JPH07112123B2 - Automatic tracking antenna device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention changes the elevation angle and azimuth angle of an antenna mounted on a moving object such as a vehicle or train according to the movement of the moving object,
The present invention relates to an automatic tracking antenna device for favorably receiving radio waves from a geostationary satellite such as a broadcasting satellite.

(Prior Art) Previously, the applicant of the present invention has mounted on a moving object, a reflecting mirror, a main primary radiator provided at a focal position of the reflecting mirror, and slightly more than the main primary radiator. A parabolic antenna including a sub-primary radiator that is horizontally offset,
A signal from a primary drive unit provided with a first drive unit provided on the parabolic antenna so as to change the azimuth angle of the parabolic antenna, a second drive unit provided with the parabolic antenna so as to change the elevation angle of the parabolic antenna. Of the parabolic antenna until the main reception level exceeds a predetermined level, and a main reception level detection section that detects the main reception level of the, the sub reception level detection section that detects the sub reception level of the signal from the sub primary radiator. The first control means for supplying a control signal to the first and second drive parts so as to change the azimuth angle and the elevation angle, and the main reception level becomes smaller than a predetermined level due to movement of the moving object, for example. At this time, depending on whether the difference between the main reception level and the sub reception level is positive or negative, the parabola is adjusted in the predetermined direction until the main reception level becomes equal to or higher than the predetermined level. Tena was proposed an automatic tracking apparatus of the parabolic antenna and a second control means for supplying a control signal to the first and second driver to rotate the (Japanese Patent Application No. Sho 60-37189).

[Problems to be Solved by the Invention]

When such a parabolic antenna automatic tracking device is installed in a vehicle moving on land, for example, when the vehicle enters a tunnel or the like and the signal from the broadcasting satellite is suddenly cut off, the main reception level is equal to or higher than a predetermined level. Since the parabolic antenna continues to rotate until it becomes, there is a problem that the mechanical parts such as the first and second driving parts for changing the azimuth angle and the elevation angle of the parabolic antenna are largely consumed. There is also a problem that the energy for rotating the parabolic antenna is wasted.

Further, in order to solve such a problem, it is conceivable that a microcomputer is provided in the tracking device to stop the tracking when the signal from the broadcasting satellite is cut off. However, this stops tracking even when the signal from the broadcasting satellite is cut off, not because the vehicle entered the tunnel but because the response speed of the tracking device is slower than the speed of direction change of the vehicle. There is a problem.

An object of the present invention is to provide an automatic tracking antenna device that can stop the unnecessary movement of the antenna by stopping the signal search when the arrival of radio waves is blocked by an obstacle. .

[Means for Solving the Problems]

The first invention is made in view of the above problems, and includes an antenna mounted on a moving object, a driving unit provided to the antenna so as to change its azimuth angle and elevation angle, and Searching means for supplying a control signal for changing the azimuth angle and elevation angle of the antenna to the driving section until the antenna receives a signal from the geostationary satellite, and the antenna from the geostationary satellite after the operation of the search means is completed. Tracking means for supplying the control signal to the drive section so as to receive a signal at a predetermined level or higher; a noise detection section for detecting the level of noise outside the reception band of the antenna received by the antenna; First determining means for generating a hold command when it is determined that the antenna is receiving a signal from the geostationary satellite, and noise of the noise detecting section according to the hold command. And a holding unit for holding the bell,
It is determined whether the first condition that the noise level of the noise detection unit is higher than the noise level of the hold unit and the second condition that the antenna is receiving a signal from the geostationary satellite are satisfied. When the first condition is satisfied, the tracking means is stopped, when the first condition is unsatisfied and the second condition is satisfied, the tracking means is operated, and when the first and second conditions are unsatisfied, And a second discriminating means for operating the searching means.

Further, according to the second invention, the noise detecting unit detects the level of noise in the reception band of the antenna received by the antenna, and the holding unit preliminarily provides a non-blocking state in the beam direction of the antenna. The noise level of the noise detecting section is held, and when the hold command is received, the noise level of the noise detecting section is changed to a hold level, and the noise level of the noise detecting section is changed to the second discriminating means. Is greater than the noise level of the hold unit and the second condition that the antenna is receiving a signal from the geostationary satellite is determined, and in the unsatisfied state of the second condition, When the first condition is satisfied, the tracking means is stopped, and in this stopped state, the second
When the condition is satisfied, the tracking means is activated to
Further, there is provided a discriminating means for supplying the hold command to the holding part and activating the searching means when the second condition is not satisfied. In the second invention, the first discriminating means is not provided.

