JPH09162776A - Reflection type communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power consumption of hand set in simple configuration by radiating the signals of different amplitudes from a base unit during transmission and reception periods, detecting the envelopes of signals radiated from the base unit at the hand set and preventing the operation of hand set from getting adverse due to a temperature change. SOLUTION: When a hand set 10 is located at the place where the signal transmitted from the base unit can not be received, the operating voltage of each circuit part at the hand set 10 is controlled by a power source control circuit 20, and the operating voltage is supplied only to a carrier wave detection circuit 30 for detecting the envelopes of carrier wave signals from the base unit. Therefore, when the hand set 10 can not be used, power consumption is limited to a minimum. In such a standby mode, the envelopes of carrier wave signals are detected among the signals transmitted from the base unit by a diode 13 for both detection and modulation, the level of envelop signal is compared with a reference voltage through a filter circuit 17 by a level detection circuit 19, a LOW signal is outputted to the power source control circuit 20, and the standby mode is maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective communication system used for ID tags, room entrance / exit management systems, and the like.

[0002]

2. Description of the Related Art Conventionally, a reflection type communication system using a small transponder has been used in an ID tag, a toll road charge system, an entrance / exit management system, or the like. In such a communication system, for example, an inquiry signal is transmitted from the master unit to the slave unit, and the slave unit which has received the inquiry signal transmits information related thereto as a response signal. With this, the parent device can recognize information such as which one of the plurality of child devices the child device is, or what state the child device is in. A signal for changing the status information held inside the slave unit is transmitted as necessary. Taking a toll road toll collection system as an example, the parent machine recognizes the prepaid balance stored in the child machine from the response from the child machine,
After that, it operates to transmit a command to the slave unit to change the balance in the slave unit to a reduced value. Further, such a system is also used for opening and closing doors and managing locks when entering and exiting a building.

For such a reflection type communication system, a system using an induction magnetic field in the long wave band has been conventionally known.
Along with technological advances in recent years, methods that employ radiated electromagnetic fields in the SHF band have come to be used (see “MICROWAV
E JOURNAL "Jan.1995 pp.64-78). FIG. 4 shows an example of the configuration of a slave unit in a reflection type communication system using such a radiation electromagnetic field in the SHF band. In this figure, 1
Reference numeral 01 is an antenna, 102 is a diode, and 103 is a digital signal source for generating a digital signal unique to the slave unit.

In the child device thus constructed, a signal of frequency f is emitted as an inquiry signal from the parent device (not shown), and this signal is received by the antenna 101 of the child device. In this slave unit, since the digital signal from the digital signal source 103 is applied to the diode 102, the conduction / non-conduction state of the diode 102 is switched according to the digital signal. Depending on whether the diode 102 is conducting or non-conducting, the antenna 101
Since the matching state is changed, the signal of the frequency f received from the base unit is reflected a lot when the antenna 101 is in the mismatching state and only a little when the antenna 101 is in the matching state. Therefore, a digital signal (ID) unique to the slave unit is output from the antenna 101 of the slave unit.
Thus, the signal of the frequency f amplitude-modulated is reflected. The base unit side can recognize the ID of the slave unit by detecting the reflected signal.

In this conventional example, a response signal such as ID data is transmitted from the slave unit to a question signal from the master unit, but data such as command data is transmitted from the master unit to the slave unit. Reflective communication systems have also been proposed which are also possible. An example of such a reflective communication system will be described with reference to FIG. This figure shows an example of the configuration of a slave unit in such a reflection type communication system. 111 is an antenna and 112 is a high frequency switch, which is similar to the diode 102 shown in FIG. 4, for example. . Reference numeral 113 is A using a Schottky diode or the like
M detector, 114 is a decoding circuit, and 115 is a processing circuit, which is composed of, for example, a sequential circuit or a microcomputer. 116 is FSK (frequency shift ke
ying) encoder 117 is a drive circuit of the high frequency switch 112. Reference numeral 118 denotes the antenna 111 when the high frequency switch 112 is switched to the circuit 118 side.
Is a mismatch circuit for bringing the circuit into a mismatched state, for example, a circuit for simply releasing it.

