JP3349870B2 - Spread spectrum communication equipment for train control - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission signal (information signal).
Is spread-modulated with a pseudo-noise code having a spectrum width sufficiently wider than the transmission signal, a so-called PN code, and transmitted.
On the other hand, the present invention relates to a spread-spectrum communication device that performs spread-spectrum demodulation with the PN code on the receiving side and selectively receives only a transmission signal. In particular, it enables reduction of a correlation value due to leakage from another information source, Or that can be accurately distinguished.

[0002]

2. Description of the Related Art The present applicant has previously disclosed in Japanese Patent Application Laid-Open No. 5-2942.
No. 39, etc., in spread spectrum communication (hereinafter, referred to as
SS such as a train control communication device using SS communication)
A communication device is proposed. FIG. 5 is an example of a train detection device using the SS communication.

Each of the track circuits (three track circuits in the illustrated example for convenience) T1 to T3 has a phase difference θ1 to θ3 with a predetermined reference PN code (PN1 (θ0)) as shown in FIG.
PN code (PN1 (θ1)) generated with
(PN1 (θ3)) is assigned to the transmitter a and the receiver b.
It is configured so that communication can be performed with the communication device.

In the transmitter a, the carrier (fc) having a predetermined frequency generated by the carrier generator 1 is transmitted to the PN assigned to the track circuit T1. After being spread by the spreading circuit 2 using the code (PN1 (.theta.1)), it is transmitted to the starting end of the track circuit T1 via the transmission circuit 3 formed of an amplifier circuit and the like.

[0005] In the receiver b, the signal input from the terminal side of the track circuit T 1 is amplified by the receiving circuit 10 and then filtered by the band-pass filter 11. A part of the filtered signal is supplied to a PN code (PN1) from a PN code generation circuit (PNG) described later.
(Θ1)) is used in the despreading circuit 12 to perform despreading processing,
A signal including the carrier (fc) used on the transmitter a side is extracted.

The extracted signal is supplied to a bandpass filter 1
After being filtered at 3, the signal is processed by a processing circuit 14 formed by an amplifier circuit, a detection circuit, and the like, and a drive signal of the track relay TR is obtained.

When the track circuit T1 is not short-circuited by the axle (wheels) of the train, the track relay TR lifts the track circuit T because it can receive the carrier wave (fc) from the transmitter a.
When 1 is short-circuited on the axle of the train, it falls because the reception level of the carrier (fc) from the transmitter a side decreases. Therefore, the presence or absence of a train in the track circuit T1 can be detected based on the operation state of the track relay TR.

The P used in the despreading circuit 12
The N code (PN1 (θ1)) corresponds to the bandpass filter 11
Is generated using a part of the signal processed by That is, a part of the signal processed by the band-pass filter 11 is guided to the demodulation circuit 20 and demodulated using the same signal as the carrier (fc) used in the transmitter a, so that the PN code (PN1 ( θ1)) is extracted.

The extracted signal is supplied to a low-pass filter 21
Correlator (matched filter) after being filtered by
22. In this correlator 22, the same P as the PN code (PN1 (θ1)) used on the transmitter a side is used.
A correlation value is obtained using the N code (PN1 (θ1)),
When the correlation is obtained, the PNG 23 is output from the correlator 22.
Is supplied with a drive signal. Accordingly, the PNG 23 sends the PN code (P
PN code synchronized with N1 (θ1)) (PN1 (θ1))
Can be supplied.

[0010]

By the way, as described above, the same PN code (PN1) is used, and its phase position is assigned to each channel, that is, in the above example, to the SS assigned to each track circuit. In a communication device, different types of PN codes (PN1), (PN2),
The cross-correlation value can be reduced as compared with using (PN3).

However, the cross-correlation value is expressed as "1 / PN code (P
N1) ", which is not zero (eg, P
If the N code (PN1) is 7 bits in the embodiment described later, it becomes 1/7. ), If the level of the leak signal from another adjacent channel (track circuit) is high, there is a problem that the correlation value increases according to the level, which may hinder the distinction between the own signal and the other signal. There is.

The present invention has been made in order to solve the above-mentioned drawbacks, and has as its object to solve the problem even when the level of a leak signal from another adjacent channel is large.
An object of the present invention is to provide an SS communication device capable of reducing a correlation value.

