Joshua M. Kovitz

MEMS Reconfigurable Optimized E-Shaped Patch Antenna Design for Cognitive Radio

Reconfigurable antennas offer attractive potential solutions to solve the challenging antenna problems related to cognitive radio systems using the ability to switch patterns, frequency, and polarization. In this paper, a novel frequency reconfigurable E-shaped patch design is proposed for possible applications in cognitive radio systems. This paper provides a methodology to design reconfigurable antennas with radio frequency microelectromechanical system (RF-MEMS) switches using particle swarm optimization, a nature-inspired optimization technique. By adding RF-MEMS switches to dynamically change the slot dimensions, one can achieve wide bandwidth which is nearly double the original E-shaped patch bandwidth. Utilizing an appropriate fitness function, an optimized design which works in the frequency range from 2 GHz to 3.2 GHz (50% impedance bandwidth at 2.4 GHz ) is obtained. RF-MEMS switch circuit models are incorporated into the optimization as they more effectively represent the actual switch effects. A prototype of the final optimized design is developed and measurements demonstrate good agreement with simulations.

Nature-Inspired Optimization Techniques in Communication Antenna Designs

This paper summarizes the primary features inherent in current optimization methods typically applied to antenna designs and demonstrates their effectiveness by applying particle swarm optimization (PSO), a nature-inspired global optimization technique, to novel antenna design solutions in wireless communications. The concept of the PSO technique is briefly introduced and an outline of the important parameters that are utilized is summarized. Next, an implementation strategy combining PSO with numerical algorithms for electromagnetic solutions, namely the finite element method (FEM) and the method of moments (MoM), is discussed. In both realizations (PSO-FEM and PSO-MoM), the PSO technique drives the design variables, such as the antenna dimensions, geometrical features, etc., and the full-wave electromagnetic analysis engines evaluate the fitness function for the optimizer. Optimized antenna designs including a multiband handset antenna and an E-shaped patch antenna for circularly polarized (CP) applications are presented. Measurement results of prototype optimized designs are shown to demonstrate the functionality and effectiveness of the methodologies presented in this paper.

Design and Implementation of Broadband MEMS RHCP/LHCP Reconfigurable Arrays Using Rotated E-Shaped Patch Elements

A novel broadband RHCP/LHCP reconfigurable patch antenna array using an E-shaped patch antenna element is investigated. By applying particle swarm optimization (PSO), a challenging, combined S11-AR bandwidth of 17% was achieved and verified through measurement for the isolated element using MEMS switches at an overall substrate thickness of 0.092λ0. The achieved bandwidth is significantly higher than the current state-of-the-art in single-layer, single-feed circularly polarized (CP) patch element designs with similar substrate thickness. A small percentage of the upper frequency band experiences a pronounced beam squint similar to other thick substrate CP patch antennas. To overcome the beam squint, a novel rotated-element configuration is implemented to force pattern symmetry. Derivations of pattern symmetry and network effects are also shown. The final design prototype using rotated elements provides a measured 20% S11-AR bandwidth with good radiation pattern stability.

Frequency reconfigurable wideband E-shaped patch antenna: Design, optimization, and measurements

This paper presents the design of a frequency reconfigurable wideband E-shaped patch antenna using particle swarm optimization. Ideal switches are used to demonstrate proof of concept of frequency reconfigurability. Utilizing an appropriate fitness function, an optimized design which works in the frequency range from 2GHz to 3.25GHz (53% total bandwidth) is obtained. A prototype of the design is developed and measurements are performed.

Practical and Cost-Effective Bias Line Implementations for Reconfigurable Antennas

Bias lines form an integral part of the reconfigurable antenna design process. Current methodologies for bias lines are either too narrowband or require a relatively large amount of real-estate that may not be available. Also, metallic lines are unsuitable for designs with strong fields in the bias line location. Bias lines using resistive materials are often prototyped using microfabrication facilities, but these facilities might not always be accessible. This letter investigates a novel, practical, and cost-effective bias line solution using conductive adhesives. These resistive lines effectively attenuate the RF signals providing good isolation between the RF and the dc signals while still passing a dc voltage to activate the switches. The reconfigurable E-shaped patch antenna is used as a case study in this letter, and some issues when using metallic lines in this type of antenna are also presented. The newly proposed bias line aims to minimize those issues shown hereafter. The fabrication process is also enumerated for those interested in repeating these designs for other applications. Overall, the S11 and pattern measurements show good agreement with the simulations and prove their effectiveness experimentally.

For Satellites, Think Small, Dream Big: A review of recent antenna developments for CubeSats.

Advances in modern technology have aided the development of a class of miniaturized satellites called SmallSats that typically weigh less than 500 kg. Key members of this family are CubeSats. CubeSats can weigh as little as 1.33 kg, with a typical volume of 10 ? 10 ? 10 cm³. Their potential has motivated the scientific community to revisit existing spacecraft technologies to make them suitable for CubeSats.

A spline-profiled conical horn antenna assembly optimized for deployable Ka-band offset reflector antennas in CubeSats

With the advent of small-scale satellite technologies, there has been significant interest in developing advanced functionalities for CubeSat and SmallSat projects. Developing high-gain antennas within this paradigm opens the door for many new applications which require high data rates or narrow-beam patterns. In this paper, we discuss the optimization of a compact, spline-profile horn antenna assembly that could be used as a feed for future deployable offset reflector antennas in CubeSats.

Understanding the radiation pattern anomalies in the broadband CP reconfigurable E-shaped patch

Recently a CP reconfigurable E-shaped patch antenna was proposed for broadband use with over 17% AR-S11 bandwidth. However, it has been observed that beam squints begin to appear in the upper frequencies of the band of operation. This paper reveals these beam squints and provides some insight into their origin. We investigate these beam squints by examining their aperture near-fields and show that these squints result from the excitation of a mode similar to the rectangular TM11 mode.

Micro-actuated pixel patch antenna design using particle swarm optimization

Reconfigurable antennas are quite useful because of their versatility in many different applications. An innovative approach for configuring these antennas using an optimizer is investigated. This is accomplished by implementing particle swarm optimization as the antenna controller. Simulation results show rapid convergence onto optimal pixel configurations for a desired resonant frequency. In summary, the Software Optimized Antenna (SOA), a novel class of antenna, is being proposed and investigated.

Dispersion engineered right/left-handed transmission lines enabling near-octave bandwidths for wideband CP patch arrays

Composite right/left-handed (CRLH) transmission lines have recently attracted a significant interest due to their abilities to generate phase characteristics which go beyond the typical right-handed lines. In this work, we demonstrate their use in generating a wideband quadrature phase excitation for creating circular polarization (CP) with antenna systems capable of generating two orthogonal polarizations. In particular, we investigate their application towards a patch antenna array of sequentially rotated elements. By engineering the dispersion of the CRLH lines, we have been able to measure roughly 60% AR-S11 bandwidth with a prototyped 2 × 2 array of sequentially rotated wideband, single layer patch antennas.