JP2004070804A - Wireless ic card reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless IC card reader capable of dispensing with a complicated adjustment and improving the wave detection efficiency by realizing a synchronous wave detection without using a carrier reproduction circuit. <P>SOLUTION: This wireless IC card reader 100 has a synchronous wave detection circuit, and it performs a radio communication with a wireless IC card to read a response signal from the wireless IC card. This reader has an oscillation circuit 102 for oscillating a transmission carrier wave signal, a modulation amplifier part 107 for outputting a transmission signal as a modulation signal, a transmission modulation amplifier part 105 for modulating the transmission carrier wave signal based on the modulation signal, and a receiving demodulation part 114 having a DBM (Double Balanced Mixer) 120 as the synchronous wave detection circuit to demodulate a receiving radio signal. The DBM inputs the receiving radio signal and the transmission carrier wave signal from the oscillation circuit. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless IC card reader having a synchronous detection circuit, performing wireless communication with a wireless IC card, and reading a response signal from the wireless IC card.
[0002]
[Prior art]
In the conventional wireless IC card reader, since the modulation method is an amplitude modulation method (AM method), the reception and demodulation unit uses the most common envelope detection using a diode.
[0003]
FIG. 3 is a block diagram showing a conventional wireless IC card reader.
[0004]
In FIG. 3, 100M is a wireless IC card reader, 101 is a 13.56 MHz crystal oscillator, 102 is an oscillation circuit that oscillates a transmission carrier signal having a transmission carrier frequency of 13.56 MHz using the crystal oscillator 101, and 103 is A buffer amplifier circuit for amplifying and stabilizing the transmission carrier signal oscillated by the oscillation circuit 102, an excitation amplifier circuit 104 for amplifying the transmission power amplifier circuit 105 so that sufficient excitation can be performed, a low-pass filter 106, and a low-pass filter 107 A modulation amplifier 108 receives a transmission signal a and outputs a modulation signal. An amplification circuit 108 amplifies the transmission signal a as a 106 kbps NRZ encoding digital signal and amplifies the modulation amplification circuit 110 so as to be sufficiently excited. , 109 are baseband filters as low-pass filters, and 111 is a transmitting antenna 112 and a receiving band. An antenna shared with the antenna 113, 114 is a reception demodulation unit, 115 is a 13.56 MHz bandpass filter, 116 is a diode detection circuit, 117 is a low-pass filter, 118 is a signal amplification circuit, and 110 is a 106 kbps reception signal b. Waveform shaping circuit.
[0005]
The general operation of the wireless IC card reader of FIG. 3 will be described. A low-pass filter (baseband filter) 109 is provided downstream of the amplifying circuit 108 so as not to deteriorate radio wave quality due to unnecessary frequency components of the modulated wave. The transmission signal amplified by the modulation amplification circuit 110 is supplied to the transmission power amplification circuit 105 as a modulation signal m, whereby an AM wave signal is obtained as an output signal of the transmission power amplification circuit 105. This AM wave signal has its harmonic distortion component removed by the low-pass filter 106, and is transmitted by the transmission antenna 112.
[0006]
FIG. 4 is a circuit diagram showing a general wireless IC card.
[0007]
4, reference numeral 200 denotes a wireless IC card, 201 denotes an antenna coil, 202 denotes a control unit, 203 denotes a load fluctuation circuit, 204 denotes a detector, and 205 denotes a control circuit having a memory 206.
[0008]
The operation of the wireless IC card reader 100M of FIG. 3 and the wireless IC card 200 of FIG. 4 will be described. Note that the transmission signal generation unit that generates the transmission signal a and the reception signal processing unit that processes the reception signal b are not relevant to the present invention, and thus description thereof is omitted.
