JP2021190842A - Transmission/reception system - Google Patents

Abstract

To provide a transmission/reception system that can improve an S/N ratio on a reception side without increasing the size of a facility on a transmission side and significantly increasing costs.SOLUTION: A vehicle detection system, which is an example of a transmission/reception system, includes: an on-vehicle transmission device 10 that transmits a vehicle detection signal containing a plurality of amplitude-modulated waves with different carrier wave frequencies from each other that are amplitude-modulated by modulated waves of the same frequency; and a ground receiver 40 that receives the vehicle detection signal via a loop coil LC, extracts the modulated waves from the respective amplitude-modulated waves, and performs a process corresponding to a total level obtained by totaling levels of the extracted modulated waves.SELECTED DRAWING: Figure 1

Description

The present invention relates to a transmission / reception system having a transmitting device for transmitting a signal and a receiving device for receiving the signal.

As an example of the transmission / reception system, in Patent Document 1, an on-board device (corresponding to a transmission device) provided on a train traveling on a track transmits a train detection signal via an on-board antenna, and the transmitted train detection signal is transmitted. Described is a technique in which a ground device (corresponding to a receiving device) provided on the ground receives the signal via a loop coil arranged along the track.

In the technique described in Patent Document 1, the train detection signal is composed of an amplitude-modulated wave in which a carrier wave having a predetermined frequency is amplitude-modulated by a modulated wave. Further, the ground device is configured to detect that the train exists in the section corresponding to the loop coil by receiving the train detection signal.

Japanese Unexamined Patent Publication No. 2008-13043

Since the loop coil is not covered with a metal shield or the like, it also receives noise. Therefore, when the noise increases, the S / N ratio between the train detection signal and the noise in the ground device decreases, and false detection of the presence / absence of the train in the section corresponding to the loop coil is induced. There is a risk. As a countermeasure, conventionally, the train detection signal is significantly amplified and / or the number of on-board antennas is increased to increase the reception level of the train detection signal in the ground device, thereby increasing the reception level of the train detection signal. The decrease in the S / N ratio between the train detection signal and the noise in the apparatus was prevented.

However, such measures lead to an increase in the size of the equipment on the train side (that is, the equipment on the transmitting side) and a significant cost increase. Therefore, the S of the train detection signal (that is, the reception signal) and the noise in the ground device (that is, the reception side) is not caused by the increase in size of the equipment on the train side (equipment on the transmission side) and the significant cost increase. It is required to improve the / N ratio.

It should be noted that such a request, that is, a request for improving the S / N ratio between the received signal and noise on the receiving side without causing an increase in the size of equipment on the transmitting side and a significant cost increase, is a train detection signal. It is not limited to the case of transmitting and receiving, but also exists in the case of transmitting and receiving signals other than the train detection signal.

Therefore, an object of the present invention is to provide a transmission / reception system capable of improving the S / N ratio between the received signal and noise on the receiving side without inviting an increase in size of equipment on the transmitting side and a significant cost increase. And.

According to one aspect of the present invention, the transmission / reception system receives a transmission device including a plurality of amplitude-modulated waves having different carrier frequency and are amplitude-modulated by modulation waves of the same frequency, and the plurality of received signals. It has a receiving device that extracts a modulated wave from the amplitude-modulated wave of the above and performs processing according to the total level of the summed levels of the extracted modulated waves.

According to the present invention, it is possible to provide a transmission / reception system capable of improving the S / N ratio between the received signal and noise on the receiving side without causing an increase in size of equipment on the transmitting side and a significant cost increase. ..

It is a figure which shows the schematic structure of the vehicle detection system which concerns on one Embodiment of the transmission / reception system of this invention. It is a block diagram which shows the structure of the on-vehicle transmission device of the vehicle detection system. It is a figure which shows the generation process of the vehicle detection signal in the on-vehicle transmission device, (a) shows a carrier wave, (b) shows a modulated wave, (c) is generated by amplitude-modulating a carrier wave by a modulated wave. The amplitude-modulated wave is shown, and (d) shows the vehicle detection signal. It is a block diagram which shows the structure of the ground transmission device of the vehicle detection system. It is a block diagram which shows the structure of the ground receiver of the vehicle detection system. It is a block diagram which shows the structure of the conventional on-vehicle transmission device. It is a figure which shows the generation process of a vehicle detection signal in a conventional on-vehicle transmission device, (a) shows a carrier wave, (b) shows a modulated wave, (c) is generated by amplitude-modulating a carrier wave by a modulated wave. The amplitude-modulated wave (vehicle detection signal) is shown. It is a block diagram which shows the structure of the conventional ground receiver. It is a figure for demonstrating the modification of the ground receiving device of the vehicle detection system. It is a block diagram which shows the structure of the on-vehicle transmission device of the vehicle detection system which concerns on other embodiment. It is a figure which shows the example of the amplitude modulation wave and the vehicle detection signal generated by the on-board transmission device of the vehicle detection system which concerns on another embodiment, and (a) is a figure which the vehicle detection signal is composed of three amplitude modulation waves. (B) shows the case where the vehicle detection signal is composed of five amplitude-modulated waves. It is a block diagram which shows the structure of the ground receiver of the vehicle detection system which concerns on other embodiment. It is a figure which shows the relationship between the number of amplitude modulation waves constituting the vehicle detection signal transmitted from the on-vehicle transmission device, and the reception level of a vehicle detection signal in a ground receiver.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a diagram showing a schematic configuration of a vehicle detection system according to an embodiment of the transmission / reception system of the present invention. As shown in FIG. 1, the vehicle detection system (transmission / reception system) according to the embodiment includes an on-vehicle transmission device (transmission device) 10 mounted on a vehicle V traveling on a travel path R in the direction of arrow A, and a vehicle V. An on-board antenna 20 provided in the lower part of the front side of the vehicle, a plurality of loop coil LCs installed along the traveling path R, a ground transmission device 30 connected to each of the plurality of loop coil LCs, and a plurality of loop coils. It has a ground receiver (receiver) 40 connected to each of the LCs.