In this reflection type communication system, when data is transmitted from a master unit (not shown) to a slave unit, ASK is performed by a data signal to be transmitted from the master unit to the slave unit.
(Amplitude shift keying) When a signal of modulated frequency f is transmitted, while the master unit receives data from the slave unit, only the carrier wave signal of frequency f that is not modulated from the master unit to the slave unit is transmitted. It is designed to be sent.

On the other hand, in the slave unit, the ASK-modulated signal of frequency f transmitted from the master unit (not shown) is received by the antenna 111, and is guided to the AM detector 113 through the high frequency switch 112. AM detector 113
At, the received signal is AM-detected, and the decoding circuit 114
The data signal that has been decoded and transmitted from the master unit is reproduced. This signal is input to the processing circuit 115, the processing corresponding to the command data is executed in the processing circuit 115, or a response signal to that is generated.

When the master unit receives data from the slave unit, the master unit transmits only the unmodulated carrier signal to the slave unit. At this time, the response signal created by the processing circuit 115 is input to the FSK encoder 116, and the FSK encoder 116 generates a pulse signal having a different frequency corresponding to "0" or "1" of the response signal. It The FSK-encoded response signal output from the FSK encoder 116 is the drive circuit 1
High frequency switch circuit 1
12 is driven.

When the high frequency switch circuit 112 is on the side of the mismatch circuit 118, the antenna 111 is in a mismatching state, and the signal transmitted from the master unit is reflected with a large reflectance. On the other hand, the high frequency switch circuit 112 is
When connected to the M detector 113 side, the antenna 1
11 is in the matching state, and the reflectance of the signal transmitted from the parent device is low. Therefore, the high-frequency switching circuit 112 is driven by the drive signals of different frequencies corresponding to “0” and “1” of the response signal created in the processing circuit 115, and the reflection from the antenna 111 whose amplitude changes at different frequencies. Waves are emitted. In the master unit (not shown), the reflected wave is amplitude-detected, FM demodulated, and then decoded to reproduce the response signal created in the slave unit.

By the way, the child device of such a reflection type communication system is generally miniaturized in some cases, for example, as a card because it is carried by a person or installed in a moving article. . Since a large-capacity battery power source cannot be installed in a child device of such a miniaturized reflection type communication system, it is consumed by being placed in a standby mode or an operating mode depending on its usage state. It is controlled to reduce power consumption.

For example, the level of a carrier signal of an unmodulated frequency f transmitted from the master unit to the slave unit is detected, and when the level of this carrier signal is a predetermined value or more, that is, reflected by the slave unit. , If the slave unit determines that the level of the carrier signal to be detected by the master unit is a level that can be received by the master unit, the slave unit is within an area where communication with the master unit is possible. Recognizing that, the operating voltage is supplied to each circuit unit, the interrogation signal transmitted from the parent device is received, and the operation mode in which information related to the interrogation signal is created as a response signal is set.

On the other hand, when the level of the carrier signal of the unmodulated frequency f transmitted from the master unit to the slave unit is detected and the level of this carrier signal is below a predetermined value, that is, the slave unit is the master unit. When recognizing that it is not within the area where communication with the slave unit is possible, the slave unit enters a standby mode in which the operating voltage is supplied only to the carrier wave detection circuit that detects the level of the carrier wave signal transmitted from the master unit.

That is, in the reflection type communication system, the carrier detection circuit of the slave unit detects the level of the carrier signal transmitted from the master unit, and the use mode of the slave unit is set to the operation mode or the detection mode of the carrier signal. Change to standby mode,
The power consumption of the child device is reduced.

[0014]

In the reflection type communication system as described above, in order to detect the carrier wave signal transmitted from the master unit in the slave unit, the carrier wave is detected by the diode provided in the AM detection circuit. A method of directly detecting the level of the signal or applying a bias current to the diode of the AM detection circuit to detect a change in the AC component obtained by modulating the bias current by the carrier signal is used.

