Processing amplitude modulated signals

Abstract

A method of processing an amplitude modulated (AM) signal, the method comprising: receiving an AM signal comprising a sequence of encoded symbols, each symbol in the encoded sequence being from a set of predefined symbols, wherein each predefined symbol in the set of predefined symbols comprises, when encoded, an AM signal portion comprising one or more high amplitude signal periods and a low amplitude signal period, wherein the low amplitude signal period is in a different position in the AM signal portion for different predefined symbols in the set of predefined symbols; processing the received AM signal to measure a separation between two successive low amplitude signal periods in the received AM signal; identifying, based at least in part on the measured separation, a symbol of the sequence of symbols encoded in the received AM signal; and performing an action based on the identified symbol.

Description

Technical Field

[0001] This disclosure relates to amplitude-modulated signals. More specifically, but not exclusively, this disclosure relates to methods for processing amplitude-modulated signals and receiver apparatus for processing received amplitude-modulated signals. Background Technology

[0002] Amplitude modulation (AM) signals are used in a wide variety of applications. One such application is Near Field Communication (NFC) technology. NFC is a set of communication protocols that enable over-the-air communication between two electronic devices (e.g., a transmitter and a receiver) over a relatively short distance, such as 4 centimeters or less. NFC devices can use or have used RFID technology, where electromagnetic fields are used to identify and track tags. Tags can be attached to or embedded in various objects or surfaces. Tags may contain a radio receiver and a transmitter. When triggered by an electromagnetic signal from a nearby reader, the tag can be configured to transmit digital data, such as an identifier of the tag and / or an identifier of the object to which the tag is attached, back to the reader.

[0003] At the receiver device (e.g., an NFC tag), the AM signal is received from the transmitter device (e.g., an NFC reader). The AM signal encodes a sequence of symbols that form a command from the transmitter device. This signal is typically demodulated at the receiver device and then sampled to identify a specific modulation pattern representing a particular symbol encoded in the signal.

[0004] AM signals, such as those transmitted to NFC tags via NFC readers, typically consist of a sequence of high-amplitude and low-amplitude signal periods. Some applications, such as NFC Type 5 technology, can operate using 100% amplitude modulation. For signals with 100% amplitude modulation (also known as on / off keying OOK), the low-amplitude signal periods have zero amplitude. During such low-amplitude signal periods, clock recovery (i.e., the process of extracting timing information from the signal to allow sampling and thus symbol recognition) may not be straightforward or even possible because no signal is transmitted by the transmitter device during such periods.

[0005] This disclosure aims to alleviate the problems mentioned above. Alternatively or additionally, this disclosure aims to provide an improved method for processing AM signals. Alternatively or additionally, this disclosure aims to provide an improved receiver apparatus for receiving and processing AM signals. Summary of the Invention

[0006] According to a first aspect, this disclosure provides a method for processing amplitude-modulated (AM) signals, the method comprising:

[0007] Receive an AM signal containing a sequence of coded symbols, where each symbol in the sequence comes from a predefined set of symbols.

[0008] Each predefined symbol in the set of predefined symbols includes an AM signal portion during encoding. The AM signal portion includes one or more high-amplitude signal periods and low-amplitude signal periods, wherein the low-amplitude signal periods are located at different positions in the AM signal portion for different predefined signals in the set of predefined signal symbols. The received AM signal is processed to measure the interval between two consecutive low-amplitude signal periods in the received AM signal.

[0009] The symbols encoded in the received AM signal are identified, at least in part, based on the measurement interval; and

[0010] Actions are performed based on the identified symbols.

[0011] According to a second aspect of this disclosure, a receiver device is also provided, the receiver device comprising electronic circuitry configured to:

[0012] Receive an amplitude-modulated (AM) signal containing a sequence of coded symbols, each symbol in the sequence coming from a predefined set of symbols.

[0013] Each predefined symbol in the set of predefined symbols contains an AM signal portion during encoding. The AM signal portion contains one or more high-amplitude signal periods and low-amplitude signal periods, wherein the low-amplitude signal period is located at different positions in the AM signal portion for different predefined symbols in the set of predefined symbols.

[0014] The received AM signal is processed to measure the interval between two successive low-amplitude signal periods in the received AM signal;

[0015] The symbols encoded in the received AM signal are identified at least in part based on the measurement interval; and

[0016] Actions are performed based on the identified symbols.

[0017] It should be understood, of course, that features described with respect to one aspect of this disclosure may be incorporated into other aspects of this disclosure. For example, the methods of this disclosure may be incorporated into any features described with reference to the apparatus of this disclosure, and vice versa. Attached Figure Description

[0018] Embodiments of this disclosure will now be described by way of example only, with reference to the accompanying schematic drawings, in which:

[0019] Figure 1 A schematic diagram of a receiver device according to the present disclosure is shown;

[0020] Figure 2 A flowchart illustrating the steps of a method according to this disclosure is shown;

[0021] Figure 3 A schematic diagram of a receiver device according to the present disclosure is shown;

[0022] Figure 4 This illustrates a set of predefined symbols according to this disclosure;

[0023] Figure 5 This illustrates a set of commands according to this disclosure;

[0024] Figure 6 The set of symbol combinations according to this disclosure is shown; and

[0025] Figure 7 An exemplary signal diagram for a calibration process is shown according to this disclosure. Detailed Implementation

[0026] Figure 1 A schematic diagram of a receiver device 100 according to the present disclosure is shown. The receiver device 100 includes electronic circuitry 110 configured to process amplitude-modulated (AM) signals received by the receiver device 100, as described below. The electronic circuitry 110 may include all or part of an integrated circuit. The receiver device 100 also includes an antenna 120 for receiving the AM signals to be processed by the electronic circuitry 110. Figure 1 The dashed arrows in the diagram depict this. Antenna 120 may include a radio frequency (RF) antenna configured to receive RF signals.

