JP2000278169A - Interrogator of mobile communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately convert response data from a responder at all times in the case that an interrogator makes radio communication with the responder by means of an analog signal that is amplitude-modulated by digital data. SOLUTION: The interrogator 1 makes radio communication with a mobile responder 3 by means of an analog signal that is amplitude-modulated by digital data, reception circuits 17, 18 receive the analog signal from the responder 3 in a radio wave, extract a data signal component from the analog signal through a half wave rectifier system and a converter 26 converts the extracted data signal component into digital data. In the case of rectifying the analog signal received by the reception circuits 17, 18, even when a rebound waveform takes place, since the rebound waveform is aborted by the half wave rectification, the converter 26 can convert the extracted data signal component into correct digital data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interrogator for wirelessly communicating with a transponder which can be moved by an analog signal amplitude-modulated by digital data, and more particularly to accurately converting a data signal component extracted from an analog signal into a digital signal. And an interrogator for a mobile communication system.

[0002]

2. Description of the Related Art As a non-contact type mobile communication system for performing analog wireless communication between an interrogator and a movable transponder, for example, an ID tag (a transponder which moves by being attached to luggage or the like). ) And a reader / writer (interrogator) that is fixedly installed or carried by the user and wirelessly communicates data with the ID tag, or a non-contact type ID tag system that is moved by being carried by the user. There is known a non-contact type IC card system including an IC card (a transponder) that performs a communication and a reader / writer (an interrogator) that is fixedly installed and wirelessly communicates data with the IC card.

[0003] Such an ID tag system is used, for example, for sorting transported luggage. A label-like ID tag having a size of about 1 cm x 5 cm is attached to each luggage, and an operator operates a reader / writer. The delivery management of each package is performed by reading data such as an identification code (ID), a product name, and a destination stored in the ID tag by using. Such an I
The D tag has a memory and a wireless communication function unit, and has an ID
When the tag enters the communicable area of the reader / writer, the reader / writer transmits question data requesting an ID or the like, and the ID tag returns response data such as its own ID or the like in response thereto, whereby the reader / writer Identify the ID tag,
Management of product names, delivery destinations, etc. is performed.

In such an ID tag system, an amplitude modulation system (or ASK: Amplitude Shift Keying, in which the amplitude is made to correspond to a discrete level) in which a carrier is amplitude-modulated by digital data to be transmitted and transmitted wirelessly is used. Conventionally, for example, the system configuration is as shown in FIG. Note that the example shown in FIG.
The D tag 3 is not provided with a power source such as a battery cell, and the transponder 3 is operated by the power transmitted from the interrogator (reader / writer) 1 by a carrier wave. This is a contactless ID tag system that performs analog wireless communication as described below using the antennas 10 and 30.

In this ID tag system, the interrogator 1
Then, the carrier generated by the synthesizer 11 is
2. Amplitude-modulate with digital interrogation data and operation clock in 2 and transmit the obtained analog interrogation signal to transmission amplifier 1.
The signal is amplified by 3 and transmitted wirelessly from the antenna 10 via the circulator (distribution / combiner) 14.

On the other hand, in the transponder 3, the operating power is received from the interrogator 1 by a power receiving circuit (not shown) using the antenna 30 in common or by using a separate power receiving antenna. The interrogation signal received at 30 is subjected to amplitude demodulation and digital conversion by the modulator / demodulator 31, and the controller 32 writes and reads data to and from the memory 33 according to the demodulated interrogation data in digital format. The digital response data to the query data is output from the control unit 32 to the modem 31,
1 modulates the amplitude of the carrier received from the interrogator 1 with the response data, and wirelessly transmits the obtained analog response signal from the antenna 30 to the reader / writer 1. That is, the use of the carrier wave from the interrogator 1 eliminates the internal oscillating circuit and reduces the required operating power.

