JPH08340287A - Non-contact identification code reader - Google Patents

Abstract

PURPOSE: To excellently receive an intrinsic identification code transmitted from a non-contact identification tag by radio at all times even when the S/N of a communication path is deteriorated. CONSTITUTION: This non-contact identification code reader 1a sends out a signal with frequency fC generated by a local oscillator 13 through a supply radio wave output circuit 12 and a transmission antenna circuit 11 as a carrier frequency fC for transmission. The noncontact identification tag 2 modulates the fC in a modulation circuit 25 by the frequencies f1 and f0 for which the intrinsic identification codes written in a memory 23 by a logic circuit 24 based on the carrier frequency fC received through a tuning circuit 21 and an interface circuit 22 are allocated to the '1' and '0' of read codes and sends out the signals of two bands which are the HSB of fC+f1 and fC+f0 and the LSB of fC-f1 and fC-f0 . The reception antenna circuit 17 of the non-contact identification code reader 1a switches switches S1 and S2 for changeover corresponding to the S/N of the communication path, receives the HSB or the LSB and sends it out to a mixer circuit 15 and the intrinsic identification code is demodulated in a demodulation circuit 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contactless identification code reader, and more particularly, to a unique identification code of a contactless identification tag for storing a unique identification code given in advance and providing the identification of a wearer by a contactless operation. The present invention relates to a contactless identification code reader for reading.

[0002]

2. Description of the Related Art A gate that stores a unique identification code in advance and is carried by a carrier to enable unlocking of an entrance gate of a designated room without contacting the entrance gate. The contactless identification tag used for ensuring the function is recently being used frequently in many fields of use.

The contactless identification tag has a unique identification code that is read when it enters the operation area of the contactless identification code reader that reads the unique identification information stored in the contactless identification tag in a contactless state. The contactless identification tag receives a radio wave having a frequency f _C (hereinafter referred to as a power supply wave) transmitted from the contactless identification code reader and uses this as a carrier wave for transmission. The contactless identification tag modulates and transmits a carrier wave for transmission having a frequency f _C using a power supply wave with a unique identification code stored in its own memory.

The wireless transmission output transmitted from the contactless identification tag is received by the contactless identification code reader, and the contactless identification of the contactless identification tag with respect to the wearer is performed. The frequency component of the signal generated by the contactless identification tag modulating the carrier wave for transmission of the frequency f _C with the unique identification code becomes binary logical values “1” and “0” forming the unique identification code. respectively signals f ₁ and f ₀ frequencies assigned, the upper sideband of f _C + f ₁ and f _C + f ₀ centered at f _C (High Side
Band: hereinafter referred to as HSB), and f _C −f ₁ and f _C −
It becomes a lower side band (hereinafter referred to as LSB) of f ₀ . FIG. 3 shows the frequency relationship between these carrier waves for transmission and HSB and LSB.

FIG. 2 is a block diagram showing a configuration of a conventional contactless identification tag and a contactless code reader. However, Figure 2
The non-contact code reading device shown in (1) is described only for the configuration directly related to the present invention, and other well-known configurations necessary as a receiver such as a control circuit, an amplifier circuit, and a filter are omitted for convenience of description.

The contactless identification code reader 1 includes a transmitting antenna circuit 11, a feeding wave output circuit 12 for feeding the feeding wave to the transmitting antenna circuit 11, and a feeding wave output circuit 12 for generating a frequency f _C of the feeding wave. A local oscillator 13 which supplies
By mixing the local oscillation frequency f _C provided from the reception antenna circuit 14 and the local oscillator 13 with the reception frequency, the frequencies f corresponding to the unique identification codes “0” and “1” are obtained.
A mixer circuit 15 for extracting ₀ and f ₁ signal components;
The demodulation circuit 16 demodulates and outputs the unique identification code as output data from the signal components of the frequencies f ₀ and f ₁ .

