Systems and methods for multi-mode inductively couples communication

A method for inductively coupled communication is described. The method includes determining an operational mode for inductively coupled communication. The method also includes performing the operational mode by combining a transmit power amplifier (PA) output replica and a PA output copy at a signal combining block of a receiver. The PA output replica reflects effects of channel properties. The PA output copy is unaffected by the channel properties.

TECHNICAL FIELD

The described technology generally relates to an apparatus and method of wireless communication. More particularly, the technology relates to multiple operational modes in near-field communication (NFC).

BACKGROUND

The wireless communication environment in a home or an office generally includes a number of independently developed radio access technologies and standards. These technologies were initially designed for target applications and they perform relatively well for these applications. In a typical home or office environment, an access to content (e.g., web, video, etc.) is provided to a broadband modem through the home-owner's IP backhaul connection. For instance, mobile services are provided through the cellular network, through either a macro cell or a femto cell located within the home or office. Wireless local area network (WLAN) access points (APs) provide data connectivity between computers, cell phones, laptops, printers, and other wireless stations using 802.11-based Wi-Fi technology.

Another communication medium currently being implemented in electronic equipment is near-field communication (NFC). NFC is an inductively coupled communication technology. The use of NFC interfaces in electronic equipment provides portable devices with functions similar to those of non-contact integrated circuit cards (e.g., radio frequency identification (RFID) cards). In addition, electronic equipment provided with NFC interfaces is typically capable of operating as radio frequency (RF) readers and/or writers to communicate with other NFC devices.

A wireless communication device may communicate with a remote device using NFC technology. Benefits may be realized by using a single transmitter and receiver to perform multiple operational modes in NFC.

SUMMARY

A method for inductively coupled communication is described. The method includes determining an operational mode for inductively coupled communication. The method also includes performing the operational mode by combining a transmit power amplifier (PA) output replica and a PA output copy at a signal combining block of a receiver. The PA output replica reflects effects of channel properties. The PA output copy is unaffected by the channel properties.

The channel properties may include loading conditions in relation to at least one of an antenna, matching network, coupling to a remote device, or load modulation.

In an implementation, the signal combining block may perform time domain summing of the PA output replica and the PA output copy. The PA output copy may be subtracted from the PA output replica. In another implementation, the signal combining block may perform frequency translation.

Phase, frequency and amplitude alignments of the PA output replica and the PA output copy may be variable with respect to each other, and with respect to incoming received signals. The poly-phase, multi-tone and amplitude variable aspects of the PA output replica and the PA output copy may be implemented in analog, digital or a combination of both analog and digital portions of a near-field communication (NFC) block.

The operational mode may be a reader mode with target load modulation. Performing the operational mode may include transmitting an outgoing carrier. An incoming load modulation of the outgoing carrier may be sensed by providing the PA output replica to the signal combining block. The outgoing carrier may be stripped at the signal combining block with the PA output copy to isolate an incoming load modulation signal and carrier residue.

The operational mode may be a target mode. A low level outgoing carrier may be transmitted to maintain a controlled output impedance connection at a matching network and antenna. An incoming modulation of an incoming carrier may be sensed by providing the PA output replica to the signal combining block. The outgoing carrier and incoming carrier may be stripped at the signal combining block with the PA output copy with a weighted output level to isolate an incoming modulation signal.

The method may also include performing a phase lock on an incoming carrier based on a summing error generated by summing the PA output replica and the PA output copy at the signal combining block.

The operational mode may be a target mode with active load modulation (ALM). An outgoing ALM sub-carrier may be transmitted. The outgoing ALM sub-carrier and incoming modulation of an incoming carrier may be sensed by providing the PA output replica to the signal combining block. The outgoing ALM sub-carrier and the incoming carrier may be stripped at the signal combining block with the PA output copy to isolate an incoming modulation signal on the incoming carrier.

The operational mode may be a radio frequency (RF) polling mode. An outgoing polling signal may be transmitted. The outgoing polling signal and channel effects may be sensed by providing the PA output replica to the signal combining block. Signal levels for the channel effects may be determined by subtracting the PA output copy from the PA output replica at the signal combining block. The presence of a coupled object may be determined based on a change in the signal levels.

The operational mode may be an RF polling mode. The signal combining block may include a receiver analog-to-digital converter (ADC). An outgoing polling signal may be transmitted. The outgoing polling signal and channel effects may be sensed by providing the PA output replica to an input of the receiver ADC. Signal levels for the channel effects may be determined by providing the PA output copy at higher order frequencies to a clock of the receiver ADC. The presence of a coupled object may be determined based on a change in the signal levels.

The operational mode is an RF polling mode. The signal combining block may include a receiver ADC. An outgoing polling signal may be transmitted. The outgoing polling signal and channel effects may be sensed by providing the PA output replica to an input of the receiver ADC. Signal levels for the channel effects may be determined by providing the PA output copy that is at or near frequencies of the transmitted polling signal to a clock of the receiver ADC. The presence of a coupled object may be determined based on a change in resulting directly down-converted signal levels.

A wireless communication device for inductively coupled communication is also described. The wireless communication device includes a processor, a memory in communication with the processor, and instructions stored in the memory. The instructions are executable by the processor to determine an operational mode for inductively coupled communication. The instructions are also executable to perform the operational mode by combining a transmit PA output replica and a PA output copy at a signal combining block of a receiver. The PA output replica reflects effects of channel properties. The PA output copy is unaffected by the channel properties.

An apparatus for inductively coupled communication is also described. The apparatus includes means for determining an operational mode for inductively coupled communication. The apparatus also includes means for performing the operational mode by combining a transmit PA output replica and a PA output copy at a signal combining block of a receiver. The PA output replica reflects effects of channel properties. The PA output copy is unaffected by the channel properties.

