JP3149156B2 - Microwave antenna device for mounting on moving object - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking-type microwave antenna device mounted on a mobile object typified by a vehicle-mounted satellite broadcast receiving antenna device. Regarding countermeasures in case of change in elevation direction.

[0002]

2. Description of the Related Art A tracking-type microwave antenna device mounted on a mobile body such as an automobile and used for receiving satellite broadcasts has been developed.
Since a radio wave from a broadcasting satellite (geostationary satellite) must be able to be received even when the mobile body is traveling, it is necessary to perform pointing control such that the main beam of the antenna matches the azimuth and elevation of the broadcasting satellite. .

[0003] Therefore, as a prior art, a planar antenna having a main beam set in a direction perpendicular to the antenna surface, and a driving mechanism capable of mechanically rotating the planar antenna in azimuth and elevation directions are provided. An antenna device capable of performing both angle tracking and elevation tracking is known, but this type of antenna device requires that a flat antenna be tilted obliquely with respect to a horizontal plane when receiving satellite broadcasting, and the height of the device is high. Is about 150mm
When mounted on a moving body such as a car, the amount of protrusion from the roof is too large, which not only impairs the aesthetics of the moving body but also causes a large wind pressure during traveling, which leads to deterioration of aerodynamic characteristics and the like. Was. Further, since both azimuth tracking and elevation tracking are performed, complication of the tracking mechanism is unavoidable. Therefore, the manufacturing cost is high and the weight of the apparatus is 5 to 50 kg.
And it is difficult to mount it on a small car.

In order to reduce the size, weight and cost of this type of antenna device, Japanese Patent Laid-Open Publication No.
As in the prior application by the present inventor described in Japanese Patent No. 2824, the antenna device in which the elevation angle of the main beam of the antenna is made to substantially match the direction of the broadcast satellite in advance and only the azimuth is tracked is known. Proposed. That is, in the related art, the tilt angle of the main beam of the flat antenna with respect to the antenna surface is set to the elevation angle of the broadcast satellite in order to receive a radio wave from the broadcast satellite in a state where the flat antenna is installed substantially horizontally on the moving body. The broadcast satellite can be tracked only by rotating and driving the planar antenna only in the azimuth direction.
As a result, the protruding amount of the device from the roof of the moving body is reduced
To the extent that it does not significantly impair the aesthetics of the moving object, minimizes the degradation of aerodynamic characteristics, and requires only a simple azimuth angle tracking mechanism, thus reducing manufacturing costs. There are various merits such as the weight of the device is reduced to about 2 kg, which facilitates mounting on a small car.

[0005]

However, in the above-mentioned conventional antenna device which is advantageous for reduction in size and weight and cost, the main beam of the planar antenna is moved from the satellite direction when the moving body is traveling on a slope. There is a problem that the receiving sensitivity is easily degraded due to deviation. The elevation angle of the broadcast satellite differs by about 20 degrees in Japan depending on the receiving area, but the beam width of the main beam of the planar antenna in the elevation direction is about 10 degrees.
Therefore, it is not possible to receive satellite broadcasts anywhere in Japan where a mobile body equipped with such a conventional antenna device is installed.For example, in East Japan and West Japan, the tilt angle of the main beam with respect to the antenna surface is different. An antenna device must be used, and there is a problem that versatility is lacking.

The present invention has been made in view of the above-mentioned deficiencies of the prior art, and has as its object to be advantageous in reducing the size and weight and cost and to obtain good reception sensitivity even when traveling on a slope. Further, it is an object of the present invention to provide a mobile-mounted microwave antenna device which can be used in a wide area and has high versatility.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pair of planar antennas which are installed substantially horizontally on a movable body with the azimuths of respective main beams matched, and a pair of planar antennas. Rotation driving means for rotating the antennas in an azimuth direction in synchronization with each other, wherein the main beam of one of the planar antennas is inclined with respect to the antenna surface by a first inclination angle (for example, an angle slightly larger than the elevation angle of a broadcasting satellite). ) And the main beam of the other planar antenna is set to a second tilt angle (for example, an angle slightly smaller than the elevation angle of the broadcast satellite) with respect to the antenna surface different from the first tilt angle. Achieved by: And an antenna changeover switch for selecting one of the pair of planar antennas and connecting to the receiving circuit, and when the strength of the received signal of the one planar antenna connected to the receiving circuit is smaller than a predetermined value. Control means for selecting the other planar antenna for the antenna changeover switch and outputting an automatic changeover signal for connecting to the receiving circuit, wherein the planar antenna connected by the antenna changeover switch is connected to the automatic changeover signal. It is preferable to adopt a configuration selected in accordance with the following.

