Steven J. Franson

Implementation and Experimental Verification of a Smart Antenna System Operating at 60 GHz Band

With the introduction of the unlicensed spectrum at the 60 GHz range, the development of communication systems with data rates in Gb/s range has become feasible. However, there are quite significant challenges at this frequency range such as high propagation loss, oxygen absorption, antenna alignment and unavailability of high-gain, high power circuit elements. In this paper we present a novel 2-channel hybrid smart-antenna system operating at 60 GHz band which can be used with an antenna switching system to improve the signal power performance and to serve as an automated alignment system. The critical system parameters for a smart-antenna system at this frequency are the transmitter to receiver distance, element spacing, and antenna beamwidth. As the widely known beamforming assumptions may not hold for some configurations, a more general beamforming formulation is given in the paper to serve as a guideline for system designers. The twist angle of array elements is introduced as a new array design parameter. By selecting the optimal twist angle to help overlap radiation patterns, the fine alignment of the transmit and receive beams is established electronically using beamforming, thus reducing the cost of deployment and maintenance of the 60 GHz indoor communication systems.

Gigabit per Second Data Transfer in High-Gain Metamaterial Structures at 60 GHz

While much metamaterial research has concentrated on the exotic physical properties of metamaterial structures and their potential applications, there has been little reported on the usefulness of these metamaterial structures in actual applications, for example, in communications systems. Moreover, since many metamaterials are designed for operation at very specific frequencies, there are reasonable concerns for how they will act when they are applied to high-data-rate systems. This paper takes a zero-n grid structure that has been shown previously to produce high directivity in the microwave regime, and demonstrates its usefulness for real wireless data transfer in the millimeter-wave regime. The design frequency is selected to be 60 GHz, where there is a large swath of worldwide available bandwidth. An improvement in the overall system gain with no degradation of its gigabit per second data transfer is demonstrated.

Confirmation of Zero-N Behavior in a High Gain Grid Structure at Millimeter-Wave Frequencies

A multilayer grid structure that has been used previously to create an antenna with high directivity and gain and that has been explained as having a near zero index of refraction is extended to millimeter-wave frequencies. Alternate explanations for the associated phenomena are examined. Further confirmation of this zero-n behavior is presented.

Gigabit per second data transfer at 60GHz in high gain grid antennas

A significant issue in the field of metamaterials is the demonstration of their usefulness in actual communication systems. This paper uses the known grid structure [1-3] as a highly directive superstrate, suspended over a patch antenna, to transfer high data rate signals. The design frequency is at 60 GHz, where worldwide there is several GHz of available unlicensed bandwidth. We measure the system gain of the antenna, and demonstrate its operation with a multi-gigabit per second signal. The grid antenna has been described as having a near zero index of refraction, however, the grid can also be viewed as an antenna aperture. Fundamental limits on the antenna directivity dictate that the maximum directivity which can be achieved for this structure would be limited by the overall size of the grid, i.e., if the physical area of the aperture is A, then Dmax = 4 piA/lambda2. Therefore, in order to increase the directivity even more, the grid size needs to be increased. In our simulations, an 11 x 11 grid showed the most gain, having over 17 dBi. This structure is shown in Fig. 1. Beyond this size, the patch can no longer efficiently illuminate the grid. If the grid size needs to be increased further in order to increase the gain, one might ask why we simply do not just use an array of patches. The answer lies in the high loss of the substrate at millimeter-wave frequencies. A microstrip array of patch antennas would employ some type of feed network, which becomes very lossy with increasing array size. As a result, large patch arrays are generally not desirable at millimeter-wave frequencies.

Invited paper - hybrid simulation of electrically large millimeter-wave antennas

This paper describes the simulation of an electrically large parabolic antenna fed by a horn antenna at millimeter-wave frequencies. Due to the fact that the feed needs to be simulated using a highly accurate simulation method, while the parabolic dish can be simulated with a physical optics approximation, a hybrid approach is needed. This paper describes a comparison of different approaches using a commercially available tool which makes use of a hybrid simulation approach. Time saving approaches is described, as well as methods to easily simulate variations in the design.

High data rate modulation issues in metamaterial-based antenna

This paper investigates the challenges related to using metamaterial structures for high data rate applications. In particular, the time domain effects are considered. The responses of these structures have time delay effects which tend to distort any high data rate signal that interacts with them, and which cause a time-dependent radiation pattern to be observed. The impacts of these effects on an artificial magnetic conductor (AMC) and a zero-n metamaterial antenna system are investigated.

High frequency broadband communications

The 60 GHz band has emerged as an international spectrum opportunity for short-range wireless communication networks. In this paper, technology trends that can impact the commercial deployment of systems utilizing millimeter-wave frequency bands are discussed. Millimeter-wave frequency bands have historically been costly to utilize and traditionally used almost exclusively for government and non-consumer products. Recent and ongoing advances in semiconductor technology and low cost high frequency packaging can be leveraged for low cost solutions that enable widespread deployment. An example of such a system operating in the millimeter-wave spectrum where bandwidths of ~3 GHz have been achieved. Multi-gigabit data transmission and reception over significant distances has also been realized to demonstrate the potential throughput of such a broadband wireless system.

Performance of GaAs on silicon power amplifier for wireless handset applications

Recently RF devices formed by the epitaxial growth of GaAs on a Si substrate have been demonstrated. The RF performance of these new devices compares well with devices on a conventional GaAs substrate process. This new GaAs-on-Si technology has the potential for replacing expensive RF components such as power amplifiers with lower cost devices fabricated on GaAs-on-Si while still maintaining good DC-RF performance. This paper presents the RF performance of these GaAs/STO/Si devices and shows for the first time their viability as power amplifiers in wireless handsets.