A computer-program product for inductively coupled communication is also described. The computer-program product includes a non-transitory computer-readable medium having instructions thereon. The instructions include code for causing a wireless communication device to determine an operational mode for inductively coupled communication. The instructions also include code for causing the wireless communication device to perform the operational mode by combining a transmit PA output replica and a PA output copy at a signal combining block of a receiver. The PA output replica reflects effects of channel properties. The PA output copy is unaffected by the channel properties.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary implementations of the disclosure and is not intended to represent the only implementations in which the disclosure may be practiced. The term “exemplary” used throughout this description means “serving as an example, instance, or illustration,” and should not necessarily be construed as preferred or advantageous over other exemplary implementations. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary implementations of the disclosure. In some instances, some devices are shown in block diagram form.

Various configurations are now described with reference to the Figures, where like reference numbers may indicate functionally similar elements. The systems and methods as generally described and illustrated in the Figures herein could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of several configurations, as represented in the Figures, is not intended to limit scope, as claimed, but is merely representative of the systems and methods.

FIG. 1is a block diagram illustrating one configuration of a wireless communication system100for performing inductively coupled communication. The wireless communication system100may include a wireless communication device102that is in communication with a remote device104. In one configuration, the wireless communication device102and the remote device104may communicate using inductively coupled communication.

The wireless communication device102may also be referred to as an electronic communication device, mobile device, mobile station, subscriber station, client, client station, user equipment (UE), remote station, access terminal, mobile terminal, terminal, user terminal, subscriber unit, etc. Examples of wireless communication devices include laptop or desktop computers, cellular phones, smart phones, wireless modems, e-readers, tablet devices, gaming systems, etc. Some of these devices may operate in accordance with one or more industry standards.

In an implementation of inductively coupled communication, the wireless communication device102and the remote device104may use near-field communication (NFC). In the context of near-field communications, there are two devices communicating: a reader and a target. The wireless communication device102may operate as a reader NFC device or as a target NFC device depending on an operational mode124. A reader NFC device may also be referred to as a poller, polling device, or initiator. A target NFC device may also be referred to as a listener, listening device, or tag. When operating as a reader, the antenna114of the wireless communication device102may produce a radiated field (also referred to as a magnetic field or an electromagnetic field). This radiated field may be received by the antenna of a remote device104that is operating as a target NFC device.

The wireless communication device102and the remote device104may use one or more NFC signaling technologies to communicate with each other. The NFC signaling technologies may include NFC type-A, NFC type-B and NFC type-F. The NFC signaling technologies differ in the modulation schemes employed.

NFC has four different tag types, which support a subset of the NFC signaling technologies. Type 1 tags (T1T) use NFC type-A communication without data collision protection. Type 2 tags (T2T) use NFC type-B communication with anti-collision. Type 3 tags (T3T) use NFC type-F with anti-collision. Type 4 tags (T4T) can use either NFC type-A (T4AT) or NFC type-B (T4BT) with anti-collision.

In a configuration, the wireless communication device102and the remote device104may be operable to communicate using NFC through various interfaces, such as a frame RF interface, ISO-data exchange protocol (DEP) RF interface and NFC-DEP RF interface. In another configuration, the wireless communication device102and the remote device104may establish an NFC-DEP RF protocol-based communication link with link layer connections defined through a logical link control protocol (LLCP). In still another configuration, the wireless communication device102and the remote device104may be operable to be connected to an access network and/or core network (e.g., a CDMA network, a GPRS network, a UMTS network, and other types of wireline and wireless communication networks).

In another operational mode124, the wireless communication device102may poll for nearby NFC devices. The remote device104may begin to listen when it comes within a few centimeters of the wireless communication device102. The wireless communication device102will then communicate with the remote device104to determine which signaling technologies can be used. For example, when the wireless communication device102is acting as a reader, the remote device104may enter the radiated field of the wireless communication device102.

When in reader mode, the wireless communication device102may generate an RF field to communicate with the remote device104. The wireless communication device102may modulate the RF field to send a signal (e.g., data) to the remote device104. Once the remote device104receives that signal, the wireless communication device102may transmit a continuous wave to maintain the RF field. The continuous wave may have a carrier frequency. In the case of NFC, the carrier frequency may be 13.56 megahertz (MHz). The remote device104may receive the RF field. The remote device104may respond by performing modulation on top of the continuous wave. The wireless communication device102may receive the modulated signal and try to decode it.

NFC hardware system architectures may perform one or more of the operational modes124. These operational modes124are discrete functional activities. For example, NFC systems may perform activities related to a reader/writer (e.g., reader) and card emulation (e.g., target), as described above.

In an approach, these operational modes124lead to an architecture with discrete blocks, the blocks including circuits to perform the different operational modes124. For example, one block may be dedicated to RF polling operations (e.g., sniffing or target detection). Another block may be dedicated to reader transmit and receive operations. And another block may be dedicated to target transmit (of either passive or active load modulation) and target receive operations.

Each of the discrete blocks may include one or more pins for integration into an NFC chip. However, the allocation of specific blocks and package pins to deal with specific tasks can be expensive, inefficient and time consuming to implement and integrate.

The systems and methods herein describe the use of an NFC transmit power amplifier (PA) output replica120and a PA output copy122in combination with a receiver signal combining block116to perform multiple operational modes124. This may allow for multiple NFC functional activities (i.e., operational modes124) to be undertaken by the same NFC block106instead of implementing dedicated designs for each operational mode124.

The wireless communication device102may include an NFC block106that performs NFC operations. For example, the NFC block106may establish a communication channel126between the wireless communication device102and a remote device104using NFC protocols. The NFC block106may also be referred to as an NFC controller (NFCC), an NFC chip or a module on a system-on-chip (SoC). The NFC block106may include a transmitter108and a receiver118.

