MXPA99007551A - Apparatus and method for delivering power to a contactless portable data source - Google Patents

Abstract

The present invention ecompasses a terminal device and method of powering a portable device therefrom, by transmitting in two modes of operation. In particular, the terminal transmits to the portable data device, in a first mode of operation (201), a power signal at a first level and a data signal using a first modulation format and a first bit rate. The terminal further transmits, in a second mode of operation (205), a power signal at a second level and a data signal using a second modulation format and a second bit rate. The terminal is capable of determining a requirement to change modes of operation (203) and changes modes in response to changing power requirements of the portable data device.

Description

APPARATUS AND METHOD FOR DISTRIBUTING ENERGY TO A PORTABLE CONTACT DATA SOURCE Field of the Invention This invention relates generally to data transmission systems that include terminals and portable data devices, and in particular to a method for powering portable data devices in such a data transmission system.

Background of the Invention It is known that data transmission systems include terminal devices (sometimes called readers or exciters) and portable data devices (sometimes called smart cards or cards). It is well known that current portable data devices include memory devices and processors that require power from the terminal device. Once that portable data device (which can be contactless or contact / non-contact - sometimes referred to as combi cards) enters the excitation field of the terminal device, the energy and data can then be transferred from the terminal device to the portable data device. Many factors have an effect on the apparent energy observed by the portable data device. In particular, the variation of proximity to the terminal device and the different applications / transactions have an impact on the energy that is being observed and consumed by the data device. These variations in energy levels cause operation problems in the cards, as described below. Depending on the function that is being exercised by the card at any particular time, the amount of DC current (Direct Current) required by the card may vary. For example, if a simple-state machine is all that is required for access control, the read-only mode of the operation, the card can consume only on the order of 300 μA to 3 V. If a transaction is initiated further If a complex, such as an electronic bag debt for a vending machine or a collective conductor signal, it may be necessary to activate a microprocessor or microcontroller, and the current consumed may rise to 1 mA or more, depending on the complexity and speed of the processor. Such a transaction would also require, at some time, write or erase a memory, and in this way, an additional 500 - 800 μA of current could be consumed. If a very secure mode is required, such as a high-value transaction or access to a high-security building or room, an encryption or authentication algorithm is commonly employed. Such functions are computationally intensive and complete them in a timely manner, generally requiring auxiliary processing power. These auxiliary computational modes could increase the current consumption in the card by 5 mA or more, depending on the clock speed and complexity of the implementation. For a given card - reader separation, the current flow in the reader antenna must be above a certain level to provide enough power to the card so that, after rectifying the coupled power, the requirements are maintained DC power consumption of the card. A competitive advantage that is enjoyed by cards that can operate at greater distances from the reader. Reader manufacturers generally operate the antenna with more current than allowed by the regulations of local radiated conditions. Larger reader streams also mean far, unintentionally radiated, higher fields, which could interfere with other frequency bands in the vicinity. This is one of the reasons why the worldwide Industrial, Scientific and Medical (ISM) band of 13.56 MHz is considered by contactless card standards bodies, for example, ISO-14443. This particular region of the spectrum, allows higher radiated emissions for narrowband, high power applications, as described with reference to FIGURE 1. FIGURE 1 shows a spectral diagram 100 that includes a spectral mask 102, which describes the FCC regulatory emission limits for the ISM band. That is, the actual energy-frequency response curve 104, which represents the energy levels emitted from the terminal, can not exceed the limits shown in mask 102 at the frequencies shown. For example, under part FCC 15, a radiated E field strength of 10,000 μV / m measured at 30 m, is the maximum power level 110 allowed within ± 7 kHz of 13.56 MHz. Similarly, outside this band narrow, the radiated E field must fall below the general limit 108 of 30 μV / m measured at 30 m. To communicate with the card, the reader must impose a modulation on the current of the antenna. This modulation must be easily detectable on the card, so that it can be easily demodulated with a low complexity card receiver, low cost and low power consumption. The value of the modulation index agreed by ISO-14443 is ± 10% nominal around the value of the average carrier for logical 1 or 0. For random data, this level of modulation for reasonable data rates (105.9375 kbps in ISO-14443), will result in sidebands that are below a peak of approximately 25 dBc, 30 dBc in average in the bandwidth of 9 kHz measurement of the International Special Committee on Radio Interference (ie, CISPR-16). These spectral sidebands will fall out of the ISM window of ± 7 kHz, so the largest ones can be 30 μV / m to 30 m under the FCC 15 part. This means that for very large the modulated carrier could be 25 dB higher , or will be allowed 533 μV / m, or even up to 10,000 μV / m for the unmodulated carrier. For a microprocessor card of the state of the art (1 mA to 3.3 Vdc), the amount of the reading interval (that is, maximum separation between the terminal and the portable data device) achievable with these levels of radiated emissions is only order of 10 - 12 cm. Any higher current modes required by more sophisticated transactions would reduce this reading range only. Accordingly, there is a need for a data transmission system that allows a level of activity-dependent energy to be present in the portable data device. Such a data transmission system that could dynamically provide such an increase in energy without exceeding the regulatory limits would be an improvement over the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 shows a spectral diagram of an energy and data signal, according to what has been implemented in the devices of the prior art; FIGURE 2 shows a flow chart describing the operation of a terminal device, according to the present invention; FIGURE 3 shows a flow chart describing the operation of a portable data device, in accordance with the present invention; and FIGURE 4 shows a spectral diagram of a power signal, according to a preferred embodiment of the present invention.