[0009]
In FIG. 3, a 13.56 MHz transmission wave transmitted from the transmission antenna 112 is guided to the card-side antenna coil 201 in FIG. 4, is detected and rectified by the detection diode 204, and is a component in the detected and rectified signal. There are a DC component and an AM modulation signal component of a transmission wave (hereinafter referred to as a “detection signal”). The DC component is guided to the control circuit 205 and the detected and rectified DC component acts as a DC power supply for the control circuit 205. At the same time, the detection signal is analyzed and determined by the analysis means of the control circuit 205 as to whether or not the signal is a desired received signal. If the signal is not the desired received signal, the control circuit 205 does not react at all and nothing appears in the response signal d. Absent. In the case of a desired reception signal, a response signal d of the logic operation is sent to the load variation circuit 203. The load variation circuit 203 generally has a configuration of a parallel circuit of a fixed capacitor and a variable capacitor or a variable resistor. When there is no response signal d, the parallel resonance frequency of the antenna coil 201 and the fixed capacitor becomes 13. Resonating at 56 MHz, in a state in which a transmission wave is most induced, and when there is a response signal d, the 13.56 MHz resonance point is changed by the action of the variable capacitor or variable resistor. In addition, transmission wave induction is reduced. The induced change of the antenna coil 201 becomes the same change as the response signal d, and the change is a change of the excitation of the transmission wave of the transmitting antenna 112 of FIG. As a result, the transmission voltage of the transmission antenna 112 has the same effect as the logic signal of the response signal d, and finally the transmission voltage of the transmission antenna 112 is induced in the reception antenna 113 arranged near the transmission antenna 112. Thus, the amplitude-modulated radio wave modulated with the logic response signal d from the card side can be received, and the received amplitude-modulated wave is input to the reception demodulation unit 114 as a received radio wave signal. This received radio wave signal passes through a 13.56 MHz bandpass filter 115, and is detected by a diode detection circuit 116 by diode detection (envelope detection) to become a detection signal. Since the detection signal output from the diode detection circuit 116 has a low level, it passes through the low-pass filter 117 and is amplified by the signal amplification circuit 118. The amplified detection signal output from the signal amplification circuit 118 is converted into a digital signal b (that is, a reception signal b) by a waveform shaping circuit 119 using a comparator. At this time, the reception radio signal generated by the reception antenna 113 is a signal whose amplitude has been modulated by the load variation circuit 203 of the wireless IC card 200, and the amplitude-modulated reception radio signal is demodulated to a predetermined level. By amplifying and shaping the waveform, the digital signal b can be extracted.
[0010]
Since the modulation degree of the amplitude modulation generated by the load fluctuation control of the card-side antenna coil 201 changes depending on the distance between the antenna coil 201 and the transmitting antenna 112, that is, the coupling degree, it is not possible to keep the wireless IC card 200 at a fixed position manually. Is difficult, and must be treated as if the degree of coupling is constantly changing. That is, it is necessary to assume that the modulation degree changes from 1 or more to nearly 0, and in the detection method using the envelope detection by the diode detection circuit 116 in FIG. 3, the voltage of the detection input is a forward voltage drop of the diode (about 0). 6 V) or more, and the signal voltage after detection, that is, the detection efficiency is poor, and the signal-to-noise (S / N) performance of the signal amplification circuit 118 after detection is likely to deteriorate. If the signal-to-noise ratio (S / N) is poor, the signal level that can be received is limited due to the capability of the signal processing circuit of the waveform shaping circuit 119. As a result, communication between the wireless IC card 200 and the transmitting antenna 112 is possible. It is said that there is no effective improvement method in the method based on the envelope detection by the original diode detection circuit 116 with respect to the improvement of extending the proper distance, and this is the limit.
[0011]
Improving the communicable distance is a fatal issue for wireless IC cards, so if the distance is increased, the operator holding the card will be able to move between the card and the reader without having to worry about getting closer than necessary. Can be exchanged, and a smooth and comfortable wireless IC card operation environment can be constructed.
