Wideband compact planar inverted-F antenna

Abstract

An improved low profile antenna of the PIPAPIFA style is formed from a single piece of useful conductive material and includes a first plate spaced apart from an elongated ground plate. The first and ground plates are interconnected by a shorting plate having a width less than that of either the first or ground plate. A feed plate is interposed between the two plates and is either completely covered by the first plate or slightly exposed. Such antennas have extremely large bandwidth of up to about 50%.

Description

[0001]This application is a 371 of PCT / US01 / 13603 filed Apr. 27, 2001 which claims benefit of Ser. No. 60 / 200,009 filed Apr. 27, 2000.BACKGROUND OF THE INVENTION[0002]The present invention relates generally to planar inverted-F antennas, and more particularly to such an antenna with improved performance characteristics that is particularly suitable for use in wireless telephones.[0003]The wireless communication industry has expanded rapidly and many different frequency bands have been implemented. A need exists for wireless devices that operate in multi-frequency bands. Dual band antennas have been used to meet this need, however, many dual band antennas use a dual feed which introduces difficulties into the feed system. Dual band antennas permit wireless handsets to operate in different networks that have different frequencies. There are more than three frequency bands used in the world for wireless communications. It is possible, but expensive to place multiple antennas on handset...

AI Technical Summary

Benefits of technology

[0009]It is therefore a general object of the present invention to provide a low profile, PIFA-style antenna in use with wireless handsets that has improved performance characteristics, such as improved bandwidth.

[0012]Still another object of the present invention is to provide a low profile, planar inverted-F antenna for use in wireless applications that includes an integrated ground plane and has an increased bandwidth.

[0013]The present invention achieves these and other objects by way of novel and unique structure. In accordance with one principal aspect of the present invention, a PIFA is provided that includes a conductive radiating element in the form of a plate, an elongated ground plate spaced apart from and underneath the radiating element, short circuit plate interconnecting the radiating element to the ground plate and a feed plate interposed. In this manner, the ground plate is formed as part of the entire antenna structure, thereby eliminating the need to use a different conducting plane, such as a metal housing of the handset to perform the grounding function and reduce the overall size of the handset.

[0014]In another important aspect of the present invention and as exemplified by another embodiment thereof, the feed plate and radiating element are dimensioned so that the feed plate is completely shielded by the radiating-element so as to prevent the feed plate from radiating, so as to eliminate undesirable variations in antenna radiating pattern and control of the resonant frequency. As a result, the ground plate becomes the main radiating element, and by dimensioning the first and feed plates, the bandwidth of the antenna can be significantly increased to about 50%.

Problems solved by technology

Dual band antennas have been used to meet this need, however, many dual band antennas use a dual feed which introduces difficulties into the feed system.

It is possible, but expensive to place multiple antennas on handsets and it also increases the complexity of the handset.

This parameter of bandwidth is limited in most applications by the need to match the impedance of the antenna to the system with which it is used.

This structure has its own disadvantages, one of which is that it utilizes the casing of the telephone handset as a ground plane and the other of which is that even with its low profile and capacitive feed, its achieved bandwidth is only about 5% at a VSWR (Voltage Standing Wave Ratio) of 2 or less.

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