Performance Of Reflector Antennas Research Articles

A Quick Calculation Method for Radiation Pattern of Submillimeter Telescope with Deformation and Displacement

Radiation pattern captures the electromagnetic performance of reflector antennas, which is significantly affected by the deformation of the primary reflector due to gravity and the displacement of the secondary reflector. During the design process of large reflector antennas, a substantial amount of time is often dedicated to iteratively adjusting structural parameters and validating electromagnetic performance. To improve the efficiency of the design process, we first propose an approximate calculation method of optical path difference (OPD) for the deformation of the primary reflector under gravity and the displacement of the secondary reflector. Then an OPD fitting function based on the modified Zernike polynomials is proposed to capture the phase difference of radiation over the aperture plane, based on which the radiation pattern will be obtained quickly by the aperture field integration method. Numerical experiments demonstrate the effectiveness of the proposed quick calculation method for analyzing the radiation pattern of a 10.4 m submillimeter telescope antenna at its highest operating frequency of 856 GHz. In comparison with the numerical simulation method based on GRASP (which is an antenna electromagnetic analysis tool combining physical optics (PO) and physical theory of diffraction (PTD)), the quick calculation method reduces the time for radiation pattern analysis from more than one hour to less than two minutes. Furthermore, the quick calculation method exhibits excellent accuracy for the figure of merit (FOM) of the radiation pattern. Therefore, the proposed quick calculation method can obtain the radiation pattern with high speed and accuracy. Compared to the time-consuming numerical simulation method (PO and PTD), it can be employed for quick analysis of the radiation pattern for the lateral displacement of the secondary reflector and the deformation of the primary reflector under gravity in the design process of a reflector antenna.

Development of Deployable Reflector Antenna for the SAR-Satellite: Part 1. Design and Analysis of the Main Reflector Using Honeycomb Sandwich Composite Structure

The deployable reflector antenna based on the synthetic aperture radar is a satellite component that consists of a unit structure in the form of a folded reflector. During the launch process, this satellite antenna is in the stowed condition to improve storage efficiency. It is then deployed to perform the space mission in the on-orbit condition. Due to these structural characteristics of the deployable reflector antenna, the reflector is possible to be loaded in the limited volume of the launch vehicle with the reduced size. Additionally, because the deployable reflector antenna is made by the lightweight material of the carbon fiber reinforced polymer and honeycomb core, it can reduce the launching cost and improve the revisit interval. In this paper, the conceptual design of the main reflector of the deployable reflector antenna was conducted. The main reflector was designed as the honeycomb sandwich composite structure. To design the main reflector, the stacking sequence of the composite material and honeycomb core was investigated to maximize the structural stiffness and minimize the antenna’s mass. Subsequently, finite element analyses including modal, quasi-static, structural–thermal coupling, and transient response were performed to numerically evaluate the structural performance of the lightweight composite reflector antenna.

Design of a Deployable Broadband Mesh Reflector Antenna for a SIGINT Satellite System Considering Surface Shape Deformation.

In this paper, we propose a deployable broadband mesh reflector antenna for use in signals intelligence (SIGINT) satellite systems, considering performance degradation due to shape deformation. To maximize gain by increasing the diameter of the reflector while reducing the weight of the antenna, the reflector of the antenna is designed using lightweight silver-coated Teflon mesh. The mesh reflectors are typically expanded by tension to maintain their parabolic structure; thus, shape deformation cannot be avoided. This shape deformation results in shape differences between the surface of the mesh reflector and the ideal parabolic reflector, thus resulting in the degradation of the performance of the mesh reflector antenna. To observe this degradation, we analyze antenna performance according to the number of arms, the number of joints, the feed distance, and the distance from the reflector center to each joint. The performance of the mesh reflector antenna is examined using an effective lossy conducting surface (ELCS) that has the same reflectivity as the silver-coated Teflon mesh to reduce simulation time and computing resources. The designed silver-coated Teflon mesh reflector and the double-ridged feed antenna are fabricated, and the bore-sight gain is measured using the three-antenna method. The measured bore-sight gain of the proposed antenna is 31.6 dBi at 10 GHz, and the measured and simulated results show an average difference of 3.28 dB from 2 GHz to 18 GHz. The proposed deployable mesh reflector antenna can be used in a variety of applications where small stowed volume is required for mobility, such as mobile high-gain antennas as well as satellite antenna systems. Through this study, we demonstrate that shape deformation of the mesh reflector surface significantly affects the performance of reflector antennas.

