JPS62129767A - Automatic tracking system - Google Patents

Abstract

PURPOSE:To enable a stable automatic tracking having the best of advantages of two tracking systems, by using both a driving by a step track system and an estimation tracking. CONSTITUTION:A step track judgement means 11 determines the subsequent driving position based on an angle data from an angle-reading circuit 8 and a level motor from a reception-level-reading circuit 9. On the other hand, an angle memory means 12 stores locuses created in the previous tracking of antennas for satellites as angle data. An orbit estimating means 13 reads angle data out of the means 12 to estimate an orbit. A comparison means 14 compares an output of the means 11 with an output of the means 13. When the resulting differences are smaller than predetermined values, a selector means 15 selects an output of the means 11. On the other hand, when the difference between the two outputs is larger than the predetermined value, the output of the means 13 is selected. This assures a stable automatic tracking with the antenna free from errors regardless of any violent changes in the reception level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic tracking system using a step track system.

[Conventional technology]

The step track method is a method in which the antenna is mechanically driven to change the pointing direction by a small angle, and the received signal level before and after this change is compared and judged, and the antenna's pointing direction is controlled so that the received level is maximized. It is. This method has a slow response time.

It does not require a complicated tracking receiver like the Mono/PLS method, and is a simple and economical automatic tracking method for earth station antennas that target artificial satellites whose positions change slowly, such as geostationary satellites. Widely used.

This method will be explained below.

FIG. 3 is a block diagram of a step-trunk type tracking device. In the figure, a beacon signal wave received by an antenna 1 is converted by a receiving device 2 into a DC signal proportional to the reception level. This signal is converted into a digital signal by a sampling circuit 6 in the automatic tracking control device 3 and then supplied to a drive logic determining circuit 7 for level determination. The drive logic judgment circuit 7 performs processing predetermined by a microprocessor, and determines whether the antenna 1 The next direction to be driven is determined, and a drive command signal is sent to the drive circuit 4. In this way, the antenna 1 is oriented in the direction where the reception level of the incoming radio waves becomes higher.

FIG. 4 is a flowchart for explaining the basic operation of the drive logic determining circuit, and will be explained step by step.

(1) Integrate the reception level over a certain period of time with the antenna stationary and store the value L1.

(11) Next, the antenna is driven stepwise around the rotation axis 2 (for example, X-axis rotation) by a minute angle Δθ.

(iiiJ Step (1) after the antenna comes to rest)
The received signal level is measured in the same manner as above, and the value L2 is stored.

(iv) Compare L, and L2, and if L, (L2, continue to drive the antenna in the same direction, conversely, Ll>L
If it is 2, reverse the driving direction of the antenna and change it to L1KL.
The same operation is repeated until 2 (ILI -L21<ΔL).

By switching the drive axis from the X axis to the Y axis when the L exhaust reaches L2 and repeating the above operation several times, the antenna can be correctly directed toward the satellite.

FIG. 5 is an antenna pattern characteristic diagram showing the relationship between the minute angle Δθ and the change ΔL in the received signal level.

For example, when step driving is performed from θ1 to 02, if there is no change in the intensity of incoming radio waves, the received signal changes from L1 to L2 and decreases by the change ΔL due to antenna driving. And L
Since 2-Ll<0, the next driving direction is reversed from θ2 to θ1 and driven in the direction of the peak of the main turn.

[Problem that the invention seeks to solve]

However, when the reception level fluctuates drastically.

For example, if the reception level increases by ΔL after measuring L as shown in FIG. 5 and before measuring L2, it changes from L1 to L3. Here, ΔL, )ΔLo.

L3-Ll>0, resulting in an incorrect judgment.

As a result, the antenna is driven in the direction opposite to the peak in the next step, such as from θ2 to θ3. Normally, when stepping to reduce the tracking error, the frequency of the above-mentioned error in judgment is high. Become. Also.

If the reception level continues to rise when the rain is stopping or there are two long periods of scintillation.

This error in judgment also occurs continuously, and the antenna is increasingly driven in the direction opposite to the peak, eventually making it impossible to receive normally.

An object of the present invention is to eliminate such drawbacks and provide a stable automatic tracking system that does not cause tracking errors even when the reception level fluctuates rapidly.

[Means for solving problems]

In the present invention, in an automatic tracking method using a step trunk method, which compares reception levels before and after step driving of an antenna and performs step driving of the next antenna in a direction in which the reception level increases, the antenna is means for storing the trajectory of tracking the artificial satellite, and means for calculating the predicted trajectory from this stored data;
It is characterized by comprising means for comparing the drive position based on the logical judgment of the step track and the predicted trajectory, and means for switching between driving based on the logical judgment of the step track and driving based on the predicted trajectory according to the comparison result of the comparison means. shall be.

[Effect]

In other words, when the next trajectory is predicted from the trajectory that the antenna has been tracking so far, and the drive command based on the logical judgment of the step track causes the antenna to deviate greatly from the predicted trajectory, the antenna is forced to move in the direction of the predicted trajectory. Switch and drive.

〔Example〕

Referring to FIG. 1, in addition to the conventional antenna driving based on logical judgment of step tracks by the step track determination means 11, the present invention also includes antenna driving based on trajectory prediction by the angle storage means 12 and trajectory prediction means 13. I am making it possible for you to do so. The step track determination means 11 is.

The next driving position is determined based on the angle data from the angle reading circuit 8 and the level data from the reception level reading circuit 9. On the other hand, the angle storage means 12.

The antenna tracks the satellite in the past and stores it as angle data. Further, the trajectory prediction means 13 reads angle data from the angle storage means 12 and predicts the trajectory.

