Patent Publication Number: US-2018048193-A1

Title: Method and apparatus for sensing environment and optimizing power efficiency using an antenna

Description:
FIELD OF THE INVENTION 
     This disclosure relates to a device for sensing the environment of a wireless element and more specifically to sensing properties of the environment by measuring electrical characteristics or feedback from the wireless element. 
     BACKGROUND 
     In the wireless power and communications industry, poor battery efficiency in wireless transmission is detrimental to the user experience with those devices. One contributing factor to poor transmission is the changing of the antenna impedance due to the antenna&#39;s environment. Whereas wireless communication devices previously utilized efficient external fixed or extendable antennas or were coupled to remote mounted antennas such as in the case of car phones, most modern wireless communication devices feature internal antennas for aesthetic reasons. The internal placement of the antenna in modern wireless communication devices often results in a pronounced negative impact on the user experience. Similarly, alignment and power transfer between devices having inductive charging capabilities experience inefficiencies due to sub optimal alignment between the inductive resonators or charging coils of the charging device and the device being charged. 
     For example, due to the internal placement of the antenna in modern wireless communication, the impedance of the antenna can change drastically as users alter the way they hold their phone (e.g. from one hand, to both hands, or up to the head). The constantly changing impedance of the antenna leads to energy losses in the transmission and reception of radio signals by the wireless communication device. These losses can be significant and result in severe degradation in battery life of modern wireless communication devices. In extreme cases, holding the wireless communication device in a certain way can cause a total loss of signal potentially resulting in, at best, breaks in call audio transmission and, at worst, the complete dropping of a connection and loss of call audio transmission. 
     Prior attempts to rectify the issues associated with internal antenna placement have not been successful for a variety of reasons. For example, while a complex antenna array may be implemented to improve signal performance, these configurations are expensive both in economic cost, internal phone real estate, and power consumption of the device. Alternatively, wireless communication devices may include additional added in-line circuitry coupled between the antenna and fundamental transmit/receive components. In such cases, while the circuitry may rectify some of the issues associated with antenna performance in a small set of detectable use cases, the circuitry cannot detect all use cases and realized performance gains come at the cost of overall signal degradation introduced by the presence of the circuitry itself to detect the occurrence of a use case. 
     Additionally, prior attempts to rectify issues with inductive charging efficiency primarily include the use of a magnet to aid in optimally aligning the phone with the charger. This solution is hard to scale and still does not prevent the inefficiency when misalignment occurs. There is exists a need to aid in the alignment of inductive chargers and prevent the inefficient use of the energy when the device and charging apparatus is not optimally aligned. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect, this disclosure is related to a method for sensing an environment of an antenna, the method comprising generating a test signal for transmission into the environment of the wireless element. The signal generated outside of a data or power operating frequency of the antenna can then be tested. The feedback from the antenna corresponding to the test signal and the feedback dependent on the environment of the antenna can then be received. A feedback signal for measurement based on the feedback received from the antenna can be provided. Lastly the feedback signal to sense one or more properties of the environment impact on the antenna is measured. 
     In another aspect, this disclosure is related to an inductive charging apparatus comprising at least one inductive resonator, a wireless element, and a feedback sensor comprising a signal generator, a feedback detector, and a coupler. 
     In yet another aspect, this disclosure is related to a wireless communications device comprising: an antenna, and a feedback sensor comprising a signal generator, a feedback detector, and a coupler. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and advantages of this disclosure, and the manner of attaining them, will be more apparent and better understood by reference to the following descriptions of the disclosed system and process, taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1A  is a bock diagram illustrating an example sensing device for sensing the environment of an antenna. 
         FIG. 1B  is a bock diagram illustrating an example sensing device for sensing the environment of a wireless element. 
         FIG. 2A  is a block diagram illustrating an example coupler configuration of a sensing device for providing a feedback signal to a feedback detector for measurement to sense properties of environment impact on a wireless element, such as an antenna or inductive resonator. 
         FIG. 2B  is a block diagram illustrating additional example coupler configurations for providing a feedback signal to a feedback detector for measurement to sense properties of environment impact on an wireless element. 
         FIG. 2C  is a block diagram illustrating additional example coupler configurations for providing a feedback signal to a feedback detector for measurement to sense properties of environment impact on an wireless element. 
         FIG. 2D  is a block diagram illustrating additional example coupler configurations for providing a feedback signal to a feedback detector for measurement to sense properties of environment impact on an wireless element. 
         FIG. 3  is a block diagram illustrating an example feedback detector for measuring a received feedback signal to sense properties of environment impact on a wireless element. 
         FIG. 4  is a block diagram illustrating an example antenna controller for configuring a tunable antenna based on a signature corresponding to sensed properties of an environment of the tunable antenna. 
         FIG. 5  is a flowchart illustrating an example method for sensing an environment of an antenna. 
         FIG. 6  is a flowchart illustrating an example method for adjusting a tunable antenna. 
         FIG. 7  is a diagram of an exemplary embodiment of the present invention including a wireless device equipped with an exemplary embodiment of a feedback detector apparatus and illustration related to portions of the wireless device. 
         FIG. 8  is a diagram of an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The figures and the following description relate to various embodiments by way of illustration only. It should be noted that from the following discussion, alternative embodiments of the structures and methods disclosed herein will be readily recognized as viable alternatives that may be employed without departing from the principles of the embodiments. 
     Reference will now be made in detail to several embodiments, examples of which are illustrated in the accompanying figures. Wherever practicable, similar or like reference numbers may be used in the figures and may indicate similar or like functionality. The figures depict embodiments for purposes of illustration only. 