The on-vehicle transmission device 10 is configured to generate a vehicle detection signal and transmit the generated vehicle detection signal via the on-vehicle antenna 20. Each of the plurality of loop coils LC is provided corresponding to the closed section set in the traveling path R. In other words, each loop coil LC section in the travel path R constitutes each closed section in the travel path R. The ground transmission device 30 is connected to the vehicle approach side of the loop coil LC. However, the present invention is not limited to this, and the ground transmission device 30 may be connected to the vehicle advance side of the loop coil LC. The ground transmission device 30 is configured to generate a disconnection detection signal and transmit the generated disconnection detection signal to the loop coil LC. The ground receiver 40 is connected to the vehicle advance side of the loop coil LC. However, the present invention is not limited to this, and the ground receiving device 40 may be connected to the vehicle approach side of the loop coil LC. The ground receiving device 40 is configured to receive a vehicle detection signal and a disconnection detection signal from the loop coil LC. In the following description of the terrestrial transmitting device 30 and the terrestrial receiving device 40, the loop coil LC to which the terrestrial transmitting device 30 or the terrestrial receiving device 40 is connected is referred to as a “corresponding loop coil LC”. ..

FIG. 2 is a block diagram showing the configuration of the on-vehicle transmission device 10. As shown in FIG. 2, in the present embodiment, the on-board transmission device 10 includes a carrier wave generation unit 11, a modulated wave generation unit 12, a modulation unit 13, a synthesis unit 14, and an amplification unit 15.

The carrier wave generation unit 11 generates two carrier waves having different frequencies from each other. In the present embodiment, the carrier wave generation unit 11 includes a first carrier wave generation circuit 111 that generates a carrier wave having a frequency of f1 (hereinafter referred to as “first carrier wave f1”) and a carrier wave having a frequency of f2 (hereinafter referred to as “second carrier wave f2”). A second carrier wave generation circuit 112 that generates (referred to as) is included. The two carrier waves (first carrier wave f1 and second carrier wave f2) generated by the carrier wave generation unit 11 (first carrier wave generation circuit 111 and second carrier wave generation circuit 112) are sent to the modulation unit 13.

The modulated wave generation unit 12 produces a square wave having a period of T (frequency is fm = 1 / T) and a ratio of the mark portion M to the space portion S (hereinafter referred to as “mark space ratio”) of 1: 1. It is generated as a modulated wave fm. However, the present invention is not limited to this, and the modulated wave generation unit 12 may generate a trapezoidal wave having a period of T and a mark space ratio of 1: 1 as the modulated wave fm. The modulated wave fm generated by the modulated wave generation unit 12 is sent to the modulation unit 13.

The modulation unit 13 sequentially modulates the two carrier waves (first carrier wave f1 and second carrier wave f2) generated by the carrier wave generation unit 11 with the modulation wave fm generated by the modulation wave generation unit 12 to generate two amplitude modulated waves. do. In the present embodiment, the modulation unit 13 includes a first modulation circuit 131 and a second modulation circuit 132. The first modulation circuit 131 generates the first amplitude modulation wave F1 by amplitude-modulating the first carrier wave f1 generated by the first carrier wave generation circuit 111 with the modulation wave fm. The second modulation circuit 132 amplitude-modulates the second carrier wave f2 generated by the second carrier wave generation circuit 112 by the modulation wave fm delayed by a half cycle (T / 2) in the delay circuit 141 to obtain the second amplitude modulation wave F2. Generate. The two amplitude modulation waves (first amplitude modulation wave F1 and second amplitude modulation wave F2) generated by the modulation unit 13 (first modulation circuit 131 and second modulation circuit 132) are sent to the synthesis unit 14.

The synthesizing unit 14 synthesizes two amplitude-modulated waves (first amplitude-modulated wave F1 and second-amplitude-modulated wave F2) generated by the modulation unit 13 to generate a vehicle detection signal.

The amplification unit 15 amplifies the vehicle detection signal (combined wave of the first amplitude modulated wave F1 and the second amplitude modulated wave F2) generated by the synthesis unit 14. Then, the vehicle detection signal amplified by the amplification unit 15 is transmitted to the loop coil LC via the on-board antenna 20.

FIG. 3 is a diagram showing a process of generating a vehicle detection signal in the on-vehicle transmission device 10. FIG. 3A shows a carrier wave (first carrier wave f1 generated by the carrier wave generation unit 11 and second carrier wave f2), and FIG. 3B shows a modulated wave (modulated wave fm generated by the modulated wave generation unit 12). And a half-period (T / 2) delayed modulation wave fm), FIG. 3 (c) shows an amplitude modulation wave (first amplitude modulation wave F1, second) generated by amplitude-modulating a carrier wave with a modulation wave. Amplitude-modulated wave F2) is shown, and FIG. 3D shows a vehicle detection signal (composite wave of a first amplitude-modulated wave F1 and a second amplitude-modulated wave F2).

