Communications: electrical – Selective – Interrogation response
Reexamination Certificate
2000-03-21
2004-06-08
Zimmerman, Brian (Department: 2635)
Communications: electrical
Selective
Interrogation response
C340S010100, C340S010340, C340S572100, C340S572600, C340S572700
Reexamination Certificate
active
06747548
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a non-contact IC card system including a non-contact IC card using electromagnetic induction but not having a battery, and to a non-contact IC card.
BACKGROUND ART
FIG. 36
illustrates a configuration of this type of conventional non-contact IC card system. In this illustration, numeral
80
designates a non-contact IC card (which will be referred to hereinafter as a card) not containing a battery, while numeral
70
denotes a reader writer (which will be referred to hereinafter as an R/W).
In the card
80
, numeral
81
represents an antenna resonance circuit constituting a parallel resonance circuit using an antenna coil
81
a
and a capacitor
81
b,
numeral
82
depicts a rectifying circuit comprising rectifying devices
82
a
and
82
b,
and numeral
83
signifies an energy storing circuit made up of energy storing capacitors
83
a
and
83
b
for storing energy after rectification.
FIG. 36
shows an example of full-wave voltage doubler rectifying circuits.
Numeral
84
designates a comparator for detecting the fact that a voltage after rectification exceeds a predetermined value, and numeral
84
a
signifies a reference power supply for producing the aforesaid predetermined value. In addition, numeral
85
depicts a variable resistive device comprising, for example, an MOSFET transistor and connected in parallel to the antenna resonance circuit
81
. This variable resistive device
85
, when the comparator
84
detects that the voltage after the rectification exceeds the predetermined value, alters a quality factor Q of the antenna resonance circuit
81
in proportion to the exceeding or extra quantity from the predetermined value.
Numerals
86
a
and
86
b
represent output transistors, respectively, numeral
87
designates a transistor drive circuit to be described later, numeral
88
denotes a driver taking an operating condition by a control signal
88
a
at transmission, and numeral
89
indicates a resistor connected to the output side of this driver.
Numeral
90
a
depicts a high-potential side level comparator for detecting the fact that the high-potential side amplitude level of the antenna resonance circuit
4
exceeds a predetermined value (for example, Vcc), numeral
90
b
denotes a low-potential side level comparator for detecting the fact that the low-potential side amplitude level of the antenna resonance circuit
81
falls below a predetermined value (for example, GND), numeral
90
c
signifies an intermediate level comparator for detecting whether the antenna resonance circuit
81
is above or below a predetermined value (for example, ½ Vcc), numeral
91
means a control section, and numeral
92
designates a memory section for data storage.
Meanwhile, in the R/W
70
, numeral
71
represents a transmission antenna resonance circuit comprising an antenna coil
71
a
and a capacitor
71
b
to constitute a series resonance circuit, numeral
72
denotes a power transmission adjusting resistor for adjusting the magnitude of the power transmission from the R/W
70
, numeral
73
depicts a driver, and numeral
74
indicates a modulating circuit comprising an EX-OR circuit, connected to the input side of this driver
73
and made to receive data
74
a
and a carrier
74
b.
Numeral
75
represents a reception antenna resonance circuit comprising an antenna coil
75
a
and a capacitor
75
b,
constituting a parallel resonance circuit, numeral
76
denotes an amplifying circuit for amplifying a signal received, and numeral
77
depicts a demodulating circuit.
Since the power supply varies depending upon the distance between R/W
70
and the card
80
, for absorbing this variation, on the card
80
side, the quality factor Q of the antenna resonance circuit
81
is altered on the basis of the voltage after the rectification, thereby stabilizing the voltage induced in the card
80
.
When the comparator
84
makes a decision that the voltage after the rectification exceeds the predetermined value, the variable resistive device
85
adjusts the quality factor Q of the antenna resonance circuit
81
so that the quality factor Q decreases correspondingly to the exceeding quantity from the predetermined value. Furthermore, the decrease of Q causes the adjustment of the reception voltage, which leads to the stabilization of the voltage, to be induced in the card
80
, against the variation of the distance between the R/W
70
and the card
80
.
In addition, a modulation system for data transmission from the card
80
to the R/W
70
also requires less consumption of energy. For this reason, a modulation is made by varying the constant of the antenna resonance circuit
81
. A phase modulation system is realized in a manner that the constant of the antenna resonance circuit
81
is changed correspondingly to the variation of data to be transmitted.
In the case of the phase modulation system, the transistor drive circuit
87
generates a 180° pulse lasting for a period of a phase of 180° when the output data varies. This 180° period is determined from the output of the intermediate level comparator
90
c.
Furthermore, in a manner that the output transistor
86
a
conducts ON/OFF operation in accordance with this 180° pulse, the connection/disconnection of the output capacitor
86
b
to/from the antenna resonance circuit
81
is accomplished so that the resonance frequency of the antenna resonance circuit
81
varies with the variation of data. The connection of the output capacitor
86
b
to the antenna resonance circuit
81
causes the variation of the circuit constant of the antenna resonance circuit
81
.
FIG. 37
is a waveform illustration for explaining the operation. In
FIG. 37
, (a) indicates data, (b) indicates a carrier, (c) shows a waveform after phase modulation, (d) shows a signal (180° pulse) to the base of the transistor
86
a
at the phase modulation, (e) illustrates a waveform after frequency modulation which will be described later, and (f) illustrates a signal to the base of the transistor
86
a
when the frequency modulation is conducted.
As shown in (a) to (d) of
FIG. 37
, when the variation of the output data takes place (variation from an H level to a L level and from the L level to the H level), the frequency is changed for a period of 180° and, assuming that this frequency is ½ of the original frequency, the two-phase modulation is realized.
That is, as shown in (c) of
FIG. 37
, the signal after the phase modulation turns in frequency to ½ for the period of 180° from the variation of data, that is, the period between A and B and the period between C and D, whereupon the phase inverts for the period between B and C.
In addition, taking the phase into consideration rather than the output of the intermediate level comparator
90
c,
if the output transistor
86
a
is turned ON/OFF in accordance with the variation itself of the output data from the control section
91
, as shown in (e) and (f) of
FIG. 37
, the frequency modulation is conducted such that the frequency becomes ½.
Still additionally, as another approach, there has been a system in which the output transistor
86
a
is connected between both the ends of the resonance circuit
81
and both the ends of the resonance circuit
81
is short-circuited at a varying point of the output data for the period of 180° to compulsively invert the phase for the PSK modulation, thereby accomplishing high-speed data transmission.
In the above-described conventional non-contact IC card system, the power transmission has been made from the R/W to the card, while the data transmission has been performed in a manner that its power carrier is PSK (Phase Shift Keying)-modulated in accordance with data.
In such a system, if an approach is taken to achieve the improvement of the data transmission rate and the improvement of the communication range simultaneously, since the range of the variation of the frequency of signal to be put to use is wide, the frequency band also becomes wide. Further, since a restriction is imposed according
Birch & Stewart Kolasch & Birch, LLP
Mitsubishi Denki & Kabushiki Kaisha
Yang Clara
Zimmerman Brian
LandOfFree
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