[0027] Alternatively or concurrently, receiver device 100 includes a Near Field Communication (NFC) device. NFC is a set of communication protocols that enable over-the-air communication between electronic devices over relatively short distances. The NFC device may use or be used in RFID technology, where an electromagnetic field is used to identify and track tags. Tags may be attached to or embedded in various objects or surfaces.

[0028] Alternatively or alternatively, receiver device 100 includes an NFC tag device. The NFC tag device may include a radio receiver and a transmitter. When triggered by an electromagnetic interrogation signal from a nearby NFC reader device, the tag device may be configured to transmit digital data, such as an identifier of the tag and / or an identifier of the object to which the tag is attached, back to the reader device. The tag device may be referred to as a "target device," and the reader device may be referred to as an "initiator device." The NFC tag device may have a relatively simple and / or small form factor, for example, in the form of a sticker, tag, smart poster, access card, identity document, key pouch, or card. Alternatively or alternatively, receiver device 100 may include an RFID tag device that is not an NFC tag device.

[0029] Alternatively or alternatively, the receiver device 100 includes an NFC Type 5 tag device. The NFC Type 5 tag device is a type of NFC tag device compatible with the ISO / IEC 15693 standard. The NFC Type 5 device can be configured to operate with a 100% amplitude-modulated signal. Alternatively or alternatively, the receiver device 100 includes an NFC-V device and / or is configured to process NFC-V signals.

[0030] Alternatively, receiver device 100 may include a powerless device. That is, receiver device 100 may not include its own power source. An NFC tag device is an example of such a powerless device. The NFC tag device can instead draw power from the electromagnetic field generated by a nearby NFC reader device. A powerless device may also be referred to as a “passive device” because its action is only performed by that device in response to a prompt from another device (e.g., a reader device). Alternatively, receiver device 100 may not include a powerless device. That is, receiver device 100 may include a power supply device or an active device. For example, receiver device 100 may include or be contained within a mobile phone. The mobile phone may be configured to emulate a smart card or other NFC target device, for example, to perform a transaction. The methods described herein can also be applied to NFC peer-to-peer communication where both devices (“initiator” and “target”) are powered.

[0031] While the examples disclosed herein relate to NFC (e.g., NFC devices, NFC signals, etc.), it should be understood that the methods described herein can be more generally applied to systems that do not use or involve NFC technology but can still use AM signals. Therefore, in some instances, receiver device 100 does not include an NFC device, and the received AM signal does not include an NFC signal, etc.

[0032] As mentioned above, in Figure 1In the example shown, receiver device 100 includes antenna 120 configured to receive AM signals from transmitter device (not shown). For example, transmitter device may include NFC reader device. However, it should be understood that in alternative examples, receiver device 100 does not include antenna 120. For example, AM signals may be received at receiver device 100 from another device (not shown) including an antenna, configured to receive AM signals from transmitter device. This other device may then transmit the AM signals to receiver device 100 without using an antenna, for example, via a wired connection between the other device and receiver device 100. Therefore, in some examples, antenna 120 may be omitted from receiver device 100.

[0033] Alternatively or concurrently, receiver device 100 includes a flexible integrated circuit. Flexible integrated circuits are typically much thinner and more flexible than conventional integrated circuits, enabling their use in a wider range of applications. Flexible integrated circuits are particularly well-suited for use in or as NFC tags because their thinner, more conformable, and bendable physical properties facilitate integration into objects or surfaces. According to this disclosure, a “flexible integrated circuit” (flexible IC or flexIC) is a type of integrated circuit IC designed to be flexible and conformable, allowing it to be bent, twisted, and adapted to non-flat or irregular surfaces. Unlike conventional rigid integrated circuits, which are typically fabricated on silicon chips and are not flexible, according to this disclosure, flexible integrated circuits are fabricated on a flexible substrate using appropriate materials and thin-film processes. The substrate is typically formed from a suitable flexible polymer material. However, the flexible substrate can be formed from any other material that provides suitable electrical, chemical, and / or structural properties. The flexible substrate can be formed from a single common material, from multiple different materials, or from multiple different types of the same material (e.g., different polymers). The flexible substrate may, for example, contain one or more materials selected from the following list: flexible glass, polymer materials, metal oxide materials, resin materials, resist materials, foil materials, paper, insulating coated metal, or any other suitable material.

[0034] When polymer-based materials are used, the substrate may comprise one or more polymers selected from the following: polyethylene naphthalate, polyethylene terephthalate; polymethyl methacrylate; polycarbonate, polyvinyl alcohol, polyvinyl acetate, polyvinylpyrrolidone, polyvinylphenol, polyvinyl chloride, polystyrene, polyimide, polyamide (e.g., nylon); polyhydroxy ether, polyurethane, polycarbonate, polysulfone, parylene, polyarylate, polyetheretherketone (PEEK); acrylonitrile butadiene styrene (ABS), 1-methoxy-2-propyl acetate, benzocyclobutene (BCB), polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polybutylene adipate (PAD). terephthalate (PBAT), cellulose polymers, or any other suitable polymeric material.