As shown in FIGS. 3A to 3D, the vehicle detection signals transmitted from the on-board transmitter 10 via the on-board antenna 20 are amplitude-modulated by the same modulated wave fm and have different carrier frequencies. Includes two amplitude modulated waves. Specifically, in the present embodiment, the vehicle detection signal has a first amplitude modulated wave F1 having a period of T and a mark space ratio (M: S) of 1: 1 and a mark having a period of T. This is a combined wave with the second amplitude modulated wave F2 having a space ratio (M: S) of 1: 1. Here, the modulated wave fm that modulates the second carrier wave f2 is delayed by a half cycle (T / 2), and the second amplitude modulated wave F2 has a half cycle (T / 2) with respect to the first amplitude modulated wave F1. ) It has been shifted. Therefore, in the vehicle detection signal, the other mark portion M is arranged in one space portion S of the first amplitude modulated wave F1 and the second amplitude modulated wave F2.

In the present embodiment, the mark portion M of the amplitude-modulated wave means a portion where the carrier wave exists in the amplitude-modulated wave, and the space portion S of the amplitude-modulated wave means that the carrier wave does not substantially exist in the amplitude-modulated wave. A portion (a portion where the carrier wave does not exist or the amplitude of the carrier wave is significantly smaller than that of the mark portion M). Therefore, the mark portion M of the first amplitude modulation wave F1 can be referred to as a carrier wave (first carrier wave f1) in the first amplitude modulation wave F1, and the mark portion M of the second amplitude modulation wave F2 is in the second amplitude modulation wave F2. It can also be called a carrier wave (second carrier wave f2).

FIG. 4 is a block diagram showing the configuration of the terrestrial transmission device 30. As shown in FIG. 4, in the present embodiment, the ground transmission device 30 has a disconnection detection signal generation unit 31 that generates a disconnection detection signal, and corresponds to the disconnection detection signal generated by the disconnection detection signal generation unit 31. It is transmitted to the loop coil LC. The disconnection detection signal is a signal for detecting the presence or absence of disconnection of the loop coil LC, and is not particularly limited, but is a signal having a frequency different from that of the first carrier wave f1, the second carrier wave f2, and the modulated wave fm. In the present embodiment, the disconnection detection signal is a signal having a frequency of fd, and is hereinafter referred to as “disconnection detection signal fd”.

Here, although detailed description is omitted, as shown by the broken line in FIG. 4, the ground transmission device 30 further includes a speed limiting signal generation unit 32, an amplification unit 33, and a synthesis unit 34, and speed limiting signal generation. The speed limiting signal generated by the unit 32 and amplified by the amplification unit 33 may be configured to be transmitted to the corresponding loop coil LC together with the broken line detection signal fd. In this case, the speed limiting signal is, for example, an amplitude modulated wave generated by amplitude-modulating a predetermined carrier wave with a modulated wave assigned to each speed limiting information, and is a vehicle traveling in a section of the corresponding loop coil LC. It is transmitted to the on-board control device (not shown) of V. The frequency of the predetermined carrier wave is different from the frequency of the first carrier wave f1, the second carrier wave f2, and the disconnection detection signal fd, and the frequency of the modulated wave assigned to each speed limiting information is used in the on-board transmission device 10. It is different from the frequency of the modulated wave fm to be obtained.

FIG. 5 is a block diagram showing the configuration of the ground receiving device 40. As shown in FIG. 5, in the present embodiment, the ground receiving device 40 includes a separation unit 41, a demodulation processing unit 42, an addition unit 43, a first processing unit 44, and a disconnection determination unit 45.

The separation unit 41 separates each amplitude modulated wave (first amplitude modulated wave F1, second amplitude modulated wave F2) and disconnection detection signal fd from the signal received from the corresponding loop coil LC (hereinafter, simply referred to as “received signal”). do. In the present embodiment, the separation unit 41 includes a plurality of BPFs (bandpass filters) to which the received signal is input, specifically, a bPF 410 for fd, a BPF 411 for f1, and a BPF 412 for f2.

The fd BPF410 is a filter that passes through the frequency band of the disconnection detection signal fd, the f1 BPF411 is a filter that passes through the frequency band of the first carrier wave f1, and the f2 BPF412 is the frequency band of the second carrier wave f2. It is a filter that passes through. That is, the fd BPF410 passes through the disconnection detection signal fd included in the received signal, the f1 BPF411 passes through the first amplitude modulated wave F1 included in the received signal, and the f2 BPF412 passes through the received signal. The second amplitude modulated wave F2 included in is passed through. The output of the fd BPF 410 (that is, the disconnection detection signal fd) is sent to the disconnection determination unit 45. On the other hand, the output of the f1 BPF411 (that is, the first amplitude modulated wave F1) and the output of the f2 BPF412 (that is, the second amplitude modulated wave F2) are sent to the demodulation processing unit 42.

The demodulation processing unit 42 demodulates each amplitude-modulated wave (first amplitude-modulated wave F1 and second-amplitude-modulated wave F2) separated by the separation unit 41. Furthermore, the demodulation processing unit 42 demodulates each amplitude modulated wave separated by the separation unit 41, extracts the modulated wave from each amplitude modulated wave, and converts each extracted modulated wave into DC (converts to DC). ) Is configured. In the present embodiment, the demodulation processing unit 42 includes a first demodulation processing unit 42A and a second demodulation processing unit 42B.

The first demodulation processing unit 42A includes a first demodulation circuit 421A, a first fm BPF422A, and a first detection smoothing circuit 423A. The first demodulation circuit 421A demodulates the first amplitude modulated wave F1 which is the output of the BPF 411 for f1. The BPF422A for the first fm is a filter that passes through the frequency band of the modulated wave fm. The first detection smoothing circuit 423A detects and smoothes the output of the first fm BPF422A. When the demodulation result of the first amplitude modulated wave F1 by the first demodulation circuit 421A passes through the first fm BPF422A, the modulated wave fm is taken out from the first amplitude modulated wave F1 and further passes through the first detection smoothing circuit 423A. As a result, the modulated wave fm extracted from the first amplitude modulated wave F1 is converted (converted to DC) into DC. The DC-converted modulated wave fm (output of the first detection smoothing circuit 423A) is sent to the adder 43.

