Reflective array antenna

About: Reflective array antenna is a research topic. Over the lifetime, 4366 publications have been published within this topic receiving 57884 citations.

A phased-array antenna using a multi-line phase shifter controlled by a piezoelectric transducer

Abstract: A new phased-array antenna of wide bandwidth with beam scanning capability has been developed. The array uses a multi-line time-delay phase shifter controlled by a piezoelectric transducer (PET) and a Vivaldi antenna array. The multi-line phase shifter controlled by the PET has an increased insertion loss of less than 1 dB and phase shift of 0/spl deg/ to 360/spl deg/ up to 20 GHz. The proposed phased-array antenna demonstrated a beam scanning capability from -16/spl deg/ to +17/spl deg/ at 10 GHz. Similar results were obtained from 10 to 18 GHz. The use of PET controlled phase shifter has advantages of low cost and low loss over a wide bandwidth.

Why Does Reflector Enhance the Gain of Helical Antennas

Abstract: We investigate uniformly-wound helical antennas above ground conductors of various shapes, with aim to determine factors that improve the antenna radiation pattern and gain. We show that the characteristics of helical antennas with large spillover fields can be improved using ground conductors (reflectors). This is achieved by intercepting unwanted radiation and redirecting it favorably. (8 pages)

Optical and Microwave Beamforming for Phased Array Antennas

Abstract: Phased array antenna has been used for a variety of military and civil applications, over the past five decades. Being structurally conformal and flexible, phased array antenna is highly suitable for mobile applications. Besides, it can form the agile or shaped beams required for interference cancellation or multifunction systems. Moreover, the spatial power combination property increases the effective radiated power of a transmitter phased array system. Similarly, in a receiver phased array, beamforming increases the signal to noise ratio by coherent integration of the desired signals. Despite its impressive potentials and properties, phased array antenna has not become a commercial product yet. Cost and complexity of phased array antenna are beyond the scales of consumer electronics devices. Furthermore, calibration is an essential requirement of such a complex system, which is a fairly time-consuming process and requires skilled man power. Moreover, the narrow bandwidth of microwave components degrades the broadband performance of phased array system. Finally, the majority of the beamforming algorithms developed so far have preconditions, which make them unsuitable for a low-cost system. The objective of this thesis is to provide a novel cost-effective solution to minimize the system complexity of the future intelligent antenna systems, without sacrificing the performance. This research demonstrates that a powerful, robust beamforming algorithm, integrated in an efficient single-receiver architecture, constitutes the essence of a low-cost phased array antenna. Thus, a novel beamforming technique, called Zero-knowledge algorithm is developed. It is investigated, both theoretically and experimentally, that the proposed algorithm can compensate for the hardware errors and imperfections of the low-cost components of the system. Zero-knowledge beamforming algorithm possesses significant properties. Neither a priori knowledge of the incoming signal direction, nor the exact characteristics of the phase control network are required in this method. Proper adjustment of the parameters, makes this algorithm appropriate for mobile systems, particularly those installed on vehicles. The algorithm alleviates the drawbacks of analog phase shifters, such as imbalanced insertion loss and fabrication tolerances. Furthermore, this algorithm can serve as the core of a direction-of-arrival estimation technique, which senses the minor deflections of the array heading. For broadband applications optical delay lines must be used in the phase control network of the phased array systems, which are costly. Nevertheless, employing

Transparent Antennas for Solar Cell Integration

Abstract: Transparent patch antennas are microstrip patch antennas that have a certain level of optical transparency Highly transparent patch antennas are potentially suitable for integration with solar panels of small satellites, which are becoming increasingly important in space exploration Traditional patch antennas employed on small satellites compete with solar cells for surface area However, a transparent patch antenna can be placed directly on top of solar cells and resolve the issue of competing for limited surface real estate For such an integration, a high optical transparency of the patch antenna is required from the solar cells' point of view On the other hand, the antenna should possess at least acceptable radiation properties at the same time This dissertation focuses on some of the most important concerns from the perspective of small satellite applications For example, an optimization method to simultaneously improve both optical transparency and radiation efficiency of the antenna is studied Active integrated antenna design method is extended to meshed patch applications in an attempt to improve the overall power efficiency of the front end communication subsystem As is well known, circular polarization is immune from Faraday rotation effect in the ionosphere and thus can avoid a 3-dB loss in geo-satellite communication Therefore, this research also aims to present design methods for circularly polarized meshed patch antennas Moreover, a meshed patch antenna capable of supporting a high communication data rate is investigated Lastly, other types of transparent patch antennas are also analyzed and compared to meshed patches In summary, many properties of transparent patch antennas are examined in order to meet different design requirements

Helical antennas for multi-mode mobile phones

Abstract: The use of helical antennas in handsets for multi-frequency operation has been studied. It is shown that it is possible to obtain very wideband operation or two separate frequency bands of operation by using two helical antennas attached on the top edges of the conducting case of a handset. The presence of the second antenna has relatively small effect on the operation. If one of the single helical antennas is replaced with two helical antennas one within the other three separate frequency bands of operation can be obtained.