JPH01182782A - Reflection type transmitter - Google Patents

Abstract

PURPOSE:To achieve a lower power by varying an impedance of an antenna by a transmission data to change reflection characteristic of the antenna corresponding to the transmission data. CONSTITUTION:As an address counter 6 counts a clock signal ck each time being inputted to specify the subsequent address, a data written in a memory 7 is read out in succession. The data read out is applied to a gate electrode of an FET 8 as a series of identification code ID to the FET 8 perform an ON or OFF switching according to the code ID. In response to the ON or OFF action of the FET 8, an impedance changes between terminals 2b and 2c (between feeding points 4a and 4b). When the FET 8 switches ON, a dipole antenna 4 matches a transmitted wave, and the matching of the antenna 4 is broken when it 8 does OFF. In this manner, the matching of the antenna 4 corresponds to the ON or OFF action of the FET 8 and the ON or OFF action of the FET 8 is effected to the code ID. This enables detection of the code ID in a communicator thereby eliminating the need for providing any transmitting circuit and a power source for transmission.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reflective transmitter, and is particularly suitable for use in a transmitter used in an identification system using microwaves.

[Summary of the invention]

This is a reflection-type transmitting device that uses low power and is miniaturized by changing the impedance of the antenna depending on the data to be transmitted, modulating the incident radio wave, and re-radiating it as a reflected wave.

[Conventional technology]

2. Description of the Related Art Systems have been put into practical use in which a recognition device (communicator) receives radio waves from a transmitting device to recognize an article or check people entering and leaving a gate. The transmitting device used in such a system is shaped like a tag or a card, and a reflective or active transmitting device is used.

A reflective transmitter is a device in which an antenna for reflecting radio waves is provided on the main body of the transmitter, and the radio waves transmitted from the recognition device are reflected by the antenna and sent back to the recognition device (for example, Japanese Patent Publication No. 57-24598). .

On the other hand, active transmitting devices are equipped with a data generation circuit, a transmitting circuit for transmitting data, a receiving circuit for receiving radio waves transmitted from the recognition device, etc., and respond in response to the radio waves from the recognition device. It is now possible to send data for recognition.

[Problem to be solved by the invention]

A reflective transmitter has a simple structure and can be made small and inexpensive, but cannot transmit data. For this reason,
For example, it could not be used in cases where advanced recognition was required, such as in logistics management systems implemented for parcel delivery services and air cargo flights.

On the other hand, active transmitters can transmit data, but require a transmitter circuit, a receiver circuit, and a power source for these circuits.

An object of the present invention is to reduce the size of a transmitting device capable of transmitting thought data that addresses the above-mentioned problem, and to enable it to be manufactured at low cost.

[Means to solve the problem]

The reflective transmitter of the present invention has an incident continuous wave radio wave 11.
an antenna 4 that reflects the transmission data, a transmission data generation circuit 9, and an impedance change circuit (FET) that changes the impedance of the antenna 4 in response to the transmission data.
I-run transistor 8 or diode D).

[Operation] Data is transmitted by utilizing the fact that the reflection characteristics of the antenna 4 change according to changes in the impedance of the antenna. An antenna reflected wave 14 as a radio wave for carrying data
21, there is no need to provide a transmitting circuit for generating a carrier wave or a transmitting power source.

〔Example〕

FIG. 1 is a configuration diagram of a reflection type transmitter showing an embodiment of the present invention. This transmitting device is configured as an ID tag device. The tag body l is made of synthetic resin, for example, and is formed into a thin, milk-like shape, and has a dipole antenna 4 printed and wired on a flexible substrate, etc., as shown in the plan view of Fig. 2.
is provided on the surface. Further, an identification code generator 2 for forming transmission data and a battery 3 serving as a power source for driving the identification code generator 2 are buried inside.

The identification code generator 2 includes an oscillator 5 and an address counter 6.
, memory 7, FET) transistor 8 are integrated into one chip IC, and power consumption is extremely low.

The memory 7 is, for example, a writable ROM (CPROM), and data to be sent from the ID tag device is written therein. In other words, for example, when an ID tag device is used in a logistics system, data such as the type of package, reception number, names of recipient and sender, and destination are encoded (digitized).
has been written.

The positive and negative electrodes of the battery 3 are directly connected to terminals 2a and 2b provided on the identification code generator 2, respectively, and the identification code generator 2 is always in operation. Therefore, the data generation circuit 9 consisting of the oscillator 5, address counter 6, and memory 7 is always operating, and the clock signal ck of a predetermined frequency is always derived from the oscillator 5 to the address counter 6.

