Barcodes have become a common and useful tool for identifying products, parts, prices, serial numbers, and many other bits of data. Over the years many different barcodes have been used, including the UPC codes found in grocery stores and the Code 39 barcodes used for many non-grocery items. These different barcodes are substantially only alternative ways of encoding information. For example, a narrow bar or space might represent a 0 while a wide bar or space might represent a 1, or a long bar might represent a 0 while a short bar might represent a 1.
Barcodes can differ on how they are sensed. Light, usually in the form of a scanning laser beam, or magnetic energy are commonly used to sense barcodes. A problem with light operated barcodes is that the barcode can become obscured, either with contaminates such as dirt or smudged ink, or by an opaque obstruction, such as a barcode-containing document being inside an envelope or under another document. Another manner of sensing barcodes is through magnetics. Magnetic barcodes generally require careful, close placement of a magnetic barcode reader relative to the barcode itself, which is often a difficult task.
Thus, barcodes sensed by light cannot be placed where they cannot be scanned by a scanning light beam. For example, they cannot be placed on objects within envelopes, and they cannot be embedded beneath the surface of an object such as paper currency. While it might be possible to accomplish this objective with magnetic barcodes, technical consideration make it a complex task.
Therefore, a barcode system that permits reading a barcode even when embedded beneath a surface, or placed within opaque materials such as an envelope, and not requiring highly accurate placement of the barcode reader relative to the barcode would be beneficial. Even more beneficial would be a barcode system which is of a small size and which permits for multiple barcodes at a single physical location.
The present invention is directed to a microwave barcode system wherein the barcode comprises a plurality of conductive wires, consisting of a plurality of lengths, mounted on a surface of an object, or embedded beneath the surface of the object. A transmitter, comprising a dipole antenna, radiates microwave signals in the direction of the surface. A microwave reader, comprising a dipole antenna, positioned to receive the microwave signals passing through the surface, and senses an attenuation of the microwave signal caused by a resonant interaction between the microwave signals and the conductive wires.
The conductive wires of the present invention can be mounted in a standup fashion, wherein each wire is mounted adjacent to and parallel to, but not touching, its at least one neighbor, and/or in a lay-down fashion, wherein each wire is mounted coincident with an imaginary line which is also coincident with the remaining wires, and wherein the wires are mounted end-to-end with a gap surrounding each wire end. Because a microwave reader positioned to read a stand-up barcode cannot detect signals polarized for a lay-down barcode, and a reader positioned to read a lay-down barcode cannot detect signals polarized for a stand-up barcode, both stand-up and lay-down versions of the barcode may be employed simultaneously at a single physical location.