Abstract:
A near field communication (NFC) or Radio Frequency Identification (RFID) reader device for contact-less communication includes a transmitter block connected to an antenna via a matching circuitry. An electromagnetic carrier signal and modulated data information are emitted via this main antenna. Any secondary object brought into the vicinity of the main antenna influences the primary resonant circuit resulting in a load change seen by the transmitter. This detuning can cause increased power consumption, RF (Radio Frequency) standard incompliance, and device damage. The present disclosure describes devices and methods on how to detect detuning and how to regulate the transmitter&#39;s output.

Description:
FIELD 
       [0001]    The described embodiments relate generally to devices and methods for NFC (near field communication) or RFID (Radio-frequency identification), and more particularly to devices and methods that provide for NFC or RFID device RF (Radio frequency) detuning detection and driver output power regulation. 
       BACKGROUND 
       [0002]    Wireless communication technologies, such as those used for NFC or ISO 14443 devices, communicate with each other via magnetic field induction in close distance. Each device features an antenna. The primary device (“reader” or “initiator”) generates the magnetic field which can be used to power secondary devices like passive transponders. Modulation schemes applied to the magnetic fields are used for communication purpose between the devices. 
         [0003]    The primary device uses a transmitter to generate the emitted radio frequency (RF) field. A matching circuity is used to transform and adapt the antenna impedance to the emitting device&#39;s transmitter. A low ohmic matching impedance is generally used for increased power transmission. 
         [0004]    One limiting factor of the operating volume size is the emitted RF power of the primary device. Applications like contact-less payment systems require a specific operating distance. As the primary device&#39;s antenna size is often a constraint to the product, high output power transmitters are required. 
         [0005]    The primary and secondary devices form a coupled wireless resonant circuit. If the coupling between the components is increased, the primary resonant circuit will be loaded and detuned. This results in a different load impedance seen by the primary device&#39;s transmitter, possibly causing an increased driver current and increased RF field emission. Regulatory bodies and RF standards limit the maximum allowed emitted RF power. Therefore, incompliance of the application system can occur in case of detuning. Furthermore, increased current consumption can be linked to device damage and reduced user experience in case of battery powered devices. 
         [0006]    Therefore, it is desirable to have devices and methods that can provide for NFC or RFID device RF detuning detection and driver output power regulation. 
       SUMMARY 
       [0007]    This specification discloses devices and methods that can provide for NFC or RFID device RF detuning detection and driver output power regulation. In a first embodiment, a sensor within a transmitter monitors a transmitter (TX) current and/or voltage, so that a detuning of an antenna and matching network can be detected by a change in the TX current and/or voltage. Then, in response to detection of the detuning, the TX current is regulated. This is direct regulation. In a second embodiment, a sensor monitors a voltage or current of an antenna and matching network, so that a detuning of the antenna and matching network can be detected by a change in the voltage or current of the antenna and matching network. Then, in response to detection of the detuning, the TX current is regulated. This is indirect regulation. In a third embodiment, the first and second embodiments can be combined, so that a first sensor within a transmitter monitors a transmitter (TX) current and/or voltage, while a second sensor monitors a voltage or current of an antenna and matching network. Subsequently, a detuning of an antenna and matching network can be detected by a change in the TX current and/or voltage, and/or a change in the voltage or current of the antenna and matching network. Then, in response to detection of the detuning, the TX current is regulated. This is combined regulation. 
         [0008]    RF detuning detection and driver output power regulation is important, because with certain antenna configuration, the maximum allowed driver current can be exceeded when the antenna is detuned with a card. Even though careful antenna design can take care to reduce the maximum current under different detuning scenarios, the maximum allowed driver current can still be exceeded. Therefore, there is need for devices and methods that can provide for NFC or RFID device RF detuning detection and driver output power regulation. 