The PA output replica120reflects the external output voltage and currents of the PA110, and can therefore replicate the effects of channel properties. These channel properties may include loading conditions in relation to at least one of the antenna114, matching network112, coupling to a remote device104or any load modulation conditions.

In an implementation, the NFC block106may (optionally) include a PA output replica generator125that generates the PA output replica120. The PA output replica generator125may be coupled between the PA110and the matching network112(as shown) or may be integrated within the PA110. In an approach, the PA output replica generator125may be a circuit-level current/voltage mirror circuit that faithfully replicates a ratio of the PA output stage currents and voltages. In another approach, the PA output replica generator125may be current and voltage sensing transformers. In another approach, the PA output replica generator125may be a tap from an electromagnetic interference (EMI) filter (e.g., ISM filter). In yet another approach, the PA output replica generator125may be a coupler that measures reflected power waves and incident power waves instead of voltages and currents. The generation of the PA output replica120is described in more detail in connection withFIG. 3.

The PA output copy122may be a scaled transmit signal copy. The PA output copy122is unaffected by the channel properties such as the effects of loading conditions due to the antenna114, matching network112, coupling to a remote device104and load modulation conditions.

It should be noted that the same source signal may be used to generate the PA output replica120and the PA output copy122. However, the NFC block106may independently change the phase and amplitude of the PA output copy122with respect to the PA output replica120. Thus, in one example, a separate digital-to-analog converter (DAC) may generate and scale the PA output copy122.

In an implementation, the signal combining block116may include a summer that performs receiver block summing (also referred to as receiver summing). In this implementation, the signal combining block116may perform time domain summing of the PA output replica120and the PA output copy122. The PA output copy122may be subtracted from the PA output replica120to leave only the incoming signal (e.g., modulated signal) and carrier residue. This implementation may be configured for cancellation and carrier correlation.

In another implementation, the signal combining block116may include a mixer. In this implementation, the mixer may perform frequency translation using the PA output replica120and the PA output copy122. For example, the PA output replica120may be multiplied by the negative of PA output copy122. The remaining signal may be at the carrier frequency. This remaining signal may be mixed down in the receiver118using the PA output copy122again to get the signal down to DC. The receiver118may then reject the DC to leave only the incoming signal (e.g., modulated signal) and carrier residue.

In yet another implementation, the signal combining block116may include an analog-to-digital converter (ADC)129of the receiver118. In this implementation, the PA output replica120may be provided to an input of the receiver ADC129. The PA output copy122may be provided to the clock of the receiver ADC129. The resulting output of the ADC129may be used for RF polling, as described below.

It should be noted that while the signal combining block116is shown outside the receiver118inFIG. 1, the signal combining block116may also be included within the receiver118. Furthermore, down-conversion (either direct or intermediate frequency (IF)) and digitization may be done in the receiver118.

The PA output replica120may be coupled to the external matching network112and the antenna114. The PA output replica120may also be coupled to the signal combining block116. The PA output copy122may be coupled to the signal combining block116. The PA output replica120and PA output copy122may be internally routed to the receiver path, eliminating the need for external receiver package pins and associated external components.

The NFC block106may perform multiple operational modes124using the PA output replica120, the PA output copy122and the signal combining block116. One operational mode124may include a reader mode in which the wireless communication device102operates as reader. Another operational mode124may include a target mode in which the wireless communication device102operates as a target. Yet another operational mode124may include an RF polling mode in which the wireless communication device102may poll for nearby NFC devices.

In one case, the operational mode124of the wireless communication device102may be reader mode with target passive load modulation. In this operational mode124, the wireless communication device102is acting as a reader and the remote device104is the target. The wireless communication device102may send an outgoing carrier to the remote device104. For instance, the PA110of the transmitter108may send the carrier to the matching network112and antenna114for transmission to the remote device104.

The remote device104may receive the outgoing carrier and respond by performing passive load modulation on the carrier. The PA output replica120, which includes the incoming load modulation of the outgoing carrier, may be fed to the signal combining block116. In this way, the wireless communication device102may sense incoming load modulation of the outgoing carrier when in reader mode with target passive load modulation.

The PA output copy122may be fed to the signal combining block116to strip the outgoing carrier to leave just the incoming load modulation signal and carrier residue. As used herein, the term “strip” or “stripping” refers to cancellation of a signal. Therefore, in this case, the signal combining block116may perform cancellation of the outgoing carrier. This may be accomplished by subtracting the PA output copy122from the PA output replica120. The resulting load modulation signal may be further processed by the receiver118.

In another case, the operational mode124of the wireless communication device102may be reader mode with incoming target active load modulation (ALM). In this operational mode124, the wireless communication device102is acting as a reader and the remote device104is the target.

To compensate for the deficiencies of passive load modulation, a target device may use active load modulation (ALM). With ALM, alternate circuit approaches are based on synchronizing the target device to the signal from the reader device. The target device may regenerate the signal received from the reader device. The target device may then retransmit a phase-synchronized modulated signal to the reader device. With ALM, the resulting level of the modulation received at the reader device can be higher than the modulation level produced by a traditional passive (e.g., resistive) load modulation.

When operating in reader mode with incoming target ALM, the wireless communication device102may send an outgoing carrier to the remote device104as described above. The remote device104may then perform ALM on the carrier.

The PA output replica120may be fed to the signal combining block116for sensing the incoming active load modulation of the outgoing carrier. The PA output copy122is fed to the signal combining block116to strip the outgoing carrier to leave just the incoming active load modulation signal and carrier residue. The resulting modulation signal may be further processed by the receiver118.

In another case, the operational mode124of the wireless communication device102may be target mode. In this operational mode124, the wireless communication device102is acting as the target and the remote device104is the reader. The wireless communication device102may then receive a modulated signal from the remote device104.