     Embodiments relate to a sensing device configured to sense the environment of a wireless element, such as an antenna, inductive resonator, or other similar element, in a wireless communications device without impacting data signal integrity. By incorporating a sensing device in the wireless communications device that operates outside the data signal operating frequency(s) of the wireless element, send/receive data signal integrity may be retained while sensing the environment of the wireless element. The sensing device may further use properties of the sensed environment to adjust the configuration of a tunable antenna or other wireless element to decrease signal degradation due to the environment and increase battery life and efficiency of the wireless device. 
     Embodiments also relate to a sensing device configured to sense the environment of a wireless element, such as an antenna, inductive resonator or a coupled inductor, in a wireless power transfer device without impacting power transfer efficiency. By incorporating a sensing device in the wireless power transfer device that operates outside the operating power transfer frequency(s) of the antenna, the power transfer efficiency may be maintained while sensing the environment of the antenna. The sensing device may further use properties of the sensed environment to adjust the configuration of a tunable antenna to increase power transfer efficiency by properly impedance matching the antenna as affected by the environment. Wireless power transfer devices include but are not limited to devices which transmit and/or receive wireless power for the purpose of heating, charging, lighting, and/or powering an external device, object, material, matter, etc. and/or itself. Some example wireless power transfer device applications include battery charging, radio frequency ablation, battery-less electrical circuitry (e.g. passive RFID), etc. The sensing device can also be used to detect misalignment between the devices, such as a phone and inductive charger, to allow a user to ensure optimal alignment for efficient charging or power transfer. 
       FIG. 1A  is a bock diagram illustrating an example sensing device  100  for sensing the environment  118  of a wireless element  112 , such as an antenna  112 . The sensing device  100  is coupled to the antenna  112 , which operates in an environment  118 . 
     In some embodiments, the sensing device  100  is internal to a wireless communication device (not shown) such as a mobile phone or other hand-held device having an antenna  112  (or multiple antennas) enabling wireless communications over WiFi, GSM, CDMA, 2G, 3G, 4G LTE protocols and the like. Accordingly, the antenna  112  may transmit and receive signals carrying wireless communication data such as audio, text, image, video, and the like. Oftentimes, the antenna  112  is incorporated wholly or partially within the enclosure or casing of the wireless communication device. In other instances, the antenna  112  may be aesthetically incorporated as part of the enclosure or casing of the wireless communication device. For example, a surrounding bezel or back-plate of the wireless communication device may include the antenna  112 . 
     In other embodiments, the sensing device  100  is incorporated in a wireless power transfer device. The sensing device  100 , however, operates in a similar fashion to that discussed below with reference to a wireless communication device. Accordingly, while the sensing device  100  is discussed in detail with reference to a wireless communication device, wireless power transfer devices may similarly incorporate a sensing device that operates outside the operating power transfer frequency(s) of an antenna (e.g., similar to operating outside the data signal operating frequency(s) of the antenna) such that the power transfer efficiency may be maintained while sensing the environment of the antenna. 
     Under ideal conditions, such as a wireless communication device operating in a vacuum, the environment  118  of the antenna  112  may include the enclosure or casing of the wireless communication device or other components of the wireless communication device that impact antenna performance. The design and/or placement of the antenna  112  from the factory typically accounts for such considerations. In practice, however, the environment  118  of the antenna  118  changes as a user utilizes the device. For example, different users typically hold the wireless communication device in different ways and a particular user may alter his grip on the wireless communication device, position the wireless communication device against different surfaces such as his face or a table, and/or amongst or in various objects such as in a purse, backpack, room, car, or pocket. The use cases, and other attachments, can present an ever changing environment  118  in which the antenna  112  operates in the wild. Changes in the operating environment  118  of the antenna  112  can impact antenna performance by, for example, altering an impedance of the antenna to different degrees and/or reflecting portions of a transmitted signal back to the antenna. Additionally, amplifier(s) (not shown) in a wireless communication device are designed to achieve optimal efficiency with a specific antenna impedance. Thus, as the environment  118  of the antenna  112  changes and alters the impedance of the antenna, the amplifier(s) may operate less efficiently. The sensing device  100  senses properties of the environment  118  impact on the antenna  112  which may be used to mitigate signal degradation and thus improve battery life of the wireless communication device. 
     As shown, the sensing device  100  may include a signal generator  110 , coupler  114 , and feedback detector  116  to sense properties of the environment  118  in which the antenna  112  is operating. The signal generator  110  is coupled to the coupler  114  and can generate test signals for transmission to the antenna  112  and into the environment  118 . In one embodiment, the signal generator  110  can generate the test signals on frequencies outside the data signal operating frequency(s) and/or wireless power operating frequency band of the antenna  112 . The signal generator  110  may generate a test signal at a discrete frequency, multiple discrete frequencies, or sweep over multiple frequencies. In some embodiments, the test signal generated by the signal generator  110  may be modulated and composed of a range of frequencies. In some embodiments, the sensing device  110  may detect a context of operation of the wireless communication device and the signal generator  110  may generate a test signal of a particular type and more/less frequently based on the context. Example contexts of operator of the wireless communication device may include whether or not the antenna  112  is actively transmitting or receiving data or starting to actively transmit or receive data. The signal generator  110 , in turn, may be configured, for example, to generate a test signal less frequently (or not at all) when the antenna  112  is not actively transmitting data (or inactive), generate a test signal more frequently when the antenna is actively transmitting data, and generate a test signal proximate to when the antenna starts to actively transmit or receive data. 
     The coupler  114  receives the test signals from the signal generator  110  and passes them to the antenna  112  for transmission into the environment  118 . The coupler  114  isolates the antenna  112 , the signal generator  110 , and/or the feedback sensor/detector  116  and passes signals between the various components of the sensor device  100 . In some embodiments, the coupler  114  includes transmission lines coupling the antenna  112 , the signal generator  110 , and/or the feedback sensor  116 . 
