Patent Application
20090002248
This invention generally concerns antennas and, more specifically, concerns half- and quarter-wavelength printed slot ultra-wideband (“UWB”) antennas for use in mobile terminals.
Wireless multimedia systems are becoming increasingly popular. However, improvements are still needed in order to provide higher-data-rate communication links, for example, to efficiently transmit video signals. As a result, more attention is being directed to the development of ultra-wideband (“UWB”) communication systems. The UWB communication system is a short-range wireless technology, which is expected to play a role in scenarios where “everybody and everything” is connected by different types of communication links including human to human, human to machine, machine to human, and machine to machine. It is anticipated that the consumer electronics and personal computer industries soon will take advantage of UWB technology to transmit data, video and audio. This technology will also provide a clear added-value benefit to the mobile phone industry by developing UWB-equipped mobile devices.
In order to transmit and receive UWB signals, an effective UWB antenna is required. In the past, although different types of UWB antennas (such as, for example, 3-D cone and 2-D planar bow-tie antennas) have been proposed, these antennas have CONFIRMATION COPY not been suitable for mobile terminals as the size of these proposed UWB antennas is quite large. In fact, for a successful design of an UWB antenna, special requirements, such as compactness, low profile, and low cost, need to be met. This invention provides a suitable solution to meet the needs of mobile terminals.
Prior art examples of proposed UWB antenna designs for mobile terminals include “Novel Microstrip-Monopole-Integrated Ultra-Wideband Antenna for Mobile UWB Devices,” by Y. J. Wang, C. K. Lee, P. S. Tian, and S. W. Lee, 2003 Radio and Wireless Conference Proceedings, pp. 87-90. This design utilizes a microstrip-monopole integrated UWB antenna. In this design, however, the physical dimension of the UWB antenna is 40 mm×40 mm×15.5 mm, which is too large for modern mobile handsets. Other examples have utilized a printed slot antenna for wideband [Jia-Yi Sze, and Kin-Lu Wong, “Bandwidth Enhancement of a Microstrip-Line-Fed Printed Wide-Slot Antenna,” IEEE Transactions on Antennas and Propagations, vol. 49, No. 7, pp. 1020-1024, July 2001] and ultra-wideband [X. Qing, M. Y. W. Chia, X. Wu, “Wide-Slot Antenna for UWB Applications,” IEEE 2003 Antennas and Propagation Society International Symposium, vol. 1, pp. 834-837] operations. It is to be noted, however, that the size of the printed circuit board (“PCB”) used in the designs of the printed slot antenna for wideband and ultra-wideband operations were not related to the size of any actual mobile terminals, hence these designs cannot be directly used for mobile handsets. Additionally, the size of conventional slot antennas is based on half-wavelength designs.
The foregoing and other problems are overcome, and other advantages are realized, in accordance with the presently preferred embodiments of these teachings.
The present invention employs slot antennas integrated on a printed circuit board to make UWB antennas for mobile terminals. The slot antennas integrated on a PCB of a mobile terminal can be used as a UWB antenna.
An embodiment of the present invention employs a slot antenna to form an UWB antenna for a mobile terminal, including a half-wavelength slot UWB antenna and a quarter-wavelength slot UWB antenna. Embodiments in accordance with this invention can be used for mobile terminals to transmit and receive UWB signals in the frequency range of, for example, 3.0 GHz to 5.0 GHz.
A first alternate embodiment of the present invention comprises a half-wavelength slot antenna comprising: a dielectric substrate having a first side and a second side; an electrically conducting layer positioned on the first side of the dielectric substrate, wherein there is a rectangular slot in the electrically conducting layer exposing a portion of the first side of the dielectric substrate, and wherein the rectangular slot has at least a first side and a second side orthogonal to the first side; a feed line positioned on the second side of the dielectric substrate, wherein a centerline of the feed line extends parallel to the first side of the rectangular slot and wherein the feed line has proximal and distal ends, the distal end of the feed line extending just into a region on the second side of the dielectric substrate directly opposite the rectangular slot, bisecting the second side of the rectangular slot; a fork-shaped tuning stub positioned on the second side of the dielectric substrate directly opposite the rectangular slot of the first side, the fork-shaped tuning stub comprising a first branch extending transversely in either direction from the distal end of the feed line parallel to the second side of the rectangular slot, wherein the first branch has an intermediate point and two distal ends, the intermediate point of the first branch aligning with the distal end of the feed line, the fork-shaped tuning stub further comprising second branches extending transversely from the distal ends of the first branch parallel to the first side of the rectangular slot; and wherein the first side of the rectangular slot is about 10 mm and the second side of the rectangular slot is about 28 mm; the first branch has a length of about 18 mm, and wherein the half-wavelength antenna operates in the frequency range of about 3.1 GHz to 4.9 GHz.
