JP3530497B2 - Directivity pattern measurement system and method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a directional pattern measuring system and method, and more particularly to a low altitude orbit (altitude several 100 km to several 1000 km) or a medium altitude orbit (altitude 1).
The present invention relates to a directional pattern measurement indicating system and method for easily and quickly measuring an antenna directional pattern and a mirror surface shape using radio waves radiated from a satellite that orbits the earth (about 10,000 km).

[0002]

2. Description of the Related Art Generally, a large-diameter (large-sized) parabolic antenna (particularly, a large-diameter radio telescope used in radio astronomy) adopts a flexible structure that allows structural deformation due to its own weight on the mirror surface and its supporting mechanism. ing. An antenna adopting such a flexible structure causes the mirror surface to be gravitationally deformed by the elevation angle of the antenna, but the focal length only changes after the deformation, and the shape of the mirror surface itself maintains a hyperbolic shape, so-called homologous. It is based on the modified design.

[0003]

However, in a telescope actually manufactured, the directional pattern and the main mirror surface shape are not always ideal due to various factors such as the accuracy of determining the focal position, the mirror surface, and the secular change of the support structure. It is hard to say that the shape is maintained. Therefore, it is important to measure the directivity pattern and the mirror surface shape for each elevation angle of the antenna.

In the measurement of the directional pattern of the antenna, a reference radio wave source installed on a measuring tower or a high mountain far away is usually formed at a point considered sufficiently far from the antenna to be measured. , Change the direction of the antenna and record the strength of the received signal (radio field strength). However, when the reference radio wave source is installed on a measuring tower or a mountain, the elevation angle with respect to the reference radio wave source viewed from the antenna cannot be set so large. Therefore, when measurement is performed at a high elevation angle, for example, a beacon radio wave (beacon signal) of a geostationary satellite may be used.

However, in the above method, since the position of the radio wave source is fixed, the measurable elevation angle cannot be set to an arbitrary value. On the other hand, as a method capable of setting the elevation angle to an arbitrary value, for example, measurement using an astronomical object having a very strong radio wave intensity has been attempted. However, with this method, it is assumed that it is difficult to accurately measure the directional pattern because the altitude of the celestial body changes from moment to moment while the antenna is scanning the celestial body that is the radio source. To be done. Therefore, a method using a non-geostationary satellite has been attempted in order to measure the directivity pattern at an arbitrary elevation angle. However, since this method uses only one satellite, it takes a long time to accurately measure the beam shape, and the environmental changes around the antenna (for example, uneven distribution in the atmosphere Strict measurement was difficult due to water vapor, water drops, etc.).

Here, a technique related to the present invention will be described. As a reference radio wave source required when measuring a directivity pattern of an antenna, the inventors of the present invention presume that it is ideal to be able to set positions at various elevation angles, and mobile bodies that have become widespread in recent years Low altitude orbit (100k altitude) in communications and global networks
Attention was paid to a communication system in which a plurality of small satellites (for example, non-geostation type communication satellites) orbiting the earth orbit in the range of m to several 1000 km) or medium altitude orbit (altitude of about 10,000 km) is orbited.
Furthermore, the present inventors have paid attention to the fact that a reference power source can always be secured on the celestial sphere by using a plurality of beacon radio waves radiated by such a plurality of non-stationary communication satellites.

In view of the above points, the present invention uses the beacon signals from a plurality of non-geostationary satellites by fixing the elevation angle of the measurement target antenna, and thereby the accurate two-dimensional measurement of the measurement target antenna for a certain elevation angle is performed. The purpose is to measure a directivity pattern (for example, a radio wave intensity for each elevation angle, a sensitivity pattern). It is another object of the present invention to accurately and inexpensively evaluate the performance of a large antenna.

Another object of the present invention is to perform a strict directional pattern measurement that does not in principle involve movement in the elevation angle direction, which affects the gravitational deformation of the mirror surface of the antenna. It is another object of the present invention to measure the deformation of the two-dimensional directivity pattern associated with the deformation of the mirror surface shape due to the change of the elevation angle in the measurement target antenna (large antenna).

[0009]

According to the first solution of the present invention, the elevation angle is set to a predetermined angle, and a first antenna for receiving radio waves radiated from a plurality of satellites, and the first antenna. A first receiver that converts the radio field intensity received by the first data into first data, and stores a first data string including a plurality of the first data sampled at a plurality of times at each time in a first file; A second antenna arranged near the first antenna for receiving the radio wave;
The radio field intensity received by the second antenna is converted into second data, and a second data string including a plurality of second data obtained by sampling a plurality of times at each time is used as a second data string.
A second receiver stored in a file, a satellite position data file storing the elevation angle and azimuth angle of the satellite indicating the position of the satellite at each time, and the first and second at a certain time from the first and second files. The data is read, the intensity ratio between the first data and the second data is obtained, the calibration radio wave intensity by the first antenna is calculated, and further, the elevation angle and azimuth angle of the satellite are read from the satellite position data file, A calibration computer that creates a plurality of calibration result files including the calibration radio field intensity, the elevation angle and the azimuth angle of the first antenna by associating with the elevation angle and the azimuth angle of the first antenna, and the plurality of calibration result files. The elevation angle and azimuth angle of the first antenna and the calibration radio field intensity are read from the first antenna, and the two-dimensional directivity pattern of the first antenna is calculated.
Provided is a directional pattern measurement system including a data processing device that creates a directional pattern file including a two-dimensional directional pattern at an elevation angle of a predetermined angle of an antenna.