         [0009]    In one embodiment, a method for detuning detection and transmitter (TX) current regulation is disclosed. The method includes monitoring, by a sensor within a transmitter, a transmitter (TX) current and/or voltage. The method also includes detecting a detuning of an antenna and matching network by a change in the TX current and/or voltage. The method further includes, in response to detection of the detuning, regulating the TX current. In one embodiment, regulation of the TX current is achieved by changing a transmitter supply voltage or a transmitter internal resistance. In one embodiment, changing the transmitter supply voltage or the transmitter internal resistance is controlled using a control unit. In one embodiment, changing the transmitter supply voltage or the transmitter internal resistance is performed by an active attenuator. In one embodiment, the TX current is regulated by using a plurality of gears, wherein each one of the plurality of gears represents a discrete power configuration for the transmitter. In one embodiment, the transmitter is a Near Field Communication (NFC) transmitter or a Radio Frequency Identification (RFID) transmitter. 
         [0010]    In one embodiment, a method for detuning detection and transmitter (TX) current regulation is disclosed. The method includes monitoring a voltage or current of an antenna and matching network. The method also includes detecting a detuning of the antenna and matching network by a change in the voltage or current of the antenna and matching network. The method further includes, in response to detection of the detuning, regulating the TX current. In one embodiment, regulation of the TX current is achieved by changing a transmitter supply voltage or a transmitter internal resistance. In one embodiment, changing the transmitter supply voltage or the transmitter internal resistance is controlled using a control unit. In one embodiment, changing the transmitter supply voltage or the transmitter internal resistance is performed by an active attenuator. In one embodiment, the step of monitoring the voltage or current of the antenna and matching network includes monitoring the voltage or current at one or more nodes of the antenna and matching network. In one embodiment, the TX current is regulated by using a plurality of gears, wherein each one of the plurality of gears represents a discrete power configuration for the transmitter. In one embodiment, the method further includes the steps of: (1) monitoring, by a sensor within a transmitter, a transmitter (TX) current and/or voltage, and (2) detecting a detuning of the antenna and matching network by a change in the TX current and/or voltage and/or a change in the voltage or current of the antenna and matching network. In one embodiment, the transmitter is a Near Field Communication (NFC) transmitter or a Radio Frequency Identification (RFID) transmitter. 
         [0011]    In one embodiment, a device for detuning detection and transmitter (TX) current regulation is disclosed. The device includes an active attenuator configured to generate a transmitter (TX) voltage, an antenna and matching circuit configured to be driven by a TX current corresponding to the TX voltage, a first sensor configured to monitor the TX current and/or voltage, a second sensor configured to monitor a voltage or current of the antenna and matching network, and a control unit. The control unit is configured to detecting a detuning of the antenna and matching network based on a change in the TX current and/or voltage and/or a change in the voltage or current of the antenna and matching network, and, in response to detection of the detuning, regulating the TX current. In one embodiment, the control unit regulates the TX current by changing a TX supply voltage or a TX internal resistance. In one embodiment, the device further includes a pre-driver configured to generate an amplified signal for input to the active attenuator. In one embodiment, the second sensor monitors the voltage or current of the antenna and matching network at one or more nodes of the antenna and matching network. In one embodiment, the TX current is regulated by using a plurality of gears, wherein each one of the plurality of gears represents a discrete power configuration for the transmitter. In one embodiment, the device is a Near Field Communication (NFC) device or a Radio Frequency Identification (RFID) device. 
         [0012]    The above summary is not intended to represent every example embodiment within the scope of the current or future Claim sets. Additional example embodiments are discussed within the Figures and Detailed Description below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The described embodiments and the advantages thereof may best be understood by reference to the following description taken in conjunction with the accompanying drawings. These drawings in no way limit any changes in form and detail that may be made to the described embodiments by one skilled in the art without departing from the spirit and scope of the described embodiments. 
           [0014]      FIG. 1  shows a device (configured for detuning detection and driver output power regulation) that can detect detuning by monitoring for a change in the transmitter (TX) current (i.e., direct regulation), in accordance with some example embodiments. 
           [0015]      FIG. 2  shows a device (configured for detuning detection and driver output power regulation) that can detect detuning by monitoring for a change in the voltage or current of the antenna and matching network (i.e., indirect regulation), in accordance with some example embodiments. 
           [0016]      FIG. 3  shows a device (configured for detuning detection and driver output power regulation) that can detect detuning by utilizing the monitoring techniques of both the  FIG. 1  and  FIG. 2  devices (i.e., combined regulation), in accordance with some example embodiments. 
