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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1992

Progress in integrated-circuit horn antennas for receiver applications. Part 1: Antenna design

The purpose of this work is to present a systematic method for the design of multimode quasi-integrated horn antennas. The design methodology is based on the Gaussian beam approach and the structures are optimized for achieving maximum fundamental Gaussian coupling efficiency. For this purpose, a hybrid technique is employed in which the integrated part of the antennas is treated using full-wave analysis, whereas the machined part is treated using an approximate method. This results in a simple and efficient design process. The developed design procedure has been applied for the design of a 20, a 23, and a 25 dB quasi-integrated horn antennas, all with a Gaussian coupling efficiency exceeding 97 percent. The designed antennas have been tested and characterized using both full-wave analysis and 90 GHz/370 GHz measurements.

Eleftheriades, George V.↗
NASA NTRS1993

The 24 GHz measurements of 2.2 lambda conical horn antennas illuminating a conducting sheet

Monostatic reflection-coefficient magnitude, absolute value of Gamma, measurements occurring between a radiating horn and a metal reflecting plate are presented for a family of three 2.2 lambda diameter conical horn antennas. The three horns have different aperture phase deviations: 6 deg, 22.5 deg, and 125 deg. Measurements of the magnitude of absolute value of Gamma as a function of horn-plate separation (d) extend from an effective antenna aperture short (d = O) to beyond the far-field boundary (d = 2D(sup 2)/lambda, where D is the antenna diameter). Measurement data are presented with various physical environments for each of the horns. Measured scalar data are compared with theoretical data from two models, a numerical model for a circular waveguide aperture in a ground plane and a scalar diffraction theory model. This work was conducted in support of the development effort for a spaceborne multifrequency microwave reflectometer designed to accurately determine the distance from a space vehicle's surface to a reflecting plasma boundary. The metal reflecting plate was used to simulate the RF reflectivity of a critically dense plasma. The resulting configuration, a ground plane mounted aperture facing a reflecting plane in close proximity, produces a strong interaction between the ground plane and the reflecting plate, especially at integral half-wavelength separations. The transition coefficient is characterized by large amplitude variations.

Cross, A. E.↗
NASA NTRS1991

Millimeter-wave integrated-horn antennas. I - Theory. II - Experiment

Full-wave analysis is employed to determine the far-field pattern and input impedance of a dipole-fed horn antenna in a ground plane, and the theoretical results are compared with mm-wave and microwave data. The theoretical work exploits the Green's function corresponding to the horn structure and the method of moments. It is determined that the horn should have 70 sections/wavelength and 50 secondary modes for optimized accuracy, and certain dipole positions can reduce the resonance to zero. The experimentally derived impedance and radiation patterns agree with the constraints developed theoretically. The 70-degree flare-angle horn with selected dipole positions and horn apertures yields good radiation patterns, cross-polarization levels, and resonant dipole impedances. The conclusions are of interest to the development of the horn antennas etched in Si/GaAs for applications to zero-visibility tracking, radio astronomy, plasma diagnostics, and remote sensing.

Eleftheriades, George V.↗
NASA NTRS1985

Theoretical Investigation Of Dielectric Horn Antennas

Mathematical model applicable to both solid and hollow dielectric horn antennas implemented in computer program. Conventional hollow metal horns have several disadvantages: difficult to fabricate at short wavelenghts and conducting properties of metal tend to deteriorate with increasing frequency. Dielectric horns offer advantages over conventional metal horns. Computer program permits user to investigate potential of various dielectricantenna designs.

Raines, J. K.↗
NASA NTRS1991

Aperture efficiency of integrated-circuit horn antennas

The aperture efficiency of silicon integrated-circuit horn antennas has been improved by optimizing the length of the dipole probes and by coating the entire horn walls with gold. To make these measurements, a new thin-film power-density meter was developed for measuring power density with accuracies better than 5 percent. The measured aperture efficiency improved from 44 percent to 72 percent at 93 GHz. This is sufficient for use in many applications which now use machined waveguide horns.

Guo, Yong↗
NASA NTRS1993

Probe impedance measurements for millimeter-wave integrated horn antennas

In order to achieve an impedance-matched millimeter-wave integrated horn antenna mixer array, the characteristics of the antenna probes inside the horn must be known. This paper describes impedance measurements for various probes in low-frequency model horns of two different types: (1) a 3 x 3 array made of aluminum by electric discharge machining and (2) a half horn made of copper sheet placed on a big copper-clad circuit board that was used as an image plane. The results of measurements indicate that the presence of the horn increases the effective length of the probe element, in agreement with reports of Guo et al. (1991) and theoretical analysis of Eleftheriades et al. (1991). It was also found that the resonant frequencies can be controlled by changing the length of the probes or by loading the probes.

Guo, Yong↗
NASA NTRS1989

Measurements of very low-sidelobe conical horn antennas

A description is given of conical corrugated-horn antennas that were designed for millimeter-wave radiometers with a 7 degree field of view, namely the Differential Microwave Radiometers (DMRs) that will measure the large-angular-scale anisotropy of the cosmic background radiation that is generally thought to be the remnant of the primeval explosion, the Big Bang. The DMRs will be part of the Cosmic Background Explorer (COBE) satellite. Measured test results for three radiometers at 31.4, 53, and 90 GHz are reported along with those of a circular polarization orthomode transducer designed and characterized at 31.4 GHz. The measurement techniques and facilities are described, including an outdoor far-field facility where measurements down to levels 90 dB below the main beam maximum were achieved. The goal of achieving very low-sidelobe antennas with good symmetry has been demonstrated.