[0013]

In order to achieve the above object, an SS communication apparatus according to the present invention includes a transmitter for spreading a predetermined communication signal using a predetermined PN code and transmitting the signal,
A train control SS comprising a receiver that receives a signal from the transmitter, performs despreading processing using the same PN code as the predetermined PN code, and receives a transmission signal from the transmitter.
In the communication device, the predetermined PN code used in the transmitter of one track circuit is the same reference PN code (PN1 (θ ) as the PN code used in the transmitter of another track circuit.
0)) PN whose phase is shifted by a predetermined pitch number
A code (PN1 (θ1)), the PN code used in the correlator of received <br/> signal unit of said one track circuit, before Symbol inverts the PN code used (PN1 (θ1)) at the transmitter PN sign (* PN1 (θ1)) (* means inversion)
Wherein it is characterized in that reference is a PN code (PN1 (θ0)) PN code obtained by adding the (PN'1 (θ1)) and.

[0014]

[Action] In the above structure, PN code used in the receiver of one track circuit, PN code used in the transmit unit
(PN1 (θ1)) inverted PN code (* PN1
(.Theta.1)) obtained by adding the (※ are mean inversion.) And standards PN marks <br/> No. (PN1 (.theta.0)) Monodea
You .

[0015]

Embodiments of the present invention will be described below with reference to the drawings. A schematic configuration diagram when the present invention device is applied to a track circuit is the same as FIG. 5 described above.
This will be described with reference to FIG. Therefore, description of each component in FIG. 5 is omitted.

The PN code (PN1) used in the transmitter a
(Θ1)) is the value of P used in the other track circuits T1 and T3.
The same reference PN code (PN1 (θ0)) synchronized with the N codes (PN2 (θ2)) and (PN3 (θ3)) is shifted in phase by several pitches and used (see FIG. 6).

Hereinafter, the track circuit T1 will be mainly described.
Now, as shown in FIG. 1, the reference PN code (PN1 (.theta.0)) is set to 7 of "11.sup.11-11-1-1".
As shown in FIG. 1, the PN code (PN1 (.theta.1)) assigned to the track circuit T1 has a bit configuration and is shifted by 3 bits from the phase of the reference PN code (PN1 (.theta.0)) as shown in FIG. -1 1 1 1 -1 ".

The despreading circuit 12 of the receiver b uses the same PN code (PN1 (θ1)) as the PN code (PN1 (θ1)) used in the transmitter a in synchronism with the transmitter. The signal (fc) from a can be extracted. Therefore, from the PNG 23, the despreading circuit 12
Is supplied with a PN code (PN1 (θ1)) synchronized with the PN code (PN1 (θ1)) on the transmitter a side.

The PNG 23 sends out the above-mentioned PN code (PN1 (θ1)) according to the drive signal from the correlator 22, and the drive signal is transmitted to the low-pass filter 2 by the correlator 22.
PN code (PN1) included in the signal input through
This signal is output when a correlation between (θ1)) and a PN code described later is obtained, that is, when the PN code on the transmitter a side is synchronized.

The PN code for obtaining the correlation used in the correlator 22 is, as shown in FIG. 1, the PN code (PN1 (θ1)) used in the transmitter a (see FIG. 1).
PN code (* PN1 (θ1)) with the sign reversed
Reference. Note that an asterisk means inversion. Hereinafter, it is called an inverted PN code. ) To the reference PN code (PN1 (θ
0)) and the PN code (PN1 '(θ1
)) (Hereinafter, this PN code (PN1 '(θ1)) is referred to as an additive PN code for convenience).

FIGS. 2 to 4 show that the use of the added PN code (PN1 '(. Theta.1)) enables a correlation value to be obtained without being affected by leakage signals from other track circuits (other channels). It will be described using FIG.

FIG. 2A shows a reference PN code (PN1).
This shows the correlation when (θ0) is shifted one bit at a time. In other words, a completely coincident state is obtained every 7-bit shift, and in the other 6-bit shifts, “−1”, that is, “3” bits match and “4” bits mismatch.

FIG. 2 (b) shows the state of the correlation value by graphing the above (a). When shifted one bit at a time in the horizontal axis direction, the correlation value is obtained every 7 bits. It is shown that. Here, assuming that the point at which the correlation value is obtained (the peak point in FIG. 2B) is “1”, the other portion is “− ／”.