A very low level or no carrier level may be transmitted by the PA110to the external outputs connecting the NFC block106to the matching network112. For example, in an implementation where the NFC block106is connected to the matching network112using one or more package pins, the PA110may transmit a low level or no carrier level across the pins to the matching network112. This maintains a controlled output impedance connection to the matching network112and antenna114. Leaving this circuit disconnected and at a higher impedance may lead to an un-damped response and high induced voltage levels at the package pins of the NFC chip, possibly damaging the circuits. Therefore, transmitting a low level (or no level) carrier may maintain a controlled output impedance and prevent this damage condition.

The PA output replica120may be fed to the signal combining block116for sensing the modulation of an incoming carrier from an external reader (e.g., remote device104). In an implementation, the PA output copy122with weighted output level may be fed to the signal combining block116that aligns with the incoming carrier (from the external reader) to leave just the incoming modulation signal and carrier residue. The resulting modulation signal may be further processed by the receiver118.

The transmitter108may optionally include an output copy adjusting block127that may generate a weighted output level. A weighted output level (also referred to as a weighted copy level) may be used to ensure that the wireless communication device102minimizes the effect of the PA output copy122at the output of the signal combining block116. The level of the PA output replica120may change as the PA110adjusts its gain to compensate for changes in the impedance of the matching network112and/or antenna114due to the channel effects. For example, as the impedance of the matching network112and/or antenna114changes due to load modulation or coupling with the remote device104, the current of the PA output replica120may change. Therefore, the level of the PA output replica120may differ from the level of the PA output copy122, which does not experience the channel effects.

However, subtracting too little or too much from the PA output replica120may result in the carrier residue being too large with respect to the desired modulated signal. The output copy adjusting block127may adjust the level of the PA output copy122to minimize the difference with the PA output replica120level.

The wireless communication device102may perform a phase lock on the incoming carrier. The incoming carrier phase, frequency and amplitude alignment may be estimated by processing the summing error. In an implementation, this may be accomplished using a phase/frequency and amplitude locked loop. The more the wireless communication device102achieves alignment of the phase/frequency with the amplitude, the less error is seen at the output. An adaptive algorithm may adjust the frequency, phase and amplitude parameters to minimize the error. To retain a reference clock derived from the external reader (i.e., remote device104), carrier alignment is the desired objective rather than cancellation of incoming carrier signal.

In yet another case, the operational mode124of the wireless communication device102may be target mode with active load modulation (ALM). In this operational mode124, the wireless communication device102is acting as the target and the remote device104is the reader. The wireless communication device102may receive a modulated signal from the remote device104. The wireless communication device102may also perform ALM with the remote device104.

In this operational mode124, a transmitted ALM sub-carrier is sent by the PA110. Again, the NFC block106maintains a controlled output impedance connection to the matching network112and antenna114, as opposed to leaving the circuit disconnected and at a higher impedance leading to un-damped responses and high induced voltage levels at the chip package pins that can damage the circuits.

The PA output replica120is fed to the signal combining block116for sensing the transmitted ALM and modulation of an incoming carrier from the remote device104. The PA output copy122is fed to the signal combining block116to strip the outgoing ALM sub-carrier and the incoming carrier to leave just the modulated signal on the incoming carrier from the remote device104.

Phase lock on the incoming carrier may be performed as described above. However, to retain a reference clock derived from the remote device104, cancellation of the outgoing ALM sub-carrier signal is desired.

In yet another case, the operational mode124of the wireless communication device102may be RF Polling mode. In this operational mode124, the wireless communication device102may poll for an external device (e.g., remote device104). The PA110may transmit an outgoing polling signal. The polling signal may be a low level carrier frequency sweep, multitone or wide-band (e.g., pulse, pseudo random binary sequence (PRBS), etc.) signal transmitted by the PA110.

The wireless communication device102may sense the outgoing polling signal and channel effects. The PA output replica120may be provided to the signal combining block116and may contain the transmitted polling signal and effects from properties of the output channel126. For example, if the remote device104enters the vicinity of the wireless communication device102, then the channel properties may change due to coupling between the wireless communication device102and the remote device104. Signal levels for the channel effects may be determined by subtracting at the signal combining block116the PA output copy122from the PA output replica120.

The wireless communication device102may determine the presence of a coupled object (e.g., remote device104) based on a change in the signal levels. As the remote device104comes closer to the wireless communication device102, then the difference between the PA output replica120and the PA output copy122may increase, indicating the presence of a coupled object.

In an implementation, the signal combining block116may not perform down-conversion during RF polling. In this implementation, the signal produced by the signal combining block116is a subtraction of the PA output replica120and the PA output copy122. In this case, the signal combining block116may be a block that performs time domain summing of the PA output replica120and the PA output copy122. The result will vary over the frequency band according to the channel properties. Down-conversion of this signal could happen later in the receiver118.

In another implementation, the full or partial receiver chain or just an analog-to-digital converter (ADC)129can be used to digitize the PA output replica120. In this implementation, the signal combining block116may be an ADC129of the receiver118. The wireless communication device102may sense the outgoing polling signal and channel effects by providing the PA output replica120to an input of the receiver ADC129.

In this implementation, the PA output replica120may be the input frequency of the ADC129. The PA output copy122may be used as a variable or multiplied clock frequency for the ADC129. The ADC129clock can be swept on or near to the same frequency as those in the transmitted polling signal, or swept at a multiple of the channel frequency to be analyzed, to digitize the entire channel bandwidth. Corresponding digital codes (e.g., DC codes) are therefore produced that capture the effects of the channel126on the frequencies within the channel bandwidth. If the input frequency and the clock frequency are the same at the ADC129, this mixes the frequency down to DC due to sampling the same voltage each time.

