Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2002-07-24
2003-12-30
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S702000, C343S847000, C343S893000
Reexamination Certificate
active
06670923
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to antennas, and more specifically to antennas for use within handheld or portable wireless communication devices or handsets.
2. Description of the Related Art
State of the art cellular communication systems generally require handsets that provide both a multi-band and a multi-system capability. That is, there is a growing need for multi-purpose cellular handsets that can be utilized in cellular applications such as Advanced-Mobile-Phone-Service (AMPS), Personal-Communications-Service (PCS), Global-System-For-Mobile-Communication (GSM), Distributed-Communications-System (DCS) and Industrial Scientific Medical (ISM), and that can also be utilized in non cellular applications such as Global-Positioning-System (GPS) and Bluetooth (BT) (Bluetooth is the code name for an open specification to standardize data synchronization between disparate personal computer and handheld personal computer devices).
Current advances in cellular communication technology also provide an emphasis on providing an antenna that is internal to a cellular handset, to thereby utilize the inherent advantages that are provided by such an antenna that is buried with the wireless communication device.
The structure and arrangement that is provided by the present invention includes a planar inverted-F antenna (PIFA).
A PIFA is a compact, low profile, microstrip antenna, and it is called an inverted-F antenna because a side view of the antenna resembles the letter F facing down. U.S. Pat. Nos. 6,072,434, 6,218,991 and 6,222,496, incorporated herein by reference, are examples of PIFAs.
Multi-Band PIFAs are of interest to the mobile wireless communication industry. In a multi-band PIFA a choice between providing a single antenna feed, or providing multiple antenna feeds, tends to be dependent on system requirements. However, from the standpoint of antenna design, the choice between providing a single antenna feed or multiple antenna feeds has both merits and demerits.
In a single antenna feed, multi-band, PIFA providing a required bandwidth at multiple resonant frequencies generally leads to antenna design complexities.
On the other hand, a multi-band PIFA having multiple antenna feeds tends to diminish antenna design complexities since the design of a plurality of individual radiating/receiving elements, each having a separate feed, tends to be less difficult. However, multiple antenna feeds encounter the problem of mutual coupling between the individual radiating/receiving elements of a multi-band. PIFA. There is also a concern that a multi-band PIFA with multiple antenna feed ports may have its performance compromised due to mutual coupling and poor isolation between the PIFA's various resonant bands.
Hence, in spite of the reduced design complexities that are provided by a multi-band PIFA having multiple feeds, such a PIFA has not been a choice for practical applications, mainly due to the mutual coupling problem. In view of this, techniques that reduce the mutual coupling between the individual radiating/receiving elements of such as multi-band PIFA are important.
Past research on dual-feed, dual-band, PIFAs has emphasized optimizing the PIFA for cellular applications. However, most of the prior art dual-feed, dual-band, PIFAs exhibit an isolation of only about 15 dB.
Further improvement in the isolation that is provided by a dual-feed. dual-band, PIFA has been realized by increasing the physical separation between the antenna's multiple radiating/receiving elements. However, such an option contradicts the desirable requirement that the overall physical volume that is occupied by the PIFA be small.
Therefore, techniques which accomplish the desired objective of improved isolation without increasing the overall volume and/or linear dimensions of a multi-band PIFA are needed by the art.
The design and application of a dual-feed, dual-band, PIFA for cellular or mobile communication have been dealt with in the following publications, wherein the publications generally deal with the design of PIFA for cellular bands such as the AMPS/PCS or GSM/DCS bands.
[1] Z. D. Liu, P. S. Hall and D. Wake, “Dual-Frequency Planar Inverted-F Antenna”, IEEE Trans. Antennas and Propagation Vol. AP-45, No. 10, pp. 1451-1458, October 1997.
[2] C. B. Rowelland R. D. Murch,“A Compact PIFA Suitable for Dual-frequency 900/1800—MHz Operation”, IEEE Trans. Antennas and Propagation Vol. AP-46, No. 10, pp.596-598, April 1998.
[3] P. Kabacik and A. A. Kucharski,“Optimizing the radiation Pattern Of Dual Frequency Inverted F Planar antennas”, JINA conference, pp.655-658, 1998.
[4] P. Song, P. S. Hall, H. Ghafouri-Shiraz and D. Wake, “Triple-Band Planar Inverted F Antenna”, IEEE-APS Symposium, 1999, Orlando, pp.908-911.
Above cited reference [1] discusses an achievable isolation between the two feed ports of a GSM/DCS band PIFA. Specifically, isolation between the two ports as reported in [1] is of the order of about 15 dB. Any improvement in the isolation, while maintaining the overall volume of the PIFA, is at the expense of gain at one of the antenna ports.
To the contrary, the present invention improves the isolation (18-19 dB) between the two feed ports of two-antenna assemblies that are constructed and arranged in accordance with the present invention, without degrading the gain at the individual antenna ports. Further, the present invention does not increase the overall physical volume that is occupied by the multi-band antenna structure.
The design of a GSM/DCS/ISM Tri Band PIFA with two and three feed ports is described in above cited reference [4]. In this reference, multiple antennas are each of the PIFA type with all of the radiating elements lying on a single surface that is parallel to a ground plane. Prior art
FIGS. 1-3
, discussed below, show this type of arrangement.
In an embodiment of the present invention a multi-band, two-antenna assembly or module provides a combination of a PIFA and an inverted-F antenna (IFA) whose radiating elements are located in an orthogonal orientation.
An IFA is also known as a shunt-driven inverted-L antenna transmission line having an open end. That is, an IFA is a version of an inverted-L antenna having with the freedom to tap the input along the antenna's horizontal wire in order to achieve a degree of control over the antenna's input impedance.
FIG. 1
is a top view of a prior-art multi-band PIFA
10
having multiple feeds.
FIG. 2
is a section view of PIFA
10
taken on line
2
—
2
of
FIG. 1
, and
FIG. 3
is a section view of PIFA
10
taken on line
3
—
3
of FIG.
1
. Multi-band PIFA
10
includes two separate feeds, one feed for each if its two frequency bands.
PIFA
10
includes radiating/receiving elements
11
and
12
that resonate at the two separate frequency-bands. Radiating/receiving elements
11
and
12
occupy a common plane, and they are positioned above and generally parallel to a ground plane element
13
. An L-shaped slot
14
provides both physical and electrical separation between the two radiating/receiving elements
11
and
12
.
A first hole
15
is provided in the relatively large area radiating/receiving element
11
, and a conductive feed pin
16
is inserted through hole
15
. Feed pin
16
is used to feed radio frequency (RF) power to radiating/receiving element
11
. Feed pin
16
is electrically insulated from ground plane element
13
at the location whereat feed pin
16
passes through a hole that is provided in ground plane element
13
.
A second hole
17
is provided in radiating/receiving element
11
. A conductive post
18
which functions as a short circuit between radiating/receiving element
11
and ground plane element
13
is inserted through hole
17
and through a hole that is provided in ground plane element
13
. Post
18
extends generally parallel to feed pin
16
.
Radiating/receiving element
11
, having the relatively larger dimensions of length (L
1
) and width (W
1
), reso
Kadambi Govind Rangaswamy
Stoiljkovic Vladimir
Suganthan Shanmuganathan
Centurion Wireless Technologies, Inc.
Chen Shih-Chao
Holland & Hart LLP
Wong Don
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