The second demodulation processing unit 42B includes a second demodulation circuit 421B, a second fm BPF422B, and a second detection smoothing circuit 423B. The second demodulation circuit 421B demodulates the second amplitude modulated wave F2 which is the output of the BPF412 for f2. The second fm BPF422B is a filter that passes the frequency band of the modulated wave fm. The second detection smoothing circuit 423B detects and smoothes the output of the second fm BPF422B. When the demodulation result of the second amplitude modulated wave F2 by the second demodulation circuit 421B passes through the second fm BPF422B, the modulated wave fm is taken out from the second amplitude modulated wave F2 and further passes through the second detection smoothing circuit 423B. As a result, the modulated wave fm extracted from the second amplitude modulated wave F2 is converted into DC. The DC-converted modulated wave fm (output of the second detection smoothing circuit 423B) is sent to the adder 43.

The addition unit 43 sends from the first demodulation processing unit 42A the DC-converted modulated wave fm (that is, the modulated wave fm taken out from the first amplitude modulation wave F1) and the second demodulation processing unit 42B. The DC-converted modulated wave fm (that is, the modulated wave fm extracted from the second amplitude modulated wave F2) is added. The addition result by the addition unit 43 is sent to the first processing unit 44.

The first processing unit 44 executes processing according to the level of the addition result by the addition unit 43. Specifically, in the present embodiment, the first processing unit 44 monitors the level of the addition result by the addition unit 43 as the reception level of the vehicle detection signal. Then, the first processing unit 44 determines that the level of the addition result by the addition unit 43 is equal to or higher than the predetermined first threshold value, in other words, the reception level of the vehicle detection signal is equal to or higher than the determination level. Since the vehicle detection signal has been received, it is determined that the vehicle V exists in the corresponding loop coil LC section (closed section) on the travel path R. In this case, the first processing unit 44 outputs information indicating that the vehicle V exists in the section (closed section) of the corresponding loop coil LC in the traveling path R. The information output by the first processing unit 44 is used, for example, in the logic for determining the speed limit information outside the section (closed section) of the corresponding loop coil LC, and / or by a transmitter (not shown) or the like. It is transmitted to an external device (a vehicle management device that manages all vehicles traveling on the travel path R, etc.).

On the other hand, the first processing unit 44 has a vehicle detection signal when the level of the addition result by the addition unit 43 is less than the first threshold value, in other words, when the reception level of the vehicle detection signal is less than the determination level. Is not received, so it is determined that the vehicle V does not exist in the corresponding loop coil LC section (closed section) on the travel path R. In this case, the first processing unit 44 does not perform any further processing. However, the present invention is not limited to this, and the first processing unit 44 may output information indicating that the vehicle V does not exist in the corresponding loop coil LC section (closed section) in the travel path R.

The disconnection determination unit 45 determines that there is no disconnection in the loop coil LC when the signal level of the disconnection detection signal fd is equal to or higher than the second threshold value, and when the signal level of the disconnection detection signal fd is less than the second threshold value. Is determined to have a disconnection in the loop coil LC. Then, when the disconnection determination unit 45 determines that the loop coil LC has a disconnection, the disconnection determination unit 45 outputs information indicating that the disconnection has occurred in the loop coil LC. The information output by the disconnection determination unit 45 is transmitted to the external device in the same manner as the information output by the first processing unit 44.

Next, the operation and effect of the vehicle detection system according to the embodiment having the above configuration will be described in comparison with the conventional vehicle detection system. First, the conventional vehicle detection system will be briefly described with reference to FIGS. 6 to 8. However, the description of the configuration common to the vehicle detection system according to the above-described embodiment will be omitted as appropriate.

FIG. 6 is a block diagram showing a configuration of an on-board transmission device (hereinafter referred to as “conventional on-board transmission device”) 50 of a conventional vehicle detection system. As shown in FIG. 6, the conventional on-board transmission device 50 includes a carrier wave generation circuit 51, a modulation wave generation circuit 52, a modulation circuit 53, and an amplifier circuit 54.

The carrier wave generation circuit 51 generates a carrier wave (carrier wave f0) having a frequency of f0. Similar to the modulated wave generation unit 12, the modulated wave generation circuit 52 generates a square wave having a period of T (frequency fm = 1 / T) and a mark space ratio of 1: 1 as the modulated wave fm. The modulation circuit 53 generates a vehicle detection signal (amplitude modulation wave F0) by amplitude-modulating the carrier wave f0 generated by the carrier wave generation circuit 51 with the modulation wave fm generated by the modulation wave generation circuit 52. The amplifier circuit 54 amplifies the vehicle detection signal (amplitude modulation wave F0) generated by the modulation circuit 53. Then, the vehicle detection signal amplified by the amplifier circuit 54 is transmitted to the loop coil LC via the on-board antenna 20.

FIG. 7 is a diagram showing a process of generating a vehicle detection signal in the conventional on-vehicle transmission device 50. 7 (a) shows the carrier wave f0, FIG. 7 (b) shows the modulated wave fm, and FIG. 7 (c) is generated by amplitude-modulating the vehicle detection signal (carrier wave f0 with the modulated wave fm). The amplitude modulated wave F0) is shown. As shown in FIGS. 7A to 7C, the vehicle detection signal used in the conventional vehicle detection system is an amplitude-modulated wave F0 having a period of T and a mark space ratio of 1: 1. be.

