Patent Application
20110012792
This invention relates generally to antennas, and more particularly to a multiband antenna operating on several distinct bands.
As wireless devices become exceedingly slimmer and greater demands are made for antennas operating on a diverse number of frequency bands, common antennas such as a Planar Inverted “F” Antenna (PIFA) design becomes impractical for use in such slim devices due to its inherent height requirements. Antenna configurations typically used for certain bands can easily interfere or couple with other antenna configurations used for other bands. Thus, designing antennas for operation across a number of diverse bands each band having a sufficient bandwidth of operation becomes a feat in artistry as well as utility, particularly when such arrangements must meet the volume requirements of today's smaller communication devices.
Another concern with antenna designs in general for multi-band phones includes optimized antenna performance across desired frequency bands. Existing designs may have call drop issues or poor performance that relate to loading on antennas caused by hand grips on a portion of the phone or caused by loading caused by other loading conditions. Furthermore, antennas designed for PCS bands are generally configured to be optimized across the entire PCS band which may not be ideal for a number of scenarios.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present disclosure.
One embodiment of the present disclosure can entail an antenna arrangement for a multimode communication device having a first antenna designed primarily for operation in a low band below 1000 MHz and in predetermined modes for high bands above 1500 MHz, a second antenna designed to operate solely or only in the high bands, a Voltage Standing Wave Ratio (VSWR) tuner coupled to the first antenna, and a controller coupled to the VSWR tuner. The antenna arrangement can also entail a switching mechanism for selecting between the first antenna and the second antenna where the controller would be coupled to the switching mechanism and the tuner.
Another embodiment of the present disclosure can entail a multimode communication device having an antenna arrangement having a first antenna designed for operation in both low bands and high bands, a second antenna designed to operate solely or only in high bands, a tuner coupled to the first antenna adapted to adjust matching elements to modify return loss to lower reflected power, a switching mechanism for selecting between the first antenna and the second antenna, and a controller coupled to the switching mechanism and the tuner.
Yet another embodiment of the present disclosure can entail an antenna arrangement for a multimode communication device having a tuner coupled to a first antenna adapted to adjust matching elements to modify return loss to lower reflected power where the antenna is designed for operation in both low bands and high bands, a switching mechanism for selecting between the first antenna and a second antenna, where the second antenna is designed to operate only in high bands, and a controller coupled to the switching mechanism and the tuner.
The transceiver 12 utilizes technology for exchanging radio signals with a radio tower or base station of a wireless communication system according to common modulation and demodulation techniques. Such techniques can include, but are not limited to, GSM, TDMA, CDMA, WiMAX, WLAN among others. The controller 30 utilizes computing technology such as a microprocessor and/or a digital signal processor with associated storage technology (such as RAM, ROM, DRAM, or Flash) for processing signals exchanged with the transceiver 12 and for controlling general operations of the communication device 10. The communication device 10 can separately include additional antennas at different locations such as a side antenna that can be a receive antenna in the range of 2100 MHz. Alternatively or optionally, the communication device can include a WLAN or Bluetooth antenna in operational range of 2440 MHz for example. The communication device 10 can also include a GPS antenna that operates in the range of 1575 MHz.
Referring to
A main aspect of the embodiments involves an antenna arrangement that includes at least one low band antenna optimized by tuning in conjunction with using diversity with a high band antenna. In another aspect, the embodiments can determine a priori which pieces or portions of the spectrum a user is likely to use based on their geographic location and wireless carrier and then modify the antenna(s) to optimize operation of the antenna for the predetermined portions or pieces of the spectrum likely to be used.
With respect to the main aspect, the embodiments here hinge on an observation that the cause of loss of efficiency of an antenna due to a user can be attributed to predominantly impedance mismatch or resistive losses in user tissue and further recognizing that the lower bands' effects are typically include a significant contribution from impedance mismatch and the higher band effects are primarily due to resistive losses in the tissue. An antenna tuning and selection scheme as contemplated herein tunes the antennas impedance for operation at the low band and further uses an antenna selection scheme for the high band operation. Such an arrangement can reduce volume requirements as compared to an antenna selection scheme at low band, and can improve performance for the high band as compared to an antenna tuning scheme. Although antenna selection schemes and antenna tuning are both separately known techniques, utilizing both techniques as combined in the manner described is not known.
In combating hand effects, it is important to consider the two main mechanisms for loss of realized efficiency, absorption and mismatch, and the way in which these effects vary with frequency. The bar charts 100 of
On the other hand, from inspection of the high band family of curves as seen in section 104 of the bar graph, it is seen that there is little opportunity for improvement from a VSWR tuner (radiation and system efficiencies are nearly the same). At highband, the dominant loss mechanism is absorptive (dissipation in the tissue of the hand). These observations are consistent with the known current distributions of the antennas in the respective bands. At lowband, strong currents are distributed over the entire phone chassis, as it is small relative to a wavelength, while at highbands, the current distribution (while still involving the entire chassis) is more strongly localized to the antenna area. These facts lead to the greater opportunity for addressing hand impacts at the highband using redundant antennas, or more specifically adding a second antenna that is selected for use modes when the hand is covering the first antenna. In reference to the system efficiencies for two or more redundant antennas across two use cases it has been found that substantial benefit can be obtained at the high band via redundant antennas (that is, by selecting the antenna that is out of the user's hand in a given use mode).
