JPH1174939A - Communication equipment and communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide communication equipmeutt/method which can speedily and securely recognize the switching of a transmission signal. SOLUTION: An inverter 3 for generating and transmitting a signal for canceling the component of a signal which is transmitted till then at timing for switching the transmission signal in accordance with transmitted data, a switching circuit 4 and a switching control circuit 5 are provided. When the transmission signal is changed, the signal canceling the signal which is transmitted till then is transmitted. Thus, the influence of the signal which is transmitted till then is speedily cancelled and the switching of the transmission signal is easily recognized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication apparatus and a communication method, and more particularly, to a communication system for supplying operating power to a data carrier while transmitting and receiving data by wireless communication with the data carrier. It is suitable for use.

[0002]

2. Description of the Related Art In a data carrier communication system including a data carrier such as an IC card and a tag and a communication device called an interrogator for wirelessly transmitting and receiving signals to and from the data carrier, the communication device and the data In order to be able to transmit and receive data wirelessly even when the distance from the carrier is long, power is supplied from the communication device side to the data carrier side.

[0003] For this reason, when the distance between the communication device and the data carrier approaches, an excessive voltage is generated in the antenna coil provided in the data carrier, and the antenna coil is provided in the data carrier. Semiconductor chip may be destroyed.

As a countermeasure, an overvoltage limiting circuit is provided on the data carrier to suppress the maximum voltage.
In addition, in the operation at the short distance, there is an advantage that the impedance of the circuit of the data carrier is reduced and the response of the circuit is fast. Therefore, the communication at the short distance can be performed without any problem in the data carrier communication system.

[0005] Therefore, a problem in the data carrier communication system occurs at the time of long-distance communication in which the data carrier exists near the operation limit. By the way, the most effective method for increasing the reception output at the time of long-distance communication is to increase the transmission output. However, there is a limit in increasing the transmission output due to the radio law and the like. In addition, since the data carrier does not have a power source, there is a limit in increasing the transmission output to extend the communication distance.

Therefore, as one method of extending the communication distance, it is known to reduce the load on the tuning circuit by lowering the power consumption of the data carrier and increase the tuning Q in the antenna coil. Have been.

On the other hand, in a data carrier communication system, there is a demand to increase a communication data rate. In order to increase the communication data rate, it is necessary to widen the bandwidth of the transmission path, so it is effective to reduce the tuning Q as much as possible. However, lowering the tuning Q is inconsistent with the above-described device for extending the communication distance.

On the communication device side, it is preferable to tune the transmitting antenna in order to improve the power efficiency at the output end or to reduce the level of unnecessary radiation such as harmonics. However, tuning the transmitting antenna narrows the band in which radio waves can be radiated efficiently, so that it is not possible to satisfy the demand for increasing the communication data rate.

Therefore, conventionally, data communication is performed between a data carrier and a communication device while balancing the above-mentioned requirements among various characteristics. FIG.
FIG. 9 is a configuration diagram illustrating a schematic configuration of a main part of a transmission unit in a conventional communication device that performs data communication using the K communication method. FIG.

As shown in FIG. 8, the communication device includes a carrier oscillator 81 that oscillates a carrier wave S1 having a predetermined frequency.
A switch circuit 82 for generating a transmission signal S2 by intermittently transmitting a carrier wave S1 output from the carrier oscillator 81 in accordance with transmission data, a switching control circuit 83 for controlling a switching operation of the switch circuit 82, and an output from the switch circuit 82 An amplifier 84 amplifies the transmitted transmission signal S2 to a predetermined level, an antenna circuit 85 that radiates the transmission signal S2 supplied from the amplifier 84 to space as an electromagnetic wave, and the like.

The operation of the communication device configured as described above will be described with reference to FIG. In FIG.
(A) shows data to be transmitted, in this case “0, 0,
An example of transmitting 1, 0, 1, 1 "data is shown.

FIG. 9B shows that the switching control circuit 83 operates according to the transmission data shown in FIG.
This shows a transmission signal S2 generated by intermittent 1s, and when "0" is transmitted, there is a blank portion where no carrier is transmitted at the end of the data transmission period. When transmitting “1”, the carrier is transmitted during the entire data transmission period, and data “0” and data “1” are transmitted in order.