     Implementations of the coupler  114  may further include one or more filter(s) (SAW, BAW, discrete components, distributed components, single inductors, single capacitors, etc.) coupled to or between the antenna  112 , the signal generator  110 , and/or the feedback sensor  116  or otherwise incorporated into the coupler  114  in order to isolate the components of the sensor device  100  from the antenna  112  at the data signal operating frequency(s) of the antenna  112 . Examples of filter(s) that may be implemented in the coupler  114  may include a bandstop, bandpass, notch, low-pass, high-pass filter(s), etc., or a combination thereof, in order to pass the test signal frequency(s) and isolate the data signal operating frequency(s) of the antenna  112  and/or isolate frequencies outside the test frequency(s). In some embodiments, the coupler  114  could include impedance matching circuitry. The impedance matching circuitry may be utilized to improve the sensor&#39;s sensitivity to environment changes at test signal frequency(s) and/or to allow the setting of specific feedback signal(s) for specific environments. 
     Additionally, in some embodiments, the coupler  114  may be coupled to the antenna  112  at a physical location on the antenna  112  to improve isolation of the sensor device  100  to the data signal operating frequency(s) of the antenna. In some embodiments, the coupler  114  couples the signal generator  110  to the feedback detector  116  along two paths, one coupled to the antenna  112  and one isolated from the antenna  112 . Alternatively or additionally, in some embodiments, the coupler  114  may include directional couplings between the antenna  112  and sensor device  100  components to separate the paths of a test signal for transmission and feedback received from the antenna  112 . Embodiments of the coupler  114  may include additional or alternate components to couple the signal generator  110 , the antenna  112 , and/or the feedback detector  116 . 
     The coupler  114  further receives feedback from the antenna  112  associated with the test signals passed to the antenna and transmitted into the environment  118 . More specifically, proximate to when the coupler  114  passes a test signal to the antenna  112  for transmission, feedback associated with the test signal is subsequently received at the coupler  114 . The feedback received at the coupler  114  varies depending on the generated test signal, the antenna  112 , and the environment  118 . 
     Considering a given test signal and antenna  112 , feedback received at the coupler  114  may vary as a result of an altered impedance of the antenna and/or portions of the test signal reflected back to the antenna due to the environment. For example, when the environment close to the antenna  112  (e.g., hand position on the wireless communication device) changes, an impedance of the antenna may change. In another example, when the environment “far” from the antenna  112  (e.g., position in a room, car or, bag the wireless device is operated in and size and/or composition of different rooms, cars or, bags) changes, reflections received at the antenna may occur or change. 
     Further, considering a given environment  118  and antenna  112 , feedback received at the coupler  114  may vary based on the test signal. For example, as two (or more) different environments may result in similar feedback for a given test signal (e.g., at one frequency), by generating another test signal at a different discrete frequency or the initial test signal at multiple discrete frequencies or to sweep over multiple frequencies feedback may be varied to distinguish between the different environments. 
     Additionally, in embodiments comprising a tunable antenna, considering a given test signal and environment  118 , feedback received at the coupler  114  may vary based on the configuration of the antenna. Hence, the configuration of the tunable antenna may be adjusted to compensate based on feedback. 
     Embodiments of the coupler  114  pass one or more feedback signals based on the feedback received from the wireless element  112  to the feedback detector  116 . For example, the coupler  114  may receive feedback corresponding to a test signal and pass a feedback signal comprising significantly unaltered feedback. In another example, the coupler  114  may receive feedback corresponding to a test signal and pass a feedback signal comprising filtered feedback. In yet another example, the coupler  114  may receive feedback corresponding to a test signal and pass a feedback signal comprising the test signal superimposed with the received feedback. Configurations of the coupler  114  may perform one or more of these operations to pass feedback signals to the feedback detector  116 . In some embodiments, the coupler  114  may additionally pass received test signals generated by the signal generator  110  to the feedback detector  116  (prior to, and/or subsequent to any filtering performed at the coupler  114 ). In other embodiments, the signal generator  110  may pass the generated test signals to the feedback detector  116 . 
     The feedback detector  116  receives one or more feedback signals and/or a test signal and processes one or more of the received feedback signals to sense properties of the environment  118  impact on the antenna  112 . For example, the feedback detector  116 , which is described in more detail with reference to  FIG. 3 , may measure a feedback signal directly and/or by performing one or more comparisons between the feedback signal and/or a test signal and/or a corresponding feedback signal to sense properties of the environment  118  impact on the antenna  112 . 
       FIG. 1B  is a block diagram illustrating a capacitive or inductive charging apparatus  100  for sensing the environment  118  of an inductive resonator  112 . The sensing device  100  is coupled to the inductive resonator  112 , which operates in an environment  118 . As described above this exemplary embodiment operates similar to the sensing device shown in  FIG. 1A . The charging apparatus can sense when an apparatus such as a phone is placed on a charging pad and is not optimally aligned to the inductive resonator which can result into inefficient transfer of energy. The charging apparatus  100  can be used to ensure optimal alignment and/or prevent inefficient transfer of energy between the inductive resonator and the device. In one exemplary embodiment, the coupler can be a capacitor to tune the circuit to the appropriate frequency. 
       FIG. 2A  is a block diagram illustrating an example coupler  214 A configuration of a sensing device  200  for providing a feedback signal  211  to a feedback detector  116  for measurement to sense properties of environment  118  impact on an antenna  112 . 
     As shown, the signal generator  110  may generate a number of different test signals. For example, the signal generator  110  may generate a test signal  203  at a discrete frequency  201 A, multiple discrete frequencies  201 B, or a sweep(s) of frequencies  201 C. In some embodiments, the signal generator  110  may generate a modulated test signal  203  composed of a range of frequencies. The signal generator  110  transmits the generated test signal  203  to the coupler  214 A. In one embodiment, the signal generator  110  generates the test signals  201 A,  201 B,  201 C at frequencies outside the data signal operating frequency(s) and/or wireless power operating frequency band of the antenna  112 . 