According to the second solving means of the present invention, the elevation angle is set to a predetermined angle, and the radio field intensity received by the first antenna for receiving radio waves emitted from a plurality of satellites is converted into first data. Storing a first data string including a plurality of the first data sampled at a plurality of times at each time point in a first file, and being arranged in the vicinity of the first antenna to receive the radio wave Second
Converting the radio field intensity received by the antenna into second data, storing a second data string including a plurality of the second data sampled for each time at the time in a second file; And 2 files at a certain time, the first and second data are read, the intensity ratio between the first data and the second data is obtained, the calibration radio wave intensity by the first antenna is calculated, and the time of each of the satellites is calculated. The elevation and azimuth of the satellite are read from the satellite position data file that stores the elevation and azimuth of the satellite, and the calibration radio field intensity is associated with the elevation and azimuth of the first antenna. A step of creating a plurality of calibration result files including an elevation angle and an azimuth angle of the first antenna; and an elevation angle of the first antenna from the plurality of calibration result files. And a azimuth angle and a calibration radio field intensity are read, a two-dimensional directivity pattern of the first antenna is calculated, and a directivity pattern file including a two-dimensional directivity pattern at an elevation angle of the first antenna is created. There is provided a directional pattern measuring method including:

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. A. Configuration of Directional Pattern Measurement System FIG. 1 shows a directional pattern measurement system 1 according to the present invention.
It is a schematic block diagram of 00. The directional pattern measurement system 100 includes, for example, a measurement target antenna 10, a first receiver 15, a reference antenna 20, and a second receiver 25.
The orbit prediction computer 30, the calibration computer 40, the data processing device 50, the satellite 60, and the storage device 70 are included. The storage device 70 stores, for example, the measurement antenna file 7
1, a reference antenna file 72, a satellite position data file 73, a calibration result file 74, and a directivity pattern file 75. In addition, the satellite 60 is, for example, a low altitude (100 km to several 1000 km altitude) in the orbit of the earth.
Or, it is a non-geostationary satellite that rotates at a medium altitude (altitude of about 10,000 km) and emits a beacon signal.

Here, the matters relating to the directional pattern measuring system 100 relating to the present invention will be outlined. The directional pattern measurement system 100 receives radio waves (non-modulated radio waves, for example, beacon signals) from a plurality of satellites 60 in a state where the elevation angle of the measurement target antenna 10 which is a large-diameter antenna is fixed, and thereby a certain elevation angle is obtained. Is a system for measuring an accurate two-dimensional directivity pattern of the measurement target antenna 10 ("directivity pattern" means reception and / or transmission radio wave intensity at a certain elevation angle).

Generally, a large-diameter antenna has a drive axis (here, an azimuth axis) in a direction parallel to the direction of gravity (vertical direction).
And a drive shaft (here, an elevation angle axis) in a direction perpendicular to the vertical direction. Here, in principle, the gravitational deformation of the large-diameter antenna mainly occurs only when the antenna is rotated around the elevation angle axis, so the shape deformation of the antenna occurs only when the antenna is moved in the elevation axis direction. Assuming that, even if the antenna is moved in the azimuth axis direction to capture the satellite 60, the shape deformation of the antenna does not occur (or the deformation has little effect).

The antenna 10 to be measured is a large (large-diameter) antenna that waits for the satellite 60 by predicting the orbit (arrow in the figure) of the satellite 60, and receives the beacon signal from the satellite 60. It has a mirror surface such as a substantially hyperbolic shape. The first receiver 15 transmits, for example, unmodulated radio waves such as beacon radio waves radiated by the satellite 60 to the measurement target antenna 10
Amplifies the voltage value (information proportional to the received radio wave intensity) obtained by receiving as input data, converts it to a frequency that can be captured by the internal A-D converter, and then samples with this A-D converter, The time-series digital data is stored in the measurement antenna file 71 in the storage device 70. The sampling rate depends on the frequency fluctuation range of the received signal due to the Doppler effect accompanying the movement of the satellite 60, but can be set to, for example, about 1 MHz.

The reference antenna 20 is, for example, a satellite 60.
Is a small antenna for always tracking, and is arranged in the vicinity of the measurement target antenna 10 to calibrate fluctuations due to atmospheric absorption of beacon radio waves received by the first receiver 15 and differences in radiation intensity for each satellite 60. belongs to. The second receiver 25 amplifies, as input data, a voltage value (information proportional to the received radio wave intensity) obtained when the reference antenna 20 receives an unmodulated radio wave such as a beacon radio wave radiated by the satellite 60. Then, after the frequency is converted into a frequency that can be taken in by the internal A / D converter, sampling is performed by this A / D converter, and the data is stored in the storage device 7 as time series digital data.
The reference antenna file 72 in 0 is stored. Note that the sampling rate is 1 MHz as in the first receiver 15.
It can be a degree.

Further, the orbit prediction computer 30 predicts the orbit of the satellite 60, and performs processing for controlling the antenna 10 to be measured and the reference antenna 20 to face in that direction. The satellite position data file 73 in the storage device 70 is, for example, position data for each time of the satellite 60 (here, the satellite position data includes "satellite azimuth" and "satellite azimuth", which have general versatility. "Elevation" is stored, but the position data of this satellite and the target antenna 1
0 and "azimuth" of the two drive axes of the reference antenna 20
Information about the relative relationship with the “elevation angle” may also be stored. ) Is remembered. The orbit prediction computer 30 controls the directions of the measurement target antenna 10 and the reference antenna 20 based on the position data of the satellite 60 at a desired time stored in the satellite position data file 73. As a result, the measurement target antenna 10 can predict the passage point (arrow in the figure) of the satellite 60 and wait for the satellite 60. The reference antenna 20 can also drive the drive shaft (not shown) according to the position data of the satellite 60 to constantly track the satellite 60.