The contactless identification tag 2 has an external tuning circuit 21 that tunes to a power supply wave having a frequency f _C , an interface circuit 22 that interfaces the tuning circuit 21 with the internal configuration, a memory 23, and a memory 23. To the logic circuit 24 for writing the unique identification code to the memory 23 and for reading the unique identification code written in the memory 23, and using the feed wave of the frequency f _{C received} via the interface circuit 22 as the carrier wave for transmission. Unique identification code "1",
The interface circuit 22, the memory 23, and the modulation circuit 25 that modulates and outputs f ₁ and f ₀ corresponding to “0”.
The logic circuit 24 and the modulation circuit 25 are usually integrated as an IC. The contactless identification tag 2 connects the logic circuit 24 to an external information device such as a computer and writes the unique identification code in the memory 23 in advance, or wirelessly writes it through the tuning circuit 21, and The unique identification code written in the memory 23 is read.

The tuning circuit 21 controls the frequency component f _{C of the} feed wave.
With a narrow band selectivity to, and tuned to receive the feed wave of the frequency f _C transmitted from the contactless identification code reader 1.
This feed wave is supplied to the logic circuit 24 and the modulation circuit 25 via the interface circuit 22. Logic circuit 24
Supplies a unique identification code from the memory 23 to the modulation circuit 25 based on the reception of the power supply wave. Modulation circuit 25
Uses the feed wave of frequency f _{C as} a carrier wave for transmission,
F that corresponds this to the unique identification code "1" or "0"
It is modulated by ₁ and f ₀ , and is transmitted as a radio transmission output including f _C + f ₁ and f _C + f _{0 of} HSB or f _C −f ₁ and f _C −f ₀ of LSB. The tuning circuit 21 has a narrow band but f
_Since f ₁ and f ₀ are sufficiently low frequencies compared to _C ,
HSB or LSB is transmitted at a level that is practically acceptable. The contactless identification code reader 1 tunes the receiving antenna circuit 14 to the frequency band of LSB or HSB by using the receiving antenna coil L ₁ and the tuning capacitor C ₁ to supply the power of the data component of the unique identification code. To receive. Usually, the frequency interval between the LSB and the HSB is large enough to be separated using the tuning characteristic of the antenna.
The power of f _C and the power in the frequency band of HSB or LSB, which are unnecessary components for data demodulation, are not input.

Next, the received signal containing the data component of the unique identification code and the local oscillation frequency of the frequency f _C supplied from the local oscillator 13 are input to the mixer circuit 15.
Only the data components of the unique identification codes of frequencies f ₀ and f ₁ are separated and output. By demodulating this data component in the demodulation circuit 16, the unique identification code of the contactless identification tag 2 is obtained. Further, the transmitting antenna circuit 11 has a frequency f _C due to the transmitting antenna coil L ₂ and the tuning capacitor C _2.
To form a tuning circuit for transmitting the feed wave of the frequency f _C provided from the local oscillator 13 via the feed wave output circuit 12.

[0010]

In the conventional contactless identification code reader described above, the power of the data component of the input unique identification code is L of the carrier wave for transmission of the contactless identification tag.
Only one of SB or HSB. LS now
When operating with only the B component as the receive input, the LSB
If strong external noise that matches the frequency band of the above exists in the operating environment of the contactless identification code reader, the signal-to-noise ratio (S / N ratio) at the antenna input end deteriorates, the communication distance decreases, and the data error rate. Problems such as rising of

In wireless communication between the contactless identification code reader and the contactless identification tag, good data communication can be performed if noise is not present even in the frequency band used for data communication, but noise is present. However, it has not been possible to easily change the power supply wave sent from the contactless identification code reader and the transmission carrier wave sent from the contactless identification tag. In addition, even if the operating frequency of these power supply wave and carrier wave for transmission installed in a place where there is noise is changed, the contactless identification code reader at the other place using the conventional frequency will change the contactless identification after the change. There are various problems such that it becomes impossible to receive the data of the unique identification code from the tag.

An object of the present invention is to solve the above-mentioned problems and to read a contactless identification code having a simple structure capable of ensuring good data communication of a unique identification code even in an operating environment of low S / N. To provide a device.

