Abstract:
Systems and methods for improved Global Positioning System (“GPS”) function employ two multiband, multiport antennas to receive GPS signals. The antennas also serve WiFi frequencies, and the system utilizes the received WiFi signal strength to correct the GPS reception pattern for detuning due to user contact or other factors. The correction is made via selective combination of the GPS signals from the antennas. In addition, a phase shifter in one of the signal paths is used to account for changes in device orientation and to maximize the upper hemisphere component of the GPS reception pattern.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure is related generally to geolocation techniques and, more particularly, to a system and method for enhancing Global Positioning System (“GPS”) antenna performance in a mobile communications device. 
       BACKGROUND 
       [0002]    Cellphone users rely on their devices for a wide range of services every day, from communication to entertainment. Indeed, the cellular infrastructure has expanded to the point that no matter where the user is, there is probably cellular service. However, sometimes the precise location of the user still matters a great deal. 
         [0003]    More than a decade ago, cellphone users acquired the ability to determine their location on the earth&#39;s surface via GPS, and now an entire class of services uses GPS and other location technologies to enhance the user experience. This class of services, referred to as “location-based” services, includes customized search options, navigational assistance, locality-based advertisements and suggestions, and so on. 
         [0004]    Typically, WiFi networks and GPS and are used to provide location data for location-based services. WiFi networks are typically short range, such that a device&#39;s presence on a particular WiFi network serves to roughly resolve the device&#39;s location. For greater accuracy, GPS operates by calculating a device&#39;s location relative to multiple earth-orbiting satellites. 
         [0005]    However, since GPS satellite signals may be attenuated, it is important that a device be able to accurately and reliably capture such signals. For a single GPS antenna on a device, the GPS signal strength is impacted differently by different mechanical modes of use, e.g., free space, head and hand, hand only, etc. Moreover, for consistent performance, GPS Upper Hemisphere Isotropic Sensitivity performance specifications should be met regardless of the mechanical use mode (e.g., both left and right head and hand). 
         [0006]    Typically, however, the location of the GPS antenna on the device is largely determinative of the device&#39;s GPS performance in various orientations and user-handling conditions. While it is possible to implement an antenna placement that balances performance between left and right side of the head, such a solution would necessarily represent a compromise with respect to performance in any given mode. Also, such an antenna placement may interfere with the placement of other antennas. 
         [0007]    It is also possible to employ switched GPS antennas, that is, to use multiple GPS antennas and switch between these antennas based on additional input, e.g., data from an accelerometer. This technique would provide some degree of adaptability of the radiation pattern to suit different usage conditions but would not account for user loading of an antenna. 
         [0008]    While the present disclosure is directed to a system that can eliminate some of the shortcomings noted in this Background section, it should be appreciated that any such benefit is not a limitation on the scope of the disclosed principles, or of the attached claims, except to the extent expressly noted in the claims. Additionally, the discussion of technology in this Background section is reflective of the inventors&#39; own observations, considerations, and thoughts, and is in no way intended to accurately catalog or comprehensively summarize the prior art. As such, the inventors expressly disclaim this section as admitted or assumed prior art with respect to the discussed details. Moreover, the identification herein of a desirable course of action reflects the inventors&#39; own observations and ideas and should not be assumed to indicate an art-recognized desirability. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0009]    While the appended claims set forth the features of the present techniques with particularity, these techniques, together with their objects and advantages, may be best understood from the following detailed description taken in conjunction with the accompanying drawings of which: 
           [0010]      FIG. 1  is a simplified schematic of an example device with respect to which embodiments of the disclosed principles may be implemented; 
           [0011]      FIG. 2  is a physical layout schematic of the device of  FIG. 1  showing antenna placement in keeping with an embodiment of the disclosed principles; 
           [0012]      FIG. 3  is a schematic of a radio-frequency (“RF”) circuit of a multiband, multiport antenna system within which embodiments of the disclosed principles may be implemented, wherein multiple WiFi antennas support GPS frequencies and are deployed to optimize GPS reception; 
           [0013]      FIG. 4  is a flowchart showing an example process of multiband, multiport antenna operation in accordance with an embodiment of the described principles; 
           [0014]      FIG. 5  shows a set of simplified signal-strength plots illustrating the effect of phase-shift steering on GPS signal strength in a free-space condition in accordance with an embodiment of the described principles; and 
           [0015]      FIG. 6  shows a set of simplified signal-strength plots illustrating the effect of phase-shift steering and variable signal combination on GPS signal strength in a hand-held device in accordance with an embodiment of the described principles. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Before presenting a detailed discussion of embodiments of the disclosed principles, an overview of certain embodiments is given to aid the reader in understanding the later discussion. As noted above, GPS signals are often used to assist in identifying a location of a device, so it is important that the device be able to accurately and reliably capture such signals. Moreover, since a user&#39;s manipulation and handling of the device are not predetermined, the device should be able to accurately and reliably capture such signals regardless of the position of the user&#39;s head and hand and regardless of the device orientation. 