Accurate Data Match and Call Method for the Thermal Compensation Database of the Reflector Antenna

Abstract The influence of thermal deformation on the performance of reflector antennas has become increasingly significant with the increasing aperture and working frequency. The use of a thermal compensation database is an efficient method to compensate for the deformation caused by the non-uniform temperature distribution. However, how to efficiently and accurately match and call the database remains as one of the tough challenges for the antenna thermal compensation system to achieve real time compensation. Therefore, this study proposes a data match and call method for the thermal compensation database of the reflector antenna, matching the database from three aspects: the overall rms match of temperature data, the similarity area match of each data sample, and the key area match of key structural positions. The validation of this method is demonstrated in an example. The difference between the pointing adjustment amount calculated by the matched data and the collected data was found to be less than 1″, which satisfied the requirements of practical engineering, thus achieving real-time thermal compensation of the antenna.

Far‐Field Pattern Tolerance Analysis of Reflector Antenna with Random or System Error Based on Interval Arithmetic

A novel analytic approach for the research of effect on electromagnetic performance of reflector antennas with deformation, including random processing error and system error caused by external loads(such as wind,gravity, and solar radiation), in panels of the reflector surface is proposed. The deformations are modeled as error intervals, and their impact on the electromagnetic performance, including radiation power pattern and some main electromagnetic characteristics(such as side lobe level,peak power, and half-power beamwidth), are efficiently estimated by Interval analysis(IA). The closed-form equations indicate the relationship between the error interval and the bounds(upper and lower bounds) of the radiated power pattern interval by exploiting the rules of interval arithmetic. Two kinds of surface errors(random and system error) and two shapes of deformation area(bump-like and sector) are taken into account in the numerical examples to assess the validation and effectiveness of the proposed approach. The results of the examples show that the proposed IA-based approach has great capability and effectiveness regarding the traditional statistical method(such as Monte-Carlo method).

Compensation of vibration-induced pointing error caused by wind disturbances in large antenna

Under different working conditions, scientists need to ensure that the pointing performance of large reflector antenna; however, wind disturbances are the most tricky problems that minimize the pointing accuracy. This is because the wind disturbances have randomness and time-varying characteristics. Davenport spectrum has been widely used to estimate the frequency domain of wind; moreover, it is also used to design the antenna controller in such a way that the servo angle error caused by wind torque gets minimized significantly. But it is difficult to ensure pointing accuracy without considering the reflector vibration caused by wind force. Therefore, this paper proposes a novel method to overcome wind disturbances. This method introduces the concept of predictable pointing errors in the servo controller. All these predictable errors are induced by vibrations. First, we developed an analysis model to determine pointing errors caused by wind. Second, we develop the wind forecast technique to estimate the future load on antenna structure. Third, using the model predictive control (MPC), we design a novel controller to compensate the future pointing errors. Finally, we conduct a series of tests and analysis. For a 7.3 m antenna, the results indicate that when MPC controller is used in the system, the resultant pointing errors are seven times smaller than the errors witnessed under the traditional controller. This indicates that MPC controller is effective in improving the pointing performance.

Optimization of reflector antennas in radio telescopes

We present an analysis on the performance of Cassegrain reflector antennas. In our study, we have adopted the design parameters for the Cassegrain configuration used in the Atacama Large Millimeter Array (ALMA) project. We have adjusted the focal-length-to-diameter ratio f/D of the primary reflector to investigate the optimum performance of the antenna. In our study, signal frequency at the high edge of ALMA band 1, i.e. 45 GHz has been selected. The results obtained from the physical optics simulation show that the aperture efficiency of the antenna is at its optimum (i.e. 80.36%) when f/D ranges from 0.5 to 0.6. The radiation characteristics at this range of ratio are found to be similar. The radius of the secondary reflector and edge taper Te which correspond to the optimum aperture efficiencies ranges from 371 mm to 372 mm and 10.64 dB to 10.75 dB, respectively.