     In the illustrated embodiment, the coupler  214 A passes the test signal  205  to the antenna  112  and passes the test signal  207  to the feedback detector  116 . The coupler  214 A receives feedback  209 , as a result of the impedance of the antenna and/or portions of the test signal reflected back to the antenna due to the environment, from the antenna  112  in response to the test signal  205 . The coupler  214 A, in turn, passes a feedback signal  211  based on the received feedback  209  to the feedback detector  116 . The feedback signal  211  may be passed directly and comprise significantly unaltered feedback  209  from the antenna  112 . In other embodiments, the coupler  214 A may filter the feedback  209  and pass a feedback signal  211  comprising filtered feedback to the feedback detector  116 . 
     The feedback detector  116  measures the feedback signal  211  to sense properties of the environment  118  of the antenna  112 . In the illustrated embodiment, the feedback detector  116  receives the test signal  207  and the feedback signal  211  from the coupler  214 A. Accordingly, the feedback detector  116  may measure the feedback signal  211  directly and/or perform one or more comparisons between the feedback signal  211  and the test signal  207 . 
     In other embodiments, such as those illustrated in  FIGS. 2B-D , the coupler may pass other combinations and/or different signals to the feedback detector  116  for measurement. 
       FIG. 2B  is a block diagram illustrating an example coupler  214 B configuration for providing a feedback signal  211  to a feedback detector for measurement to sense properties of environment impact on an antenna. Coupler  214 B may be incorporated into the sensing device  200 . 
     In the illustrated embodiment, the coupler  214 B receives a test signal  203  from a signal generator. The coupler  214 B passes the test signal  205  to an antenna and passes the test signal  207  to a feedback detector for measurement. The coupler  214 B receives feedback  209 , as a result of the impedance of the antenna and/or portions of the test signal reflected back to the antenna due to the environment, from the antenna in response to the test signal  205 . The coupler  214 B superimposes  220  the test signal  205  with the feedback  209  received from the antenna to form a feedback signal  211  based on the received feedback  209 . In turn, the coupler  214 B passes the feedback signal  211  to the feedback detector for measurement. 
     Thus, the feedback detector receives the test signal  207  and the feedback signal  211  from the coupler  214 A. Accordingly, the feedback detector may measure the feedback signal  211  directly and/or perform one or more comparisons between the feedback signal  211  and the test signal  207 . 
       FIG. 2C  is a block diagram illustrating an example coupler  214 C configuration for providing a feedback signal  211  to a feedback detector for measurement to sense properties of environment impact on an antenna. Coupler  214 C may be incorporated into the sensing device  200 . 
     In the illustrated embodiment, the coupler  214 C receives a test signal  203  from a signal generator. The coupler  214 C passes the test signal  205  to an antenna for transmission. The coupler  214 C receives feedback  209 , as a result of the impedance of the antenna and/or portions of the test signal reflected back to the antenna due to the environment, from the antenna in response to the test signal  205 . The coupler  214 C superimposes  220  the test signal  205  with the feedback  209  received from the antenna to form a feedback signal  211  based on the received feedback  209 . In turn, the coupler  214 C passes the feedback signal  211  to the feedback detector for measurement. 
     Thus, the feedback detector receives the feedback signal  211  from the coupler  214 A. Accordingly, the feedback detector may measure the feedback signal  211  directly to sense properties of environment impact on the antenna. In some embodiments, the signal generator may pass the test signal  203  to the feedback detector such that the feedback detector may perform one or more comparisons between the feedback signal  211  and the test signal  207 . 
       FIG. 2D  is a block diagram illustrating an example coupler  214 D configuration for providing a feedback signal  211  to a feedback detector for measurement to sense properties of environment impact on an antenna. Coupler  214 D may be incorporated into the sensing device  200 . 
     In the illustrated embodiment, the coupler  214 D receives a test signal  203  from a signal generator. The coupler  214 D passes the test signal  205  to an antenna for transmission. The coupler  214 B receives feedback  209 , as a result of the impedance of the antenna and/or portions of the test signal reflected back to the antenna due to the environment, from the antenna in response to the test signal  205 . The coupler  214 D, in turn, passes a feedback signal  211  based on the received feedback  209  to the feedback detector. The feedback signal  211  may be passed directly and comprise significantly unaltered feedback  209  from the antenna. In other embodiments, the coupler  214 D may filter the feedback  209  and pass a feedback signal  211  comprising filtered feedback to the feedback detector. 
     Thus, the feedback detector receives the feedback signal  211  from the coupler  214 A. Accordingly, the feedback detector  116  may measure the feedback signal  211  directly to sense properties of environment impact on the antenna. In some embodiments, the signal generator may pass the test signal  203  to the feedback detector such that the feedback detector may perform one or more comparisons between the feedback signal  211  and the test signal  207 . 
       FIG. 3  is a block diagram illustrating an example feedback detector  116  for measuring a received feedback signal  211  to sense properties of environment impact on an antenna. As shown, embodiments of the feedback detector  116  may receive a test signal  207  in addition to the feedback signal  211  for performing measurements. In the illustrated embodiment, the feedback detector  116  includes a phase detector  305  and a magnitude detector  310 . Other embodiments of the feedback detector  116  may include one or both of the detectors  305 ,  310  and/or other types of detectors such as a comparator, zero-crossing, and/or window detector. 