           [0017]      FIG. 4  shows the architecture of a transmitter (TX) related device that is configured for detuning detection and driver output power regulation, in accordance with some example embodiments. 
           [0018]      FIG. 5  shows details for a  FIG. 4  device, in accordance with some example embodiments. 
           [0019]      FIG. 6  shows how a transmitter (TX) current can be regulated by using a plurality of gears, wherein each one of the plurality of gears represents a discrete power configuration for the transmitter, in accordance with some example embodiments. 
           [0020]      FIG. 7  shows a flow chart of method steps for detuning detection and driver output power regulation, where the detuning is detected by monitoring for a change in the transmitter (TX) current and/or voltage (i.e., direct regulation), in accordance with some example embodiments. 
           [0021]      FIG. 8  shows a flow chart of method steps for detuning detection and driver output power regulation, where the detuning is detected by monitoring for a change in the voltage or current of the antenna and matching network (i.e., indirect regulation), in accordance with some example embodiments. 
           [0022]      FIG. 9  shows a flow chart of method steps for detuning detection and driver output power regulation, where the detuning is detected by combining the detection methods of both  FIG. 7  and  FIG. 8  (i.e., combined regulation), in accordance with some example embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Representative devices and methods according to the present application are described in this section. These examples are being provided solely to add context and aid in the understanding of the described embodiments. It will thus be apparent to one skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the described embodiments. Other embodiments are possible, such that the following examples should not be taken as limiting. 
         [0024]    In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments in accordance with the described embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the described embodiments, it is understood that these examples are not limiting; such that other embodiments may be used, and changes may be made without departing from the spirit and scope of the described embodiments. 
         [0025]      FIG. 1  shows a device  100  configured for detuning detection and driver output power regulation, in accordance with some example embodiments. In particular,  FIG. 1  shows that device  100  can detect detuning by monitoring for a change in the transmitter (TX) current (i.e., direct regulation), in accordance with some example embodiments. 
         [0026]      FIG. 1  shows that an output driver  110  of a transmitter is connected to an antenna by means of a matching network. In  FIG. 1 , the antenna and matching network is labelled as a component  130 , which has a corresponding impedance Z MATCH    135 . Changing the load on the antenna (such as reading a card) can lead to detuning which changes the impedance Z MATCH    135  at the output of the output driver  110 . This leads to a change of the transmitter current I TX1    171  and I TX2    172 . Therefore, detuning of the antenna and matching network  130  can be detected by a change in the transmitter (TX) current (i.e., I TX1    171  and I TX2    172 ). Then, in response to detection of the detuning, the TX current can be regulated. This regulation of the TX current results in a reduced driver current and reduced RF field emission. This allows the transmitter to achieve compliance of the application system in case of detuning, since regulatory bodies and RF standards limit the maximum allowed emitted RF power. Furthermore, the reduced current consumption can minimize device damage and enhance user experience in case of battery powered devices. 
         [0027]      FIG. 1  shows that the output driver  110  of the transmitter includes an active attenuator  120  at the output stage. The active attenuator  120  can be configured to generate a transmitter (TX) voltage. In turn, the antenna and matching circuit  130  can be configured to be driven by a TX current corresponding to the TX voltage. 
         [0028]      FIG. 1  shows that the active attenuator  120  includes a sensor 1 (labelled  140 ), which can be used to monitor the transmitter (TX) current (i.e., I TX1    171  and I TX2    172 ). In one embodiment, only the TX current is monitored, so that detuning of the antenna and matching network is detected by a change in the TX current. It is not shown in  FIG. 1 , but in one embodiment, only the TX voltage is monitored, so that detuning of the antenna and matching network is detected by a change in the TX voltage. This is because detuning of the antenna and matching network can lead to both a change in the TX current and voltage. In one embodiment, both the TX current and voltage are monitored, so that detuning of the antenna and matching network is detected by a change in both the TX current and voltage. This is because detuning of the antenna and matching network can be better detected by monitoring both the change in the TX current and voltage. In one embodiment, the detuning can be detected by monitoring: (1) only the TX current, (2) only the TX voltage, or (3) both the TX current and voltage. The detection method selected can depend on the precision and speed of detection, as well as the ease and cost of detection and implementation. 