In the interrogator 1, the analog response signal received by the antenna 10 is input to the distributor 15 via the circulator 14, and the response signal (received signal)
And one of the response signals is input to the first receiving circuit 17 via the phase shifter 16, and the other response signal is input to the second receiving circuit 18 as it is. Phase shifter 16
Then, the phase of one response signal is shifted by 45 degrees, and the first receiving circuit 17 separates the interrogation signal input from the transmission amplifier 13 at a constant level and the phase-shifted response signal into
9 to extract the difference, remove unnecessary components by the filter 20, amplify the extracted response data signal component by the reception amplifier 21, and output the amplified response data signal component to the synthesis amplifier 22. On the other hand, in the second receiving circuit 18, the interrogation signal input from the transmission amplifier 13 at a constant level and the response signal that is not phase-shifted are mixed by the mixer 23 to extract the difference, and the filter 24 removes unnecessary components. Then, the extracted response data signal component is amplified by the reception amplifier 25 and output to the synthesis amplifier 22.

That is, the double balance mixers 19, 2
3 is input with a certain level to the LO terminal, and the double balance mixers 19 and 23
It cancels its own interrogation signal riding on the response signal input from the F terminal, and extracts only the response data signal component transmitted by the transponder 3. The combining amplifier 22 combines the two input response data signal components, and the level converter 26 converts the combined analog-level response data signal component into a digital signal and outputs the digital signal to a control unit (not shown).

[0009] Here, in the mobile communication system in which the transponder 3 and the interrogator 1 move as described above, and the distance between the interrogator 1 and the transponder 3 changes, the distance changes. Since the phase of the signal received by the interrogator 1 changes, only one of the first receiving circuit 17 or the second receiving circuit 18 greatly decreases the reception level according to the change in the distance, and the response signal Cannot be received. Assuming that the wavelength of the carrier is λ, the second receiving circuit 1 that does not perform phase control
As shown by the solid line in FIG.
4 = The level is extremely reduced in 90 degree cycles,
A state where the received signal cannot be demodulated occurs.

Therefore, in the ID tag system as described above, the received signals are inputted to the first receiving circuit 17 and the second receiving circuit 18 with their phases shifted from each other by 45 degrees, and as shown in FIG. The phase shifter 16 shifts the reception signal of the first reception circuit 17 by λ / 8 = 45 degrees with respect to the reception signal of the second reception circuit 18. by this,
The extremely low level is compensated for by the other received signal, and the outputs of the receiving circuits 17 and 18 are combined so that the response data can be received at a certain level or more as a whole.

The wireless communication between the interrogator 1 and the responder 3 is performed by a time-division frame as shown in FIG. And the upstream frame to the interrogator 1 are assigned alternately. As shown in FIG. 6, in each frame, bit data "1" (or "0") has an analog waveform positioned at the front of the frame, and bit data "0".
(Or “1”) is represented by the analog waveform located at the rear of the frame.

[0012]

However, in the mobile communication system as described above, the receiving circuits 17 and 18 extract the response data signal component (FIG. 6) from the analog received signal by the full-wave rectification method. In particular, there is a problem that bit data (data “1” in the example of FIG. 6) in which an analog waveform is located at the front part in the frame cannot be correctly converted by the level converter 26.

That is, when rectifying a data signal component in which an analog waveform is located at the front in a frame, a saturated analog waveform appears as a rebound of the opposite polarity as shown by a broken line in FIG. As a result, this rebound waveform is rectified as shown by a solid line in FIG.
Rectification may occur as a state where two waveforms are arranged side by side with a dip having a lowered level. When it changes as shown in FIG. 7, in the example of FIG.
Despite being "1", the level converter 26 outputs the bit data "1", "0" or the bit data "1", "1".
In some cases, the interrogator 1 could not correctly recognize the response data from the transponder 3. The data signal component in which the analog waveform is located at the rear of the frame. When rectifying is performed, even if a rebound waveform is generated, the rectification is out of the frame, so that such a problem does not occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in an interrogator for performing radio communication with an transponder using an analog signal amplitude-modulated by digital data, the response data from the transponder is always accurate. It is an object of the present invention to provide a recognizable interrogator.

[0015]

An interrogator for a mobile communication system according to the present invention is an interrogator for performing radio communication with a movable transponder using an analog signal amplitude-modulated by digital data. The unit wirelessly receives the analog signal from the transponder, extracts a data signal component from the analog signal by a half-wave rectification method, and a converter converts the extracted data signal component into digital data.