[0008]

As described above, if a pair of planar antennas having different inclination angles of the main beam with respect to the antenna plane are rotated in the azimuth direction in synchronization with each other, the deviation of the elevation angle of the main beam with respect to the satellite direction is reduced. Since the smaller planar antenna can be connected as appropriate, even if the relative position of the broadcast satellite changes in the elevation direction, for example, when the moving object moves significantly north and south or approaches a slope, by switching the connected planar antenna Good receiving sensitivity can always be obtained. Furthermore, since the pair of planar antennas are rotated synchronously in the azimuth direction, there is no need to separately provide a drive motor and a rotation control mechanism. Therefore, it is possible to avoid the complexity of the tracking mechanism and to reduce the size, weight, and cost. This is advantageous.

Further, as described above, if a configuration is adopted in which the planar antenna connected by the antenna changeover switch is selected according to the automatic changeover signal, a manual antenna changeover operation after confirming the reception sensitivity can be performed. Since it becomes unnecessary, the operability is improved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic plan view of a moving object mounting antenna apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a circuit configuration of the embodiment. In these figures, reference numeral 1 generally indicates an antenna mechanism including an antenna unit 2 and an LNB 3, and the antenna mechanism 1 includes a receiver 4, a reception intensity detection device 5, a control device 6, a motor driver 7, a mode selection device, and the like. The receiving system is configured by being connected to an external device such as the switch 8. The antenna unit 2 includes a pair of planar antennas 20 and 21 and these planar antennas 2 and 21.
A motor (stepping motor) 22 for rotationally driving the motors 0 and 21 in the azimuth direction, a pulley 23 attached to a drive shaft of the motor 22, a plurality of rotation guides 25, The motor driver 7 supplies a signal for controlling the motor 22 to the input terminal 24. Further, the LNB 3 includes low-noise amplifiers 30 and 31.
An electronic switch (antenna changeover switch) 32;
Mixer 33, local oscillator 34, intermediate frequency amplifier 35
, A choke coil 36, a capacitor 37, an intermediate frequency signal (BS-IF signal) output terminal 38, and the like.

Here, the antenna section 2 will be described in detail. Each of the planar antennas 20 and 21 has substantially the same configuration as the antenna disclosed in Japanese Patent Application Laid-Open No. 5-152824 previously proposed by the present inventors. In other words, the circular planar antenna 20 has a plurality of rotation guides 2 that are rotatable around the outer periphery.
5 and a belt 26
The belt 26 is driven by the motor 22 through the pulley 23 to thereby obtain the planar antenna 2.
0 allows forward and reverse rotation in the azimuth direction (circumferential direction). Similarly, also in the circular planar antenna 21, a belt 27 is wound around an outer peripheral portion supported by a rotation guide 25, and the motor 22 moves the planar antenna 21 in the azimuth direction via the belt 27 and the pulley 23. It can rotate forward and backward. As a result, the pair of planar antennas 20 and 21 are rotated by the motor 22 in the azimuthal direction in synchronization with each other. Further, as shown by arrows in FIG. 1, the pair of planar antennas 20 and 21 are installed substantially horizontally on the moving body with the azimuth angles of the respective main beams being matched.