Toral, Marco A.↗
NASA NTRS1980

Pattern measurements of a low-sidelobe horn antenna

The techniques and results of power pattern measurements of a corrugated horn antenna designed for low sidelobes are reported. The power pattern was measured to levels 90 dB below the main beam maximum in both the E- and H-planes. The measured patterns were found to be in good agreement with predictions from existing theory for the performance of corrugated scalar feeds.

Janssen, M. A.↗
NASA NTRS1989

Nonprincipal-plane scattering from flat plates: Second-order and corner diffraction and pattern control of horn antennas

Several high-frequency models for nonprincipal-plane scattering from a rectangular, perfectly conducting plate are examined. Two methods, the Method of Equivalent Currents and corner diffraction coefficients, are considered. Formulations for second-order Physical Theory of Diffraction equivalent currents and for corner diffracted fields are presented. Comparisons are made among plate models. Results away from grazing are accurate using only first-order terms. Near grazing, second-order and corner diffraction terms improve the results for many cases. The pattern control of horn antennas using lossy materials to coat the inner walls of the horn is also investigated. Integral Equation and Moment Method techniques are used to formulate the problem. It is clearly demonstrated that side lobe level reduction can be achieved using impedance surfaces on the inner walls of the horn.

Balanis, Constantine A.↗
NASA NTRS1989

Nonprincipal plane scattering of flat plates and pattern control of horn antennas

Using the geometrical theory of diffraction, the traditional method of high frequency scattering analysis, the prediction of the radar cross section of a perfectly conducting, flat, rectangular plate is limited to principal planes. Part A of this report predicts the radar cross section in nonprincipal planes using the method of equivalent currents. This technique is based on an asymptotic end-point reduction of the surface radiation integrals for an infinite wedge and enables nonprincipal plane prediction. The predicted radar cross sections for both horizontal and vertical polarizations are compared to moment method results and experimental data from Arizona State University's anechoic chamber. In part B, a variational calculus approach to the pattern control of the horn antenna is outlined. The approach starts with the optimization of the aperture field distribution so that the control of the radiation pattern in a range of directions can be realized. A control functional is thus formulated. Next, a spectral analysis method is introduced to solve for the eigenfunctions from the extremal condition of the formulated functional. Solutions to the optimized aperture field distribution are then obtained.

Balanis, Constantine A.↗
NASA NTRS1975

A corrugated horn antenna using V-shape corrugations

Corrugated horns use corrugations on the E-plane walls that are operating in the cutoff condition. In this paper, attention is focused on replacing the rectangular shaped corrugation with a V-shaped corrugation. The properties of the V corrugations are obtained using an integral equation solution; the results of the computational studies indicate that for operation of the V corrugations in the forbidden zone the depth of the corrugations lie between 0.3125 to 0.625 times the wavelength in contrast to the rectangular corrugations where the corresponding depth is 0.25 to 0.5 times the wavelength. The radiation patterns and impedance of two identical rectangular horns with corrugated E-plane walls using either V or rectangular corrugations are directly compared.

Mentzer, C. A.↗
NASA NTRS1985

Dual-Mode Horn Antenna for Millimeter Wavelengths

Millimeter-wave feed horn exhibits nearly equal beam-intensity patterns in E- and H-planes as well as low side-lobe levels. Horn includes circular waveguide step transition, and conical section. Design simplified version of Potter feed-horn design. New feed horn easier to construct, in part because of simpler shape. Reduction in phase change between step transition and aperture increases bandwidth, thereby reducing precision required to manufacture phase-sensitive dimensions of horn.

Pickett, H. M.↗
NASA NTRS2002

Evolutionary design of corrugated horn antennas

An evolutionary progranirnitzg (EP) algorithm is used to optimize pattern of a corrugated circularhorn subject to various constraints on return loss and antenna beamwidth and pattern circularity and low crosspolarization. The EP algorithm uses a Gaussian mutation operator. Examples on design synthesis of a 45 section corrugated horn, with a total of 90 optimization parameters, are presented. The results show excellent and efficient optimization of the desired horn parameters.

optimization corrugated horn antennas evolutionary↗
NASA NTRS1989

Part B: Pattern control of horn antennas

During this period, the computations of the impedance elements were completed. These include interactions between the two electric current modes, the elecric current mode and the magnetic current mode, and the two magnetic current modes. An accurate and efficient formulation of computing interactions between electric current mode and magnetic current mode was accomplished. This, together with other subroutines allows for the fill-in of all the elements in the matrix. After the fill-in of the impedance elements in the matrix, the forward problem is accomplished. That is, given the specification of the horn and the excitating waveguide mode, the radiation pattern of the antenna based on the integral equation can be obtained. An example case was run for a standard X-band gain-horn (DBG-520). The H- and E-plane patterns of this horn antenna with perfectly conducting walls are compared with the gain pattern available from the manufacturer for up to the first side lobe. Good agreements are obtained although the cross polarization has not yet been accounted for. The effect of the lossy coating on the radiation pattern was also investigated. The resulting E-plane pattern shows about 3-dB improvement in the first sidelobe and 4-dB improvement in the second sidelobe.

Balanis, Constantine A.↗
NASA NTRS1971

Dual-frequency feed-horn antenna

Antenna with novel two-port diplexer separates high power /31.65 GHz/ transmitted signal from low power /15.2 GHz/ received signal. Two-port network feeds dual-frequency horn and excites antenna with minimal loss in power. Isolation between transmit port and receive port ranges from 60 db to 80 db.

Schuchardt, J. M.↗
NASA NTRS1975

Horn antenna with v-shaped corrugated surface

Corrugated shape is easily machined for millimeter wave application and is better suited for folding antenna designs. Measured performance showed ""V'' corrugations and rectangular corrugations have nearly the same pattern beamwidth, gain, and impedance. Also, ""V'' corrugations have higher relative power loss.

Beck, F. B.↗