Not Applicable
Not Applicable
The present invention relates generally to antennas for handheld communication devices, and more particularly to multiple input, multiple output antennas.
Different types of wireless mobile communication devices, such as personal digital assistants, cellular telephones, and wireless two-way email communication equipment are available. Many of these devices are intended to be easily carried on the person of a user, often fitting in a shirt or coat pocket.
As the use of wireless communication equipment continues to grow dramatically, a need exists provide increased system capacity. One technique for improving the capacity is to provide uncorrelated propagation paths using Multiple Input, Multiple Output (MIMO) systems. MIMO employs a number of separate independent signal paths, for example by means of several transmitting and receiving antennas.
This typically requires multiple antennas which results in duplication of certain parts within the wireless mobile communication device, and results in an unfavorable trade-off between device size and performance. The trade-off is that smaller devices suffer performance problems, including shortened battery life and potentially more dropped calls, whereas devices with better performance require larger housings. The primary factor of this trade-off is mutual coupling between the antennas, which can result in wasted power when transmitting and a lower received power from incoming signals.
Effective MIMO performance requires relatively low correlation between each signal received by the multiple antennas. This is typically accomplished in large devices using one or more of: spatial diversity (distance between antennas), pattern diversity (difference between antenna aiming directions), and polarization diversity.
Unfortunately, when multiple antennas are used within a mobile handheld communication device, the signals received by those antennas are undesirably correlated, due to the tight confines typical of the compact devices that are favored by consumers. This noticeably disrupts MIMO performance. The trade-off is then to either enlarge the device, which consumers will likely shun, or else tolerate reduced performance.
Therefore, is it desirable to develop an MIMO antenna arrangement which is capable has a compact size to fit within a device housing small enough to be desired by consumers and which has improved performance.
The present antenna for a mobile wireless communication device uses fewer components and reduces signal correlation by reducing antenna coupling, even when implemented in a more compact form than prior systems. This is achieved with a geometric design that enables a single element to fulfill the roles which previously required by two individual antennas.
The antenna design is based on merging two planar inverted F-antennas (PIFAs) with a common strip and a common ground plane to provide a compact design that is well suited for a diversity antenna system in a mobile handheld device. Alternatively the antenna could also be utilized as a duplexer allowing the receive and transmit signals to be separated.
The antenna comprises a patch of electrically conductive material located in a first plane. A first leg and a second leg are spaced apart and both are formed of electrically conductive material that is electrically connected to the patch. The first and second legs are coplanar and transverse to the first plane. An electrically conductive strip is connected to the patch and to the first leg, wherein the strip is transverse to the first plane. A third leg is electrically connected to and projects away from the strip. The antenna has a first signal port for applying a first signal to the first leg, and a second signal port for applying a second signal to the third leg.
The present antenna is advantageously useful with mobile wireless communication devices, such as personal digital assistants, cellular telephones, and wireless two-way email communication devices, and will be described in that context. Nevertheless this antenna may be employed with other types of radio frequency equipment.
Referring initially to
The housing 21 contains a main dielectric substrate 22, such as a printed circuit board (PCB) substrate, for example, on which is mounted the primary circuitry 24 for mobile device 20. That primary circuitry 24, typically includes a microprocessor, one or more memory devices, along with a display and a keyboard that provide a user interface for controlling the mobile device.
An audio input device, such as a microphone 25, and an audio output device, such as a speaker 26, function as an audio interface to the user and are connected to the primary circuitry 24.
Communication functions are performed through a radio frequency circuit 28 which includes a wireless signal receiver and a wireless signal transmitter that are connected to a MIMO antenna assembly 29. The antenna assembly 29 can be carried within the lower portion of the housing 21 and will be described in greater detail herein.
The mobile wireless communication device 20 also may comprise one or auxiliary input/output devices 27, such as, for example, a WLAN (e.g., Bluetooth®, IEEE. 802.11) antenna and circuits for WLAN communication capabilities, and/or a satellite positioning system (e.g., GPS, Galileo, etc.) receiver and antenna to provide position location capabilities, as will be appreciated by those skilled in the art. Other examples of auxiliary 110 devices 27 include a second audio output transducer (e.g., a speaker for speakerphone operation), and a camera lens for providing digital camera capabilities, an electrical device connector (e.g., USB, headphone, secure digital (SD) or memory card, etc.).