In one variant of the first alternate embodiment, the half-wavelength antenna comprises a half-wavelength slot ultra wideband antenna.
In another variant of the first alternate embodiment, the feed line of the half-wavelength antenna comprises a microstrip line.
In a further variant of the first alternate embodiment, the return loss of the half-wavelength antenna has at least two resonant frequencies within the operating frequency range.
In yet another variant of the first alternate embodiment, the first resonant frequency is a function of the length of the second side of the slot, and the second resonant frequency is a function of the length of the first branch of the fork-shaped tuning stub of the half-wavelength antenna.
In a still further variant of the first alternate embodiment the invention comprises an antenna assembly, wherein the antenna assembly comprises: a half-wavelength slot antenna comprising: a dielectric substrate having a first side and a second side; an electrically conducting layer positioned on the first side of the dielectric substrate, wherein there is a rectangular slot in the electrically conducting layer exposing a portion of the first side of the dielectric substrate, and wherein the rectangular slot has at least a first side and a second side orthogonal to the first side; a feed line positioned on the second side of the dielectric substrate, wherein a centerline of the feed line extends parallel to the first side of the rectangular slot and wherein the feed line has proximal and distal ends, the distal end of the feed line extending just into a region on the second side of the dielectric substrate directly opposite the rectangular slot, bisecting the second side of the rectangular slot; a fork-shaped tuning stub positioned on the second side of the dielectric substrate directly opposite the rectangular slot of the first side, the fork-shaped tuning stub comprising a first branch extending transversely in either direction from the distal end of the feed line parallel to the second side of the rectangular slot, wherein the first branch has an intermediate point and two distal ends, the intermediate point of the first branch aligning with the distal end of the feed line, the fork-shaped tuning stub further comprising second branches extending transversely from the distal ends of the first branch parallel to the first side of the rectangular slot; and wherein the antenna assembly further comprises: a dual-band planar inverted F-antenna positioned on the dielectric substrate.
By employing slot antennas printed on a PCB of a mobile terminal, slot UWB antennas suitable for mobile terminals can be designed. Additionally, to further reduce the size of the printed slot UWB antennas, quarter-wavelength slot UWB antennas are utilized.
By using quarter-wavelength printed slot antennas, a size savings of at least 80% can be achieved in comparison to conventional half-wavelength slot antennas, while retaining desirable resonant and radiation properties. In addition, interactions between the printed slot ultra-wideband antennas and the dual-band planar inverted F-Antenna (PIFA) antennas used in mobile terminals for cellular radio systems (e.g. GSM, cdma2000, WCDMA) are substantially reduced. The isolation between the slot and PIFA antennas is low enough so that both antennas can be used in the same terminal.
Thus, a second alternate embodiment of the present invention comprises a quarter-wavelength slot antenna comprising: a dielectric substrate having a first side, a second side and at least one edge; an electrically conducting layer positioned on the first side of the dielectric substrate, wherein there is a rectangular slot in the electrically conducting layer exposing a portion of the first side of the dielectric substrate, and wherein a first side of the rectangular slot is aligned with the at least one edge of the dielectric substrate; a feed line positioned on the second side of the dielectric substrate, wherein a centerline of the feed line extends parallel to the first side of the rectangular slot and wherein the feed line extends along the at least one edge of the dielectric substrate, and wherein the feed line has proximal and distal ends, the distal end of the feed line extending just into a region on the second side of the dielectric substrate directly opposite the rectangular slot; and an L-shaped tuning stub positioned on the second side of the dielectric substrate directly opposite the rectangular slot of the first side, the L-shaped tuning stub comprising a first branch extending transversely from the distal end of the feed line away from the first edge of the dielectric substrate parallel to a second side of the rectangular slot, wherein the first branch has proximal and distal ends, the L-shaped tuning stub further comprising a second branch extending transversely from the distal end of the first branch parallel to the first side of the rectangular slot.
