Patent Application
20080160851
The present invention is directed to textiles having a high impedance surface. More particularly, the present invention is directed to wearable and portable textiles having conductive matter that, at least in part, defines the high impedance surface.
A conventional ground plane must be placed a quarter wavelength away from an associated antenna to avoid having its image currents cancel the currents in the antenna, which would result in poor radiation efficiency. Conventional flat metal ground planes also support the propagation of surface waves, which cause multipath interference and backward radiation.
Some conventional high impedance antenna surfaces have been designed to address some of these shortcomings of conventional ground planes. Some high impedance surfaces are fabricated as printed circuit boards. A series of U.S. patents to Sievenpiper, the most recent being U.S. Pat. No. 6,739,028, describe a high impedance surface comprising one or more layers of periodic arrays of flat plates. Each plate may be connected to a backside ground plane by one or more conductive posts. Because the image currents of the board are not phase reversed, the high impedance surface can be placed directly against an antenna.
The conventional high impedance antenna surfaces used for many telecommunications applications require a relatively large area, especially for frequencies below 10 GHz as used in many cellular, two-way radio, and satellite communications systems. This large area requirement is directly contrary to the present-day desire to reduce the size of personal communications devices and other personal electronics.
It may be desirable to provide a textile having a high impedance antenna surface, where the textile is a woven, non-woven, knitted, felted, or foamed material that can be fabricated into a wearable garment or portable article. It may be desirable to exploit the substantial surface area of a wearable garment or portable article while not being restricted by the flexibility, durability, and launderability of the garment or article.
According to various aspects of the disclosure, a textile may include conductive matter and a high impedance surface defined at least in part by the conductive matter.
In accordance with some aspects of the disclosure, a textile having a high impedance antenna surface may comprise a conductive fabric ground plane, one or more layers of conductive fabric plate arrays, and one or more non-conductive fabric layers interleaved between the conductive fabric ground plane and the one or more layers of conductive fabric plate arrays.
In various aspects of the disclosure, a textile may comprise a high impedance surface and an antenna mounted on the high impedance surface.
An exemplary embodiment of a textile 100 having a high impedance surface 102 is illustrated in
According to various aspects, the high impedance surface 102 may be defined at least in part by conductive matter. As described in more detail below, the conductive matter may comprise conductive thread, a conductive fabric, or a conductive paste.
As shown in
In one exemplary aspect, as shown in
Referring to
Referring now to
It should be appreciated that the textile 100 may optionally include one or more vias 134 formed by conductive thread stitched to the ground plane 110 and the conductive matter of the conductive fabric plates 116 described above (vias are shown only in
In some aspects, the first and second layers may comprise arrays of square or rectangular plates. With squares or rectangles, the offset would typically cause each square or rectangle to partially overlap four squares or rectangles of the other layer. It should be appreciated that a textile may comprise more than two layers of conductive fabric plate arrays. Regardless of the number of layers of conductive fabric plate arrays, the layers are electrically isolated from each other.
According to some aspects, the layers of conductive fabric plate arrays may be electrically isolated, for example, by interleaving or sandwiching a second non-conductive center between them. Alternatively, the conductive fabric plate arrays may be electrically isolated from each other by the non-conductive fabric on which they are directly formed, as in the embodiment of
A person skilled in the art will appreciate that a high impedance surface comprising a single layer of plates depends upon the fringing capacitance between plates lying in the same plan, i.e., the edge-to-edge capacitance. A high impedance surface with a second, offset layer of plates provides parallel plate series capacitance between the plates of the first layer. This parallel plate series capacitance is typically substantially greater in magnitude that the fringing capacitance of the single-layer construction, thereby reducing the resonant frequency of the high impedance surface.
As shown in
The textile 100 may comprise an interface configured to interconnect the antenna 150 with an electronics assembly 162. The electronics assembly 162 may be held by a user or stowed in a pocket of the textile 100 or some other worn or carried article, or it may be partially or fully integrated into the worn or carried article. According to various aspects, the electronics assembly may comprise a cellular telephone or smartphone, a two-way radio, a satellite communication device, a personal information device or personal digital assistant, or any other personal communication device.
The textile 100 with high impedance surface 102 can be placed directly against the antenna 150 because there is no phase reversal that is typical of a normal ground plane. Although the proximity of a mounted antenna to the body changes as the user moves, the high impedance surface 102 may also prevent detuning of antennas caused by the body of a user. Thus, the textile 100 and a low profile antenna 150 accommodate the desire for small form factor communications products, while taking advantage of the huge surface area provided by a garment or other fabric structure in comparison with the size of typical portable electronics housings.
It should be appreciated that the high impedance surface 102 of the textile 100 may suppress surface waves of any antenna on the textile. Accordingly, a plurality of antennas may be mounted on the high impedance surface 102 without causing mutual interference problems. The suppression of surface waves may also improve the performance of patch antennas.
It will be apparent to those skilled in the art that various modifications and variations can be made in the devices and methods of the present disclosure without departing from the scope of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only.