FIG. 8 is a block diagram showing a configuration of a ground receiving device (hereinafter referred to as “conventional ground receiving device”) 60 of a conventional vehicle detection system. As shown in FIG. 8, the conventional ground receiver 60 includes a Fd BPF410, a f0 BPF61, a demodulation circuit 62, an fm BPF63, a detection smoothing circuit 64, a second processing unit 65, and a disconnection determination. It has a portion 45.

The f0 BPF 61 is a filter that passes through the frequency band of the carrier wave f0, and a received signal received from the corresponding loop coil LC is input. The demodulation circuit 62 demodulates the output of the f0 BPF61 (that is, the amplitude-modulated wave F0). The fm BPF 63 passes through the frequency band of the modulated wave fm, and the detection smoothing circuit 64 detects and smoothes the output of the fm BPF 63. The amplitude-modulated wave F0 is demodulated by the demodulation circuit 62, and the demodulation result of the amplitude-modulated wave F0 by the demodulation circuit 62 passes through the fm BPF 63, so that the modulated wave fm is extracted from the amplitude-modulated wave F0, and further, the detection smoothing circuit 64 The modulated wave fm extracted from the amplitude modulated wave F0 is converted into DC by passing through. Then, the second processing unit 65 monitors the level of the DC-converted modulated wave fm as the reception level of the vehicle detection signal, and when the level of the DC-converted modulated wave fm is equal to or higher than the determination level, the traveling path R is used. It is determined that the vehicle V exists in the corresponding loop coil LC section.

As described above, in the conventional vehicle detection system, the vehicle detection signal transmitted from the conventional on-board transmission device 50 is an amplitude-modulated wave F0 having a period of T and a mark space ratio of 1: 1. The ground receiving device 60 receives the vehicle detection signal (amplitude modulated wave F0) via the loop coil LC. Then, the conventional terrestrial receiver 60 extracts the modulated wave fm from the amplitude modulated wave F0, converts the extracted modulated wave fm into a DC, and sets the level of the converted modulated wave fm (output of the detection smoothing circuit 64) to the vehicle. The vehicle V exists in the corresponding loop coil LC section (closed section) in the travel path R based on the level of the modulated wave fm (output of the detection smoothing circuit 64) that is monitored as the reception level of the detection signal and converted into DC. It was judged whether or not to do it.

On the other hand, in the vehicle detection system according to the embodiment, the vehicle detection signal transmitted from the on-board transmission device 10 has a period of T and a mark space ratio of 1: 1 and the first amplitude modulated wave F1. It is a combined wave with the second amplitude modulated wave F2 having a period of T and a mark space ratio of 1: 1. The ground receiving device 40 uses a loop coil LC to transmit a vehicle detection signal (first amplitude modulated wave F1). And the second amplitude modulated wave F2 combined wave) is received. The terrestrial receiver 40 separates the first amplitude modulated wave F1 from the vehicle detection signal, extracts the modulated wave fm from the first amplitude modulated wave F1, and converts the extracted modulated wave fm into a DC. Further, the ground receiving device 40 separates the second amplitude modulated wave F2 from the vehicle detection signal, extracts the modulated wave fm from the second amplitude modulated wave F2, and converts the extracted modulated wave fm into a DC. Then, the ground receiver 40 adds these two DC-converted modulated wave fm (that is, the output of the first detection smoothing circuit 423A and the output of the second detection smoothing circuit 423B), and detects the level of the addition result by the vehicle. It is monitored as a signal reception level, and it is determined whether or not the vehicle V exists in the section of the corresponding loop coil LC on the travel path R based on the level of the addition result.

Here, the modulated wave fm extracted from the first amplitude modulated wave F1 is converted into DC (output of the first detection smoothing circuit 423A) and the modulated wave fm extracted from the second amplitude modulated wave F2 is converted into DC. Each of the above (output of the second detection smoothing circuit 423B) corresponds to the digitized modulation wave fm extracted from the amplitude modulated wave F0 in the conventional vehicle detection system (output of the detection smoothing circuit 64). Therefore, the level of the addition result between the modulated wave fm taken out from the first amplitude modulated wave F1 converted into DC and the modulated wave fm extracted from the second amplitude modulated wave F2 converted into DC is the conventional level. The level of the modulated wave fm extracted from the amplitude modulated wave F0 in the vehicle detection system is doubled. That is, in the vehicle detection system according to the embodiment, the reception level of the vehicle detection signal in the ground receiving device is twice the reception level of the vehicle detection signal in the conventional ground receiving device.

Therefore, according to the vehicle detection system according to the embodiment, the vehicle detection signal in the ground receiving device is compared with the conventional vehicle detection system without significantly amplifying the vehicle detection signal or increasing the number of on-board antennas. The reception level of can be increased. As a result, the S / N ratio between the vehicle detection signal and the noise in the ground receiver can be improved, and false detection of the presence or absence of a vehicle in the corresponding loop coil section can be effectively prevented. In the vehicle detection system according to the embodiment, the "level of the addition result by the addition unit 43" corresponds to the "total level" of the present invention.

Next, a modified example of the ground receiving device 40 will be described with reference to FIG. However, the description of the components common to the above-mentioned terrestrial receiver 40 will be omitted as appropriate. Further, in FIG. 9, a waveform example at a predetermined location is shown at the lower side of the block diagram showing the configuration of the ground receiving device 40'according to the modified example. As shown in FIG. 9, the ground receiving device 40'according to the modified example has a separation unit 41, a demodulation processing unit 42', a synthesis unit 46, a detection smoothing unit 47, and a processing unit 48.

