Patent Application
20100328163
1. Field Of The Invention
This invention relates to wireless communication systems, in particular, directional antennas for use in wireless communication systems.
2. Background
In wireless communication systems, antennas are used to transmit and receive radio frequency signals. In general, the antennas can be omni-directional, receiving and transmitting signals from any direction, or directional, with reception and transmission of signals limited in direction. In general, directional antennas provided increased gain over an omni-directional antenna because the directional antenna's coverage is focused over a small spatial region. Because a directional antenna covers a limited spatial region, the antenna needs to be “pointed” so that it can transmit and receive signals in a desired direction. Some conventional antenna systems include multiple directional antennas, or elements, arranged in an array such that individual elements “point” in different directions. By selecting desired elements of the array the overall direction of the antenna system can be varied. In addition, there exist antenna systems which provide directive gain with electronic scanning, such as phased arrays, rather than being fixed. However, many such electronic scanning technologies are plagued with excessive loss and high cost. In addition, many of today's wireless communication systems provide very little room for antennae elements.
One type of directional antenna that is popular is traditional Yagi-Uda (“Yagi”) antenna. A traditional Yagi antenna includes a driven element, the element a signal is fed to by a transmitter or other signal source, called the driver or antenna element, one or more reflectors, and one or more director elements. The reflector and director elements are parasitic elements that are not driven. By choosing the proper length and spacing of a reflector element from the driven element, as well as the length and spacing of director elements, the induced currents on the reflector and director elements will re-radiate a signal that will additively combine with the radiation from the driven element to form a more directive radiated beam compared to the radiation from the driven element alone. The most common Yagi arrays are fabricated using a dipole for the driven element, and straight wires for the reflector and director elements. The reflector element is placed “behind” the driven element and the director elements are placed in “front” of the driven element. The result is a linear array of wires that together radiate a beam of radio frequency (RF) energy in the forward direction. The directivity, and therefore the gain, of the radiated beam can be increased by adding additional director elements, but at the expense of overall antenna size. The director element can be eliminated, which leads to a smaller antenna with wider beam width coverage compared to Yagi antennas utilizing director elements.
In conventional Yagi antennas, the driven element is a dipole element that has a length that is nominally one-half of a wavelength of the radio frequency (RF) signal transmitted or received by the antenna. The reflector element is usually approximately five percent longer than the dipole and the director elements are approximately five percent shorter than the dipole. The spacing between the elements is critical to the design of the Yagi and varies from one design to another, with element spacing typically varying between one-eighth and one-quarter wavelength. While the Yagi antenna dos provide a relatively simple directional antenna design, the overall size is usually relatively large because of the reflector and director elements and the spacing between the elements.
There is a need in the art for improved antennas that can provide directional gain and are compact in size.
The present invention includes a method, apparatus and system as described in the claims. In one embodiment, an antenna system includes a dual-band strip line monopole element. The monopole element includes a radio frequency (RF) choke, such as a coplanar waveguide stub, located at one end of the element above a lower portion of the element. The overall length of the monopole element is selected so as to resonate at a first desired frequency. For example, the overall length of the monopole element can be selected to be about a one quarter wavelength of the first desired frequency. The length of the lower portion is selected so as to resonate at a second desired frequency. For example, the length of the lower portion of the monopole element can be selected to be about a one-quarter wavelength of the second desired frequency. The antenna system also includes a first reflector element located at a distance from the monopole element corresponding to a reflective distance of the first desired frequency, wherein a length of the first reflector element is selected so as to resonate at the first desired frequency. For example the distance from the monopole element to the first reflector and the length of the first reflect can be about a quarter wavelength of the first desired frequency. The antenna system includes a second reflector element located between the monopole element and the first reflector, wherein the second reflector element is located at a distance corresponding to a reflective distance of the second desired frequency. The length of the second reflector is selected so as to resonate at the second desired frequency. For example, the distance from the monopole element to the second reflector and the length of the second reflector can be about a quarter wavelength of the second desired frequency.
In another embodiment, an antenna system includes a first and a second dual-band strip line monopole elements, and each monopole element includes an RF chock, such as a coplanar waveguide stub, located at one end of the element above a lower portion of the element, An overall length of the monopole element is selected so as to resonate at a first desire frequency, for example, the overall length of the monopole element can be selected to be about a one quarter wavelength of the first desired frequency. A length of the lower portion of the monopole element is selected so as to resonate at a second desired frequency, for example, the length of the lower portion of the monopole elements can be selected to be about a one-quarter wavelength of the second desired frequency. The antenna system also includes a common reflector element located between the first and second monopole elements. The common reflector is located at a reflective distance of the first desired frequency from each of the first and second monopole elements. A length of the common reflector element is selected so as to resonate at the first desired frequency, for example the length of the common reflector is selected to be about a quarter wavelength of the first desired frequency. The antenna system includes a first and a second reflector elements, wherein the first reflector element is located between the first monopole element and the common reflector and the second reflector element is located between the second monopole element and the common reflector. The first and second reflector elements are each located at a distance from the first and second monopole elements corresponding to a reflective distance of the second desired frequency. In addition, each of the first and second reflector elements has a length selected so as to resonate at the second desired frequency. For example, the length of the first and second reflectors can be selected to be about a quarter wavelength of the second desired frequency.
