JPH0390884A - Moving body identification device - Google Patents

Abstract

PURPOSE:To evade a failure in communication due to the movement of a responder and to obtain accurate data by selecting a mixture output which has a larger envelope output at all times and eliminating the phase inversion of the output and the other remaining mixture output. CONSTITUTION:When the responder 200 modulates a received unmodulated high frequency 1a with a modulating signal 2a based upon its ID code and resends the modulated signal, an interrogator 00 mixes and detects the received high frequency 1a by mixers 107 and 108 and signals 1b and 1c are obtained through amplifiers 109 and 110 and further compared 111 and 112 with a specific level to obtain signals 1d and 1e. The signals 1b and 1c, on the other hand, have their envelopes detected 113 and 113, a signal 1f is obtained through a waveform shaper 116, and 0 when the signal 1b is larger or 1 when the signal 1c is larger is outputted. The signals 1d - 1f are inputted to a signal processing circuit 17 and the phases of the signals 1d and 1e are compared and inverted properly to put the data in phase and select them, thereby outputting the same signal 1h as the signal 2a. Therefore, even if the responder 200 moves, accurate data are obtained continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a mobile object identification device, and more particularly to a mobile object identification device that can prevent loss of demodulated signals when using homodyne detection.

[Prior Art] In recent years, attempts have been made to attach ID cards to moving objects such as containers, automobiles, and human bodies to perform logistics management, fee collection, gate management, etc.
A compact and lightweight transceiver (transponder) that responds with an identification code in response to an interrogation radio wave from a central transceiver (interrogator), which can identify moving objects without contact, is attracting attention.

In such a mobile object identification device, since the transponder needs to be as small as possible, it is usually not provided with an oscillator for generating a carrier wave, but instead receives and modulates an unmodulated carrier wave emitted from the interrogator and retransmits it. is adopted. in this case,
Detection in the interrogator is generally homodyne detection in which a modulated carrier wave and the unmodulated carrier wave are mixed in a mixer.

Homodyne detection is characterized by high sensitivity, but
When this is used for communication with a moving transponder, the mixed detection output becomes zero every time the relative distance between the interrogator and the transponder becomes half a wavelength of the carrier wave, making communication impossible.

In order to solve this problem, for example, Japanese Patent Application Laid-Open No. 63-52082
The publication states that the modulated carrier wave received by the interrogator is divided into two received waves with a phase of 90 degrees, each is mixed with the unmodulated carrier wave, and this mixed output is detected by envelope detection. A device has been proposed that selects and demodulates a received wave with a higher line output.

[Problems to be Solved by the Invention] According to the device proposed above, it is possible to appropriately select the mixed output on the side that does not become zero and always perform good communication.
When the transponder moves at a high speed or when a relatively long data signal is read out following the identification signal, it is necessary to switch the mixed output during signal readout. The phase of each of the above mixed outputs is reversed each time it becomes zero, so when switching the mixed output, a problem may occur where the phase of the mixed output before and after switching is shifted by 180 degrees. .

The present invention solves these problems, and it is possible to avoid the communication failure caused by the movement of the transponder, and to always obtain accurate data even when communicating with a transponder that moves at high speed or when reading long data from the transponder. An object of the present invention is to provide a mobile object identification device that can obtain the following information.

[Means for Solving the Problems] The configuration of the present invention will be explained with reference to FIG. 1. In a mobile object identification device that performs identification communication between an interrogator provided on a fixed side and a transponder provided on a mobile object, The interrogator includes a carrier wave generating means that continuously generates an unmodulated carrier wave, a transmitting means that transmits the carrier wave, and two receivers that receive the modulated carrier wave and whose phases are 90 degrees to each other. a distribution means for distributing the received waves into waves, a mixing means for mixing each of the received waves with the unmodulated carrier wave and detecting the mixture, a detection means for envelope-detecting the mixed output of each of the mixing means, and an envelope output of each of the detection means. a selection means for comparing and selecting the larger mixed output;
If the phase of one of the selected mixed outputs is inverted with respect to the remaining mixed output, phase matching means eliminates this inversion and makes the phases match, and demodulates the selected one of the mixed outputs. and a demodulating means for obtaining an identification signal, and the transponder is equipped with a replying means for modulating the received unmodulated carrier wave and returning the identification signal.

