UA54446C2 - Method for transmission of data between a terminal and a portable data carrier - Google Patents

Abstract

A method for the transmission of data between a terminal and a portable data carrier via a wireless electromagnetic transmission link wherein a carrier signal modulated by 100 % ASK data acts as a timing signal in the data carrier and the significance of data is determined by the shifting position in the carrier signal within a time slot and the information content of a shifting position corresponds to a number of N bits, whereby N is larger than or equal to 2. The significance of these N bits is defined by the shifting position within 2N possible positions in a time slot. At the beginning or the end of a time slot there is a zero-time interval, in which there is no occurrence of a shirting point allocated to the data to be transmitted in order to avoid unacceptably long malfunctioning of the carrier signal.

Description

Description of the invention

The use of data transmission methods is spreading, in which the exchange of information between portable data carriers 2 and the terminal is carried out in a non-contact manner, that is, by means of inductive or capacitive communication, that is, in general, by means of a wireless electromagnetic transmission line. At the same time, the portable data carrier usually receives energy from the terminal also in a non-contact way, for which a high-frequency signal of the carrier frequency is used, for; which, in addition, on the one hand, the modulated data is used, and which, in turn, is used directly as a clock signal in the data carrier. 70 For data transmission, the carrier frequency signal in most application options is only switched on and off, that is, one hundred percent amplitude manipulation is carried out (AZK, Atriyide-ZNPIY-Keuipoa). In this case, the carrier frequency signal is usually extinguished or switched off or remains unchanged for the transmission of a logical one ("1") or a logical zero ("0") during not the entire allocated time segment, hereinafter the "time interval", the duration of which is determined by the "electrical" transit time bit, and within a much shorter 12 time. The interval during which the signal is turned off (blank interval)" is, for example, one-fourth or one-third of the time interval equal to the bit transit time, or time interval. Consequently, the carrier signal exists during the interval between the two states causing signal blanking, long enough to provide power and clock frequency.

Coding is possible using the Miller code. For this, a logical one T is transmitted using a blanking interval in the middle of the time interval, and a logical zero "0" is transmitted using a blanking interval at the beginning of the time interval, and the logical zero "0" transmitted after the logical one "1" is represented by the absence of a blanking interval during the time interval to prevent too short gaps between blanking intervals.

Fig.bA shows the signal in the Miller code, with the help of which the carrier frequency signal should be amplitude modulated. It represents the sequence 101000110. The vertical dashed lines indicate time intervals. The blanking interval is approximately one fourth of the time interval. Fig. 6B shows the corresponding frequency spectrum determined by computer, and the signal from Fig. bA is modulated with a frequency of 100 MHz for the carrier frequency signal. As can be seen, the contour of the sidebands has the form (ziph/x), and the distance between the maximum peaks of the sidebands and the peak of the carrier frequency can be ee, equal to approximately 18.2dB. "Her

For the worst case, that is, modulation with a sequence of units 111111111, shown in Fig. 7A, the frequency spectrum has the form according to Fig. 7B. In this case, the distance between the peaks of the side frequency bands and the peak of the carrier frequency reaches only 10.5 dB. "AND

According to the requirements for the range of permitted frequencies, as well as the standard of the Temporary Working Group 3о (МККР) ET 300330 (ЕТ5И, September 1994), the carrier frequency is the frequency used for o industrial, scientific and medical equipment (which creates interference), for example, 13.56MHz, with a cut-off level of 42dBμA/m (F 10m. The width of the carrier frequency range is only /- 7kHz, so that the modulation spectrum for the chosen type of modulation and Miller code bit-coding remains completely outside this range. In the mentioned standard, the level in the range beyond these limits is limited to a value of 20dBμA/m (Ф 10m, З i.e. 22dB lower than the carrier frequency, and the frequency range of measurements is 1О0kHz. The system described with the application of one hundred percent amplitude manipulation according to the Miller code, as indicated above, turns out

iz" beyond these limits, and permission to operate this system can be granted only if one hundred percent modulation is not carried out and an average value is determined that allows today's