         [0029]    In device  100  of  FIG. 1 , the output driver  110  can regulate the TX current (i.e., I TX1 , I TX2 ) by changing a power supply voltage ( 168 ) or internal resistances (i.e., R OUT  1, R OUT  2), depending on the sensed current shift of I TX1  and I TX2 . This change in the power supply voltage ( 168 ) or internal resistances (i.e., R OUT  1, R OUT  2) will in turn cause the output voltages (i.e., V TX1 , V TX2 ) to be changed. In  FIG. 1 , internal resistances are shown as R OUT  1 ( 191 ), R OUT  2 ( 192 ), which are included in the active attenuator  120 . In one embodiment, the internal resistances can be any transmitter internal resistance, which can be used to regulate the TX current. In one embodiment, the power supply voltage can be any transmitter supply voltage, which can be used to regulate the TX current. In  FIG. 1 , output voltages (i.e., V TX1 , V TX2 ) are not shown. In one embodiment, the output voltages (i.e., V TX1 , V TX2 ) can be the voltages provided at nodes TX 1  ( 181 ) and TX 2  ( 182 ). 
         [0030]      FIG. 1  shows that the output driver  110  of the transmitter includes a control unit  160  configured to detecting a detuning of the antenna and matching network based on a change in the TX current and, in response to detection of the detuning, regulating the TX current. In  FIG. 1 , sensor  1  ( 140 ) provides a signal  1  ( 145 ) to control unit  160 . Sensor  1  ( 140 ) is monitoring the TX current (i.e., I TX1    171 , I TX2    172 ), so that signal  1  ( 145 ) can be used by the control unit  160  to detect a change in the TX current. Then, after a detuning of the antenna and matching network has been detected, the control unit  160  can in turn send a control signal  165  to the active attenuator  120  to regulate the TX current by changing the internal resistances (i.e., R OUT  1, R OUT    2 ). In one embodiment, the control unit  160  can regulate the TX current by changing the power supply voltage ( 168 ). In one embodiment, the control unit can regulate the TX current by changing: (1) only a transmitter supply voltage, (2) only a transmitter internal resistance, or (3) both the transmitter supply voltage and the transmitter internal resistance. The changing method selected can depend on the precision and speed of change, as well as the ease of change and the manner of implementation. In one embodiment, the control unit  160  can be partially or completely outside of the output driver  110 . 
         [0031]      FIG. 2  shows a device  200  configured for detuning detection and driver output power regulation, in accordance with some example embodiments. In particular,  FIG. 2  shows that device  200  can detect detuning by monitoring for a change in the voltage or current of the antenna and matching network (i.e., indirect regulation), in accordance with some example embodiments. 
         [0032]      FIG. 2  shows that an output driver  210  of a transmitter is connected to an antenna by means of a matching network. In  FIG. 2 , the antenna and matching network is labelled as a component  230 , which has a corresponding impedance Z MATCH    235 . Changing the load on the antenna (such as reading a card) can lead to detuning which changes the impedance Z MATCH    235  at the output of the output driver  210 . This leads to a change of the transmitter current I TX1    271  and I TX2    272 , which in turn causes a change in the voltage or current of the antenna and matching network  230 . In other words, the detuning effect increases or decreases the voltage/current at one or more nodes of the antenna and matching network  230 , which is correlated to the variation of the TX current (i.e., I TX1    271 , I TX2    272 ). Therefore, detuning of the antenna and matching network  230  can be detected by a change in the voltage or current of the antenna and matching network  230 . Then, in response to detection of the detuning, the TX current can be regulated. This regulation of the TX current results in a reduced driver current and reduced RF field emission, with the benefits of: (1) compliance to regulatory bodies and RF standards in the case of detuning, (2) minimizing device damage, and (3) enhanced user experience in case of battery powered devices. 
         [0033]      FIG. 2  shows that the output driver  210  of the transmitter includes an active attenuator  220  at the output stage. Similar to device  100  of  FIG. 1 , the active attenuator  220  can be configured to generate a transmitter (TX) voltage. In turn, the antenna and matching circuit  230  can be configured to be driven by a TX current corresponding to the TX voltage. 