[0012]
In order to realize a wireless IC card reader having a reception circuit with good detection efficiency, there is a detection circuit using a synchronous detection method (generally called product detection), and a double balanced mixer (hereinafter, referred to as “product detection”). A wireless IC card reader 100N as shown in FIG. 5 that constitutes a synchronous detection circuit using “DBM”) is conceivable and can be put to practical use.
[0013]
Next, the mechanism and operation of the device having the configuration shown in FIG. 5 will be described. FIG. 5 is a block diagram showing a wireless IC card reader using synchronous detection to improve detection efficiency.
[0014]
5, constituent elements 101 to 109 are the same as those in FIG. 3, and are denoted by the same reference numerals, and detailed description thereof will be omitted. Reference numeral 120 denotes a DBM, 121 denotes a carrier reproduction circuit, 122 denotes a PLL circuit, 123 denotes a low-pass filter (hereinafter, referred to as “LPF”), and 124 denotes a comparison frequency oscillation circuit. The operation of the detection circuit using the synchronous detection system having these configurations will be described.
[0015]
First, the carrier reproduction circuit 121 will be described. The purpose is a circuit block for generating a signal synchronized with the same frequency as the carrier component from a 13.56 MHz AM reception wave received from the reception antenna 113 through the bandpass filter 115. The operation is performed by a voltage variable frequency oscillator (VCO). A 13.56 MHz band signal is oscillated by a comparison frequency oscillating circuit 124, which is compared with the AM reception wave by a PLL (Phase Locked) circuit, and an error signal between the VCO signal and the AM reception wave is output. Is taken out and smoothed by the LPF 123, and a phase-locked signal can be created as the VCO signal at exactly the same frequency as the carrier of the AM reception wave. This signal is called a reproduction carrier and is indispensable for synchronous detection using DBM.
[0016]
The operation principle of the synchronous detection of the DBM 120 will be described with reference to FIG. FIG. 6A is a circuit diagram showing a configuration of a general DBM, and FIG. 6B is a waveform diagram showing an operation waveform of the DBM in FIG. 6A.
[0017]
The DBM 6 shown in FIG. 6A includes diodes D1, D2, D3, and D4 arranged in a ring and transformers T1 and T2 called phase distributors, and has three terminal pairs (hereinafter, referred to as "ports"). have. The operation of the DBM 6 having such a configuration will be described. When a signal is applied to port 1 and port 3, respectively, the output waveform appearing at the output of port 2 is diode D1 during the positive half cycle of the polarity of the signal at port 3, as shown in FIG. And D2 are turned on, and the diodes D3 and D4 are repeatedly turned on during the time of the negative half cycle of the polarity of the signal of the port 3, and the phase of the input signal of the port 1 is changed during the time of the negative half cycle. A signal having a waveform inverted by 180 degrees appears as a port 2 signal.
[0018]
This operation is achieved when a 13.56 MHz received wave is applied to port 1 and a reproduced carrier having a comparison frequency of 13.56 MHz described above is applied to port 3 as shown in FIG. This means that the component multiplied by the signal at port 3 appears at port 2, so that a modulated wave can be extracted from the received signal after all, and can operate as a detection circuit. This detection method is generally called direct conversion detection using DBM, as opposed to envelope detection by the conventional diode detection circuit 116, and is called active type using transistors and ICs as shown in FIG. Since conversion gain can be obtained by using DBM, AM detection with higher efficiency can be performed. FIG. 7 is a circuit diagram showing a general active DBM. Normally, this active DBM is often used. Port 1 in FIG. 6A corresponds to terminals 1 and 4 in FIG. 7, and port 2 similarly has terminals 6 and 12 and port 3 in FIG. Correspond to the terminals 8 and 10, and the operation principle is the same as that of FIG.
[0019]
[Problems to be solved by the invention]
However, in the above-described conventional wireless IC card reader 100N, although synchronous detection using the DBM 120 is used, the carrier reproduction circuit 121 is indispensable due to the characteristics of the circuit. There is a problem that control and adjustment for reproduction are complicated.
