JP3509493B2 - Data communication system, wireless IC card and wireless IC card system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital data communication system, a wireless IC card, and a wireless IC card system using the wireless IC card. [0002] In a card system such as a commuter pass, a contact / contact type system such as a magnetic card is used.
There is a need for a system that operates wirelessly without contact. That is, the power required for the operation is wirelessly supplied to the card, and the electronic circuit on the card communicates with the controller body. In the above system, the controller modulates a high-frequency signal with information to be transmitted, and transmits the modulated signal to the air via an antenna. The transmitted energy is captured by an antenna on the card side, and the information is reproduced by a demodulation circuit on the card. This high frequency signal is called a carrier. Conventionally, as a modulation / demodulation method, amplitude modulation ASK (A) for changing the amplitude of a carrier wave according to digital information
FSK (Frequency) which changes the frequency of the carrier wave and the amplitude of the key.
Shift Keying) and PSK (Phase Shift Keying) that changes the phase of a carrier wave are typical. Generally, PSK is excellent in that the signal error rate is low and the occupied frequency bandwidth is narrow, and it is adopted in many modulation / demodulation methods of digital data transmission. PS
When demodulation is performed using K, a delay detection method using a delay line and a detection method in which a synchronous clock is generated by phase-locked detection (PLL) are known. SUMMARY OF THE INVENTION An object of the present invention is to provide a high-performance system with a minimum hardware configuration without using a delay line required for demodulating PSK and a PLL which causes an increase in power consumption. Data communication system and radio I for performing quality data communication
It is to provide a C card system. SUMMARY OF THE INVENTION The present invention provides a system for wirelessly performing power transmission using a signal at a frequency fp and digital data communication using a carrier at a frequency fs.
= Fp / N (N is an integer), and the amount of phase displacement during PSK modulation is (M × 360 °) / N (M and N are integers and P is not equal to 180 °). Further, the present invention is a wireless IC card system using the data communication system. Further, the present invention includes a wireless IC card and a base station for at least supplying power and transmitting data to the wireless IC card, and the wireless IC card transmits the wireless IC card from the base station using a frequency dividing circuit. The demodulated data is demodulated. Further, the present invention includes a frequency dividing circuit as a data demodulating circuit. An embodiment of a data communication system according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the power transmitted wirelessly from a reader / writer 1 provided at a ticket gate or a bus of a station according to the present invention to an IC card 2 passed or approached in a non-contact manner. 1 is a diagram showing a schematic configuration of a system that operates an electronic circuit on an IC card 2 to transmit and receive information such as a ticket and a commuter pass to and from a reader / writer 1 to serve as a ticket and a commuter pass. . FIG. 2 is a diagram showing an embodiment of data communication according to the present invention. The reader / writer 10 includes an oscillator 11 that oscillates a frequency for transmitting power, a 分 frequency divider 14 that generates a carrier wave for data communication, and a matching circuit that performs impedance matching with the antenna coil 13 to transmit power efficiently. 12, CPU 1 for controlling the whole system, memory 2 for storing data, modulator 15 for modulating communication data, power amplifier 16, antenna coil 9
A matching circuit 19 for impedance matching with the amplifier, an amplifier 18 for amplifying a signal received by the antenna coil, and a demodulation circuit 17. The wireless card 20 that receives and operates power and data information from the reader / writer 1 includes an antenna coil 21 that receives power, a matching circuit 22 that efficiently extracts power, and a rectifier circuit 2 that extracts a DC power supply voltage.
