U.S. patent application number 15/060147 was filed with the patent office on 2016-06-30 for wireless communication device and method for identifying the type of modulation among a plurality of modulation types in a near filed communication device.
The applicant listed for this patent is Proton World International N.V.. Invention is credited to Youssef Ahssini, Guy Restiau.
Application Number | 20160191279 15/060147 |
Document ID | / |
Family ID | 46875864 |
Filed Date | 2016-06-30 |
United States Patent
Application |
20160191279 |
Kind Code |
A1 |
Restiau; Guy ; et
al. |
June 30, 2016 |
WIRELESS COMMUNICATION DEVICE AND METHOD FOR IDENTIFYING THE TYPE
OF MODULATION AMONG A PLURALITY OF MODULATION TYPES IN A NEAR FILED
COMMUNICATION DEVICE
Abstract
A method for configuring a first near-field communication device
according to a modulation type transmitted by a second device,
wherein: a decoder of the first device is configured to decode an
overcoded type-B modulation; a signal received during a first time
slot corresponding to the duration of a symbol of an initialization
frame is decoded; and the first device is configured according to
the value of the decoded symbol to determine the modulation
type.
Inventors: |
Restiau; Guy; (Ramillies,
BE) ; Ahssini; Youssef; (Vilvoorde, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Proton World International N.V. |
Zaventem |
|
BE |
|
|
Family ID: |
46875864 |
Appl. No.: |
15/060147 |
Filed: |
March 3, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14348348 |
Mar 28, 2014 |
9312920 |
|
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PCT/EP2012/068646 |
Sep 21, 2012 |
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15060147 |
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Current U.S.
Class: |
455/41.1 |
Current CPC
Class: |
H04W 4/80 20180201; H04B
5/00 20130101; H04W 72/0446 20130101; G06K 7/10297 20130101; H04B
5/0031 20130101; H04L 27/0012 20130101 |
International
Class: |
H04L 27/00 20060101
H04L027/00; H04W 72/04 20060101 H04W072/04; H04W 4/00 20060101
H04W004/00; H04B 5/00 20060101 H04B005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2011 |
FR |
11/58817 |
Claims
1. A device, comprising: demodulation and decoding circuitry, which
in operation, decodes received signals according to a selected
modulation type of a plurality of modulation types; and
modulation-type selection circuitry, coupled to the demodulation
and decoding circuitry, wherein the modulation-type selection
circuitry, in operation, controls the demodulation and decoding
circuitry to decode a received signal as a type-B modulated signal
for a first time slot; and when a result of the decoding of the
first time slot as a type-B modulated signal is 00 in hexadecimal
notation, the modulation-type selection circuitry: controls the
demodulation and decoding circuitry to decode the received signal
as a type-B modulated signal for a second time slot: when a result
of the decoding of the received signal for the second time slot is
00 in hexadecimal notation, selects type-B modulation as the
modulation type of the received signal; and when a result of the
decoding of the received signal for the second time slot is
different from 00 in hexadecimal notation, selects type-15693-10 as
the modulation type of the received signal.
2. The device of claim 1 wherein said time slot has a duration of
9.44 microseconds.
3. The device of claim 1 wherein when the result of decoding the
first time slot is different from 00 in hexadecimal notation and
smaller than AA in hexadecimal notation, the modulation-type
selection circuitry selects type-15693-100 modulation as the
modulation type of the received signal.
4. The device of claim 1 wherein when the result of decoding the
first time slot is FC in hexadecimal notation, the modulation-type
selection circuitry selects type-A modulation as the modulation
type of the received signal.
5. The device of claim 1 wherein when the result of decoding the
first time slot is AA in hexadecimal notation, the modulation-type
selection circuitry selects type-C modulation as the modulation
type of the received signal.
6. The device of claim 1 wherein when the result of decoding the
first time slot is CC in hexadecimal notation, the modulation-type
selection circuitry selects type-C modulation as the modulation
type of the received signal.