[0020]
This wireless IC card reader is required to be able to realize synchronous detection without using a carrier reproducing circuit.
[0021]
The present invention provides a wireless IC card reader capable of achieving synchronous detection without using a carrier recovery circuit, eliminating the need for complicated adjustments, and improving detection efficiency. The purpose is to do.
[0022]
[Means for Solving the Problems]
A wireless IC card reader according to the present invention includes a synchronous detection circuit, performs wireless communication with the wireless IC card, and reads a response signal from the wireless IC card. An oscillation circuit that oscillates a transmission carrier signal, a modulation amplification unit that outputs the transmission signal as a modulation signal, a transmission modulation amplification unit that modulates the transmission carrier signal based on the modulation signal, and a DBM as a synchronous detection circuit. And a reception demodulation unit for demodulating the received radio signal. The DBM has a configuration for inputting the received radio signal and the transmission carrier signal from the oscillation circuit.
[0023]
Thereby, synchronous detection can be realized without using a carrier reproduction circuit, and a wireless IC card reader that can eliminate complicated adjustment and improve detection efficiency can be obtained.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
A wireless IC card reader according to claim 1 of the present invention has a synchronous detection circuit, performs wireless communication with the wireless IC card, and reads a response signal from the wireless IC card. An oscillation circuit that oscillates a transmission carrier signal, a modulation amplification unit that outputs the transmission signal as a modulation signal, a transmission modulation amplification unit that modulates the transmission carrier signal based on the modulation signal, and a DBM that serves as a synchronous detection circuit. And a receiving demodulation unit for demodulating the received radio signal. The DBM receives the received radio signal and the transmission carrier signal from the oscillation circuit.
[0025]
According to this configuration, the reception radio signal and the transmission carrier signal from the oscillation circuit are input to the DBM to form a synchronous detection circuit, that is, a reproduced carrier signal for demodulating the reception radio signal to obtain the reception signal. Therefore, synchronous detection can be realized without using a carrier recovery circuit, which is conventionally required, and complicated adjustment is not required, and the detection efficiency can be improved. Has the effect of increasing the distance to
[0026]
The wireless IC card reader according to claim 2, comprising a synchronous detection circuit, performing wireless communication with the wireless IC card, and reading a response signal from the wireless IC card, An oscillation circuit that oscillates a transmission carrier signal, a modulation amplification unit that outputs the transmission signal as a modulation signal, a transmission modulation amplification unit that modulates the transmission carrier signal based on the modulation signal, and a transmission carrier signal that is input from the oscillation circuit. A modulation / demodulation unit having a DBM as a synchronous detection circuit for modulating a transmission signal and demodulating a received radio signal, a first changeover switch disposed on an input side of the DBM, and disposed on an output side of the DBM; A second changeover switch, and a third changeover switch disposed between the oscillation circuit and the output side of the DBM during transmission. , A first changeover switch inputs a modulation signal to a DBM, a second changeover switch outputs a signal from the DBM to an amplification circuit of a transmission modulation amplifier, and at the time of reception, the first changeover switch receives a reception radio signal. Is input to the DBM, the second changeover switch outputs the signal from the DBM to the low-pass filter of the modem, and the third changeover switch directly connects the oscillation circuit to the output side of the DBM during transmission. It is what it was.
[0027]
According to this configuration, in addition to having the function of claim 1, it is possible to generate an amplitude-modulated wave signal by quadrature modulation using the DBM even at the time of transmission, thereby eliminating the need for a modulation amplification circuit and reducing power consumption. It has the effect of being able to.
[0028]
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0029]
(Embodiment 1)
FIG. 1 is a block diagram showing a wireless IC card reader according to Embodiment 1 of the present invention.
