JP3197966B2 - transponder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transponder using microwaves, and more particularly to a transponder using spread spectrum communication to enable high quality communication.

[0002]

2. Description of the Related Art Conventionally, this type of transponder emits a response signal having a frequency different from the frequency of the interrogation signal when the interrogator receives the interrogation signal from the transmitter (interrogator). Thus, communication is performed between the transmitter and the receiver.

[0003] The present applicant has previously filed Japanese Patent Application No. Hei.
No. 2647 proposed a transponder type train position detecting device. In the proposed device, a plurality of receivers (hereinafter, referred to as tags) are provided on a train at predetermined intervals, and a train position is detected based on which tag the transmitter has communicated with. Therefore, it has a feature that the train position can be detected at the tag installation interval, and the train position can be detected with an accuracy of, for example, several meters.

[0004]

However, in the above proposed apparatus, the tag is attached to a train made of metal, so that the reflected wave from the vehicle body becomes noise, or the tag is used to improve the train detection accuracy. If the installation interval is small, multiple tags may be present in the communication area (reaction area) of the transmitter. If the tag is received by the transmitter while communicating with multiple tags, interference will occur at the carrier level. There is a disadvantage that reception becomes impossible.

[0005] Further, since the transmitter is provided together with a transmitter for transmitting a signal to the tag in the same device and a receiver for receiving a signal from the tag, the transmitter transmits from the transmitter to the receiver. Leakage of a signal into a vehicle, a so-called perspective problem, remains as an inevitable problem.

Accordingly, the present invention has been made to solve the above-mentioned drawbacks, and an object of the present invention is to adopt a spread spectrum communication (hereinafter, referred to as SS communication) system to perform S / S communication.
N ratio is improved, and train positions can be determined with a precision of several meters, for example,
It is an object of the present invention to provide a high-performance transponder which can be applied to a train position detecting device capable of detecting with 0 m accuracy. In particular, in the present invention, to solve the above-mentioned perspective problem
And the phase of the interrogation signal received by the
Phase modulation and when this phase modulation is adopted
To resolve the existence of the so-called dead zone
In the receiver of the transceiver, the received response signal is
And their interrogation signals are phase-shifted by 90 °.
Demodulation processing is performed.

[0007]

In order to achieve the above object, a transponder according to the present invention transmits an interrogation signal having a predetermined frequency from a transmitter of a transmitter to a tag, and the tag transmits the interrogation signal to the tag. when receiving the signal, the transponder transmits to the receiving part of the transmitter a response signal including predetermined information, the tag is different to the first PN code及 beauty second PN code with each other Selecting the first PN code and the second PN code corresponding to the generated PN code generation means and the logical values “1” and “0” forming the predetermined information; A modulating means for subjecting the predetermined information to spread spectrum modulation processing using the selected PN code, and a signal modulated by the modulating means,
Response signal generating means for generating the response signal by phase-modulating the phase of the received interrogation signal by 180 °, wherein the receiving unit of the transmitter transmits the received response signal to the interrogation signal.
Signal and two signals obtained by shifting the phase of the interrogation signal by 90 °
First PN code及 beauty second P in extracted in each PN code extracting means for extracting demodulation processing to the first PN code及 beauty second PN code, respectively, that said extracting means
First PN code及 beauty second PN provided in advance with N code
Reproducing means for obtaining a correlation value between the two using a code and reproducing the predetermined information based on the obtained correlation value.

[0008]

In the above configuration, when the tag receives the interrogation signal from the transmitter, information to be responded (hereinafter referred to as data).
The interrogation signal is phase-modulated by 180.degree. With a signal obtained by modulating "1" and "0" with the first and second PN codes to generate a response signal for responding to the transmitter. The receiving unit of the transmitter that has received the response signal demodulates the interrogation signal using two signals having phases different by 90 ° to extract the first and second PN codes. The extracted PN code is a previously prepared P
A correlation value with the N code is obtained. Then, data is reproduced from the obtained correlation value.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view when the transponder according to the present invention is applied to train position detection.