Description of a Preferred Modality The present invention encompasses a data transmission system that includes a data transmission terminal and a portable data device. According to the invention, the terminal device is capable of transmitting to the card either in a first mode of operation or in a second mode of operation. In the first mode, an energy signal and a data signal are transmitted to the card, where the energy is extracted from the power signal to power the circuitry of the card, which in turn processes the extracted data bits of the modulated data signal. In the second mode of operation, a power signal is transmitted together with a modified data signal, or in a preferred embodiment, no data signal. The terminal device determines the level of the power signal in response to the requirement of the portable data device, and switches between the first and second modes of operation in response to this. FIGURE 2 shows a flow chart describing the operation of a terminal device, according to the present invention. In a first mode of operation, an energy signal (201) is transmitted in combination with a modulated data signal in a predetermined form, as described below. It should be noted that, in this mode of operation, the modulated data and energy signal would appear mainly as shown in the spectral diagram of FIGURE 1. As is known, the portable data device processes the data signal that is being processed. received using the energy extracted from the energy signal transmitted by the terminal device. The terminal and the card continue to operate in this manner while determining (203), if a change of power is required on the card, indicating a need to change the modes of operation. If mode change is not required, the operation continues as before. However, if the power requirements for the portable data device change (e.g., as a result of intensive power application), the terminal device increases the energy signal while reducing the data modulation (205), as described in more detail later. Numerous indices and modulation formats are possible for the first link mode from the reader to the card, and the choice of modulation would depend on the desired transaction time interval (data rate), the complexity of the desired card receiver (cost, energy consumption), and the desired reading interval (allowed carrier level while satisfying, the general limit of radiated emissions with sidebands). For example, a very low data rate system (a few hundred bits / seconds to a few thousand bits / seconds with the appropriate impulse formation) could adjust the modulation sidebands within the ISM spectral mask ± 7 kHz, allowing very high signal strength and long-range operation. However, for more complex transactions, such low data rates would result in very long transaction times, which may exceed 10 seconds. For fast, desirable transactions for vending machines, access to buildings, or transit, bit rates of the order of 100 kbps are required. For a card capable of complex transactions, such as secure access and multi-purpose ATM, a processor is required, and the level of power needed to support a processing requires a low modulation level, in conjunction with a high data rate to achieve reasonable card ranges. For ISO-14443, a modulation index of 10 ± has been agreed upon 2% for ASK modulation for simple detection. It should be noted here that low-deflection FSK or low-index PSK would also provide low sidebands, but at the cost of a more complex card receiver (not a simple surround detector). A less complex transaction, such as access to a building, requires less current consumption in the card, and can therefore be supported by a system that radiates less energy and that simultaneously provides larger sidebands, such as the 100% ASK modulation agreed by the second derivation of ISO-14443. This modulation allows a receiver. simpler on the card, but an energy signal that must be reduced, due to its larger lateral bands, approximately 10 dB with respect to the 10% ASK modulation system. For cards that consume equal power, 10% modulation allows a reading interval approximately twice as great as 100% modulation, due to the higher level of the sideband and, consequently, the lower level of the carrier allowed for the 100% modulation. For a card capable of performing complex functions, different levels of CD current are required, as has already been discussed. In order for the card to maintain the same interval under these different modes, it will require a higher reader antenna current. These would correspond to the second operating modes, such as the writing / erasing of the EEPROM or the accelerator or coprocessor of the physical authentication components. This can be done in at least two ways. First, the reader, knowing what type of transaction is being made, rsabe when the card has to write data in memory or start its accelerator of the physical components of authentication, and the reader can set their energy in a predetermined amount and during a predetermined duration, when it reaches the appropriate point in the transaction. Alternatively, the card, with a processor, determines that it will need more power for its next mode of operation, and requests an increase of energy of a certain level during a certain time interval of the reader, so that the following can be initiated mode. The terminal maintains the second mode of operation (207) until the second mode ends. The conclusion of this second mode can be determined in at least two ways. First, the terminal, with the knowledge of the transaction, knows the predetermined duration of the need to increase the power, or second, the card notifies the terminal of the conclusion of the second mode of operation. If the transaction is not complete (209), the terminal continues to check the mode change requirements (203). During the higher current operating modes, so that the same spectral mask is satisfied, either or both of the following must occur. First, the data rate must be reduced or increased significantly, or second, the modulation index must be reduced, or some combination of both. The fact that altering the data rate satisfies the requirements, can be shown by means of simple numerical integrations using any of several mathematical packages, and integrating over a 9 kHz bandwidth of the CISPR-16 centered in a deviation of 7 kHz . For example, assume a data rate of the first mode of 105.9375 kbps, and that the sideband spectrum obeys the following distribution: where A is the level of the absolute relation, Rb is the bit rate, Tb is the reciprocal of the bit rate, and f is the carrier deviation frequency. Decreasing the data rate increases Tb, which causes the components of the low frequency relationship to increase, but also narrows the main lobe, so that the lowest total energy falls within the measuring filter centered at a deviation of 7. kHz Alternatively, if the data rate increases above 105.9375 kbps, Tb becomes smaller, and consequently the sin (x) / x is now approximately equal to 1 over the bandwidth of the measurement filter for velocity of very high data, the integrated energy again does not decrease. If the second mode requires an increase in the carrier's power of 5 dB, so that the absolute modulation level "A" is also increased by 5 dB, the data rate should be reduced to < 1.6 kbps, so that the main lobe of the spectrum narrows enough to satisfy the spectral mask of ± 7 kHz. For the increase of the data rate, the data rate would need to increase above about 340 kbps. Any data rate would reduce the integrated off-band energy by 5 dB, and would comply with the regulations. By