JP2000299679A - Transponder by spread spectrum communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly receive and process a data signal from each transponder by means of an interrogator by amplifying a signal, which is phase-modulate by a gain corresponding to the amplitude level of a signal extracted by a spreading code extracting means, so as to input to a correlation arithmetic means. SOLUTION: A signal outputted from an adder 12 is sent to the comparator 20 of an input conversion part 15' and sent also to a gain controller 25. The controller 25 detects the amplitude level of the signal, generates a controlling signal for controlling the operating state of a gain variable amplifier 24 so as to make a gain corresponding to the amplitude level and output the controlling signal to the amplifier 24. The amplifier 24 executes the amplifying processing of an output signal from a balanced modulator 21 in accordance with the control signal. Then, an amplified signal is sent to a band pass filter(BPF) 23 and fed back to the controller 25, and a BPF 23 removes unnecessary band components included in an amplitude signal and its signal is dent to a correlator 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transponder for performing communication using an microwave between an interrogator and a transponder, and more particularly to a transponder in which a plurality of transponders are spread spectrum in response to an interrogation signal from the interrogator. The present invention relates to a transponder based on a spread spectrum communication method for returning a transmitted data signal.

[0002]

2. Description of the Related Art Generally, a spread spectrum communication system is
A carrier modulated with a spread code (pseudo-noise code) having a spectrum width sufficiently wider than the information signal is modulated with an information signal and transmitted, and the receiving side selectively receives only a signal modulated with the spread code. It is a method. Since such a communication system selectively receives only a signal modulated by a specific spreading code, it has an excellent confidentiality and a function of removing various interference waves and noise. Further, from these functions, if signals modulated with different spreading codes are used in many communication channels, the same frequency band can be shared by each channel. When this spread spectrum communication method is introduced for a transponder using an interrogator and a transponder, by assigning different spreading codes to a plurality of transponders, data from each transponder is shared by one interrogator. You can expect to read at the time.

As a transponder of the above spread spectrum communication system, for example, a transponder having a configuration as shown in a block diagram of FIG. 3 is known. In the transponder of FIG. 3, an interrogation wave (interrogation signal) generated by the interrogation wave generator 10 of the interrogator 1 is transmitted via the antenna 11a. The plurality of transponders 3 ₁ , 3 _2, ... Receiving the interrogation wave transmitted from the interrogator 1 via the antenna 33a respond to the reception of the interrogation wave by converting the spread-spectrum data signal into a spread code generator. The interrogator 31 generates the interrogation wave according to the signal and modulates the interrogation wave by the modulator 32. In the interrogator 1 receiving signals from the responders 3 ₁ , 3 ₂ ... Via the antenna 11b,
In the multiplier 12, the interrogation wave is removed from the received signal by homodyne detection or the like, and a spreading code is extracted. The extracted spread code is input to the correlator 13 to perform a spread code identification process. Based on the identification result, the decoder 14 decodes data from the responders 3 ₁ , 3 ₂ . Is executed.

In the interrogator 1 described above, for example, when the correlator 13 is configured in an analog system such as a SAW convolver, the spread code extracted by the multiplier 12 is not directly input to the correlator 13. In many cases, the input is made via the input converter 15 shown by the broken line in FIG. The input converter 15 generates a signal obtained by phase-modulating a specific carrier using the spread code from the multiplier 12 as a modulation pulse, and outputs the signal to the correlator 13. As a device that performs this phase modulation, there is a balanced modulator that outputs one of an input signal (carrier) with a phase of 0 or π according to the positive or negative of the other signal (modulation pulse).

FIG. 4 is a diagram showing a circuit example of a conventional input converter 15 configured using a balanced modulator. In the circuit configuration of FIG. 4, the level of the spread code is determined by the comparator 20, and a binarized signal is input to the balanced modulator 21 as a modulation pulse according to the result. The balanced modulator 21 outputs a signal that has been phase-modulated using the modulated pulse and a predetermined carrier generated by the carrier generator 22. The output signal of the balanced modulator 21 is sent to the correlator 13 via a band pass filter (hereinafter, referred to as BPF) 23 having a required pass band.

[0006]

By the way, in the interrogator 1 of the conventional communication system as described above, when signals from a plurality of transponders 3 ₁ , 3 ₂ ... The signal extracted by removing the interrogation wave is obtained by adding a plurality of spreading codes. Therefore, the result of addition of each spreading code is reflected on the amplitude level of the extracted signal as shown in FIG.