Address counter 6 specifies an address in memory 7, and data written at the specified address is read out. Since the address counter 6 counts up and specifies the next address every time the clock signal ck is applied,
The data written in the memory 7 is read out one after another. The read data is applied to the gate electrode of the FET transistor 8 as a series of identification codes ID consisting of digital signals. Therefore, the potential of the gate electrode changes to a high potential or a low potential depending on the contents (data) of the identification code ID, so that the transistor 8 performs an on/off operation depending on the identification code ID.

The transistor 8 has a source electrode grounded and a drain electrode connected to the terminal 2C of the identification code generator 2. Therefore, as the transistor 8 turns on/off, the impedance between the terminals 2b and 20 changes. Feeding points 4a and 4b of the antenna 4 are connected to these terminals 2b and 2C.

As shown in the system block diagram of FIG. 3, when a microwave band continuous wave transmission wave 11 radiated from a communicator 12, which is an identification device, is received, a voltage is induced in the dipole antenna 4, and a received current ■ flows. Therefore, the received radio wave, that is, the transmission wave 11 radiated from the communicator 1O, is re-radiated from the dipole antenna 4. The communicator 10 receives the re-radiated radio waves, that is, the reflected waves 14 from the dipole antenna 4 with the receiving antenna 13 and demodulates them.

The impedance between the terminals 2b and 20 (between the feeding points 4a and 4b) changes depending on whether the transistor 8 is turned on or off.

When the transistor 8 is turned on, the impedance between the feed points 4a and 4b becomes, for example, 50 [Ω], and the dipole antenna 4 is matched with the transmission wave 11 of 2.45 GH2. Furthermore, when the transistor 8 is turned off, the impedance of the feed points 4a and 4b is, for example, 100 [Ω].
As a result, the matching of the dipole antenna 4 is disrupted. When matching is achieved and when matching is not achieved, 1. The reflection characteristics of the dipole antenna 4 are different. For this reason, there is a difference in phase and amplitude between the reflected waves 14 when they are matched and the reflected waves when they are not matched. That is, this ID tag device turns on/off the transistor 8 to modulate the phase (or amplitude) of the received radio wave (transmitted wave 11 from the communicator 10) and reflects it to the communicator 10. Become.

Therefore, data can be received by receiving the composite wave of the reflected wave 14 and the transmitted wave 11 in the communicator 10 and demodulating the phase or amplitude.

As described above, the matching state of the dipole antenna 4 corresponds to the on/off of the transistor 8, and the on/off of the transistor 8 corresponds to the identification code ID, so the identification code ID can be detected by the communicator 10. becomes. Therefore, there is no need to create a carrier wave (carrier) for transmitting the identification code ID to the communicator 10 using the ID tag device, so there is no need to provide a transmitting circuit and a power source for transmitting. Also, the transmitted wave 1 from the communicator
1 is received, the reflected wave 14 is automatically generated, so there is no need for a receiving circuit and a receiving power source for sending the identification code ID in response to the transmitted wave 11 from the communicator IO.

Therefore, since only the identification code generator 2 consumes power, the power consumption is extremely small, for example, 1 μA. Therefore, it can be operated continuously for about one year using a button battery with a small capacity of about 10 mA/h.

This ID tag device can be used in various fields by changing the data written to the memory 7. For example, if data about people is written, it can be applied to a system for managing people entering and exiting at gates. In this case, tag body 1
It is best to form it into a card shape.

Note that other antennas, such as a microstrip antenna, may be used instead of the dipole antenna 4.

FIG. 4 is a circuit diagram of a main part of a reflection type transmitter showing another embodiment. In this transmitting device, a series circuit consisting of a diode D and a capacitor CI is connected between feeding points 4a and 4b of a dipole antenna 4, and these connection points are connected to a terminal 2a of an identification code generator 2. It is. Also, the other terminal (feeding point 4b) of the capacitor C1 is connected to the terminal 2b.

Communicator 10 received by dipole antenna 4
The transmitted wave 11 from the diode D is multiplied by the square characteristic of the diode D, and the second harmonic of the transmitted wave 11 is reflected as a reflected wave 21.
Re-radiated from the D-tag device. In this example, a transmitting dipole antenna 20 that resonates with the second harmonic is provided, and feed points 20a and 20b of this antenna 20 are connected to feed points 4a and 4b of the dipole antenna 4, respectively, to efficiently regenerate the second harmonic. It's radiating.

On the other hand, the transmitted wave 11 from the communicator 10 received by the dipole antenna 4 is rectified by the diode D and stored in the capacitor C1. Therefore, a voltage is generated across the capacitor CI as indicated by arrow A, and this voltage is applied to the identification code generator 2 via the terminal 2a12b. The voltage generated at the arrow A portion varies depending on the electric field strength at the receiving point, but is usually several mV to several V, so that the identification code generator 2 can be operated sufficiently.