     The phase detector  305  receives the test signal  207  and the feedback signal  211  and senses the environment  118  of the antenna  112  by detecting a difference in phase between the test signal and the feedback signal. For example, the phase detector  305  may generate an output voltage when the phase between the test signal and the feedback signal differ using well known analog or digital circuitry configurations, such as those suitable for use in a Phase-Locked Loop (PLL). A detected difference in phase between the test signal and the feedback signal may be indicative of a change in impedance of the antenna and/or that portions of the test signal are reflected back to the antenna due to the environment. 
     In one embodiment, the phase detector  305  generates an output voltage representative of the degree to which the phase between the test signal and the feedback signal differs. For example, the phase detector  305  may generate the output voltage representative of the difference in phase between the test signal and the feedback signal using well known analog or digital circuitry configurations, such as those suitable for use in a PLL. A change in antenna impedance and/or change in the portions of the test signal reflected back to the antenna due to the environment will cause corresponding changes in the received feedback signal  211  and thus the measured phase difference between the test signal  207  and the feedback signal  211 . The measured phase difference may be used to differentiate between different operating environments of the antenna. For example, certain environments may exhibit a high degree of difference in phase between the test signal and the feedback signal while others exhibit a minimal degree of difference in phase between the test signal and the feedback signal. 
     In some instances, the phase difference at one test frequency may be different than the phase difference at another test frequency in an environment. Because multiple environments may correspond to a feedback signal  211  and test signal  207  having the same (or similar) phase difference at one frequency, generation of test signals at different frequencies and/or comprising multiple frequencies may be performed (e.g., by a signal generator) such that the phase detector  305  may measure the phase difference between a test signal  207  and feedback signal  211  at multiple frequencies or sweeps of frequencies to allow improved discrimination between environments. 
     The phase detector  305  may output the detected difference in phase between the test signal  207  and the feedback signal  211  to a tunable antenna controller for altering a configuration of the antenna  112  to account for the sensed environment  118 . An embodiment of an antenna controller is described in more detail with reference to  FIG. 4 . 
     In one embodiment, the magnitude detector  310  receives the test signal  207  and the feedback signal  211  and senses the environment  118  of the antenna  112  by detecting a difference in magnitude between the test signal and the feedback signal. For example, the magnitude detector  310  may generate an output voltage when the magnitude of the feedback signal exceeds that of the test signal (or vice versa) using well known analog or digital circuitry configurations, such as an operational amplifier comparator. 
     In another embodiment, the magnitude detector  310  may measure a difference in magnitude between the feedback signal and a reference signal (or voltage) and/or an absolute magnitude of the feedback signal. In such cases, the test signal  207  need not be provided to the magnitude detector  310 . 
     In some embodiments, the test signal input levels and/or the feedback signal input levels are adjusted and/or filtered prior to input into the magnitude detector  310 . For example, the level of a signal may be increased (e.g., using an amplifier) or decreased (e.g., using a voltage divider) prior to measurement of the feedback signal and/or comparison of the feedback signal with the test or reference signal to adjust a sensitivity of the measurement and comparison, respectively. Alternatively, or in addition, the signal may be passed through a filter. For example, the magnitude detector  310  may incorporate a filter to limit the frequencies of the test signals and/or feedback signals (e.g., to the range of frequencies outside the data signal operating frequency(s) and/or wireless power operating frequency band of an antenna. At least one filter can be used to eliminate the detectability of the RF system completely. This essentially makes the RF system disappear from recognition. The filter(s) can be used to filter the feedback signal  203  as well as the test signal  205 , among others. 
     A detected difference in magnitude between the test or reference signal and the feedback signal and/or an absolute magnitude (based on changes thereof) of the feedback signal may be indicative of a change in impedance of the antenna and/or that portions of the test signal are reflected back to the antenna due to the environment. 
     In one embodiment, the magnitude detector  310  generates a voltage representative of the degree to which the magnitude between the reference or the test signal and the feedback signal differ. For example, the magnitude detector  310  may generate the output voltage representative of the difference in magnitude between the test signal and the feedback signal by presenting an envelope detection voltage for each of the signals. The envelope detector detects the envelope power level of the test signal and/or the feedback signal using well known analog or digital circuitry configurations, such as a diode detector, and generates an output voltage corresponding to the magnitude of the test signal and/or feedback signal. A voltage representative of the degree to which the magnitude between the test signal and the feedback signal differ is output based on the difference of the two envelope detection voltages. A voltage representative of the degree to which the magnitude between the reference signal and the feedback signal differ is output based on the difference of the envelope detection voltage of the feedback signal and the reference voltage. A voltage representative of the magnitude of the feedback signal may be output directly. 
     A change in antenna impedance and/or change in the portions of the test signal reflected back to the antenna due to the environment will cause corresponding changes in the received feedback signal  211  and thus the measured amplitude difference between the reference or test signal  207  and the feedback signal  211  or the absolute magnitude of the feedback signal  211 . 
     The measured magnitude difference or absolute magnitude (based on changes thereof in the feedback signal) may be used to differentiate between different operating environments of the antenna. For example, certain environments may exhibit a high degree of difference in magnitude or large magnitude of the feedback signal and other environments may exhibit a minimal degree of difference in magnitude or minimal magnitude of the feedback signal. 
     In some instances, the magnitude difference or absolute magnitude of the test signal at one test frequency may be different at another test frequency. Because multiple environments may correspond to a same (or similar) magnitude difference or absolute magnitude at one frequency, generation of test signals at different frequencies and/or comprising multiple frequencies may be performed (e.g., by a signal generator) such that the magnitude detector  310  may measure the magnitude difference or absolute magnitude at multiple frequencies or sweeps of frequencies to allow improved discrimination between environments. 
     The magnitude detector  310  may output the detected difference in magnitude between the reference or test signal and the feedback signal and/or the absolute magnitude of the feedback signal to an antenna controller for altering a configuration of the antenna  112  to account for the sensed environment  118 . An embodiment of an antenna controller is described in more detail with reference to  FIG. 4 . 