In the embodiments of the antenna systems, a ratio of the second desired frequency to the first desired frequency can be a non-integer value. For example, if the monopoles include an RF chock, such as a quarter wavelength choke or a coplanar stub, then the ratio of the second desired frequency to the first desired frequency can be greater than about 2. In another embodiment, if a lumped RF choke is used then the ratio of the second desired frequency to the first desired frequency can be less than about 2. In one embodiment, the first desired frequency is about 2.4 GHz and the second desired frequency is about 5 GHz.
The antenna system can be implemented on a supporting structure, for example, a cardbus card, or a PCMCIA card.
A method of varying a beam pattern of an antenna includes having a first dual-band strip line monopole element reflectively coupled to a first and second reflector and a second dual-band strip line monopole element reflectively coupled to the first and a third reflector. Applying a first signal at a desired frequency to the first dual-band strip line monopole element, wherein the frequency of the signal is selected to cooperate with, and reflect from one of the first and second reflectors to thereby radiate a radio frequency signal in a first direction, and applying a second signal at a desired frequency to the second dual-band strip line monopole element, wherein the frequency of the signal is selected to cooperate with, and reflect from one of the third reflector to thereby radiate a radio frequency signal in a second direction.
In one embodiment, a wireless communication device can include a dual-band antenna having a first monopole element reflectively coupled to a first reflector and a second monopole element reflectively coupled to a second reflector; wherein the first monopole element and first reflector are configured to form a radio frequency beam pattern in a first direction and the second monopole element and second reflector are configured to form a radio beam pattern in a second direction. The wireless communication device also includes a radio module configured to transmit and receive radio frequency signals, and a switch configured to controllable couple the radio module to the first or the second monopole elements.
In another embodiment, a wireless communication device includes a dual-band antenna having a first monopole element reflectively coupled to a first reflector and a second monopole element reflectively coupled to a second reflector; wherein the first monopole element and first reflector are configured to form a radio frequency beam pattern in a first direction and the second monopole element and second reflector are configured to form a radio beam pattern in a second direction. The wireless communication device also includes a radio module comprising a plurality of radios, wherein a first radio is communicatively coupled to the first monopole element and a second radio is communicatively coupled to the second monopole element.
Other features and advantages of the present invention will become more readily apparent to those of ordinary skill in the art after reviewing the following detailed description and accompanying drawings.
These and other aspects, advantages and details of the present invention, both as to its structure and operation, may be gleaned in part by a study of the accompanying drawings, in which like reference numerals refer to like parts. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.
Certain embodiments as disclosed herein provide for systems, methods, and apparatuses for a wireless communication device having a multi-beam, multi-band antenna and methods for manufacturing the same. For example one system and method described herein provides a plurality of antenna elements where one or more elements are active and other elements form reflectors for the one or more active elements. As described, the active elements and reflector cooperate to create directed transmissions, or direction of positive gain for the antenna system, at one or more frequency bands. The system can be used for various wireless communication protocols and at various frequency ranges. For example, the system can be used at frequency ranges and having bands centered around 2.4 Ghz, 5.0 Ghz, or other desired frequency bands.
After reading this description it would become apparent to one skilled in the art how to implement the invention in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be described herein, it is to be understood that these embodiments are presented by way of example only, and not limitations. As such, this detailed description of various embodiments should not be construed to limit the scope or breadth of the present invention. In the description that follows, an example is described for a dual-band antenna that has two main directions of transmission and operates at two primary radio frequency (RF) frequencies. It is noted that the invention is not limited to two directions of transmission nor two frequency bands, and this example is merely used to illustrate aspects and features of the invention. Thus, the aspects and features described can be used to implement any desired number of directions and any desired number of frequency bands.