In one variant of the second alternate embodiment of the present invention, the feed line comprises a microstrip line.
In another variant of the second alternate embodiment of the present invention, the antenna operates in the frequency range of about 3.1 GHz to 4.9 GHz.
In a further embodiment of the second alternate embodiment of the present invention, the return loss of the quarter-wavelength antenna has at least two resonant frequencies within the operating frequency range.
In yet another embodiment of the second alternate embodiment of the present invention, the at least two resonant frequencies comprise a first resonant frequency, wherein the first resonant frequency is a function of the length of the second side of the rectangular slot; and a second resonant frequency, wherein the second resonant frequency is a function of the length of the first branch of the L-shaped tuning stub.
In a still further variant of the second alternate embodiment the invention comprises an antenna assembly, wherein the antenna assembly comprises a quarter-wavelength slot antenna comprising: a dielectric substrate having a first side, a second side and at least two edges, wherein the two edges comprise a first edge and a second edge orthogonal to the first edge; an electrically conducting layer positioned on the first side of the dielectric substrate, wherein there is a rectangular slot in the electrically conducting layer exposing a portion of the first side of the dielectric substrate, and wherein a first side of the rectangular slot is aligned with the first edge of the dielectric substrate; a feed line positioned on the second side of the dielectric substrate, wherein a centerline of the feed line extends parallel to the first side of the rectangular slot and wherein the feed line extends along the at least one edge of the dielectric substrate, and wherein the feed line has proximal and distal ends, the distal end of the feed line extending just into a region of second side of the dielectric substrate directly opposite the rectangular slot; an L-shaped tuning stub positioned on the second side of the dielectric substrate directly opposite the rectangular slot of the first side, the L-shaped tuning stub comprising a first branch extending transversely from the distal end of the feed line away from the first edge of the dielectric substrate parallel to a second side of the rectangular slot, wherein the first branch has proximal and distal ends, the L-shaped tuning stub further comprising a second branch extending transversely from the distal end of the first branch parallel to the first side of the rectangular slot; and a dual-band planar inverted F-antenna positioned on the dielectric substrate inward from the second edge of the dielectric substrate.
A third alternate embodiment of the present invention comprises a mobile station having an antenna assembly, wherein the antenna assembly comprises a half-wavelength slot antenna comprising: a dielectric substrate having a first side and a second side; an electrically conducting layer positioned on the first side of the dielectric substrate, wherein there is a rectangular slot in the electrically conducting layer exposing a portion of the first side of the dielectric substrate, and wherein the rectangular slot has at least a first side and a second side orthogonal to the first side; a feed line positioned on the second side of the dielectric substrate, wherein a centerline of the feed line extends parallel to the first side of the rectangular slot and wherein the feed line has proximal and distal ends, the distal end of the feed line extending just into a region on the second side of the dielectric substrate directly opposite the rectangular slot, bisecting the second side of the rectangular slot; a fork-shaped tuning stub positioned on the second side of the dielectric substrate directly opposite the rectangular slot of the first side, the fork-shaped tuning stub comprising a first branch extending transversely in either direction from the distal end of the feed line parallel to the second side of the rectangular slot, wherein the first branch has an intermediate point and two distal ends, the intermediate point of the first branch aligning with the distal end of the feed line, the fork-shaped tuning stub further comprising second branches extending transversely from the distal end of the first branch parallel to the first side of the rectangular slot; and wherein the first side of the rectangular slot is about 10 mm and the second side of the rectangular slot is about 28 mm; the first branch has a length of about 18 mm, and wherein the half-wavelength antenna operates in the frequency range of about 3.1 GHz to 4.9 GHz.
In one variant of the mobile station of the third alternate embodiment, the antenna assembly further comprises a dual-band planar inverted F-antenna.
