Patent Application
20100199903
This invention relates to methods of constructing radio frequency antennas, transmission lines and other structures such as filters.
In many radar and communications systems, it is desirable to employ an antenna or transmission line that is lightweight and flexible. For example, an antenna may be incorporated into a fabric structure such as a garment or a tent. In other applications, an antenna may be incorporated into a composite laminate. This laminate is first comprised of a reinforcement fabric which is then impregnated with a resin. This prepreg structure is often merged with other prepreg structures and then cured to produce a final assembly. Prior to merging and curing, it is desirable to incorporate said antenna structures into the laminate reinforcement fabric and thereby obtain a durable, low cost, integrated antenna structure.
In the past, several methods of constructing radio frequency structures from textile materials have been proposed. See “Method for constructing microwave antennas from textile fabrics and components”, Provisional Patent Application, U.S. application Ser. No. 60/557,431, Mar. 29, 2004 and “The Characterization of Conductive Textile Materials Intended for Radio Frequency Applications”, Robert K. Shaw, et. al., IEEE Antennas and Propagation Magazine, Vol. 49, No. 3, June 2007, pp. 28-40. Structures have been built using conductive foil or fabric attached to a laminate or conductive ink printed onto a laminate. However, under fatigue stress, such embedded radio frequency (RF) structures can cause delamination.
Also in the past, methods of incorporating conductive fibers into reinforcement fabric by direct stitching of said fiber have resulted in undesirable radio frequency losses due to propagation disturbances. The inventors have tried that method and the data for that method is included in
It is therefore the object of this invention to provide methods of constructing RF structures by attaching conductive fiber to the reinforcement fabrics of composite laminates.
It is a further object of this invention to provide a means of constructing RF structures by attaching conductive fiber to the surface of fabric structures so that propagation losses are reduced.
It is another object of this invention to provide a means of construction of microwave antennas on a reinforcing fabric for later incorporation into laminated structures.
It is another object of this invention to provide a means of constructing RF structures and to incorporate said structures into clothing in a way that allows said RF structures to look like fashion designs or appliques.
It is the realization of these-objects that an RF structure can be incorporated into ordinary fabrics, non-woven fabrics and even clothing so that said RF structures are flexible, not subject to delamination and the basic structure can also be incorporated in to laminate prepeg structures for other applications.
This invention features conductive fiber such as copper wire, stainless steel wire or other conductive fibers that is attached to fabric such as composite laminate reinforcement fabric by means of zigzag overstitching. This overstitching is accomplished by use of cording embroidery and can be implemented with, for example, Schiffley or Cornelly Embroidery machine or with cording attachments to lock-stitch embroidery machines or by other similar means. It is important that the fibers be attached onto the reinforcing fabric as opposed to being stitched through said fabric as stitching through the fabric diminishes the microwave properties of the antenna.
Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings in which:
There is shown in