The calibration computer 40 uses the measurement antenna file 7 in the storage device 70 created by the first receiver 15.
1 and the reference antenna file 72 in the storage device 70 created by the second receiver 25, and the storage device that stores the position data (satellite angle, elevation angle) of the satellite 60 when these files are created. Each data is read from the satellite position data file 73 in 70, and the azimuth of the satellite is corrected by calibrating the fluctuation of the beacon radio wave received by the first receiver 15 due to the atmospheric absorption and the difference of the radiation intensity for each satellite 60. Data including the calibration result corresponding to the elevation angle is stored in the calibration result file 74 in the storage device description 70.

The data processing device 50 is a calibration computer 40.
A two-dimensional directivity pattern (radio wave intensity) of a certain elevation angle is created based on the calibration result file 74 that stores a plurality of data for each of a plurality of satellites 60 having different orbits, and is calculated by changing the elevation angle. By processing, the radio field intensity for each elevation angle is calculated, and this data is stored in the storage device memory 7.
It is stored in the directivity pattern file 75 in 0.

B. Operation of directional pattern measurement B-1. Operation Outline FIG. 2 shows a directional pattern measurement system 1 according to the present invention.
00 is a flowchart. It should be noted that, for convenience of description, the description of the flow chart here is a schematic one, and a specific description will be given later. First, in step S101,
The orbit prediction computer 30 calculates the orbit of the satellite 60 passing over the measurement target antenna 10 based on the satellite position data file 73 read from the storage device 70 by the orbit prediction computer 30 in advance.

FIG. 3 is an explanatory diagram of the satellite position data file 73. The satellite position data file 73 is
It includes general-purpose position data "satellite azimuth" and "satellite elevation" for indicating the position of a certain satellite 60. The measurement target antenna 10 is rotated in the azimuth axis direction according to the calculated orbit of the satellite 60 with the elevation angle kept constant under the control of the orbit prediction computer 30, and the satellite 60 causes the beam of the measurement target antenna 10 to rotate. It waits to pass through the inside (range in which radio waves can be received), and receives unmodulated radio waves such as beacon signals from the satellite 60 (S101). The reference antenna 20 arranged in the vicinity of the measurement target antenna 10 similarly drives the drive shaft according to the calculated orbit of the satellite 60 under the control of the orbit prediction computer 30 to track the satellite 60 and beacon it. The signal strength is constantly measured.

Next, in step S103, the first receiver 15 makes the obtained radio field intensity correspond to the time based on the beacon signal received by the measurement target antenna 10 and the measurement antenna file 71 in the storage device 70. Remember. Further, the second receiver 25 stores the obtained radio field intensity in the reference antenna file 72 in the storage device 70 corresponding to the time based on the beacon signal received by the reference antenna 20.

Here, FIG. 4 shows an explanatory view of each file stored in the storage device 70. FIG. 4 shows an explanatory diagram of the measurement antenna file 71 and the reference antenna file 72. The data format after sampling by the first receiver 15 is, for example, no header, 1 data is 2
It corresponds to Byte (1 Word), 1 pps synchronization signal (1 bit: “A” in the figure), and spare external input 1
(1 bit: “B” in the figure), spare external input 2 (1 bit: “C” in the figure), and spare external input 3 (1 bit:
In the figure, "D") and A-D converted radio field intensity data (12 bits) are included.

The recording format is, for example, data (8
Bits: "Day" in the figure), data indicating the hour (8 bits: "hour" in the figure), data indicating the minute (8 bits: "minute" in the figure), and data indicating the second ( 8-bit: In the figure,
"Second") and a plurality of sampled data strings (16 bits: data 1, 2, 3 ... In the figure) in a predetermined period based on this time.

Next, in step S105, the calibration computer 40 has the measurement antenna file 71 and the reference antenna file 72 stored in step S103.
And the measurement target antenna 1 based on the data
Calibration that calibrates fluctuations in beacon radio waves due to atmospheric absorption and differences in radiation intensity for each satellite 60 by obtaining the intensity ratio between the intensity of the radio wave received at 0 and the intensity of the radio wave received at the reference antenna 20. Ask for results. The time change of the radio field intensity after calibration in one satellite 60 is the one-dimensional directivity pattern (here, “one-dimensional”) of the measurement target antenna 10 along the orbit (passage path direction) of one satellite 60. Means that the data is calculated based on only the beacon signal from one satellite 60).

The calibration computer 40 also uses the storage device 70 to store the position data of the satellite 60 ("satellite azimuth", "satellite elevation") contained in the satellite position data file 71 into the antenna 10 to be measured. Corresponding as "azimuth" and "elevation" on the drive axis of the measurement target antenna 1
The calibration result for the azimuth angle and the elevation angle of 0 is stored in the calibration result file 74. Furthermore, the calibration computer 40 repeats the process of obtaining the calibration result file 74 for a large number of non-geostationary satellite orbits, and a plurality of calibration result files 74-k (k =
1 to n) are created.

Here, in FIG. 5, the calibration result file 74-
The explanatory view of k is shown. Calibration result file 74-k (k =
1, 2. ． ． The data format of the data in each sampling of n) includes, for example, "azimuth of the measurement target antenna 10" expressed as floating point data, "elevation angle of the measurement target antenna 10", and "calibration result". .
As the recording format of the calibration result file 74, for example, data indicating the day (8 bits: “day” in the figure), data indicating the hour (8 bits: “hour” in the figure), and minutes Data (8 bits: "minutes" in the figure), data representing seconds (8 bits: "seconds" in the figure), and a data string (16 bits) sampled within a predetermined period based on this time. : In the figure, data 1, 2, 3 ...) are included.