The separation unit 41 includes a BPF 410 for fd, a BPF 411 for f1, and a BPF 412 for f2, and each amplitude modulated wave (first amplitude modulated wave F1, second amplitude modulated wave F2, and disconnection detection signal fd) from the received signal. To separate.

The demodulation processing unit 42'demodulates each amplitude modulated wave separated by the separation unit 41 and extracts the modulated wave from each amplitude modulated wave. The demodulation processing unit 42'includes a first demodulation processing unit 42A'and a second demodulation processing unit 42B'.

The first demodulation processing unit 42A'has a first demodulation circuit 421A and a first fm BPF422A. The first demodulation processing unit 42A'demodulates the first amplitude modulated wave F1 which is the output of the BPF411 for f1, extracts the modulated wave fm from the first amplitude modulated wave F1, and transfers the extracted modulated wave fm to the synthesis unit 46. send.

The second demodulation processing unit 42B'has a second demodulation circuit 421B, a second fm BPF422B, and a delay circuit 141. The second demodulation processing unit 42B'demodulates the second amplitude modulated wave F2 which is the output of the BPF412 for f2, extracts the modulated wave fm from the second amplitude modulated wave F2, and extracts the extracted modulated wave fm in a half cycle (T). / 2) Delayed and sent to the synthesizer 46.

The synthesis unit 46 synthesizes the modulated wave fm sent from the first demodulation processing unit 42A'and the modulated wave fm sent from the second demodulation processing unit 42B', and synthesizes a combined wave (modulated wave fm + modulated wave fm). Is sent to the detection smoothing unit 47.

The detection smoothing unit 47 converts (converts to direct current) the combined wave (modulated wave fm + modulated wave fm) sent from the combining unit 46 into direct current, and sends the converted combined wave to the processing unit 48.

The processing unit 48 monitors the level of the combined wave converted to direct current by the detection smoothing unit 47 as the reception level of the vehicle detection signal. Then, when the level of the DC-converted combined wave is equal to or higher than the first threshold value, the processing unit 48 determines that the vehicle V exists in the corresponding loop coil LC section (closed section) in the traveling path R. Information indicating that the vehicle V exists in the section (closed section) of the corresponding loop coil LC on the travel path R is output. On the other hand, when the level of the DC-converted combined wave is less than the first threshold value, the processing unit 48 determines that the vehicle V does not exist in the corresponding loop coil LC section (closed section) in the traveling path R. ..

Even when the ground receiving device 40'according to the modified example is used instead of the ground receiving device 40, the same effect as that of the above-described embodiment can be obtained. Further, when the ground receiving device 40'according to the modified example is used instead of the ground receiving device 40, the "level of the combined wave converted to direct current by the detection smoothing unit 47" corresponds to the "total level" of the present invention. ..

In the above-described embodiment, the vehicle detection signal transmitted from the on-board transmission device 10 is two amplitude-modulated waves (first amplitude-modulated wave F1) whose carrier frequencies are different from each other and are amplitude-modulated by the modulated wave fm of the same frequency. , The second amplitude modulated wave F2). However, it is not limited to this. The vehicle detection signal transmitted from the on-board transmission device 10 may be composed of three or more amplitude-modulated waves whose carrier frequencies are different from each other and which are amplitude-modulated by the modulated wave fm of the same frequency. The vehicle detection system according to another embodiment will be described below. However, the description of the components common to the vehicle detection system according to the above-described embodiment will be omitted as appropriate.

FIG. 10 is a block diagram showing a configuration of an on-board transmission device 10 of a vehicle detection system according to another embodiment. The carrier wave generation unit 11 generates n carrier waves having different frequencies from each other. The carrier wave generation unit 11 generates a first carrier wave generation circuit 111 that generates the first carrier wave f1, a second carrier wave generation circuit 112 that generates the second carrier wave f2, and a carrier wave (third carrier wave f3) having a frequency of f3. A third carrier wave generation circuit 113 and an nth carrier wave generation circuit 11n that generates a carrier wave having a frequency of fn (nth carrier wave) are included.

The modulated wave generation unit 12 generates a square wave having a period of T (frequency fm = 1 / T) and a mark space ratio of 1: (n-1) as the modulated wave fm. For example, when the number of carrier waves generated by the carrier wave generation unit 11 is 3 (n = 3), the modulation wave generation unit 12 modulates a square wave having a period of T and a mark space ratio of 1: 2. When the number of carrier waves generated as fm and the carrier wave generation unit 11 is 5 (n = 5), the modulation wave generation unit 12 is a square wave having a period of T and a mark space ratio of 1: 4. Is generated as a modulated wave fm.

The modulation unit 13 modulates the n carrier waves (first carrier wave f1, second carrier wave f2, third carrier wave f3, ... nth carrier wave fn) generated by the carrier wave generation unit 11 by the modulation wave generation unit 12. It is sequentially modulated by the wave fm to generate n amplitude-modulated waves. The modulation unit 13 includes a first modulation circuit 131, a second modulation circuit 132, a third modulation circuit 133, and ... an nth modulation circuit 13n.

The first modulation circuit 131 generates the first amplitude modulation wave F1 by amplitude-modulating the first carrier wave f1 generated by the first carrier wave generation circuit 111 with the modulation wave fm. The second modulation circuit 132 generates the second amplitude modulation wave F2 by amplitude-modulating the second carrier wave f2 generated by the second carrier wave generation circuit 112 by the modulation wave fm delayed (T / n) by the delay circuit 141. .. The third modulation circuit 133 amplitude-modulates the third carrier wave f3 generated by the third carrier wave generation circuit 113 by the modulation wave fm delayed by 2 × (T / n) by the two delay circuits 141, and performs the third amplitude modulation. Generate wave F3. ... The nth modulation circuit 13n is a modulation in which the nth carrier wave fn generated by the nth carrier wave generation circuit 11n is delayed by (n-1) × (T / n) by (n-1) delay circuits 141. Amplitude modulation is performed by the wave fm to generate the nth amplitude modulated wave Fn.

