JP2000269722A - Obstacle detector for antenna mounted on moving object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect level reduction due to obstacles. SOLUTION: Levels of antenna reception signals from plural antennas 18A, 18B, 18C, and 18R mounted on a moving object are reduced, if corresponding antennas are shielded by obstacles. A maximum level extraction circuit 6, to which these antenna reception signals are inputted, is provided. This extraction circuit 6 generates a maximum level signal obtained by subtracting a preliminarily determined threshold from a signal having a maximum level. Comparators 18A, 18B, 18C, and 18R generate an obstruction level detection signal, if a signal having a value smaller than the maximum level signal from the extraction circuit 6 exists in antenna reception signals. In response to this obstruction level detection signal, a 2.8 ms pulse generating circuit 22 generates a pulse signal in a period, when it can be considered that antennas are shielded by obstacles. In response to the fall of this pulse signal, a 20 ms pulse generation circuit 24 generates a pulse signal. If the maximum level signal of the maximum level extraction circuit 6 is reduced to a value lower than the level reduction threshold during 2.8 ms, the output signal of a comparator 28 resets the 20 ms pulse generation circuit 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an obstacle detecting device for detecting whether an antenna mounted on a moving body such as a vehicle or a ship is shielded by an obstacle.

[0002]

2. Description of the Related Art Conventionally, an antenna mounted on a moving body is
Automatic tracking is performed so that a moving body always points to a transmission source, for example, a broadcasting satellite or a communication satellite, even when the moving body moves. This automatic tracking determines the reception level of one antenna,
The elevation angle and azimuth of the antenna are adjusted so that this becomes a predetermined value or more.

[0003]

By the way, the reception level of the antenna may suddenly drop, and automatic tracking may not be possible. As a cause of this, for example, a pointing error due to a sudden turning or sudden stop of the moving body, and a temporary movement of the moving body due to a shielding object, for example, when the moving body is a vehicle, a building or an oncoming vehicle It can be considered as radio wave shielding. In case of a pointing error, it can be dealt with by searching the position of the antenna again.In the case of shielding by an obstacle, if the automatic tracking device is equipped with a gyro or GPS, it will be corrected to a state where it can be received normally by tracking using this can do. However, in the case where the reception level of the antenna is simply determined as described above, it is not possible to determine the cause, and the search is performed again. Therefore, it took a lot of time to correct again to a normal reception state.

An object of the present invention is to provide an obstacle detecting device capable of detecting a level decrease due to an obstacle.

[0005]

An obstacle detection device according to one embodiment of the present invention is used with a plurality of antennas mounted on a moving body. Antenna reception signals from these antennas decrease in level when the corresponding antenna is shielded by an obstacle. Each antenna is arranged such that this reduction in level occurs first in one antenna and then in the other. When the level drops in the next antenna, the reception level of the antenna whose level has dropped earlier often returns to the original level. A failure level decrease detection circuit to which these antenna reception signals are input is provided. This detection circuit has at least two
When a level drop that can be regarded as a level drop due to an obstacle occurs between the levels of the two antenna reception signals, a fault level drop detection signal is generated. The failure level drop detection signal
An obstacle detection circuit is also provided that generates an obstacle detection signal when the detection is continued for a period that can be regarded as shielding of the antenna by an obstacle or more.

[0006] In general, a drop in antenna level due to an obstacle occurs in one antenna. In this case, a level difference occurs between at least two antenna reception levels, and based on this, the failure level detection circuit generates a failure level decrease detection signal. The shielding by the obstacle continues for a period longer than the period that can be regarded as the shielding of the antenna by the obstacle, and the signal level continues to decrease.
Therefore, when the obstacle level reduction detection signal is generated over the above period, it is determined that the obstacle is blocked by the obstacle, and the obstacle detection signal is generated. When this signal is generated, control is performed so that the transmission source is directed to the antenna using a gyro or GPS, for example.