However, when the carrier wave phase modulation is performed by the circuit shown in FIG. 4 using a signal reflecting the result of addition of the spread code, the signal output from the balanced modulator 21 is As shown in FIG. 5 (B), only the positive or negative information of the spreading code is reflected, and the amplitude level of the extracted signal is not reflected. Such a signal is BP
When input to the correlator 13 via F23, the plurality of spreading codes received at the same time mutually affect each other as noise. At this time, if the amplitude of the spread code is not reflected on the signal input to the correlator 13 as described above, the degree of influence is further increased, and as a result, signals from a plurality of transponders are received at the same time. The problem is that the discrimination performance at the time deteriorates.

The present invention has been made in view of the above points. Even when the interrogator receives the spread spectrum signals returned from a plurality of transponders at the same time, the data signal from each transponder is received. It is an object of the present invention to provide a transponder based on a spread spectrum communication system in which an interrogator can receive and process correctly.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an interrogator for transmitting an interrogation signal and, when receiving the interrogation signal from the interrogator, using a predetermined spread code using a spread spectrum code. A plurality of transponders that return the processed data signal to the interrogator, and a transponder based on a spread spectrum communication system including the interrogator,
Spreading code extracting means for receiving signals from the plurality of transponders and extracting a spreading code from the received signals, and analog calculating means for calculating a correlation value between the input signal and a preset reference spreading code An input conversion unit that generates a signal obtained by phase-modulating a predetermined carrier based on the signal extracted by the spread code extraction unit and inputs the signal to the correlation operation unit,
Wherein the input converting means amplifies the phase-modulated signal by a gain corresponding to the amplitude level of the signal extracted by the spreading code extracting means and inputs the amplified signal to the correlation calculating means. is there.

[0010] In this configuration, in response to the interrogation signal transmitted from the interrogator, the data signal subjected to the spread spectrum processing is returned from the plurality of transponders to the interrogator. In the interrogator that has received the signal returned from each transponder, the spread code component included in the received signal is extracted by the spread code extraction means and sent to the input conversion means. The input conversion means generates a signal obtained by phase-modulating a predetermined carrier based on the signal from the spread code extraction means, and generates a signal corresponding to the amplitude level of the signal from the spread code extraction means. And then sent to the correlation calculation means.
The correlation calculating means calculates a correlation value with a preset reference spreading code using the signal sent from the input converting means as an input signal, and calculates data transmitted from each transponder based on the calculated correlation value. Signal recognition processing is performed. Thus, even when the interrogator receives signals from a plurality of transponders at the same time, a signal corresponding to the added spread code is input to the correlation operation unit, and accurate operation processing is performed. .

Further, as a specific configuration of the input conversion means, a modulation pulse generation section for generating a binarized modulation pulse in accordance with the amplitude level of the signal extracted by the spread code extraction means, A balanced modulation section that generates a phase modulation signal by multiplying the modulation pulse from the modulation pulse generation section by the predetermined carrier, and a variable gain amplification section that amplifies the phase modulation signal generated by the balanced modulation section And a control unit that detects the amplitude level of the signal extracted by the spread code extraction unit and controls the gain of the amplification unit in accordance with the detection result.

In this configuration, the signal extracted by the spread code extraction means is sent to the modulation pulse generation unit and the control unit of the input conversion means. The modulation pulse generation section generates a modulation pulse, and the modulation pulse is multiplied by a predetermined carrier in the balanced modulation section to generate a phase modulation signal that does not reflect the result of adding the spreading code. At the same time, the control section detects the amplitude level of the signal from the spread code extracting means, and generates a control signal for controlling the variable gain of the amplification section to one corresponding to the amplitude level. Then, the phase modulation signal generated by the balanced modulation unit is sent to the amplification unit whose gain is controlled by the control unit and is amplified.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. The basic configuration of the transponder using the spread spectrum communication method according to the present embodiment is the same as the configuration of the conventional communication system shown in FIG. 3 described above. And a plurality of transponders 3 ₁ , 3 _2, ... Which return data signals subjected to spread spectrum processing in response to the interrogation wave. The feature of this embodiment lies in that the input converter 15 of the interrogator 1 is improved as described below.

