JPS63134978A - Data transmission system for moving body discriminator - Google Patents

Abstract

PURPOSE:To prevent a radio interference in a state that plural tags exist simultaneously in a discriminating area, by exchanging a pre-signal to and from the tag before starting communication, and registering the communication. CONSTITUTION:It is supposed that a tag 1 enters first a discriminating area A of a discrimination circuit 3, and subsequently, a tag 2 enters. When a pre- signal from the discrimination circuit 3 is received, the tag 1 sends back a registration signal of a fact that the pre-signal has been received. The discrimination circuit 3 which has received a send-back signal sends an effective data request signal instead of the pre-signal. The tag 1 starts to send and receive usual data to and from the discrimination circuit 3. During this time, the tag 2 is in a state for waiting for reception, since the pre-signal is not received. In such a way, a radio interference which occurs due to a fact that signals are sent back simultaneously from plural tags can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a data transmission system in a mobile object identification device that uses light, electromagnetic waves, lines of magnetic force, etc. to identify tags attached to mobile objects.

[Background technology]

Mobile object identification devices that use light, electromagnetic waves, magnetic lines of force, etc.
It consists of a tag that holds data internally, and an identifier that reads the data from the tag without contact and performs an identification operation. Conventionally, in such a mobile object identification device, a one-to-l signal transmission method as shown in FIG. 5 has been adopted for data transmission between the tag and the identifier.

In other words, when the tag 1 attached to a moving object, etc. enters the identification area A using light, electromagnetic waves, magnetic field lines, etc. emitted by the identifier 3, the identifier 3 detects the tag 1's possession with respect to the tag l. The device transmits a data request signal requesting a return of the data held by the device, and in response to the data request signal, returns the data it owns. Here, discriminator 3
is constantly transmitting an effective data request signal of several bytes or more, and as shown in Figure 6, tag 1 and tag 2
There is no problem if the tags enter the identification area A during the transmission periods 1 and 2 of separate data request signals, but this transmission period is usually several lQmsec or more, and during that time two or more tags enter the identification area A at the same time. If the tag enters within A, there is a problem in that the reply signal from the tag cannot be received accurately.

[Purpose of the invention]

The present invention has been made in view of the above points, and an object of the present invention is to provide a mobile device that can eliminate interference when a plurality of tags are present in an identification area at the same time. An object of the present invention is to provide a data transmission method in an identification device.

[Disclosure of the invention]

The data transmission method in the remote identification device of the present invention includes an identifier that transmits a data request signal to identify the mobile object, receives data returned from the tag, and an identifier that stores its own data. A mobile object identification device comprising a tag installed in a mobile object and transmitting data upon receiving a data request signal from the identifier, the identifier comprising:
Normally, a preliminary signal having a shorter time width than the data request signal is transmitted, and the tag receives the preliminary signal, registers that fact, and receives a reply signal in response, and upon reception, the tag replaces the preliminary signal. The above object is achieved by transmitting a data request signal using a data request signal and communicating with a tag that has become communicable upon reception of the preliminary signal.

(Example) Hereinafter, the present invention will be explained based on the drawings as an example.

FIG. 1 is an explanatory diagram showing the overall configuration of an embodiment of the present invention, and FIG. 2 is a time chart showing the operation of this embodiment.

First, an outline of this embodiment will be explained. As shown in FIG. 2, the discriminator 3 intermittently transmits a preliminary signal that is usually about 1 bit long. In tag 1, the reception circuit described below allows
The prior signal is identified and a signal of about 1 bit registered to that effect is sent back.

The discriminator 3 that has received this reply signal transmits an effective data request signal in place of the preliminary signal.

The tag 1 is set in a state where it can effectively communicate data by receiving the advance signal, and the identifier 3 and the tag 1 perform effective communication.

Next, this embodiment will be explained in detail. Now, assume that tag 1 enters identification area A at time α, and tag 2 subsequently enters at time β for a short time (but longer than the length of the prior signal).