Germany has requirements, but it is inadmissible according to ET5 300 330 and FCC regulations, which 49 require quasi-peak evaluation. and-th From Helmut Lemme's article "The speed of data transmission in the infrared frequency range increases", "Electronics", Z3/1996, P.38...44, it is known the use of phase-pulse modulation for transmission in the infrared frequency range with the aim of acceleration of data transmission, but at the same time, two bits are subordinated to each pulse of shk. However, in this case, phase-pulse modulation is used in order to achieve a higher data transfer rate without changing the peaks of the sidebands of the frequency spectrum with the same number of pulses transmitted per unit time, but this does not matter in this case . However, since it is desirable to achieve the maximum possible pulse repetition rate, there are no gaps between pulses in this case, so that for bit sequences 11 and 00, the carrier frequency signal is turned off for a time corresponding to the duration of two pulses. This is not an additional disadvantage in the case of transmission in the infrared range, since in this case a generator for generating clock pulses is always provided in the receiving device 25.

GF) However, in the methods based on the invention, in which the carrier frequency signal is used directly as a clock frequency signal, this would lead to an unacceptably long dropout of the clock signal.

Therefore, the invention was based on the task of developing a method for transmitting data between a terminal and a portable data carrier 60 using a wireless electromagnetic transmission line, in which, at approximately the same data transfer rate in bits, a greater distance between the peaks of the sidebands and the peak of the carrier would be provided frequency without unacceptably long disconnection of the carrier frequency signal, which is used as a clock signal.

This task is solved using the method according to paragraphs 1 and 2 of the claims. The preferred options for the development of the invention are given in the dependent clauses of the claims.

In the transmission method according to the invention, at least two, preferably three transmitted bits are accounted for in the carrier frequency signal for one interval in which the signal amplitude changes. In this interval, the amplitude of the carrier frequency signal changes (amplitude change interval). In the case of one hundred percent amplitude manipulation, the signal would be turned off (quenched), so that a blanking interval would be formed. The significance of these bits is determined by the position of the amplitude change interval within a time interval of a certain length or duration. Thus, with M bits per interval of amplitude change, it should be possible to detect 2 M possible positions for one interval of amplitude change within one time interval, that is, in the case of transmission of three bits per one interval of amplitude change, the number of such possible positions 70 is eight. Although this requires an increase in the cost of detecting the amplitude change intervals in the receiving device, at a constant transmission rate, fewer amplitude change intervals per unit time are required, so that a lower pulse repetition rate is provided, and at the same time, smaller sideband peaks of the modulated signal in this way carrier frequency. Depending on the selected number of bits per interval of the amplitude change, it is even possible to simultaneously increase the bit rate and reduce the peaks of the 75 sidebands.

If the data rate in bits must remain constant, for example, because the requirements of a given transmission protocol must be met, a solution is preferable, in which the duration of the time segment according to the invention, further - the zero time segment, within the time interval that does not fall no amplitude change interval subordinate to the data to be transmitted is equal to or a multiple of the duration of a possible amplitude change interval position. Thanks to this, the process of detecting intervals of amplitude change is significantly simplified compared to the case when the duration of the zero time segment is arbitrary.

Next, the invention is explained in more detail on the example of implementation with the help of drawings. They show: figA and 18 - a schematic representation of the time characteristics of the parameters for the method according to the invention, as well as the corresponding signal of the carrier frequency after one hundred percent amplitude manipulation Ha fig.2 - different possibilities of forming a time interval. Fig. 3 is a scheme of the method according to the invention without a zero period of time; i9)

Fig. AA and 48 - the time characteristic of the carrier frequency signal, modulated according to the invention using the bit sequence 001000110, and the corresponding frequency spectrum.

Fig. 5A and 5B are time characteristics of the carrier frequency signal modulated according to the invention by means of the bit sequence 000000000, and the corresponding frequency spectrum.

