The above and other objects and advantages of the present invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which:
The present invention will be explained with reference to
As shown, antenna 100 comprises a feed trace 104, a short trace 106, patch 108, and support substrate 110. Substrate 110 provides support for antenna 100 to facilitate patch 108 residing perpendicular or substantially perpendicular to ground plane 102. Substrate 110 is optional, however, and can be removed. When used, substrate 110 may be comprised of a number of materials, but it has been found using printed circuit board material is satisfactory. Moreover, increasing the dielectric constant of substrate 110 generally reduces the size of antenna 100, but also generally reduces the efficiency and bandwidth of the antenna as well.
As shown, patch 108 has eight equal length sides 112, forming a octagonal shape similar to a conventional stop sign. The junction 116 between two sides can be sharp (as shown, or curved or beveled as desired. While shown as having equal length sides 112, the sides may have differing lengths. For example, sides 112L and 112R may be significantly longer than sides 112LT, 112RT, etc. Moreover, changing the side lengths provides a tuning function for antenna 100. Bandwidth at any tuned frequency is dependent, in part, of the shape of antenna 100, which is dependent, in part, on the side lengths. While shown as having an octagonal shape, the shape of patch 108 may be any polygon shape.
Feed trace 104 and short trace 106 reside on side 112B (sometimes referred to as a bottom edge) closest to ground plane 102. Either or both of feed trace 104 and short trace 106 may be connected to other sides, such as, for example, short trace 106 may connect to side 112RB or 112R. The length of feed trace 104 and/or short trace 106 provides a tuning feature. Moreover, a longer short trace 106 generally reduces the resonant frequency of antenna 100. A gap G exists between side 112B and ground plane 102. Gap G is somewhat dependent on the tuned resonant frequency.
Feed trace 104 and short trace 106 are separated by a distance D. Varying distance D provides impedance matching making it unnecessary to have a separate matching circuit. However, a matching circuit may be used.
Short trace 106 is useful in tuning antenna 100. Varying the a width WS of short trace 106 allows the operating frequency of antenna 100 to be tuned.
While not shown, antenna 100 may have a slot. The slot tends to lower the resonant frequency, although it is believed the slot would have to extend/terminate on a side. Also, parasitic elements, such as parasitic element 200 (shown only in
While the invention has been particularly shown and described with reference to one or more embodiments thereof, it will be understood by those skilled in the art that various other changes in the form and details may be made without departing from the spirit and scope of the invention.