The transmitter A is installed on the ground side near the rail R on which the train A runs, and tags B, B are provided on the side of the train A at predetermined intervals, for example, every 5 m.
... are provided. Each of the tags B, B,... Stores in advance a vehicle number, a distance position from the train tip, a tag number, and the like as data.

Therefore, since the installation position of the transmitter is known, depending on which tag B the transmitter A has communicated with,
The head position and tail position of the train A can be detected accurately and with high accuracy. FIG. 2 shows the transmitter A and the tag B (here, only one tag is shown, but each tag is the same except for the data stored therein, so the other tags are omitted). FIG. 3 is a block diagram illustrating an electrical configuration.

Hereinafter, FIG. 2 will be described in accordance with the order of communication.
The transmitting unit a of the transmitter A has a predetermined frequency, for example, 2.45 GHz.
_It has a signal generator 1 for generating a microwave interrogation signal (f) of _{z, and} the interrogation signal (f) is amplified by an amplifier circuit 2 and separated from a response signal from a tag B. It is fired toward the tag B through the circulator 3.

The interrogation signal emitted from the antenna 4 is received by the antenna 5 on the tag B side. Then, the received interrogation signal is shifted in phase by 180 ° (π) by the modulation circuit 6 by a response signal generated by modulating based on the data stored in advance in the tag B,
From the antenna 4 on the transmitter A side.

The response signal is generated by the following components provided in the tag B. That is, the tag B has a data generation circuit 7 having a ROM in which predetermined data is stored, and the output of the data generation circuit 7 is input to a pair of AND circuits 8a and 8b. It is configured as follows. One of the inputs (input to the AND circuit 8b on the illustrated side) is configured to be input via the inverting circuit 9.

Therefore, when there is an output corresponding to the logical value "1" among the data output from the data generating circuit 7, it is output to the AND circuit 8a, while the output corresponding to the logical value "0" is provided. Is output to the other AND circuit 8b.

The other input terminals of the AND circuits 8a and 8b are connected to the first and second PN code generators 10a and 10b, respectively.
The output of b is configured to be input.
The PN code generators 10a and 10b are configured to output _first and _second PN codes (PN ₁ and PN ₂ ) of different types in synchronization with each other with the clock pulse from the clock pulse generator 11. I have.

The output terminals of the AND circuits 8 a and 8 b are configured to be input to the OR circuit 12 and output to the modulation circuit 6.

FIGS. 3A to 3C show examples of waveforms at the respective points of the above-described tag B (points (1) to (2) in FIG. 2).

That is, FIG. 3 shows a state in which data of "1, 0, 0, 1,..." Is output in the output waveform at the point of FIG. 2, and FIG. The output waveform at the point shown in FIG. 2, that is, the data is represented by a PN code (P
N ₁ or PN ₂ ). FIG. 3 shows a response signal generated by shifting the phase by 180 ° (π) with the output waveform of the portion of FIG. 2, that is, the waveform of the received interrogation signal shown in FIG. ing. FIG. 3 is an enlarged view of only the same part. Phase of interrogation signal received at receiver B
Is phase-modulated by 180 ° for the following reason. You
That is, as described above, the interrogation signal of the transmitter A is
And the signal is decoded again by the receiver a2 of the transmitter A.
In the system, the direct leakage signal from the transmitter A is a big problem.
Become. In other words, very large reception interference at the same frequency
Issue. In order to solve this, generally, the receiver B
Phase-modulates the reflected wave with data and sends it back.
You. The magnitude of the phase modulation can be considered from 0 to 180 °
Are 0 ° and 180 ° corresponding to “0” and “1” of the data.
It is easiest to take the value of
Better. In the receiving part a2 of the transmitter A, direct leakage
A composite signal of the signal and the received reflected signal is input. This
Here, a part of the transmission signal is guided to the receiving unit a2, and phase detection is performed.
You. That is, a demodulated output is extracted according to the phase difference.
At this time, the transmission leakage signal has almost no transmission distance,
Since it is input immediately, the phase difference with the transmission signal becomes 0.
The output of the phase detection is only the DC component and twice the frequency component.
Become. On the other hand, the received reflected wave is modulated with data,
Is also the value obtained by dividing the wavelength by the distance between the transceivers A and B.
Are input out of phase. When this is phase detected,
AC output corresponding to the data (data "0", "1"
Has changed). Where the output signal is
Pass filter (DC component cut and cut of double component of carrier wave)
G), only the signal from receiver B is extracted
Let Decoding this gives information. Other modulation
In a method, for example, a method of performing amplitude modulation and returning a reflected wave,
A very small modulation signal is added to the large output of the leakage signal.
Transmitter, level fluctuation due to noise
Phase modulation directly affects the demodulated output,
The overall performance will be very poor.