7. The device of claim 1 wherein when the result of decoding the
first time slot is not included in a set of results {00, FC, AA,
CC} in hexadecimal notation, the modulation-type selection
circuitry selects type-15693-100 modulation as the modulation type
of the received signal.
8. The device of claim 1 wherein when the modulation-type selection
circuitry selects type-15693-100 modulation as the modulation type
of the received signal, the modulation-type selection circuitry
determines whether the received signal is a type 15693-100-4 signal
or a type 15693-100-256 signal.
9. The device of claim 1 wherein when the modulation-type selection
circuitry selects type-15693-10 modulation as the modulation type
of the received signal, the modulation-type selection circuitry
determines whether the received signal is a type 15693-10-4 signal
or a type 15693-10-256 signal.
10. A system, comprising: analog-front-end circuitry; and
digital-signal-processing circuitry coupled to the analog-front-end
circuitry, wherein the digital-signal-processing circuitry, in
operation, decodes a received signal as a type-B modulated signal
for a first time slot; and when a result of the decoding of the
first time slot as a type-B modulated signal is 00 in hexadecimal
notation: decodes the received signal as a type-B modulated signal
for a second time slot: when a result of the decoding of the
received signal for the second time slot is 00 in hexadecimal
notation, selects type-B modulation as the modulation type of the
received signal; and when a result of the decoding of the received
signal for the second time slot is different from 00 in hexadecimal
notation, selects type-15693-10 as the modulation type of the
received signal.
11. The system of claim 10 wherein said time slot has a duration of
9.44 microseconds.
12. The system of claim 10 wherein when the result of decoding the
first time slot is different from 00 and smaller than AA, the
digital-signal-processing circuitry selects type-15693-100
modulation as the modulation type of the received signal.
13. The system of claim 10 wherein when the result of decoding the
first time slot is FC in hexadecimal notation, the
digital-signal-processing circuitry selects type-A modulation as
the modulation type of the received signal.
14. The system of claim 10 wherein when the result of decoding the
first time slot is AA in hexadecimal notation, the
digital-signal-processing circuitry selects type-C modulation as
the modulation type of the received signal.
15. The system of claim 10 wherein when the result of decoding the
first time slot is CC in hexadecimal notation, the
digital-signal-processing circuitry selects type-C modulation as
the modulation type of the received signal.
16. The system of claim 10 wherein when the result of decoding the
first time slot is not included in a set of results {00, FC, AA,
CC} in hexadecimal notation, the digital-signal-processing
circuitry selects type-15693-100 modulation as the modulation type
of the received signal.
17. A method comprising: selecting a modulation type of a received
signal by: decoding the received signal as a type-B modulated
signal for a first time slot; and when a result of the decoding of
the first time slot as a type-B modulated signal is 00 in
hexadecimal notation: decoding the received signal as a type-B
modulated signal for a second time slot: when a result of the
decoding of the received signal for the second time slot is 00 in
hexadecimal notation, selecting type-B modulation as the modulation
type of the received signal; and when a result of the decoding of
the received signal for the second time slot is different from 00
in hexadecimal notation, selecting type-15693-10 as the modulation
type of the received signal; and decoding the received signal using
the selected modulation type.
18. The method of claim 17, comprising: when the result of decoding
the first time slot, in hexadecimal notation, is different from 00
and smaller than AA, selecting type-15693-100 modulation as the
modulation type of the received signal.
19. The method of claim 17, comprising: when the result of decoding
the first time slot is FC in hexadecimal notation, selecting type-A
modulation as the modulation type of the received signal.
20. The method of claim 17, comprising: when the result of decoding
the first time slot is AA in hexadecimal notation, selecting type-C
modulation as the modulation type of the received signal.
21. The method of claim 17, comprising: when the result of decoding
the first time slot is CC in hexadecimal notation, selecting type-C
modulation as the modulation type of the received signal.
22. The method of claim 17, comprising: when the result of decoding
the first time slot is not included in a set of results {00, FC,
AA, CC} in hexadecimal notation, selecting type-15693-100
modulation as the modulation type of the received signal.