With reference to
A rectangular patch 42 of conductive material is located on the first surface 34 at one corner of the support and extends along the two adjacent edges where the first surface abuts the third and fourth surfaces 36 and 37, as shown particularly in
A conductive strip 48 is located on the fourth surface 37 and extends along the two edges at which the fourth surface abuts the first and third surfaces 34 and 36, respectively. The conductive strip 48 is electrically connected at those edges to the patch 42 and the first conductive leg 44. The conductive strip 48 extends approximately half the distance between the first and second surfaces 34 and 35, for example. In addition, the conductive strip 48 extends along the edge between the first and fourth surfaces 34 and 37 approximately twice the distance that the conductive patch 42 extends along that edge, for example. A conductive third leg 50 projects, like a tab, from the strip 48 toward the edge at which the fourth surface 37 abuts the second surface 35 and is spaced from that edge so as to be electrically isolated from the ground plane, conductive layer 40. Preferably the conductive strip 48 abuts the patch 42 and the first leg 44 so as to be contiguous therewith. The conductive strip 48 and the first and third legs 44 and 50 that are contiguous to the strip, form an inverted F-element.
A first signal port 52 is provided by electrical contacts on the first leg 44 and the ground plane 40. A second signal port 54 is provided by contacts with the third leg 50 of the conductive strip 48 and the ground plane, conductive layer 40.
The first and second signal ports 52 and 54 are connected to the radio frequency circuit 28 which can use the antenna to transmit signals in several different modes. In one mode, the excitation signal is applied to the first signal port 52, while the second port 54 is terminated by a 50 Ohm impedance, for example. In a second mode, the first port 52 is terminated with a 50 Ohm impedance, for example, and the excitation signal is applied to the second port 54. Alternatively, two separate excitation signals can be applied simultaneously to the antenna 30, one excitation signal to each of the two signal ports 52 and 54. Each signal port excites the antenna with a two-way current distribution in the X or Y direction or two-way polarizations in order to achieve polarization diversity. Since the direction of the currents from the two signal ports 52 and 54 are almost opposite, the current coupling between the ports is relatively low, thereby achieving high isolation between those ports.
With reference to
Each antenna 101-104 has a first port 118 connected between the first leg 110 and the conductive layer 120 on the second surface 109 of the support 105. The second port 119 of each antenna is connected between the third leg 116 and the ground plane, conductive layer 120.
The four antennas 101-104 in
Every single element antenna 201-204 has a first signal port 214 connected between its first leg 208 and the ground plane 218 and a signal second port 216 connected between its third leg 215 and the ground plane.
Each antenna 201-204 in
With reference to
The strip 310 and the first and second legs 306 and 308 on a side surface of the support 305 are in electrical contact with the associated patch 314 of the same antenna, wherein the patch is on the first support surface 316. Each antenna 301-304 has a first signal port 318 connected between the first leg 306 and the ground plane 322 and a second signal port 320 connected between the third leg and the ground plane 322.
The antenna assembly 300 also may have the optional shorting conductors 324 located between the ground plane 322 and the end of the first leg 308 that abuts the strip 310 in each antenna 301-304.
The four dual-port antennas in the antenna assemblies illustrated in
Antenna assembly 400 is special case of the present multiple-input, multiple-output antenna in which four dual-port antennas 401, 402, 403, and 404 are located at the corners of a first surface 406 of a substrate 405. An opposite second surface 407 has a the conductive layer 418 thereon. All four of the antennas 401-404 are identical and the details of the first antenna 401 shall be described.
The first antenna 401 has a first electrically conductive strip 408 extending along an edge where the first surface 106 abuts an orthogonal third surface 412. The first strip 104 abuts and is contiguous with a second strip 410 that extends from the substrate corner along another edge of the first surface 406 that abuts a fourth surface 414. The third and fourth surfaces 412 and 414 form side surfaces of the substrate.
The first antenna 401 includes a first signal port 416 between the first strip 408 and a conductive layer 418, that forms a ground plane on the second surface of the substrate 405. A second signal port 420 of the first antenna 14 provides electrical connection between the conductive layer 418 and the second strip 410. An optional shorting conductor 415 extends along the corner edge between the third and fourth surfaces 412 and 414 providing an electrical connection of the first and second strips 408 and 410 to the conductive layer 418.
A further version of an eight-port antenna assembly 500 is shown in
The first antenna 501 has first and second strips 508 and 510 that are contiguous and aligned with each other along the edge of the first surface 506 that abuts and orthogonal third surface 512. A first signal port 515 provides a connection between the first strip 508 and the conductive layer 518 on the second a surface 507. A second signal port 516 provides connection between the conductive layer 518 and the second strip 510. An optional shorting conductor 520 extends from the interface between the first and second conductive strips 508 and 510 and the conductive layer 518.
The foregoing description was primarily directed to a certain embodiments of the antenna. Although some attention was given to various alternatives, it is anticipated that one skilled in the art will likely realize additional alternatives that are now apparent from the disclosure of these embodiments. Accordingly, the scope of the coverage should be determined from the following claims and not limited by the above disclosure.
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Number | Date | Country | |
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Number | Date | Country | |
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Parent | 12364932 | Feb 2009 | US |
Child | 13447418 | US |