Next, in step S107, the data processing device 50 performs the above-described step S10 for each of the plurality of beacon signals from the plurality of satellites 60 having different orbits.
A plurality of calibration result files 74-k (k = 1, 2 ... N) obtained by repeating steps 1 to S105 are read, and the two-dimensional directivity pattern of the measurement target antenna 10 is acquired. Further, the data processing device 50 stores the obtained two-dimensional directivity pattern in the directivity pattern file 75 corresponding to the elevation angle.

FIG. 6 is an explanatory diagram of the two-dimensional directivity pattern file 75 for each elevation angle. The directivity pattern file 75 stores, for example, the elevation angle of the measurement target antenna 10 and the two-dimensional directivity pattern regarding the reception or transmission radio field intensity (sensitivity) corresponding to this elevation angle. The directivity pattern file 75 for each elevation angle here is, for example,
When the elevation angle is 30 °, 40 °, and 50 °, the two-dimensional directivity patterns are A, B, and C, respectively. Note that steps S101 and S103 are real-time processing because time information when the beacon signal from the satellite 60 is received is required,
On the other hand, steps S105 and S107 may be off-line processing, or all steps may be processed in real time. B-2. Detailed processing of the calibration computer 40 (about S105)

Here, the calibration process in the calibration computer 40 will be mainly described in detail. FIG. 7 shows the calibration computer 4.
It is explanatory drawing which shows the calibration process of 0. First, the calibration computer 40 respectively reads the data strings relating to the radio field intensity sampled during a predetermined period based on a predetermined time from the measurement antenna file 71 and the reference antenna file 72 in the storage device 70 (S201, S203). Here, the time-series digital data read according to the recording formats (see FIG. 4) of the measurement antenna file 71 and the reference antenna file 72 read by steps S201 and S203 and created by the first receiver 15 and the second receiver 25 are: When the horizontal axis represents time and the vertical axis represents frequency amplitude, the state as shown in the graph 42 is stored.

Next, in the calibration computer 40, for example, the unmodulated radio waves (beacon signals) emitted by the satellite 60, which is a non-stationary communication satellite, are concentrated in a very narrow frequency. The time-series digital data stored in the measurement antenna file 71 and the reference antenna file 72 indicated by 42 are converted into frequency spectrum data by, for example, fast Fourier transform (S).
205, S207). Here, steps S205 and S2
The frequency spectrum data calculated in 07 is in the state shown in the graph 44 when the horizontal axis is the frequency, the vertical axis is the intensity of the received radio wave, and when the time axis is used.

Further, the calibration computer 40 captures the value of the sharp peak appearing on the graph 44 as the intensity of the received radio wave,
Calibration is performed using this value. Specifically, the peak value of the spectrum obtained from the data of the measurement antenna file 10 is Vm, the base (radio field intensity at a frequency other than the beacon) is Vbm, while the peak obtained from the data of the reference antenna file 20. The value is Vr and its base (radio field strength at frequencies other than beacon) is Vbr
As these values (Vm, Vbm, Vr, Vbr)
Is detected from the graph 44 (S209, S211).

Next, the calibration computer 40 executes step S
209, using these values detected from S211, the calibration result Vc which is the data after calibration is calculated by the mathematical expression (1). Vc = (Vm-Vbm) / (Vr-Vbr) (1) Further, the calibration computer 40 is a satellite that records position data ("satellite azimuth angle""satellite elevation angle") of the satellite 60 for each time. The position data 73 file is read, and this position data is associated with the "azimuth angle of the measurement target antenna 10" and the "elevation angle of the measurement target antenna 10" on the drive axis of the measurement target antenna 10. The calibration computer 40 responds to the calculated “azimuth angle of the measurement target antenna 10” and “elevation angle of the measurement target antenna 10” with the “calibration result V”.
"c" is stored in the calibration result file 74 (S213).
Note that steps S201 to 211 are repeated a number of times corresponding to the integration time unit, and steps S201 to 213 are repeated.
Is repeated during the measurement time.

Here, step S1 of the calibration computer 40.
The time synchronization method in the calibration processing in 05 will be described. Time information written at the beginning of the measurement antenna file 71 and the reference antenna file 72 (1 bit of 1 pp
s sync signal bit: “A” in FIG. 4 is ± 0.
There may be an error of about 5 seconds. In the directional pattern measurement system 100 according to the present invention, it is necessary that the data collected by the measurement target antenna 10 and the data collected by the reference antenna 20 have the same time in milliseconds. Therefore, time synchronization is performed using the 1 pps synchronization signal recorded in the most significant bit of each data. This 1 pps synchronization signal is, for example, O in synchronization with the start of 1 second.
It becomes N (= "1"), and it turns off after 25 milliseconds.
It is a pulse signal that repeats the operation of (= “0”).
Therefore, by detecting the moment when the pulse signal is turned on from the data of the two files and executing the process from the data immediately after that, a high degree of coincidence at time is obtained. Also,
The place to detect the processing start position on the two files is
It is necessary to agree within ± 0.5 seconds in advance.
The 1 pps synchronization signal can be obtained from, for example, an inexpensive GPS receiver.

