L. Boccia

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

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.

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.

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.

Experimental investigation of a varactor loaded reflectarray antenna

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.

Resonant Frequencies of Circular Substrate Integrated Resonators

In this letter, the characterization of circular resonators realized in substrate integrated waveguide technology is presented. Resonances are found by setting up the equations of the scattering for an ensemble of metallic posts in parallel plates waveguide and considering the nontrivial solution to the corresponding homogeneous problem. Resonant frequencies are then located by means of an efficient strategy, based on an estimate of the minimum singular value. In the last part of the letter a data fit formula of practical use is presented for circular resonators with a wide range of geometrical and electrical parameters resonating on TM010 and TM110 modes.

Analysis of Lossy SIW Structures Based on the Parallel Plates Waveguide Green's Function

In this paper, a full-wave analysis technique of lossy substrate integrated waveguides, based on the dyadic Greens function of the parallel plate waveguide, is presented. The fleld inside the waveguide is expressed in terms of cylindrical vector wave-functions and the flnite conductivity of the top and of the bottom plates, and of the metallic vias are taken into account. Losses into the dielectric substrate are also included. Coaxial ports are considered as sources and self and mutual admittances are evaluated. Cases of practical structure taken from literature are presented showing a very good agreement with the most used commercial software.

Shorted elliptical patch antennas with reduced surface waves on two frequency bands

In this paper, a study on the surface waves emission of a shorted annular elliptical patch (SAEP) antenna is presented. This radiator is constituted of an annular elliptical patch having the inner border shorted to the ground plane. The surface wave field excited by the SAEP antenna has been evaluated considering an equivalent magnetic current distribution flowing onto the outer boundary of the patch. It will be demonstrated that the dimensions of the outer elliptical contour can be chosen in such a way that the excitation of the TM/sub 0/ surface wave mode is suppressed on two frequencies. This characteristic makes possible the design of SAEP antennas with reduced surface wave (RSW) emissions on two frequency bands. To validate this result both numerical simulations and measurements will be presented. In particular, it will be shown that when the RSW-SAEP is considered the field strength within the substrate undergoes a faster decay resulting in a reduced mutual coupling in dual band array applications. Furthermore, the effective reduction of the surface waves power minimizes the scattering from the ground plane edges leading in smoother radiation patterns.