[0013]

The present invention has the following means constitution in order to achieve the above-mentioned object. That is, the contactless identification code reader of the present invention stores the unique identification code, receives the transmission carrier wave of the frequency f _C from the outside, and has the binary logical values “1” and “0” that form the identification code. A contactless identification code for recognizing the unique identification code by receiving a wireless transmission output of a contactless identification tag that assigns frequencies f ₁ and f ₂ to each of A reader, which sends the transmission carrier wave to a predetermined coverage area, and includes the upper sidebands and frequencies of the frequencies f _C + f ₁ and f _C + f ₀ included in the wireless transmission output transmitted by the contactless identification tag. f _C −
and has a configuration in which the receiving frequency switching means for enabling the switching reception of two frequency bands of the lower sideband of the f ₁ and f _C -f _0.

Further, in the apparatus of the present invention, the frequency switching means forms a tuning circuit together with an antenna for receiving the radio transmission output sent from the contactless identification tag, and the upper sideband and the lower sideband are combined. It has a configuration including two tuning capacitors for tuning to the two frequency bands, and a changeover switch for switching the two tuning capacitors.

[0015]

The operation of the present invention having the above construction will be described below. The contactless identification code readers that receive and read the unique identification code unique to each contactless identification tag wirelessly transmitted from the contactless identification tag are f _C + f ₁ and f _C +.
Only the HSB of the upper sideband having the frequency of f ₀ and the LSB of the lower sideband having the frequencies of f _C −f ₁ and f _C −f ₀ can be received. Here, f _C is a carrier frequency for transmission that the contactless identification code reader transmits and supplies to the contactless identification tag, and f ₁ and f ₀ are unique identification codes “1” that are different for each contactless identification tag. ",
It is a frequency set corresponding to "0".

As described above, since the conventional contactless identification code reader uses only one of HSB and LSB as the reception frequency band, the S / N of the communication path deteriorates and the communication distance decreases and the data error rate. However, even if this causes an increase in the above, it was not possible to avoid this effect by changing the reception frequency band. Even if the reception frequency band and the frequency used by the contactless identification tag can be changed in response to a noisy operating environment, other contactless identification code readers that use the conventional reception frequency band will not The code cannot be read.

According to the present invention, the contactless identification code reader is provided with a simple structure capable of performing reception switching of two frequency bands, HSB and LSB, by the reception antenna circuit, so that S / N of the operating environment can be improved. Corresponding to the above, it is possible to ensure good data communication between the contactless identification tag and the contactless identification code reader by operating while selecting the one with the lower noise in these two frequency bands. In addition, the problem of loss of compatibility between the contactless identification code readers that occurs when simply trying to avoid problems by simply changing the communication frequency does not occur, and there is no change in contactless identification tags. You don't have to.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. The embodiment shown in FIG. 1 includes a contactless identification code reader 1a of the present invention and a contactless identification tag 2 shown together. The non-contact identification code reader 1a has the same transmitting antenna circuit 11 and feeding wave output circuit 1 as the conventional example shown in FIG.
2, local oscillator 13, mixer circuit 15 and demodulation circuit 1
6, the receiving antenna circuit 17 directly related to the present invention
Is provided. Further, the contactless identification tag 2 has the same configuration as the conventional example shown in FIG. 2 and has a tuning circuit 21 and an interface circuit 2.
2, a memory 23, a logic circuit 24, and a modulation circuit 25. Since the components having the same reference numerals as those of the conventional example in FIG. 2 have the same contents, detailed description of these components will be omitted.

The reception antenna circuit 17 of the contactless identification code reader 1a includes a reception antenna coil L ₁ and two tuning capacitors C _H and C _L for tuning the reception antenna coil L ₁ in the frequency bands HSB and LSB.
And two switching switches S ₁ and S ₂ for switching and connecting the tuning capacitor C _H or C _L to the receiving antenna coil L ₁ .

Next, the operation of this embodiment will be described.
The tuning capacitor C _H of the receiving antenna circuit 17 has a capacitance for setting the tuning frequency of the receiving antenna coil L ₁ to HSB, and the tuning capacitor C _L has a capacitance for setting LSB. Further, the changeover switches S ₁ and S ₂ are switch circuits capable of switching a minute signal by using elements such as an analog switch and a relay. Now, the changeover switches S ₁ and S ₂ are both set to the L side, and the tuning frequency of the receiving antenna circuit 17 is set to the LSB frequency band by the receiving antenna coil L ₁ and the tuning capacitor C _L. If external noise that matches the LSB frequency band exists in the operating environment of the reader, problems such as a decrease in communication distance and an increase in data error rate occur.