[0035] When a metal oxide-based material is used, the substrate may contain one or more metal oxides selected from the following materials: Al2O3, SiO2, etc. x N y The substrate may contain one or more resins selected from the following: SiO2, Si3N4, or any other suitable metal oxide. When a resin-based material is used, the substrate may contain one or more photoresists selected from the following: UV-curable resins or any other suitable resins. When a photoresist-based material is used, the substrate may contain one or more photoresists selected from the following: nanoimprint resists, photoresists such as, for example, bisphenol A phenolic epoxy resin (SU-8) or polyhydroxybenzyl silsesquioxane, or any other suitable photoresists. When a foil-based material is used, the substrate may contain one or more foils selected from the following: polymer foils or any other suitable foils. When an insulating coated metal is used, the substrate may contain one or more insulating coated metals selected from the following: insulating coated stainless steel or any other suitable insulating coated metal.

[0036] Alternatively, receiver device 100 may not include a flexible IC. For example, receiver device 100 may be a silicon-based device.

[0037] Figure 2 A flowchart illustrating the steps of a method 200 for processing AM signals according to this disclosure is shown. Method 200 can be at least partially achieved through the above references. Figure 1The described receiver device 100 performs the action, and more specifically, through the electronic circuitry 110 of the receiver device 100. Method 200 provides a general solution for processing AM signals that does not require clock recovery (whether using a phase-locked loop or other clock recovery method), and is therefore applicable to a wider range of systems and applications compared to known methods, including low-cost and / or low-power systems, and / or systems with a relatively small footprint, such as flexible integrated circuits.

[0038] The first step of method 200, exemplified by item 210, includes receiving an AM signal. The AM signal can be received via antenna 120 of receiver device 100, or from another device. For example, the received AM signal may include a radio frequency (RF) signal. Alternatively, the received AM signal may include an NFC signal, such as an NFC-V signal.

[0039] The received AM signal contains a sequence of coded symbols. Each symbol in the coded sequence comes from a set of predefined symbols. Alternatively, the predefined symbols in the set of predefined symbols are defined according to NFC standards. For example, predefined symbols may be defined according to ISO / IEC 15693 and / or ISO / IEC 14443 standards. Alternatively, predefined symbols may not be defined according to NFC standards.

[0040] Each predefined symbol in the set of predefined symbols contains an AM signal portion during encoding, which includes one or more high-amplitude signal periods and low-amplitude signal periods. The low-amplitude signal periods are located at different positions within the AM signal portion for different predefined symbols in the set of predefined symbols. Therefore, as disclosed herein, a “symbol” corresponds to a specific signal pattern defined by its position within the pattern of low-amplitude signal periods. As disclosed herein, an “AM signal portion” refers to a portion of an AM signal, i.e., the time portion encoding a given symbol. For example, an AM signal may contain multiple consecutive portions, each encoding individual symbols, such that the overall AM signal encodes a sequence of multiple symbols, thereby constituting a command. As disclosed herein, a “signal period” refers to the period or duration of an AM signal. A given AM signal portion (corresponding to a symbol) contains multiple signal periods. As disclosed herein, a “high-amplitude signal period” refers to the period of an AM signal with a relatively high amplitude. As disclosed herein, a “low-amplitude signal period” refers to the period of an AM signal with a relatively low amplitude. A given AM signal can switch between high-amplitude signal periods and low-amplitude signal periods to encode information. That is, each high-amplitude signal period can be defined by a pair of low-amplitude signal periods on each side. Similarly, each low-amplitude signal period can be defined by a pair of high-amplitude signal periods. Alternatively, the high-amplitude signal periods within a given AM signal can have different durations, while each low-amplitude signal period has the same duration. Or, the low-amplitude signal periods can have different durations. All high-amplitude signal periods of a given AM signal can have the same amplitude, and all low-amplitude signal periods of a given AM signal can have the same amplitude.

[0041] Alternatively or alternatively, the received AM signal may contain 100% amplitude modulation (AM) signal. Therefore, the low-amplitude period of the received AM signal may have zero amplitude, while the high-amplitude period may have nominal or 100% amplitude. Alternatively or alternatively, the low-amplitude period may have an amplitude greater than zero. For example, the received AM signal may contain 5% AM, 10% AM, 15% AM, 20% AM, 25% AM, 30% AM, 35% AM, 40% AM, 45% AM, 50% AM, 55% AM, 60% AM, 65% AM, 70% AM, 75% AM, 80% AM, 85% AM, 90% AM, 95% AM, etc.

[0042] Alternatively, the received AM signal may include an on / off keying (OOK) signal. OOK is a type of Amplitude Shift Keying (ASK) modulation that represents digital data as the presence or absence of a carrier. That is, during the transmission of logic zero, no carrier is transmitted. This corresponds to a low-amplitude signal period with zero amplitude. OOK can be referred to as "100% ASK". Alternatively, the received AM signal may include ASK signals other than the OOK signal. For example, logic zero can be represented by a carrier with a non-zero amplitude but still reduced relative to the carrier amplitude used for logic one. The received AM signal may include 5% ASK signal, 10% ASK signal, 15% ASK signal, 20% ASK signal, 25% ASK signal, 30% ASK signal, 35% ASK signal, 40% ASK signal, 45% ASK signal, 50% ASK signal, 55% ASK signal, 60% ASK signal, 65% ASK signal, 70% ASK signal, 75% amplitude modulation signal, 80% ASK signal, 85% ASK signal, 90% ASK signal, 95% ASK signal, etc.