B-3. Detailed Processing of Data Processing Device 50 (Regarding Step S107) FIG. 8 is a flowchart showing a two-dimensional directivity pattern calculation in the data processing device 50. Data processor 50
First, a plurality of calibration result files 74-k (k = 1 to n) created based on a plurality of beacon signals in the measurement target antenna 10 at a fixed elevation angle are read (S301). Next, the data processing device 50 sets data on the calibration radio field intensity on the two-dimensional coordinate represented by the position angle (elevation angle, azimuth angle) in the antenna based on the plurality of 1 to n in step S301 ( Plot) (S
303). In addition, the data processing device 50, step S3
Interpolation processing is performed on the data setting obtained in 01 (S
305) Further, the two-dimensional directivity pattern is displayed and stored in the directivity pattern file 75 storing the two-dimensional directivity pattern for each elevation angle (S307). Further, the data processing device 50 changes the elevation angle of the measurement target antenna 10 and repeats steps S301 to 307 to repeatedly measure the two-dimensional directivity pattern indicating the sensitivity or the directivity of the antenna, and for each elevation angle. Directivity pattern file 7 storing a two-dimensional directivity pattern
5 is created (S309). Thereby, according to the directivity pattern measurement system 100, the elevation angle dependence of the directivity pattern of the antenna can be measured.

(Regarding Steps S301 and S303)
Here, FIG. 9 is an explanatory diagram showing the relationship between the celestial sphere coordinate system and the visual field coordinate system. FIG. 9A shows a celestial sphere coordinate system, and shows a state of looking up at the sky from the position of the measurement target antenna 10 (this is referred to as a celestial sphere coordinate system). Here, the outermost circle is the horizon, the middle of the circle is the zenith, the upper side of the circle is north, and the right side is east. In addition, the orbits of the satellites (two types here) are indicated by arrows extending from the south horizon to the north horizon in the figure. Further, in the drawing, a donut-shaped region indicated by hatching is a field of view (with respect to the center of the field of view) of the measurement target antenna 10 when the measurement target antenna 10 is rotated around the azimuth axis at a constant elevation angle. It is a region showing the range until the sensitivity becomes half).

The small white circle in the region showing the field of view of the measurement target antenna 10 represents the width of the field of view of the measurement target antenna 10 when the azimuth angle is further fixed.
Therefore, in order for the field of view of the measurement target antenna 10 to enter the orbit of the satellite 60, the orbit of the satellite 60 is predicted in advance, and the measurement target antenna 10 is rotated around the azimuth axis with a constant elevation angle. It is necessary to move the field of view of the measurement target antenna 10 within a donut-shaped region in the figure.

On the other hand, FIG. 9B shows a visual field coordinate system, and the visual field of the antenna 10 to be measured has an axis parallel to the elevation direction (in the figure, an axis extending from the horizon to the zenith) and an azimuth. It can be expressed by two coordinate axes (two-dimensional coordinate system) with an axis parallel to the angular direction (circumferential direction of a large circle showing the horizon in the figure) (this is called the view coordinate system: beam coordinate). ). Here, as an example, the center of the drawing indicates the center of the field of view, the inner circle indicates the position where the sensitivity is half the center of the field of view, and the outer circle indicates the position where the sensitivity becomes 1/10. Further, the upper direction in the figure indicates the zenith direction, and the lateral direction indicates the axial direction parallel to the azimuth angle. Specifically, the visual field coordinate system here indicates orbits of a plurality of satellites 60 passing through the visual field of the measurement target antenna 10 when the elevation angle of the measurement target antenna 10 is 30 degrees (however, , As an example, the antenna aperture is 10 m, the reception frequency is 6.8 GHz, and the measurement time is 1 hour).

Here, when the shape of the mirror surface of the antenna 10 to be measured is deformed by gravity, the sensitivity is half or 1/1.
The curve connecting the positions of 0 does not become a circle but becomes an ellipse, or has a more irregular shape (here, this curve is a circle and the shape of the mirror surface of the antenna 10 to be measured is not deformed). It is supposed to be). In the directional pattern measurement system 100, by measuring the unevenness, the deformation of the two-dimensional directional pattern (that is, the unevenness) due to the deformation of the mirror surface shape of the measurement target antenna 10 according to the elevation angle. It is calculated.

When the antenna 10 to be measured has a constant elevation angle and only the respective azimuth axes are rotated so that the field of view of the antenna 10 to be measured is directed to the orbit of the satellite 60, the satellite 60 on the field of view coordinate system is displayed. In the figure, small circles are connected to show what kind of movement is made. This indicates that the satellite 60 is linearly crossing the view coordinate system at various angles. In addition, satellite 60
The direction in which the satellite crosses depends on the movement of the satellite 60 on the celestial spherical coordinates of the satellite 60 and the antenna 20 to be measured.
Is determined by the elevation angle of. Further, when there are a plurality of satellites 60, each satellite 60 takes various orbits on the celestial spherical coordinates, and as a result, the satellites cross at various angles on the visual field coordinates.

(Steps S303, S305, S307
First, the data processing device 50 uses the field-of-view coordinate system (see FIG. 9B) to measure the antenna 10 to be measured.
The two-dimensional directivity pattern is obtained from the intensity change of the beacon signal of the satellite 60 passing through the field of view. As a method of obtaining the two-dimensional directivity pattern, for example, a method substantially similar to the CT scan imaging and image processing methods used in medical diagnosis can be used. For example, the two-dimensional directivity pattern is obtained by calculating the interpolated contour lines of the radio field intensity based on the obtained calibration result data of the plurality of calibration result files 74-k.

FIG. 10 is an explanatory diagram of the calculation of the two-dimensional directivity pattern by the data processing device 50. Figure 1
At 0 (a), the satellite 6 is in the field of view of the antenna 10 to be measured.
A change in the intensity of the beacon signal (here, a change curve 63 corresponding to the track 61 and a change curve 64 corresponding to the track 62) when the 0 track (here, the tracks 61 and 62) is crossed is shown. There is. These change curves 63, 64
The horizontal axis indicates the beacon of the satellite 60, which is the measurement target antenna 10.
Elapsed time from the time when reception is started by (satellite 60 from the beacon reception start time of satellite 60
Is proportional to the movement angle of the field), and the vertical axis is the radio field intensity ratio with the center of the field of view as a reference. This allows
The change curves 63 and 64 of the received radio wave intensity form a one-dimensional directivity pattern along the trajectory of the satellite 60 (orbits 61 and 62).