FIG. 3 shows the correlation of the inverted PN code (* PN1 (θ1)) shown in FIG.
2 (a) corresponds to FIG. 2 (a), and FIG. 3 (b) corresponds to FIG. 2 (b).

FIG. 4 shows the correlation of the added PN code (PN1 '(θ1)) shown in FIG.
(A) corresponds to FIG. 2 (a) and FIG. 3 (a), and FIG. 4 (b) corresponds to FIG. 2 (b) and FIG. 3 (b). are doing.

As shown in the correlation column of FIG. 4 (a), "3" and "4" completely match every 3 bits and 4 bits, and "0" for other bits. Become. That is, the addition PN code (PN1 '
(Θ1)) is, as shown in FIG. 4B, a correlation value obtained by adding the correlation value A shown in FIG. 2B and the correlation value B shown in FIG. 3B. Become c. This correlation value C indicates “0”, “8”, and “−8”, unlike the conventional correlation value A indicating “−1” and “7”.

Therefore, as in this embodiment, the correlator 2
When the correlation is obtained using the additive PN code (PN1 '(θ1)) in 2, the value other than the autocorrelation is "0".
Even if there is a leak signal from the other track circuits T2 and T3, a drive signal for the PNG 23 can be generated without being affected by the leak signal. Therefore, only the own signal can be accurately received.

In the above-described embodiment, an example is shown in which the device of the present invention is applied to a track circuit.
Any method can be applied as long as the phase pitch of (θ0)) is shifted by a predetermined bit for each channel and SS communication is performed.

[0029]

In the train communication SS communication apparatus according to the present invention, the predetermined PN used in the transmitter of one track circuit is used.
The code is a PN used in the transmitter of another track circuit .
PN code phase shifted a predetermined number of pitches by the phase of the code with the same reference PN code (PN1 (θ0)) (PN1
(.Theta.1)) and is, PN code used by the correlator <br/> receiver of the one track circuit, before Symbol PN marks <br/> No. used in the transmitter the (PN1 (θ1)) Inverted PN code (* PN1
(Θ1)) (* means inversion) and the reference P
Since it is a PN code (PN'1 (? 1)) obtained by adding the N code (PN1 ( ? 0)) , leakage from a transmitter of another track circuit is performed. Even if there is a signal, a correlation value can be obtained without being affected by the leak signal, and the own signal can be received accurately.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a reference PN code, a PN code in which the phase of the reference PN code is shifted by three chips, an inverted PN code, and an addition PN code.

FIG. 2 is an explanatory diagram showing a correlation between reference PN codes.

FIG. 3 is an explanatory diagram showing a correlation between inverted PN codes.

FIG. 4 is an explanatory diagram showing a correlation between additive PN codes.

FIG. 5 is a schematic configuration diagram of a conventional device.

FIG. 6 is a table showing PN codes used in each transmitter.

[Description of Code] a Transmitter b Receiver T1 to T3 Orbit circuit 1 Carrier generation circuit 2 Spreading circuit 3 Transmission circuit 10 Receiving circuit 11, 13 Bandpass filter 12 Despreading circuit 14 Processing circuit 20 Demodulation circuit 21 Low-pass filter 22 Correlation Container 23 PNG

Claims (1)

(57) [Claims] A transmitter for spreading a predetermined communication signal by using a predetermined PN code and transmitting the spread signal, and receiving a signal from the transmitter and using the same PN code as the predetermined PN code. In a spread spectrum communication device for train control, comprising a receiver for performing despreading processing and receiving a transmission signal from the transmitter, a predetermined PN code used in the transmitter of one track circuit is used for another track circuit. PN code phase shifted a predetermined number of pitches by the phase of the same reference PN code and the PN code is also used in the transmitter (PN1 (θ0)) of (PN1 (.theta.1
)), And the PN code used by the correlator of the receiver of one track circuit, the PN code (PN1 from the previous SL transmitter (.theta.1
)) Inverted PN code (* PN1 (θ1)) (*
Means inversion. ) And the reference PN code (PN1)
(Θ0)) and PN code (PN'1)
(Θ1)) , a spread spectrum communication device for train control .