         [0034]      FIG. 2  shows that the active attenuator  220  includes a sensor 2 (labelled  250 ), which can be used to monitor a voltage or current of the antenna and matching network  230 . In one embodiment, only a voltage of the antenna and matching network is monitored, so that detuning of the antenna and matching network is detected by a change in the voltage of the antenna and matching network. In one embodiment, only a current of the antenna and matching network is monitored, so that detuning of the antenna and matching network is detected by a change in the current of the antenna and matching network. In one embodiment, both the voltage and current of the antenna and matching network are monitored, so that detuning of the antenna and matching network is detected by a change in both the voltage and current of the antenna and matching network. This is because detuning of the antenna and matching network can be better detected by monitoring both the change in the voltage and current of the antenna and matching network. In one embodiment, the detuning can be detected by monitoring: (1) only the voltage, (2) only the current, or (3) both the voltage and current of the antenna and matching network. The detection method selected can depend on the precision and speed of detection, as well as the ease and cost of detection and implementation. In one embodiment, sensor 2 (labelled  250 ) monitors the voltage or current of the antenna and matching network at one node of the antenna and matching network. In one embodiment, sensor 2 (labelled  250 ) monitors the voltage or current of the antenna and matching network at one or more nodes of the antenna and matching network. 
         [0035]    In device  200  of  FIG. 2 , the output driver  210  can regulate the TX current (i.e., I TX1 , I TX2 ) by a power supply voltage ( 268 ) or internal resistances (i.e., R OUT  1, R OUT  2), depending on the sensed voltage or current variation of the antenna and matching network  230 . In  FIG. 2 , internal resistances are shown as R OUT  1 ( 291 ), R OUT  2 ( 292 ), which are included in the active attenuator  220 . In one embodiment, the internal resistances can be any transmitter internal resistance, which can be used to regulate the TX current. In one embodiment, the power supply voltage can be any transmitter supply voltage, which can be used to regulate the TX current. In  FIG. 2 , output voltages (i.e., V TX1 , V TX2 ) are not shown. In one embodiment, the output voltages (i.e., V TX1 , V TX2 ) can be the voltages provided at nodes TX 1  ( 281 ) and TX 2  ( 282 ). 
         [0036]      FIG. 2  shows that the output driver  210  of the transmitter includes a control unit  260  configured to detecting a detuning of the antenna and matching network based on a change in the voltage or current of the antenna and matching network, and, in response to detection of the detuning, regulating the TX current. In  FIG. 2 , sensor 2 ( 250 ) provides a signal 2 ( 255 ) to control unit  260 . Sensor 2 ( 250 ) is monitoring the voltage or current of the antenna and matching network  230 , so that signal 2 ( 255 ) can be used by the control unit  260  to detect a change in the voltage or current of the antenna and matching network  230 . Then, after a detuning of the antenna and matching network has been detected, the control unit  260  can in turn send a control signal  265  to the active attenuator  220  to regulate the TX current by changing the internal resistances (i.e., R OUT  1, R OUT  2). In one embodiment, the control unit  260  can regulate the TX current by changing the power supply voltage ( 268 ). In one embodiment, the control unit can regulate the TX current by changing: (1) only a transmitter supply voltage, (2) only a transmitter internal resistance, or (3) both the transmitter supply voltage and the transmitter internal resistance. The changing method selected can depend on the precision and speed of change, as well as the ease of change and the manner of implementation. In one embodiment, the control unit  260  can be partially or completely outside of the output driver  210 . 
         [0037]      FIG. 3  shows a device  300  configured for detuning detection and driver output power regulation, in accordance with some example embodiments. In particular,  FIG. 3  shows that device  300  can detect detuning by utilizing the monitoring techniques of both the  FIG. 1  and  FIG. 2  devices (i.e., combined regulation), in accordance with some example embodiments. In other words,  FIG. 3  utilizes both “direct regulation” and “indirect regulation” (i.e., “combined regulations”). In summary, device  300  of  FIG. 3  can detect detuning by monitoring for a change in the transmitter (TX) current and/or voltage (i.e., direct regulation), and/or a change in the voltage or current of the antenna and matching network (i.e., indirect regulation). 