Description
TECHNICAL FIELD
[0001] Embodiments generally relate to electronic circuits and,
more specifically, to near-field radio frequency communication
devices. Such devices are generally known as NFC (Near Field
Communication) devices.
DISCUSSION OF THE RELATED ART
[0002] More and more radio frequency communication devices are
capable of operating in near field with a fixed terminal or another
mobile device. In particular, most mobile phone type
telecommunication devices are now equipped with a near-field
communication (NFC) router.
[0003] It is generally spoken of NFC devices operating in card mode
(or emulating a card), as opposed to a second operating mode of
these devices, which is to emulate a card reader to cooperate with
another near-field device. The device then behaves as a
terminal.
[0004] There are different near-field communication standards. The
difference between such standards essentially is the modulation and
coding type of data to be transmitted. Formerly, transponders were
most often dedicated to one type of modulation. They are now
designed to be able to operate according to different modulation
types and can thus be configured to set this type for each new
transaction with a terminal.
[0005] The modulation type is most often set by the terminal, and
the transponder-type device modifies the configuration of its NFC
router to be able to communicate with the reader.
[0006] Usually, the router or the radio frequency front head
capable of operating according to different modulations
successively switches to these different modulations until it
recognizes a request transmitted by a reader. This however takes
time.
[0007] Further, some terminals are themselves capable of operating
according to different modulation types to be able to adapt to
transponders dedicated to a single type. In this case, the terminal
successively sends requests according to the different types until
it receives a response in one of the types. However, the terminal
should leave enough time between two types (generally on the order
of a few milliseconds) so that a configurable transponder also has
time to scan the different modulation types until both
configurations (terminal and transponder) match.
[0008] Such a configuration process is long and makes the device in
card mode risk never to detect a request.
SUMMARY
[0009] An embodiment is to overcome all or part of the
disadvantages of usual card-mode near-field telecommunication
devices.
[0010] Another embodiment is to provide a process for configuring a
device in card mode.
[0011] Thus, an embodiment provides a method for configuring a
first near-field communication device according to a modulation
type transmitted by a second device, wherein:
[0012] a decoder of the first device is configured to decode an
overcoded type-B modulation;
[0013] a signal received during a first time slot corresponding to
the duration of a symbol of an initialization frame is decoded;
and
[0014] the first device is configured according to the value of the
decoded symbol to determine the modulation type.
[0015] According to an embodiment, said duration approximately
corresponds to 9.44 microseconds.
[0016] According to an embodiment, said symbol is divided in 8 and
decoded by assigning a state 0 or 1 to each eighth.
[0017] According to an embodiment, if the first symbol is 00 in
hexadecimal notation, a second time slot of same duration as the
first one and consecutive thereto is decoded for type B.
[0018] According to an embodiment:
[0019] if a second symbol corresponding to the second time slot is
also 00 in hexadecimal notation, the decoder is configured for the
type-B modulation; and otherwise, the decoder is configured for the
type-15693 modulation.
[0020] According to an embodiment, if, in hexadecimal notation, the
first symbol is different from 00 and smaller than AA, the decoder
is configured for the 15693-type modulation.
[0021] According to an embodiment, if the first symbol is equal to
value FC in hexadecimal notation, the decoder is configured for the
type-A modulation.
[0022] According to an embodiment, if the first symbol is equal to
value AA in hexadecimal notation, the decoder is configured for the
type-C modulation.
[0023] Another embodiment provides a near-field reception device
comprising the above circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The foregoing and other features, and advantages will be
discussed in detail in the following non-limiting description of
specific embodiments in connection with the accompanying
drawings.
[0025] FIG. 1 is a simplified diagram of a system of the type to
which the embodiments which will be described apply;
[0026] FIG. 2 is a block diagram of an embodiment of an NFC router
configuration system;
[0027] FIG. 3 is a simplified timing diagram illustrating an
example of modulated signals received by an NFC router;
[0028] FIG. 4 shows timing diagrams illustrating initial phases of
communication according to different modulation types capable of
being used by an NFC router operating in card mode; and
[0029] FIG. 5 is a simplified flowchart of an NFC router
configuration mode.