reducing the modulation index, it would also reduce the integrated energy level. For example, if the carrier is increased by 5 dB, and the absolute modulation level "A" remains the same (so that the modulation index is reduced), the levels of the sideband remain the same. For example, if the second mode requires a carrier power increase of 5 dB, the modulation index would fall from about 10% to about 5%. For some applications, it is not necessary to exchange data during higher current modes. In the preferred embodiment, there is no modulation during the writing / erasing of the EEPROM or while the accelerator or mathematical coprocessor of the physical computing components is working, since nothing else can be communicated, until the portable data device has completed an operation, and waiting for the execution of the following steps in the data exchange protocol. In this context, modulation can not be considered a special case of a lower data rate or a lower modulation index. A typical transaction would proceed as follows: The card enters the field of the reader, which is transmitting requests in the format of the first mode of modulation and power level. The card is activated when it is close enough, initially using the first modulation mode and power level. At this time, the card can communicate its power request request back to the reader. Eventually, the card needs to change the modes, perhaps from an EEPROM reading or a reader authentication. At this time, the card could notify the reader that it is ready for an energy step of a certain size and a certain duration. The reader recognizes this request and increases the power. However, since there is little or no communication required during this second mode, the reader deactivates all modulation or modifies the bit rate and the modulation index to reduce out-of-band emissions, so that an increase in the energy level of the carrier, and transmits to the higher energy level during the required period of time. Once this time has elapsed, the reader reduces the energy level back to the level of the first mode, and resumes communication with the card. In the above manner, the terminal is capable of distributing the energy required by the card without emitting levels that exceed the FCC spectral mask (102 shown in FIGURE 1). FIGURE 3 shows a flow chart describing the operation of the portable data device, according to the present invention. After entering the excitation field of the terminal device, the simple application portable data device determines (302), its power requirements for an ascending transaction sequence. A multi-application portable data device also determines the energy required for the upstream transaction sequence corresponding to the application supported by the terminal device. That is, depending on the application in which the terminal device is working, the card is able to determine its own power requirements. It should be noted that the present invention also has a capacity, on the card, to determine '-i. the desired energy levels and the operating energy levels present, as observed by the regulator / rectifier circuit. As with the terminal device, this mode continues until the requirement for an energy change is detected (304). After detection of the power change requirement, the portable data device transmits (306) back to the terminal device its new power requirements for the pending application. According to the invention, the card determines which energy request to send back to the reader through different means. First, observing the state of your regulator, the card could calculate that it needs less energy than what is being provided and, based on a design analysis, ask the reader to decrease their energy by a suggested amount. Second, the card, knowing that it will connect to a high current consuming function, such as a mathematical coprocessor, notifies the reader that there is not enough energy to connect to this function and, based on a design analysis, can request that increase the energy a suggested amount. The reader increases the energy at the requested level by modifying, at the same time, the modulation and / or data rate to reduce the spectrum according to what was described during the operation in the second mode. In addition, when the transaction follows a fixed standard pattern each time it is started, the card can communicate power requirements, either as a function of the task or as a function of time, to the terminal device for subsequent sequential execution. The terminal device stops this information from the energy profile and, when a first mode is completed, it moves to a second mode for a specific time. After completing the second mode, the terminal device adjusts its power level, modulation index and / or data rate to operate in the next requested mode, until the power-time sequence is completed. It is allowed to depart from this original power-time profile, if the execution of the protocol requires the repetition of a task or tasks that require power. A power-time profile could also be stored inside the card, and be communicated to the reader at the beginning of the transaction. This power-time profile could also be known a priori both by the reader and by the card. In this case, the specific details of the power-time profile do not need to be communicated directly during the transaction; A power-time profile can be defined by a unique identifier that is communicated to the reader. Referring again to FIGURE 3, the card continues to determine (302) its energy requirements, until the transaction ends (308). FIGURE 4 shows a spectral diagram 400 that increases the energy signal transmitted from the terminal (ie, the second mode of operation), according to the invention. As shown, the maximum energy level 401 exceeds the maximum energy level generated in the first mode of operation (ie energy level 106) by an amount 403, although it still meets the FCC limit, as indicated by the spectral mask 102. Also, without data modulation (or with a substantially zero modulation), the sideband energy curve 405 is well below the spectral mask 102. In this way, the present invention allows the card receives greater energy from the terminal without exceeding the regulatory emission limits. The invention described above allows cards with multiple modes or functions to complete a complex transaction at the maximum interval capacity of the reader (terminal), still satisfying the spectral regulations of the radiated emissions. Unlike previous implementations of this type of product, it changes the level of energy needed for more complex and more powerful functions, but also adjusts the data rate and / or modulation index for different energy levels, to maintain a satisfactory sideband level. In addition, the card constantly observes its regulator to determine if a power change of the reader is necessary.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (10)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. In a terminal device, a method for feeding a portable data device, characterized in that it comprises the steps of: transmitting to the portable data device, in a first mode of operation, a power signal to a first level and a data signal using a first modulation format and a first bit rate; transmitting to the portable data device, a second mode of operation, a power signal to a second level and a data signal using a second modulation format and a second bit rate; determine a requirement to change the modes of operation; and changing, in response to the determination step, between the first mode of operation and the second mode of operation.