         [0017]    GPS signal strength is affected in different ways by different mechanical user modes, e.g., free space, head-and-hand (left or right), hand-only (left or right), and so on. Despite the differing impact of these modes on GPS signal strength, GPS performance specifications should still be met for each mode. In an embodiment of the disclosed principles, signals from two diplexed multiband GPS antennas also supporting WiFi multiple input/multiple output are combined. 
         [0018]    A variable power combiner is used to reduce the impact of an antenna being detuned by user proximity or contact or by the device environment. The GPS signal combining value at any time is based, in an embodiment, on differences in WiFi receiver signal levels for the two antennas, with this difference serving to approximate differences in GPS signal levels. This serves to adapt the system when, for example, the user&#39;s grip blocks one of the antennas. A nominal or default combiner value combines power equally from the two antennas, indicating an unloaded (free-space) condition for the device. In addition, in the absence of WiFi signals, the GPS signal combining value may be set to the default value. 
         [0019]    In a further embodiment, the GPS reception pattern is steered using a variable phase shifter and a variable RF combiner to maximize an upper hemisphere reception pattern (also referred to as the “skyward” pattern). Nominal or zero phase points the reception pattern toward the top of the device. Other phase values steer the radiation pattern laterally away from the device axis so that the pattern is pointed away from the ground based on accelerometer or gyroscope input. 
         [0020]    With this overview in mind, and turning now to a more detailed discussion in conjunction with the attached figures, the techniques of the present disclosure are illustrated as being implemented in a suitable computing environment. The following generalized device description is based on embodiments and examples within which the disclosed principles may be implemented, and should not be taken as limiting the claims with regard to alternative embodiments that are not explicitly described herein. Thus, for example, while  FIG. 1  illustrates an example mobile device within which embodiments of the disclosed principles may be implemented, it will be appreciated that other device types may be used, including but not limited to laptop computers, tablet computers, embedded automobile computing systems, and so on. 
         [0021]    The schematic diagram of  FIG. 1  shows an exemplary device  110  forming part of an environment within which aspects of the present disclosure may be implemented. In particular, the schematic diagram illustrates a user device  110  including several exemplary components. It will be appreciated that additional or alternative components may be used in a given implementation depending upon user preference, component availability, price point, and other considerations. 
         [0022]    In the illustrated embodiment, the components of the user device  110  include a display screen  120 , applications (e.g., programs)  130 , a processor  140 , a memory  150 , one or more input components  160  such as speech and text input facilities, touch screens, sensors (gyroscope, accelerometers, light sensors, etc.), cameras, and one or more output components  170  such as text and audible output facilities, e.g., one or more speakers. 
         [0023]    The processor  140  can be any of a microprocessor, microcomputer, application-specific integrated circuit, or the like. For example, the processor  140  can be implemented by one or more microprocessors or controllers from any desired family or manufacturer. Similarly, the memory  150  may reside on the same integrated circuit as the processor  140 . The memory  150  may be accessed via a network, e.g., via cloud-based storage. The memory  150  may include a random-access memory. The memory  150  may include a read-only memory (i.e., a hard drive, flash memory, or any other desired type of memory device). 