However, when the level of the carrier signal output from the base unit is directly detected by using the diode of the AM detection circuit, the forward voltage of the diode changes due to the temperature change, so that the carrier signal detected by the diode changes. There is a problem in that the level changes, and the detection accuracy and detection sensitivity deteriorate due to temperature changes. For this reason, it is necessary to add a circuit for increasing the detection sensitivity of the diode as a whole, which causes a problem that the number of parts increases and the current consumption of the slave unit increases.

Further, when detecting a change in the AC component obtained by modulating the bias current flowing through the diode of the AM detection circuit, it is necessary to add a new modulation circuit, the number of parts increases, and the slave unit also remains. There is a problem that the current consumption of the device increases.

In order to solve such problems, it is an object of the present invention to provide a reflection type communication system in which the current consumption of the slave unit is reduced.

[0018]

In order to achieve the above object, the base unit of the reflection type communication system of the present invention has a transmission period for transmitting an inquiry signal to a handset and a response signal from the handset. It has amplitude control means for controlling the amplitude of the carrier wave differently depending on the reception period, and the slave unit has detection means for detecting the envelope of the signal radiated from the master unit, and is output from the detection means. The operation of the slave unit is controlled by the detection signal.

According to the present invention, the master unit radiates signals having different amplitudes in the transmission period and the reception period, and the slave unit detects the envelope of the signal radiated from the parent unit, so that the temperature change It is possible to reduce the fluctuation of the detection signal due to.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION A reflective communication system which is an embodiment of the present invention will be described below. FIG. 1 shows an example of a block diagram of a base unit of a reflection type communication system according to the present embodiment. In the base unit 1 shown in this figure, 2 is a processing device for performing predetermined data processing in the reflection type communication system, and 3 is a carrier wave generator, for example, an oscillator that oscillates a high-frequency signal in the 5.8 GHz band. Reference numeral 4 denotes an amplitude control circuit, which controls the amplitude level of the carrier signal output from the carrier generator 3 in a transmission period in which a master device transmits a data signal to a slave device and a reception period in which data is received from the slave device. Control. Reference numeral 5 is an ASK modulator for ASK modulating the carrier signal generated by the carrier generator 3 with the data signal output from the processing device 2. A circulator 6 outputs a signal input from the ASK modulator 5 to the antenna 7 and
It operates so as to output the signal input from the AM detection circuit 8. Reference numeral 7 is an antenna, and 8 is an AM detection circuit. Reference numeral 9 denotes an FM detection circuit, which is composed of an amplifier, a limiter and an FM detection device, FM-detects the output signal AM-detected by the AM detection circuit 8 and reproduces a reception data signal,
It is output to the processing device 2.

Next, FIG. 2 shows an example of a block diagram of a slave unit of the reflection type communication system according to the present embodiment. In the slave unit 10 shown in this figure, 11 is a signal processing circuit built in the slave unit 10, and is composed of, for example, a memory circuit and a sequential circuit, or a microcomputer.
12 is, for example, a VCO (Voltage Controlled Oscillato)
r: voltage-controlled oscillator) and the like,
It oscillates signals of different frequencies according to the transmission data transmitted from the master unit 1 shown in FIG. Reference numeral 13 denotes a diode for both detection and modulation, which is connected to the antenna 14 similarly to the diode 102 shown in FIG. 4, and performs AM detection on the reception signal input from the antenna 14 and
The impedance of the antenna 14 is changed according to the FSK signal output from the FSK modulator 12. Reference numeral 15 is a filter circuit including, for example, a high-pass filter, and 16 is a decoding circuit. The data signal which is AM-detected by the detection / modulation diode 13 and is input through the filter circuit 15 is output to the signal processing circuit 11. To do.