Further, in the data processing device 50, if another satellite 60 is used, the data processing device 50 crosses the field of view at a different angle. Therefore, the creation of the one-dimensional directivity pattern along the trajectory of the satellite 60 is repeated. As a result, a large number of radial loci are drawn in the field of view of the measurement target antenna 10, and a large number of unidirectional patterns along the loci of the different satellites 60 are calculated. In addition, the data processing device 50 performs so-called interpolation calculation using the data of the place where the locus passes through for the portion where the locus does not pass, thereby the two-dimensional measurement target antenna 10 at a fixed elevation angle. Is calculated.

FIG. 10B is a diagram showing a two-dimensional directivity pattern of the measurement target antenna 10 at a certain elevation angle. This directivity pattern 65 is measured by the antenna 10 to be measured.
Is a three-dimensional representation of the two-dimensional angle of departure from the center of the field of view and the radio field intensity at that position. That is, here
As an example, regarding the two-dimensional directivity pattern obtained by using the interpolation process, the radio wave intensity with respect to the elevation angle at or near the center of the measurement target antenna 10 is shown. This directional pattern 65 is, for example, steps S301 to S307.
It is a composite of a large number of unitary directional patterns along different trajectories of a plurality of satellites 60 calculated by

(Regarding Step S309) The data processing device 50 sets the two-dimensional directivity pattern 65 created in steps S301 to S307 to the antenna 1 to be measured.
By repeating while changing the elevation angle of 0, how the two-dimensional directional pattern changes with respect to the elevation angle,
The change state of the two-dimensional directivity pattern with respect to the elevation angle is stored in the directivity pattern file 75 in the storage device 70.

C. Detailed Description of Calibration Next, “the strength of the radio wave received by the measurement target antenna 10 and the reference antenna 2 arranged near the measurement target antenna 10 in steps S201 to 213 described above.
By deriving the ratio to the intensity of the radio wave received at 0 (see the above formula (1)), it is possible to calibrate fluctuations in beacon radio waves due to atmospheric absorption and differences in radiant intensity between satellites. To explain. First, the strength of the radio wave received by the measurement target antenna 10 is
In addition to the change in the directivity pattern of No. 3, the change may be caused by "absorption of radio waves by the atmosphere", "change in distance between the satellite 60 and the measurement target antenna 10", "difference in radiated radio wave intensity for each satellite 60", and the like. Therefore, it is necessary to remove changes in the radio field intensity other than the directivity patterns of these antennas with the data received by the reference antenna 20.

Generally, a radio wave (here, a beacon signal)
Passes through the earth's atmosphere and reaches the antenna. It is known that the atmosphere causes some absorption of radio waves, and in particular, water vapor and water droplets (raindrops) in the atmosphere are radio waves used for measurement (for example, microwave: frequency 100).
It causes strong absorption for 0 to 3000 MHz). Here, the water vapor and water droplets are unevenly distributed in the atmosphere. Therefore, when viewing a satellite from the antenna,
The satellite will move on the other side of the unevenness of this distribution, and the radio field intensity reaching the antenna will fluctuate. This fluctuation is irrelevant to the intensity change due to the directivity pattern of the antenna (measurement target antenna 10) to be measured, and thus needs to be removed.

Therefore, the reference antenna 20, which is a small antenna, is arranged in the vicinity of the measurement target antenna 10 (specifically, a distance smaller than the unevenness of the atmosphere), and the beacon signal of the same satellite 60 as the measurement target antenna 10 is transmitted. To receive. At this time, since the reference antenna 20 constantly tracks the satellite 60, the data of the reference antenna file 72 recorded by the reference antenna 20 does not include a change in intensity due to the directivity pattern in principle. When the intensity of the radio waves received by the two antennas changes in a correlated manner, it is determined that the change is not due to the directivity pattern of the measurement target antenna 10 but due to atmospheric absorption (that is, the measurement target antenna 10 and The directivity pattern with the reference antenna 20 is unlikely to be correlated because the antenna diameters are different).

Here, when there is atmospheric absorption, the data output from the reference antenna 20 which is a small antenna (radio wave intensity of the beacon signal) changes according to the amount absorbed by the atmosphere. When the measurement target antenna 10 and the measurement target antenna 20 are installed close to each other, the variation due to atmospheric absorption in the reference antenna 20 and the variation due to atmospheric absorption in the measurement target antenna 10 maintain a proportional relationship. Therefore, by dividing the radio wave reception intensity (Vm-Vbm) of the measurement target antenna 10 by the radio wave reception intensity (Vr-Vbr) of the reference antenna 20, it is possible to remove the fluctuation due to atmospheric absorption, and " Calibration for "radio wave absorption" can be performed.

In addition, "Satellite 60 and measurement target antenna 10
The change in the distance between the two will be described. If the data (radio wave intensity of the beacon signal) output from the reference antenna 20, which is a small antenna controlled to constantly track the satellite 60, is not absorbed in the atmosphere. It is assumed that it takes a substantially constant value, but in reality, the distance between the reference antenna 20 and the satellite 60 changes with time even without absorption, so the time when the satellite 60 re-approaches the reference antenna 20 is regarded as a peak. It shows a gradual increase / decrease characteristic. Also in this calibration of the increase / decrease characteristic, since the output of the reference antenna 20 and the output of the measurement target antenna 10 have a proportional relationship, the “satellite 60 and It is possible to calibrate the “change in the distance between the measurement target antennas 10”.

