G. Amendola

Antennas for Modern Small Satellites

Modern small satellites (MSS) are revolutionizing the space industry. They can drastically reduce the mission cost, and can make access to space more affordable. The relationship between a modern small satellite and a ldquoconventionalrdquo large satellite is similar to that between a modern compact laptop and a ldquoconventionalrdquo work-station computer. This paper gives an overview of antenna technologies for applications in modern small satellites. First, an introduction to modern small satellites and their structures is presented. This is followed by a description of technical challenges in the antenna designs for modern small satellites, and the interactions between the antenna and modern small satellites. Specific antennas developed for modern small-satellite applications are then explained and discussed. The future development and a conclusion are presented.

A Compact High Gain Antenna for Small Satellite Applications

The development of a circularly-polarized compact high-gain antenna to be used for the European Student Earth Orbiter small satellite mission is described. The antenna is realized stacking two coaxial shorted annular patches and placing the top one at half a wavelength from the lower one. At variance of other similar configurations proposed in the past, the one presented in this paper has several important features which can be extremely useful for application in the space environment. In particular, it can be easily fabricated employing suspended technology and its radiation characteristics are to some extent controllable by opportunely varying the geometry. In the following, a straightforward design procedure will be presented detailing the criteria to optimize top and bottom radiating elements. Both numerical and measured results will show that the proposed design satisfies the specifications and presents characteristics comparable to other larger and heavier solutions usually more difficult to design. Specifically, it will be shown that with this configuration it is possible to obtain gain values higher than 12 dB using ground plane of moderate size and that a further improvement up to 15dB can be obtained employing larger ground planes

Analysis of Substrate Integrated Waveguide Structures Based on the Parallel-Plate Waveguide Green's Function

This paper presents the full-wave characterization of substrate integrated waveguide structures. Substrate integrated circuits are considered as an ensemble of conducting posts placed in a parallel-plate waveguide and are analyzed in terms of the cavities formed by the top and bottom conducting plates and by the walls of the metallic vias. The field inside the parallel-plate waveguide is computed by considering the dyadic Greens function expressed as an expansion in terms of vectorial cylindrical eigenfunctions and considering the scattering from the ensemble of conducting posts. Coaxial or waveguide ports are included in the analysis as equivalent magnetic current distributions. Self-admittance and mutual admittance are calculated in a form that separates the parallel-plate contribution from the field scattered by the posts. Results relevant to structures already presented in literature will be shown and compared with simulations obtained with one of the most used articles of commercial software. It will be shown that an excellent agreement with published results is achieved together with significant improvements both in computational time and memory requirements.

A shorted elliptical patch antenna for GPS applications

An L1 Global Positioning System (GPS) antenna with improved multipath-rejection capability is presented. The antenna is realized with a shorted annular elliptical patch (SAEP). Some of the characteristics of SAEP are presented briefly and a detailed account of the design is given. Measured results are presented and discussed.

Performance Improvement for a Varactor-Loaded Reflectarray Element

The application of varactor diodes as phase-shifting devices in reflectarrays has received considerable attention because it represents a low-cost and low-complexity solution for the creation of scanning antennas with continuous phase tuning. The main issues related to the design of varactor-loaded reflectarrays are the difficulty in the correct characterization of the unit cell, and the limited phase range achievable by changing the polarization voltage of the device. The contribution presented in this communication attempts to cover both these aspects. In particular, a simple model for the analysis of a varactor-loaded microstrip reflectarray cell is presented, and then employed to increase the patchs phase response to 360° . The result is then validated experimentally, with the results showing good agreement between simulated and measured data.

Aperture-Coupled Reflectarrays with Enhanced Bandwidth Features

An extensive analysis is performed on the aperture-coupled reflectarray configuration to highlight and quantify the bandwidth enhancement due to the use of reduced inter-element spacings. Bandwidth extension is directly evaluated on the phase curves relative to the reflection coefficient against frequency for different lengths of the tuning line. The operating frequency range computed with the proposed approach is numerically validated on the gain patterns of synthesized reflectarrays and a strong broadband behavior is demonstrated for reflectarrays of moderate aperture dimensions and reduced unit cell size.

Multilayer Antenna-Filter Antenna for Beam-Steering Transmit-Array Applications

This paper presents a study on reconfigurable transmit-array (TA) antennas based on multilayer tunable elements. The proposed configuration can be referred to as a multilayer antenna-filter antenna (MAFA) and it can be viewed as an extension of the antenna-filter antenna concept. It consists of multiple antenna layers cascaded to form a spatially distributed bandpass filter. Phase agility is achieved by tuning the resonant frequency of each layer. The main objective of this paper is to introduce a new design technique for MAFA TA antennas. As will be shown, the key feature of the proposed approach is that it allows to simultaneously take into account three key design parameters: the phase tuning range, the maximum acceptable losses per unit cell, and the operating bandwidth. Simulations and experimental results for MAFAs based on varactor-loaded slot antennas will be illustrated to prove the validity of the proposed method. In particular, numerical results will demonstrate that MAFA cells can be designed to provide full phase agility over operating bandwidths of up to 10% with maximum insertion losses of 3 dB. Furthermore, a specific example will show how introducing an inter-layer medium with a higher dielectric permittivity it is possible to reduce the array longitudinal size. Finally, experimental results obtained using a waveguide simulator will be presented for a 1 × 3 five-layer MAFA cell.

Hybrid Array Antenna for Broadband Millimeter-Wave Applications

A hybrid array configuration suitable for wideband millimeter-wave applications is presented in this work. The proposed structure is based on the use of circular waveguide elements electromagnetically coupled trough circular apertures to a stripline distribution network. The adopted excitation mechanism avoids the use of transition components generally reducing the overall antenna efficiency. Simulated and measured results on a Ka-band prototype are discussed to prove the wideband radiation behavior.

Application of varactor diodes for reflectarray phase control

A new approach for beam steering in reflectarray applications is introduced in this paper. The progressive phase distribution is achieved by loading each microstrip patch element with a varactor diode on the radiating edge. In the following, the scattering characteristics of a single varactor loaded patch antenna will be presented. As a proof of concept, the beam steering capability of a five elements linear reflectarray has been experimentally investigated.

Method of Moments Analysis of Slotted Substrate Integrated Waveguide Arrays

A method of moments analysis is described for substrate integrated waveguide slot arrays. The array structure is modeled as a parallel plate waveguide on which via holes and slots are created. The field into the waveguide is expressed by the sum of the parallel plates contribution and the field scattered by the metallic through holes, with both contributions expressed by means of an expansion in terms of vectorial cylindrical eigenfunctions. The slots are modeled as unknown equivalent magnetic current distributions which are found by solving an integral equation derived from the continuity of the field on the slot surface. Antenna arrays already presented in the literature will be analyzed, and the results compared with HFSS simulations. It will be shown that the proposed method is efficient and gives results in excellent agreement with the most common simulation tools.