The method according to claim 1, characterized in that the determination step comprises the steps of receiving, from the portable data device, a request to change the operating modes.

The method according to claim 1, characterized in that the determination step comprises the steps of: recovering a stored power-time profile; and interpreting the power-time profile to determine if a mode change is currently required. .

The method according to claim 1, characterized in that the first modulation format comprises the ASK modulation which uses a modulation index in the range of 8% -12%.

5. The method according to claim 1, characterized in that the first modulation format comprises the ASK modulation that uses a modulation index of 100%.

6. In a portable device that is in communication with a terminal device, a method for performing one of a plurality of tasks that require power, characterized in that it comprises the steps of: determining an energy requirement for a first of the plurality of tasks that they require power; and transmitting to the terminal device, in response to the determination step, a request for power requirement.

7. The method according to claim 6, characterized in that the determination step comprises the step of identifying a power-time profile, which characterizes the energy requirement to perform the plurality of tasks that require power. The method according to claim 6, characterized in that the transmission step comprises the step of indicating to the terminal device to distribute an energy signal corresponding to the power requirement. The method according to claim 6, characterized in that the determination step comprises the step of calculating a value of relative difference between the current energy level on the portable data device and the desired energy level. The method according to claim 9, characterized in that the transmission step comprises the step of sending the value of the difference relative to the terminal device.