observations during non-rainy periods. The procedure implemented for extracting the template was based on the same data processing methodology used by other authors in this field. Here, we describe through specific examples the main characteristics of the templates extracted on non-rainy days, as well as the impact of some meteorological parameters and unavoidable, but small antenna pointing errors.

A Compact Gap-Waveguide Dual-Polarized Ka-Band Feed for 50dBi Reflector Antennas With Tracking Function

A dual-polarized Ka-band feed based on gap waveguide (GW) technology for an ultra-high-gain reflector antenna is presented. The feed provides SUM-beams for data transfer and DIFF-beams for tracking. The whole reflector antenna is composed of the feed and a dual-reflector Cassegraine antenna. The feed has been prototyped, and the measured reflection coefficients for the horizontally and the vertically polarized SUM-beam ports are below -10 dB and -8 dB over 30.8-38 GHz, respectively. The measured feed radiation patterns agree well with the simulated ones. The dual-reflector Cassegraine antenna has been designed and simulated by using GRASP with the simulated far-field function of the proposed feed, showing that the reflector antenna achieves SUM-beam gains above 50 dBi and the null depth of the DIFF-beams are more than 30 dB below the maximum of SUM-beams.

Analysis and compensation of the reflector antenna pointing error under wind disturbance

A large reflector antenna has been widely used in satellite communications, gravitational wave detection, galaxy origin observation and other fields due to its narrow beam and high gain. With the increase of the antenna aperture and the improvement of the working frequency, the requirements for the pointing accuracy of an antenna are also rising. However, the effect of environmental load on the deformation of the antenna structure, which in turn affects its beam pointing, has become a key problem to be solved urgently in the antenna engineering applications. The key issue to solving this problem involves accurately estimating the pointing error caused by the structural deformation and designing an effective controller that is based on the structural deformation. In this paper, we first establish a dynamic model for antenna structure based on the modal superposition method. The model is then modified by using modal characteristics and the dynamic displacement information of the sampling points to achieve the purpose of accurately estimating the structural deformation. Secondly, by considering the influence of the deformation of the rotating shaft and the reflector surface on the pointing accuracy, a control-oriented pointing error analysis model is established for estimating the pointing error caused by the environmental load in real time. Thirdly, based on considering the influence of the shaft deformation on the error compensation, the feedback error amount is decoupled and corrected to improve the accuracy of the compensation error. Finally, this paper analyzes and verifies the 65 m S/X-band dual reflector antenna with a numerical example. We consider a fluctuating wind with an average wind speed of 10 m s−1 as an example, which results in a maximum pointing error of 55.82″ as calculated by the antenna theoretical model, whereas the maximum pointing error as predicted by our model is 68.27″. The pointing error after compensating for the cause of the environmental load with the modified controller is reduced to 10.57″, which effectively improves the antenna pointing performance.

Miniature Convoluted FSS for Gain Enhancement of a Multiband Antenna

Convoluted elements on a frequency selective surface (FSS) allow for low frequency elements to be contained in physically smaller unit cells. Smaller unit cells give the FSS greater angular stability, especially where a curved FSS is required, and so unwanted grating effects are avoided. A convoluted element FSS with a frequency rejection band centred at 2 GHz and unit cell area of 15 mm by 15 mm ( $0.10\,\,\lambda \times 0.10\,\,\lambda$ ) has been developed. To test its usefulness, the full structure FSS is used as a parabolic reflector in a dual band FSS reflector antenna operating at 1 GHz and 2 GHz. Simulated and measured results are close at both bands. The reflector antenna has high gain at 2 GHz of 12.7 dBi (simulated) and 11.7 dBi (measured). To observe the angular stability of the FSS and therefore its effectiveness as a reflector, it was compared with a copper test reflector at both bands. Simulation of the reflector antenna with test reflector produced a 2 GHz gain of 13.3 dBi which is very close to that with the FSS reflector. The simulated 2 GHz gain plot of the reflector antenna with FSS reflector is very similar to that with the test reflector indicating that the FSS has good angular stability. The gain at 1 GHz is also high with 9.3 dBi (simulated) and 8.7 dBi (measured). Simulation of the reflector antenna with no FSS and only a rear test reflector produced a 1 GHz gain of 10 dBi which is very close to that with the FSS reflector in place indicating that the FSS causes no significant attenuation at that frequency. The convoluted element FSS would be useful as a curved reflector in the creation of high gain, multiband, conformal antennas.

New technique for shaping axisymmetric dual‐reflector antennas using conic sections to control aperture illumination

This work presents a new technique for the geometrical optics (GO) shaping of axisymmetric dual-reflector antennas. Both reflectors' generatrices are shaped by the continuous concatenation of conic sections, suited to provide simultaneous control of amplitude and phase of the aperture's GO field. With amplitude and phase control of the aperture field, the antenna designer has more options to achieve prescribed circularly symmetric radiation patterns. The GO formulation is derived for the well-known shaped Cassegrain configuration, but it can be easily adapted to other axisymmetric geometries. Illustrative GO designs are investigated and results validated by a full-wave analysis provided by the method of moments.

Calculation of the Best Fit Subreflector and Its Application in Eliminating the Harmless Error of Deformed Large Subreflectors

For a dual reflector antenna whose subreflector is also equivalent to a large reflector antenna, its structure will inevitably be deformed due to the effect of gravity, wind, temperature, and so on. This article is inspired by the homologous idea applied to main reflectors and extends this idea to subreflectors to eliminate the harmless error of the distorted subsurface by using the best fit surface of the same type. This article proposes seven parameters to determine the best fit subreflector (BFS): five rigid parameters (three translation and two rotation parameters) and two parameters related to the change of the subreflector shape. These seven homology parameters are calculated by the least square method (LSM). The subreflector of the QiTai radio telescope (QTT) is used in two examples. The first example shows that the proposed method can effectively calculate the BFS surface and obtain the accuracy that has eliminated the harmless error of the distorted subreflector. In the second example, the accuracy without harmless error is used in the classical design so that the homologous design of the subreflector structure is realized. The excellent results show the validity of the proposed method and provide an important reference for the structure design of large subreflectors.