[0043] Alternatively or alternatively, the received AM signal may include an NFC signal. Alternatively or alternatively, the AM signal may be received from an NFC reader device. For example, the received AM signal may include an interrogation signal sent by the NFC reader device to the NFC tag device to identify the NFC tag device and / or the object attached to the NFC tag device.

[0044] The second step of method 200, exemplified by item 220, involves processing the received AM signal to measure the interval between two successive low-amplitude signal periods in the received AM signal. As disclosed herein, "interval" refers to the duration or period of the AM signal between two events. Measuring the interval between two successive low-amplitude signal periods is equivalent to measuring the duration of a given high-amplitude signal period, i.e., how long the given high-amplitude signal period is, since the given high-amplitude signal period is defined by low-amplitude signal periods on each side.

[0045] Alternatively, processing the received AM signal includes demodulating the received AM signal to obtain a demodulated signal. The low-amplitude signal period of the received AM signal may correspond to a pulse in the demodulated signal. Therefore, measuring the interval between successive low-amplitude signal periods in the received AM signal may include measuring the interval (e.g., time) between pulses in the demodulated signal. Alternatively, the received AM signal may not be demodulated before the measurement interval.

[0046] Alternatively, the processing performed at item 220 includes using a latch circuit to measure the interval. The latch circuit can be configured to store a counter value representing the duration of a given high-amplitude signal period, thereby enabling the measurement of the interval between successive low-amplitude signal periods. The latch circuit can be reset by a low-amplitude signal period (optionally, this low-amplitude signal period may correspond to a pulse in the demodulated signal obtained by demodulating the received AM signal). The latch circuit is an example of an asynchronous counter. In alternative instances, other asynchronous counters or synchronous counters can be used to measure the interval.

[0047] The third step of method 200, exemplified by item 230, includes identifying symbols of a sequence of symbols encoded in a received AM signal, at least in part, based on a measurement interval. The identity of a symbol can depend on the measurement interval, such that different values ​​of the measurement interval can be translated into different symbols. For example, a counter value obtained at item 220 (e.g., via a latching circuit) corresponding to the interval between successive low-amplitude signal periods can be translated into a specific symbol. Since each symbol is one of a set of predefined symbols, where each predefined symbol can be encoded as a portion of the AM signal having a low-amplitude signal period at different locations, a given symbol can be identified based on the measurement interval between successive low-amplitude signal periods in the received AM signal. That is, the position of the low-amplitude signal period in a given portion of the AM signal can be used to identify the symbol corresponding to that portion of the AM signal.

[0048] Therefore, the symbols encoded in the received AM signal can be identified without sampling the pulses in the demodulated signal obtained by demodulating the received AM signal. Consequently, clock recovery is not an issue and is not required in the currently described method. Even if clock information is lost, for example, even if the signal is 100% amplitude modulated, the AM signal can be decoded.

[0049] One known clock recovery method involves using a phase-locked loop (PLL). A PLL is an electronic circuit that continuously adjusts the voltage to match the frequency of the input signal and can be used to recover interrupted signals (e.g., amplitude-modulated signals with zero-amplitude periods). PLLs can be used in silicon technology. PLL-based clock recovery methods allow the length of a 100% modulation (i.e., no-signal) period to be measured, and the signal can then be decoded in the usual manner. This differs from measuring the interval between successive low-amplitude signal periods and using the measurement interval to deduce the sign, as disclosed herein. PLLs may require relatively stable input voltages and relatively large power consumption. Specifically, an accurate PLL may require extremely low variation in complementary transistor types and / or device characteristics. Furthermore, PLLs are typically large and power-intensive circuits. Therefore, implementing a PLL in some systems can be difficult, expensive, and / or complex, such as systems with significant variations in device characteristics within a single integrated circuit, systems lacking complementary transistor types, and / or systems requiring relatively low power consumption. Such a system can be a flexible integrated circuit. Therefore, the method described in this paper provides a general and low-power solution for decoding AM signals that does not require clock recovery (whether using PLL or other clock recovery methods), and is thus applicable to a wider range of systems and applications, including low-cost and / or low-power systems, compared to known methods.

[0050] Alternatively, the identification is further based on previously identified symbols encoded in the symbol sequence of the received AM signal. Alternatively, the previously identified symbols and the identified symbols (i.e., the symbols identified at item 230) are consecutive symbols encoded in the symbol sequence of the received AM signal. For example, a previously identified symbol may immediately precede the identified symbol in the sequence. It is known that a given symbol in the set of predefined symbols necessarily follows or necessarily does not follow another given symbol in the set of predefined symbols. Therefore, knowledge of previously identified symbols can help identify the current symbol, for example, by reducing the number of possible symbols that the current symbol can be. This improves the reliability and / or efficiency of symbol identification. Alternatively, the previously identified symbols are known or fixed symbols.

