JP2003198441A - Satellite tracking antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a satellite tracking antenna in which a receiving level can be kept satisfactory even when a shading object is present. <P>SOLUTION: The satellite tracking antenna is provided with a phased array antenna 21 for receiving radio waves from a satellite, a map database 25 for storing map information and information on a building making a shading object, and an antenna control part 29 for detecting the presence/no presence of the shading object blocking off the radio waves around a present vehicle location from the information on the building acquired from the map database 25, detecting the coming direction of waves reflected on this shielding object when such a shading object blocking off the radio waves is present, and performing control to turn the antenna directivity of the phased array antenna 21 to that direction. Thus, even when the building blocking off the radio waves is present, satisfactory receiving characteristics can be provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite tracking antenna which always directs its antenna directivity toward the satellite so that radio waves from the satellite can be received.

[0002]

2. Description of the Related Art Conventionally, a satellite tracking antenna of this type, as shown in FIG. 6 (a), uses an A / D converter 83 to convert output information from a vehicle azimuth angle sensor such as a magnetic sensor 81 and an optical fiber gyro 82. Then, the digital signal is converted into a digital signal and supplied to the tracking personal computer 84, the azimuth angle of the satellite with respect to the own vehicle is calculated, and the calculated signal is supplied to the antenna control unit 85. The antenna control unit 85 selects the antenna beam number, that is, the combination number of the phase amounts for forming the antenna directivity, based on the received satellite azimuth information, and specifies it to the phase shifter driver 86. The phase shifter driver 86 supplies the phase amount of the designated beam number to the phased array antenna 87, realizes the phase amount in each antenna element, controls the antenna directivity, and controls so as to always face the satellite direction. is doing. In FIG. 6A, LNA is a low noise amplifier, HPA is a high power amplifier,
D / C is a test reception frequency converter, and U / C is a transmission frequency converter.

Further, the phased array antenna 87 is
In FIG. 6C, the individual antenna elements are a,
The antennas are arranged as shown by b and c, and the antenna directivity and the direction of change of the directivity in this case are as illustrated.
Further, the feeding system for each antenna element a, b, c of the phased array antenna 87 is configured as shown in FIG. 6B, and each antenna element is provided with a 3-bit diode phase shifter.

[0004]

In the above-mentioned conventional satellite tracking antenna, the antenna directivity is always oriented in the direction of the satellite and only the radio waves directly coming from the satellite, that is, the direct waves are received. However, if there is a shield that blocks radio waves between the vehicle and the satellite, the signal cannot be received, and especially in an urban area where skyscrapers are lined up, there is a problem that the signal cannot be received for a long time.

The present invention has been made in view of the above,
The purpose is to use a satellite tracking antenna that is configured to receive reflected waves when it is determined that direct waves from satellites cannot be received and that can always receive satellite radio waves without being affected by shields. To provide.

[0006]

In order to achieve the above object, the present invention provides a phased array antenna for receiving radio waves from a satellite, direction detecting means for detecting the direction of the satellite, and detection by the direction detecting means. Directivity control means for controlling the antenna directivity of the phased array antenna in the desired direction, map information storage means for storing building information together with map information, and a building stored in the map information storage means Based on the information, the shield detecting means for detecting whether or not there is a shield for shielding the radio waves from the satellite in the direction of the satellite detected by the direction detecting means, and the shield by the shield detecting means. When detected, reflected wave detection means for detecting the arrival direction of the reflected wave of the radio wave from the satellite,
Switching control means for controlling the polarization rotation direction so as to direct the antenna directivity of the phased array antenna to the arrival direction of the reflected wave detected by the reflected wave detecting means.

In the satellite tracking antenna of the present invention, based on the building information stored together with the map information, whether there is a shield that blocks the radio waves from the satellite in the direction of the satellite detected by the direction detecting means. If there is a shield that blocks the radio wave from the satellite, the direction of arrival of the reflected wave of the radio wave from the satellite is detected, and this reflected wave is directed to the antenna directivity of the phased array antenna. The polarization rotation direction is switched to point the.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a satellite tracking antenna according to an embodiment of the present invention. The satellite tracking antenna shown in the figure is adapted to receive a reflected wave when the radio wave from the satellite is blocked by a structure such as a high-rise building and cannot be received.

