Patent Application
20090146887
The present invention relates generally to devices that contain multiple antennas.
Modern mobile computing devices are typically capable of carrying out communications using a plurality of different wireless protocols. Different types of wireless communication require separate antennas. These different types of antennas each take up space within the mobile computing device. Since mobile computing devices have a limited amount of space, the addition of more wireless communications protocols becomes difficult because of space constraints.
The present invention relates to reduced volume antennas. The antenna device includes (a) a first wireless communications arrangement which is capable of at least one of transmitting and receiving. In addition, the device includes (b) a first antenna coupled to the first wireless communications arrangement and (c) a second wireless communications arrangement which is capable of at least one of transmitting and receiving. Furthermore, the device includes (d) a second antenna coupled to the second wireless communications arrangement. The second antenna acts as a parasitic element for the first antenna.
The exemplary embodiments of the present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The exemplary embodiments of the present invention describe devices that minimize the space requirements of multiple antennas.
A “device,” as used in this disclosure, may refer to any type of device that may send or receive signals through the use of an antenna. For example, the device may be a handheld computer, a notebook computer, a personal digital assistant (“PDA”), a scanner, a mobile telephone, a data acquisition device, a camera, a pager, etc. Though the exemplary embodiments of the present invention may refer specifically to mobile computing devices, as such devices may greatly benefit from reducing the overall amount of space devoted to antennas, the broader principles of the present invention are equally applicable to any other type of device that may include a plurality of antennas.
An “antenna” is a transducer used to transmit and receive radio waves. Though the exemplary embodiments described below will refer to specific types of antennas, those of skill in the art will understand that the same principles are applicable to antennas used for any purpose. Many types of antennas use “parasitic elements,” which are antenna elements that do not have any wired input or output, but either reflect or absorb and re-radiate radio waves sent to or from an active antenna element in proximity to the parasitic element. The use of parasitic elements improves the performance of antennas. The same effect can be achieved by the addition of lumped elements (e.g., capacitors or inductors) to the antenna, but this can result in losses. However, the use of parasitic elements and lumped elements takes up additional space within a device.
Modern mobile computing devices may communicate wirelessly using a plurality of communication protocols. For example, a mobile device may be able communicate with a wireless local area network (“WLAN”), a wireless wide area network (“WWAN”), one or more peripherals using the Bluetooth protocol, a global positioning system (“GPS”), a radio frequency identification (“RFID”) protocol, etc. In prior embodiments of such devices, the antennas for each of these are separated from each other and occupy considerable volume within the device. This is challenging given the small form factor of mobile devices, and makes it difficult to further decrease the size of such devices.
By locating the antennas 150 and 160 proximately to one another, the antenna 160 may act as a parasitic element for the antenna 150, and vice versa. In other words, as described above, the antenna 160 may act as a capacitive element to reflect or absorb and re-radiate radio waves that have been sent to or from the antenna 150, while the antenna 150 does the same for radio waves sent to or from the antenna 160. Those of skill in the art will understand that the radio waves may interfere with one another if they are transmitted on similar frequency bands; thus, acceptable isolation may be achieved by using the antennas 150 and 160 for communication on frequency bands that are suitably different from one another. Meeting the technical specification for an acceptable isolation is an important factor for practical implementation of the exemplary embodiments of the present invention. This ensures reduced interference between the antennas 150 and 160 (in this case, working at different frequencies) connected to their respective transceivers/receivers.
Those of skill in the art will understand that the antennas 150 and 160 must be located close enough to one another that they are capable of acting as parasitic elements for one another, providing the right amount of coupling. The precise proximity required will depend on the amount of coupling required between the antennas 150 and 160 and depends on the individual designs of the antennas 150 and 160. For example, if the antenna 150 is a Bluetooth antenna operating in a frequency range appropriate for Bluetooth functionality (e.g., 2.4 GHz to 2.4835 GHz), and the antenna 160 is a GPS antenna operating on a frequency appropriate for GPS functionality (e.g., 1176.45 MHz, 1227.60 MHz, 1379.913 MHz, 1381.05 MHz or 1575.42 MHz), they may be placed a first distance from one another, while if the antenna 150 is an 802.11 antenna operating in a frequency band appropriate for 80:2.11 communication (e.g., 2.4 GHz to 2.5 GHz) and the antenna 160 is an WWAN antenna operating at a frequency appropriate for WWAN communication (e.g., 850 MHz, 900 MHz, 1800 MHz, 1900 MHz), they may be placed a second distance from one another. The first and second distances may or may not be the same.
The exemplary embodiments of the present invention aid in the design of devices including multiple antennas by making it possible to simultaneously improve the performance of the antennas and conserve space within the devices. As discussed above, conserving space is of particular importance in modern mobile computing devices. By the implementation of these exemplary embodiments, multiple antennas can be located in close proximity to one another, improving the performance of both in confined space while eliminating the need for passive elements that serve no other function.
The above described exemplary embodiments refer specifically to devices using exactly two antennas acting as parasitic elements for one another. However, those of skill in the art will understand that other embodiments that incorporate antennas configured in groups of more than two are also possible. For example, in another exemplary embodiment, an antenna housing may contain three antennas, all of which operate on frequencies that differ sufficiently so as to not interfere with one another, and all of which are spaced at appropriate distances from one another to act as parasitic elements for one another as described above. Other exemplary embodiments may include differing numbers of antennas selected and placed in similar manners.
The present invention has been described with reference to the above specific exemplary embodiments. However, those of ordinary skill in the art will recognize that the same principles may be applied to other embodiments of the present invention, and that the exemplary embodiments should therefore be read in an illustrative, rather than limiting, sense.
