JP3700384B2 - Communication device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication device, and more particularly to a communication device having an improved antenna tracking method for communicating with a satellite.
[0002]
[Prior art]
Conventional communication devices include those described in Yamamoto et al., “Antenna Tracking System Suitable for Land Mobile Satellite Communication” published in the Journal of the Institute of Electronics, Information and Communication Engineers dated December 14, 1990.
[0003]
There are two examples listed here,
In the first example, a closed loop method is used in which a signal from a communication relay station is used to obtain the position of the communication relay station with respect to the moving body.
[0004]
In the second example, an open loop method is used in which the position of the communication relay station with respect to the mobile body is determined based on the known position information of the communication relay station and the direction measurement sensor information mounted on the mobile body.
[0005]
[Problems to be solved by the invention]
In the closed loop method, a step track method is generally used as a method for searching for a point where the intensity of the signal from the satellite is maximum, but there are a plurality of local maximum points in addition to the maximum point. There is a problem that it is easy to fall into a local maximum and it is difficult to automatically search for this maximum point.
[0006]
Also, in the correction loop that operates when the reception level decreases, the signal from the satellite usually changes by about 1 dB. Therefore, if the threshold value is decreased, antenna vibration occurs, and if the threshold value is increased, the tracking accuracy deteriorates. There was a problem to do. There is also a problem that the control of the correction loop is easily affected by fluctuations in the communication signal level due to reflected waves of the surrounding buildings and rainfall.
[0007]
In addition, although the step track method is often used for the correction loop, the step track method has a problem that a certain amount of error always occurs due to the search because the search is performed.
[0008]
Also, in the case of tracking using the conventional closed loop method, since a correction is made in a feedback manner with respect to the deviation between the maximum signal strength and the current received signal, a certain amount of error is always avoided. In addition, when the satellite viewing position is moving, or when the communication device is mounted on a moving body, if the satellite viewing position or the moving body changes rapidly, the satellite There was a problem that tracking was not possible.
[0009]
Accordingly, a first object of the present invention is to realize high-speed automatic acquisition without falling into a local maximum when acquiring a satellite by searching for the maximum point of the signal strength from the satellite in satellite communication. To provide a communication device.
[0010]
In addition, the second object of the present invention is communication that can realize stable tracking even if the signal intensity pattern of the communication radio wave fluctuates due to fluctuations in the communication signal level due to reflected waves from surrounding buildings, etc., or rainfall. To provide the equipment.
[0011]
[Means for Solving the Invention]
In order to achieve the first object, in the present invention, the database has a pattern in which the communication intensity has a plurality of local maximums with respect to a change in the antenna directivity angle, and the given antenna directivity angle and communication intensity are obtained. The antenna is driven and controlled at a position where the communication strength is increased by updating the pattern so as to be matched and identifying the position in the updated pattern in the database .
[0012]
A communication device for achieving the second object is:
The communication device reconstructs the database of antenna directivity characteristics based on received signal strength information when the communication device is used.
[0013]
According to the present invention,
Based on the antenna directivity characteristics database input in advance, the signal strength under search can be evaluated, and the communication direction of the antenna can be controlled so that the received signal strength of the antenna is maximized, resulting in a local maximum. The communication direction control of the antenna can be realized.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
[0015]
As shown in FIG. 1, the communication device 100 communicates with the ground station 300 via a satellite 200 that functions as a communication relay station.
[0016]
The communication device 100 includes an antenna 110 for communicating with the satellite 200, a communication data transmitter 120, and a communication data receiver 130.
[0017]
In addition, the communication device 100 includes an antenna driving mechanism 140 and an antenna control device 150.
[0018]
The antenna control device 150 calculates the direction in which the antenna 110 is directed in the direction in which the intensity of the radio wave from the satellite 200 is maximum based on the signal of the communication data receiver 130, and passes through the motor driver 152. The communication direction of the antenna 110 is controlled by driving the antenna driving mechanism 140.
[0019]
The antenna driving mechanism 140 is an azimuth-elevation system in the embodiment of FIG. 1, and motor units 141 and 142 including servo sensors and motors are driven by a signal from the antenna control device 150 to reduce the speed reducer. The direction of the antenna 110 attached to the mechanism unit 145 is changed by driving the elevation angle mechanism 146 and the azimuth angle mechanism 147 configured by bearings or the like as the components of the mechanism unit 145 via 143 and 144.
[0020]
Next, the operation of this embodiment will be described.
[0021]
The structure of the database 400 included in the antenna control device 150 will be described with reference to FIG.
[0022]
FIG. 2 shows a database generally called a multilayer perceptron, which has an input layer 510, an intermediate layer 520, and an output layer 530.
[0023]
Next, a database construction algorithm will be described.
[0024]
E _p : error function t _pj for antenna directivity characteristic pattern: expected output of j-th unit for pattern p (defined only for output layer 530)
o _pj : Actual output of the j-th unit for pattern p w _ij : Weight from unit i to unit j f _j : Below threshold function, f _j is f (net) = 1 / (1 + exp (−k · net ) (Formula 1)
This will be described in Algorithm 1 using the sigmoid function defined in (1).
[0025]
(Algorithm 1)
Algorithm 1 is composed of the following steps 1 to 5.