The satellite tracking antenna of the embodiment shown in FIG.
Phased array antenna 2 for receiving radio waves from satellites
1. Vehicle position and direction detection device 23 for detecting the position and directional relationship between the vehicle and the satellite, building information for determining whether there is a shield such as a high-rise building between the vehicle and the satellite That is, a map database 25 that stores information such as the height and density of buildings, a radio field intensity sensor 27 for searching the direction of arrival of radio waves, or monitoring the radio reception level, an antenna of the phased array antenna 21. The antenna control unit 29 calculates the amount of phase of each antenna element so that the directivity is in the direction of the satellite, and the phase shifter driver 31 that gives the amount of phase calculated by the antenna control unit 29 to each antenna element.

The individual antenna elements constituting the phased array antenna 21 are capable of receiving both a direct wave, which is a radio wave directly coming from the satellite, and a reflected wave, such as a building (not simultaneous reception). Both left-handed and right-handed circularly polarized waves (when circularly polarized waves are reflected, the directions of rotation of the planes of polarization become opposite) must be able to be received and switched easily. Therefore, the antenna element is of a two-point feeding system as shown in FIG.

This two-point feeding system will be described in more detail with reference to FIG. In the case of an array antenna system element that performs switching, only a direct wave needs to be received, so that a single-point feeding method may be used as shown in FIGS. 3 (b-1) and (b-2). The phase amount of the phaser may be fixed as shown in FIG. 9 (b-3). For example, in FIG. 3B-3, the phase amount of the phase shifter A = 45.
Phase amount of phase shifter B = 180 °, phase amount of phase shifter C =
The phase is fixed at 90 ° and the phase amount of the phase shifter D = 0 °.

However, when the reflected wave is also received, the phase of the reflected radio wave is inverted, so that in the case of circular polarization, the rotation direction of the polarization is inverted (reverse rotation).
The receiving side also needs to support this. Therefore, it is necessary for the receiving antenna to be capable of forming circularly polarized waves in both forward and reverse rotation directions.

As described above, in order to configure circularly polarized waves in both rotation directions by one antenna, as shown in FIG.
As shown in (a-2), in the two-point feeding method, the feeding phase of one point is advanced by 90 ° with respect to the feeding phase of the other,
Alternatively, it is delayed by 90 °, thereby forming a normal polarization and an inverted circular polarization. Therefore, when the phase of the feeding point corresponding to one point is fixed, the phase of the feeding point corresponding to the other point needs to be changed by ± 90 ° (180 °). As shown in a-3), ± 90 ° (18
A phase shifter with a phase change of 0 ° is needed at the other point. That is, of the two feeding points, one point may be a fixed phase shifter, but the other point needs to have a phase shifter having a phase change amount of ± 90 ° (possible with 1 bit). In addition, the timing of phase switching is triggered by the inability to receive direct waves (this is the case when it is estimated that the signal will be blocked for a certain period of time instead of the instantaneous block, and this estimation is performed by the map database). .

Next, the operation will be described with reference to the flow chart shown in FIG.

In FIG. 4, first, the position and direction of the own vehicle is detected by the own vehicle position / direction detecting device 23, and from which result the direction of the satellite is calculated (steps 510 and 520). Then, based on the information of the building stored in the map database 25, it is determined whether or not there is a shield such as a building between the satellite and the own vehicle, by the antenna control unit 29.
(Step 530).

If there is no shield, an antenna beam number which gives a left-handed circularly polarized wave with an antenna directivity toward the satellite direction angle is selected, and the antenna beam number is designated to the phase shifter driver 31 (step 540). ). Phase shifter driver 3
1 has a database of the phase amount of each antenna element arranged by the antenna beam number, and gives the phase amount of the designated antenna beam number to each antenna element (step 550). As a result, the directivity of the antenna is directed toward the satellite.

While the direct wave is being received, it is monitored by the radio field intensity sensor 27 whether or not the reception level of the direct wave is lowered (step 56).
0) If it has not decreased, the process returns to step 510 to repeat the same operation, but if it has decreased, the process proceeds to step 570 to calculate the reflected wave arrival direction.