Improvement in side-lobe performance of prime focal reflector antenna

This paper presents a simple and elegant solution to improve the degradation of side lobe level (SLL) caused by strut and feed system blockage in prime focal reflector antenna system. This is accomplished by numerical optimization of reflecting wedges, which may be integrated with conventional rectangular cross-sectional struts. Design, optimization and analysis of metallic sheet feed cover have been carried out to reduce diffraction caused by the feed system. Quadrilateral meshing is used to analyze non-standard scatterers. Comprehensive analysis results showing frequency response of SLL of antenna system have been discussed, for different antenna component assemblies. A novel method has been implemented to understand the effect of wedged struts and feed cover for SLL improvement. Experimental data have also been presented to validate the simulated antenna parameters. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1304–1311, 2016

A Practical Approach to Evaluate the Effects of Machining Errors on the Electrical Performance of Reflector Antennas Based on Paneled Forms

A novel and practical approach to determine the effects of machining errors on the electrical performance of large reflector antennas is presented. The proposed approach is based on the practical paneled forms of reflector surface and a sum of ideal radiation power in the absence of errors and error power contributed by the manufacturing inaccuracies. The error field of each panel is expressed using first Taylor expansion, and then the Gaussian correlation function of phase errors is employed to perform the quadruple numerical integration of average power radiated from a single panel. Detailed parametric simulations are performed based on a 35-m reflector antenna, and the results clearly demonstrate how the average power is changed with machining errors and error correlation interval.

Aperture Efficiency Predictions in Symmetrical Paraboloidal Reflector Antennas With Nonplanar Log-Periodic-Type Feeds

Nonplanar log-periodic-type antennas are attractive as wideband reflector feeds since they can be arranged to provide an axially symmetric radiation pattern that is stable over a wide bandwidth with near constant input impedance. However, these antennas have a frequency-dependent phase center that causes de focusing and degrades reflector antenna performance when used in wideband systems. This letter presents a technique, which includes radiation pattern as well as defocusing effects, to predict an upper bound for reflector system performance when a nonplanar log-periodic feed is used, resulting in useful design guidelines. Predicted results compare favorably with physical optics simulations.

Calibration of Cylindrical Reflector Antennas With Linear Phased Array Feeds

The phase of the elements of a phased array feed is optimized to yield a maximum directivity for front fed and offset cylindrical parabolic reflector antennas. Calibration improves the reflector antenna performance, especially for front fed reflectors with larger feeds.

Characterization of effects of periodic and aperiodic surface distortions on membrane reflector antennas

The focus of this paper is to characterize the effects of periodic and aperiodic surface distortions on the performance of membrane reflector antennas. Since the surface of this class of reflector antennas is very thin, it is susceptible to various types of periodic and aperiodic distortions. The particular antenna dimensions used for this study are similar to the specifications for the JPL/UCLA half scale model of second generation precipitation radar (PR-2) mission reflector. Analytical expressions are introduced to model periodic and aperiodic surfaces and based on these models the effects of distortions on the radiation performance of the antenna are simulated. Aperiodic distortions are more realistic cases of distortions due to the fact that the period of the distortions is not constant through out the reflector surface. For each case, far-field patterns of the reflector are simulated and it is shown that closed-form expressions can then be derived which result in a very efficient computational method to predict some of the unique features of these patterns including location and level of observed grating lobes. Furthermore, based on spatial Fourier analysis of the surface distortion, it is shown that deviation from periodicity in the distortions of reflector surface results in lowering these grating lobes. Parametric studies have been performed to provide design guidelines for acceptable surface behavior for large deployable membrane reflector antennas for future space borne missions.

Noise temperature and gain loss due to paints and primers: a case study of DSN antennas

In achieving high performance for reflector antennas, it has been noted that it is essential to carefully assess the roles of surface paints and primers. A thorough literature search has revealed that not much has been reported on this very important engineering-implementation topic. It is one of the main objectives of this feature article to provide a detailed study on the effects of paints and primers on reflector-antenna performance. In particular, as a case study, this paper presents excess-noise-temperature and added-gain loss data at 32 GHz for various combinations of paints and primers currently being studied for use on DSN (Deep Space Network) antenna reflector surfaces. It is shown that 500FHR6 acrylic urethane-based paint has the lowest excess-noise-temperature contribution. Previously, it has been recommended that this paint be used for all new DSN beam-waveguide antennas being constructed, and for all those 34-m and 70-m antennas with reflector surfaces that need repainting. The results, methodologies, and observations presented in this article are also applicable to other reflector-antenna configurations.