If the environment changes due to the presence of a remote device104, a resonance peak may move, this resonance peak movement due to a coupled object may be referred to as a coupled object artifact. This resonance peak movement may occur in terms of frequency polling or in terms of amplitude. If the resonance peak changes, then the digital code will change. The wireless communication device102may look at the digital codes to detect this movement. The movement of the digital codes may indicate the presence of the remote device104.

The effect on the resonance of the antenna114and matching network112and the resonance due to coupled objects (e.g., remote device104) in the vicinity of the wireless communication device102may be digitally recorded over the frequency range of the channel126. If a change occurs in the environment in relation to coupled objects, there will be a corresponding change in the resonance of the antenna/matching network and the resonance of the coupled object. In other words, there may be a shift (e.g., movement) of coupled object artifacts. This will be reflected in a change of digital codes at the corresponding frequencies of the channel126.

In an approach, the wireless communication device102may determine signal levels for the channel effects by using the PA output copy122at higher order frequencies as the clock of the receiver ADC129. In another approach, the wireless communication device102may determine the presence of a coupled object based on a change in the resulting directly down-converted signal levels. Down-conversion (e.g., to DC) here may be done directly by the ADC129by correlating the ADC129clock and input signal. In this approach, the wireless communication device102may determine signal levels for the channel effects by using the PA output copy122that is at or near to the same frequencies as those in the transmitted polling signal (i.e., PA output replica120) as the clock of the receiver ADC129. As described above, the changes in resonance due to a coupled object may be detected in changes to the digital codes generated by the ADC129. These digital codes may be used to determine signal levels for the channel effects.

The PA output replica120and PA output copy122signals have many possibilities for phase, frequency and amplitude alignments. These may be varied with respect to each other, and with respect to incoming received signals. The poly-phase, multi-tone and amplitude variable alignments may be implemented in analog, digital or a combination of both analog and digital portions of the NFC block106.

The described systems and methods will result in NFC-based communications utilizing fewer hardware components. Instead of discrete blocks for the various NFC functional activities (e.g., reader, target, polling, etc.), the NFC block106may realize different operational modes124using a single transmitter108and receiver118to implement different NFC functions. A desired result is to reduce the number of blocks and package pins in the NFC block106, which further may reduce the size and cost of the NFC block106.

FIG. 2is a flow diagram illustrating a method200for multi-mode inductively coupled communication. The method200may be performed by a wireless communication device102. The wireless communication device102may be configured with NFC circuitry for communication with a remote device104. The NFC circuitry may include an NFC block106and NFC antenna circuitry (e.g., an NFC antenna114and matching network112).

The wireless communication device102may determine202an operational mode124for inductively coupled communication. The wireless communication device102may perform inductively coupled communication using NFC. The wireless communication device102may determine whether to operate in a reader mode, a target mode or an RF polling mode. The operational mode124may be selected based on one or more applications running on the wireless communication device102.

The wireless communication device102may perform204the operational mode124by combining a transmit power amplifier (PA) output replica120and a PA output copy122at a signal combining block116of a receiver118. The PA output replica120may reflect effects of channel properties. The channel properties may include loading conditions in relation to at least one of the antenna114, matching network112, coupling to a remote device104, or load modulation. The PA output copy122may be unaffected by the channel properties.

In an implementation, the signal combining block116may include a summer that performs time domain summing of the PA output replica120and the PA output copy122. The PA output copy122may be subtracted from the PA output replica120. This implementation may be configured for cancellation and carrier correlation.

In another implementation, the signal combining block116may include a mixer. The mixer may perform frequency translation using the PA output replica120and the PA output copy122.

In yet another implementation, the signal combining block116may be an analog-to-digital converter (ADC)129of the receiver118that can be used to digitize the PA output replica120. In this implementation, the PA output replica120may be provided to an input of the receiver ADC129. The PA output copy122may be provided to the clock of the receiver ADC129.

The wireless communication device102may perform a reader mode with target load modulation as described in connection withFIG. 5. A target mode may be performed as described in connection withFIG. 6. A target mode with active load modulation (ALM) may be performed as described in connection withFIG. 7. An RF polling mode may be performed as described in connection withFIGS. 8-10.

FIG. 3is a block diagram illustrating one example of a wireless communication device302for multi-mode NFC. The wireless communication device302may include an NFC block306for performing NFC operations with a remote device304. For example, the NFC block306may establish a communication channel326between the wireless communication device302and a remote device304using NFC protocols.

The NFC block306may include a transmit power amplifier (PA)310aand a receiver318. The PA310amay receive a signal from a signal source328a. The PA310amay be coupled to a matching network312via two pins332a,b. In an implementation, the matching network312may include three capacitors330a-c. The matching network312may be coupled to an antenna314. In an implementation, the antenna314may be a coil or loop antenna.

The NFC block306may generate a PA output replica320that reflects the external output voltage and currents of the PA310. Therefore, the PA output replica320may replicate the effects of channel properties. These channel properties may include loading conditions in relation to at least one of the antenna314, matching network312, coupling to a remote device304and all load modulation conditions.

In an implementation, the PA output replica320may be generated using a circuit-level current/voltage mirror circuit that faithfully replicates a ratio of the PA output stage currents and voltages. In another implementation, the PA output replica320may be generated with current and voltage sensing transformers. The current and voltage sensing transformers may be part of an EMI filter. In yet another implementation, the PA output replica320may be generated with a coupler that measures reflected power waves (a) and incident power waves (b) instead of voltages and currents. The PA310voltage v is related to a and b as v=k(a+b), where k is a fixed constant related to the reference impedance for the coupler.

The NFC block306may generate a PA output copy322that is a scaled transmit signal copy. The PA output copy322is unaffected by the channel properties such as the effects of loading conditions due to the antenna314, matching network312, coupling to a remote device304and load modulation conditions. The PA output copy322may be a dummy transmit PA signal that is unloaded by the outside circuit. Since the PA output copy322does not need to be full size, the signal (voltage/current) amplitude may be scaled by adjusting the voltage/current ratios.