DETAILED DESCRIPTION
[0030] The same elements have been designated with the same
reference numerals in the different drawings, where the timing
diagrams have been drawn out of scale. For clarity, only those
steps and elements which are useful to the understanding of the
described embodiments have been shown and will be detailed. In
particular, the circuits for generating communication frames
according to the different standards have not been detailed, the
described embodiments being compatible with usual standards.
Further, the generation of polling requests by a read or read/write
terminal has not been detailed either, the described embodiments
being here again compatible with usual terminals.
[0031] The embodiments which will be described aim at an NFC router
operating in card mode and at its configuration for a communication
with a reader.
[0032] FIG. 1 is a simplified drawing of an example of a
communication system of the type to which the embodiments which
will be described apply.
[0033] A mobile telecommunication device 1 (for example, a GSM-type
mobile device) is capable of communicating with a network
symbolized by an antenna 2. Device 1 is further equipped with a
near-field communication router 3 capable of communicating with a
terminal 4 (TERMINAL) for generating a radio frequency field.
[0034] Most often, a device 1 equipped with an NFC router is
capable of operating both in so-called reader mode and in so-called
card mode. In reader mode, device 1 and its NFC router 3 behave as
a read and write terminal of another near-field communication
device. In card mode, the mobile device operates as a contactless
electromagnetic transponder or chip card to communicate with a
terminal 4. There exist many alternative telecommunication devices
equipped with an NFC router, but all use the same principle: when
operating in card mode and within the range of a near-field
communication terminal, they wait for a request from this terminal
to respond thereto.
[0035] The embodiments which will be described hereinafter more
specifically refer to devices integrating both near-field
communication (NFC) and telecommunication means. The described
solutions however apply to any near-field communication device
capable of operating according to several modulation types or
standards.
[0036] When such a device is within the range of a terminal, it
successively switches to the different modulation types with which
it is capable of operating to detect the type according to which
the terminal sends its request and to be able to start a near-field
communication therewith.
[0037] In certain cases, the terminal itself is capable of
operating according to different types. In this case, it starts by
sending a request according to a first communication or modulation
type and then, in the absence of any response from a transponder,
it switches to another type, and so on. On the terminal side, this
operation continues in a loop as long as no response from a
transponder has been received.
[0038] Such usual solutions take time before the communication can
start. Further, the modulation type risks not being detected.
[0039] This problem becomes even more critical with the development
of NFC routers capable of operating according to different
modulation types and the multiplicity of multistandard
terminals.
[0040] The embodiments which will be described take advantage of
the specificities to the most frequent near-field communication
standards to shorten the time of detection of the modulation type
and avoid situations where no type is detected.
[0041] Any transmission from a near-field communication terminal to
a transponder (reference will be made to a card hereinafter) is
performed in amplitude modulation. The difference between
modulation types is due to the coding of the amplitude modulation
transmission to transmit the bits.
[0042] FIG. 2 is a simplified block diagram of an embodiment of a
modulation type selection device. The representation of FIG. 2 is
simplified and functional.
[0043] The NFC router is assumed to comprise an analog front end 12
(AFE) equipped with means for receiving the radio frequency
signals. In the example of FIG. 2, analog front end 12 is further
assumed to be equipped with means (symbolized by a signal Tx)
enabling to transmit towards the terminal. It is generally spoken
of a retromodulation from the transponder to the terminal. An
output of front end 12 is sent to a demodulator/decoder 14 (DECOD)
of the received signals. It for example is an amplitude
demodulation circuit associated with a digital decoder. Decoder 14
provides the received signals (Rx) to the other mobile
telecommunication device circuits (not shown). According to the
embodiment shown in FIG. 2, circuit 14 also delivers the
demodulated signal to a block 16 (SELECT) for selecting the
received modulation type (TYPE).
[0044] The function of decoder 14 is, from a modulation type with
which it is initially configured, to detect the real type of
modulation of the signal received from front end 12, in order to
configure decoder 14 for the rest of the transmission once the type
has been selected by block 16.