The response signal received by the antenna 4 is
Circulator - first pair provided in the receiving unit a ₂ transmitter A via the data 3, the second demodulation circuit 13a, is input to 13b. Of the demodulation circuits 13a and 13b, the interrogation signal (f) is directly input to the demodulation circuit 13a of one (here, the first demodulation circuit), and the demodulation circuit 13b of the other (here, the second demodulation circuit) is inputted. The interrogation signal (f) is input via the phase shifter 14 such that the interrogation signal (f) whose phase is advanced or delayed by 90 ° (π / 2) from the original interrogation signal (f) is input.

When demodulation processing is performed by the demodulation circuits 13a and 13b using the interrogation signal (f), the PN code (PN ₁ ,
PN ₂ ) is output. This output signal is input to the first and second correlators 16a and 16b via the band pass filters 15a and 15b, respectively. In addition,
The interrogation circuits 13a and 13b use different interrogation signals having a 90 ° phase shift.
The reason for demodulation is as follows. That is, receiving
The signal phase is twice the distance between transceivers A and B (this
Radio wave propagation delay time (called the effective transmission distance between receivers)
Will be shifted. The value of this deviation is “0” or
When the phase becomes the same as "1", it is demodulated with a part of the transmission signal.
The output becomes zero. 0 in phase detection
Phase detection of signals of ~ 180 ° is 0 output (DC separation)
This is the so-called dead zone.
This dead zone is the point at which the effective transmission distance repeats a multiple of the wavelength.
Will exist. To solve this, the transmitter A
The response signal received by the receiving unit a2 is
It is two signals whose phase of the interrogation signal is shifted by 90 °.
Each is demodulated. By performing such operations
Thus, the above-mentioned dead zone can be eliminated. That is, 9
The leak signal of the 0 ° transmission signal is the same as the DC component in any detection.
This is twice the component of the carrier. These are bandpass filters
It is removed by 15a and 15b. Next, from receiver B
The reflected signal is 0 ° and 180 °.
The phase at the center depends on the effective transmission distance.
Present as a bias value. 90 ° phase at receiver a2
Demodulate by two circuits (13a, 13b) with difference
Then, a signal comes out at either output. 45
° When input with out-of-phase inputs, the same
Output is obtained in size. The organization of these outputs will be described later.
This is performed by the 20 data regenerator of FIG. That is, the first
The output of the correlator 16a and the output of the second correlator 16b are respectively
When the square root is added and squared, the ideal output is obtained.
You.

The first and second correlators 16a and 16b have the same PN code as the _first PN code (PN ₁ ) and the _second PN code (PN ₂ ) in the third PN code generator 17a and the fourth PN code, respectively.
It is configured to be input from each of the code generators 17b.

[0023] Thus, from the first correlator 16a, the predetermined correlation value is obtained when the correlation and the 1PN code PN ₁ is taken, also, from the second correlator 16b correlation and the 2PN code PN ₂ Is obtained, a predetermined correlation value is obtained. This condition is indicated by the peak values in FIG.

The data "1,0,1,1" in FIG.
., "0, 1,..." Are the data "1, 0, 0, 1,.
Has nothing to do with. In this case, the peak value (correlation value) indicated by a dashed line is based on a signal received from another tag, and is removed by the next gating circuit.