It should be noted that the same signal source328and PA310may be used to generate the PA output replica320and the PA output copy322. However, the NFC block306may independently change the phase and amplitude of the PA output copy322with respect to the PA output replica320. Thus, in one example, a separate digital-to-analog converter (DAC) may generate and scale the PA output copy322. Therefore, a separate signal source328band PA310bare depicted inFIG. 3for generating the PA output copy322.

The PA output replica320and the PA output copy322may be provided to a summer316. The summer316may be an implementation of the signal combining block116ofFIG. 1. The summer316may perform time domain summing of the PA output replica320and the PA output copy322. The PA output copy322may be subtracted from the PA output replica320. The output of the summer316may be provided to the receiver318. Down-conversion (either direct or intermediate frequency (IF)) and digitization may be done in the receiver318.

This implementation may be configured for cancellation and carrier correlation. Because the PA output replica320and PA output copy322are internally routed to the receiver path, this eliminates the need for external receiver package pins and associated external components.

FIG. 4is a block diagram illustrating another example of a wireless communication device402for multi-mode NFC. The wireless communication device402may include an NFC block406for performing NFC operations with a remote device404. For example, the NFC block406may establish a communication channel426between the wireless communication device402and a remote device404using NFC protocols.

The NFC block406may include a signal source428a, PA410aand a receiver418. The PA410amay be coupled to a matching network412via two pins432a,b. In an implementation, the matching network412may include three capacitors430a-c. The matching network412may be coupled to an antenna414.

The NFC block406may generate a PA output replica420and PA output copy422as described in connection withFIG. 3. As described above, the NFC block406may independently change the phase and amplitude of the PA output copy422with respect to the PA output replica420. Therefore, a separate signal source428band PA410bare depicted inFIG. 4for generating the PA output copy422. However, the same signal source428and PA410may be used to generate the PA output replica420and the PA output copy422.

In this implementation, the NFC block406may include a mixer416. The PA output replica420and the PA output copy422may be provided to the mixer416. The mixer416may be an implementation of the signal combining block116ofFIG. 1. The mixer416may perform frequency translation of the PA output replica420and the PA output copy422. The output of the mixer416may be provided to the receiver418. The output of the mixer416may be mapped to DC. The receiver418may perform digitization and reject the DC component from the mixer output signal.

FIG. 5is a flow diagram illustrating a method500for performing a reader mode with target load modulation. The method500may be implemented by a wireless communication device102. The wireless communication device102may be configured with an NFC block106for communication with a remote device104. The NFC block106may perform multiple operational modes124using a PA output replica120, a PA output copy122and a signal combining block116.

The wireless communication device102may determine502that the operational mode124for NFC is reader mode with target passive load modulation. In this operational mode124, the wireless communication device102is acting as a reader and the remote device104is the target.

The wireless communication device102may transmit504an outgoing carrier. The wireless communication device102may send the outgoing carrier to the remote device104. For instance, the PA110of the transmitter108may send the carrier to the matching network112and antenna114for transmission to the remote device104.

The wireless communication device102may sense506incoming load modulation of the outgoing carrier by providing the PA output replica120to the signal combining block116. The remote device104may receive the outgoing carrier and respond by performing passive load modulation on the carrier. The PA output replica120, which includes the incoming load modulation of the outgoing carrier, may be fed to the signal combining block116. In this way, the wireless communication device102may sense incoming load modulation of the outgoing carrier.

The wireless communication device102may strip508the outgoing carrier at the signal combining block116with the PA output copy122to isolate the incoming load modulation signal and carrier residue. For example, the signal combining block116may perform cancellation of the outgoing carrier. This may be accomplished by subtracting the PA output copy122from the PA output replica120. The resulting load modulation signal may be further processed by the receiver118.

In the case where the remote device104performs active load modulation (ALM), the PA output replica120may be fed to the signal combining block116for sensing the incoming active load modulation of the outgoing carrier. The PA output copy122may be fed to the signal combining block116to strip the outgoing carrier to leave just the incoming active load modulation signal and carrier residue.

FIG. 6is a flow diagram illustrating a method600for performing a target mode. The method600may be implemented by a wireless communication device102. The wireless communication device102may be configured with an NFC block106for communication with a remote device104. The NFC block106may perform multiple operational modes124using a PA output replica120, a PA output copy122and a signal combining block116.

The wireless communication device102may determine602that the NFC operational mode124is target mode. In this operational mode124, the wireless communication device102is acting as the target and the remote device104is the reader. The wireless communication device102may receive a modulated signal from the remote device104.

The wireless communication device102may transmit604a low level outgoing carrier to maintain a controlled output impedance connection at the matching network112and antenna114. This maintains a controlled output impedance connection to the matching network112and antenna114.

The wireless communication device102may sense606incoming modulation of an incoming carrier by providing the PA output replica120to the signal combining block116. The PA output replica120may be fed to the signal combining block116for sensing the incoming modulation of an incoming carrier from an external reader (e.g., remote device104).

The wireless communication device102may strip608the outgoing carrier and incoming carrier at the signal combining block116with the PA output copy122with a weighted output level to isolate the incoming modulation signal from the remote device104. For example, the signal combining block116may subtract the PA output copy122with a weighted output level from the PA output replica120. This may cancel out the outgoing carrier and the incoming carrier to leave just the incoming modulation signal and carrier residue.

FIG. 7is a flow diagram illustrating a method700for performing a target mode with active load modulation (ALM). The method700may be implemented by a wireless communication device102. The wireless communication device102may be configured with an NFC block106for communication with a remote device104. The NFC block106may perform multiple operational modes124using a PA output replica120, a PA output copy122and a signal combining block116.

