Patent Publication Number: US-2016233944-A1

Title: Rule Based Switchable Polarization

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority under 35 U.S.C. 119 to U.S. Provisional Application Ser. No. 62/113,776, filed Feb. 9, 2015, the entire content of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Aspects of the disclosure relate to wireless communication systems, and, more particularly, to apparatus and methods for switching a polarization of a device based on one or more rules. 
     In wireless communication systems, there is an ever-increasing demand for higher data throughput and reduced interference. In certain frequency bands of operation, such as the Industrial, Scientific, Medical (ISM) bands, 5 GHz, and 60 GHz frequency bands, there exists a high susceptibility to interference from other access points, stations, radio transmitting devices, objects, and/or to changes or disturbances in the wireless link environment. This interference may degrade a wireless link by, for example, causing a polarization of electromagnetic waves to change, contributing to increased packet loss, especially in dense environments. 
     SUMMARY 
     Aspects of the present disclosure are directed to rule based switchable polarization techniques. In one aspect, a device such as a transceiver may receive one or more radio frequency (RF) signals. A packet error rate (PER) associated with the received RF signals (or other indicator of link quality) may be measured or otherwise determined A polarization switching circuit may be provided that is used determine, for example, if the measured PER is greater than a predetermined threshold PER. In response to the determination that the PER is greater than the predetermined threshold PER, the polarization switching circuit may change a polarization of the device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a transceiver having a polarization switching circuit according to an aspect of the present disclosure; 
         FIG. 2  is flow chart illustrating a method for switching a polarization of a device according to an aspect of the present disclosure; and 
         FIGS. 3-6  are exemplary environments employing one or more polarization switching circuits according to aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Certain terminology is used in the following description for convenience only and is not limiting. The words “lower,” “bottom,” “upper” and “top” designate directions in the drawings to which reference is made. Unless specifically set forth herein, the terms “a,” “an” and “the” are not limited to one element, but instead should be read as meaning “at least one.” The terminology includes the words noted above, derivatives thereof and words of similar import. It should also be understood that the terms “about,” “approximately,” “generally,” “substantially” and like terms, used herein when referring to a dimension or characteristic of a component, indicate that the described dimension/characteristic is not a strict boundary or parameter and does not exclude minor variations therefrom that are functionally similar. At a minimum, such references that include a numerical parameter would include variations that, using mathematical and industrial principles accepted in the art (e.g., rounding, measurement or other systematic errors, manufacturing tolerances, etc.), would not vary the least significant digit. 
     Polarization is an important factor for radio frequency (RF) antennae and wireless communications in general. Both RF antennae and electromagnetic waves are said to have a polarization. The polarization of an electromagnetic wave may generally be described as the plane in which the electromagnetic wave vibrates. Because RF antennae may be sensitive to polarization, RF antennae may more effectively receive and transmit signals that have a particular polarization. In many cases, a polarization of an RF antenna may be in the same plane as the radiating elements of the antenna. For example, a vertical antenna (e.g., an antenna with radiating elements that are arranged vertically) may more effectively receive vertically polarized signals, and a horizontal antenna (e.g., one with radiating elements that are arranged horizontally) may more effectively receive horizontally polarized signals. Between horizontal and vertical polarizations, there is a 90 degree range that may be leveraged in the presence of interference using the same channel. 
     Other techniques, such as those used with MIMO architectures, may employ a combination of multiple channels, signal-processing algorithms, and antennas to achieve higher throughput and to decrease bit error rates (BER). Employing these combinations comes at a cost of increased complexity and expense. Further, circular polarization techniques exhibit a 3 dB loss as power is split across two separate planes compared to linear polarization techniques. As such, aspects of the present disclosure may be advantageous at least because aspects described herein may be performed mainly by the RF and antenna portions, resulting in processing simplifications. 
     Aspects of the present disclosure are directed to a packet error rate (PER) rule based electronically switchable polarization device for wireless transceivers. In light of the disclosure, those of skill in the art may appreciate advantages to be had if a transceiver could quickly switch a phased array antenna from operation in one polarization mode to operation in another, different polarization mode, or varying degrees there between. For example, it may be desirable for a phased array to be capable of switching to any one of several different polarizations (e.g., linear vertical, linear horizontal, right-hand circular, left-hand circular, and the like). As an example, in a particular environment, one wireless device may wish to wirelessly communicate information with another wireless device. One or more objects (e.g., obstructions) may introduce a multipath effect causing a polarization of electromagnetic waves (used to carry the desired information) to change. According to aspects of the disclosure, the wireless device designated to receive the information may include a polarization switching circuit that can alter the polarization at which the receiving device receives the signals carrying the information. By switching the polarization, for example by changing the phase and/or gain of radiating elements of a phased array antenna, the receiving wireless device may reduce the PER of the signals it is attempting to receive. 