In one embodiment, because the RF chokes, such as coplanar waveguide stubs, 108 and 110 have capacitive impedance at 2.5 GHz, the monopoles 104 and 106 may be a bit shorter than a quarter of wavelength at 2.4 GHz. In one example, the monopoles 104 and 106 are approximately 20% shorter that a quarter wavelength at 2.4 GHz. As noted, the chokes, or stubs, 108 and 110 are located about a quarter of a wavelength 130 above a ground plane 120. The width and length of the monopoles 104 and 106 can be selected to achieve a desired impedance. In one embodiment, the monopoles 104 and 106 width and length can be selected to achieve an impedance close to 50 Ohms at 2.4 and 5 GHz.
In the example of
In one embodiment, the distance 132 and 134 between the common reflector and each of the two monopoles 104 and 108 may be approximately a quarter of a wavelength at 2.4 GHz. The length 136 of the common reflector 122 can be a resonate length at the first desired frequency, for example, about a quarter of a wavelength at 2.4 GHz.
The example dual-band antenna 102 illustrated in
In one embodiment, a coplanar waveguide stub is included at the end of the common reflector 122. including a coplanar waveguide stub at the end of the common reflector 122 adapts the common reflector 122 into a dual-band reflector. In this case, the lower portion of each monopole, that resonates, for example at 5 GHz, will have two reflectors instead of one. This configuration may increase the antenna gain at 5 GHz.
In the example of
As discussed further below, each RF input 150 and 152 can provide a separate antenna beam. Providing separate antenna beams provides many advantages. For example, the dual-band antenna 102 can be used in multiple input multiple output (MIMO) communication devices, such as a diversity-switched antenna in a 2×2 MIMO.
The dual-band antenna 102 concept illustrated in
If an RF signal at the second desired frequency is fed to the first RF input 150 then only the lower portion 112 of the monopole 104 will resonate because the upper portion of the monopole 104 is a coplanar waveguide stub 108 that has a very high impedance at the second desired frequency and isolates the stub 108. For example, in one embodiment, the input impedance of the coplanar waveguide stub 108 very high at 5 GHz. This high impedance at 5 GHz isolates the top portion of the monopole from the bottom portion of the monopole at 5 GHz.
Again, similarly to a two element Yagi antenna, the lower portion 112 of the monopole 104 and the reflector 124 located between the first monopole 104 and the common reflector 122 will cooperate to produce an antenna beam pattern 206 at the second desired frequency, generally, to the left of the dual-band antenna 102. The common reflector 122 does not resonate at the second desired frequency because its length was selected to be a resonate length at the first desired frequency, and therefore has minimal impact on the antenna beam pattern 206.
In a similar manner, an RF signal at the first desired frequency that is fed into the second RF input 152 will produce an antenna beam pattern 210 at the first desired frequency, generally, to the right of the dual-band antenna 102. Also, an RF signal at the second desired frequency fed into the second RF input 152 will produce an antenna beam pattern 212 at the second desired frequency, generally, to the right of the dual-band antenna 102
In one embodiment of the example illustrated in
If a 5 GHz RF signal is fed to the first RF input 150 then only the lower portion 112 of the monopole 104, which has a resonant size for a 5 GHz signal, will resonate because the upper portion of the monopole 104 is an RF choke, such as a coplanar waveguide stub, 108 that has a very high impedance at 5 GHz and isolates the stub 108. Again, similarly to a two element Yagi antenna, the lower portion 112 of the monopole 104 and the reflector 124 located between the first monopole 104 and the common reflector 122 that is a size selected to resonate at 5 GHz, will cooperate to produce a 5 GHz RF beam pattern 206 radiating, generally, to the left of the dual-band antenna 102. The common reflector 122 that is a resonate size for a 2.4 GHz signal does not resonate at 5 GHz, for example because it is too long, and therefore has minimal impact on the radiate RF beam 206.
In a similar manner, a 2.4 GHz RF signal fed into the second RF input 152 will produce a 2.4 GHz RF beam pattern 210 radiating, generally, to the right of the dual-band antenna 102. Also, a 5 GHz signal fed into the second RF input 152 will produce a 5 GHz RF beam pattern 212 radiating, generally, to the right of the dual-band antenna 102
As illustrated in
While the example illustrated in
The discussion above described an antenna that operates at two different frequencies and antenna patterns that are opposite each other. Other configurations of frequencies and patters are possible. For example, different configurations of monopoles and reflectors can operate at different frequencies. Likewise, different arrangements of monopoles and reflectors can produce various beam patterns. In addition, other configurations can operate at more than two different frequencies.
The dual-band antenna described herein can be used with many different radio systems. For example, the antenna system can be combined with the systems described in U.S. patent application Ser. No. 11/209,358, filed Aug. 22, 2005 entitled “Optimized Directional Antenna System”, assigned to the assignee of the present application and hereby incorporated by reference in its entirety. The dual-band antenna described can also be used in MIMO applications, and other applications where an antenna that can provide directionality and operate at multiple frequencies would be useful.