The transponder having such a basic configuration is, for example, an interrogator 1 and transponders 3 ₁ , 3 ₂ .
Is suitable as a railway transponder or the like installed on the ground such as in a station yard or on a train. However, the transponder of the present invention is not limited to railway use.

FIG. 1 is a block diagram showing a configuration of an input converter of an interrogator 1 which is a feature of the present embodiment. However, the same parts as those of the configuration of the conventional input conversion unit 15 are denoted by the same reference numerals.

In FIG. 1, an input converter 1 according to the present embodiment is shown.
The configuration of 5 ′ is different from the conventional input converter 15 (FIG. 4) in that a variable gain amplifier 24 as an amplifier is provided between the balanced modulator 21 and the BPF 23 and the amplification of the variable gain amplifier 24 is performed. The point is that a gain controller 25 is provided as a control unit for controlling the operation. The configuration of the input conversion unit 15 ′ other than the above is the same as the configuration of the conventional input conversion unit 15.

Here, the multiplier 12 of the interrogator 1 corresponds to the spreading code extracting means, the correlator 13 corresponds to the correlation calculating means, and the input converter 15 'corresponds to the input converting means. Further, the comparator 20 of the input converter 15 'functions as a modulation pulse generator, and the balanced modulator 21 functions as a balanced modulator.

The variable gain amplifier 24 includes the balanced modulator 2
1 is a general amplifier that amplifies the phase modulation signal output from 1 and outputs the amplified signal to the BPF 23.
Is variable.

The gain controller 25 controls the variable gain amplifier 2 based on the spread code extracted by the multiplier 12.
4 to generate a control signal for controlling the gain of No. 4.
Specifically, a part of the signal output from the multiplier 12 is input, the amplitude level of the input signal is detected, a control signal having a gain corresponding to the amplitude level is generated, and the variable gain amplifier 24 Output to The gain controller 25 has a function of constantly monitoring the output level of the variable gain amplifier 24 and reflecting the monitoring result on the control of the variable gain amplifier 24.

Next, the operation of this embodiment will be described. First, in this transponder, an interrogation wave (interrogation signal) is generated by the interrogation wave generator 10 of the interrogator 1 and the antenna 11
are transmitted to the outside via a, and the interrogation waves are received by the transponders 3 ₁ , 3 _2, ... near the interrogator 1. Each of the transponders 3 ₁ , 3 _2, ... Generates a predetermined spread code set for each transponder in response to the interrogation wave from the interrogator 1, and the spread code is The signal is sent from the spreading code generator 31 to the modulator 32 in accordance with the signal. Modulator 3
In 2, the interrogation wave received by the antenna 33a is modulated according to the signal from the spreading code generator 31, and
Is returned to the interrogator 1 via. Note that the antenna 33a
And 33b can be the same.

In the interrogator 1, the signals returned from the responders 3 ₁ , 3 ₂ ... Are received by the antenna 11b and sent to the multiplier 12. The multiplier 12 removes the interrogation wave included in the reception signal by multiplying the reception signal by the interrogation wave from the interrogation wave generation circuit 10 and performs a spreading code extraction process. Since the spreading code extracted by the multiplier 12 indicates the sum of the respective spreading codes of the transponders 3 ₁ , 3 ₂ ..., The amplitude level of the extracted signal is
As shown in FIG. 2A, the result of adding the respective spreading codes is reflected.

The signal output from the multiplier 12 is sent to the comparator 20 of the input converter 15 'and also sent to the gain controller 25. Comparator 20
Then, as in the case of the conventional interrogator, a signal (modulation pulse) binarized into positive or negative according to the amplitude level of the input signal is generated, and the modulated pulse is output to the balanced modulator 21. The balanced modulator 21 outputs a signal that is phase-modulated using the carrier and the modulation pulse from the carrier generator 22. The signal output from the balanced modulator 21 reflects only the positive or negative information of the received spread code.

On the other hand, the gain controller 25 detects the amplitude level of the signal from the multiplier 12 and adjusts the gain of the variable gain amplifier 2 so that the gain corresponds to the amplitude level.
4 is generated, and the control signal is output to the variable gain amplifier 24.

In the variable gain amplifier 24, the balanced modulator 21 is controlled in accordance with a control signal from the gain controller 25.
Is amplified. The gain at this time corresponds to the amplitude level extracted by the multiplier 12, and the signal output from the variable gain amplifier 24 to the BPF 23 has a waveform as shown in FIG.