[0051] Alternatively, the measurement interval is a first interval, and identification is further based on the measurement of a previous interval between two successive low-amplitude signal cycles in the received AM signal. Alternatively, the previous interval and the first interval are consecutive intervals between pairs of low-amplitude signal cycles in the received AM signal. In other words, the previous interval and the first interval correspond to the duration of consecutive high-amplitude signal cycles in the received AM signal, since each high-amplitude signal cycle is defined by a low-amplitude signal cycle on each side. Therefore, symbol identification can be based on the measurement of two consecutive intervals between pairs of low-amplitude signal cycles (corresponding to the duration of two consecutive high-amplitude signal cycles). Using two consecutive intervals (the current interval and the previous interval) improves the accuracy and / or reliability of symbol identification. For example, some symbols or combinations of symbols in a predefined set of symbols may not be uniquely identified based on the measurement of a single interval, but may be uniquely identified based on the measurement of two consecutive intervals. Alternatively, each of the first interval and the previous interval is measured using a separate latching circuit. That is, two latching circuits can be used, each latching circuit storing a counter for a separate interval.

[0052] Alternatively, identification is further based on a measurement of another prior interval between two successive low-amplitude signal cycles in the received AM signal. Alternatively, this additional prior interval and the previous intervals (mentioned above) are consecutive intervals between pairs of low-amplitude signal cycles in the received AM signal. Therefore, symbol identification can be based on measurements of three consecutive intervals between pairs of low-amplitude signal cycles (corresponding to the durations of three consecutive high-amplitude signal cycles). Using three consecutive intervals (the current interval and two prior intervals) ensures that each symbol in the predefined set of symbols can be uniquely identified.

[0053] Alternatively, each of the first interval, the preceding interval, and yet another preceding interval is measured using a separate latching circuit. That is, three latching circuits can be used, each storing a counter value for its respective interval. The three counter values ​​can then be used to identify the symbol. For example, each symbol in a predefined set of symbols can correspond to one or more different sets of the three counter values ​​(corresponding to three consecutive intervals between pairs of low-amplitude signal periods), such that the three counter values ​​together uniquely identify the symbol. The three latching circuits can together form a state machine.

[0054] The fourth step of method 200, illustrated by project 240, involves performing an action based on the identified symbol.

[0055] Alternatively, the action at item 240 involves using the identified symbol to identify one or more further symbols encoded in the received AM signal. For example, it is known that a given symbol necessarily follows other known symbols in the sequence, and therefore the identified symbol can be used to identify subsequent symbols.

[0056] Alternatively or concurrently, the symbol sequence encoded in the received AM signal represents a command, and the execution action includes determining the command. The command may be determined based on the identified symbol and, alternatively, one or more previously identified symbols in the sequence. Alternatively or concurrently, the command may include NFC commands, such as NFC-V commands. The command may include ISO / IEC 15693 commands, i.e., commands from a set of commands defined by the ISO / IEC 15693 standard. The execution action may include identifying a command from a predefined set of commands. The command may include requests and / or instructions. This command may be generated by a transmitter device such as an NFC reader device.

[0057] Alternatively or alternatively, the execution of the action includes generating a signal in response to a determined command. The signal can be transmitted from the receiver device 100 via the antenna 120, for example, to an NFC reader device. This signal may include an identifier of the receiver device 100, the status of the receiver device 100, one or more parameters of the receiver device 100, etc. Alternatively or alternatively, the execution of the action includes multiple steps, such as determining a command represented by a received AM signal, generating a response to the determined command, and transmitting a signal containing the response.

[0058] Alternatively or concurrently, method 200 includes a step (not shown) of identifying a predefined symbol calibration sequence in the received AM signal. Method 200 may also include a step (not shown) of determining timing parameters of the received AM signal based on the calibration sequence. In such cases, the interval between two successive low-amplitude signal periods (performed at item 220) is measured based on the determined timing parameters of the received AM signal. In some cases, different AM signals may have different timing parameters, which can affect the measurement of the interval between two successive low-amplitude signal periods. By using a predefined symbol calibration sequence to determine the timing parameters for a specific AM signal, the interval can be measured more accurately and / or more reliably.

[0059] Alternatively or alternatively, each symbol in the coded symbol sequence contains multiple bits, each bit having a fixed bit duration. For example, each symbol may contain 8 bits, where at least one bit is a low-amplitude signal period. Alternatively or alternatively, the timing parameters for determining the received AM signal include a fixed bit duration. As disclosed herein, "bit duration" refers to the duration of each bit in a given signal. "Bit duration" may also be referred to as "bit length." While the bit duration is fixed for a given signal (i.e., each bit in a given signal has the same duration), the bit duration can vary between different signals. Therefore, the timing parameters for determining the received AM signal may include determining the bit duration for that signal. The bit duration may correspond to the duration of a low-amplitude signal period, since in some instances, each low-amplitude signal period may contain 1 bit. Since different signals may use different bit durations, this can affect the measurement of the interval between successive low-amplitude signal periods. For example, the measurement interval determined to be 5 or 6 bits may depend on the duration of each bit. Therefore, by using a calibration sequence to determine the fixed bit duration of the AM signal used for reception, the interval between successive low-amplitude signal periods can be measured more accurately and / or more reliably. This situation is described in more detail below. Alternatively, the timing parameters for the signal include parameters other than the fixed bit duration for the signal. Alternatively, the bit duration does not vary between different signals.

[0060] Figure 3 A receiver device 300 according to the present disclosure is schematically shown. The receiver device 300 may be similar to the above reference. Figure 1 The receiver device 100 described herein and / or has similar functionality. The receiver device 300 may be configured to perform at least some of the methods described above.