[0030]
In FIG. 1, the components 101 to 115 and 117 to 120 are the same as those in FIG. 100 is a wireless IC card reader. The difference between the configuration shown in FIG. 1 and the configuration shown in FIG. 5 is that the carrier reproduction circuit 121 shown in FIG. 5 is eliminated and the signal from the viewing amplification circuit 103 is input to the DBM 120. Here, the transmission power amplification circuit 105 forms a transmission modulation amplification unit.
[0031]
The operation of the wireless IC card reader 100 thus configured will be described.
[0032]
As described in the related art, the reception radio signal induced in the reception antenna 113 is filtered by a bandpass filter 115 to remove unnecessary radio signals, and input to a signal input terminal (not shown) of the DBM 120. On the other hand, by inputting the transmission carrier signal oscillated by the oscillation circuit 102 and amplified by the buffer amplifier circuit 103 to a carrier input terminal (not shown) of the DBM 120, a demodulated signal by beatdown is obtained as an output signal of the DBM 120. Can be The demodulated signal passes through a low-pass filter 117, is amplified to a predetermined level by a signal amplifier circuit 118, is waveform-shaped by a waveform shaping circuit 119, and is output as a received signal b.
[0033]
As described above, in the related art, a carrier recovery circuit that extracts a demodulation carrier signal from a received radio signal is required, but in the present embodiment, it is noted that a transmission carrier signal can be used as a reception reproduction carrier signal. Demodulation by synchronous detection in the DBM 120 can be achieved.
[0034]
As described above, according to the present embodiment, the oscillation circuit 102 that oscillates the transmission carrier signal, the modulation amplifier 107 that outputs the transmission signal a as the modulation signal m, and modulates the transmission carrier signal based on the modulation signal m And a DBM 120 as a synchronous detection circuit, and a reception demodulation unit 114 for demodulating the received radio signal. The DBM 120 converts the received radio signal and the transmission carrier signal from the oscillation circuit 102 into each other. By inputting the received radio wave signal and the transmission carrier signal from the oscillation circuit 102 to the DBM 120 to form a synchronous detection circuit, that is, for obtaining the reception signal b by demodulating the transmission carrier signal to the reception radio signal. Since it can be used as a reproduced carrier signal, synchronous detection can be realized without using a carrier reproducing circuit, which was required in the past. Complex adjustment while eliminating the need can be improved detection efficiency, it can be extended the distance between the wireless IC card 200.
[0035]
(Embodiment 2)
FIG. 2 is a block diagram showing a wireless IC card reader according to Embodiment 2 of the present invention.
[0036]
In FIG. 1, the components 101 to 109, 111 to 113, 115, and 117 to 120 are the same as those in FIG. 100A is a wireless IC card reader, 125 is a modulator / demodulator, 126 is a third switch, 127 is a first switch, and 128 is a second switch. The configuration shown in FIG. 2 is different from the configuration shown in FIG. 1 in that the modulation amplification circuit 110 shown in FIG. 1 is removed and first, second, and third changeover switches 127, 128, 126 and a DC offset circuit 129 are provided. And T and R in FIG. 2 represent contact contact positions during transmission and reception. That is, DBM 120 operates as a detector as in Embodiment 1 at the time of reception R, and operates as an AM modulator as shown in FIG. 7 at the time of transmission T as shown in FIG. The transmission system is constituted by the transmission power amplification circuit 105 from the excitation amplification circuit 104 without passing through the modulation amplification circuit 110 of FIG.
[0037]
The operation of the wireless IC card reader 100A thus configured will be described. The wireless IC card reader 100A is characterized in that a changeover switch is provided so that the DBM 120 used in the reception demodulation unit 114 of the first embodiment is also used as a transmission modulation circuit.