[0026]
Step 1: Initialization of weights and thresholds All weights and thresholds are determined by small random numbers.
[0027]
Step 2: Fixed antenna directivity angle (X _p = x ₀ , x ₁ ,..., X _n-1 ) and electric field strength (T _p = t ₀ , t _{1 ,. -1} ) to the database. Here, n and m are the numbers of input and output units, respectively. Let w ₀ be −θ (threshold) and x ₀ be always 1. X _p and T _p are paired.
[0028]
Step 3: Output of each unit from the calculation input layer of the network output to the output layer _{o pj = f [Σw ij x} i] ... ( Equation 2)
Is calculated (from 0 to n-1 for i). F in (Expression 2) is a sigmoid function defined in (Expression 1).
[0029]
Step 4: Update the weight for each layer from the output layer to the input layer using the weight update (Formula 3).
[0030]
w _{ij (t + 1)} = w _{ij (t)} + ηδ _pj o _pi + α (w _{ij (t)} −w _{ij (t−1)} ) (Equation 3)
Here, w _{ij (t)} represents the weight from unit i to j at time t (t-th learning), η represents a gain term for adjusting the amount of change in weight, and δ _pj represents the unit error amount for pattern p. . Α is a moment term and 0 <α <1.
[0031]
δ _pj is for the output layer
δ _pj = k · o _pj (1−o _pj ) (t _{pj −opj} ) (Formula 4)
For the middle tier
δ _pj = k · o _pj (1-o _pj ) Σδ _pk w _jk ... (Formula 5)
Is calculated as The sum of Σ in Equation 5 is assumed to be over all the units k belonging to the layer above the layer to which the unit j belongs.
[0032]
Step 5: Repeat Step 2 to Step 4 until the actual output is sufficiently close to the expected output.
[0033]
According to this algorithm 1, the weight W _ij is stored in the database 400 as data associating the antenna direction change with the communication strength.
[0034]
FIG. 3 shows the directivity characteristics of a standard antenna.
[0035]
The horizontal axis in FIG. 3 represents a relative angle with the direction (angle) in which the communication signal strength of the antenna is maximized being zero. In the vertical axis of FIG. 3, the relative gain with the maximum communication signal strength point of the antenna as 0 is in decibels. In Algorithm 1, data on the horizontal axis is used as X _p and data on the vertical axis is used as T _p .
[0036]
When communication is started in the communication device 100, the antenna 110 is driven by the antenna control device 150, the strength of the communication data taken into the antenna control device 150 via the communication data receiver 130, and the motor units 141 and 142. Based on the driving angle information of the motor units 141 and 142 captured in the antenna control device 150, the current position in the antenna directivity characteristic pattern of FIG. 3 can be identified using the database 400 constructed based on the algorithm 1 described above. . After identifying the current position, the maximum point of the communication strength can be narrowed by driving the antenna 110 so that the celestial angle (degree) in FIG.
[0037]
Next, a second embodiment of the present invention will be described.
[0038]
In the communication apparatus of FIG. 2, the database 400 is already constructed and stored in the memory 500. Assume that the memory 500 is a read-only memory such as a ROM.
[0039]
When communication is started, the database 400 in the memory 500 is read into another memory 600. The memory 600 is assumed to be a readable / writable memory such as a RAM.
[0040]
When communication is started in the communication apparatus 100, the maximum communication strength point is captured by the method described in the first embodiment.
[0041]
After capture, the antenna 110 is driven by the antenna control device 150, the strength of the communication data taken into the antenna control device 150 through the communication data receiver 130, and the antenna control device 150 through the motor units 141 and 142. Based on the driving angle information of the motor units 141 and 142, the database 400 in the memory 600 is reconstructed based on the algorithm 1 described above.
[0042]
The present invention is not limited to the database mode in the above embodiment, and various modifications can be made without departing from the gist of the present invention.
[0043]
【The invention's effect】
As described above, according to the present invention, the communication direction of the antenna that maximizes the received signal strength of the antenna can be captured in a short time, and the variation pattern of various antenna directivity characteristic patterns can be obtained. It is possible to provide a communication device capable of robust and highly accurate communication direction control.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of a communication apparatus according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a database according to the first embodiment of the present invention.
FIG. 3 is a diagram showing directivity characteristics of an antenna.
FIG. 4 is a system configuration diagram of a mobile communication device according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 ... Communication apparatus, 110 ... Antenna, 120 ... Communication data transmitter, 130 ... Communication data receiver, 140 ... Antenna drive mechanism, 141 ... Motor unit, 142 ... Motor unit, 143, 144 ... Reduction gear, 145 ... Mechanism part DESCRIPTION OF SYMBOLS 146 ... Elevation angle mechanism, 147 ... Azimuth angle mechanism, 150 ... Antenna control apparatus, 151 ... Control calculating part, 152 ... Motor driver, 200 ... Satellite, 300 ... Fixed station, 400 ... Database, 410 ... Input layer, 420 ... Middle Layer, 430 ... Output layer, 500,600 ... Memory.

Claims (2)

A communication device having an antenna, comprising a drive device for driving the antenna and a control device for controlling the drive device, wherein the control device has a pattern in which the communication intensity has a plurality of local maximums with respect to a change in antenna directivity angle. Is used as a database, and the pattern is updated so as to be suitable for a given antenna directivity angle and communication strength, and the position in the updated pattern of the database is identified, thereby increasing the communication strength. The communication device controls the drive device to move the antenna. In the drive control device that controls the driving of the antenna, it has a pattern that has multiple local maximal communication strengths against changes in the antenna directivity angle, and it conforms to the given antenna directivity angle and communication strength. The antenna drive control apparatus which moves an antenna to the position where the said communication strength becomes large by updating the said pattern so that it may identify, and identifying the position in the updated pattern of the said database . "

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