       FIG. 4  is a block diagram illustrating an example antenna controller  400  for configuring a tunable antenna  412  based on a signature  411  corresponding to the sensed properties of the environment  118  of the tunable antenna. As shown, the antenna controller  400  includes a signature generator  405  for generating a signature corresponding to the sensed properties of the environment  118 , a signature mapping table  410  for performing a lookup of the signature to determine a corresponding antenna state, and an antenna state configurator  415  for placing the tunable antenna  412  in the corresponding antenna state. The tunable antenna  412  could be an antenna which has tunable electrical properties. Alternatively the tunable antenna  412  could be an antenna which itself has static electrical properties, but for which circuitry within the device&#39;s operating data signal path is tunable (e.g. tunable matching network(s), tunable filter(s), tunable amplifier(s), etc.). The tunable antenna  412  could also be a combination of both an antenna which has tunable electrical properties and an antenna for which circuitry within the device&#39;s operating data signal path is tunable. 
     In one embodiment, the antenna controller  400  is incorporated in the sensing device  100  illustrated in  FIG. 1 . In another embodiment, the antenna controller  400  may be completely separate or partially separate from the sensing device  100  illustrated in  FIG. 1 . The antenna controller  400  is coupled to the feedback detector  116  of the sensing device and receives signals  401  describing sensed properties of the environment  118  of the tunable antenna  412  output by the feedback detector  116 . The antenna controller  400  processes the received signals  401  to determine a best antenna state and transmits instructions  403  to the tunable antenna  412  to configure the tunable antenna  412  to the desired antenna state. 
     The signature generator  405  receives the signals  401  describing sensed properties of the environment  118  of the tunable antenna  412  and generates a signature corresponding to the environment  118  based on the sensed properties. Example signals  401  output from the feedback detector  116  and received by the signature generator  405  may include a voltage indicative of a difference in magnitude between a reference or test signal and a feedback signal, a change in the magnitude of the feedback signal, and/or a voltage indicative of a difference in phase between a test signal and a feedback signal. Additionally, a voltage level of a received signal  401  may indicate the degree to which the magnitude or phase of the signals differ and/or the absolute magnitude of the feedback signal. The signature generator  405  generates a signature based on a presence (and/or a level) of the voltage indicative of a difference in magnitude between a reference or test signal and a feedback signal, the voltage indicative of the magnitude of the feedback signal, and/or the voltage indicative of a difference in phase between a test signal and a feedback signal. The signature generator  405  can also account for the different voltages levels at various frequencies when determining the signature. 
     In one embodiment, the signature generator  405  comprises one or more analog to digital converters which convert the received signals  401  into digital data which can be utilized in software to create a signature. For example, the signature could be an array of magnitude, magnitude difference, and/or phase difference voltages at various frequencies along with a current antenna state and data signal frequency or band: e.g. [M(f 1 ),P(f 1 ),M(f 2 ),P(f 2 ),A,fd] where M and P are magnitude and phase difference voltages, respectively, at f 1  and f 2 , two test signal frequencies, A is the current antenna state, and fd is the frequency or band of the data signal. In one implementation, the signature generator  405  may perform multiple successive complete signature generations based on multiple successive signals  401  describing sensed properties of the environment  118  of the tunable antenna  412  and average the successive signatures to generate one signature with decreased noise. The signature generator  405  outputs the generated signature for lookup in the signature mapping table  410 . 
     The signature mapping table  410  includes a number of signatures  411  and their corresponding antenna states  413  that provide best antenna performance. In one embodiment, the signature mapping table  410  is constructed during development of the wireless communications device by, for example, placing the wireless communication device in a given environment, sensing properties of the given environment (i.e., with the sensing device  100 ), sweeping antenna states, generating a signature  411  (i.e., Sig′) based on the sensed properties, and testing which antenna state (i.e., State A) provides the best performance in each data signal frequency or band. By placing the wireless communication device in different environments  118  and antenna states in this manner, different signatures (i.e., Sig′, Sig″, etc.) can be generated and each matched to a best antenna state (e.g., State A, State B, etc.). 
     In some embodiments, the signature mapping table  410  may be populated with signatures generated during the course of operation of the wireless communication device by testing possible states of the tunable antenna  412  against a given signature to determine which state produces the best results. Thus, for example, if a generated signature differs from the signatures stored in the mapping table  410 , a best antenna state may be determined. In some embodiments, for a signature not found in the mapping table  410 , an objective function of the generated signature and the mapping table signatures  411  may be optimized to determine a corresponding signature in the mapping table. In turn, the antenna state mapped to the corresponding signature, which optimizes the objective function, may be stored in association with the generated signature as a new entry in the mapping table  410 . 
     During wireless communication device operation, the signature mapping table  410  is queried with a generated signature (e.g., by the signature generator  405 ) and performs a lookup in the table to find a best matching test signature  411  stored in the table. In turn, the signature mapping table  410  outputs the antenna state  413  (e.g., to the antenna state configurator  415 ) corresponding to the best matching test signature  411 . 
     The antenna state configurator  415  receives antenna state  413  information from the signature mapping table  410  and transmits instructions  403  to the tunable antenna  412  to configure the tunable antenna  412  to the desired state. In turn, the tunable antenna  412  operates in an antenna state best suited to the sensed environment  118  to improve performance and/or increase battery life of the wireless communication device. 