The driving based on logical judgment of the step track and the driving based on trajectory prediction are switched by a switching means 15 which switches according to the comparison result of the comparing means 14. That is, the comparison means 14 compares the output of the step track determination means 11 and the trajectory prediction means 1.
Compare with the output of 3. If the difference between them is smaller than a predetermined value, the switching means 15 selects the output of the step track determining means 11. On the other hand, if the difference between the two outputs is greater than a predetermined value, the output of the trajectory prediction means 13 is selected. The above control is performed by a microprocessor.

The above-mentioned control is carried out by converting the flowchart shown in FIG.
This can be achieved by replacing the "Antenna Drive # (Step 11)" part in the figure. Once the drive direction is determined in the step track flow in Figure 4, the flow in Figure 2 is entered before actually driving the antenna. Determine the true driving direction.

Referring to FIG. 2, first, in step (V), it is confirmed whether sufficient past tracking angle data to calculate the predicted trajectory is stored in the storage means. This is because the predicted trajectory cannot be calculated in the initial state when the power is turned on, so the device is driven unconditionally in the direction determined by the step track. Once it is confirmed that enough data has been stored, the predicted trajectory will be calculated using this data. next.

In step (1), the predicted trajectory and the drive position based on the logical judgment of the step track are compared, and if the difference does not exceed a predetermined value, the step track is driven to the position based on the logical judgment.

On the other hand, if the difference exceeds D, the antenna is directed in the direction of the predicted trajectory. Thereafter, in step (vii), the current antenna position is stored in the storage means and the process returns to the step track logic of FIG. 4 again.

By the way, when tracking an artificial satellite whose position changes slowly, such as a geostationary satellite, error-free tracking can be achieved by driving the antenna with priority given to the predicted orbit. However, if tracking is performed using only the predicted trajectory, the antenna will gradually deviate from the true direction of the satellite over a long period of time. The present invention can be said to be a tracking method that combines the advantages of the step track method and the tracking method based on trajectory prediction and compensates for the disadvantages. That is, when fluctuations in the received level are small and step tracking does not cause errors, driving is performed by step tracking, and when level fluctuations become severe, stable tracking is performed using the predicted trajectory.

There are various methods for calculating the predicted trajectory, but a simple extrapolation method is sufficient for the trajectory calculation used here.

- For example, in the second-order extrapolation method, the predicted value of the next step is calculated using data from three points among periodically sampled past orbital positions. When choosing these three points,
The longer the time interval between data, the stronger the influence of past trajectories becomes, and the predicted trajectory becomes less influenced by current tracking results. On the other hand, if the interval is short, the predicted trajectory will be influenced by the current tracking results and will change easily. Therefore, when the reception level fluctuates rapidly and the frequency of step track logical judgment errors is high, the time interval between data is lengthened to prevent the predicted trajectory from changing easily. Conversely, when there is little variation in the reception level, the time interval between data is shortened to control the predicted trajectory to quickly follow the trajectory based on the step track.

In this way.

More stable satellite tracking, which combines the advantages of step tracking and predictive tracking, can be performed depending on the fluctuation state of the reception level.

In order to perform such control in the present invention, specifically, the number of times the difference between the antenna drive position and the predicted trajectory during step track driving exceeds a predetermined value d is counted, and the control the time interval of data when performing predictive calculations. However, the value d is selected to be small enough to make the above-mentioned forced direction in the direction of the predicted trajectory.

According to this method, the predicted trajectory does not change easily even if the fluctuations in the reception level become severe and the frequency of step-track logic judgment errors increases. It is possible to track satellites without leaving orbit. Furthermore, when there is little variation in the reception level, the predicted trajectory quickly follows the trajectory based on the step track, and the same characteristics as tracking the satellite using only the step trunk can be obtained.

Note that in the above explanation, the time interval of data for prediction calculation is controlled based on the frequency at which logic errors occur in the step track, but the same result can be obtained by determining the variation in the sampling value of the reception level and controlling it using this amount. It is clear that a significant effect can be obtained. Further, the controlled value may be the order of prediction calculation instead of the time interval between data.

〔Effect of the invention〕

As explained above, the present invention can perform stable automatic tracking that combines the advantages of both tracking methods by using step-track driving and predictive tracking.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
The figure is a flowchart diagram showing the operation of the main part of the present invention.
4 is a block diagram of a conventional step track device, FIG. 4 is a flowchart showing a general step track operation, and FIG. 5 is an antenna/q-turn diagram for explaining the step trunk operation. In the figure, 12 is an angle storage means, 13 is a trajectory prediction means, and 14
15 is a comparison means, and 15 is a switching means. Figure 2

Claims (1)

[Scope of Claims] 1. An automatic tracking method using a step track method in which reception levels before and after step driving of an antenna are compared and control is performed such that the step drive of the next antenna is performed in a direction in which the reception level increases, means for storing the trajectory of the satellite that the antenna has tracked so far, means for calculating a predicted trajectory from this stored data, means for comparing the drive position based on logical judgment of the step track with the predicted trajectory, and said comparison. An automatic tracking method characterized by comprising means for switching between drive based on logical judgment of a step track and drive path based on a predicted trajectory in accordance with a comparison result of the means. 2. In the automatic tracking method according to claim 1, when calculating the predicted trajectory, the number of times the difference between the drive position determined by the logical judgment of the step track and the predicted trajectory exceeds a predetermined value is counted. An automatic tracking method characterized in that the time interval between data when calculating the predicted trajectory is changed according to the counted value.