[0038]
The changeover switches 126 to 128 are controlled so as to switch between the contact point T and the contact point R at the time of transmission and at the time of reception. The operation when the changeover switches 126 to 128 are switched to the contact R at the time of reception is the same as the operation in the first embodiment, and the description thereof will be omitted. When the changeover switches 126 to 128 are switched to the contact point T at the time of transmission, the transmission signal a is amplified by the amplifier circuit 108 and is input to the signal input terminal of the DBM 120 via the baseband filter 109. As a result, AM is applied to the transmission carrier signal from the buffer amplification circuit 103 and output as an AM wave signal from the DBM 120. This AM wave signal is amplified by the excitation amplification circuit 104 via the changeover switch 128, and the transmission power is The transmission radio signal is power-amplified by the amplification circuit 105.
[0039]
As described above, according to the present embodiment, oscillation circuit 102 that oscillates a transmission carrier signal, modulation amplification section 107 that outputs transmission signal a as a modulation signal, and transmission that modulates the transmission carrier signal based on the modulation signal. Modulation / amplification sections 104, 105, and 120; a modulation / demodulation section 125 that has a DBM 120 as a synchronous detection circuit that inputs a transmission carrier signal from the oscillation circuit 102, modulates a transmission signal, and demodulates a received radio signal; A first changeover switch 127 disposed on the output side of the DBM 120, a second changeover switch 128 disposed on the output side of the DBM 120, and the output side of the DBM 120 during transmission. A third changeover switch 126, and at the time of transmission, the first changeover switch 127 inputs a modulation signal to the DBM 120; The second changeover switch 128 outputs the signal from the DBM 120 to the amplifier circuits 104 and 105 of the transmission modulation amplifying unit. At the time of reception, the first changeover switch 127 inputs the received radio wave signal to the DBM 120 and the second changeover switch 128 Outputs the signal from the DBM 120 to the low-pass filter 117 of the modulation / demodulation unit 125, and the third changeover switch 126 directly connects the oscillation circuit 102 and the output side of the DBM 120 at the time of transmission. In addition to the same operation and effect as described, the amplitude modulation wave signal can be transmitted without using the modulation amplifier circuit 110 using the DBM 120 at the time of transmission, so that power consumption of the circuit can be reduced. it can.
[0040]
【The invention's effect】
As described above, the wireless IC card reader according to claim 1 of the present invention has a synchronous detection circuit, performs wireless communication with the wireless IC card, and transmits a response signal from the wireless IC card. A wireless IC card reader that reads, an oscillation circuit that oscillates a transmission carrier signal, a modulation amplification unit that outputs the transmission signal as a modulation signal, and a transmission modulation amplification unit that modulates the transmission carrier signal based on the modulation signal. It has a DBM as a synchronous detection circuit, and has a reception demodulation unit for demodulating a received radio signal. The DBM receives the received radio signal and oscillates by inputting the received radio signal and the transmission carrier signal from the oscillation circuit. A synchronous detection circuit is formed by inputting the transmission carrier signal from the circuit to the DBM, that is, the reception carrier signal is demodulated from the transmission carrier signal and the reception signal is demodulated. , Which can be used as a reproduced carrier signal to perform synchronous detection without using a carrier reproduction circuit, which has been required in the past, eliminating the need for complicated adjustments and improving the detection efficiency. And the advantageous effect that the distance to the wireless IC card can be extended can be obtained.