Fig.bA and 6B - the time characteristic of the carrier frequency signal encoded using the Miller code, with the M bit sequence 102000110, and the corresponding frequency spectrum, as well as "I

Fig. 7A and 7B - the time characteristic of the carrier frequency signal encoded using the Miller code, with the bit sequence 111111111, and the corresponding frequency spectrum. in

Fig. 18 shows a carrier frequency signal with one hundred percent amplitude manipulation, which corresponds to the invention, which transmits the bit sequence 100111000 during the depicted time segment. For this, in the given example, only three intervals of amplitude change are needed, that is, time segments in which there is no carrier signal frequency, since three bits are transmitted for one amplitude change interval. The significance of these three bits is determined by the position of the amplitude change interval in the time interval. A relevant example is shown in Fig. 1A. - s The time interval begins with a zero time segment corresponding to the invention, which does not include any amplitude change interval subject to the data to be transmitted. The possibility of "» location of the amplitude change interval on the segment of the remaining time interval is provided. For the chosen example, that is, three bits per one amplitude change interval, there are 23 - 8 possible combinations of three bits, so

What should be expected is the eight possible positions of the amplitude change interval. In figLA, these possible axis positions are subordinated to the significance of the bits in the increasing sequence. However, any other option of subordination is possible. Thus, for example, subordinations in which the possible position e of the interval of amplitude change differs from the adjacent one by only 1 bit, because in this case the time shift "" of the signal probably results in a change of only one bit, and this can be easily recognized by using the parity test. An example of such subordination is, for example, | 000 | 001 | 011 | 010 1110 1111 1101 | 100 |. e The positions of the amplitude change intervals in the time intervals shown for the bit sequence 100111000, which

The FO is subject to transfer, indicated by a thick contour line.

As can be seen in Fig. 1A and 18, for the sequence of the last possible positions in the time interval, in the given example for the bit sequence - 111, and the first possible position in the time interval, in the given example - 000, in the absence of a zero time segment according to with the invention, two amplitude change intervals are arranged in series. In the method, which is the basis of the invention, in which the carrier frequency signal, o is used directly as a clock signal, this would lead to an unacceptably long clock drop. Therefore, according to the invention, a zero period of time is provided.

However, if the first and last possible positions of the amplitude change interval are not located consecutively, because one after the other, it is generally possible to predict the amplitude change interval subject to the command signal in the zero time period. However, such command signals can only be located between "valid" data combinations if it is ensured that the carrier frequency signal exists long enough during the time between all amplitude change intervals.

Figure 2 shows preferred variants of the time interval structure. The top diagram shows a temporal 65 sequence of "electrical" bits represented by logical zeros ("0"). However, other presentation options are also possible. The transmission rate in bits in this transmission method should not increase, so that when transmitting three bits per interval of amplitude change, the time interval has a duration equal to the duration of three "electrical" bits.

In the case of transmission of three bits per interval of amplitude change in one time interval, eight possible positions are assumed, as well as a zero time interval. To simplify the interval detection scheme in the receiving device, the preferred option is when the duration of the zero time segment is equal to or is a multiple of the duration of the possible position.

It should be noted here that the length of the amplitude change interval does not necessarily have to be equal to the length of the possible position, but can generally be smaller. This interval should only be within a possible position of 7/0 to ensure that the significance of the bits can be determined unambiguously.

The middle part of Fig. 2 shows an example when the duration of a zero time segment is equal to the duration of a possible position. In the lower part of Fig. 2, an example is given, when the length of the zero time segment is four times greater than the length of the possible position, and thus corresponds to the duration of the "electrical" bit. These cases are particularly easy to detect.

In the given examples, the zero time segments are always located after the time interval. However, they can be predicted or located at the end of the time interval.