The "difference in radiated radio wave intensity for each satellite 60" will be described. Since non-stationary communication satellites are moving in the sky, there are a large number of communication points to ensure communication with the ground at all times. Must be placed in orbit and at least one satellite must be visible from the ground.
Further, the directional pattern measurement system 10 according to the present invention
At 0, for example, beacon signals are received from a plurality of satellites 60 having different orbits one after another, and the directivity pattern is calculated. Here, the intensity of the radio wave is different for each satellite 60, but when calculating the two-dimensional directivity pattern,
All satellites need to be calibrated to have the same intensity. Also in the calibration here, since the output of the reference antenna 20 and the output of the measurement target antenna 10 have a proportional relationship, the same processing as "absorption of radio waves by the atmosphere" is performed for "each satellite 60". It is possible to calibrate "difference in radiated field intensity".

Here, the above-mentioned "absorption of radio waves by the atmosphere"
"Change in distance between satellite 60 and antenna 10 to be measured"
The calibration of "difference in radiated radio wave intensity for each satellite 60" is performed by the radio wave reception intensity (Vr-Vb) of the reference antenna 20.
r) the radio wave reception intensity (Vm-V) of the measurement target antenna 10.
What is possible by dividing bm) will be described with a simple mathematical expression. Radio wave intensity Ar (t) of beacon signal received by reference antenna 20 = (Vr-Vbr), radio wave intensity Am (t) of beacon signal received by measurement target antenna 10 =
(Vm-Vbm), both antennas are satellite 60
, The output of the two is Am (t) = k · Ar (t) (2). However, k is a proportional constant.

Further, the absorption ratio in the presence of atmospheric absorption is α (t), the radio wave intensity of the beacon signal of the reference antenna 20 in the presence of absorption is Ar ′ (t), and similarly, the measurement is performed when there is absorption. If the radio field intensity of the beacon signal received by the target antenna 10 is Am ′ (t), then Ar ′ (t) = α (t) · Ar (t), Am ′ (t) = α (t) · Am (t ) (3) holds. Here, t is time and α changes with the movement of the satellite 60. Therefore, Am = Am ′ (t) / α (t) = Am ′ (t) / {Ar ′ (t) / Ar (t )} (4) holds. As a result, the original value Am (t) = (Vm
-Vbm) can be restored. Further, the radio wave intensity A of the beacon signal of the reference antenna 20 when there is no atmospheric absorption
Even if r (t) is not specified, the directional pattern measurement system 100 according to the present invention only needs to correct the amount of change in the absorption amount. Based on the radio wave intensity Ar ′ (0) = α0 · Ar of the beacon signal of the antenna 20, Am ′ (t) / {Ar ′ (t) / Ar ′ (0)} = {Am ′ (t) / α ( t)} / α0 = constant value (5) Further, since the measurement target antenna 10 is waiting for the satellite 60 when measuring the directivity pattern, if the directivity pattern of the antenna is P (t), P (t) will be applied to Am (t) and Am ' It can be expressed as (t) = α (t) · P (t) · Am (t) (6).

From the above, in order to remove the fluctuation due to atmospheric absorption, Am '(t) / {Ar' (t) / Ar '(0)} = {Am' (t) / α (t)}. It may be P (t) / α 0 (7). Also, Am ′ (t) / α (t) and A
Since r ′ (t) is an amount that does not change with time, P (t) = Const. The directivity pattern P (t) is calculated as × [Am ′ (t) / Ar ′ (t)] (8). In this calculation method, the absolute value of the directivity pattern is not fixed, but the directivity pattern is, for example, a quantity normalized with the center of the field of view of the antenna as 1, and even if the absolute value is not fixed, it is substantially determined. There is no inconvenience.

D. Summary As described above, according to the directional pattern measurement system 100 of the present embodiment, the measurement target antenna (large antenna)
In the case of 2, the deformation of the two-dimensional directivity pattern is calculated along with the deformation of the mirror surface shape due to the change of the elevation angle. Demand for large-diameter high-performance antennas is expected to increase with the expected increase in deep space communications such as interplanetary data transmission in the future. In addition, demand for non-stationary communication satellites is expected to increase in the future through data communication using communication satellites, the Internet, etc., and beacon radio waves are expected to shift to higher frequencies. Thereby, the above-mentioned directional pattern measurement system 100 can
It is expected that it can be implemented with high accuracy.

As an application of the present invention, for example, in order to grasp the state of the deformation of the mirror surface shape (deviation from the ideal hyperbolic shape), the directivity pattern corresponding to the deformation of the mirror surface shape is calculated in advance. The file is stored in an appropriate memory in the directional pattern measurement system 100, the directional pattern included in the data file is compared with the actually measured directional pattern, and a mirror surface when the two match. The shape deformation may be read from the data file. Also, by combining the antenna to be measured and a small antenna to construct a radio interferometer, for example,
It can be expected to grasp the state of deformation of the mirror surface shape by using a so-called radio holography method.

[0056]

As described above, according to the present invention, by fixing the elevation angle of the antenna to be measured and using the beacon signals from a plurality of non-geostationary satellites, it is possible to accurately measure the antenna of the antenna to be measured at a certain elevation angle. It is possible to measure a two-dimensional directivity pattern (for example, radio wave intensity for each elevation angle, sensitivity pattern). Further, the present invention can accurately and inexpensively evaluate the performance of a large antenna in a short time.

Further, according to the present invention, it is possible to measure a strict directional pattern which does not theoretically involve movement in the elevation angle direction, which influences the gravitational deformation of the mirror surface of the antenna. Further, the present invention provides a measurement target antenna (large antenna),
It is possible to measure the deformation of the two-dimensional directional pattern associated with the deformation of the mirror surface shape due to the change in the elevation angle.