[0045] As will be explained hereinafter in relation with FIG. 4, it
is provided to use a decoding based on a so-called overcoded type-B
modulation to detect the different modulation types that may be
received.
[0046] In NFC routers, radio frequency communications are based on
standards respecting a carrier frequency of approximately 13.56
MHz. Transmissions from the terminal to the transponder are
amplitude-modulated, mainly according to four families of types,
called type A, type B, type C, and type 15693 (ISO standards
14443). The different types have different transmission speeds,
carrier modulation indexes, and data codings.
[0047] The transmission speed of types A and B is 106 kbits/s, 212
kbits/s, 424 kbits/s, or 848 kbits/s. The transmission speed of
type C is 212 kbits/s or 424 kbits/s. The speed of type 15693 is
6.64 kbits per second or 26.48 kbits/s.
[0048] The modulation index of type A is 100%. The modulation index
of type B is 10%. Type C has a modulation index ranging between 8
and 30%. Type 15693 has a modulation index of 100% (type noted
15693-100) or 10% (type 15693-10). Type 15693 at 6.64 kbits/s bears
reference 256 (15693-100-256 and 15693-10-256) and type 15693 at
26.48 kbits/s bears reference 4 (15693-100-4 and 15693-10-4).
[0049] FIG. 3 illustrates, in a simplified timing diagram, a usual
example of amplitude modulation transmission of bits at states 0
and 1 with a type-A modulation. These timing diagrams show examples
of the shape of voltage V recovered by front end 12. These signals
are carried by a carrier at 13.56 MHz and are
amplitude-modulated.
[0050] In the case of a terminal-to-transponder transmission
considered herein to detect, on the transponder side, the
modulation type transmitted by the terminal, the data bits are, in
type A, coded according to the position of a modulation-free
interval I (or at a level lower than the high no-load level for
other types such as type B) during a determined period T
representing a symbol. This modulation type is an ASK-type
modulation (amplitude shift keying). A bit 0 is decoded if pulse I
is at the beginning of a period T and a bit 1 is decoded if pulse I
is not at the beginning of period T. The duration of period T, and
thus of a symbol, is approximately 9.44 microseconds. The duration
of pulse I corresponds to the duration of the symbol divided by
4.
[0051] The amplitude modulation is performed by lowering a high
level since near-field communication systems basically are designed
for transponders extracting the power supply of the circuits
contained therein from the high-frequency field emitted by the
terminal.
[0052] The embodiments which will be described take advantage of
the fact that, whatever the modulation type, a transmission from
the terminal to the transponder starts by an initial phase
according to a specific coding but with symbols all having a
duration of approximately 9.44 microseconds (corresponding to a 106
kbits/s speed) independently from the modulation type.
[0053] An overcoding based on a unit duration corresponding to the
duration of a period of a sub-carrier used by these systems at a
frequency of approximately 847.5 kHz is then defined. This
sub-carrier is in particular used for a retromodulation from the
transponder to the terminal.
[0054] The performed overcoding amounts to sampling a symbol having
a duration of 9.44 microseconds over 8 bits (according to the
periodicity of the sub-carrier frequency). It is then provided to
interpret this overcoding of 8 bits per symbol to tell the
different modulation types from one another. In other words, a
symbol is divided into 8 elements and a state 0 or 1 is assigned to
each symbol eighth according to its (relative) low or high level.
In practice, this decoding is performed by a type-B demodulator
parameterized at approximately 847.5 kHz. It is thus sufficient to
interpret differently the value of a type-B demodulated symbol.
[0055] FIG. 4 shows timing diagrams according to different
modulation types to illustrate the selection mode used in relation
with FIG. 2. The first timing diagram illustrates the shape of
carrier SC approximately at 848 kHz (period of approximately 1.18
.mu.s). The following timing diagrams illustrate the respective
shapes of the symbols present at the beginning of a frame,
respectively according to the following types:
[0056] A: symbol representing a real bit (106k) in type A (FIG.