     As such, according to aspects of the present disclosure, the polarization of an antenna of a wireless transceiver may be adjusted so that a communications link may be maintained with an acceptable PER.  FIG. 1  is a schematic diagram of a wireless transceiver  100  that includes a polarization switching circuit  102  according to an aspect of the disclosure. The wireless transceiver  100  may include an RF/baseband processor  104 , a transceiver sub-circuit  106 , the polarization switching circuit  102 , and an antenna  110 . An output of the RF/baseband processor  104  may be coupled to an input of the polarization switching circuit  102 . An output of the polarization switching circuit  102  may be coupled to an input of the transceiver sub-circuit  106 . The transceiver sub-circuit  106  may include one or more tunable phase shifters/gain controllers  112 , one or more combiner/splitters  114 , and a 90 degree hybrid coupler  116 . The 90 degree hybrid coupler  116  may be cascaded with the antenna  110 . The antenna  110  may take the form of a dual-polarized radiator element having two feed ports  118 ,  120 , each of which may excite an orthogonal polarization component. The dual-polarized radiator element may comprise an array of radiating elements, such as a phased array of radiating elements as discussed above. Examples of such radiators may include, but are not limited to, crossed dipoles, orthogonally fed square waveguides and dual-polarized microstrip patches. Due at least in part to the fact that passive intermodulation (PIM) may be negligible in some frequency bands of operation, such as the ISM, 5 GHz, and 60 GHz bands, the one or more tunable phase shifters/gain controllers  112  may include one or more liquid crystal and/or complementary metal oxide semiconductor (CMOS) phase shifters as known in the art. 
     The transmit or received signals may be weighed with different phases or different magnitudes using the tunable phase shifter/gain controllers  112 . For example, by applying a determined phase and current to one of both of the first feed port  118  and the second feed port  120 , the polarization of antenna  110  may be excited in desired direction. 
     It should be noted that the above described wireless transceiver  100  may be capable of any type of polarization, or any degree thereof, known in the art, and not limited to those discussed above. 
     The RF/baseband processor  104  may process communication signals. For example, during reception, the RF baseband processor  104  may receive combined signals from the antenna  110  via the transceiver sub-circuit  106 , perform down-conversion, demodulation, decoding, and any other known processes to extract information or data conveyed in the received combined signals. On the transmit side, the RF baseband processor  104  may receive data, which may represent voice, data, or control information from a network interface (not shown) and perform encoding, modulation, amplification, up-conversion, and any other known process for transmission of the RF signals through the antenna  110  via the transceiver sub-circuit  106 . The RF/baseband processor  104  may generally be implemented in one or more digital signal processors (DSPs) and/or application specific integrated circuits (ASICs). 
     The polarization switching circuit  102  may include a memory  108  and a polarization switching module  124 . The memory  108  may include gain and phase information in the form of, for example, a table, and may be realized, for example, as RAM memory, flash memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, or any other form of storage medium known in the art. The gain and phase information may include gain and phase settings for desired polarizations. The memory  108  may also include acceptable signal quality characteristics which may include, but are limited to, packet error rate (PER) threshold information. For example, threshold information may represent a ratio at which the PER is deemed to be unacceptable. As another example, the threshold information may represent an unacceptable percentage of packets successfully received by the wireless transceiver  100 , such as a percentage representing a percentage deemed unacceptable by the wireless transceiver  100 . Alternatively, the threshold information may represent a ratio at which the PER is deemed to be acceptable. As another example, the threshold information may represent an acceptable percentage of packets successfully received by the wireless transceiver  100 , such as a percentage deemed to be acceptable by the wireless transceiver  100 . 
     It should be noted that the wireless transceiver  100  may be configured to use any wireless communication scheme known to those skilled in the art, including long range and short range communication protocols such as ZIGBEE, IEEE 802.11 Wi-Fi, BLUETOOTH, infrared and the like. 
     The polarization switching module  124  may query the RF/baseband processor  104 , determine whether received signals are of an acceptable quality (e.g., based on the PER), and switch a polarization mode of the wireless transceiver  100  through control of the phase and/or gain of the transceiver sub-circuit  106  if the received signals are not of acceptable quality. 
     The polarization switching circuit  102  may also include a display (not shown) which may be in the form of a touch-screen display, such that a user can input certain settings or configurations (such as the above described phase/gain settings and PER threshold information) for operation of the polarization switching circuit  102  and/or the wireless transceiver  100 . 
     As shown, the polarization switching circuit  102  is separate from the RF/baseband processor  104 . However, it should be noted that the polarization switching circuit  102  may be realized as a part of the RF/baseband processor  104 . 