[Brief description of drawings]

FIG. 1 is a directional pattern measurement system 1 according to the present invention.
00 is a schematic configuration diagram of 00.

FIG. 2 is a directional pattern measurement system 1 according to the present invention.
00 flowchart.

FIG. 3 is an explanatory diagram of a satellite position data file 73.

FIG. 4 is an explanatory diagram of a measurement antenna file 71 and a reference antenna file 72.

FIG. 5 is an explanatory diagram of a calibration result file 74-k.

FIG. 6 is a two-dimensional directional pattern file 75 for each elevation angle.
Explanatory drawing of.

FIG. 7 is an explanatory diagram showing a calibration process of the calibration computer 40.

FIG. 8 is a flowchart showing two-dimensional directivity pattern calculation in the data processing device 50.

FIG. 9 is an explanatory diagram showing the relationship between the celestial sphere coordinate system and the visual field coordinate system.

FIG. 10 is an explanatory diagram of calculation of a two-dimensional directivity pattern by the data processing device 50.

[Explanation of symbols]

10 Target antenna 15 First receiver 20 Reference antenna 25 Second receiver 30 orbit prediction calculator 40 Calibration Calculator 50 data processor 60 satellites 70 storage device 71 Measurement antenna file 72 Reference antenna file 73 Satellite Position Data File 74 Calibration result file 75 Directivity pattern file 100 Directional pattern measurement system

Claims (8)

(57) [Claims] 1. An elevation angle is set to a predetermined angle, a first antenna for receiving radio waves radiated from a plurality of satellites, and a radio field intensity received by the first antenna are converted into first data, and each time is changed. A first data string including a plurality of the first data sampled a plurality of times based on the time.
A first receiver for storing in a file, a second antenna arranged in the vicinity of the first antenna for receiving the radio wave, and a radio field intensity received by the second antenna are converted into second data, A second data string including a plurality of the second data sampled for each time is used as a second
A second receiver stored in a file; a satellite position data file in which the elevation angle and azimuth angle of the satellite indicating the position of the satellite at each time are stored; and the first and second at a certain time from the first and second files. The data is read, the intensity ratio between the first data and the second data is obtained, the calibration radio wave intensity by the first antenna is calculated, and further, the elevation angle and azimuth angle of the satellite are read from the satellite position data file, By associating with the elevation angle and azimuth angle of the first antenna, the calibration radio field intensity,
A calibration computer that creates a plurality of calibration result files that include the elevation angle and the azimuth angle of the first antenna, and reads the elevation angle and the azimuth angle of the first antenna and the calibration radio field intensity from the plurality of calibration result files. A directivity pattern measurement system, comprising: a data processing device that calculates a two-dimensional directivity pattern of an antenna and creates a directivity pattern file including a two-dimensional directivity pattern at a predetermined elevation angle of the first antenna. 2. An elevation angle of the first antenna is changed to another angle, and a directional pattern file including a two-dimensional directional pattern of radio field intensity corresponding to the other angle is created. Item 3. The directional pattern measurement system according to Item 1. 3. The calibration computer converts each of the first and second data into frequency spectrum data by Fourier transform, and subtracts a base value from a peak value of the frequency spectrum data to obtain the first and second data. The directivity according to claim 1 or 2, wherein the radio field intensity of two antennas is obtained, and the calibration radio field intensity of the first antenna is obtained by dividing the radio field intensity of the first antenna by the radio field intensity of the second antenna. Pattern measurement system. 4. The data processing device reads the plurality of calibration result files, sets the calibration radio field intensity data on two-dimensional coordinates of the elevation angle and the azimuth angle of the first antenna, and sets the data. The two-dimensional coordinate data according to any one of claims 1 to 3, wherein interpolation processing is performed on a region where the satellite trajectory does not pass and data is not obtained, and a two-dimensional directivity pattern connecting positions of equal radio field intensity is created. The directional pattern measurement system according to any one. 5. A first stored in the first and second files.
And the second data includes reception time information when the radio wave from the satellite is received, and synchronization signal information for synchronizing the start timing of each process based on the reception time information. 4. The directional pattern measurement system according to any one of 4 to 4. 6. The satellite according to claim 1, wherein the satellite is a non-geostationary satellite that orbits the earth at a low altitude or a middle altitude, and the radio wave is a beacon signal. The described directional pattern measurement system. 7. The elevation angle is set to a predetermined angle, the radio field intensity received by a first antenna for receiving radio waves emitted from a plurality of satellites is converted into first data, and the time is used as a reference for each time. Storing a first data string including a plurality of the plurality of sampled first data in a first file, and a radio wave intensity received by a second antenna arranged near the first antenna for receiving the radio wave To a second file and storing a second data string including a plurality of the second data sampled for each time at a time in a second file, and a certain time from the first and second files. Of the first and second data, the intensity ratio of the first data and the second data is obtained, the calibration radio wave intensity by the first antenna is calculated, and the time of each of the satellites is calculated. The elevation and azimuth of the satellite are read from the satellite position data file that stores the elevation and azimuth of the satellite, and the calibration radio field intensity is associated with the elevation and azimuth of the first antenna. Creating a plurality of calibration result files including the elevation angle and the azimuth angle of the first antenna; reading the elevation angle and the azimuth angle of the first antenna from the plurality of calibration result files; Calculating a two-dimensional directivity pattern and creating a directivity pattern file including a two-dimensional directivity pattern at a predetermined elevation angle of the first antenna. 8. Further, the elevation angle of the first antenna is changed to another angle, and a directional pattern file including a two-dimensional directional pattern of radio field intensity corresponding to the other angle is created. Item 7. The directional pattern measuring method according to Item 7.