However, the plane antenna 20 and the plane antenna 21 have different inclination angles of the main beam with respect to the antenna surface as shown in FIG. That is, in the case of the present embodiment, the inclination angle θ1 of the main beam of the planar antenna 20 with respect to the antenna surface is set to 42 degrees, and the inclination angle θ2 of the main beam of the planar antenna 21 with respect to the antenna surface is set to 34 degrees. The relationship of θ1> θ2 holds. By the way, since the elevation angle of the broadcasting satellite in Tokyo is 38 degrees, if the mobile body equipped with this antenna device is located in Tokyo or the surrounding area, one planar antenna 2
The inclination angle θ1 of the main beam of 0 is slightly larger than the elevation angle of the broadcast satellite, and the inclination angle θ2 of the main beam of the other planar antenna 21 is slightly smaller than the elevation angle of the broadcast satellite.

As described above, in the present embodiment, the two planar antennas 20 and 21 having different main beam inclination angles with respect to the antenna surface are placed substantially horizontally on the moving body in a state where the azimuth angles of the respective main beams are matched. And the two antennas 20 and 21 are synchronously rotated in the azimuth direction by a single motor 22, so that the pair of planar antennas 20 and 21 move their main beams in a predetermined elevation direction. With the angle (8 degrees) shifted and the azimuth angle of each main beam constantly matched, the rotary drive is performed in the same direction.

Now, the satellite broadcast radio wave of the 12 GHz band received by the planar antenna 20 or the planar antenna 21 is:
The frequency is converted to a BS-IF signal of about 1 GHz band by the LNB 3 and input to the receiver 4. The receiver 4 performs demodulation of video and audio, and supplies a detection output to the reception intensity detection device 5. The reception intensity detector 5 generates a reception intensity signal Va that is a DC voltage proportional to the reception intensity from the detection output. The reception intensity signal Va is supplied to the control device 6, and the control device 6 selects a control method for keeping the intensity of the reception intensity signal Va equal to or higher than the threshold value Vt.
In order to execute this control method, a signal for controlling rotation / stop of the stepping motor 22 is supplied from the control device 6 to the motor driver 7. Thereby, for example, even when the mobile body is turning, the plane antenna receiving the radio wave of the satellite broadcast is appropriately rotated to control the main beam so as to always face the satellite. Can be tracked. As will be described later, when the reception intensity of one planar antenna connected to the receiver 4 and receiving the radio wave of the satellite broadcast is smaller than a predetermined value, the other planar antenna is connected to the receiver 4. Is output from the control device 6 to the mode selection switch 8 so as to cope with a change in the relative position of the broadcast satellite in the elevation angle direction.

Next, the planar antennas 20, 21 and LN
The operation of B3 will be described in more detail. The output of the planar antenna 20 is supplied to the low-noise amplifier 30 and the output of the planar antenna 21 is supplied to the low-noise amplifier 31. Is selected, and the output of the selected 12 GHz band is
3 mixed with the signal from the local oscillator 34, and
It is converted to a BS-IF signal in the Hz band. And this B
The S-IF signal passes through an intermediate frequency amplifier 35,
Is supplied to the receiver 4. In this way, the BS-IF signal is supplied from the LNB 3 to the receiver 4, while the DC for operating the LNB 3 is supplied from the receiver 4 to the electronic switch 3.
2 is supplied. This direct current, whose voltage is E1 or E2, is transmitted through the choke coil 36 to the electronic switch 32.
The electronic switch 32 is switched to the A side in FIG. 2 when the voltage is E1, and when the voltage is E2,
B side. That is, by switching the DC voltage supplied to the electronic switch 32, the planar antenna connected to the receiver 4 is selected as one (the planar antenna 20 or 21). At this time, even if the voltage changes to E1 or E2, only the electronic switch 32 is switched, and the LNB
The operation of the other three components does not change.

By the way, from the receiver 4 to the electronic switch 32
Can be switched at any time by operating a mode selection switch 8 connected to the receiver 4. That is, as shown in FIG. 2, the mode selection switch 8 switches “ANT1” and “ANT1”.
When the switch 8 is set to "ANT1", the voltage E1 is applied to the terminal 38 of the LNB3, and the electronic switch 32 selects the planar antenna 20 (see FIG. 3). First limited mode). Similarly, when the switch 8 is set to “ANT2”,
The voltage E2 is applied to the terminal 38 of the LNB3, and the electronic switch 32 selects the planar antenna 21 (second limited mode). When the switch 8 is set to "auto", the voltage E1 or E2 is output according to the reception state of the radio wave of the satellite broadcast, and the electronic switch 32 automatically switches one of the planar antennas 20 and 21. (Automatic switching mode).