[0061] exist Figure 3In the example shown, receiver device 300 receives an AM signal via antenna 305. The AM signal includes an RF signal. In this example, the AM signal is a 100% amplitude-modulated signal and is received by a self-reader device (not shown). RF demodulator 310 demodulates the received AM signal and extracts a data signal, wherein the low-amplitude signal period of the received AM signal is converted into pulses. Data counter 315 then counts (or measures) the intervals between pulses in the demodulated data signal. That is, the intervals between pairs of low-amplitude signal periods in the received AM signal are measured. Symbol identifier 320 then converts the counter value obtained by data counter 315 into a symbol from a predefined set of symbols. The identified symbol is fed to command interpreter 325 in the form of a 3-bit code unique to that symbol. Command interpreter 325 then determines the command encoded in the received AM signal from the sequence of identified symbols. Command interpreter 325 also queries laser programmable read-only memory LPROM 330 to determine the response for the command. The response is then encoded into an ISO15693 frame and transmitted to a transmission encoder 335, which generates a signal based on the response. Manchester encoding can be used to encode the response signal. A load modulator 340 generates a negative RF response signal, which is fed to an antenna 305 for transmission to a reader device.

[0062] Receiver device 300 may include compared to Figure 3 The components shown may include more, fewer, or different components. For example, in some instances, each of the antenna 305, RF demodulator 310, command interpreter 320, LPROM 330, TX encoder 335, and load modulator 340 may be omitted. The data counter 315 and symbol identifier 320 may work together with the components referenced above. Figure 1 and Figure 2 The described electronic circuit 110 functions similarly. However, it should be understood that in other instances, Figure 3 These two functional blocks can be combined into a single block.

[0063] Figure 4 A table showing a set 400 of predefined symbols according to this disclosure. For example... Figure 4 As shown, the set 400 of predefined symbols contains six symbols: E, A, B, C, D, and F. Different symbol sequences from set 400 can form different commands and can be encoded in the AM signal. Each command can begin with symbol E (also known as the “Start of Frame”, SOF) and end with symbol F (also known as the “End of Frame”, EOF). In some cases, a command may contain different symbol arrangements that do not begin with symbol E and / or do not end with symbol F. Alternatively, the set 400 of predefined symbols may be defined according to NFC-related standards such as ISO 15693. Different predefined symbols may be used in other instances.

[0064] Alternatively, each symbol may consist of 8 bits. As used herein, a “bit” refers to a signal period with a fixed duration, i.e., the bit duration. The bit duration can be between 6 microseconds and 12 microseconds. For example, the bit duration (i.e., the fixed duration of each bit in the signal) could be 9.4 microseconds. Each symbol contains 7 high-amplitude bits and 1 low-amplitude bit, indicated by “P”. An exception is symbol E, which contains 2 low-amplitude bits. In any case, each symbol includes at least one low-amplitude bit. Each symbol in the set 400 of predefined symbols contains an AM signal portion during encoding, such as… Figure 4 As stated in the table. For example, symbol A is encoded as a signal portion containing one high-amplitude bit, followed by one low-amplitude bit, followed by six high-amplitude bits; symbol B is encoded as a signal portion containing three high-amplitude bits, followed by one low-amplitude bit, followed by four high-amplitude bits, and so on. The low-amplitude bit (“P”) is located in different positions within the signal portion for different symbols. For example, P is located in the second position (out of eight) for symbol A and in the fourth position (out of eight) for symbol B.

[0065] Figure 5 A table illustrating a set 500 of commands according to an embodiment is provided. The set 500 of commands contains 13 commands, but it should be understood that a different number of possible commands may exist in other embodiments. Commands may be defined according to NFC-related standards such as ISO / IEC 15693. Each of the commands can be transmitted to an NFC tag via an NFC reader device. Each of the commands contains information from the above references. Figure 4 The description describes a sequence of symbols from a predefined set of 400 symbols. Each command begins with symbol E and ends with symbol F. For each command, symbol E is followed by symbol C. This can be used to determine the bit duration for a given signal, as described in more detail below.

[0066] As mentioned above, each symbol in the set 400 of predefined symbols contains an 8-bit signal portion when encoded, of which at least one bit is a low-amplitude bit (“P”). Figure 5 This illustrates how such signal segments can be combined into a single AM ​​signal for different commands. For example, a command containing the symbol sequence ECBCABAAAF can be encoded as: P-4-P-7-P-5-P-9-P-3-P-9-P-5-P-7-P-7-P-8-P-5-P, where each number indicates the period of the high-amplitude signal formed by that number of bits. (The last sentence appears to be incomplete and possibly refers to a different context.) Figure 5As can be seen, the longest interval between two low-amplitude signal periods is 13 bits (e.g., where symbol A is followed by symbol D), and the shortest interval between two low-amplitude signal periods is 1 bit (e.g., where symbol D is followed by symbol A). A single bit is equivalent to 2.5 cycles of a 424 kHz clock with a bit duration of 6 microseconds, or equivalent to 4 cycles of a 424 kHz clock with a bit duration of 9.4 microseconds.