The wireless communication device102may determine702that the NFC operational mode124is target mode with ALM. In this operational mode124, the wireless communication device102is acting as the target and the remote device104is the reader. The wireless communication device102may receive a modulated signal from the remote device104. The wireless communication device102may also perform ALM with the remote device104.

The wireless communication device102may transmit704an outgoing ALM sub-carrier. For example, a PA110may provide the ALM sub-carrier to the matching network112and antenna114for transmission to the remote device104. The wireless communication device102may also maintain a controlled output impedance connection to the matching network112and antenna114, as opposed to leaving the circuit disconnected and at a higher impedance, which leads to un-damped responses and high induced voltage levels at the chip package pins that can damage the circuits.

The wireless communication device102may sense706the outgoing ALM sub-carrier and incoming modulation of an incoming carrier by providing the PA output replica120to the signal combining block116. The PA output replica120may be fed to the signal combining block116for sensing706the outgoing ALM sub-carrier and the incoming modulation of the incoming carrier from an external reader (e.g., remote device104).

The wireless communication device102may strip708the outgoing ALM sub-carrier and the incoming carrier at the signal combining block116with the PA output copy122to isolate the incoming modulated signal on the incoming carrier. For example, the PA output copy122may be fed to the signal combining block116. The signal combining block116may subtract the PA output copy122from the PA output replica120. This may cancel out the outgoing ALM sub-carrier and the incoming carrier to leave just the incoming modulated signal and carrier residue.

FIG. 8is a flow diagram illustrating one configuration of a method800for performing an RF polling mode. The method800may be implemented by a wireless communication device102. The wireless communication device102may be configured with an NFC block106for communication with a remote device104. The NFC block106may perform multiple operational modes124using a PA output replica120, a PA output copy122and a signal combining block116.

The wireless communication device102may determine802that the NFC operational mode124is an RF polling mode. In this operational mode124, the wireless communication device102may poll for an external device (e.g., remote device104).

The wireless communication device102may transmit804an outgoing polling signal. The polling signal may be a low level carrier frequency sweep, multitone or wide-band (e.g., pulse, PRBS, etc.) signal transmitted by the PA110to the external outputs (e.g., matching network112and antenna114.

The wireless communication device102may sense806the outgoing polling signal and channel effects by providing the PA output replica120to the signal combining block116. The PA output replica120may contain the transmitted polling signal and effects from the output channel126properties.

The wireless communication device102may determine808signal levels for the channel effects by subtracting the PA output copy122from the PA output replica120at the signal combining block116. In this case, the signal combining block116may be a summer316block that performs time domain summing of the PA output replica120and the PA output copy122.

The wireless communication device102may determine810the presence of a coupled object (e.g., remote device104) based on a change in the signal levels. The result will vary over the frequency band according to the channel properties.

FIG. 9is a flow diagram illustrating another configuration of a method900for performing an RF polling mode. The method900may be implemented by a wireless communication device102. The wireless communication device102may be configured with an NFC block106for communication with a remote device104. The NFC block106may perform multiple operational modes124using a PA output replica120, a PA output copy122and a signal combining block116. In this implementation, the signal combining block116may include a receiver analog-to-digital converter (ADC)129

The wireless communication device102may determine902that the NFC operational mode124is an RF polling mode. In this operational mode124, the wireless communication device102may poll for an external device (e.g., remote device104).

The wireless communication device102may transmit904an outgoing polling signal. The polling signal may be a low level carrier frequency sweep, multitone or wide-band (e.g., pulse, PRBS, etc.) signal transmitted by the PA110to the external outputs (e.g., matching network112and antenna114.

The wireless communication device102may sense906the outgoing polling signal and channel effects by providing the PA output replica to an input of the receiver ADC129. The PA output replica120may contain the transmitted polling signal and effects from the output channel126properties.

The wireless communication device102may determine908signal levels for the channel effects by providing the PA output copy122at higher order frequencies to a clock of the receiver ADC129. The PA output copy122may provide a variable or multiplied clock frequency to the ADC129. The ADC129clock can be swept at a multiple of the channel frequency to be analyzed, in order to digitize the entire channel bandwidth. Corresponding digital codes may be produced that capture the effects of the channel126on the frequencies within the channel bandwidth.

The wireless communication device102may determine910the presence of a coupled object (e.g., remote device104) based on a change in the signal levels. The result will vary over the frequency band according to the channel properties.

FIG. 10is a flow diagram illustrating yet another configuration of a method1000for performing an RF polling mode. The method1000may be implemented by a wireless communication device102. The wireless communication device102may be configured with an NFC block106for communication with a remote device104. The NFC block106may perform multiple operational modes124using a PA output replica120, a PA output copy122and a signal combining block116. In this implementation, the signal combining block116may include a receiver analog-to-digital converter (ADC)129.

The wireless communication device102may determine1002that the NFC operational mode124is an RF polling mode. In this operational mode124, the wireless communication device102may poll for an external device (e.g., remote device104).

The wireless communication device102may transmit1004an outgoing polling signal. The polling signal may be a low level carrier frequency sweep, multitone or wide-band (e.g., pulse, PRBS, etc.) signal transmitted by the PA110to the external outputs (e.g., matching network112and antenna114.

The wireless communication device102may sense1006the outgoing polling signal and channel effects by providing the PA output replica to an input of the receiver ADC129. The PA output replica120may contain the transmitted polling signal and effects from the output channel126properties.

The wireless communication device102may determine1008signal levels for the channel effects by providing the PA output copy that is at or near to the same frequencies as those in the transmitted polling signal to a clock of the receiver ADC129. The PA output copy122may provide a variable or multiplied clock frequency to the ADC129. The ADC129clock can be swept on or near to the same frequency as those in the transmitted polling signal in order to digitize the entire channel bandwidth. Corresponding digital codes may be produced that capture the effects of the channel126on the frequencies within the channel bandwidth. In this case, the signal levels may be directly down-converted to DC. Down-conversion here may be done directly by the ADC129by having ADC129clock and signal correlated.