In terms of implementation, the lowband VSWR tuner can be realized by monitoring reverse power and adjusting matching elements to maximize return loss or by selecting from a finite set of impedance match states based on the phone's knowledge that a user's hand is present, as may be determined for example by a proximity sensor. The users hand position may also be determined by other methods. For example, if the phone is being used to enter text on a QWERTY keypad a specific handgrip may be presumed. The highband antenna selection algorithm can choose one antenna or the other based on the phone's knowledge that it is in a voice call using the earspeaker (and thus against the user's head) or a data mode of operation (and thus in the user's hand(s)), or alternatively, the highband antenna selection algorithm can employ a more sophisticated algorithms monitoring, for example, received signal quality in a diversity system and selecting the antenna that produces the highest signal quality. When operating in the high band it is also possible for both antennas to be directly connected to separate high band receivers allowing for max ratio combining diversity to be implemented.
The proposed scheme can minimize added volume for the communication device. Since antenna size is inversely proportional to operating frequency, only a redundancy antenna is added at the high bands, where the required volume is less. The lowband (where antenna volume is approximately two times greater) is served by a single antenna as is common practice now. Thus, instead of volume, additional circuit complexity is added in the form of a tunable match which would take up less volume and provide more benefit than a second low band antenna.
Although most embodiments disclosed herein involve a dual band or multi-band antenna that covers both high and low bands and a separate high band antenna, Applicants contemplate within the scope of the claimed embodiments that 2 (or more) separate multi-band antennas can be implemented to provide low band and high band diversity or MIMO (Multiple Input, Multiple Output) if necessary. Note that two separate multi-band antennas that both cover low bands may require a larger volume configuration than an arrangement that has separate multi-band antennas where at least one of the antennas only covers high bands.
Although antenna systems are primarily designed for voice-centric devices, the more current devices shipping or being developed are not necessarily voice-centric. The market already demands devices that are optimized for SMS usage, for example QWERTY-optimized landscape-mode devices, and it can be anticipated that high-data-rate applications will also come to play a significant part in the user experience. Hence, in addition to supporting good radiated performance in the talking mode (device held to head at the ear), new designs should have high RF functionality when held in one or more data modes of operation (device held in one or both hands while viewing the display).
Current antenna architectures or platforms with the antenna located at the bottom of the phone are highly optimized for talk mode and rather disadvantaged for many data modes of operation. Embodiments herein provide an antenna architecture or arrangement that can support the necessary multiple, conflicting, use modes in a single device, while minimizing any volume, cost, and complexity added to the antenna system. Such an antenna system as shown in the communication device 200 of
The positioning of the antenna can be arranged to be optimized for hand effects. Antennas located at the top of the phone or communication device tend to have less efficiency degradation due to a hand grip. For a given hand grip, the efficiency degradation is more severe in the higher frequency bands. Therefore the antenna serving the higher frequency band can be located at the top of the phone. The positioning of the antennas can also be arranged to to adjust Specific Absorption Rates or SAR. Antennas located at the bottom of a phone may have lower SAR. If the transmitter power is highest in one band, then the antenna serving the “higher power” band can be located at the bottom of the phone, so that SAR can be reduced to help meet government SAR regulatory requirements. Typically the transmitter power is highest in a low band. Therefore the antenna serving the lower frequency bands can be located at the bottom of the phone.
In yet another aspect of the embodiments herein, a manufacturer or user can select or implement an antenna or antenna arrangement that will be most optimal to a user's patterns of use. The selected antenna can be etched into an extruded housing or otherwise implement to allow the phone to be customized to enhance performance at the frequencies of most interest to a specific customer (or operator). This selection of optimized base antenna structure can preferably be done at the point of sale of the phone. In one embodiment 500 as shown in the flow chart of
Alternatively or optionally, the embodiment 500 can determine the typical areas the customer will use the phone based on collecting data on previous phones or inquiring which locations the customer will use the phone at 503. Based on the usage patterns, a carrier can compare with carrier coverage maps or otherwise determine which frequencies are mostly likely to be used at 505. At decision block 506, an antenna structure can be chosen that provides the best performance for the frequencies of interest. At 508, the optimal antenna chosen can be implemented for example by etching the antenna into the housing. Of course, implementation could also involve predetermined switch settings or tuning as contemplated herein.
Antennas today are optimized to cover multiple bands, and attempt to cover all the bands equally as illustrated by the straight line 604 of the graph 600 of
As noted with respect to
The configurations described herein can primarily provide for a multi-element multi-band internal antenna arrangement that can cover multiple GSM or UMTS bands (850 MHz, 900 MHz, 1700 MHz, 1800 MHz, 1900 MHz for example) and optionally both domestic and International WiMAX bands (2.5 GHz and 3.5 GHz). The arrangement can also cover the 2100 MHz band. Thus, the antenna configurations described can serve as a quad-band GSM dual band WiMax antenna or a Pentaband dual Band WiMax (or BlueTooth) antenna that can also separately include a GPS antenna for reception of GPS signals.
The antenna arrangement(s) can be made either of a sheet metal or can be insert molded using a 2-shot method. The antenna arrangement can comprise of any combination of loop antennas, folded dipoles, transmission lines, PIFA like elements, L-type stubs or other arrangements that provide the desired band operations and the requisite diversity and performance under various hand grip scenarios.
The foregoing embodiments of the antennas illustrated herein provide a multiband antenna design with a wide operating bandwidth where desired. The specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The embodiments herein are defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
The Abstract of the Disclosure is provided to comply with 37 C.F.R. §1.72(b), requiring an abstract that will allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.
U.S. patent application ______, Attorney Docket No. CS36402BLACK356 entitled “Split Band Diversity Antenna Arrangement”, and U.S. patent application ______, Attorney Docket No. CS36276ALBERTH362 entitled “Customized Antenna Arrangement”, both concurrently filed on Jul. 17, 2009 by the same Assignee herein.