[0067] Alternatively, a single measurement interval between successive low-amplitude signal periods may be sufficient to identify the symbol. For example, reference Figure 5 A single measurement interval of 3 bits may correspond only to symbol A, a single measurement interval of 11 bits may correspond only to symbol C, and so on. However, in some cases, a single measurement interval may not be sufficient to uniquely identify each symbol in a predefined set of symbols. For example, reference... Figure 5 A 7-bit interval can indicate any of the symbols A, B, or C. Two measurement intervals (the current interval and a previous interval) between pairs of low-amplitude signal periods are sufficient to uniquely identify most symbols. However, reference... Figure 5 The successive measurement intervals of 7 bits and 9 bits can correspond to the AB transition to identify symbol B, or to the BC transition to identify symbol C. Therefore, three measurement intervals (the current interval and two previous intervals) can be used, allowing for the unique identification of each symbol.

[0068] Figure 6 Show Figure 5 The set 600 shows all possible three-interval combinations in the commands shown, and the symbols indicating such combinations. (e.g.) Figure 6 As shown, each three-interval combination uniquely identifies a symbol. For example, sequence 1-7-7 may indicate only symbol A, sequence 3-7-9 may indicate only symbol B, and so on, where each number refers to the duration (in bits) of the respective interval between pairs of low-amplitude signal periods.

[0069] An alternative to using three-spaced combinations to interpret symbols is to treat the entire data byte stream as a pattern and map these patterns to commands. For example, as Figure 5 As shown, each command contains either 56 high-amplitude bits (also referred to as "data bits") or 84 high-amplitude bits, without counting EOF symbols. The high-amplitude bits between pairs of low-amplitude signal periods can be referred to as "data bit groups." For example, it can be seen that an 84-bit command has a 3-9 or 3-7 pattern after an initial 4-7 pattern, while a 56-bit command does not. However, in any case, the interval between successive low-amplitude signal periods is measured and used to identify symbols (e.g., the symbols that make up the command).

[0070] Therefore, the method described herein provides a deductive algorithm for determining a signal code by timing the duration of a high-amplitude signal period (i.e., the interval between low-amplitude signal periods). A finite number of symbol combinations may exist, which may contain a specific signal code, such as a command, that allows this deduction. This enables the complete reader command to be recognized as consecutive symbols are deduced.

[0071] Figure 7 An exemplary signal diagram 700 is shown for determining the fixed bit duration of a received AM signal according to this disclosure. Determining the fixed bit duration can be considered a calibration process before identifying the symbols encoded in the received AM signal. The fixed bit duration is an example of a timing parameter of the received AM signal. For different signals, the bit duration can vary between 6 microseconds and 14 microseconds. Alternatively or additionally, this calibration process is not performed. For example, the bit duration for a given signal may be known, and / or the encoded symbols may be identified without determining the bit duration. Furthermore, if a high-frequency counter is used to measure the interval between periods of a low-amplitude signal, a calibration step may not be required. The bit duration may also be referred to as the “modulation width” because a low-amplitude signal period may have a single bit duration and may correspond to a pulse of a specific width in the demodulated signal obtained by demodulating the received AM signal.

[0072] The calibration process can be based on a predefined symbol calibration sequence in the received AM signal. Alternatively, the predefined calibration sequence contains the first two symbols of the received AM signal. Specifically, it is known that each coded command begins with the sequence EC, where E and C are from the above reference. Figure 4 The description includes a set of 400 predefined symbols. This knowledge (i.e., the existence of a predefined calibration sequence) can be used to determine the bit duration of the signal used for reception. The calibration sequence may contain other symbols and / or another number of symbols.

[0073] like Figure 7 As shown in the bottom column, variables x and c can be assigned to counter states. It should be noted that... Figure 7 The assignment variable c in the bottom column is different from what is described elsewhere (and in Figure 7 The symbol C (shown in the second column) is used. The assigned variable c indicates the count for each full 106kHz clock cycle (848kHz clock is used in this example). The assigned variable x indicates the count from the falling edge of the DEMOD signal to the next “clean” 106kHz clock cycle.

[0074] To find x and c, sum the counts between the two-state thixotropic changes in the DEMOD. For symbol E, this results in 3c + x, and for symbol C, it is 6c + x. These values ​​are then subtracted from each other. That is, CE = 6c + x - 3c - x = 3c. To find x, subtract the result from symbol E, i.e., E - 3c = 3c + x - 3c = x. To find 3c, a small lookup table can be used instead of implementing div / 3 in the hardware.

[0075] Once x and c are known, the symbol can be identified, although the bit duration may vary. Specifically, once x and c are known, and the end of the calibration sequence EC is known, other symbols can be found by considering the distance from the current symbol to the next symbol.

[0076] To support other possibilities for the calibration sequence, such as E+A, E+B, etc., the specific calculations will be different, but the calibration process can still be performed because E = 3c + x is fixed and known.

[0077] Although this disclosure has been described and illustrated with reference to specific embodiments or examples, those skilled in the art will understand that the disclosure itself can lead to many different variations not specifically illustrated herein. Some possible variations will now be described by way of example only.

[0078] Alternatively or alternatively, the receiver device 100 includes or is included in an NFC tag device. Alternatively or alternatively, the receiver device 100 includes or is included in an NFC reader device. For example, the receiver device 100 may include or be included in a mobile phone or other computing device capable of receiving NFC signals from an NFC tag device.