         [0038]      FIG. 3  shows that an output driver  310  of a transmitter is connected to an antenna and matching network  330 , which has a corresponding impedance Z MATCH    335 . Changing the load on the antenna (such as reading a card) can lead to detuning which changes the impedance Z MATCH    335  at the output of the output driver  310 . This leads to a change of the transmitter current I TX1    371  and I TX2    372 , which in turn causes a change in the voltage or current of the antenna and matching network. Therefore, detuning of the antenna and matching network  330  can be detected by a change in the TX current and/or voltage, and/or a change in the voltage or current of the antenna and matching network  330 . Then, in response to detection of the detuning, the TX current can be regulated. This regulation of the TX current results in a reduced driver current and reduced RF field emission, with the same benefits as described for device  100  of  FIG. 1  and device  200  of  FIG. 2 . 
         [0039]      FIG. 3  shows that the output driver  310  of the transmitter includes an active attenuator  320  at the output stage. Similar to device  100  of  FIG. 1  and device  200  of  FIG. 2 , the active attenuator  320  can be configured to generate a transmitter (TX) voltage. In turn, the antenna and matching circuit  330  can be configured to be driven by a TX current corresponding to the TX voltage. 
         [0040]      FIG. 3  shows that the active attenuator  320  includes two sensors: a sensor 1 (labelled  340 ) and a sensor 2 (labelled  350 ). Sensor 1 ( 340 ) can be used to monitor the transmitter (TX) current (i.e., I TX1    371  and I TX2    372 ) and/or voltage. Sensor 2 ( 350 ) can be used to monitor a voltage or current of the antenna and matching network  330 . In one embodiment, only sensor 1 ( 340 ) is used, so that detuning of the antenna and matching network is detected by a change in a change in the TX current and/or voltage. In one embodiment, only sensor 2 ( 350 ) is used, so that detuning of the antenna and matching network is detected by a change in the voltage or current of the antenna and matching network  330 . In one embodiment, both sensor 1 ( 340 ) and sensor 2 ( 350 ) are used, so that detuning of the antenna and matching network is detected by a change in the TX current and/or voltage, and/or by a change in the voltage or current of the antenna and matching network  330 . This is because detuning of the antenna and matching network can be better detected by using both sensors to monitor the changes in current and voltage. In one embodiment, the detuning can be detected by using: (1) only sensor 1, (2) only sensor 2, or (3) both sensor 1 and sensor 2. The detection method selected can depend on the precision and speed of detection, as well as the ease and cost of detection and implementation. 
         [0041]    In device  300  of  FIG. 3 , the output driver  310  can regulate the TX current (i.e., I TX1 , I TX2 ) by changing a power supply voltage ( 368 ) or internal resistances (i.e., R OUT  1, R OUT  2), depending on the sensed current shift of I TX1  and I TX2  (internal variation), and/or on the voltage and current variation in the antenna and matching network  330 . In  FIG. 3 , internal resistances are shown as R OUT  1 ( 391 ), R OUT  2 ( 392 ), which are included in the active attenuator  320 . In one embodiment, the internal resistances can be any transmitter internal resistance, which can be used to regulate the TX current. In one embodiment, the power supply voltage can be any transmitter supply voltage, which can be used to regulate the TX current. In  FIG. 3 , output voltages (i.e., V TX1 , V TX2 ) are not shown. In one embodiment, the output voltages (i.e., V TX1 , V TX2 ) can be the voltages provided at nodes TX 1  ( 381 ) and TX 2  ( 382 ). 
         [0042]      FIG. 3  shows that the output driver  310  of the transmitter includes a control unit  360  configured to detecting a detuning of the antenna and matching network based on a change in the TX current and/or voltage and/or a change in the voltage or current of the antenna and matching network, and, in response to detection of the detuning, regulating the TX current. In  FIG. 3 , sensor 1 ( 340 ) provides a signal 1 ( 345 ) to control unit  360 , while sensor 2 ( 350 ) provides a signal 2 ( 355 ) to control unit  360 . Then, after a detuning of the antenna and matching network has been detected, the control unit  360  can in turn send a control signal  365  to the active attenuator  320  to regulate the TX current by changing the internal resistances (i.e., R OUT  1, R OUT  2). In one embodiment, the control unit  360  can regulate the TX current by changing the power supply voltage ( 368 ). In one embodiment, the control unit can regulate the TX current by changing: (1) only a transmitter supply voltage, (2) only a transmitter internal resistance, or (3) both the transmitter supply voltage and the transmitter internal resistance. The changing method selected can depend on the precision and speed of change, as well as the ease of change and the manner of implementation. In one embodiment, the control unit  360  can be partially or completely outside of the output driver  310 . 