FIG. 9C shows a waveform in the tuning circuit of the antenna circuit 85. Since the antenna circuit 85 performs the above-mentioned tuning, as shown in FIG. 9C, in the transmission output, the radiated power can be made completely zero even in a blank portion where no carrier is transmitted. Is gone.

FIG. 9D shows a waveform at a receiving point on the data carrier side. Since the Q of the antenna circuit of the data carrier is high, the delay in the tuning circuit of the antenna is large, and the reception output is considerably large even in the blank portion.

Next, referring to FIGS. 10 and 11,
A case where data communication is performed by the conventional FSK method will be described.
FIG. 10 is a configuration diagram showing a schematic configuration of a transmission unit of a conventional communication device, and FIG. 11 is a characteristic diagram showing contents of data to be transmitted and operation waveforms of each unit.

In FIG. 10, reference numeral 101 denotes an oscillator that oscillates a carrier having a predetermined frequency, and reference numeral 102 denotes a frequency of the carrier output from the oscillator 101 divided by 1 / N to generate a first carrier having a frequency f ₁ . First frequency divider, 103
Is a second frequency divider for generating a second carrier frequency f ₂ of the frequency of the carrier output from the oscillator 101 to 1 half circumference of M minutes.

A reference numeral 104 designates one of the first carrier f ₁ outputted from the first frequency divider 102 and the second carrier f ₂ outputted from the second frequency divider 103. To generate a transmission signal S2.

A switching control circuit 105 controls the switching operation of the switch circuit 104.
An amplifier 106 amplifies the transmission signal S2 output from the switch circuit 104 to a predetermined level. An antenna circuit 107 radiates a transmission signal S2 supplied from the amplifier 106 to space as an electromagnetic wave.

Next, the operation of the communication apparatus configured as described above will be described with reference to FIG. In FIG. 11, (A) shows data to be transmitted, and also in this case, “0,
An example of transmitting 0, 1, 0, 1, 1 "data is shown.

FIG. 11B shows a transmission signal S2 generated by performing switching control in accordance with the transmission data shown in FIG. 11A. and so as to transmit the second frequency f ₂ in the case of sending the frequency f _1, transmitting a "1". For example, the first frequency f ₁ is 117 KHz, and the second frequency f ₂
Is 125 KHz.

FIG. 11C shows a waveform in the tuning circuit of the antenna circuit 107. Tuning of the antenna circuit 107 is series resonance, it is combined the resonance frequency to the first frequency f ₁ and the second intermediate frequency f _2. Therefore, as shown in FIG. 11C, the antenna circuit 107 resonates in series at the boundary of the modulation, so that the amplitude is momentarily reduced.

On the other hand, the antenna circuit of the data carrier has parallel resonance, and its resonance frequency is set to the first frequency f _1.
When is matched to a second intermediate frequency f _2. For this reason,
As shown in FIG. 11D, the antenna circuit resonates in parallel at the boundary of the modulation, and the amplitude increases instantaneously.

[0023]

As mentioned above, AS
In the case of performing communication in the K system, if the tuning Q of the antenna coil is increased in order to enable long-distance communication, a delay in response increases, and there is a problem that demodulation in ASK becomes difficult. .

In the case of performing communication by the FSK method, if an antenna circuit having a high Q is used to secure a long communication distance, a period during which the amplitude is large as shown in FIG. As L becomes longer, it takes time to recognize that the frequency of the received signal has been switched, and thus there has been a problem that it becomes difficult to perform FSK demodulation.

The present invention has been made in consideration of the above-described problems, and has as its object to provide a communication device and a communication method capable of promptly and reliably recognizing switching of a transmission signal.

[0026]

According to the present invention, there is provided a communication apparatus for switching a transmission signal in accordance with data to be transmitted. Means for generating and transmitting a signal for canceling.

Another feature of the communication device of the present invention is that the transmission signal is transmitted by the ASK method, and that the AM signal which has been transmitted up to that time during the blank period immediately after the transmission of the signal is stopped. Are characterized by transmitting AM signals of opposite phases.

Another feature of the communication device of the present invention is that the transmission signal is transmitted by an FSK method,
After the frequency of the transmission signal is changed, a signal having a frequency opposite to the frequency transmitted so far is superimposed on a signal having a frequency to be transmitted next and transmitted.