[Action]

According to the first aspect of the invention, first, the search means brings the antenna into a state of receiving a signal from the geostationary satellite. Then, the tracking means causes the antenna to receive the signal from the geostationary satellite at a predetermined level or higher. On the other hand, the first
If the discriminating means discriminates that the antenna is receiving the signal from the geostationary satellite, the holding unit holds the noise level outside the reception band of the antenna. When the noise level of the noise detection unit is higher than the noise level held in the hold unit (when the first condition is satisfied), it is considered that the beam direction of the antenna is blocked by the shield, and the tracking unit To stop. Also,
The beam direction of the antenna is not shielded, that is, the noise level of the noise detection unit is smaller than the noise level of the hold unit (when the first condition is not satisfied), and the antenna receives the signal from the geostationary satellite. When the second condition is satisfied (when the second condition is satisfied), the tracking means is caused to perform the tracking operation so that the antenna can receive the signal from the geostationary satellite at a predetermined level or higher. Also, the beam direction of the antenna is not blocked,
That is, when the noise level of the noise detection unit is lower than the noise level of the hold unit (when the first condition is not satisfied), and when the antenna is not receiving a signal from the geostationary satellite (when the second condition is not satisfied). ), The search means is activated and the antenna can receive signals from the geostationary satellite.

Further, in the second invention, search and tracking are performed as in the first invention. In the hold part, the noise level of the noise detection part in the unshielded state in the beam direction of the antenna (the level of noise in the reception band of the antenna received by the antenna) is
It is held in advance. Then, when the antenna is not receiving a signal from the geostationary satellite (when the second condition is not satisfied) and the noise level of the noise detection unit is higher than the noise level of the hold unit, that is, the beam direction of the antenna When is blocked by the shield (when the first condition is satisfied), the tracking means is stopped. Further, in this stopped state, when the antenna is receiving a signal from the geostationary satellite (when the second condition is satisfied), the tracking means is operated so that the antenna outputs the signal from the geostationary satellite at a predetermined level. With the above, reception is possible. Furthermore, when the noise level of the noise detection unit is lower than the noise level of the hold unit, that is, when the beam direction of the antenna is not shielded by the shielding object (when the first condition is not satisfied), the antenna moves from the geostationary satellite. When no signal is received (when the second condition is not satisfied), the hold command is supplied to the hold unit, and the noise level at that time is held by the hold unit, and the beam direction of the antenna is shielded by the shield after that. It is used to determine whether or not the antenna has been detected, and the search means is activated to enable the antenna to receive a signal from a geostationary satellite.

(Embodiment) In the present invention, the noise level is detected by the noise detection unit, and this noise level becomes higher than the noise detection level in the state where the arrival of the signal from the geostationary satellite to the antenna is not blocked. At this time, that is, when the noise level becomes equal to or higher than the level at which the arrival of radio waves is blocked, it is possible to determine that reception has been cut off due to an obstacle in the beam direction and stop reception. Then, the search and tracking of the broadcast wave can be restarted based on the noise level and whether or not the broadcast wave is received. Therefore, before the description of the embodiments, it will be briefly described that the noise level becomes high when the obstacle is in the beam direction.

A noise wave is generated from an object in the natural world in proportion to the temperature of the object, but when trying to receive a signal from a geostationary satellite, the beam width of the antenna is narrow as is known, and the beam direction is the satellite. Or facing the sky. Therefore, the antenna does not receive artificial noise on the ground from its beam direction and rarely receives artificial noise from the sky. Based on these things, the value of the noise level during reception of the signal from the satellite is held in advance, and when the received noise level becomes higher than the held noise level, there is an obstacle in the beam direction. You can judge that you are doing. Explaining this concretely by a calculation formula, the noise power N of the entire receiver including the amount of attenuation such as rainfall is: noise power N = kB {αT _a + (1-α) T _o + (F-1 ) T _o }
(W) ‥‥ (1) but is represented by _{T a = 60R + (1-} R) T o (K) ‥‥ (2).

k is Boltzmann's constant ^{1.3807 × 10 -23 (J / K} ), B is the channel bandwidth, for example _{^{27 × 10 6 (27MH z)}} , α is the coupling loss of the antenna and a frequency converter (times), T _a is the antenna Antenna noise temperature (K) when T is facing the sky, T ₀
Is a reference temperature, for example, the noise temperature of the ground is 290 (K), F is a receiver noise figure (times), and R is an attenuation amount (times) at T _a due to rainfall, beam direction interception, or the like.