3);
[0057] B: 10 symbols at 0 followed by 2 symbols at 1;
[0058] 15693-10(or 100)-4: 1 symbol in the low state followed by 4
symbols in the high state, followed by a symbol in the low state
followed by 2 symbols in the high state;
[0059] 15693-10(or 100)-256: 1 symbol in the low state followed by
6 symbols in the high state, followed by one symbol in the low
state;
[0060] C-212 (type C at 212 kbits/s): alternation of pulses
representing pulses I of a type A at 0 and at 1; and
[0061] C-424 (type C at 424 kbits/s): alternations of 4 states 0
and 4 states 1 per symbol.
[0062] In FIG. 4, the codes taken by the different symbols over 8
bits have also been shown in hexadecimal notation.
[0063] The frames, which may be of initialization frame type,
illustrated in FIG. 4, are transmitted during relatively long time
periods to leave time for a transponder to detect the frame. For
example:
[0064] a type-B frame represents 94 microseconds;
[0065] a type-C-424 frame represents 112 microseconds;
[0066] a type-C-212 frame represents 224 microseconds; and
[0067] a frame 15693 represents approximately 75 microseconds.
[0068] Waiting each time for a full frame for the terminal in order
to consider a lack of compatibility with the transponder before
switching to another type of modulation takes time.
[0069] Further, applications in which near-field communications are
used generally are applications where a user brings his device
close to the terminal and where transactions should be performed
rapidly.
[0070] It is provided to use one or two 9.44-.mu.s durations
representing the transmission time of a 106-kbits/s symbol in a
starting phase, to determine the modulation type used by the
terminal during the sending of its start of frame.
[0071] FIG. 5 is a simplified flowchart of a selection mode
implemented by selector 16 of FIG. 2 to determine the type of
modulation transmitted by a terminal.
[0072] At the starting of the system (block 21, START), radio
frequency front end is woken up by the receiving of a signal from a
terminal and selector 16 initially configures decoder 14 to be able
to decode an overcoded type-B modulation (block 22, CONFIG TYPE B).
The no-load configuration of decoder 14 thus is type B.
[0073] Decoder 14 demodulates and decodes the received signal as if
it was a type-B modulation and sends the received bits to selector
14. The received bits are sent in parallel to the rest of the
transponder circuit but are not used for the time being. In
particular, as long as selector 16 has not validated the modulation
type by a signal intended for these circuits (a validation bit OK
intended for the device microcontroller), signal Rx is not
used.
[0074] The selector waits (block 23, WAIT/READ SYMBOL) for the
reception of 8 overcoded bits (of a symbol). This amounts to
decoding, in type B, a 9.44-.mu.s time slot, independently from the
received signal and from the coding performed by the modulation
type.
[0075] For simplification, the values of the symbols will be
arbitrarily expressed in hexadecimal notation hereinafter.
[0076] Once these 8 bits have been received and decoded, selector
16 determines whether these bits correspond to a symbol of value 00
(block 24, 00?).
[0077] If not (output N of block 24), this means that the
modulation is neither of type B nor of type 15693(100 or 10)-4. It
is then tested (block 25, <AA?) whether the value of the symbol
is smaller than value AA. If the answer is positive (output Y of
block 25), this means that the modulation is of type 15693-100.
Selector 16 then configures decoder 14 accordingly (block 26, TYPE
15693-100).
[0078] To be able to tell type 15693-100-4 from type 15693-100-256,
the time counter of radio frequency front end 12 is configured
(block 27, AFE TIMER) on the duration of 4 symbols and it is waited
for the reception of the next symbol. If, during this reception,
the time counter has expired (output Y of block 28, TIMER=0?), this
means a mode 15693-100-4 (block 29, TYPE 15693-(x)-4). In the
opposite case (output N of block 28), this means type 15693-100-256
(block 30, TYPE 15693-(x)-256).