[0007] The obstacle detection circuit, when the received signal level of all antennas falls below a predetermined level drop threshold,
It may have a blocking circuit for blocking generation of the obstacle detection signal. In addition to the shielding by the obstacle, for example, a sudden turn or a sudden stop of the moving body causes a decrease in the reception signal level. However, this level drop occurs in all antenna reception signals and occurs for a period shorter than a period that can be regarded as blocking of the antenna by an obstacle. Therefore, when the received signal level of all antennas falls below the predetermined level drop threshold, the blocking circuit generates a blocking signal. In addition, when the moving body suddenly turns or stops suddenly, as described above, the entire level decreases during a period shorter than the period in which the antenna can be regarded as being shielded by the obstacle, so that the generation of the obstacle detection signal is prevented by this signal. Erroneous determination is prevented.

[0008] The blocking circuit may include an extraction circuit for extracting a signal of the highest level among the received signals of all the antennas, and a comparison circuit for comparing the extracted signal from the extraction circuit with the level reduction threshold. . If the antenna reception signal at the maximum level is lower than the level lowering threshold, it can be determined that all the antenna receiving signals are lower than the level lowering threshold. In this case, the circuit configuration can be simplified as compared with comparing the level of each antenna reception signal with the level reduction threshold.

The failure level detection circuit includes a maximum level extraction circuit for generating an output obtained by subtracting a predetermined threshold from a maximum level signal among all antenna reception signals, and an output signal of the maximum level extraction circuit for all antenna reception signals. When there is a signal that is smaller than the output of the maximum level extraction circuit among the antenna reception signals, it is possible to generate a failure level reduction detection signal.

When there is an antenna reception signal whose level is lower than a value obtained by subtracting a predetermined threshold value from the reception signal of the maximum level, a level difference occurs between the two antenna reception levels due to shielding by an obstacle. Can be considered. In this case, the circuit configuration can be simplified as compared with the case where each antenna reception level has a level difference greater than or equal to a predetermined threshold value.

An obstacle detection device according to another aspect of the present invention is also used with a plurality of antennas mounted on a moving body. The levels of the antenna reception signals from these antennas decrease when the corresponding antenna is shielded by an obstacle. Each antenna is arranged such that this reduction in level occurs first in one antenna and then in the other. When the level drops in the next antenna, the reception level of the antenna whose level has dropped earlier often returns to the original level. A maximum level extraction circuit to which these antenna reception signals are input is provided. This extraction circuit generates a maximum level signal obtained by subtracting a predetermined threshold from the maximum level signal. The failure level detection circuit compares each antenna reception signal with the maximum level signal, and generates a failure level detection signal when each antenna reception signal has a value smaller than the maximum level signal. The output signal of the obstacle level detection circuit is delayed over a period in which the delay circuit can be regarded as blocking the antenna by an obstacle. In response to the output of the delay circuit, an obstacle detection signal generation circuit generates an obstacle detection signal. When the maximum level signal falls below a predetermined level lowering threshold, the deactivating circuit deactivates the fault detection signal generating circuit.

In this obstacle detection device, when there is a signal having a value smaller than the maximum level signal obtained by subtracting a predetermined threshold value from the signal having the maximum level among the antenna reception signals, a value smaller than the maximum reception level by at least the threshold value is obtained. Antenna receive signals, and at least one receive antenna may be shielded by an obstacle. To indicate this, a fault level detection signal is generated. If one antenna is actually shielded by an obstacle, this shielding state continues for at least a period that can be regarded as shielding.
Therefore, the failure level detection signal is delayed for this period. If, for example, the mobile object is turning sharply instead of being blocked by an obstacle, the levels of all the antenna reception signals are lower than the level lowering threshold value before the elapse of this period. Therefore, at this time, a de-energizing signal is generated to prevent an obstacle detection signal from being generated based on the output of the delay means. Further, if the de-energization signal is not generated within the delay period, the reception level is reduced due to the shielding by the obstacle, and the obstacle detection signal is generated.
In this case, since the maximum level extraction circuit is used for detecting that at least one of the reception levels has dropped and for detecting the drop in all the antenna reception levels, the circuit configuration is simplified.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An automatic antenna tracking device provided with an obstacle detection device according to one embodiment of the present invention includes a plurality of, for example, four rectangular receiving antennas mounted on a moving body, for example, a vehicle or a ship. 2A, 2B, 2C, and 2R are provided. The receiving antennas 2A, 2B, 2C, and 2R are the same planar antenna for receiving satellite broadcasting or satellite communication for receiving a desired satellite, for example. Receiving antennas 2A, 2
B, 2C, and 2R are arranged side by side vertically and horizontally on one gantry provided on the moving body. The elevation angle and the azimuth angle of the gantry can be adjusted by a driving unit (not shown). By this adjustment, the receiving antennas 2A, 2B,
The 2C, 2R can be directed to a transmission source, for example, a desired broadcast or communication satellite.