       FIG. 2  is a flowchart illustrating a method for setting a polarization of an antenna  110  to reduce a PER of signals in a wireless environment. At block  202 , a signal may be received by the antenna  110 . At block  204 , a PER for the received signal may be determined and, at block  206 , the PER may be compared to an acceptable PER. The acceptable PER may be a predetermined number, ratio or the like. If the determined PER is acceptable (e.g., lower than a threshold PER), at block  208 , a polarization angle of the antenna  110  may be maintained. If the determined PER is outside a preferred range (e.g., greater than the threshold PER), at block  210 , a polarization angle of the antenna  110  may be changed by a predetermined number of degrees θ. For example, if the polarization was vertical, it may be changed by 15 degrees through tuning of the phase shifter/gain controllers  112  as described above. At block  212 , the PER may be checked again to determine if it is acceptable. If acceptable, the polarization angle may be maintained. Otherwise, the polarization angle may be changed by a predetermined number of degrees θ at block  212 . The method may continue until a satisfactory PER is achieved and maintained. The method may monitor the PER for any changes while the wireless communications link is maintained, and change the angle of polarization as needed as described above. The variable number of degrees θ may be as large or small as desired, and may change during operation of the wireless transceiver  100 , for example, to become smaller as the PER improves in order to fine tune the reception. 
       FIG. 3  is an environment (e.g., a conference room)  300  in which the polarization switching circuit  102  may be used. The conference room environment  300  may include one or more wireless devices  302 , one or more of which may include the polarization switching circuit  102 . In some aspects, one or more of the wireless devices  302  may be configured to communicate with other wireless devices and may be referred to as device-to-device (“D2D”) communication devices. A D2D communication device may include a mobile station, as defined by Institute for Electrical and Electronic Engineers (“IEEE”) 802.16e (2005), 802.16m (2009), or subsequent revisions, releases, or updates thereto, or user equipment, as defined by the 3 rd  Generation Partnership Project (“3GPP”) Long Term Evolution (“LTE”) Release 8, Release 9, Release 10, Release 11, Release 12 or subsequent revisions, releases, or updates thereto. The switchable polarization circuit  102  may be implemented in a transmitter, receiver, or both (e.g., transceiver) as a part of wireless device so as to improve the PER of communication signals among users in a conference room or other environment, potentially enabling more users to simultaneously access the same channel. 
     Any communication network or environments described herein may provide for communications in accordance with any wired or wireless communication standard. For example, the communication network can provide for communications in accordance with second-generation (2G) wireless communication protocols IS-136 (time division multiple access (TDMA)), GSM (global system for mobile communication), IS-95 (code division multiple access (CDMA)), third-generation (3G) wireless communication protocols, such as Universal Mobile Telecommunications System (UMTS), CDMA2000, wideband CDMA (WCDMA) and time division-synchronous CDMA (TD-SCDMA), 3.9 generation (3.9G) wireless communication protocols, such as Evolved Universal Terrestrial Radio Access Network (E-UTRAN), with fourth-generation (4G) wireless communication protocols, international mobile telecommunications advanced (IMT-Advanced) protocols, Long Term Evolution (LTE) protocols including LTE-advanced, fifth-generation (5G) wireless communication protocols, or the like. 
     Further, such described networks may be configured to provide for communications in accordance with techniques such as, for example, radio frequency (RF), infrared, or any of a number of different wireless networking techniques, including WLAN techniques such as IEEE 802.11 (e.g., 802.11a, 802.11b, 802.11g, 802.11n, etc.), wireless local area network (WLAN) protocols, world interoperability for microwave access (WiMAX) techniques such as IEEE 802.16, and/or wireless Personal Area Network (WPAN) techniques such as IEEE 802.15, BlueTooth™, ultra wideband (UWB) and/or the like. 
     Referring to  FIG. 4 , multiple users may communicate using the same channel using the same modulation, but with different polarization to their respective offices  402 , for example, in an office setting. 
     Referring now to  FIG. 5 , one or more devices, such as a coordinating device  502  (e.g., a device including a transmitter) may assign different polarization modes for use by respective devices  504 ,  506 ,  508 ,  510  as new devices are added using the same channel. For example, users (e.g., devices) may dynamically switch their respective polarization in the same channel with low packet loss. For example, the coordinating device  502  may determine which polarization direction to select to match the polarization of any of the connecting devices  504 ,  506 ,  508 ,  510 . Such selection may be performed through a handshaking process with one or more of the connecting devices  504 ,  506 ,  508 ,  510 . Such an implementation may be particularly beneficial in dense outdoor or indoor environments such as shopping malls. 
     Referring to  FIG. 6 , another example environment including a network operating at 60 GHz may employ a polarization switching circuit. For example, the polarization switching circuit may be implemented into one or more devices such as a camera, or other device  602  which may transfer raw uncompressed data to another device  604  (e.g., receiver, TV, toy, or the like) at 60 GHz with decreased packet loss due, at least in part, to the ability of one or more of the devices  602 ,  604  to switch its polarization using the above discussed polarization switching circuit. 
     It should be noted that the above discussed environments are by non-limiting example only. Other environments and networks may be contemplated in keeping with the spirit of the present disclosure. 
     Those of skill in the art will understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     Those of skill will further appreciate that the various illustrative blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may 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 artisans may 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 present invention. 
     The various illustrative blocks described in connection with the embodiments disclosed herein may 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 may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., 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. 
     Various embodiments of the invention have now been discussed in detail; however, the invention should not be understood as being limited to these embodiments. It should also be appreciated that various modifications, adaptations, and alternative embodiments thereof may be made within the scope and spirit of the present invention.