[0079] Alternatively, the received AM signal may be a 100% amplitude modulated signal. Alternatively, the received AM signal may not be a 100% amplitude modulated signal. That is, the low-amplitude signal period in the received AM signal may have a non-zero amplitude. In this case, the clock information in the signal may not be lost (unlike in the case of 100% modulation). However, regardless of whether the clock information is lost, the currently disclosed method can still be used to identify symbols and thus decode commands. The currently disclosed method therefore provides a general solution applicable to both 100% and <100% amplitude modulated signals.

[0080] Where integers or elements having known, obvious, or foreseeable equivalents are mentioned in the preceding description, such equivalents are incorporated herein as if set forth separately. Reference should be made to the claims used to determine the true scope of this disclosure, which should be interpreted as covering any such equivalents. The reader should also understand that the whole or features of this disclosure described as preferred, advantageous, convenient, or similar are optional and do not limit the scope of the independent claims. Furthermore, it should be understood that such optional wholes or features, while potentially beneficial in some embodiments of this disclosure, may not be desirable in other embodiments and therefore may not be present.

Claims

1. A method for processing amplitude modulation (AM) signals, the method comprising: Receive an AM signal containing a sequence of coded symbols, each symbol in the sequence being drawn from a predefined set of symbols. Each predefined symbol in the set of predefined symbols includes an AM signal portion during encoding. The AM signal portion includes one or more high-amplitude signal periods and low-amplitude signal periods, wherein the low-amplitude signal periods are located at different positions in the AM signal portion for different predefined symbols in the set of predefined symbols. The received AM signal is processed to measure the interval between two successive low-amplitude signal periods in the received AM signal; The symbols of the symbol sequence encoded in the received AM signal are identified, at least in part, based on the measurement interval; as well as Actions are performed based on the identified symbols.

2. The method of claim 1, wherein the received AM signal comprises a 100% amplitude modulation signal.

3. The method of any of the preceding claims, wherein the received AM signal includes an on / off key control OOK signal.

4. The method of any of the preceding claims, wherein the identification is further based on previously identified symbols of the symbol sequence encoded in the received AM signal.

5. The method of claim 4, wherein the previously identified symbol and the identified symbol are consecutive symbols encoded in the symbol sequence in the received AM signal.

6. The method of any of the preceding claims, wherein the processing comprises using a latching circuit to measure the interval.

7. The method as described in any of the preceding claims, The measurement interval is the first interval, and The identification is further based on a measurement of the previous interval between two successive low-amplitude signal cycles in the received AM signal.

8. The method of claim 7, wherein the preceding interval and the first interval are consecutive intervals between low-amplitude signal period pairs in the received AM signal.

9. The method of claim 7 or claim 8, wherein the identification is further based on a measurement of another previous interval between two successive low-amplitude signal cycles in the received AM signal.

10. The method of claim 9, wherein the further prior interval and the prior interval are consecutive intervals between low amplitude signal period pairs in the received AM signal.

11. The method of claim 9 or claim 10, wherein each of the first interval, the previous interval, and the further previous interval is measured using a separate latching circuit.

12. The method as described in any of the preceding claims, The symbol sequence encoded in the received AM signal represents a command, and The execution of the action includes determining the command based on the identified symbols in the sequence and one or more previously identified symbols.

13. The method of claim 12, wherein performing the action comprises generating a signal that includes a response to the command determined.

14. The method of any of the preceding claims, wherein the received AM signal comprises a near field communication (NFC) signal.

15. The method of claim 14, wherein the AM signal is received from an NFC reader device.

16. The method of any preceding claim, wherein the predefined symbols in the set of predefined symbols are defined according to the Near Field Communication (NFC) standard.

17. The method as claimed in any of the preceding claims, wherein the method comprises: Identify a predefined symbol calibration sequence in the received AM signal; and The timing parameters of the received AM signal are determined based on the calibration sequence. The interval between the two successive low-amplitude signal cycles is measured based on the timing parameters determined by the received AM signal.

18. The method of claim 17, Each symbol in the coded symbol sequence contains multiple bits, each bit having a fixed bit duration, and The timing parameter for determining the received AM signal includes the fixed bit duration.

19. A receiver device comprising electronic circuitry, the receiver device being configured to: Receive an amplitude-modulated (AM) signal containing a sequence of coded symbols, each symbol in the sequence being drawn from a predefined set of symbols. Each predefined symbol in the set of predefined symbols includes an AM signal portion during encoding. The AM signal portion includes one or more high-amplitude signal periods and low-amplitude signal periods, wherein the low-amplitude signal periods are located at different positions in the AM signal portion for different predefined symbols in the set of predefined symbols. The received AM signal is processed to measure the interval between two successive low-amplitude signal periods in the received AM signal; The symbols of the symbol sequence encoded in the received AM signal are identified at least in part based on the measurement interval; and Actions are performed based on the identified symbols.

20. The receiver device of claim 19, wherein the receiver device comprises a near field communication (NFC) device.

21. The receiver device of claim 20, wherein the NFC device includes an NFC tag device.

22. The receiver device of claim 21, wherein the NFC tag device comprises an NFC Type 5 tag device.

23. The receiver device according to any one of claims 19-22, wherein the receiver device comprises a flexible integrated circuit.

24. The receiver device according to any one of claims 19-23, wherein the receiver device comprises a powerless device.

25. The receiver device according to any one of claims 19-24, wherein the receiver device includes an antenna configured to receive the AM signal from the transmitter device.

26. The receiver device of claim 25, wherein the transmitter device comprises a near-field communication (NFC) reader device, and wherein the received AM signal comprises an NFC signal.

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