Each of these receiving antennas 2A, 2B, 2C,
Although not shown, each 2R is provided with a converter. By these converters, the received signals of the respective receiving antennas 2A, 2B, 2C, 2R are converted into the first intermediate frequency signals, respectively, and supplied to the phase combining unit 4. Here, in-phase synthesis of each first intermediate frequency signal is performed. The AGC signals A, B, C,
R (these are proportional to each antenna received signal)
Are supplied to the maximum level extraction circuit 6. The maximum level extraction circuit 6 generates an extraction signal that is lower than the maximum level among the AGC signals A, B, C, and R by a predetermined threshold.

The maximum level extracting circuit 6 has input terminals 8A, 8B, 8C, 8R to which the respective AGC signals A, B, C, R are inputted, as shown in FIG. 2, for example. These input terminals 8A, 8B, 8C, 8R are connected to a diode 10
A, 10B, 10C, and 10R anodes are connected. These diodes 10A, 10B, 10C, 10R
Are connected to each other and grounded via a resistor 12. These diodes 10A, 10B, 10
C and 10R have the same characteristics. Therefore, between the ends of the resistor 12, the diodes 10A, 10B, 1
A voltage is generated having a value obtained by subtracting the voltage drop of the corresponding one of OC and 10R.

A resistor 12 and diodes 10A, 10A
The cathode of the Zener diode 14 is connected to the connection point between the cathodes of B, 10C and 10R, and the anode of the Zener diode 14 is connected to the output terminal 16 of the maximum level extraction circuit 6. Therefore, between the output terminal 16 and the ground potential, the voltage between both ends of the resistor 12 (the voltage drop of the diode 10A, 10B, 10C or 10R from the maximum level among the AGC signals A, B, C and R). Is subtracted from the voltage drop in the Zener diode 14 to generate a voltage as an extraction signal. The voltage drop at the Zener diode 14 is the threshold.

As shown in FIG. 1, each AGC signal A, B,
C and R are compared with the extracted signal from the maximum level extraction circuit 6 by the comparators 18A, 18B, 18C and 18R. Each of the comparators 18A, 18B, 18C, and 18R outputs a failure level reduction detection signal when the AGC signal input thereto is smaller than the extraction signal from the maximum level extraction circuit 6.
For example, an H-level output signal is generated.

That is, the comparators 18A, 18B, 18C, 1
The 8R generates an H-level output signal when the AGC signal input to itself becomes smaller than a value obtained by subtracting a predetermined threshold from the maximum-level received signal. In this case, when an H-level output signal is generated, there is an antenna reception signal having a level smaller than a value obtained by subtracting a threshold from the maximum reception level. Maximum level extraction circuit 6
And the comparators 18A, 18B, 18C, and 18R constitute a failure level reduction detection circuit.

These comparators 18A, 18B, 18C, 1
The 8R output signal is supplied to a delay circuit, for example, a 2.8 ms pulse generation circuit 22 via an OR circuit 20. The 2.8 ms pulse generation circuit 22 includes comparators 18A and 18A.
An H-level pulse signal is generated for 2.8 ms from when an H-level output signal is generated from any of B, 18C, and 18R. These comparators 18A, 18
B, 18C and 18R constitute a failure level detection circuit.