In this example, as shown in the block diagram of the data generation circuit 9 in FIG. 5, data is stored in a shift register 22 having a plurality of flip-flops FF connected in series. This shift register 22 is configured as a serial input serial output type, and data (consisting of 0 and l) is output one bit at a time from the flip-flop FFn provided at the final stage, and the identification code 10 is output from the terminal 2c (output terminal)
given to. Also, the output from the final stage flip-flop FFn is transferred to the first stage flip-flop FF.

The data is re-entered and generated in a circular manner.

The identification code ID given to terminal 2C is the capacitor C.
2 and to the anode of diode D through coil L1. Therefore, the diode D conducts or disconnects the feed points 20a (4a) and 20b (4b) depending on the identification code ID, so the transmitting dipole antenna 2
The impedance of 0 is the identification code 1. It changes depending on D. Therefore, since the state (phase, amplitude, etc.) of the reflected wave 21 re-radiated from the transmitting antenna 20 changes depending on the identification code ID, the reflected wave 21 is received and demodulated by the communicator IO, and the data Generated data of the generating circuit 9 can be obtained.

Note that the coil L1 is a high frequency choke coil, and prevents the received wave 11 from flowing to the terminal 2C.

Further, a capacitor C3 is connected between the connection point of the capacitor C2 and the coil L and the ground to ground the data output line in a high frequency manner so that the received wave 11 does not flow to the terminal 2c.

Next, the block diagram of FIG. 6 shows an example of a system that can distinguish and identify reflected waves from a plurality of ID tag devices. As mentioned above, data is transmitted using the reflected waves of the radio waves transmitted from the communicator, so if there are multiple ID tag devices within the range that can respond to the communicator, these ID tags Reflections from the device simultaneously enter the communicator, causing interference.

In the example shown in FIG. 6, a sawtooth wave voltage is applied to the voltage controlled oscillator (VCO) 26 to generate a ramp-shaped FM wave having a frequency of ω0+Δωot, which is transmitted from the transmitting antenna 12. The FM transmission wave 28 is received by the ID tag device, and the reflected wave 29 is transmitted to the receiving antenna 13 of the communicator 31.
If the time until the signal returns to Δτ is Δτ, the receiving frequency at time t is ω0+Δωo (t−Δτ). The received wave 29 and the transmitted wave 28 are applied to a mixer 27 to obtain an output signal having a frequency Δω0 and Δτ which is the difference between the two, and this signal is applied to a frequency demodulator 30. Depending on the distance between the communicator 31 and the ID tag device, the time Δτ for reflection from the ID tag device to return changes.
The difference frequency Δω0·Δτ is a frequency corresponding to the distance from the communicator 31 to each ID tag device. Therefore, even if there are multiple ID tag devices, the communicator 31
If the distance from
By differentiating Δτ, reflected waves that are incident simultaneously can be separated, and an output obtained by demodulating the reflected waves from the ID tag device at a specific position (Δτ is a predetermined value) can be obtained from the demodulator 30. Therefore, by phase demodulating this output, for example, it is possible to reproduce the data sent from the ID tag device.

〔Effect of the invention〕

As described above, according to the present invention, the impedance of the antenna is changed according to the transmission data, and the reflection characteristics of the antenna are changed in accordance with the transmission data, so that the transmission data can be carried on the reflected wave and sent. Therefore, it is possible to eliminate the need for a transmission circuit that generates a carrier wave and sends data, and a transmission power supply. Therefore, a data transmitting device that operates with extremely low power can be manufactured with a simple circuit configuration, small size, and at low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a reflective transmitting device showing an embodiment of the present invention, FIG. 2 is a plan view of an ID tag device, FIG. 3 is a block diagram of a data transmission/reception system, and FIG. 4 is a diagram similar to the one shown in FIG. FIG. 5 is a block diagram of a data generation circuit using a shift register, and FIG. 6 is a block diagram of a transmitting/receiving system using a plurality of transmitting devices. In addition, in the symbols used in the drawings, 2-・-1111--Identification code generator 4
−−−−−−−−−・・・−・−Dipole antenna 8
−・−・−・−−−1−−−・FET) Transistor 9・−1−−−−−−−−・−Data generation circuit 10−・
・−・−・−・・−１−−−〜Communicator 1)−−
−−・−・・−・Transmitted wave 14−−−−−・−−1−−−Reflected wave 21−・・
・−・−−−−−−−One reflected wave.

Claims (1)

[Claims] A reflection type transmitting device comprising an antenna that reflects incident continuous wave radio waves, a transmission data generation circuit, and an impedance changing circuit that changes the impedance of the antenna in response to the transmission data.