Continue reading Buckeyes embed antennas in clothes, couture to improve radio reception?
Buckeyes embed antennas in clothes, couture to improve radio reception? originally appeared on Engadget on Tue, 23 Aug 2011 12:12:00 EDT. Please see our terms for use of feeds.
Permalink | | Email this | CommentsGenerating precise and reliable true time delays (TTDs) is of paramount importance for phased array radars and a host of other applications. True time delay avoids beam squint in wideband antenna systems. Researchers at The Ohio State University have developed a free-space optical TTD device that can provide many bits of delay (more than 15 bits) for hundreds of antenna elements in ultra-compact form (half a cubic foot) with delays varying from femtoseconds to tens of nanoseconds. The invention uses a single MEMS chip, free space for massive overlapping of beam space, and a handful of mirrors. A programmable tapped delay line has many other uses, including optical correlation, optical matched filtering, optical signal processing, optical code-division multiple access coding and decoding, photonic analog-to-digital conversion, and optical communications performance monitoring. A variation of the device can also be used for optical interconnections and routers. Electronically implementing TTDs is generally impractical because of the need for many long lengths of strip line, waveguides, or coaxial cable, which are expensive, bulky, and temperature sensitive. Since long path lengths are relatively easy to obtain optically, optical TTD systems have been developed, either using fibers or free-space paths, but these existing systems are expensive and bulky due to the use of multiple optical switches. Researchers at The Ohio State University have developed a free-space optical TTD device that uses only one optical switch or spatial light modulator for the entire system instead of one or more switches for each bit, as in previous systems. Furthermore, the device avoids beam-spreading problems that may be present in other free-space systems by using a multiple-pass optical cell with refocusing mirrors. As a result, the device is more inexpensive, compact, and temperature insensitive than existing devices.
There is great commercial interest for antennas that can operate over large frequency bands. This is especially true for electrically small antennas (small in terms of wavelength). Designing effective, wide bandwidth, electrically small antennas is one of the most challenging problems in antenna engineering. Researchers at the Ohio State University have invented a method for appropriately loading the antenna at various locations along the structure with reactive elements (capacitors and inductors) which can have negative values (non-Foster elements) and can greatly increase the bandwidth of the antenna by controlling its currents. This concept is more general than previously reported methods based on the design of matching networks, which are based on the current and voltage behavior at the antenna terminals only. In contrast, this invention deals with currents throughout the entire antenna structure and results in an antenna with a simple and small form factor, ideal for miniature or portable electronics that require a small footprint.
Dr. Eric Walton of the ElectroScience Laboratory at The Ohio State University has developed a way to connect an on-glass antenna to a transmission cable that overcomes impedance matching problems in the AM and FM bands. Impedance matching for on-glass antennas is a challenge since in the FM frequency band coaxial cable impedance is often 50 ohms, and in the much lower AM frequency band the antenna and the receiver input impedance is much closer to 6,000 ohms. This invention results in a wide bandwidth and a transformation from the coaxial cable impedance to the antenna impedance. The matching circuit is especially designed to be imbedded in a small window attachment clip. This invention would be particularly suited for use in automobiles where the rear window heater grid can also function as an antenna, and consequently is essential along with another of Dr. Walton’s inventions which is described in U.S. Patent #5,781,160 (OSU Reference #94048). It should be noted, however, that this method is applicable in other on-glass wideband antenna configurations where impedance matching in the AM and FM bands must be achieved.
Dr. Eric Walton of the ElectroScience Laboratory at The Ohio State University has developed an automotive antenna that is effectively incorporated into the resistive, conductive heating elements found in automotive windows. The automobile industry has long recognized the advantages of forming an antenna in a vehicle window by imbedding conductors in the window glass. Manufacturers have also recognized that such windows can be defogged or defrosted by distributing resistive conductors over a major portion of the window area (the familiar heater grid found on the rear window of automobiles). It has been realized that the same conductors may be used for both heating the window area and as the communications antenna. The challenge lies in that the heater power source must be isolated from radio frequency signals in order to prevent RF currents from being shorted through the vehicle or heater power system. Previous attempts at isolation have been successful but have resulted in the need for heavy, expensive components and the need for separate antennas for different frequency bands. Dr. Walton’s design allows for optimal AM/FM reception (or the reception of other relatively low and high frequency bands found in modern wireless communication) and impedance matching using a single antenna, whereas previous designs required the use of two separate, different antennas. The design further allows for an apparatus with reduced size, weight, and cost as compared to previous methods. When coupled with U.S. Patents #6,320,558 and #6,483,468 (On-Glass Impedance Matching Antenna Connector, Reference #99062), impedance matching in the AM and FM bands can be easily achieved and a complete on-glass automotive AM/FM antenna/heater grid configuration realized.
Researchers at the ElectroScience Laboratory at The Ohio State University, in cooperation with an Italian automotive antenna manufacturer, have developed an improved wire pattern layout for an automotive window antenna. Automobiles traditionally have heating elements printed on the rear window for defrosting/defogging purposes, and such elements usually cover the majority of the window in order to defrost the entire area. This leaves little room for an isolated RF antenna on the window, and as a result the smaller antenna geometry results in relatively poor performance. This invention alleviates this problem by incorporating the RF antenna into the heater grid configuration, while taking into account the effects of the heater grid pattern and the general characteristics of RF current throughout the circuit. The result is a rear window antenna with improved performance that is seamlessly and attractively integrated into the already existing heater grid configuration.