The generation time of the H level is a time expected to be a period in which at least one antenna is shielded when any of the receiving antennas 2A, 2B, 2C, and 2R is shielded by an obstacle. is there.

For example, when the moving object is a vehicle, the time during which one receiving antenna is blocked by the oncoming vehicle is the time during which the one receiving antenna is blocked along the short side direction. Is shorter than when shielded along the long side. Although the length of the short side is, for example, 25 cm, both oncoming vehicles and vehicles equipped with this antenna are at a very high speed,
Assuming that the vehicle is traveling at 160 km, the shielding time of one antenna is 2.8125 ms (0.25 m / 3
60 km / s). From this time, the pulse generation time of the 2.8 ms pulse generation circuit 22 is determined.

The response characteristics of the AGC signals A, B, C, and R are set faster than 2.8 ms, for example, 2 ms. The output signal of the 2.8 ms pulse generation circuit 22 is fed back to the OR circuit 20 in order to stably generate a 2.8 ms pulse signal.

When the pulse signal of the 2.8 ms pulse generation circuit 22 falls, the fault detection signal generation circuit, for example, a 20 ms pulse generation circuit 24 responds to the fall.
An H-level pulse signal is generated at the first terminal Q for 0 ms as an obstacle detection signal. However, before the pulse signal of the 2.8 ms pulse generation circuit 22 falls, 2
When an H-level reset signal is supplied to the reset terminal R of the 0 ms pulse generation circuit 22, the 20 ms pulse generation circuit 24 does not generate an obstacle detection signal.

The reset signal is generated when the signal extracted by the maximum level extracting circuit 6 falls below a predetermined level lowering threshold. Therefore, the extracted signal from the maximum level extraction circuit 6 is compared with the level reduction threshold signal from the level reduction threshold signal source 26 in the comparator 28. Comparator 28 generates an H-level output signal when the extraction signal from maximum level extraction circuit 6 falls below the level reduction threshold.

The output signal of the comparator 28 is supplied to one input of an AND circuit 30. AND circuit 30
Is connected to the second input of the 20 ms pulse generation circuit 24.
(This is an inverted output of the output of the first terminal Q). Therefore, a reset signal is generated only when an H level output signal is generated from the comparator 28 in a state where no obstacle detection signal is generated at the first terminal Q of the 20 ms pulse generation circuit 24.

Thus, the 20 ms pulse generation circuit 2
4 generates an obstacle detection signal, and even if the output signal of the comparator 28 becomes H level, the 20 ms pulse generation circuit 2
4 is reset, and the generation of the obstacle detection signal is not interrupted. The comparator 28, the AND circuit 30, and the maximum level extracting circuit 6 constitute a blocking circuit or a de-energizing circuit. The blocking circuit, the 2.8 ms pulse generation circuit 22 and the 20 ms pulse generation circuit 24 constitute an obstacle detection circuit.

The tracking device includes a gyro device 3
4, the output of the gyro device 34 in a state where each of the antennas 2A to 2R has successfully received satellite broadcasting or satellite communication is stored, and the gyro is restored so that it can be returned to this state. The elevation and azimuth of the antennas 2A to 2R can be adjusted by the output of the device 34.

In the obstacle detecting device thus configured, for example, as shown in FIG. 3, at time t1, any one of the receiving antennas A, B, C, and R has its own antenna receiving level. 4 is lower than the value obtained by subtracting the threshold value from the maximum value (maximum level) (the value of the extraction signal from the maximum level extraction circuit 6).
As shown in (a), the 2.8 ms pulse generation circuit 22 generates an H level pulse signal.

As shown in FIG. 3, 2.8 m from time t1
If the extracted signal of the maximum level extracting circuit 6 does not drop below the level lowering threshold until the time t2 when s has elapsed, as shown in FIG. 4B, between the time t1 and the time t2,
No reset signal is generated from the AND circuit 30. Therefore, when the H-level pulse signal of the 2.8 ms pulse generation circuit 22 falls at time t2, in response to this,
The 20 ms pulse generation circuit 24 generates an obstacle detection signal for 20 ms as shown in FIG.