       FIG. 5  is a flowchart illustrating an example method for sensing the environment of an antenna. As a user utilizes a wireless communication device, the environment presented to an antenna of the wireless communication device may change as the user alters their grip on the wireless communication device, positions the wireless communication device against different surfaces such as their face or a table, and/or amongst various object such as in a purse, backpack or pocket. These changes in the environment can affect antenna performance and negatively impact battery life of the wireless communication device. A sensing device, such as that illustrated in  FIG. 1 , may be used to sense properties of the operating environment of the antenna. 
     To sense properties of an operating environment of a wireless element, such as an antenna or inductive resonator, a signal generator generates  505  a test signal for transmission to a wireless element and into an environment of the wireless element. The signal generator may generate  505  the test signal at a discrete frequency, multiple discrete frequencies, or sweep over multiple frequencies outside the data signal operating frequency(s) and/or wireless power operating frequency band of the wireless element to prevent interference with data transmit/receive operations of the wireless element. In some embodiments, the test signal is modulated. 
     A coupler isolating the wireless element from the signal generator receives the test signal and passes the test signal for transmission into the environment to the wireless element. The coupler receives  510  feedback corresponding to the test signal from the wireless element. The received feedback depends on the environment of the wireless element as the environment alters an impedance of the wireless element to different degrees and/or reflects portions of the test signal transmitted by the wireless element back to the wireless element. 
     The coupler isolates the wireless element from a feedback sensor and provides  515  a feedback signal based on the feedback received from the wireless element to the feedback sensor. Additionally, the coupler may isolate the signal generator from the feedback sensor and passes the received test signal to the feedback sensor. 
     The feedback sensor measures  520  the feedback signal to sense properties of the environment impact on the wireless element. 
     In one embodiment, the feedback sensor receives the test signal and the feedback signal and senses properties of the environment impact on the wireless element by comparing  520 A the signals to measure differences between the test signal and the feedback signal. For example, the feedback sensor may measure a detected difference in phase and/or magnitude between the test signal and the feedback signal. The feedback sensor may alternatively utilize a reference signal instead of the test signal to measure a detected difference in magnitude. 
     In another embodiment, the feedback sensor receives the feedback signal and senses properties of the environment impact on the wireless element by measuring  520 B an absolute magnitude (or changes thereof) of the feedback signal to detect changes in the magnitude of the feedback signal. 
     In some embodiments, the feedback sensor generates a voltage level corresponding to the absolute magnitude (or changes thereof) of the feedback signal and/or degree to which the measured phase or magnitude of the test signal and the feedback signal differ. The feedback sensor may output the voltage level to an antenna controller for processing to adjust a wireless element state of a tunable antenna based on sensed properties of the environment of the wireless element. 
       FIG. 6  is a flowchart illustrating an example method for adjusting a tunable antenna. Detected differences between a test signal and a feedback signal based on sensed properties of an environment of a tunable antenna and/or absolute magnitude (or changes thereof) may be processed to configure the tunable antenna to an antenna state best suited for the environment. An antenna controller, such as that illustrated in  FIG. 4 , may be used to adjust the tunable antenna. 
     To adjust a tunable antenna, a signature generator receives  605  one or more signals describing sensed properties of an environment of the tunable antenna. Example received  605  signals comprise a voltage indicative of an absolute magnitude (or changes thereof) of a feedback signal, a difference in magnitude between a test signal and a feedback signal, and/or a voltage indicative of a difference in phase between a test signal and a feedback signal. A voltage level of a received  605  signal may indicate the degree to which the magnitude or phase of the test signal and the feedback signal differ or the absolute magnitude (or changes thereof) of the feedback signal. 
     The signature generator generates  610  a signature based on the one or more signals describing sensed properties of the environment of the tunable antenna and outputs the generated signature. 
     A signature mapping table receives the generated signature and then matches  615  the generated signature with a test signature stored in association with a best antenna state for the tunable antenna in the environment in the signature mapping table. The signature mapping table outputs the best antenna state for the tunable antenna in the environment. 
     An antenna state configurator receives the best antenna state and transmits  620  instructions to the tunable antenna to configure the tunable antenna to the best antenna state to increase one or more of antenna performance and battery life of a wireless communication device. 
     In another exemplary embodiment, the feedback sensor apparatus can have a plurality of antennas and a plurality of feedback detectors. Each antenna can have a corresponding dedicated feedback detector. 
     The feedback detector apparatus has a large scope of applications and system that it can be incorporated into, thereby providing greater functionality to the system as well as improving the efficiency of the device or system. In one exemplary embodiment, the feedback detector apparatus can be incorporated into a wireless device, such as a cellular phone. The feedback detector apparatus can then take measured information and direct the cellular phone to improve the impedance mismatch by impedance matching the wireless element, such as an antenna of the cellular device, thereby constantly impedance matching as said phone is manipulated or moved in space. This constant impedance matching is necessary due to different environmental changes that the phone is traveling through. 
     For example, as a user is operating the phone at a given position, they may be moving throughout a structure or change how they are holding the phone. These changes create different impedances related to the wireless element, such as an antenna and must be accounted for in real time to ensure that the device or phone can operate efficiently. This not only increases the efficiency of power consumption by the devices and increases the battery life of the device, but also can affect the efficiency on a larger cellular infrastructure scale. Because the device is able to optimally sense and transmit information to the network, fewer cellular towers are needed per area to provide the same reception to users. 
     As previously noted, a feedback sensor apparatus can produce at least one output based on measurement of the feedback signal associated with the test signal at the first frequency and a second output based on a measuring of a second feedback signal associated with the second test signal at the second frequency. In this embodiment, the first output and the second output for discriminating between a first environment and a second environment have a similar feedback response at the first frequency and a distinct feedback response at the second frequency. 