[Function] In the mobile object identification device having the above configuration, the amplitude of the mixed output from each mixing means periodically becomes zero as the transponder moves, and the envelope of the mixed output from each detection means that detects this is envelope-detected. The output changes in magnitude alternately. Therefore, if the mixed output with the larger envelope output is always selected, the amplitude of the selected mixed output will not become zero even if the transponder moves.

When selecting one of the mixed outputs, the phase matching means compares the phases of the selected mixed output and the remaining mixed output, and if one is inverted in phase with respect to the other, The phases are made to match by eliminating this inversion.

In this way, the alternately selected mixed outputs have sufficiently large amplitudes and are always matched in phase, so that by demodulating them, an accurate identification signal can be obtained.

[Example] An example of the present invention will be shown. In FIG. 2, 100 is an interrogator that reads data from the transponder 200, and lOL is
An oscillator that generates unmodulated high frequency waves for reading. 10
2 is a branch that distributes high frequency waves in two directions at a predetermined power ratio.

103 is a circulator that controls a high frequency transmission path. 104 is an antenna that transmits and receives high-frequency radio waves. 105
is connected to a terminating resistor 118 that matches the characteristic impedance, and receives the received input high frequency at the same power ratio and with a phase difference of 9.
Hybrid that outputs at 0°. Reference numeral 1 and 06 denote a distributor that distributes the one high frequency wave branched by the branch 102 and not transmitted, with the same power ratio and the same phase. 107 is a first mixer composed of a Schottky barrier diode, etc., which performs mixed square law detection of two human powers, and works as a homodyne detector.
, 108 is a second mixer similar to 107, but the received signal is subjected to homodyne detection in a state advanced by 90° compared to 107.

109 is a first amplifier that receives the output of the first mixer 107 and amplifies only the modulated component of the received wave.

110 is also the second amplifier. 111 is a first waveform shaper that compares the output of the first amplifier 109 at a predetermined level and converts it into a digital signal.

Similarly, L12 is a second waveform shaper. 113 is a first envelope detector that detects the envelope of the output of the first amplifier 109; 114 is also the second envelope detector, 1■
5 is a differential amplifier that amplifies the difference between the outputs of the first and second envelope detectors 113 and 114; A third waveform shaper 116 receives the output of the differential amplifier 115, compares it with a predetermined level, and converts it into a digital signal. 117 receives the outputs of the first to third waveform shapers 111, 112, 11, 6, digitally processes the signals, and continuously provides normal data even when the transponder 200 moves. This is a phase matching circuit that outputs from the terminal 1h. 200 is a transponder, 20
An antenna 1 receives an unmodulated high frequency wave from the interrogator 100 and transmits a high frequency wave modulated with a predetermined ID code.

202 is a modulator that modulates the received unmodulated high frequency wave with a predetermined ID code. 203 is a memory that outputs a predetermined ID code.

In FIG. 3 showing details of the phase matching circuit 117 in FIG. 2, 301, 302, 303, and 304 are exclusive OR gates. 305 is Lee Burke. 306.307.30
9 is or gate. 310.311 latches the D input at the rising edge of the C input, and the C input is 0! A latch that holds the latch state with l and outputs the D input as is with n. 312.313 is an and gate. 314 is Noah Gate. 315 is a first initialization element that outputs the 3a signal in FIG. 5 (5) for a predetermined time when the power is turned on. 316 is a second initialization element that outputs the 3b signal in FIG. 5 (6) as a pulse when the power is turned on. This is an initialization element.