SABOR: a fast analysis tool for horn and reflector antennas

SABOR (software de analisis de bocinas y reflectores) is an antenna-analysis approach for the computation of horn- and reflector-antenna performance. The program covers and expands topics already developed with other software. The program can analyze almost any kind of horn (E and H pyramidal horns, circular horns, corrugated horns). The current configuration of SABOR can also analyze centered and offset parabolic reflectors, dual-offset Cassegrain and Gregorian reflectors, and centered Cassegrain systems. For feeding reflectors, the program allows use of the classical cos/sup q/ pattern and any of the horn mentioned above. Usage of real horns improves the accuracy of computed efficiencies and the simulation of the cross-polar radiation.

Beam efficiency of reflector antennas: the simple formula

Beam efficiency has proven to be an important measure for characterizing the performance of reflector antennas. In this paper, a simple formula is presented to allow for a quick estimate of the beam efficiency of reflector antennas. This estimate includes the effects of edge tapers, feed spillover, random surface errors, and central blockage. The application of this formula is detailed in a case study, and its accuracy is demonstrated in comparison with a numerical simulation using diffraction analysis.

Solar panel scattering effects on reflector antenna performance

The effects of solar panel scattering on a Ku-Band reflector antenna performance are analysed. It is shown from computation and experiment that solar panel scattering interference causes mainlobe gain decrease and sidelobe gain increase on the sum patterns, as well as null position shift and null depth decrease on the difference patterns.

Effect of dielectric coatings on parabolic reflector antenna performance

AbstractThe effect of a dielectric coating on the gain, co‐polar radiation pattern, and cross‐polarization level of a linearly polarized parabolic reflector antenna is investigated for both dry and wet surface conditions using a physical optics analysis of the equivalent surface currents. By choosing the correct thickness, the effect of a dielectric coating can be minimized, and, at the same time, an equivalent metal‐reflector representation shows that the antenna gain is less sensitive to the coating surface accuracy.

Analysis of active surface reflector antenna for a large millimeter wave radio telescope

The authors analyze the effects of imperfect segment alignment on the aperture efficiency of a large millimeter telescope. A 50 meter diameter instrument of this type specified to operate to wavelengths as short as 1 mm is being designed with an actively controlled main surface. By simulating the performance of the control system, they generate samples of tilt and piston errors for the segments from which the antenna radiation patterns and aperture efficiencies are calculated. They make a comparison of these results with models of antenna tolerance theory developed by Ruze (1966), which relate the aperture efficiency to the RMS phase error. They find that Ruze's formulas have a different range of validity when the aperture RMS phase error, rather than the RMS surface error, is used as a parameter. When appreciable tilt errors are present in large segmented antennas, the aperture RMS phase error tends to a constant value, independent of the aperture illumination and of the shape of the segments. They conclude that the antenna RMS surface error is a better tracer of the aperture efficiency than is the aperture RMS phase error when Ruze's formula is used. They find that this well-known expression stands as a lower limit to the performance of large segmented reflector antennas. >

Design and performance of a reconfigurable mesh reflector antenna. Part 1: Antenna design

The theory and design of a reconfigurable mesh reflector antenna is described with particular reference to satellite applications. As an example, it is shown that antenna pattern reconfiguration can be achieved for a 50-wavelengthdiameter antenna using 78 actuators with performance very comparable with that prescribed for an antenna fed from an array. The predicted performance relies on an accurate mechanical model for the knitted mesh surface, which is developed here using a network of elastic springs. The effectiveness of the model is demonstrated. Other factors affecting performance, such as boundary constraints and the means to control the mesh surface, are discussed together with tolerances on actuator settings.

Effect of an arcjet plume on satellite reflector performance

The effect of an arcjet plume on the performance of satellite reflector antennas is studied. The arcjet plume is modeled as a weakly ionized plasma. The spatial permittivity distribution of the plume is approximated using the measured electron density profile and a cold plasma model. Geometrical optics is applied to determine the ray paths as well as the transmitted fields through the inhomogeneous plume. The ray optics results are compared against several exact solutions for scattering from inhomogeneous dielectrics, and good agreement is observed for sufficiently large scatterer size. The far-field antenna patterns of the reflector in the presence of the plume are calculated from the transmitted ray fields using a ray-tube integration scheme. For arcjet prototypes in the 1-kW class, the plume effect on the antenna performance is small. As the electron density increases, the main beam and sidelobe level gradually degrade. The main beam also tends to squint away from the plume region. >