In this case, since only the reception level of one receiving antenna has decreased during 2.8 ms, it can be determined that a reception failure is caused by an obstacle. Therefore, when an obstacle detection signal is generated, the receiving antennas 2A, 2B, 2C, and 2R are directed to the broadcasting satellite or the communication satellite by using the gyro device.

As shown in FIG. 4D, at time t1
If the reset signal is generated by the AND circuit 30 at time t2 ′ when 2.8 ms has not elapsed from the time t1, the reception levels of all the receiving antennas 2A, 2B, 2C, and 2R have fallen below the drop level threshold. This is determined to be a pointing error caused by, for example, a sudden turn or a sudden stop when the moving body is a vehicle or the like. In this case, 20m
The s pulse generation circuit 24 does not generate an H level pulse signal as shown in FIG. In the case of this pointing error, a change in the output of the gyro device 30 or a change in the phase occurs, so that it can be determined that the pointing error has occurred, and the search for the broadcasting satellite or the communication satellite is performed again.

Also, due to rainfall or the stoppage of broadcasting satellites or communication satellites, the reception levels of all antennas are reduced as a whole, that is, the reception levels of the respective reception antennas are reduced without a large level difference. 2.8 ms pulse generation circuit 22 does not generate a pulse signal, and AND circuit 32 generates a level reduction detection signal. When a level drop detection signal is generated, an alarm or a display is activated using the level drop detection signal to notify the level drop and to prompt a search after a while.

In the above embodiment, the present invention is applied to an antenna for receiving satellite broadcasting or satellite communication. However, the present invention can be applied to an antenna for receiving other broadcasting. Although the planar antenna is used, another antenna such as a Yagi antenna can be used instead.

In the above embodiment, 2.8 ms
The pulse generation circuit 22 is used. Instead, for example, a clock signal of a constant frequency is counted according to the output of the OR circuit 20, and when the count value becomes a value corresponding to 2.8 ms, the output signal is output. Can be used.

The maximum level extraction circuit 6 and the comparator 18
Although A, 18B, 18C, and 18R are used, it is also possible to calculate the level difference between the AGC signals A, B, C, and R, respectively, and compare each level difference with a predetermined threshold.

Further, the output of the maximum level extracting circuit 6 is compared with the level lowering threshold by the comparator 28. Instead of this, the comparator which compares each AGC signal A, B, C, R with the level lowering threshold is used. And an AND circuit to which the outputs of these comparators are supplied. Each AGC signal A, B,
The maximum level may be extracted by A / D converting C and R and processing these digital values by a computer.

Although the AGC signal is used, an intermediate frequency signal from a converter attached to each antenna may be used instead, or a radio wave in a frequency band lower than that of satellite broadcasting or satellite communication may be received. In the case of an antenna that does, the antenna reception signal may be used as it is.

[0038]

As described above, according to the obstacle detecting device of the present invention, at least two of the plurality of receiving antennas are used.
If the difference between the reception levels of the two reception antennas is equal to or less than a predetermined value and continues for a predetermined time or more, it can be determined that an obstacle is blocking at least one reception antenna, A pointing error that occurs when the vehicle suddenly turns or stops suddenly can be clearly distinguished, and appropriate measures can be taken promptly for a decrease in the reception level due to an obstacle.

According to the obstacle detection device of the present invention, when all the reception levels are reduced within a shorter time than the predetermined time, the generation of the obstacle detection signal is blocked by the blocking circuit. Therefore, it is possible to clearly distinguish a pointing error from a level decrease caused by an obstacle.

The blocking circuit has an extraction circuit for extracting a signal having the maximum level among the reception signals of all the antennas, and a comparison circuit for comparing the extraction signal from the extraction circuit with the level reduction threshold. Therefore, the circuit configuration can be simplified as compared with comparing the level of each antenna reception signal with the level reduction threshold.