Further, according to the communication method of the present invention, in the communication method for switching a transmission signal in accordance with data to be transmitted, a signal for canceling a component of a signal that has been transmitted up to now is switched at the timing of switching the transmission signal. It is generated and transmitted.

Another feature of the communication method of the present invention is that the transmission signal is transmitted by the ASK method, and the transmission of the AM signal and the transmission of the AM signal during the blank period immediately after the signal transmission is stopped. Are characterized by transmitting AM signals of opposite phases.

Another feature of the communication method of the present invention is that the transmission signal is transmitted by an FSK method,
After the frequency of the transmission signal is changed, a signal having a phase opposite to that of the previously transmitted frequency is superimposed on a signal of the next transmission frequency and transmitted.

[0032]

Since the present invention has the above technical means, after the transmission signal is changed, a signal for canceling the signal transmitted before the transmission signal is changed is supplied to the antenna circuit, so that the transmission is performed up to that time. The effect of the signal that has been transmitted is quickly canceled, and the switching of the transmission signal can be quickly and reliably recognized.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a communication device and a communication method according to the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention, and is a configuration diagram showing a schematic configuration of a main part of a communication device for transmitting a signal in an ASK system. As shown in FIG. The communication device 10 is used for performing data transmission with the data carrier 20.

In FIG. 1, reference numeral 1 denotes a carrier S having a predetermined frequency.
1 is a first switch circuit that generates a transmission signal S2 by intermittently transmitting a carrier wave S1 output from the carrier oscillator 1 according to transmission data.

3 is an inverter for inverting the phase of the carrier wave S1 output from the carrier oscillator 1, 4 is a second switch circuit for intermittently interposing the carrier wave S1B (see FIG. 2) inverted by the inverter 3, and 5 is a first switch circuit. Is a switching control circuit that controls the switching operation of the switch circuit 2 and the second switch circuit 4.

6 is a transmission signal S2 output from the first switch circuit 2 or the second switch circuit 4
An amplifier for amplifying the transmission signal S3 output from the amplifier to a predetermined level;
2, an antenna circuit that radiates S3 into space as an electromagnetic wave.

Next, the operation of the communication apparatus of the present embodiment configured as described above will be described. The carrier wave S1 output from the carrier oscillator 1 is supplied to the first switch circuit 2 and to the second switch circuit 4 via the inverter 3 respectively.

Therefore, the signal supplied to the first switch circuit 2 is the same as the conventional signal shown in FIG. 8, but the signal supplied to the second switch circuit 4 is
The phase of the carrier wave S1 output from the carrier oscillator 1 is 1
The signal is inverted by 80 °.

The switching control circuit 5 controls the switching operation of the first switch circuit 2 and the second switch circuit 4 according to the data to be transmitted. In the case of the present embodiment, the switching control of the first switch circuit 2 is the same as the conventional one. When "0" is transmitted, the switching is performed such that there is a blank portion where no carrier is transmitted at the end of the data transmission period. Controlling.

In the present embodiment, as shown in FIG. 2, the first switch circuit 2 is opened at time t0 to stop the transmission of the carrier wave S1, and then the second switch circuit 4 is closed for a short period of time. And the signal S1B inverted by the inverter 3
Is transmitted only for a few cycles.

Hereinafter, the switch operation will be described in detail with reference to FIG. In FIG. 4, (A) shows data to be transmitted, in which case “0, 0, 1, 0, 1,.
An example of transmitting 1 "data is shown.

FIG. 4B shows a transmission signal S4 generated by the switching control circuit 5 performing switching control in accordance with the transmission data shown in FIG. 4A, and is "0". Is transmitted, there is a blank portion where the carrier is not transmitted after transmitting the data. When transmitting “1”, the carrier is transmitted during the entire data transmission period, and data “0” and data “1” are transmitted continuously.

In the present embodiment, as described above, after transmitting the signal S2 for "0", the signal S1B inverted by the inverter 3 is transmitted for several cycles, for example, two to three.
Only five cycles are transmitted. The portion of the signal S1B is shown by hatching in FIG.

As described above, by adding the signal S1B having the opposite phase to the signal transmitted so far, the waveform at the transmission point in the present embodiment becomes as shown in FIG. The output due to the response delay in the antenna circuit 7 is completely canceled, and the output is slightly generated on the side opposite to the output caused by the response delay.