         [0043]      FIG. 4  shows the architecture of a transmitter (TX) related device  400  that is configured for detuning detection and driver output power regulation, in accordance with some example embodiments. In particular,  FIG. 4  shows that device  400  includes an output driver  410 , a pre-driver  420 , a clock control  450 , a module  460  (amplitude regulation and modulation), and an antenna and matching network  430 . In one embodiment, the pre-driver  420  provides for amplification, while the output driver  410  provides for attenuation. 
         [0044]      FIG. 4  shows that the output driver  410  includes a sensor  1  (labelled  440 ), which can be used to monitor the transmitter (TX) current (i.e., I TX1  and I TX2 ) and/or voltage. In one embodiment, only the TX current and/or voltage is monitored, so that detuning of the antenna and matching network is detected by a change in the TX current and/or voltage. It is not shown in  FIG. 1 , but in one embodiment, the output driver  410  also includes a sensor 2, which can be used to monitor a voltage or current of the antenna and matching network  430 .  FIG. 4  also shows nodes TX 1  ( 481 ) and TX 2  ( 482 ), which are associated with the transmitter (TX) currents I TX1  and I TX2 , respectively. 
         [0045]    Module  460  provides for amplitude regulation and modulation. Amplitude regulation controls output power and modulation index. In one embodiment, module  460  provides power supply voltage ( 462 ) to the output driver  410  and Vcontrol ( 464 ) to the pre-driver  420 . In one embodiment, there are different voltages for power supply voltage ( 462 ) for different modes, such as reader mode and card mode. In one embodiment, the clock control  450  provides clock control to the pre-driver  420 . In one embodiment, a part of or all of the control unit (e.g.,  160 ,  260 ,  360 ) can be included in module  460 . In one embodiment, a part of or all of the module  460  can be included in the control unit (e.g.,  160 ,  260 ,  360 ). 
         [0046]      FIG. 5  shows details for device  400  of  FIG. 4 , in accordance with some example embodiments. In particular,  FIG. 5  shows details for the output driver  410 , the pre-driver  420 , and the module  460  (amplitude regulation and modulation). In particular, output driver  410  is an active attenuator that is providing active attenuation. The output driver  410  is not an amplifier. This is because TX 1  level≦TVDD≦Input level, where TVDD is the power supply voltage. The input signal is greater than TVDD, while TVDD is greater than or equal to the TX 1  level, which is the output level. Therefore, the output driver  410  actively attenuates the input signal from the pre-driver  420 , while the input signal is amplified (boosted) in the pre-driver  420 . In particular, the maximum output voltage level of the output driver  410  is regulated by changing the supply voltage or the output resistance. In one embodiment, attenuation is obtained by reducing the TVDD (which is the power supply voltage) or by changing the number of NMOS (Rout), where NMOS is an n-channel MOSFET (metal-oxide-semiconductor field-effect transistor). In  FIG. 5 , the high-side transistor of the output driver is M 2 , which is NMOS. In one embodiment, M 1  and M 2  can provide the internal resistances (i.e., R OUT  1, R OUT  2) needed for regulating the TX current. In this regard, in one embodiment, M 1  and M 2  can be an array of transistors that can be turned on or off to produce the required resistance. 
         [0047]      FIG. 6  shows how a transmitter (TX) current can be regulated by using a plurality of gears, wherein each one of the plurality of gears represents a discrete power configuration for the transmitter, in accordance with some example embodiments. In particular,  FIG. 6  shows that the TX current can be regulated by using N gears, where each gear represents a discrete power configuration for the transmitter. In  FIG. 6 , it is shown that there can be Gear 1 ( 610 ), Gear 2 ( 620 ), Gear 3 ( 630 ), . . . , Gear N ( 640 ). It is also shown that it is possible to shift up and down between these various gears, and, in one embodiment, the process can start with Gear 1. 