[0079] At the end of the configuration, the system is capable of
providing (block 31, END) the properly-decoded frame to the rest of
the telecommunication device. Indeed, the selection of the type
which is performed in at most two symbols does not adversely affect
the reception and the frame can be immediately interpreted.
[0080] If the first symbol is not smaller than value AA (output N
of block 25), this means either a type A, or a type C.
[0081] It is then tested (block 32, FC?) whether the value of the
symbol is FC. If it is (output Y of block 32), selector 16
configures decoder 14 on type A (block 33, TYPE A). If it is not
(output N of block 32), it is checked whether the symbol is AA
(block 34, AA?). If it is, this means that the modulation is of
type C-424 (block 35, TYPE C). Otherwise, it is verified whether
the value of the symbol is CC (block 36, CC?). If it is (output Y
of block 36), the type is C-212 and the decoder is configured for
type C (block 35, TYPE C). Otherwise, this means that the
modulation is of type 15693-100 and it is returned to block 26 to
cover the rest of the uncertain symbols.
[0082] If the first symbol is 00 (output Y of block 24), it is
waited for the reception of the next symbol (block 37, WAIT/READ
SYMBOL) of a 9.44-.mu.s duration to differentiate a type B from a
15693 modulation. The value of this second symbol is compared with
zero (block 38, 00?). If it is zero, this means a type-B modulation
and the decoder is then appropriately configured (block 39, TYPE
B). If it is not (output N of block 38), this means that the
modulation is of type 15693-10 (block 40, TYPE 15693-10) and the
decoder is appropriately configured.
[0083] Once the decoder has been configured for type 15693-10, the
operations of block 27 to 30 are performed as at the output of
block 26 to determine whether the modulation is of type 4 or of
type 256.
[0084] In FIG. 5, the outputs of the configurations in type B, in
type C, and in type 15693 lead to block 31. Preferably, the type-A
configuration (output of block 33) is processed differently.
[0085] The foregoing description shows that by interpreting at most
two consecutive time slots having a duration corresponding to that
of a symbol of the initialization frames, it is possible to
configure the receiver whatever the modulation type from among the
above types by interpretation of the symbol as if it was overcoded
over 8 bits.
[0086] It is thus no longer necessary to wait for the end of a
frame, nor for a switching of the terminal to another modulation
type. As soon as it is properly configured according to the method
of FIG. 5, the device in card mode responds to the terminal by
using the right type of retromodulation, which is a function of the
modulation type.
[0087] This method may be used either to configure a device in near
field while a terminal only transmits according to a modulation
type, or to match the modulation of this near-field device with
respect to a terminal scanning the different modulation types. In
both cases, the devices are then capable of communicating
together.
[0088] This method may be used either to configure a device in near
field while a terminal only transmits according to a modulation
type, or to match the modulation of this near-field device with
respect to a terminal scanning the different modulation types. In
both cases, the devices are then capable of communicating
together.
[0089] Once the type has been identified by the selector, the
mobile telecommunication device is configured to send an
acknowledgement message to the terminal. Receiving this response,
the terminal knows that the transponder is capable of interpreting
the modulation that it transmits.
[0090] In a simplified embodiment, the above-described method only
detects some of the described modulation types.
[0091] For example, for a device only operating according to types
B and 15693, only tests 24, 25, and 38 will be performed and, in
case of a negative outcome of test 25, the device does not respond
and waits for the terminal to switch to another modulation
type.
[0092] Further, the order of the tests may be modified.
[0093] Various embodiments have been described. Various alterations
and modifications will readily occur to those skilled in the art.
In particular, the selection of the types detected by the
implementation of these embodiments depends on the concerned mobile
telecommunication device, provided for it to be capable of decoding
at least one type-B modulation.
[0094] Further, the practical implementation of the described
embodiments is within the abilities of those skilled in the art
based on the functional indications given hereabove. In particular,
the interpretation of the transmitted symbols may be performed by
the digital processing circuits usually present in a device
comprising an NFC router. It will however be ascertained to
parameterize the receive front end and the decoder on an
interpretation of a signal duration approximately corresponding to
9.44 microseconds.
* * * * *