     In one embodiment, the tunable antenna and antenna controller of the feedback sensor apparatus can, in addition to configuring the tunable antenna to an antenna state best suited for the environment, be used to provide greater functionality to a device, such as a cell phone. Many phones have limited space on the external portion of the device for ancillary buttons to operate features of the phone, such as the power button, volume controls, and the menu button among others. Integrating the feedback sensor apparatus with the phone can provide greater functionality to an already existing phone without the need of additional external buttons. Additionally, the feedback sensor apparatus can effectively operate as a replacement for external control buttons or switches. This can allow cellular phone manufacturers the ability to eliminate external buttons/switches from the phone. This can aid in the manufacturing process, increase durability and weather resistance, as well as providing greater ability to make a phone thinner. 
     As shown in  FIG. 7 , in one exemplary embodiment, an apparatus  700  can include a feedback sensor communicatively coupled to a mobile device  701 , such as a cellular phone. The mobile device can include a microprocessor, memory, and data bus. The mobile device can further include a display. The apparatus  700  can include a signal generator  710 , a coupler  714 , a feedback detector  716 , and an antenna controller or tuner  705 , similar to that shown in  FIG. 4 . The feedback detector  716  can analyze at least one sensor output  707  and compare the sensor output(s)  707  to a table of lab-measured outputs, stored in a signature mapping database  722 . The database  722  can be stored on a memory, such as memory found in the mobile device  701  or an external or cloud memory communicatively connected to the mobile device  701 . The table of lab-measured outputs can be mapped to correlate to one or more distinctive locations  724  on the mobile device, essentially creating a fingerprint for the device  701 . Each distinctive location  724  can be associated with an optimal matching network configuration to minimize the impedance mismatch between the antenna  703  and the radio subsystem. This can reduce the amount of power needed for proper operation of the radio system, saving power, extending battery life, and thus extending the life of the device. 
     Additionally, the measured distinctive location  724  can be compared to a table of lab measured cases in the signature mapping database  722  that are correlated to various finger or hand positions a user might implement around the exterior of the device in positional relationship to the antenna  703 . The feedback sensor apparatus  700  can be used to monitor how these positions change over time and in real time while the mobile device  701  is in operation. In combination with a manometer and accelerometer, the apparatus  700  can determine the orientation of the mobile device  701  and anticipate the use of the phone by the user, such as determining whether the device  701  is being held up to a user&#39;s ear or a user is typing or texting on the phone. This information can be used to determine whether to activate the additional functionality to the device  701  provided by the apparatus  700 . These finger and hand positions can be mapped and correlated to the outputs  707  from the feedback detector  716  and antenna controller  705 , and thus made functional. Different sequences of hand and finger positions can be distinguished by the feedback detector  716  apparatus and then communicate with the device to perform a certain functions based on the outputs  707 . 
       FIG. 7  further illustrates how distinctive locations  724  using finger and hand positions can be used to provide additional function to the device. For example, the antenna  703  of the feedback sensor  700  can sense a user swiping across the external edge of the device  701 . This can be used to turn the volume up or down depending upon the desired functionality. Alternatively it could be used to adjust the brightness or contrast of the screen. Similarly, buttons can essentially be created without the need of a physical button to be present. These different finger positions along the external antenna or the exterior of the mobile device  701  can be correlated to various functions of the phone including but not limited to use as passwords or access keys, quick keys or hot keys for designated functions, as well as other functionality desired by a user. 
     Similarly, another exemplary embodiment of the present invention includes an optional feedback detector communicatively coupled with inductive resonators  113 , as shown in  FIG. 1B . This embodiment includes an inductive charging apparatus having greater efficiency when charging a device or a power source, such as a battery for a device. The inductive charging apparatus using the feedback sensor can further comprise a resonator that operates outside the operating range or frequency band of the antenna to prevent interference or affect the functionality of the antenna. In one exemplary embodiment, the inductive charging apparatus comprising the feedback sensor which only measures the magnitude difference between the test signal and the feedback signal and is not concerned with the phase between the two signals. This inductive charging apparatus can be used for a variety of applications, including charging phones or battery powered and hybrid cars. The primary advantage that the feedback sensor provides is the ability to accurately identify the alignment of the inductive charging apparatus with the targeted device that is to be charged. In many applications, a misalignment between the inductive charging source and the target results in inefficient charging and the wasting of power. This inefficiency often generates excessive heat that in turn has a negative effect on the lifespan of the power source. This can also negatively affect the lifespan of components within and the device itself. 
     The optimal power transfer happens when coupling between the coils of the target and source is maximized. The coupling also helps to determine the impedance of the charging resonator and determine the impedance of the charging system. If the coils are not optimally aligned, the coupling will be suboptimal and the impedance of the charging coil will also be different from the driving circuit, wasting power. Using similar procedure as previously described, the feedback sensor can match the impedance. This may not increase the power transfer of the inductive charger to the other coil, but it greatly reduces wasted power created by the impedance mismatch. 
     As shown in  FIG. 8 , in one exemplary embodiment, the present invention can be comprised of a microcontroller  841 , a voltage controlled oscillator  843 , a magnitude and/or phase detector  845 , at least one filter  847 , and a coaxial output/directional couplers  849  to an antenna  851 . The present invention can further include a feedback loop for microcontroller control. The filter  847  can be used to avoid interference with the wireless signal. Additionally, the system can further include an attenuator  853 . The present invention operates outside the bandwidth of the operation signal of the device. By operating out of the signal bandwidth, interference is avoided and the resolution can be greatly increased. In some exemplary embodiments, the compared signals do not have follow the exact same path. So in one case the transmitted signal can traverse a first path and the reflected signal can traverse a second path back to the detector. Alternatively, the transmitted and reflected signals can traverse the same path. 
     While particular embodiments and applications have been illustrated and described, it is to be understood that the embodiments are not limited to the precise construction and components disclosed herein and that various modifications, changes and variations may be made in the arrangement, operation and details of the method and apparatus disclosed herein.