On the other hand, when there is a shield between the vehicle and the satellite in the determination of step 530, step 57
Proceed to 0 and calculate the arrival direction of the reflected wave. That is, the antenna beam number is selected so that the antenna directivity is right-handed circularly polarized in the direction of arrival of the reflected wave (step 580), and the antenna beam number is designated to the phase shifter driver 31. The phase shifter driver 31 gives the phase amount of the specified antenna beam number to each antenna element (step 5
90), whereby the directivity of the antenna is oriented in the direction of arrival of the reflected wave.

The arrival direction of the reflected wave is determined as follows. First, considering that the satellite radio wave is considered to be a parallel wave because the satellite position is sufficiently far away and that the incident angle and the reflection angle are equal when the radio wave is reflected, the reflected wave arrival elevation angle is equal to the direct wave arrival elevation angle. As for the azimuth angle, if the direct wave arrival direction angle is θ degrees with reference to the vehicle position, the reflected wave arrival azimuth angle is −θ degrees. Therefore, when the direct wave arrival angle is an elevation angle φ degree and an azimuth angle θ degree, the reflected wave arrival angle is an elevation angle φ degree and an azimuth angle −θ degree (see FIG. 5).

Utilizing this property, the directivity is directed in that direction as the first means for receiving satellite radio waves. When the reflected wave reception level is less than the specified value, the second means is searched in the direction in which the reflected wave reception level is large, but the elevation angle at that time is φ degrees. Also, during searching, it always checks whether there is an obstacle between the vehicle position and the satellite by using the vehicle position, direction detection device and map database. The left-hand circularly polarized wave is directed toward the satellite position.

[0022]

As described above, according to the present invention,
Based on the building information stored with the map information,
It is detected whether or not there is a shield that blocks the radio waves from the satellite in the direction of the satellite detected by the direction detecting means, and if there is a shield that blocks the radio waves from the satellite, The direction of polarization of the phased array antenna is switched to detect the arrival direction of the reflected wave of the radio wave, and the direct wave is blocked by the building to receive the wave. Even when it is not possible, the reflected wave is received and the satellite radio wave unrecoverable time can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a satellite tracking antenna according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a feeding system of an antenna element used in the satellite tracking antenna of FIG.

FIG. 3 is an explanatory diagram of an antenna element used in the satellite tracking antenna shown in FIG.

4 is a flowchart showing the operation of the satellite tracking antenna of FIG.

FIG. 5 is an explanatory diagram showing the arrival angles of a direct wave and a reflected wave used to explain the operation of the satellite tracking antenna of FIG. 1.

FIG. 6 is a diagram showing a conventional satellite tracking antenna.

[Explanation of symbols]

21 Phased array antenna 23 Vehicle position and direction detector 25 map database 27 Radio field intensity sensor 29 Antenna control unit 31 Phase shifter driver

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04B 7/26 H04B 7/26 BF term (reference) 5J045 AA11 CA04 DA10 EA07 JA02 NA02 5J070 AA02 AC01 AD10 AF03 5K059 AA12 CC03 CC05 5K067 AA01 BB03 EE02 EE07 KK02 5K072 AA01 AA22 BB13 BB22 DD01 DD11 GG02 GG06

Claims (2)

[Claims] 1. A phased array antenna for receiving radio waves from a satellite, a direction detecting means for detecting the direction of the satellite, and an antenna directivity of the phased array antenna in the direction detected by the direction detecting means. Directivity control means for controlling, map information storage means for storing building information together with map information, and satellite information detected by the direction detection means based on the building information stored in the map information storage means. Shield detection means that detects whether or not there is a shield that blocks the radio waves from the satellite in the direction, and when a shield is detected by the shield detection means, the arrival of the reflected wave of the radio waves from the satellite A reflected wave detecting means for detecting the direction, and a polarization rotation direction for directing the antenna directivity of the phased array antenna to the arrival direction of the reflected wave detected by the reflected wave detecting means. A satellite tracking antenna, comprising: switching control means for controlling switching. 2. The phased array antenna has a plurality of antenna elements, and each antenna element has two feeding points having feeding phases different from each other by 90 degrees, and each has a first phase shifter, And a second phase shifter, wherein the first phase shifter is set to have a different phase amount for each antenna element, and the first phase shifter and the second phase shifter included in one antenna element The phase shifter has a phase amount of 9
The satellite tracking antenna according to claim 1, wherein the satellite tracking antenna is offset by 0 degree.