Therefore, in the case of the present embodiment, the receiving point of data carrier 20, that is, data carrier 2
FIG. 4D shows the reception waveform of the antenna circuit 21 of FIG.
As shown in (1), during the period corresponding to the blank portion of the transmission signal, the amplitude of the signal can be reliably reduced.
SK demodulation can be performed easily and reliably.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 illustrates the present invention using FSK.
FIG. 2 is a configuration diagram of a main part of a communication device showing an example applied to a system. In FIG. 5, reference numeral 51 denotes an oscillator that oscillates a carrier having a predetermined frequency, and reference numeral 52 denotes a first oscillator that divides the frequency of the carrier input from the oscillator 51 by 1 / N to generate a first carrier having a frequency f ₁ . divider, 53 denotes a second frequency divider for generating a second carrier frequency f ₂ of the frequency of the carrier input from the oscillator 51 to 1 half circumference of M minutes.

Further, reference numeral 54 denotes a first switch circuit for interrupting the first carrier f ₁ output from the first frequency divider 52, and reference numeral 55 denotes a first switch circuit output from the first frequency divider 52.
The inverter 56 inverts the phase of the carrier f ₁ of the first carrier f ₁ B
In a second switch circuit.

Reference numeral 57 denotes a third switch circuit for interrupting the second carrier f ₂ output from the second frequency divider 53, and reference numeral 58 denotes a second switch circuit output from the second frequency divider 53.
The inverter 59 inverts the phase of the carrier f ₂ of the second carrier f ₂ B
Is a fourth switch circuit intermittently.

Reference numeral 60 denotes the first to fourth switch circuits 5
4, 56, 57 and 59 are switching control circuits. Reference numeral 61 denotes an adder for adding the carrier output from the first or second switch circuit 54 or 56 and the carrier output from the third or fourth switch circuit 57 or 59.

An amplifier 62 amplifies the carrier output from the adder 61 to a predetermined level. Also, 63
Is an antenna circuit for radiating a transmission signal output from the amplifier 62 into space as an electromagnetic wave.

When the communication apparatus according to the present embodiment configured as described above shifts the frequency in accordance with the transmission data, the communication apparatus inverts the frequency which has been transmitted so far and the next transmission frequency. Of the carrier.

Hereinafter, a case where the frequency is shifted from the _first carrier f ₁ to the second carrier f ₂ will be described with reference to FIG. The switching control circuit 60 includes a first
Of the switch circuit 54 of the first carrier f ₁
To the adder 61. Then, at time t in FIG.
Until zero, the contacts of the second switch circuit 56, the third switch circuit 57, and the fourth switch circuit 59 are kept open.
Therefore, in this case, only the first carrier f ₁ is led out to the adder 61, and only the first carrier f ₁ is supplied to the antenna circuit 63.

Then, at the time point t0 when the frequency is shifted, the switching control circuit 60 opens the contact of the first switch circuit 54 to stop the transmission of the first carrier f ₁ , and the third switch circuit 57 Is closed, and the second carrier f ₂ is led out to the adder 61. At the same time, the contact of the second switch circuit 56 is closed for a short period, and the first carrier f ₁ B inverted by the inverter 55 is led out to the adder 61.

As a result, in a short period immediately after the time point t0, the second carrier f ₂ and the inverted signal f ₁ B of the first carrier are input to the adder 61,
These carriers f ₂ and f ₁ B are added and superimposed in the adder 61. Then, the superimposed signal is provided to the amplifier 62 and amplified to a predetermined level, and is supplied to the antenna circuit 63.

FIG. 7 is a waveform chart for explaining the operation of each unit. FIG. 7A shows data to be transmitted, and shows an example of transmitting data of “0, 0, 1, 0, 1, 1”.

FIG. 7 (B) shows a transmission signal generated by performing switching control according to the transmission data shown in FIG. 7 (A).
When the transmitted frequency f _1, transmitting a "1" in the second
It has a frequency f ₂ to be transmitted. For example, the first frequency f ₁ is 117 kHz, the second frequency f ₂ is 125KHz is used.

As described above, in the present embodiment, when the frequency is shifted, the signal of the opposite phase to the signal of the frequency which has been transmitted so far is superimposed on the signal of the next frequency to be transmitted. I have to. In FIG. 7B, a section in which signals of opposite phases are superimposed is indicated by hatching. As shown in the figure, when the frequency is shifted, the signal having the opposite phase to the signal of the frequency that has been transmitted is superimposed, so that the amplitude of the signal becomes small immediately after the frequency is shifted.

