Reconfigurable Reflector Research Articles

Synthesis technique for scanning and/or reconfigurable beam reflector antennas with phase-only control

Scanning and/or reconfigurable reflector antennas can be conveniently set up by using a hybrid antenna consisting of a reflector illuminated by a small phase-only controlled array feed. However, no general synthesis procedure performing the optimum design of such antennas seems to exist. In the paper a new general and flexible formulation of this synthesis problem is presented together with an iterative solution scheme, which make it possible to determine simultaneously the reflector geometry, the amplitude of the excitation coefficients common to all radiated beams and the phases of such excitations corresponding to each beam. The technique handles general and flexible requirements on the radiated beams (expressed by masks) as well as general constraints on the excitations of the feed array elements (the phase-only control is one of these). Furthermore, it exploits a new choice for the quantity to which the design specifications concerning the radiated field are applied, in order to alleviate the trapping problems encountered in power synthesis. A numerical analysis is performed in order to demonstrate the effectiveness of the approach as well as the possibilities offered by the hybrid reflector antenna configuration.

Adaptive null formation with a reconfigurable reflector antenna

The paper reports on a reconfigurable mesh reflector antenna which adaptively adjusts the reflector surface so as to produce a pattern null in the direction of an interfering source. Deep nulls in the sidelobe region are formed after less than 50 iterations, with little degradation of the remainder of the pattern. An experimental system based on a reconfigurable mesh reflector antenna has been built and used to demonstrate the techniques. It is believed that this represents the first demonstration of adaptive nulling using control of a reflector surface rather than the excitations of array or feed array elements. Applications lie where there is no a priori knowledge of the interference location which includes both civil and military scenarios.

Reconfigurable reflector antenna producing pattern nulls

The paper reports how a reconfigurable mesh reflector antenna can be used to generate nulls in its radiation pattern while closely maintaining the original pattern in regions away from the null. The theory is developed and theoretical results are presented for a typical antenna of a size suitable for spacecraft applications. Experimental results, which are in close accord with theory, are given for an offset mesh reflector which is scaled to approximately 30 wavelengths in diameter and is fed by a corrugated horn. It is shown that deep nulls can be formed both within the mainbeam and within the side-lobe region. Applications of the offline mode of operation lie where there is a priori knowledge of the location of the interfering source, which could be the case in civil scenarios, including those of some deep-space missions requiring communication with an Earth-based transmitter.

Array-fed reconfigurable reflectorfor spacecraft systems

The authors describe a new type of reconfigurable reflector antenna for spacecraft applications in which both the reflector shape and the excitation of a small array feed combine to offer maximum coverage flexibility. To create a reconfigurable continental coverage the array is excited to produce a suitably tapered circularly symmetric pattern and the shape of the mesh reflector adjusted to yield the appropriate secondary radiation pattern. When spot beams are required within the coverage region, the mesh reflector is configured as a paraboloid and individual elements or local clusters excited within the array.

Array-fed reconfigurable reflector for spacecraft applications

The paper describes a new type of reconfigurable reflector antenna for spacecraft applications, in which both the reflector shape and the excitation of a small array feed combine to offer maximum coverage flexibility. To create a reconfigurable continental coverage, the array is excited to produce a suitably tapered, circularly symmetric pattern, and the shape of the mesh reflector adjusted to yield the appropriate secondary radiation pattern. When spot beams are required within the coverage region, the mesh reflector is configured as a paraboloid, and individual elements or local clusters excited within the array. The results of a theoretical study are described which involve a representative 50 lambda reflector. The comparison between experiment and theory is made using a prototype mesh reflector, whose performance with a single feed has been previously described, and whose centre operating frequency is 10 GHz. The antenna is fed from a 19-element array of small dominant-mode conical horns. Generally, excellent agreement between theoretical predictions and experimental results is obtained.

Null synthesis for shaped reflector antennas

Some preliminary results are presented, demonstrating the feasibility of synthesising reflector profiles to produce deep nulls in the radiation pattern at prescribed angles while maintaining high gain levels at other prescribed angles. The synthesis technique can be applied to both shaped rigid and reconfigurable mesh reflector antennas. Experimental results for an 85cm mesh reflector antenna at 10GHz are included to provide validation of the technique.

Experimental verification of an electronically controlled reconfigurable reflector antenna

First results are presented demonstrating the feasibility of electronically controlled reconfiguration of a mesh reflector antenna. Spot-beam and shaped-beam patterns taken at 10 GHz using an 85 cm diameter reflector are in close accord with those predicted theoretically.

Design and performance of a reconfigurable mesh reflector antenna. Part 2: Antenna performance

For pt.1 see ibid., vol.138, no.6, p.485-92 (1991). The paper describes the performance of an electronically controlled reconfigurable mesh reflector antenna operating at a frequency of 10 GHz. The antenna, which is controlled from a personal computer, is capable of being reconfigured to achieve a wide range of antenna patterns. Patterns are measured using the QMW compact antenna range and excellent agreement is obtained between measured and predicted results. Reconfiguration between a high-gain beam and a shaped beam is demonstrated as well as the potential for beam scanning without feed movement.