A fourth alternate embodiment of the present invention comprises a mobile station having an antenna assembly, wherein the antenna assembly comprises: a quarter-wavelength slot antenna comprising: a dielectric substrate having a first side, a second side and at least one edge; an electrically conducting layer positioned on the first side of the dielectric substrate, wherein there is a rectangular slot in the electrically conducting layer exposing a portion of the first side of the dielectric substrate, and wherein a first side of the rectangular slot is aligned with the at least one edge of the dielectric substrate; a feed line positioned on the second side of the dielectric substrate, wherein a centerline of the feed line extends parallel to the first side of the rectangular slot and wherein the feed line extends along the at least one edge of the dielectric substrate, and wherein the feed line has proximal and distal ends, the distal end of the feed line extending just into a region on the second side of the dielectric substrate directly opposite the rectangular slot; and an L-shaped tuning stub positioned on the second side of the dielectric substrate directly opposite the rectangular slot of the first side, the L-shaped tuning stub comprising a first branch extending transversely from the distal end of the feed line away from the first edge of the dielectric substrate parallel to a second side of the rectangular slot, wherein the first branch has proximal and distal ends, the L-shaped tuning stub further comprising a second branch extending transversely from the distal end of the first branch parallel to the first side of the rectangular slot.
In one variant of the mobile station of the fourth alternate embodiment, the quarter-wavelength slot antenna operates in the frequency range of about 3.1 GHz to 4.9 GHz.
In another variant of the mobile station of the fourth alternate embodiment, the antenna assembly further comprises a dual-band planar inverted F-antenna.
In conclusion, printed UWB slot antennas made in accordance with the present invention have at least the following advantages: they are thin, being the thickness of the PCB only; they are resistant to breakage; and they require no special fabrication steps and are therefore inexpensive to manufacture.
The foregoing and other aspects of these teachings are made more evident in the following Detailed Description of the Preferred Embodiments, when read in conjunction with the attached Drawing Figures, wherein:
In a non-limiting embodiment of this invention, both half- and quarter-wavelength slot UWB antennas are integrated on a ground plane of length 80 mm, width 40 mm, and thickness 1 mm, which is the size of a typical PCB for a mobile terminal. The dielectric material used for the PCB is FR4 with τr=4.4, and the electric conductivity of the metals is 4.9×107. All of the antenna examples are simulated with IE3D (a commercial software package based on the method of moment). Moreover, the UWB antennas preferably operate in the frequency range of 3.1 GHz to 4.9 GHz, although this is not a limitation on the practice of the preferred embodiments of this invention.
The return loss of the half-wavelength slot antenna 7 is shown in
The electric field component (Ey) within the half-wavelength slot antenna 7 is advantageously symmetrical with respect to the central line (along y-axis) of the slot. The Ey field has its maximum at the central line of the slot 8 and its minimum at the two ends of the slot 8. Therefore, the central line of the slot 8 is an H-wall or open circuit. This beneficial property of the half-wavelength slot antenna is an important principle for designing quarter-wavelength slot UWB antennas, as illustrated below.
Because of the above-mentioned special property of half-wavelength slot antennas, quarter-wavelength slot UWB antennas can be designed by using half of the slot (where the slot is placed at one edge of the PCB).
The return loss of the quarter-wavelength slot UWB antenna 26 located at three different positions (case 1, case 2, case 3) on the PCB 20 is illustrated in FIG. 5. From
Discussed now is the isolation between the half- and quarter-wavelength slot UWB antenna, and a conventional dual band PIFA GSM antenna (working at frequencies of 0.9 GHz and 1.8 GHz). In particular, the dual-band PIFA antenna is located 8 mm above the PCB.
From these figures it can be seen that the isolation for each of the above quarter-wavelength slot UWB antenna examples is also sufficient. In addition, among the above three quarter-wavelength slot UWB antenna examples, the first quarter-wavelength slot UWB antenna of
From the above analysis, it can be readily observed that from a compactness and low profile point of view, the quarter-wavelength slot UWB antenna is suitable for use in mobile terminals and other small-form-factor electronic devices.
An advantage of using the quarter-wavelength slot UWB antennas over the half-wavelength slot UWB antenna is the size reduction, which makes the quarter-wavelength slot UWB antenna more suitable for mobile terminals. The following conclusions can be made for the quarter-wavelength and half-wavelength slot UWB antennas:
Additionally, the best isolation performance (between the dual-band PIFA antenna 40 and the quarter-wavelength slot UWB antennas 50) is obtained when the PIFA antenna 40 and the quarter-wavelength slot UWB antenna 50 have the greatest separation distance.
The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of the best method and apparatus presently contemplated by the inventors for carrying out the invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB04/03343 | 10/13/2004 | WO | 00 | 4/5/2007 |