FIG. 7C shows a waveform in the tuning circuit of the antenna circuit 107. As described above, the tuning of the antenna circuit 107 is series resonance, it is combined the resonance frequency to the first frequency f ₁ and the second intermediate frequency f _2. Therefore, as shown in FIG. 7C, the amplitude instantaneously decreases because the antenna circuit resonates in series at the boundary where the frequency of the transmission signal is changed.

In this embodiment, since the signal supplied to the antenna circuit 107 has a small signal amplitude immediately after the frequency is shifted, it is possible to cancel the output appearing due to the response delay. Yes, the resonance waveform at the transmission point is improved. This allows
As shown in FIG. 7D, at the reception point, the antenna circuit immediately resonates in parallel at the boundary where the transmission frequency is changed. As a result, the amplitude sharply increases immediately after the transmission frequency is changed.
Can be narrowed, and a frequency shift can be quickly recognized. This makes it possible to increase Q to some extent in the data carrier, so that a long communication distance can be secured.

[0060]

According to the present invention, as described above, a signal for canceling the component of the signal that has been transmitted is generated and transmitted at the timing of switching the transmission signal.
At the boundary where the transmission signal is changed, the effect of the signal that has been transmitted can be quickly canceled, and the receiving side can quickly and surely recognize the switching of the transmission signal.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an embodiment of the present invention and illustrating a main configuration of a communication device that transmits a signal using an ASK method.

FIG. 2 is a diagram showing a signal having a phase opposite to that of a signal being transmitted.

FIG. 3 is a diagram illustrating a state in which data transmission is performed between the communication device of the present embodiment and a data carrier.

FIG. 4 is a diagram illustrating operation waveforms of each unit of the communication device according to the present embodiment.

FIG. 5 is a configuration diagram illustrating a main configuration of a communication device that transmits a signal using the FSK method.

FIG. 6 is a diagram illustrating a state in which a signal having a phase opposite to that of a signal being transmitted is superimposed.

FIG. 7 is a diagram illustrating operation waveforms of each unit of the communication device according to the present embodiment.

FIG. 8 shows a conventional example, and is a configuration diagram showing a main configuration of a communication device that transmits a signal in an ASK system.

FIG. 9 is a diagram illustrating operation waveforms of each unit of the conventional ASK communication device.

FIG. 10 is a configuration diagram illustrating a conventional example and illustrating a main configuration of a communication device that transmits a signal using the FSK method.

FIG. 11 is a diagram for explaining an operation waveform of each unit of the conventional FSK communication device.

[Explanation of symbols]

 Reference Signs List 1 carrier oscillator 2 first switch circuit 3 inverter 4 second switch circuit 5 switching control circuit 6 amplifier 7 antenna circuit 10 communication device 20 data carrier

Claims (6)

[Claims] 1. A communication apparatus for switching a transmission signal in accordance with data to be transmitted, comprising: means for generating and transmitting a signal for canceling a component of a signal transmitted so far at a timing of switching the transmission signal. A communication device, comprising: 2. The transmission signal is transmitted by an ASK method,
2. The communication device according to claim 1, wherein an AM signal having a phase opposite to that of the AM signal transmitted so far is transmitted in a blank period immediately after the transmission of the signal is stopped. 3. The transmission signal is transmitted by an FSK method,
The method according to claim 1, wherein after changing the frequency of the transmission signal, a signal having a frequency opposite to that of the previously transmitted frequency is superimposed on a signal of a frequency to be transmitted next and transmitted. Communication device. 4. A communication method in which a transmission signal is switched according to data to be transmitted, wherein at the timing of switching the transmission signal, a signal for canceling a component of a signal that has been transmitted is generated and transmitted. Characteristic communication method. 5. The transmission signal is transmitted by an ASK method,
5. The communication method according to claim 4, wherein an AM signal having a phase opposite to that of the AM signal transmitted so far is transmitted in a blank period immediately after the transmission of the signal is stopped. 6. The transmission signal is transmitted by an FSK method,
5. The communication method according to claim 4, wherein after changing the frequency of the transmission signal, a signal having a phase opposite to that of the previously transmitted frequency is superimposed on a signal of the next transmission frequency and transmitted. .