A failure level detection circuit for detecting whether at least two reception levels have a difference equal to or greater than a predetermined threshold value,
A maximum level extraction circuit that generates an output obtained by subtracting a predetermined threshold from a maximum level signal among all the antenna reception signals, and compares the output signal of the maximum level extraction circuit with the all antenna reception signals, and When there is one smaller than the output of the maximum level extraction circuit, a comparator that generates a failure level reduction detection signal is included.Therefore, is there a level difference between each antenna reception level and a predetermined threshold or more? The circuit configuration can be simplified as compared with the case where the determination is made one by one.

In the obstacle detecting device according to the present invention,
Since the maximum level extraction circuit is used for detecting that at least one of the reception levels has decreased and for detecting the decrease in the reception levels of all antennas, the circuit configuration is simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram of an automatic tracking device that implements an obstacle detection device according to the present invention.

FIG. 2 is a detailed circuit diagram of a maximum level extraction circuit of FIG.

FIG. 3 is a diagram showing a relationship between a maximum reception level in each reception antenna of the automatic tracking apparatus in FIG. 1 and a reception level of a single reception antenna.

FIG. 4 is a waveform chart of each part in the automatic tracking device of FIG. 1;

[Explanation of symbols]

2A, 2B, 2C, 2R Receiving antenna 6 Maximum level extraction circuit (blocking circuit, failure level drop detection circuit) 18A, 18B, 18C, 18R Comparator (failure level drop detection circuit) 22 2.8 ms pulse generation circuit (failure level) Drop detection circuit) 24 20 ms pulse generation circuit (obstacle detection circuit) 28 Comparator (blocking circuit)

Claims (5)

[Claims] An antenna reception signal from a plurality of antennas mounted on a mobile object, the antenna reception signal having a reduced level when the corresponding antenna is shielded by an obstacle is input, and at least two antenna reception signals are input. When a level drop that can be regarded as a level drop due to the obstacle occurs between the levels of the antenna reception signals, a fault level drop detection circuit that generates a fault level drop detection signal; and And an obstacle detection circuit that generates an obstacle detection signal when the detection is continued for a period that can be regarded as shielding of the antenna by the antenna. 2. The obstacle detection device according to claim 1, wherein the obstacle detection circuit is configured to perform the operation when the level of the received signal from all the antennas falls below a predetermined level reduction threshold. An obstacle detection device for a mobile-mounted antenna having a blocking circuit for blocking generation of an obstacle detection signal. 3. The obstacle detecting device according to claim 2, wherein the blocking circuit extracts a signal having a maximum level from the received signals of all the antennas. An obstacle detection device for a mobile-body-mounted antenna, comprising: a comparison circuit that compares an extracted signal with the level reduction threshold. 4. The mobile-mounted antenna according to claim 1, wherein the fault level detection circuit generates an output obtained by subtracting a predetermined threshold from a maximum level signal among all the antenna reception signals. Circuit, comparing the output signal of the maximum level extraction circuit with the all antenna reception signals, and when there is a signal smaller than the output of the maximum level extraction circuit among the antenna reception signals, the failure level drop detection signal And a comparison circuit for generating an obstacle. 5. An antenna reception signal from a plurality of antennas mounted on a moving body, which is predetermined from a maximum level among antenna reception signals that decrease when the corresponding antenna is shielded by an obstacle. A maximum level extraction circuit that generates a maximum level signal obtained by subtracting the threshold value, comparing each of the antenna reception signals with the maximum level signal, and determining that each of the antenna reception signals has a value smaller than the maximum level signal. When present, a failure level detection circuit that generates a failure level detection signal, a delay circuit that delays an output signal of the failure level detection circuit over a period that can be regarded as shielding the antenna by an obstacle, and an output of the delay circuit. A failure detection signal generating circuit for generating an obstacle detection signal in response to the signal; When drops than the decrease threshold value, the fault detection signal and a deactivating circuit for deactivating the generator, the obstacle detection apparatus in a mobile mounting antenna comprising.