When a plurality of tags are present, interference usually occurs, and separate reception becomes impossible. In the apparatus of this embodiment, the tags are asynchronous and have a high probability that the phases of the generated PN codes are different from each other. Therefore, a pair of gating circuits 17a,
Reference numeral 17b is connected to the output sides of the correlators 16a and 16b, respectively, and is configured to extract only a correlation value (peak value) every predetermined time. This predetermined time interval means that the data transmission timing of the tag B matches the transmission timing. Since the transmission timing is known, the operations of the two gating circuits 17a and 17b match the transmission timing. It is decided to. For example, a set of pulses corresponding to a multiple of the cycle time of PN1 is found out of the correlation output pulses 16a. This set corresponds to the response signal from the tag B and another tag B.

FIG. 3 shows a gate signal for finding out a set of response signals from one tag B indicated by a solid line among the signals of and. Also, is a gate signal for finding a set of response signals from another tag B, also indicated by a dashed line. As an actual circuit operation, a gate signal is generated by logical judgment from a signal pulse train in which both are mixed.

The data regenerator 20 is a microcomputer.
And a tag B and another tag B based on the values input from the two gating circuits 17a and 17b.
Data is reproduced by separating the data from each other, and the data is analyzed from the data, such as vehicle number and position data. Then, the head position and the tail position of the train A are calculated and transmitted to a subsequent train or a management center (not shown). Further, a leak signal from the transmitter to the receiving unit comes in as a leak in the circulator 3. This is a kind of distance problem in communication, but in this device, since the transmission signal is a line spectrum signal and the response signal from the tag is an SS signal, it can be easily rejected with good S / N. it can.

As described above, when the train position is detected using the transponder according to the present embodiment, the communication between the transmitter and the tag employs the SS communication, so that the near-far problem can be avoided and the noise can be avoided. Can be effectively removed to maintain a high-quality communication state, and accurate train position detection can be performed.

Since the receiver (tag) does not require a complicated PN code synchronizing circuit when the SS communication is adopted, it has a simple structure and can be implemented at low cost.

[0030]

The transponder according to the present embodiment employs SS communication for communication between the transmitter and the tag, so that a distance problem can be avoided and noise can be effectively removed to achieve a high quality communication state. Can be maintained. Also, response signals from a plurality of tags can be separated and received. Further, since the tag does not require a complicated PN code synchronization circuit when SS communication is employed, the tag has a simple structure and can be implemented at low cost.

[Brief description of the drawings]

FIG. 1 is a plan view when a transponder according to the present invention is applied to train detection.

FIG. 2 is a block diagram illustrating an electrical configuration of a transmitter and a tag.

FIG. 3 is a waveform diagram at a portion of FIG. 2;

[Explanation of symbols]

 A transmitter B receiver (tag) a1 transmitter a2 receiver 1 signal generator 6 modulation circuit 7 data generation circuit 8a, 8b AND circuit 9 inversion circuit 10a, 10b first and second PN code generator 12 OR circuit 13a, 13b First and second demodulation circuits 14 Phase shifters 16a and 16b First and second correlators 17a and 17b Gating circuit 20 Data regenerator

Claims (1)

(57) [Claims] 1. An interrogation signal having a predetermined frequency is transmitted from a transmission section of a transmitter to a receiver, and when the receiver receives the interrogation signal, a response signal including predetermined information is transmitted to the receiver. in a transponder for sending to the receiving part of the machine, the receiver forms a PN code generating means for generating a different first PN code及 beauty second PN code from each other, the predetermined information logic the value "1" and "0" in association with the selecting the first PN code及 beauty second PN code, modulating means that predetermined information in the selected PN code for spread spectrum modulation process Response signal generating means for generating the response signal by phase-modulating the phase of the received interrogation signal by 180 ° based on the signal modulated by the modulation means; and a receiving unit of the transmitter, Response signal Serial question signal and the interrogation signal
PN code extracting means for extracting a phase of 90 ° phase-shifted two signals in each demodulation process to the first PN code及 beauty second PN code, respectively, first extracted by said extracting means the second P of the PN code及 beauty
First PN code及 beauty second PN provided in advance with N code
A transponder for obtaining a correlation value between the two using a code and reproducing the predetermined information based on the obtained correlation value.