Therefore, when the receiving unit rectifies the analog signal received from the transponder, even if a rebound waveform occurs as described above, the rebound waveform is discarded by half-wave rectification. As described above, an erroneous data signal component does not occur, and the extracted data signal component can be converted into correct digital data by the converter.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which the present invention is applied to a non-contact ID tag system will be described with reference to FIGS. Note that the same reference numerals are given to the same functional portions as those of the conventional non-contact ID tag system shown in FIG. 3, and a duplicate description will be omitted.

The interrogator 1 of this embodiment has a configuration in which the first receiving circuit 17 and the second receiving circuit 18 extract a response data signal component from a received analog signal by a half-wave rectification method. . More specifically, the filters 20 and 24 remove the noise components from the response data signal components extracted from the received analog signals by the mixers 19 and 23 in the same manner as described above, and only one polarity (in this example, only the positive electrode). ), And the one-polarity response data signal component is amplified by the reception amplifiers 21 and 25 and output to the synthesis amplifier 22.

Therefore, in comparison with the conventional full-wave rectification method shown in FIG. 7, according to the half-wave rectification method of this embodiment, when the data signal component in which the analog waveform is located at the front part in the frame is rectified. Even if saturation occurs, the reverse-polarity component is discarded by half-wave rectification, so that this does not appear as a rebound waveform of the reverse polarity. As shown in FIG. 2, the response data signal component is extracted as a correct waveform. Is done. Therefore, the level converter 26 can convert the response data signal component into correct bit data (“1” in this example), and the interrogator 1 can correctly recognize the response data from the responder 3. .

In this embodiment, a level converter 27 for converting the extracted response data component into display data, and a reception level display for displaying and outputting the reception signal level of the interrogator 1 based on the display data. Vessel 28 is provided.

In the above example, only the positive signal component is left by half-wave rectification. Conversely, only the negative signal component may be left. Further, in the above example, the reception signal is split and the reception processing is performed by the two-series reception circuit. However, the reception processing may be performed by the one-series reception circuit.

The transponder 3 has no power supply, and
The interrogator 1 and the responder 3 are operated by the power supplied from the mobile communication system, and the interrogator 1 and the responder 3 are described as an example of a mobile communication system in which a carrier is amplitude-modulated by data and wirelessly communicated. Alternatively, the present invention can be implemented in various system configurations. For example, a system configuration in which the transponder 3 has a battery power supply and does not supply operating power from the interrogator 1 to the transponder 3 may be used. Also, for example, mobile communication may be performed in another mode such as an IC card system. The system may be configured.

[0023]

As described above, according to the interrogator according to the present invention, a data signal component is extracted from a received analog signal by a half-wave rectification method, and the data signal component is converted into a digital signal. Even if a rebound waveform occurs in the processing, correct bit data can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a contactless ID tag system according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram illustrating the operation of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional non-contact ID tag system.

FIG. 4 is a graph showing a relationship between a distance and a received signal level.

FIG. 5 is a conceptual diagram illustrating a communication frame.

FIG. 6 is a conceptual diagram illustrating a relationship between bit data and a waveform.

FIG. 7 is a conceptual diagram illustrating a conventional problem.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reader / writer (interrogator), 3 ... ID tag (responder), 11 ... Synthesizer, 12 ... Modulator, 13 ... Transmission amplifier, 17 ... First reception Circuit, 18 ... second receiving circuit, 19, 23 ...
Mixer (mixer), 20, 24 ... filter, 2
1, 25 ... receiving amplifier, 22 ... synthetic amplifier,
26 ... level converter,

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masanori Asakusa 3-14-20 Higashinakano, Nakano-ku, Tokyo International Electric Company (72) Inventor Kazuo Funakubo 3-14-20 Higashinakano, Nakano-ku, Tokyo International Inside Electric Co., Ltd.

Claims (1)

[Claims] 1. An interrogator for performing wireless communication with an analog signal amplitude-modulated by digital data with a movable transponder, wherein the interrogator wirelessly receives the analog signal from the transponder and performs half-wave rectification. An interrogator for a mobile communication system, comprising: a receiving unit that extracts a data signal component from the analog signal; and a converter that converts the extracted data signal component into digital data.