[0041]
According to the wireless IC card reader of the second aspect, the wireless IC card reader has a synchronous detection circuit, performs wireless communication with the wireless IC card, and reads a response signal from the wireless IC card. An oscillation circuit that oscillates the transmission carrier signal, a modulation amplification unit that outputs the transmission signal as a modulation signal, a transmission modulation amplification unit that modulates the transmission carrier signal based on the modulation signal, and a transmission carrier signal from the oscillation circuit. A modulation / demodulation unit for modulating a transmission signal and demodulating a received radio signal; a first changeover switch disposed on an input side of the DBM; and a modulation / demodulation switch disposed on an output side of the DBM. And a third changeover switch disposed between the oscillation circuit and the output side of the DBM during transmission. At the time of transmission, the first changeover switch inputs a modulation signal to the DBM, the second changeover switch outputs a signal from the DBM to the amplifier circuit of the transmission modulation amplifier, and at the time of reception, the first changeover switch receives the radio wave. A signal is input to the DBM, a second changeover switch outputs a signal from the DBM to a low-pass filter of the modem, and a third changeover switch directly connects the oscillation circuit to the output side of the DBM during transmission. Accordingly, the effect described in claim 1 can be obtained, and an amplitude-modulated wave signal by quadrature modulation can be generated using the DBM at the time of transmission, so that a modulation amplification circuit is not required and power consumption is reduced. The advantageous effect that can be obtained is obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a wireless IC card reader according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a wireless IC card reader according to a second embodiment of the present invention.
FIG. 3 is a block diagram showing a conventional wireless IC card reader.
FIG. 4 is a circuit diagram showing a general wireless IC card.
FIG. 5 is a block diagram showing a wireless IC card reader using synchronous detection to improve detection efficiency.
FIG. 6A is a circuit diagram showing a configuration of a general DBM.
(B) A waveform diagram showing the operation waveform of the DBM in (a).
FIG. 7 is a circuit diagram showing a general active DBM.
[Explanation of symbols]
100, 100A Wireless IC card reader
101 crystal oscillator
102 Oscillation circuit
103 Buffer amplification circuit
104 Excitation amplification circuit
105 Transmission power amplifier circuit
106, 117 Low-pass filter
107 Modulation amplifier
108 amplifier circuit
109 Baseband filter
110 Modulation amplification circuit
111 antenna
112 transmitting antenna
113 receiving antenna
114 reception demodulation unit
115 bandpass filter
116 Diode detection circuit
118 signal amplification circuit
119 Waveform shaping circuit
120 DBM
125 Modulator / demodulator
126 third changeover switch
127 1st changeover switch
128 Second changeover switch
129 DC offset circuit
200 wireless IC card
201 antenna coil
202 control unit
203 Load fluctuation circuit
204 detector
205 control circuit
206 memory

Claims (2)

A wireless IC card reader having a synchronous detection circuit, performing wireless communication with a wireless IC card, and reading a response signal from the wireless IC card,
An oscillation circuit that oscillates a transmission carrier signal, a modulation amplification unit that outputs the transmission signal as a modulation signal, a transmission modulation amplification unit that modulates the transmission carrier signal based on the modulation signal, and a DBM as the synchronous detection circuit. Having a receiving demodulation unit for demodulating a received radio signal,
The wireless IC card reader according to claim 1, wherein the DBM inputs the received radio wave signal and a transmission carrier signal from the oscillation circuit. A wireless IC card reader having a synchronous detection circuit, performing wireless communication with a wireless IC card, and reading a response signal from the wireless IC card,
An oscillation circuit that oscillates a transmission carrier signal, a modulation amplification unit that outputs the transmission signal as a modulation signal, a transmission modulation amplification unit that modulates the transmission carrier signal based on the modulation signal, and a transmission carrier signal from the oscillation circuit. A modulation / demodulation unit that has a DBM as the synchronous detection circuit that modulates a transmission signal and demodulates a received radio signal, a first changeover switch disposed on an input side of the DBM, and an output of the DBM. And a third changeover switch disposed between the oscillation circuit and the output side of the DBM at the time of transmission.
At the time of transmission, the first changeover switch inputs the modulation signal to the DBM, and the second changeover switch outputs a signal from the DBM to an amplification circuit of the transmission modulation amplification unit,
At the time of reception, the first changeover switch inputs the received radio wave signal to the DBM, the second changeover switch outputs a signal from the DBM to a low-pass filter of the modem, and the third changeover switch A wireless IC card reader, wherein a switch directly connects the oscillation circuit and an output side of the DBM during the transmission.

Images