The wireless communication device102may determine1010the presence of a coupled object (e.g., remote device104) based on a change in the resulting directly down-converted signal levels. The result will vary over the frequency band according to the channel properties.

FIG. 11is a block diagram illustrating an exemplary schematic of an NFC system1100including a transceiver1160and a remote unit1172. The NFC system1100includes an NFC transceiver1160and a remote unit1172such as an NFC tag. The NFC transceiver1160may include a voltage power source1166, an NFC transceiver control circuit1168and a transmitter circuit1164. The NFC transceiver control circuit1168is powered by the voltage source1166, and connected to one or more transceiver loops1162.

The transceiver loops1162are hereinafter interchangeably used with coils or loop antennae. The coils and loop antenna may be made of conductive material, for example, an electromagnetic coil, through which an alternating current (AC)1170can flow. The transceiver loops1162may be circular, oval, and the like, although other sizes and shapes are possible.

For near-field communication, the AC current1170flowing through the transceiver loops1162can result in transmitting magnetic energy or magnetic flux1180at various frequencies (e.g., about 100 kHz to about 110 MHz). In a near-field case, the wavelength of the emitted frequencies may be much longer than the size of the loops1162on the NFC transceiver1160.

The remote unit1172includes a receiver circuit1174and a remote unit control circuit1176. If the remote unit1172is close enough to the NFC transceiver1160, the magnetic flux1180from the transceiver1160can get AC coupled onto one or more remote unit loops1178of conductive material, which can be an unpowered device (i.e., without a battery or other means of applying continuous power) having the electromagnetic coil and remote unit control circuit1176.

An oscillating AC current1182flowing in alternating directions in the remote unit control circuit1176can be rectified by a rectifying diode in the remote unit control circuit1176, which can cause a voltage to be built up across a bypass capacitor in the remote unit control circuit1176. Once the bypass capacitor has built up a sufficient voltage, the remote unit control circuit1176can become powered up and operational. By receiving coupled and modulated AC signal from the NFC transceiver1160, the remote unit1172can receive and detect information (e.g., commands) from the NFC transceiver1160.

Once operational, the remote unit control circuit1176may also send signals back to the NFC transceiver1160by changing the impedance seen by the remote unit loops1178. This can be accomplished by shunting or opening the remote unit loops1178with, for example, a switch. If the remote unit1172is close enough to the NFC transceiver1160, the modulated electromagnetic field generated by the remote unit loops1178in the remote unit1172can be coupled back onto the loops1162of the NFC transceiver1160. The signals sent back to the NFC transceiver1160can be slow and on the order of 100 bits of data, and provide information back to the transceiver1160such as the serial number or model number of the device to which the remote unit1172is attached, credit card number, personal identification information, security codes and passwords, and the like.

FIG. 12illustrates certain components that may be included within a wireless communication device1202. The wireless communication device1202may be a wireless device, an access terminal, a mobile station, a user equipment (UE), a laptop computer, a desktop computer, etc. For example, the wireless communication device1202ofFIG. 12may be implemented in accordance with the wireless communication device102ofFIG. 1.

The wireless communication device1202includes a processor1203. The processor1203may be a general purpose single- or multi-chip microprocessor (e.g., an Advanced RISC (Reduced Instruction Set Computer) Machine (ARM)), a special purpose microprocessor (e.g., a digital signal processor (DSP)), a microcontroller, a programmable gate array, etc. The processor1203may be referred to as a central processing unit (CPU). Although just a single processor1203is shown in the wireless communication device1202ofFIG. 12, in an alternative configuration, a combination of processors (e.g., an ARM and DSP) could be used.

The wireless communication device1202also includes memory1205in electronic communication with the processor1203(i.e., the processor can read information from and/or write information to the memory). The memory1205may be any electronic component capable of storing electronic information. The memory1205may be configured as random access memory (RAM), read-only memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor, EPROM memory, EEPROM memory, registers and so forth, including combinations thereof.

Data1207aand instructions1209amay be stored in the memory1205. The instructions1209amay include one or more programs, routines, sub-routines, functions, procedures, code, etc. The instructions1209amay include a single computer-readable statement or many computer-readable statements. The instructions1209amay be executable by the processor1203to implement the methods disclosed herein. Executing the instructions1209amay involve the use of the data1207athat is stored in the memory1205. When the processor1203executes the instructions1209, various portions of the instructions1209bmay be loaded onto the processor1203, and various pieces of data1207bmay be loaded onto the processor1203.

The wireless communication device1202may also include a transmitter1211and a receiver1213to allow transmission and reception of signals to and from the wireless communication device1202via an antenna1217. The transmitter1211and receiver1213may be collectively referred to as a transceiver1215. The wireless communication device1202may also include (not shown) multiple transmitters, multiple antennas, multiple receivers and/or multiple transceivers.

The wireless communication device1202may include a digital signal processor (DSP)1221. The wireless communication device1202may also include a communications interface1223. The communications interface1223may allow a user to interact with the wireless communication device1202.

The functions described herein may be implemented in software or firmware being executed by hardware. The functions may be stored as one or more instructions on a computer-readable medium. The terms “computer-readable medium” or “computer-program product” refers to any tangible storage medium that can be accessed by a computer or a processor. By way of example, and not limitation, a computer-readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-Ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. It should be noted that a computer-readable medium may be tangible and non-transitory. The term “computer-program product” refers to a computing device or processor in combination with code or instructions (e.g., a “program”) that may be executed, processed or computed by the computing device or processor. As used herein, the term “code” may refer to software, instructions, code or data that is/are executable by a computing device or processor.