The carrier wave detection circuit 30 shown by the broken line is a filter circuit 17, an AC amplification circuit 18, and a level detection circuit 19.
And a power supply control circuit 20, which detects the envelope of the carrier wave of the transmission signal transmitted from the base unit 1,
Control is performed to switch the use mode of the child device 10 to the standby mode or the operation mode. The filter circuit 17 is a filter circuit including, for example, a low-pass filter, and filters the envelope signal of the carrier wave detected by the detection / modulation diode 13. The AC amplifier circuit 18 amplifies the AC component of the envelope signal input via the filter circuit 17. The level detection circuit 19 is composed of, for example, a comparator, and compares the signal of the AC component of the envelope signal amplified by the AC amplification circuit 18 with the reference voltage V _ref, and, for example, "High" or "Low" depending on the comparison result. Output the detection signal of. The reference voltage V _ref is set to a voltage that is not affected by temperature changes. The power supply control circuit 20 controls the operating voltage supplied to each circuit unit based on the detection signal output from the level detection circuit 19, and sets the use mode of the handset 10 to the standby mode or the operation mode. Switching control is performed.

Hereinafter, the base unit 1 and the handset 10 of the reflection type communication system according to the embodiment of the present invention configured as described above
The operation will be described with reference to the signal waveforms shown in FIG. First, the operation of base unit 1 will be described. When transmitting data from the base unit 1 to the handset 10, a signal having a frequency ASK-modulated by the data signal to be transmitted to the handset 10 is transmitted. On the other hand, when the master device 1 receives the data from the slave device 10, the master device 1 transmits to the slave device 10 a carrier signal having a frequency that is not modulated.

Further, in the present embodiment, the transmission power transmitted from the master unit 1, that is, the amplitude level of the carrier signal transmitted from the master unit 1 as shown in FIG.
From the slave unit 10 to a data signal and a reception period in which the master unit 1 transmits a carrier signal to receive the data from the slave unit 10 by changing the amplitude level of the carrier signal. To do. In this case, the amplitude level of the carrier signal is changed in a single change or in a specific time pattern.

Next, the operation of the handset 10 will be described.
First, it is assumed that the child device 10 is outside the area of the parent device 1, that is, in a place where the transmission signal transmitted from the parent device 1 cannot be received. In this case, the power supply control circuit 20 controls the operating voltage of each circuit unit of the slave device 10, and the carrier wave detection circuit 30 that detects the envelope of the carrier wave signal from the master device 1.
The operating voltage is supplied only to the slave unit 10, and the standby mode is set so that the power consumption of the slave unit 10 is limited to the minimum.

In the standby mode, the detection / modulation diode 13 detects the envelope of the carrier signal in the transmission signal transmitted from the master unit 1. At this time, the detection / modulation diode 13 is used. A predetermined bias voltage for detecting the envelope is applied to.
In this case, the envelope signal of the carrier wave received by the antenna 14 and detected by the detection / modulation diode 13 is input to the AC amplification circuit 18 via the filter circuit 17, and the AC amplification circuit 18 converts the AC signal of the envelope signal. Only the component is amplified and input to the level detection circuit 19. Level detection circuit 1
In 9, a level of the amplified envelope signal with an AC amplifier 18, a reference voltage V _ref are compared, if the level of the envelope signal is less than or equal to a reference voltage V _ref, the power supply control circuit 20, for example, " The detection signal of "Low" is output, and the slave unit 10 is maintained in the standby mode.

Here, when the slave unit 10 moves within the area of the master unit 1, that is, to a place where the transmission signal transmitted from the master unit 1 can be received, it is received by the antenna 14 and the diode for both detection and modulation is used. In the envelope signal of the carrier wave detected in 13, only the AC component is amplified in the AC amplification circuit 18, and in the level detection circuit 19, the level of the amplified envelope signal is compared with the reference voltage V _ref . Then, for example, if the level of the envelope signal is equal to or higher than the reference voltage V _ref as shown in FIG. 3B, the level detection circuit 19
For example, the detection signal of "High" is the power control 20
Is output to In this case, the power supply control circuit 20
Supplies an operating voltage to each circuit section of the child device 10 and
Will shift from the standby mode to the operating mode.