The dual-band antenna can also be located on many different support structures. For example, the dual-band antenna can be located on a Cardbus card, or a PCMCIA card.
The radio system 504 includes a radio sub-system 522. In the example of
The signal processing module 512 implements the MIMO processing. MIMO processing is well known in the art and includes the processing to send information out over two or more radio channels using the dual-band antenna system 502 and to receive information via multiple radio channels and antennas as well. The signal processing module can combine the information received via the multiple antenna into a single data stream. The signal processing module may implement some or all of the media access control (MAC) functions for the radio system and control the operation of the radios so as to act as a MIMO system. In general, MAC functions operate to allocate available bandwidth on one or more physical channels on transmissions to and from the communication device. The MAC functions can allocate the available bandwidth between the various services depending upon the priorities and rules imposed by their QoS. In addition, the MAC functions operate to transport data between higher layers, such as TCP/IP, and a physical layer, such as a physical channel. The association of the functions described herein to specific functional blocks in the figure is only for ease of description. The various functions can be moved amongst the blocks, shared across blocks and grouped in various ways.
A central processing unit (CPU) 514 is in communication with the signal processor module 512. The CPU 514 may share some of the MAC functions with the signal processing module 512. In addition, the CPU can include a data traffic control module 516. Data traffic control can include, for example, routing associated with data traffic, such as a DSL connection, and/or TCP/IP routing. A common or shared memory 518 which can be accessed by both the signal processing module 512 and the CPU 514 can be used. This allows for efficient transportation of data packets between the CPU and the signal processing module.
A signal quality metric for each received signal and/or transmitted signal on a communication link can be monitored to determine which portion of the dual-band antenna system 502 is preferred, for example, which direction it is desired to radiate or receive RF signals. The signal quality metric can be provided from the MIMO signal processing module 512. The MIMO signal processing module has the ability to take into account MIMO processing before providing a signal quality metric for a communication link between the wireless communication device 500 and a station with which the wireless communication device is communicating. For example, for each communication link the signal processing module can select from the MIMO techniques of receive diversity, maximum ratio combining, and spatial multiplexing each. The signal quality metric received from the signal processing module, for example, data through put or error rate, can vary based upon the MIMO technique being used. A signal quality metric, such as received signal strength, can also be supplied from one or more of the radios 510a and 510b. The signal quality metric can be used to determine or select which portions of the dual-band antenna and which frequency it is desired to use.
The processor module 608 may implement some or all of the media access control (MAC) functions for the radio system 604 and control the operation of the radio module 606. In general, MAC functions operate to allocate available bandwidth on one or more physical channels on transmissions to and from the communication device 600. The MAC functions can allocate the available bandwidth between the various services depending upon the priorities and rules imposed by their QoS. In addition, the MAC functions can operate to transport data between higher layers, such as TCP/IP, and a physical layer, such as a physical channel. The association of the functions described herein to specific functional blocks in the figure is only for ease of description. The various functions can be moved amongst the blocks, shared across blocks and grouped in various ways. The processor is also in communication with a memory module 610 which can store code that is executed by the processing module 608 during operation of the device 600 as well as temporary store during operation.
In the example of
In the example of
Operation of the switch 714 can be to select one of the antennas 712a or 712b in response to a signal quality metric, such as received signal strength. In one embodiment, the signal metric can be communicated from the radio 706 to the processor module 708 and the processor module 706 operates the switch 714 to select a desired antenna 712a or 712b.
Various characteristics of the antenna have been described in embodiments herein. by way of example in terms of parameters such as wavelengths and frequency. It should be appreciated that the examples provided describe aspects that appear electrically to exhibit a desired characteristic.
The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Numerous modifications to these embodiments would be readily apparent to those skilled in the art, and the principals defined herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the invention is not intended to be limited to the embodiment shown herein but is to be accorded the widest scope consistent with the principal and novel features disclosed herein.
The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein can be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor can be a microprocessor, but in the alternative, the processor can be any processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
The steps of a method or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium. An exemplary storage medium can be coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The processor and the storage medium can reside in an ASIC.
Furthermore, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and method steps described in connection with the above described figures and the embodiments disclosed herein can often be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled persons can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the invention. In addition, the grouping of functions within a module, block, circuit or step is for ease of description. Specific functions or steps can be moved from one module, block or circuit to another without departing from the invention.
This application claims the benefit of U.S. provisional patent application Ser. No. 60/762,644, filed Jan. 27, 2006, entitled “Dual-Band Antenna” which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60762644 | Jan 2006 | US |