3. an antenna coil 25 for exchanging signals for data communication;
A matching circuit 26 for performing impedance matching; an amplifier 27 for amplifying a received signal; a demodulator 28; a CPU 3 for controlling data and communication on a card; a memory 4;
0, consisting of a power amplifier 29. Power transmission uses industrial, scientific and medical (ISM) radio frequency bands to deliver high power. In the example of FIG. 2, 13.56 MHz is used. The communication frequency can be arbitrarily set as long as it is the minimum power not exceeding the reference value of the electric field intensity defined by law. In the present embodiment, the carrier frequency of the communication is set to an integral fraction (in the example, 1/4) of the power transmission frequency. Wireless card 2
In the demodulation circuit 28 at 0, a signal for power transmission is extracted from the antenna coil 21, a carrier frequency fc divided by the 1/4 frequency divider 14 is generated, and data is demodulated by synchronous detection. Details of the demodulation circuit 28 will be described with reference to FIG. The demodulation circuit 28 includes carrier frequency signals 51, 52, and 5 obtained by dividing the power transmission signal 50 by 4 by the frequency divider 24.
Four synchronous detectors 41 synchronously detected by 3, 54,
42, 43, 44 and low-pass filters 45, 46, 47, 4
8, the demodulated signal 55 at the carrier frequency fc,
56, 57, and 58 are generated, and the CPU 3 performs the processing. At this time, the modulated wave from the reader / writer 1 is P
360 ° / N = 90 ° (N = 4) with SK modulation
Thus, by selecting any one of the demodulated signals 55, 56, 57, and 58, a demodulated signal that is correctly synchronously detected can be obtained. That is, in a system in which power transmission using a signal of the frequency fp and digital data communication using a carrier wave of the frequency fs are performed wirelessly, the relationship fs = fp / N (N is an integer) is satisfied. Is (M × 360 °) / N (M and N are integers and P is 180 °
Is not equal to). FIG. 4 is an operation flowchart of the system shown in FIG. First, the reader / writer 10 transmits a data signal using the antenna coil 9 (step 1). For example, the signal Fs shown in FIG. 5 is transmitted. This signal Fs is generated based on the signal Fc from the transmitter 11. The card 20 receives the above data signal using the antenna coil 25 (step 2). At this time, a PSK-modulated signal is used as a data signal to be transmitted. Next, the received data signal is supplied to the demodulator 2
8 demodulated. The detailed operation will be described with reference to FIG. The synchronous detectors 41 to 44 shown in FIG. 3 have a function of detecting a data signal having a predetermined phase as described above. Then, the synchronous detectors 41 to 44
Is set to a value obtained by dividing the transmission frequency from the transmitter 11 of the reader / writer. For example, the characteristic shown in FIG. 6 is set in each of the synchronous detectors 41 to 44. In this case, a signal obtained by dividing the signal Fc from the transmitter 11 by a quarter is set. Accordingly, since the operating frequencies of the reader / writer 10 and the card 20 are both generated using the transmitter 11, the two are in a synchronized state. Note that the synchronous detectors 41 to 44 may be configured by an AND circuit or the like that inputs a signal obtained by dividing the frequency of the transmission from the transmitter 11 and a received data signal. Now, such synchronous detectors 41 to 44 will be described.
Receives the above-mentioned data signal, and a synchronous detector that synchronizes with the phase of the received data signal outputs a predetermined signal (step 3). On the other hand, since the data signal is a PSK-modulated signal, data signals having different phases are transmitted from the reader / writer 10. Therefore, the synchronous detectors 41 to 44
Detects the data signals having different phases by the same processing as described above. That is, as shown in FIG. 7, two types of phases of the data signal are detected (step 4). Next, the CPU 3 determines the relationship between the first detected synchronous detector and the second detected synchronous detector.
That is, the phase of the first detected data signal is compared with the phase of the next detected data signal (step 5), and "1" is assigned to any of the data signals (step 6). In this case, it is necessary to temporarily store the received signal in the memory 4 or the like in order to perform the above-described phase comparison and determination. In FIG. 4, "1" is assigned to a data signal whose phase is advanced by 90 degrees. By detecting the two types of phases in this manner, “1” in the data signal from the read / writer 10 is obtained.