         [0024]    The information that is stored by the memory  150  can include program code associated with one or more operating systems or applications as well as informational data, e.g., program parameters, process data, etc. The operating system and applications are typically implemented via executable instructions stored in a non-transitory, computer-readable medium (e.g., memory  150 ) to control basic functions of the electronic device  110 . Such functions may include, for example, interaction among various internal components and storage and retrieval of applications and data to and from the memory  150 . 
         [0025]    Further with respect to the applications, these typically utilize the operating system to provide more specific functionality, such as file-system service and handling of protected and unprotected data stored in the memory  150 . Although many applications may provide standard or required functionality of the user device  110 , in other cases applications provide optional or specialized functionality and may be supplied by third party vendors or by the device manufacturer. 
         [0026]    With respect to informational data, e.g., program parameters and process data, this non-executable information can be referenced, manipulated, or written by the operating system or by an application. Such informational data can include, for example, data that are preprogrammed into the device during manufacture, data that are created by the device or added by the user, or any of a variety of types of information that are uploaded to, downloaded from, or otherwise accessed at servers or other devices with which the device  110  is in communication during its ongoing operation. 
         [0027]    Although not shown in detail in  FIG. 1 , the device  110  includes software and hardware networking components  180  to allow communications to and from the device  110 . Such networking components provide wireless networking functionality, although wired networking may be supported. In an embodiment, as noted above, the networking components  180  include a GPS antenna system to improve device-location consistency. 
         [0028]    In an embodiment, a power supply  190 , such as a battery or fuel cell, may be included for providing power to the device  110  and its components. All or some of the internal components communicate with one another by way of one or more shared or dedicated internal communication links  195 , such as an internal bus. 
         [0029]    In an embodiment, the device  110  is programmed such that the processor  140  and memory  150  interact with the other components of the device  110  to perform a variety of functions. The processor  140  may include or implement various modules and execute programs for initiating different activities such as launching an application, transferring data, and toggling through various graphical user interface objects (e.g., toggling through various display icons that are linked to executable applications). 
         [0030]      FIG. 2  shows a simplified physical schematic of a device  200  having multiple antennas located in accordance with an embodiment of the disclosed principles. In particular, the device  200  as shown includes three antennas for wireless communication, e.g., via a WiFi medium or cellular medium. These antennas include a first antenna  201 , a second antenna  203 , and a third antenna  205  in the illustrated embodiment. 
         [0031]    In addition, the illustrated device  200  includes a GPS antenna  207 . As may be appreciated, the location of the single GPS antenna makes traditional GPS reception vulnerable to interference by the user&#39;s head or hand or by other elements in the device environment. However, in an embodiment, one or more of the illustrated communications antennas  201 ,  203 ,  205  are used in conjunction with antenna  207  to implement a multiband, multiport antenna system wherein multiple antennas support GPS frequencies and are used to optimize GPS reception. Thus, for example, each of the GPS antenna  207  and the second antenna  203  may be diplexed to interface over WiFi as well as GPS frequencies. With a suitable underlying architecture, as will be discussed in greater detail below, this allows for improved GPS-reception robustness and directionality. 
         [0032]      FIG. 3  shows a multiband, multiport antenna system wherein multiple WiFi antennas support GPS frequencies as well and are used to optimize GPS reception. The illustrated system includes a first multiband antenna  301  and a second multiband antenna  303 . Each multiband antenna  301 ,  303  is configured to support one or more WiFi frequencies (e.g., 2.4 GHz and 5 GHz) as well as appropriate GPS frequencies (e.g., 1575.42 MHz and 1227.60 MHz). 
         [0033]    A respective diplexer  305 ,  307  interfaces each multiband antenna  301 ,  303  to the rest of the illustrated circuit. Each diplexer  305 ,  307  is configured to implement frequency-domain multiplexing. In this way, each multiband antenna  301 ,  303  supports WiFi frequency communications, but incoming GPS signals can be received and routed separately from incoming WiFi data. 