In such an operation mode, the detection / modulation diode 13 detects the data signal transmitted from the master unit 1, and at this time, the detection / modulation diode 13 detects the data signal. A predetermined bias voltage will be applied. In this case, the data signal received by the antenna 14 and detected by the detection / modulation diode 13 is passed through the filter circuit 15 and the decoding circuit 16.
And the data signal is decoded in the decoding circuit 16. The decoded data signal is input to the signal processing circuit 11, and in the signal processing circuit 11, the master unit 1
The processing corresponding to the data signal transmitted from
A response signal to that will be created. In addition,
In the operation mode as well, the detection circuit 30 detects the envelope signal of the carrier wave of the master device 1, and when the slave device 10 goes out of the area of the master device 1, the operation mode shifts to the standby mode.

As described above, in the reflection type communication system according to the embodiment of the present invention, the transmission period for transmitting the transmission power transmitted from the base unit 1 to the handset 10 and the base unit 1 changes with the reception period in which the carrier signal is transmitted to receive the data signal from the slave unit 10, and the slave unit 10 detects the envelope signal of the carrier wave transmitted from the master unit 1 to detect the envelope. Since only the AC component of the line signal is amplified, even if the forward voltage of the detection / modulation diode 13 changes due to temperature change or the like, the AC component of the envelope signal should reduce the influence of temperature characteristics. You can Therefore, it is possible to control the use mode of the slave unit with a simple circuit configuration without adding a circuit for improving the detection sensitivity as in the conventional case or newly providing a modulation circuit. The current consumption of the child device can be reduced.

In the present embodiment, the transmission power transmitted from the base unit 1 is such that when the reception sensitivities of the base unit 1 and the handset 10 are about the same, the handset 10 receives the data signal from the base unit 1. On the other hand, when the master device 1 receives the data signal from the slave device 10, the amplitude level of the carrier signal becomes smaller, so that the transmission power during the reception period when the master device 1 receives the data from the slave device 10 is increased. The case has been described, but the present invention is not limited to this, and for example, the base unit 1 supplies electric power during a period in which a data signal is transmitted from the base unit 1 to the handset 10.
It may be larger than the power during the period of receiving the data signal from 0.

[0031]

As described above, in the reflection type communication system of the present invention, the master unit is provided with the amplitude control means for outputting signals having different amplitude levels in the transmission period and the reception period, and the master unit is provided with the amplitude control unit. A detection circuit is provided to detect the envelope of the signal radiated from the machine to prevent the operation of the child machine from deteriorating due to temperature changes. It is possible to realize a slave unit with reduced power consumption with a simple circuit configuration, without the need to provide.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a master unit of a reflection type communication system of the present invention.

FIG. 2 is a block diagram showing a configuration example of a slave unit of the reflection type communication system of the present invention.

FIG. 3 is a diagram showing an example of a waveform of each signal in the reflective communication system of the present invention.

FIG. 4 is a diagram showing a configuration example of a conventional reflective communication system.

FIG. 5 is a diagram showing another configuration example of a conventional reflective communication system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 base unit 2 processor 3 carrier wave generator 4 amplitude control circuit 5 ASK modulator 6 circulator 7, 14 antenna 8 AM detector 9 FM detector circuit 10 slave unit 11 signal processing circuit 12 FSK modulator 13 diode for detection and modulation 15 17 Filter Circuit 16 Decoding Circuit 18 AC Amplifier Circuit 19 Level Detection Circuit 20 Power Supply Control Circuit 30 Detection Circuit

Claims (1)

[Claims] 1. A master unit and a slave unit, wherein the master unit modulates a carrier wave to transmit an inquiry signal, and the slave unit modulates and reflects a signal radiated from the master unit. In the reflection type communication system adapted to transmit information, the master unit has a transmission period for transmitting an inquiry signal to the slave unit, and a reception period for receiving a response signal from the slave unit, and the carrier wave. Amplitude control means for controlling the amplitude of the signal to be different, the slave unit has a detection unit for detecting an envelope of a signal radiated from the master unit, and a detection signal output from the detection unit is used. A reflection type communication system configured to control the operation of the slave.