The signal amplified by the variable gain amplifier 24 is sent to the BPF 23 having a required pass band and is fed back to the gain controller 25. In the BPF 23, unnecessary band components included in the amplified signal are removed, and the signal is sent to the correlator 13. In the correlator 13, a correlation value with the reference spreading code is calculated based on the signal on which the amplitude level of the received spreading code is reflected, and a signal indicating the correlation value is sent to the decoder 14. The decoder 14 decodes the data from the transponders 3 ₁ , 3 ₂ ... Based on the signal from the correlator 13.

As described above, according to the present embodiment, the input converter of the interrogator 1 that receives the signals subjected to the spread spectrum processing returned from the plurality of transponders 3 ₁ , 3 ₂ . 24 and gain controller 2
5 is provided so that the amplified signal reflecting the amplitude level of the signal generated by the multiplier 12 is input to the correlator 13 so that the signals from the plurality of transponders 3 ₁ , 3 ₂ . Even when received at the time, it is possible to reduce the degree to which the respective spreading codes of the transponders 3 ₁ , 3 ₂ ... Affect each other. This makes it possible to realize a transponder based on the spread spectrum communication method in which the data signals simultaneously returned from the plurality of transponders 3 ₁ , 3 ₂ ... Can be correctly received and processed by one interrogator 1.

In the above-described embodiment, the input signal to the correlator 13 is phase-modulated using the balanced modulator 21. However, the present invention is not limited to this. Using different known modulators, the correlator 13
May be phase-modulated.

[0028]

As described above, according to the transponder using the spread spectrum communication method of the present invention, the input conversion means of the interrogator is phase modulated by the gain corresponding to the amplitude level of the signal extracted by the spread code extraction means. By amplifying the signal, even if the interrogator receives signals from multiple transponders at the same time, the mutual influence of multiple spreading codes is reduced, so that multiple transponders respond simultaneously. The received data signal can be accurately received and processed by one interrogator.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of an input converter of an interrogator according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the embodiment,
(A) shows an example of the waveform of the signal generated by the multiplier,
(B) is a diagram showing an example of a waveform of a signal output from the variable gain amplifier.

FIG. 3 is a diagram showing a configuration of a transponder based on a conventional spread spectrum communication system.

FIG. 4 is a block diagram showing a circuit configuration of an input converter applied to a conventional interrogator when a correlator is of an analog type.

FIG. 5 is a diagram for explaining the operation of a conventional interrogator;
(A) shows an example of the waveform of the signal generated by the multiplier,
(B) is a diagram showing an example of a waveform of a signal output from the balanced modulator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Interrogator 3 ₁ , 3 ₂ ... Transponder 10 Interrogator generator 11a, 11b, 33a, 33b Antenna 12 Multiplier 13 Correlator 14 Decoder 15, 15 'Input conversion unit 20 Comparator 21 Balanced modulator 22 Carrier generator 23 Band Pass Filter (BPF) 24 Variable Gain Amplifier 25 Gain Controller 31 Spread Code Generator 32 Modulator

Claims (2)

[Claims] An interrogator for transmitting an interrogation signal, and a plurality of responses for returning a data signal subjected to spread spectrum processing using a predetermined spreading code to the interrogator when the interrogation signal is received from the interrogator. A transponder based on a spread spectrum communication system comprising: a transponder, wherein the interrogator receives signals from the plurality of transponders,
A spreading code extracting means for extracting a spreading code component from the received signal; an analog correlation calculating means for calculating a correlation value between the input signal and a preset reference spreading code; and a spread code extracting means. Input conversion means for generating a signal obtained by phase-modulating a predetermined carrier based on the signal and inputting the signal to the correlation operation means, wherein the input conversion means outputs the amplitude level of the signal extracted by the spread code extraction means. A transponder based on a spread spectrum communication system, wherein the phase-modulated signal is amplified by a gain corresponding to the above and input to the correlation calculating means. 2. A modulation pulse generator for generating a binarized modulation pulse in accordance with an amplitude level of a signal extracted by the spread code extraction unit, wherein the input conversion unit includes: A balanced modulation unit that generates a phase modulation signal using a modulation pulse and the predetermined carrier; a variable gain amplification unit that amplifies the phase modulation signal generated by the balanced modulation unit; The transponder according to claim 1, further comprising: a control unit that detects an amplitude level of the detected signal and controls a gain of the amplification unit in accordance with the detection result.