|Publication number||USRE42672 E1|
|Application number||US 11/516,804|
|Publication date||Sep 6, 2011|
|Filing date||Apr 27, 2001|
|Priority date||Apr 27, 2000|
|Also published as||US6795028, US20040125025, WO2001082412A2, WO2001082412A3|
|Publication number||11516804, 516804, PCT/2001/13603, PCT/US/1/013603, PCT/US/1/13603, PCT/US/2001/013603, PCT/US/2001/13603, PCT/US1/013603, PCT/US1/13603, PCT/US1013603, PCT/US113603, PCT/US2001/013603, PCT/US2001/13603, PCT/US2001013603, PCT/US200113603, US RE42672 E1, US RE42672E1, US-E1-RE42672, USRE42672 E1, USRE42672E1|
|Inventors||Warren L. Stutzman, Minh-Chau Huynh|
|Original Assignee||Virginia Tech Intellectual Properties, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (13), Classifications (15), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
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.
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.
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 handsets and it also increases the complexity of the handset.
The use of wireless (cellular) telephones is very widespread. Not only has the size of wireless telephones decreased in the past few years, but the functional capabilities of such telephones have increased as well. Some of these wireless telephones are smaller than the palm of a user. In order to operate effectively and to deliver the needed functionability required of today's wireless technology, a useful and reliable antenna must be utilized. Planar inverted-F antennas, also known by the acronym “PIFA” have been popular and used in wireless devices such as handheld telephones because a PIFA has a low profile geometry and it does not extends out of the telephone as do most monopole stubby antennas used in current wireless handheld devices.
Notwithstanding the size advantages, many low profile antennas in use today have a narrow bandwidth. 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. Conventional PIFAs, such as that described in U.S. Pat. No. 5,764,190, issued June 1998, have large resonant frequencies of 1.58 to about 1.78 GHz but with a bandwidth of about only 5% of the resonant frequency. This is usually referenced by a 2:1 VSWR into a 50 ohm load. 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.
A number of telephones are described in the literature in broadening bandwidth. These techniques include the use of a parasitic structure with a resonant frequency near that of the during antenna structure. Another is the use of a stacked microstrip patch antenna described in the articles “Broadband Air-Filled, Stacked U-Slot Shorted Patch Antenna” in Electronic Letters No. 35, Pages 515-517 (1999) or in “Design Probe-fed Stacked Patches” in IEEE Transactions on Antennas and Propagation, Vol. 47, No. 12, Pages 1780-1784, December 1999.
There are new frequencies of wireless communication proposed for a high end of frequencies in the 34 Hz range. This is known as the UMTS band and will increase the frequency bandwidth to about 23% to encompass the most used frequency bands.
A need therefore exists for a low profile antenna that has a greater bandwidth than 5% to utilize most, if not all of current and proposed wireless frequency bands, but which still maintains a desirable small size. The present invention is directed to a low profile antenna that overcomes the aforementioned disadvantages.
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.
Another object of the present invention is to provide a PIFA that utilizes its own ground plane, rather then that of a wireless handset casing and which utilizes a capacitive feed with a small ground plane.
Yet another object of the present invention is to provide an improved PIFA for use with wireless handsets, the PIFA including a first conductive plate that serves as a ground plate, a second conductive plate overlying the first plate and having a length much less than the first plate, a short circuit plate connecting these two plates together and a feed plate interposed between the first and ground plate, the feed plate being connected to the transmitter/receiver of the wireless handset.
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.
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.
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%.
These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detailed description.
In the course of this detailed description, the reference will be frequently made to the attached drawings in which:
A conductive, non-contacting feed is provided for the antenna 20 by terminating the inner conductor 31 of an RF connector 30 to a fourth conductive plate 28, that acts as a feed plate for the system. The inner conductor 31 passes through the ground plate 24 and into contact with the feed plate 2B 28, while the outer conductor 32, i.e., the casing, of the RF connector is terminated to the ground plate. This feed plate 28 preferably has the same width W (
Additionally, it is desired in this embodiment that first plate 22 entirely cover the feed plate 28, that is, it shields (using the non-electrical definition of “shield”) or shrouds the feed plate 28 in the horizontal plane in which the first plate 22 extends. These two relationships constitute to the improved operation. The literature indicates that the use of a PIFA-style antenna with a large, but distinct ground plane, as evidenced by the above-mentioned U.S. Pat. No. 5,764,190, has a limited band width that ranges from between about 5% to about 10%. This small band width is a disadvantage present in the prior art PIFA-style antennas.
We have discovered that the structure of this invention overcomes these disadvantages and such antennas provide a 400 to 500% increase over the bandwidth available in the prior art. An antenna 20 of the configuration shown in
The results of both the simulation and testing are illustrated in graph of
As for the size of the antennas of the invention, it is commonly known that the “size” of an antenna is measured by the radius of an imaginary sphere that just reduces the antenna and the “size” referred to above is the electrical size which is the principal size relative to a free space wavelength λ and is expressed in units of wavelength. In this regard, the size of the ground plates of the antennas of the invention are small, in the range of 0.4λ, which is greatly different than the large ground plane required for a conventional PIFA-style antenna of the type described in U.S. Pat. No. 5,764,190.