The synthesizing unit 14 synthesizes the first amplitude modulated wave F1 to the nth amplitude modulated wave Fn generated by the modulation unit 13 to generate a vehicle detection signal. The amplification unit 15 amplifies the vehicle detection signal (composite wave of the first amplitude modulated wave F1 to the nth amplitude modulated wave Fn) generated by the synthesis unit 14. Then, the vehicle detection signal amplified by the amplification unit 15 is transmitted to the loop coil LC via the on-board antenna 20.

FIG. 11 shows an example of an amplitude modulated wave and a vehicle detection signal generated by the on-board transmission device 10 of the vehicle detection system according to another embodiment. FIG. 10A shows a case where the vehicle detection signal is composed of three amplitude-modulated waves (when n = 3), and FIG. 10B shows a case where the vehicle detection signal is composed of five amplitude-modulated waves. The case where it is configured (the case where n = 5) is shown.

As shown in FIG. 11A, when the vehicle detection signal is composed of three amplitude modulated waves, the vehicle detection signal has a period of T and a mark space ratio of 1: 2. It is a composite wave of the modulated wave F1 to the third amplitude modulated wave F3. Here, the second amplitude modulated wave F2 is T / 3 shifted with respect to the first amplitude modulated wave F1, and the third amplitude modulated wave F3 is 2T / 3 shifted with respect to the first amplitude modulated wave F1. ing. Therefore, in the vehicle detection signal, the mark portion M of the other amplitude-modulated wave is arranged in each space portion S of the first amplitude-modulated wave F1 to the third amplitude-modulated wave F3.

Further, as shown in FIG. 11B, when the vehicle detection signal is composed of five amplitude-modulated waves, the vehicle detection signal has a period of T and a mark space ratio of 1: 4. 1 Amplitude modulated wave F1 is a composite wave of the fifth amplitude modulated wave F5. Here, the second amplitude modulated wave F2 is T / 5 shifted with respect to the first amplitude modulated wave F1, and the third amplitude modulated wave F3 is 2T / 5 shifted with respect to the first amplitude modulated wave F1. The 4 amplitude modulated wave F4 is 3T / 5 shifted with respect to the 1st amplitude modulated wave F1, and the 5th amplitude modulated wave F5 is 4T / 5 shifted with respect to the 1st amplitude modulated wave F1. Therefore, in the vehicle detection signal, the mark portion M of the other amplitude-modulated wave is arranged in each space portion S of the first amplitude-modulated wave F1 to the fifth amplitude-modulated wave F5.

FIG. 12 is a block diagram showing a configuration of the ground receiving device 40 of the vehicle detection system according to another embodiment. The separation unit 41 includes n BPFs (bandpass filters) to which the received signal is input, specifically, a bPF 410 for fd, a BPF 411 for f1, a BPF 412 for f2, a BPF 413 for f3, and so on. Includes BPF41n for fn. The f3 BPF413 is a filter that passes through the frequency band of the third carrier wave f3, and the fn BPF41n is a filter that passes through the frequency band of the nth carrier wave fn. Then, the output of BPF411 for f1 (first amplitude modulated wave F1), the output of BPF412 for f2 (second amplitude modulated wave F2), the output of BPF413 for f3 (third amplitude modulated wave F3), ... BPF41n for fn. (Nth amplitude modulation wave Fn) is sent to the demodulation processing unit 42, and the output of the fd BPF 410 (disconnection detection signal fd) is sent to the disconnection determination unit 45.

The demodulation processing unit 42 demodulates each amplitude modulated wave (first amplitude modulated wave F1 to nth amplitude modulated wave Fn) separated by the separation unit 41, extracts the modulated wave from each amplitude modulated wave, and takes out each of them. It is configured to convert (convert to DC) the modulated wave to DC. The demodulation processing unit 42 includes a first demodulation processing unit 42A, a second demodulation processing unit 42B, a third demodulation processing unit 42C, and ... nth demodulation processing unit 42N.

The third demodulation processing unit 42C has a third demodulation circuit 421C that demodulates the third amplitude modulated wave F3 that is the output of the F3 BPF413, a third fm BPF422C that passes through the frequency band of the modulated wave fm, and a third fm BPF422C. It has a third detection smoothing circuit 423C that detects and smoothes the output of. ... The nth demodulation processing unit 42N is for the nth demodulation circuit 421N that demodulates the nth amplitude modulated wave Fn which is the output of the bPF41n for fn, the nfmBPF422N that passes through the frequency band of the modulated wave fm, and the nth nth. It has an nth detection smoothing circuit 423N that detects and smoothes the output of BPF422N. Then, the demodulation result of the third amplitude modulated wave F3 by the third demodulation circuit 421C passes through the third fm BPF422C and the third detection smoothing circuit 423C, so that the modulated wave fm is taken out and taken out from the third amplitude modulated wave F3. The modulated wave fm is converted to DC. Similarly, when the demodulation result of the nth amplitude modulated wave Fn by the nth demodulation circuit 421N passes through the nfm BPF422N and the nth detection smoothing circuit 423N, the modulated wave fm is extracted and extracted from the nth amplitude modulated wave Fn. The modulated wave is converted to DC.