         [0034]    With respect to the diplexers  305 ,  307 , WiFi signals within the circuit are routed to and from a WiFi modem  309 , which is communicatively linked with a main processor  311 . The main processor  311  may be the processor  140  of  FIG. 1  or may be a separate dedicated processor. Moreover, the main processor  311  may comprise a single processor or controller or may comprise multiple such elements. 
         [0035]    As noted above, the diplexers  305 ,  307  route incoming GPS data separately from incoming WiFi data. Incoming GPS data from the first multiband antenna  301  are routed to a variable power combiner  313 , while incoming GPS data from the second multiband antenna  303  are routed first to a variable phase shifter  315  and then to the variable combiner  313 . The combined GPS signal output by the variable combiner  313  is input to a GPS low-noise amplifier  317 , the output of which is provided to the main processor  311  for use in determining the device&#39;s location. 
         [0036]    The operation of the variable combiner  313  and variable phase shifter  315  were described in overview above, and it may be recalled that the variable combiner  313  offsets the detuning of one or both multiband antennas  301 ,  303  based on device environment, while the variable phase shifter  315  steers the GPS reception pattern in the skyward direction based on device orientation. As such, the system illustrated in  FIG. 3  further includes an orientation-measurement unit  319 , which includes an accelerometer or gyroscope (or combination of the two) or other orientation sensor such as a gravitometer. The orientation-measurement unit  319  produces an orientation-related signal which identifies or can be used to derive a device orientation. The orientation-related signal is then input to a sensor processor  321  to form an orientation estimate, which is then provided to the main processor  311  to generate a phase-shift value. 
         [0037]    The operation of the system of  FIG. 3  is shown in greater detail in the flowchart of  FIG. 4 . The process  400  begins at stage  401 , wherein the main processor  311  receives a GPS location request, e.g., from an application. The processor  311  determines a device orientation at stage  403  via the orientation-measurement unit  319 . At stage  405 , the processor  311  derives a phase-shift value based on the determined device orientation. 
         [0038]    The processor  311  determines at stage  407  whether the device&#39;s WiFi facilities are powered on and WiFi signals are being or have been detected within a predetermined time frame such as 10 milliseconds. If the WiFi facilities of the device are not on, or if the WiFi facilities are on but no signal is detected, then the process  400  flows to stage  409 , wherein the processor  311  sets the GPS-combiner value to a default value such as 50% (i.e., the incoming signals are combined equally). Continuing to stage  411 , the processor  311  programs the variable combiner  313  and the variable phase shifter  315  respectively with the combiner value and the phase-shift value. 
         [0039]    Returning to stage  407 , if the processor  311  determines at this stage that the device&#39;s WiFi facilities are powered on and WiFi signals are being or have been detected within the predetermined time frame, then the process  400  flows to stage  413 , wherein the processor  311  determines the WiFi received signal-strength indicator (“RSSI”) at both antennas  301 ,  303  and determines an RSSI-difference value. 
         [0040]    The processor  311  then determines a GPS-combiner value at stage  415  based on the RSSI difference value, e.g., by setting the GPS-combiner value proportional to the RSSI-difference value or from a table or function stored in memory. From stage  415 , the processor  311  programs the variable combiner  313  and the variable phase shifter  315  respectively with the combiner value and the phase-shift value at stage  411 . 
         [0041]    Regardless of whether the process  400  arrived at stage  411  via stage  409  or stage  415 , the processor  311  implements a short delay before proceeding to stage  417 . At this stage, the processor determines whether the GPS location request is still active. If the request is no longer active, then the process  400  terminates. Otherwise, the process  400  returns to stage  403  to reiterate the setting of the variable combiner  313  and the variable phase shifter  315 . 
         [0042]    In this way, the device effectively uses differential WiFi RSSI to mitigate differential antenna detuning and uses phase shifting in concert with orientation detection to steer GPS reception for improved reception. It will be appreciated that the order or details of the illustrated process  400  may be modified without departing from the disclosed principles. For example, orientation detection may occur simultaneously with or even after detuning detection. Similarly, the phase-shift and combiner values may be applied sequentially rather than simultaneously. 
