J.L. Besada

Low-cost millimeter-wave beacon receiver including total-power radiometer: design, implementation and measurement calibration

An experimental Earth station has been installed in Madrid, with the aim of studying the propagation characteristics in the Earth-space link at 50 GHz. The station, which consists of a beacon receiver and a radiometer, was constructed in the University at a very reduced cost, compared to commercially available equipment of similar characteristics. The receiver measures the co-polar and cross-polar signal amplitudes and phases for two linear polarizations, with a 30 dB fade margin for the co-polar signals. General descriptions of the various parts of the equipment, as well as some examples of measurements, are presented in the article.

Shaped compact dual reflector antenna for Ku-band satellite pico-terminals

Pico-terminals for digital communications satellite systems need compact reflector antennas with a high aperture efficiency but with a controlled side lobe level. Shaped reflectors with an also shaped splash-plate meet both conditions satisfactorily. Such a solution was selected for the antenna of the remote user terminal of a CDMA satellite system (PRODAT project). This paper discusses its design and features.

On the radiation of horn clusters including mutual coupling and the effects of finite metal plates: application to the synthesis of contoured beam antennas

This work describes a model of the radiation of horn clusters for contoured beam antennas. The model includes internal mutual coupling (through a power divider network), modal conversions and reflections inside the horns, external mutual coupling and the effects of the edges of the metal plate that holds the cluster together. This model is applied to the synthesis of the direct broadcast satellite (DBS) antenna of the HISPASAT satellite, the computed immersed patterns of each horn being used in the optimization of the excitations. Results are given concerning model validation and optimization with immersed patterns. >

SABOR: description of the methods applied for a fast analysis of horn and reflector antennas

The program presented in this paper is intended to provide a valuable aid for teaching antennas to electrical engineers, and to provide fast and accurate pre-designs for professionals. This paper covers the theory and numerical techniques used in SABOR. In summary, this program computes the radiated field of an aperture antenna (horn or reflector), using a common engine based on the Gauss-Legendre quadrature method for evaluating the radiation integrals. For horn, the aperture fields are the usual dominant modes of the feed waveguide, with a quadratic phase correction. For reflectors, the aperture fields are computed using geometrical optics ray tracing from the feed horn. Also, equivalent-reflector concepts are applied for dual-reflector antennas. The paper includes some examples to demonstrate the most important features of the program.

Beam mode expansion applied to horn system with meniscus lens: new application to radioastronomy receivers

Classical radioastronomy receivers are fed by a corrugated horn and independent lens, both of them placed in a cryostat to lower noise temperature. In addition, the beam is focused and driven using several elliptical and plane mirrors. The paper proposes to modify the initial feeding system, placing the lens onto the horn aperture, allowing a size reduction of the horn and lens and a simplification of their mechanical design. This profile lens is designed to correct phase error at the horn aperture. A quasi-optical model of horn plus lens system using beam mode expansion (BME) has been developed. Results using a spherical-elliptical lens and those from optical geometry theory (GO) have been compared.

Quasioptical Approach for Meniscus Lens Corrected Horn: Application to Cassegrain Systems

The Beam Mode Expansion (BME) approach for corrugated conical feed horn plus meniscus lens is presented. This approach is useful for providing the radiation pattern as it propagates through an optical system. A developed theoretical model has been verified measuring near and far field of a built horn and lens. These results have been used for designing the optical system of a Cassegrain antenna at 100GHz using the fundamental Gaussian beam mode (GBM) of the new approach. Multimode analysis has been performed with the pre-designed system in order to test the fundamental GBM results.

Design of Horn Clusters Including Edge Effects and Mutual Coupling

Computation of immersed patterns including mutual coupling and edge effects is proposed in order to define a new step for the synthesis of multifed antennas. This procedure has been applied to the DBS and AMERICA-GOV antennas of HISPASAT satellite reaching an improvement versus synthesis with isolated patterns.

Applications of the diagnosis techniques in antenna for the reduction of the measurements errors

This paper shows several applications of the diagnostic techniques for the reduction of some error or uncertainty factors in antenna measurements. The method is based in the calculation of the extremely near field from the far field using FFT (Fast Fourier Transform) Techniques, improved with the Gerchberg-Papoulis Algorithm. The classical applications of the diagnostic techniques are errors detection, like phase errors in arrays or conformal errors in reflectors. Therefore, they constitute an important antenna design tool. Also, they can be used for other applications whose aim is improve the measurements in anechoic chambers. This paper shows different process applied to reduce the effect of the reflections, the effect of the leakage from AUT (Antenna under test), to improve the signal to noise and to reduce the truncation error in the planar or cylindrical near field.

Focalization of new 40 m radiotelescope of Centro Astronomico de Yebes

The paper presents the solution for the focalization of the new 40 m radiotelescope of the Centro Astronomico de Yebes (CAY) in Guadalajara, Spain. Quasi-optics theory is used for the propagation analysis of the beams through the different optical elements. The goal of the paper is to design the optical system that can focalize several bands reducing to the minimum number of possible optical elements, and sharing the maximum number of them. Hyperbolic lens and ellipsoidal mirror parameters, focal distances, and the feeder dimensions necessary for the focalization in each band are calculated.

An optical solution for the radioastronomic observation bands of the new 40 m radiotelescope of Centro Astronomico de Yebes

In this paper is presented a solution for the focalisation of the new 40 m radiotelescope of the Centro Astronomico de Yebes (CAY) in Guadalajara, Spain. Quasi-optics theory is used in this paper for the propagation analysis of the beams through the different optics elements. The goal of this paper is to design the optical system that can focalize several bands reducing to the minimum number of possible optic elements, and sharing the maximum number of them. Hyperbolic lenses and ellipsoidal mirrors parameters, focal distances, and the feeder dimensions necessary for the focalization in each band are calculated.