Due to the small dimensions of the antennas of the invention that approximate between about 2 inches to about 2½ inches long, about ⅜ inches wide and about ¼ inches high, it is preferred that the antenna be formed from a single piece of conductive material. However, in some applications it is contemplated that the plates may be assessed together by welding, although it will be understood that the single piece construction is preferable.
In the antenna of
This slight offset of the first plate 102 that exposes an edge of the feed plate 108 in combination with the length of the ground plate 104 maintains the desired small size of the antenna 100 and provides an even larger bandwidth than that provided by the first embodiment antenna 20, about 49%, which is about 5 times more than that obtained by the antenna described in U.S. Pat. No. 5,764,190.
In this antenna embodiment 100, the first plate length L1 has about 46% of the length of the ground plate length, L2, while in the first antenna embodiment 20, the first plate length L1 has about 40% of the length of the ground plate length L2. While all the operating bases for the present invention are not yet known, it is believed that the first plate should have a length that is between about 38% to 50% that of the ground plate length. Similarly, the length of the feed plate 108 is about 86% of the length of the first plate 102 and the feed plate 108 should have a length that is between about 80% to about 90% of the length of the first plate 102. The width of the shorting plate in this antenna is about 32% of the width of the first and ground plates. It is believed that the width of the shorting plate affects the operation of the invention and that the shorting plate should be between about 20% to about 40% of the widths of the first and ground plates.
It will be understood that the antennas of the invention offer significant improvement in performance over those in use of the prior art. The wide bandwidth of the antennas of the invention is important not only because their reduced size permits them to be inserted into palm-sized devices, but also permits the devices on which the antennas are used to be operational in different wireless systems using only a single feed. For example, the DCS-1800 wireless system uses a frequency band of 1710-1880 MHz, the PCS-1900 communications system uses a frequency band of 1850-1990 MHz, the IMT-2000 uses a frequency band of 1888-2200 MHz, the ISM (and including WLAN) uses a frequency band of 2400-2483 MHz, while the promising Bluetooth system uses the frequency band of 2400-2500 MHz. These five frequency bands are illustrated on
Additionally, the polarization of the antennas of the invention occurs along these lengths shown as L in
While the preferred embodiment of the invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the appended claims.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US4641366||Oct 3, 1985||Feb 3, 1987||Nec Corporation||Portable radio communication apparatus comprising an antenna member for a broad-band signal|
|US5148181||Dec 10, 1990||Sep 15, 1992||Nec Corporation||Mobile radio communication apparatus|
|US5231407 *||Jun 25, 1991||Jul 27, 1993||Novatel Communications, Ltd.||Duplexing antenna for portable radio transceiver|
|US5644319||May 31, 1995||Jul 1, 1997||Industrial Technology Research Institute||Multi-resonance horizontal-U shaped antenna|
|US5764190||Jul 15, 1996||Jun 9, 1998||The Hong Kong University Of Science & Technology||Capacitively loaded PIFA|
|US5781158||Jul 30, 1996||Jul 14, 1998||Young Hoek Ko||Electric/magnetic microstrip antenna|
|US6342860||Feb 9, 2001||Jan 29, 2002||Centurion Wireless Technologies||Micro-internal antenna|
|US6483463 *||Mar 27, 2001||Nov 19, 2002||Centurion Wireless Technologies, Inc.||Diversity antenna system including two planar inverted F antennas|
|US6573869 *||Mar 21, 2001||Jun 3, 2003||Amphenol - T&M Antennas||Multiband PIFA antenna for portable devices|
|US6593888||Dec 10, 2001||Jul 15, 2003||Z-Com, Inc.||Inverted-F antenna|
|US6683575||Jul 5, 2002||Jan 27, 2004||Kabushiki Kaisha Toshiba||Antenna apparatus|
|US6734825 *||Oct 28, 2002||May 11, 2004||The National University Of Singapore||Miniature built-in multiple frequency band antenna|
|US7046196 *||Sep 29, 2000||May 16, 2006||Harada Industry Co., Ltd.||Dual-band microstrip antenna|
|U.S. Classification||343/702, 343/700.0MS|
|International Classification||H01Q5/00, H01Q1/24, H01Q9/04|
|Cooperative Classification||H01Q9/045, H01Q5/378, H01Q5/357, H01Q9/0414, H01Q9/0421|
|European Classification||H01Q9/04B5, H01Q9/04B1, H01Q9/04B2, H01Q5/00K4, H01Q5/00K2C4|
|Jan 7, 2011||AS||Assignment|
Owner name: VIRGINIA TECH INTELLECTUAL PROPERTIES, INC., VIRGI
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:VIRGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSITY;REEL/FRAME:025599/0560
Effective date: 20030428
Owner name: VIRIGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSI
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:STUTZMAN, WARREN L.;HUYNH, MINH-CHOU;REEL/FRAME:025599/0546
Effective date: 20030418
|Feb 24, 2012||FPAY||Fee payment|
Year of fee payment: 8
|Mar 13, 2012||CC||Certificate of correction|
|Feb 23, 2016||FPAY||Fee payment|
Year of fee payment: 12