First, the tag 1 receives a preliminary signal from the discriminator 3, and returns a signal of about 1 bit that registers the fact that the preliminary signal has been received, and the discriminator 3 receives the reply signal. transmits an effective data request signal in place of the advance signal. The tag 1 is set to a state in which effective data communication is possible by receiving the preliminary signal, and the identifier 3 and the tag 1 start effective communication, that is, normal data transmission and reception. During this time, the identifier 3 does not transmit the preliminary signal, so the tag 2 is within the identification area A, but does not receive the preliminary signal and is in a reception waiting state.

The tag 2 continues to wait for reception until the communication between the identifier 3 and the tag 1 is completed and the pre-signal to be transmitted again is received. After receiving the advance signal, the same communication as that between the identifier 3 and the tag 1 described above is performed. Further, the tag l immediately after completing the communication is set not to receive the preliminary signal for a certain period of time so as not to receive the preliminary signal again. Therefore, for a priori signal with a short time width of about 1 bit,
As long as a plurality of tags do not enter the identification area A at a time interval shorter than the time width, there is no interference caused by simultaneous return signals from a plurality of tags, and accurate communication is possible.

FIGS. 3 and 4 show examples of the receiving section of the tag.

FIG. 3 is an example of the case where the prior signal is identified by software, and the demodulator 4 removes the carrier wave component from the modulated signal.
and the signal component data “O” extracted by the demodulator 4
A comparator 5 that compares the outputs of the filter circuits f, , f, which take out two frequencies corresponding to "1" and "1", and outputs an FSK demodulated output, and a serial circuit that processes the outputs. It consists of a communication interface 6 and a CPU 7, and the FSX demodulation output is directly input to the CPU 7, and the CPU 7 identifies the prior signal based on the time width of the received signal.

FIG. 4 is an example of hardware-based identification of the prior signal.
Using a frequency different from the two frequencies corresponding to "O" and "I", a filter circuit f3 is separately provided to extract the frequency component from the output of the demodulator 4 in FIG. Identify signals.

〔Effect of the invention〕

As described above, the data transmission method in the remote identification device of the present invention includes an identifier that transmits a data request signal for identifying the mobile object, receives data returned from the tag, and a self-identifier. and a tag that is installed in a mobile body and that transmits the data when it receives a data request signal from the identifier, the identifier usually has a tag that stores data from the data request signal. A preliminary signal with a short time width is transmitted, and the tag receives the preliminary signal, registers it, and receives a reply message 3, which sends a data request signal in place of the preliminary signal. Since the tag is transmitted and the tag is enabled to communicate upon reception of the prior signal, the tag can be identified even when multiple tags are present in the identification area at the same time. Thus, a data transmission method for a remote identification device can be provided.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the overall configuration of an embodiment of the present invention. FIG. 2 is a time chart explaining the operation of the same as above. FIG. 3 is a block diagram showing the receiving section of the tag. , a block diagram showing another example of the above, FIG. 5 is an explanatory diagram showing the overall configuration of the conventional example, and FIG. 6 is a time chart explaining the operation of the above 1.2-Tag, 3-Discriminator Patent Applicant Matsushita Electric Works Co., Ltd. Agent Patent Attorney Toshimaru Takemoto (and 2 others) Figure 1 Figure 3 Figure 5

Claims (1)

[Claims] (1) An identifier that transmits a data request signal for identifying the mobile object and receives data returned from the tag, and an identifier that is installed in the mobile object and has its own data. and a tag that transmits the data upon receiving a data request signal from the identifier, the identifier usually transmits a preliminary signal having a shorter time width than the data request signal, and the tag transmits the data in advance. A tag that receives a signal, registers a reply signal to that effect, and sends a data request signal in place of the prior signal, and becomes ready for communication by receiving the prior signal. 1. A data transmission method in a mobile object identification device, characterized in that it communicates with a mobile object identification device.