The operation of the above device will be explained below with reference to FIG. 4 and FIG. The modulated signal 2a based on the ID code (FIG. 4 (2)) performs ASK modulation on the received unmodulated high frequency wave and retransmits it (signal 2b in FIG. 4 (3)).

The received high frequency wave is subjected to mixed detection by mixers 107 and 108 of two homodyne circuits whose phases are orthogonal, and the output thereof is transmitted through first and second amplifiers 109 and 110 as shown in FIG. 5) are the signals Lb and lc. 4th above
The figure shows a state in which the relative distance between the transponder 200 and the interrogator 100 is changing at a constant speed, and the output is
Alternately take maximum and minimum values.

Output signals 1b, l of the first and second amplifiers 109.110
c (Fig. 4 (4>, (5)) is compared with a predetermined level ■Tll by the second waveform shaper 111, 112, and the signals 1d, le (Fig. 4 (6), (7) ).

On the other hand, the signals 1b and lc are detected by the second envelope detectors 113 and 114, respectively, and then passed through the differential amplifier 115 and the third waveform shaper 116 to the signal if (FIG. 4 (8)
> becomes. That is, signal 1f outputs n Q n when signal 1b is large, and when signal IC is large)) 1
Output n.

The signals 1d, lc, and if are input to the signal processing circuit 117. Since the signal processing circuit 117 has a latch, when the power is turned on, the first and second initialization elements 31
5.316 initializes the latch. Then, an exclusive OR gate 30 for the input signals 1d and le
2. Compare the phase at 303 and latch the output at 310.3
11, the time point when the signal if changes is memorized, and the output is
The data is input to exclusive OR gates 301 and 302, and the phase is appropriately inverted to align the data phases. Thereafter, it is selected by AND gates 312 and 313 and output from NOR gate 314 (signal 1h in FIG. 5 (15)). The signal 1h obtained by the above procedure is transmitted to the transponder 2 as shown in FIG.
The modulation signal 2a is the same as the modulation signal 2a of 00, and even if the transponder 200 moves, it is possible to read data continuously and accurately.

Further, even if the moving speed and moving direction change, similar results can be obtained.

[Effects of the Invention] As described above, according to the mobile object identification device of the present invention, good and reliable data can be obtained even when the moving speed of the transponder is high or when the data length read from the transponder is long. can be read.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to claims, Figs. 2 to 5 show an embodiment of the present invention, Fig. 2 is an overall block diagram of the device, Fig. 3 is a circuit diagram of a phase matching circuit, and Fig. 4 and FIG. 5 is a signal time chart. 100... Interrogator 0 0 0 0 1 1 1 0 0 0 1... Oscillator 4... Antenna 5... Hybrid 7.108... Mixer 3.114... Envelope detector 5. ... Differential amplifier 7 ... Phase matching circuit O ... Responder 1 ... Antenna 2 ... Modulator

Claims (1)

[Claims] In a mobile object identification device that performs identification communication between an interrogator provided on a fixed side and a transponder provided on a mobile object, the interrogator includes a carrier wave generating means that continuously generates an unmodulated carrier wave, and a carrier wave generating means that continuously generates an unmodulated carrier wave; a transmitting means for transmitting a carrier wave; a distributing means for receiving the modulated carrier wave and distributing it into two received waves having phases different from each other by 90 degrees; and mixing each of the received waves with the unmodulated carrier wave. A mixing means for detecting, a detection means for envelope-detecting the mixed output of each mixing means, a selection means for comparing the envelope outputs of each detection means and selecting the larger mixed output, and a selected one of the mixing means. If the phase of the output is inverted with respect to the other remaining mixed output, a phase matching means for eliminating this inversion and matching the phases, and demodulating the selected one of the mixed outputs to obtain an identification signal. 1. A mobile object identification device, wherein the transponder comprises a demodulating means, and the transponder includes a replying means for modulating the received unmodulated carrier wave and returning the identification signal.