Large Deployable Reflector Antenna Research Articles

Review and evaluation of warp-knitted patterns for metal-based large deployable reflector surfaces

A large deployable reflector antenna (LDA) is comprised of numerous components. One of the key components of this reflector antenna is the reflector surface. Several types of reflector surfaces have been developed and used, namely, metal mesh-based reflector surfaces, membrane-based reflector surfaces, etc. The benefits presented by warp-knitted metal mesh-based reflector surfaces are their foldability and light weight structural characteristics. Typical metal mesh-based reflector surfaces are produced using a warp knitting textile manufacturing process. A warp-knitted metal mesh reflecting surface is an elastic, open structured knit with a low bending stiffness produced on a high gauge knitting machine (E26 or higher gauge) consisting of a compatible metal yarn (typically tungsten or molybdenum). This paper gives an overview about the requirements for mesh reflector surfaces stated in the literature. Afterwards, an overview of different patterns currently investigated by the LDA community is given. The names given to the various types of patterns in the literature often differ. The construction of the various patterns is therefore first optical analysed and compared. Subsequently, the different patterns are evaluated on the basis of the requirements. Based on the requirements and the possibilities of the warp knitting machine, new possible patterns are identified and evaluated. For the development of a new reflector surface, the identified patterns are developed as a warp-knitted spacer fabric. This decision increases the stiffness of the knitted fabric. This new concept for an advanced reflector surfaces is introduced by Large Space Structures GmbH (LSS) (concept) and ITA (production technology).

Insensitivity Characteristics in the Dual Polarization of Deployable CFRP Reflector Antennas for SAR

A large deployable reflector antenna is considered and designed for the application of a synthetic aperture radar system requiring high gain for the high resolution of a detected image within a distance of a few hundred kilometers. For its lightweight and strong characteristics, carbon fiber reinforced polymer (CFRP) is introduced as a composite material and fabricated for conductivity evaluation. Effective electrical characteristics are obtained as a function of carbon fiber direction, using measured S-parameters in a rectangular waveguide. By taking into account the changes of the effective electrical characteristics that depend on the fiber direction of reflector antenna, the radiation pattern is investigated at X-band in terms of gain and polarization variation effects. The proposed reflector antenna made of quasi-isotropic CFRP panel can realize the insensitive characteristics depending on the incident polarization.

Mesh Mapping of Large Deployable Reflector in Mechanical - Electromagnetic Analyses

Ultra lightweight large deployable reflector antenna is gradually used nowadays in space applications. Both lightweight structures and materials are used. The relationship between the structure design and the electromagnetic performances is much tighter than other ground electric devices. This paper presents a mesh mapping method of large deployable reflector in mechanical - electromagnetic analyses. By using this method, the mechanical deformations can be precisely transformed on the electromagnetic model. It can be used to understand the relationship between the mechanical deformations and the electromagnetic performances on such a huge, complex structure.

Subreflectarrays for Reflector Surface Distortion Compensation

With the increasing interest in the applications of large deployable reflector antennas operating at high frequencies, the requirement on the reflector surface accuracy becomes more demanding. Thermal effects inevitably cause certain reflector surface distortions, thus degrading the overall antenna performance. This paper introduces a novel reflector surface distortion compensation technique using a subreflectarray and presents detailed discussions. A microstrip reflectarray is used as a subreflector, illuminated by a primary feed. By properly adjusting the additional phase shift provided by the subreflectarray, the aperture phase errors caused by the main reflector surface distortions are compensated, resulting in a considerably improved antenna performance. As an example, a distorted 20-m offset parabolic reflector antenna operating at X-band is successfully compensated by a subreflectarray, and the simulation results are compared with those obtained by array feed and shaped subreflector compensation techniques. The microstrip subreflectarray is low-profile, lightweight, and cost-effective. Only one primary feed is required, and a reconfigurable design can be achieved if electronically reconfigurable reflectarray elements are adopted.