Here, at the time of fine weather, we obtain the noise power N ₂ when there is a noise power N ₁ and the obstacle when the beam direction obstacle free (R = 1 (multiplication)) (R = 0 (times)). However, assuming that there is no coupling loss, α = 1 (times), and F =
Assuming 1.5 times, the noise power N ₁ is 7.64 × 10 ⁻¹⁴ (W) according to the equations (1) and (2), and the noise power N ₂ is 1.62 × 1.
^0-13 (W). Therefore, the noise power between N ₁ and N ₂ is approximately
There is a 3.3 dB difference.

In addition, the noise power N ₃ when there is no obstacle in the direction of arrival of the radio waves (R = 0.63 (times)) is 1.08 × in the same manner.
It is 10 ^-13 (W). Therefore, when there is no obstacle (R = 0.63) in the direction of arrival of radio waves during rain, and when there is an obstacle (R = 0.63)
O) and, there is a difference of about 1.8 dB between the noise powers N ₃ and N ₂ . In this way, even during fine weather or during rainfall, it is possible to determine whether there is an obstacle in the beam direction based on the difference in noise power between when there is an obstacle and when there is no obstacle.

The first embodiment will be described with reference to FIGS. The first embodiment is for receiving satellite broadcasts transmitted from broadcast satellites in a vehicle or train moving on land. In FIG. 1, 1 is an antenna, 2 is a drive unit, 3 is a control unit, 4 is a noise detection unit, and 5 is a determination unit.

The antenna 1 is a plane antenna 1 for receiving broadcast waves,
One dielectric plate 7 together with four control plane antennas 6
Are formed on the same surface.

The exercise unit 2 includes two motors 8 and the antenna 1
And a device for driving the dielectric plate 7 in order to change the azimuth angle and the elevation angle of the control antenna 6.

The control unit 3 supplies a control signal to the drive unit 2 so that the antenna 1 maintains a state in which the antenna 1 receives radio waves from a broadcasting satellite at a predetermined level or higher, based on the radio waves received by the control antenna 6. Is. However, when a stop signal is received from the microcomputer 16 described later, the antenna 1
It is configured to stop the search or tracking of the signal while maintaining the azimuth angle and the elevation angle of the same at the angle at that time.
The antenna 1, the control antenna 6, the drive unit 2, and the control unit 3 are conventionally known antenna automatic tracking devices,
For example, the automatic tracking device for the parabolic antenna described in the conventional example has a function of searching and tracking a broadcast wave. Therefore, detailed description thereof will be omitted. However, in this embodiment, one plane antenna 1 and four control plane antennas 6 are attached to one dielectric plate 7, but the main antenna provided on the parabolic reflector as in the conventional example. The primary radiator and the sub-primary radiator may be used instead of the planar antenna 1 and the control planar antenna 6.

The signal and noise received by the antenna 1 pass through the frequency converter 9 to become an IF signal, and this IF signal is supplied to the bandpass filter 11 coupled to the frequency converter 9 and the receiver 12. The bandpass filter 11 is for passing noise outside the reception band (a band near the reception frequency, in which no broadcast radio wave exists),
The noise that has passed through this enters the level detection circuit 13. The level detection circuit 13 converts noise into a DC level. The bandpass filter 11 and the level detection circuit 13 form the noise detection unit 4. The output signal of the level detection circuit 13 is branched into two signals, one input to the comparison circuit 15 via the hold unit 14 and one input directly to the comparison circuit 15. The output of the comparison circuit 15 is a microcomputer. Entered in 16. The hold unit 14 temporarily holds the noise level. The comparison circuit 15 determines whether or not the noise level detected by the level detection circuit 13 is higher than the noise level temporarily held by the holding unit 14, and outputs the determination result to the microcomputer 16. . The determination unit 5 is composed of the hold unit 14, the comparison circuit 15, and the microcomputer 16, and the level detection circuit 13,
The hold unit 14 and the comparison circuit 15 are a microcomputer 16
It is controlled according to the program. Also, the receiver 12
Outputs a signal indicating whether or not the antenna 1 is receiving a broadcast wave to the microcomputer 16.
The microcomputer 16 supplies the control unit 3 with a signal for operating the control unit 3 or a signal for stopping the control unit 3 based on these supplied signals.

Next, referring to FIG. 2, the microcomputer 16
The flowchart will be described. First, the azimuth and elevation of the dielectric plate 7 are changed and a signal is supplied to the control unit 3 so as to search for a radio wave from a broadcasting satellite (step 100). This search method uses a conventionally known method such as that described in the conventional example, and therefore a detailed description thereof will be omitted. Next, it is judged whether or not the antenna 1 is receiving the broadcast wave based on the output from the receiver 12 (step 10
2) If YES, the control unit 3 tracks the satellite signal.
A control signal is supplied to (step 104). If the determination in step 102 is NO, the process returns to step 100, and a control signal is supplied to the control unit 3 so as to search for a satellite signal. This tracking method also utilizes a conventionally known method as described in the conventional example.