Another solution to prevent an unacceptably long dropout of the clock frequency signal corresponding to the invention is shown in Fig.3. A zero time segment is not provided here, however, in order to prevent an unacceptably long dropout of the clock frequency signal when the last and the first possible position of the amplitude change interval in the time interval are sequentially located, in this case, instead of the amplitude change interval in the first possible position, the amplitude change interval in the time interval is not transmitted . But for this, it is necessary to ensure the temporary storage of the corresponding position of the amplitude change interval during the next time interval, in order to be able to determine whether, in the absence of an amplitude change interval in the time interval, the amplitude change interval occupied the last possible position in the previous time interval, or place an error during transmission. In any case, there may be no need to use scheme o to determine the zero time segment

Figures 4A and 4B, as well as 5A and 5B, show calculated frequency spectra for certain given bit sequences to be transmitted using a method according to the invention. You should choose a method with the transmission of three bits per interval of amplitude change and the duration of the zero time segment, which is equal to the duration of four possible positions, as shown in the lower part of Fig. 2.

Thus, the duration of the time interval is equal to ZOms, and the possible position is 2.5ms, and the same duration of the amplitude change interval is chosen. In Fig. 4A, the bit sequence 001000110 is selected, and in Fig. 5A, the bit sequence 000000000 is selected, which represents the worst case in terms of the frequency spectrum.

As can be seen from the frequency spectra, with an almost arbitrary bit sequence according to Fig. 4A, the specified distance "interval between the sidebands and the carrier frequency signal is approximately 21.8dB. Even in the worst-case scenario shown in Fig. 5B, the distance is still 20.9dB, so that the above-mentioned frequency requirements are met much better than the state of the art requires.

The specificity of today's methods of data transmission between a terminal and a portable data carrier using a wireless electromagnetic transmission line requires the use of one hundred percent amplitude manipulation, so that the application of the method according to the invention can guarantee special advantages. However, it is still possible that in 7-3) the specific requirements will change in the future, and a lower modulation depth will be acceptable. So, in this case, not a simple process of turning on/off the signal will be carried out, but switching between ;" two levels. This can lead to a further reduction in the width of the sidebands. The application of the method protocol according to the invention guarantees the advantage that, both according to today's specific requirements, and with future changes regarding the modulation depth, it will be possible to work with without changes. sh»

Claims (1)

The formula of the invention , , , , , , . ve 1. The method of data transmission between a terminal and a portable data carrier using a wireless Ф electromagnetic data transmission line, and the carrier frequency signal, the amplitude manipulation of which is carried out with the help of data, is used in the data carrier as a clock signal, and the significance of the data is determined by the position of the amplitude change interval in the carrier frequency signal within the time interval, which differs in that the information content in the amplitude change interval corresponds to the information content in M bits, with M greater than or equal to 2, and the significance of these M bits is determined by the position of the change interval (F, amplitudes within 2" of possible positions in the time interval, and that at the beginning or at the end of the time interval ka place a zero segment of time, in which there is no interval of amplitude change, subject to the data to be transmitted. 60 2. The method of data transmission between a terminal and a portable data carrier using a wireless electromagnetic data transmission line, and the carrier frequency signal, the amplitude manipulation of which is carried out with the help of data, is used in the data carrier as a clock signal, and the significance of the data is determined by the position of the amplitude change interval in carrier frequency signal within the time interval, and in the presence of data, the significance of which is usually determined by the first possible position in the time interval, b5 After the appearance of data, the significance of which is determined by the last possible position in the time interval, the significance of the data, which is usually determined by the first possible position, in this case is determined by that the interval of amplitude change does not appear in any possible position in the time interval, which differs in that the interval of amplitude change corresponds to M bits, and M is greater than or equal to 2, and the significance of these M bits is determined by the position of the interval of amplitude change within 2" possible positions in the time interval. C. The method according to claim 1, which differs in that the duration of the time interval is equal to M bits. 4. The method according to any one of claims 1-3, which differs in that one hundred percent amplitude manipulation is used. c schi 6) (Se) « « « IS c) - with . and? 1 sh» sh» sh» 4) name) 60 b5