The addition unit 43 adds n DC-converted modulated waves fm sent from the demodulation processing unit 42 (first demodulation processing unit 42 to nth demodulation processing unit 43N), and adds the addition result to the first processing unit 44. Output to.

The first processing unit 44 monitors the level of the addition result by the addition unit 43 as the reception level of the vehicle detection signal. Then, when the level of the addition result by the addition unit 43 is equal to or higher than the predetermined first threshold value, the first processing unit 44 has the vehicle V in the corresponding loop coil LC section (closed section) in the travel path R. Then, it is determined that the information indicating that the vehicle V exists in the section (closed section) of the corresponding loop coil LC on the travel path R is output. On the other hand, when the level of the addition result by the addition unit 43 is less than the first threshold value, the first processing unit 44 determines that the vehicle V does not exist in the corresponding loop coil LC section (closed section) on the travel path R. do.

FIG. 13 shows the relationship between the number n of the amplitude-modulated waves constituting the vehicle detection signal transmitted from the on-board transmission device and the reception level of the vehicle detection signal in the ground receiving device.

In FIG. 13, the reception level when n = 1, that is, when the number of amplitude-modulated waves constituting the vehicle detection signal is 1, indicates the reception level of the vehicle detection signal in the conventional ground receiver 60. Here, the reception level of the vehicle detection signal in the conventional ground receiving device 60 is set to a reference value of 1.0. When n = 2, that is, when the number of amplitude-modulated waves constituting the vehicle detection signal is 2, the reception level is the reception level of the vehicle detection signal in the ground receiving device 40 of the vehicle detection system according to the above-described embodiment. Yes, it is twice the reception level of the vehicle detection signal in the conventional ground receiving device 60. When n ≧ 3, that is, when the number of amplitude-modulated waves constituting the vehicle detection signal is 3 or more, the mark in each amplitude-modulated wave constituting the vehicle detection signal is compared with the case of n = 1 or n = 2. Although the ratio of the units is small, the reception level of the vehicle detection signal in the ground receiving device 40, which is the level of the addition result by the adding unit 43, is 2.5 times or more the reception level of the vehicle detection signal in the conventional ground receiving device 60. become.

Therefore, as with the vehicle detection system according to the above-described embodiment, the vehicle detection system according to another embodiment can also increase the reception level of the vehicle detection signal in the ground receiving device as compared with the conventional vehicle detection system. .. As a result, the S / N ratio between the vehicle detection signal and the noise in the ground receiver can be improved, and false detection of the presence or absence of a vehicle in the corresponding loop coil section can be effectively prevented. In the vehicle detection system according to another embodiment as well as the vehicle detection system according to the embodiment, the "level of the addition result by the addition unit 43" corresponds to the "total level" of the present invention.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it is needless to say that the present invention can be modified and modified based on the technical idea of the present invention. For example, the present invention can be widely applied to a transmission / reception system for transmitting / receiving various signals other than a vehicle detection signal.

10 ... On-board transmitter (transmitter), 11 ... Carrier wave generator, 12 ... Modulated wave generator, 13 ... Modulator, 14 ... Synthesizer, 15 ... Amplifier, 20 ... On-board antenna, 30 ... Ground transmitter , 31 ... disconnection detection signal generation unit, 32 ... speed limit signal generation unit, 40 ... ground receiver (receiver), 41 ... separation unit, 42 ... demodulation processing unit, 43 ... addition unit, 44 ... first processing unit, 45 ... disconnection determination unit, LC ... loop coil, R ... running path, V ... vehicle

Claims (7)

A transmitter that transmits a signal containing a plurality of amplitude-modulated waves whose carrier frequencies are different from each other and whose amplitude is modulated by a modulated wave of the same frequency.
A receiving device that receives the signal, extracts the modulated wave from the plurality of amplitude modulated waves, and executes processing according to the total level of the summed levels of the extracted modulated waves.
Has a transmission / reception system. The transmission / reception system according to claim 1, wherein the receiving device outputs information when the total level is equal to or higher than a threshold value. The transmission / reception system according to claim 1, wherein the receiving device outputs different information depending on whether the total level is equal to or higher than the threshold value and lower than the threshold value. The transmission / reception system according to any one of claims 1 to 3, wherein in the signal, a mark portion of another amplitude-modulated wave is arranged in a space portion of each of the plurality of amplitude-modulated waves. The transmitter is
A carrier wave generator that generates multiple carriers with different frequencies from each other,
A modulation unit that sequentially amplitude-modulates each of the plurality of carrier waves generated by the carrier wave generation unit with a modulation wave of the same frequency to generate a plurality of amplitude-modulated waves, and a modulation unit.
A compositing unit that synthesizes a plurality of amplitude-modulated waves generated by the modulation unit to generate the signal, and a compositing unit.
The transmission / reception system according to any one of claims 1 to 4. The receiving device is
A separation unit that separates each amplitude-modulated wave from the received signal,
A demodulation processing unit that demodulates each amplitude-modulated wave separated by the separation unit and extracts a modulated wave from each amplitude-modulated wave.
A processing unit that executes processing according to the total level of the sum of the levels of the modulated waves taken out by the demodulation processing unit, and a processing unit.
The transmission / reception system according to any one of claims 1 to 5. The transmitting device is provided on a vehicle traveling on a predetermined traveling path.
The receiving device receives the signal through a loop coil provided along the traveling path, and when the level of the addition result is equal to or higher than the threshold value, the vehicle is placed in a section of the corresponding loop coil in the traveling path. It is determined that the vehicle exists, and information indicating that the vehicle exists in the corresponding loop coil section on the travel path is output.
The transmission / reception system according to any one of claims 1 to 6.

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