         [0048]    An algorithm can be applied to operate a device configured for detuning detection and driver output power regulation, such as one of the devices shown in  FIGS. 1-5 . In one embodiment, the algorithm can be applied as follows: While the transmitter is generating an RF field, a device configured for detuning detection and driver output power regulation can sense the transmitter (TX) current and/or voltage value periodically. Or, in one embodiment, a device configured for detuning detection and driver output power regulation can sense the transmitter (TX) current and/or voltage value and/or the voltage or current value of the antenna and matching network periodically. If the sensed value exceeds the predefined upper threshold, the TX block configuration shall be updated such that the emitted RF power is reduced (i.e., “Shift down” as shown in  FIG. 6 ). Similarly, if the value is below a lower threshold, the emitted RF power shall be increased again (i.e., “Shift up” as shown in  FIG. 6 ). 
         [0049]    To avoid too low (and too high) field emission during the regulation, a discretization of the TX power range in several TX configurations can improve the efficiency and performance of the applied algorithm. Several TX power levels are defined to adapt the device and the communication for varying load conditions. Each relates to a specific register configuration (“gear”). The regulation is based on reading the sensed value and comparing to normalized threshold settings. The gear is then updated accordingly. 
         [0050]    In one embodiment, a gear represents the TX configuration in reader mode. Gear 1 reflects the “high power” configuration, so any higher numbered gear will have reduced TX power. The system can be in Gear 1 to N. In one embodiment, the system initially starts in Gear 1. In one embodiment, while in any gear:
       (1) Read out sensed value and predict transmitter (TX) current.   (2) If TX current&gt;TX current(max_threshold), then shift down (if possible).   (3) If TX current&lt;TX current(min_threshold), then shift up (if possible).       
 
         [0054]      FIG. 7  shows a flow chart of method steps for detuning detection and driver output power regulation, where the detuning is detected by monitoring for a change in the transmitter (TX) current and/or voltage (i.e., direct regulation), in accordance with some example embodiments. As shown in  FIG. 7 , the method  700  begins at step  710 , where the method monitors, by a sensor within a transmitter, a transmitter (TX) current and/or voltage. Then, the method proceeds to step  720 . In step  720 , the method detects a detuning of an antenna and matching network by a change in the TX current and/or voltage. Next, at step  730 , the method, in response to detection of the detuning, regulates the TX current. 
         [0055]      FIG. 8  shows a flow chart of method steps for detuning detection and driver output power regulation, where the detuning is detected by monitoring for a change in the voltage or current of the antenna and matching network transmitter (TX) current (i.e., indirect regulation), in accordance with some example embodiments. As shown in  FIG. 8 , the method  800  begins at step  810 , where the method monitors a voltage or current of an antenna and matching network. Then, the method proceeds to step  820 . In step  820 , the method detects a detuning of the antenna and matching network by a change in the voltage or current of the antenna and matching network. Next, at step  830 , the method, in response to detection of the detuning, regulates the TX current. 
         [0056]      FIG. 9  shows a flow chart of method steps for detuning detection and driver output power regulation, where the detuning is detected by combining the detection methods of both  FIG. 7  and  FIG. 8  (i.e., combined regulation), in accordance with some example embodiments. As shown in  FIG. 9 , the method  900  begins at step  910 , where the method monitors a voltage or current of an antenna and matching network. Then, the method proceeds to step  920 . In step  920 , the method monitors, by a sensor within a transmitter, a transmitter (TX) current and/or voltage. Next, at step  930 , the method detects a detuning of the antenna and matching network by a change in the TX current and/or voltage and/or a change in the voltage or current of the antenna and matching network. Then, at step  940 , the method, in response to detection of the detuning, regulates the TX current. 
         [0057]    In this specification, example embodiments have been presented in terms of a selected set of details. However, a person of ordinary skill in the art would understand that many other example embodiments may be practiced which include a different selected set of these details. It is intended that the following claims cover all possible example embodiments. 
         [0058]    The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. 
         [0059]    The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.