Can be specified, and the data signal from the reader / writer 10 can be accurately transmitted to the card 20. As described above, if a synchronous detector to which "1" should be assigned can be detected, only the signal from the synchronous detector may be taken into the CPU 3. Alternatively, the CPU 3 may process only the signal from the synchronous detector. Further, in the BPSK method of transmitting a data signal by shifting the phase by 180 degrees, it is not possible to compare whether or not the phase has advanced. Therefore, in the case of the present invention, it is preferable to use the PSK method using other phases. FIG. 8 shows the above-described processing realized by hardware. In FIG. 8, data holding means 60 for holding the output signals of synchronous detectors 41 to 44, data holding means 60
And a selection unit 61 for selecting an output based on the result of the operation detection unit. For example, a shift register may be used as the data holding unit 60, and a switching circuit may be used as the selection unit 62, for example. First, the outputs of the synchronous detectors 41 to 44 are held by the data holding means 60. Next, the operation detecting means 61 detects the two types of operated synchronous detectors as described above, using the data held by the data holding means 60. Then, the phase of the received data signal is compared using the detection result. Then, the selector 62 is controlled so as to select the output of the synchronous detector to which "1" is to be assigned from the comparison result. For example, the selector 62 compares the signals from the synchronous detectors and selects the output from the synchronous detector whose phase is advanced.
Control. Until the output of the synchronous detector to which "1" is to be assigned is selected, the output from the synchronous detector is held by the data holding means 60. The controlled selecting means 62 selects the output of the synchronous detector to which "1" is to be assigned, and inputs the selected output to the CPU. Thus, the processing described in the above embodiment can be realized by hardware. Needless to say, hardware is more suitable for high-speed processing. According to the present invention, a clock recovery circuit such as a PLL circuit is not required by extracting a synchronous clock required for PSK demodulation from a power transmission system, and the data communication function can be performed with minimum hardware. The effect of realizing is achieved. Further, according to the present invention, a PLL which causes a delay line and an increase in power consumption conventionally required for demodulation of PSK.
It enables high-quality data communication with a minimum hardware configuration without the use of.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a schematic configuration of a wireless card system according to the present invention. FIG. 2 is a diagram showing an embodiment of data communication according to the present invention. FIG. 3 is a diagram showing details of a demodulation circuit in a data communication embodiment according to the present invention. FIG. 4 is a flowchart showing data demodulation processing according to the present invention. FIG. 5 is a diagram showing a data waveform according to the present invention. FIG. 6 is a diagram showing a data waveform according to the present invention. FIG. 7 is a diagram showing data demodulation according to the present invention. FIG. 8 is a hardware configuration diagram according to the present invention. [Description of References] 1 ... CPU, 2 ... Memory, 3 ... CPU, 4 ... Memory 4,
9: Antenna coil, 10: Reader / writer, 11: Oscillator that oscillates frequency for transmitting power, 12: Matching circuit,
13 antenna coil, 14 1/4 frequency divider, 15 modulator, 16 power amplifier, 17 demodulation circuit, 18 amplifier, 19 matching circuit, 20 wireless card, 21 antenna coil, 22 Matching circuit, 23 rectifier circuit, 25 antenna coil, 26 matching circuit, 27 amplifier, 28
Demodulator, 29 power amplifier, 30 modulators 30, 41,
42, 43, 44 ... synchronous detector, 45, 46, 47, 4
8: low-pass filter, 50: power transmission signal, 51, 52,
53, 54... Carrier frequency signals, 55, 56, 57, 5
8 Demodulated signal

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Nagai 2326 Imai, Ome-shi, Tokyo Inside the Device Development Center, Hitachi, Ltd. (56) References JP-A-6-96300 (JP, A) JP-A-1- 269344 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 27/18 H04B 5/00

Claims (1)

(57) [Claim 1] Power transmission using a signal of frequency fp and frequency
Digital data communication using a carrier wave of several fs wirelessly
A cormorants system, the frequency fp by dividing, by a phase displacement P of PSK modulation
Means for generating a plurality of different phase signals, and means for synchronous detection using the plurality of phase signals, wherein the frequency fp and the frequency fs are fs = fp / N (where N is
The phase displacement P is expressed as P = ( M × 360 °) / N (where M and N are integers).
One P is equal to or is not equal) to 180 °
system.