         [0043]    The described principles have been modeled by the inventors and show significant improvement in radiation patterns compared to those of a single GPS antenna as well as compared to the use of multiple GPS antennas without steering or differential tuning  FIG. 5  shows simplified GPS signal-strength plots for a free-space device model illustrating the effect of orientation-based phase shifting on the device&#39;s upper hemisphere GPS reception pattern. The first plot  501  shows GPS signal-strength patterns with the device  200  oriented vertically with respect to its major axis  503 . 
         [0044]    As can be seen, the upper hemisphere pattern  505  dominates and is oriented skyward. There is also a minor lower hemisphere pattern  507 . Less significant portions of the signal-strength pattern emanate horizontally but have been omitted for clarity. In this orientation in free-space conditions, the combiner value is centered ( 50 / 50 ) and the phase-shift value is zero. 
         [0045]    The second plot  511  shows a GPS signal-strength pattern with the same device  200 , except that the device  200  is now oriented 27° from vertical with respect to its major axis  503 . In this orientation, again in free-space conditions, the combiner value is still centered but the phase-shift value has been adjusted to maximize the upper hemisphere pattern. In particular, the phase-shift value has been shifted by 60° from its nominal value. 
         [0046]    As with the first plot  501 , the upper hemisphere pattern  513  of the second plot  511  is substantially vertical, although now it is shifted very slightly in the direction of rotation. The minor lower pattern  515  remains essentially unmoved in the device frame of reference. 
         [0047]    Modeling the radiation pattern of the device  200  in a non-free-space environment shows that the disclosed principles allow mitigation of antenna detuning to some extent as well.  FIG. 6  shows simplified GPS reception-strength patterns illustrating the effect of orientation-based phase shifting and detuning mitigation on the device&#39;s upper hemisphere GPS-reception pattern while the device  200  is hand-held at the user&#39;s ear. 
         [0048]    The upper plot shows a GPS signal-strength pattern  601  modeled while the device  200  is hand-held at the user&#39;s ear (device reference number omitted in this view for clarity). The first plot does not reflect any correction of the GPS pattern via variable combining but does reflect steering of the GPS pattern via phase shifting (nominal minus 60° due to device tilt). The second plot shows the resulting radiation pattern  611  with the device  200  in the same position but with GPS-detuning correction applied in addition to the phase-shift steering. The RSSI-based variable signal combination in this example accounts for the differential effect of the user&#39;s hand and head on the WiFi antennas of the device  200 . 
         [0049]    As can be seen, the phase shift-only pattern  601  exhibits a substantial upper hemisphere component but also includes certain low spots. The addition of correction via variable signal combination based on differential RSSI supplements certain low spots  613 ,  615  in the forward upper direction at the expense of aggravating other low spots  617 ,  619  in the lower and rearward directions. Since the upper hemisphere pattern is the most important for GPS reception, it can be seen that the addition of variable combining serves to improve GPS reception further in addition to the improvement yielded by phase-shift steering. 
         [0050]    It will be appreciated that various systems and processes for improving geolocation-antenna operation have been disclosed herein. However, in view of the many possible embodiments to which the principles of the present disclosure may be applied, it should be recognized that the embodiments described herein with respect to the drawing figures are meant to be illustrative only and should not be taken as limiting the scope of the claims. Therefore, the techniques as described herein contemplate all such embodiments as may come within the scope of the following claims and equivalents thereof. 
         [0051]    Moreover, while the description here is with reference to WiFi and GPS antenna systems, it is not intended to be limited to such. For example, the system could use a long-term evolution cellular system in combination with the GPS location or a WiFi system in combination with directional 5G systems. 
         [0052]    Also, other sensors, e.g., accelerometers, driving-mode detectors, etc., could be used to determine device context, and alternative phase and combiner values can be used to steer the radiation pattern in a different direction than the skyward direction, e.g., in a horizontal plane pointing to a window.