Then, following step 104, it is determined whether or not a broadcast wave is being received (step 106), and if YES, the noise level detected by the level detection circuit 13 at this time is held in the hold unit 14 (step 108), and the step Return to 104 and continue tracking satellite signals. Therefore, the noise level held in the hold unit 14 is constantly updated to the latest level while the radio wave is being received. If the judgment in step 106 is NO, it is judged whether or not the noise level detected by the level detection circuit 13 is higher than the noise level held in the holding section 14 (step 110). If the determination in step 110 is YES, it can be determined that there is an obstacle in the radio wave arrival direction as described above. Therefore, the control unit 3 should stop tracking satellite signals.
(Step 112), returns to step 110, and returns to step 110 until the determination at step 110 becomes NO.
Repeat 0 and 112. When the determination in step 110 is NO, it is determined whether or not the broadcast wave is being received (step 114). Step 114
If YES is determined, it can be determined that the vehicle has exited from an obstacle, for example, a tunnel. Therefore, a control signal is supplied to the control unit 3 so as to restart tracking of the satellite signal (step 116).
Return to step 104. If the determination in step 114 is NO,
For example, as a result of passing through a winding tunnel or the like, the beam direction of the antenna 1 at the exit of the tunnel is greatly different from the arrival direction of the radio wave from the geostationary satellite, so that there is no obstacle, but reception is not possible, so go to step 100. return,
A control signal is supplied to the control unit 3 so as to search for a satellite signal.

Next, a second embodiment will be described. The second embodiment differs from the first embodiment in that the bandpass filter 11 of the first embodiment is different.
Was designed to pass noise outside the reception band.
The band-pass filter 11 of the embodiment is designed to pass the noise within the reception band, and the band-pass filter 11 passes the noise within the reception band. Since it cannot detect the noise level, the microcomputer 16 controls the level detection circuit 13 to operate when the broadcast wave is not received.
It is a change of the program. Since the other components are the same, detailed description thereof will be omitted and FIG. 1 is a block diagram of the second embodiment.

The program of the microcomputer 16 will be described with reference to FIG. First, the level of noise (the noise level when not blocked by a tunnel, a building, etc.) when the broadcast wave is not received is held in the hold unit 14 (step 200). Next, a control signal is supplied to the control unit 3 so as to search the radio waves from the broadcasting satellite by changing the azimuth angle and the elevation angle of the dielectric plate 7 (step 202). This search method uses a known method as described in the conventional example. Then, it is judged whether or not the antenna 1 is receiving the broadcast wave based on the output from the receiver 12 (step 204), and if YES, the control signal is sent to the control unit 3 so as to track the satellite signal. Supply (step 206). Step two
If the determination in 04 is NO, the process returns to step 202, and a control signal is supplied to the control unit 3 so as to search for a satellite signal. This tracking method also utilizes a conventionally known method.

Then, following step S206, it is determined whether radio waves are being received (step 208), and if YES, the process returns to step 206,
Continue tracking satellite signals. NO in step 208
If so, it is determined whether the noise level detected by the level detection circuit 13 is higher than the noise level held in the holding unit 14 (step 210). If the determination in step 210 is NO, the radio wave is not received, but the radio wave is not blocked by an obstacle, so the held noise level is erased at this time (when no radio wave is received). The noise level of 1 is held in the holding unit 14 (step 212), and the process returns to step 202 to supply a control signal to the control unit 3 so as to search for a satellite signal. If the determination in step 210 is YES, the radio wave is blocked by an obstacle, so the control signal is supplied to the control unit 3 so as to stop the tracking of the satellite signal (step 214) and the broadcast radio wave is being received. It is determined (step 216). If the determination in step 216 is NO, the radio wave is still blocked by an obstacle, so step
Returning to step 210, steps 210, 214 and 216 are repeated until the determination at step 216 becomes YES. If the determination in step 216 is YES, the radio wave is not blocked by an obstacle, so
A control signal for restarting tracking is supplied to the control unit 3 (step 218), and the process returns to step 206.

The determination unit 5 in FIG. 1 includes a holding unit 14 and a comparison circuit 15
It is composed of a level judgment circuit consisting of and the microcomputer 16, but instead of providing a level judgment circuit, an A / D converter is coupled between the level detection circuit 13 and the microcomputer 16, and an output signal of the A / D converter is provided. Based on this, the function equivalent to that of the level determination circuit can be achieved in the microcomputer 16.