At this time, the tuning frequency of the receiving antenna is changed from the LSB to the HSB frequency band by switching the changeover switches S ₁ and S ₂ from the L side to the H side. Note that the changeover switches S ₁ and S ₂ may be of a type that is manually changed, and a control circuit (microprocessor or the like) (not shown) in the non-contact identification code reader 1a determines automatically from the result of data demodulation. You may use the switch type. Thus, the contactless identification code reader 1
External noise of HSB existing in the operating environment of a is LSB.
When the noise is smaller than the external noise of, the better data communication can be secured as compared with the case of performing the LSB communication.

In this way, the frequency used for communication is selected to one of the LSB / HSB low noise frequency bands in accordance with the external noise situation in the operating environment where the contactless identification code reader is installed. As a result, the possibility of ensuring good data communication can be significantly increased. Usually, the HSB and the LSB are separated by a degree that can be separated by utilizing the tuning characteristic of the antenna.
Therefore, even if strong noise is present in the HSB and good data communication cannot be performed, noise is not often present in the LSB, and the possibility of good data communication is significantly increased.

The contactless identification tags, which are larger in number than the contactless identification code readers, do not need to be changed at all, so they are set on the HSB side and on the LSB side. Even in a system in which a contactless identification code reader is mixed, data communication can be secured without any problem.

[0024]

As described above, according to the present invention, a non-contact type which transmits a transmission carrier frequency to a non-contact identification tag and is wirelessly transmitted from the non-contact identification tag using the transmission carrier frequency. The contactless identification code reader that receives and reads the identification code unique to the identification tag switches between the two frequency bands HSB and LSB transmitted from the contactless identification tag according to the S / N of the communication path and receives them. By providing the configuration, there is an effect that good quality identification code reception can always be ensured without changing the contactless identification tag.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a contactless identification code reader according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional non-contact identification code reader.

FIG. 3 is a diagram showing a relationship between a frequency of a carrier wave for transmission transmitted by a contactless identification code reader and frequencies of HSB and LSB received.

[Explanation of symbols]

1 non-contact identification code reader 1a non-contact identification code reader 2 non-contact identification tag 11 transmitting antenna circuit 12 feed wave output circuit 13 local oscillator 14 receiving antenna circuit 15 mixer circuit 16 demodulating circuit 17 receiving antenna circuit 21 tuning circuit 22 interface Circuit 23 Memory 24 Logic circuit 25 Modulation circuit C ₂ Tuning capacitor C _H Tuning capacitor C _L Tuning capacitor S ₁ switching switch S ₂ switching switch L ₁ receiving antenna coil L ₂ transmitting antenna coil

Claims (2)

[Claims] 1. A unique identification code is stored, a carrier wave for transmission having a frequency f _C is externally received, and frequencies f ₁ and f are assigned to binary logic values “1” and “0” forming the identification code, respectively. _A contactless identification code reader that recognizes the unique identification code by receiving a wireless transmission output of a contactless identification tag that assigns ₂ and modulates the transmission carrier wave with the unique identification code and sends the modulated carrier wave. A credit carrier is sent to a predetermined coverage area, and the upper sideband of frequencies f _C + f ₁ and f _C + f ₀ included in the wireless transmission output transmitted by the contactless identification tag and frequencies f _C −f ₁ and f _C. −
A contactless identification code reader comprising a reception frequency switching means capable of switching reception of two frequency bands including the lower sideband of f ₀ . 2. The frequency switching means forms a tuning circuit together with an antenna for receiving the wireless transmission output sent from the contactless identification tag, and two frequency bands of the upper sideband and the lower sideband. 2. The non-contact identification code reader according to claim 1, further comprising two tuning capacitors for tuning to each other and a changeover switch for switching the two tuning capacitors.