〔The invention's effect〕

As described above, according to the present invention, it is possible to determine whether or not there is an obstacle in the arrival direction of a radio wave based on the noise level. The search for can be stopped. Therefore,
For example, since the response speed of the tracking device is slower than the speed of changing the direction of a moving object such as a vehicle or a train, there is an effect that the satellite signal search is not erroneously stopped when the satellite signal is cut off. Then, when a vehicle or train equipped with this automatic tracking antenna device enters a tunnel or the like,
Since the search is stopped, it is possible to prevent the mechanical parts such as the drive unit for changing the azimuth angle and the elevation angle of the antenna from being consumed, and it is possible to eliminate the waste of energy for rotating the antenna. . Further, as shown in FIGS. 3 (a) and 3 (b), when the antenna 1 is under the elevated structure 18 or when the broadcast radio wave 17 is temporarily cut off due to the shadow of the building 19, the azimuth angle of the antenna 1 Since the tracking is stopped while keeping the elevation angle as it is, when the antenna 1 gets out of the obstacle such as the elevated 18 etc., the antenna is receiving radio waves and the noise level is higher than the held noise level. Since it is also small, satellite signals are tracked promptly. Also, for example, when exiting a long and winding tunnel, the beam direction of the antenna and the arrival direction of the radio wave are different even though the shield is gone, and the antenna is not receiving radio waves, And since the noise level is smaller than the held noise level,
The satellite signal is searched promptly. Therefore, since the tracking or searching is appropriately performed according to the situation after the shield of the antenna in the beam direction is completed, the reception state of the satellite signal by the antenna is promptly restored.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of an automatic tracking antenna device according to the present invention, FIG. 2 is a flow chart showing a program of a microcomputer used in the same embodiment, and a third embodiment.
FIGS. 4A and 4B are diagrams showing an example in which an obstacle is interposed in the radio wave arrival direction of the antenna, and FIG. 4 is a flow chart showing a program of the microcomputer used in the second embodiment of the present invention. 1 ... Antenna, 2 ... Drive section, 3 ... Control section, 4 ...
Noise detector, 5 ... Judgment unit, 6 ... Control antenna, 12
...... Receiver, 13 ...... Level detection circuit, 14 ...... Memory section, 15
…… Comparison circuit, 16 …… Microcomputer.

Claims (2)

[Claims] 1. An antenna mounted on a moving object for receiving a signal from a geostationary satellite in the sky, a driving unit provided on the antenna so that its azimuth and elevation can be changed, and the antenna is provided from the geostationary satellite. Search means for supplying a control signal for changing the azimuth angle and elevation angle of the antenna to the drive section until the signal is received, and the antenna outputs a signal from the geostationary satellite at a predetermined level after the operation of the search means is completed. Tracking means for supplying the control signal to the drive section so as to receive the above, a noise detection section for detecting the level of noise outside the reception band of the antenna received by the antenna, and the antenna from the geostationary satellite And a noise level of the noise detection unit according to the hold command. The hold unit that is closed, the first condition that the noise level of the noise detection unit is higher than the noise level of the hold unit, and the second condition that the antenna is receiving a signal from the geostationary satellite. It is determined whether or not the tracking means is stopped when the first condition is satisfied, and the tracking means is activated when the first condition is not satisfied and the second condition is satisfied, and the first and second
An automatic tracking antenna device comprising: a second discriminating means for activating the searching means when the condition is not satisfied. 2. An antenna mounted on a moving object for receiving a signal from a geostationary satellite in the sky, a driving unit provided on the antenna so that its azimuth angle and elevation angle can be changed, and the antenna is provided from the geostationary satellite. Search means for supplying a control signal for changing the azimuth angle and elevation angle of the antenna to the drive section until the signal is received, and the antenna outputs a signal from the geostationary satellite at a predetermined level after the operation of the search means is completed. Tracking means for supplying the control signal to the drive section so as to receive the above, a noise detection section for detecting a noise level in the reception band of the antenna received by the antenna, and a beam direction of the antenna in advance. The noise level of the noise detector in the unblocked state is held, and when the hold command is received, the noise level of the noise detector is held. And the first condition that the noise level of the noise detection unit is higher than the noise level of the hold unit and the second condition that the antenna is receiving a signal from the geostationary satellite. In the unsatisfied state of the second condition, the tracking means is stopped when the first condition is satisfied, and in the stopped state, the tracking means is operated to operate the first and An automatic tracking antenna apparatus comprising: a determination unit that supplies the hold command to the hold unit and operates the search unit when the two conditions are not satisfied.