Here, an example of the automatic antenna switching operation when the mode changeover switch 8 is set to "automatic" will be described with reference to the flowchart of FIG. In order to compare and determine the magnitude of the reception intensity signal Va, the control device 6 has two threshold values V as shown in FIG.
t and Vs are set in advance, and among them, the threshold V
t is a voltage at which the signal can be received satisfactorily if the reception intensity is higher than this, and the threshold value Vs is a limit value at which the signal can be received barely.

In FIG. 4, assuming that the electronic switch 32 selects the planar antenna 20 (ANT1) as an initial condition, first, in the reception intensity detection step of step S1, the reception intensity obtained by the planar antenna 20 is determined. The magnitude Va1 of the signal Va is detected. This reception intensity Va
1 is supplied to the control device 6 and compared with the threshold values Vt and Vs in the intensity comparison step of step S2. As a result, if Va1 ≧ Vt, it can be determined that the reception has been performed well, so that the motor 22 is not driven and step S
The process returns to the reception intensity detection process of step S1. If Vs ≦ Va1 <Vt, the reception state is slightly poor, so the motor 22 is driven to rotate the planar antenna 20 in the azimuth direction. And then step S
The process returns to step 1 for detecting the reception intensity.

In step S2, Va1 <Vs
In the case of, the reception state is extremely poor, so that the electronic switch 32 is used instead of the planar antenna 20 selected so far.
Proceeds to the antenna switching step of step S4 in which the user selects the planar antenna 21. Next, in the reception intensity detection step of step S5, the magnitude Va2 of the reception intensity signal Va obtained by the planar antenna 21 is detected, and in the intensity comparison step of step S6, the reception intensity V
a2 is the reception intensity Va1 immediately before performing the antenna switching operation.
Compare with As a result, if Va2> Va1, the process returns to the reception intensity detection step of step S1 with the planar antenna 21 (ANT2) selected, but Va2 ≦ Va1.
In the case of (1), it means that the reception state has been deteriorated by performing the antenna switching operation. Therefore, the process proceeds to the antenna switching step of step S7, and the planar antenna 20 (ANT) is returned again.
After selecting 1), the process returns to the reception intensity detection step of step S1.

Note that, in the antenna switching operation in steps S4 and S7, the control device 6 supplies an automatic switching signal to the mode selection switch 8, and in response to the automatic switching signal, the switch 8 applies the voltage E1 or the voltage E1 to the terminal 38 of the LNB 3. E
2 by applying the switch 8
Is set to "ANT1" or "ANT2", the automatic switching signal is ignored.

Therefore, when the mobile unit travels only in a limited area where the mobile object is almost flat, the mode selection switch 8 is set to "ANT1" (first limited mode) or "ANT1".
2 "(second limited mode), and using only one of the planar antennas 20 or 21 having good reception sensitivity, noise caused by the antenna switching operation can be avoided. .

Also, if the mode selection switch 8 is set to "automatic", the satellite direction can be changed even when the moving object moves largely north and south or approaches a sloping road and the relative position of the broadcasting satellite changes in the elevation direction. , The plane antenna with the smaller deviation of the main beam in the elevation angle direction is automatically selected, so that good reception sensitivity can always be obtained without performing a manual antenna switching operation.

In addition, since the above-described antenna device is configured to rotate the pair of planar antennas 20 and 21 synchronously in the azimuth direction, it is not necessary to provide a drive motor and a rotation control mechanism for each planar antenna 20 and 21. The mechanism can be prevented from becoming complicated, which is advantageous for reduction in size and weight and cost, and does not hinder mounting on a small car. The flat antennas 20 and 21 of this antenna device have almost the same configuration as that described in Japanese Patent Application Laid-Open No. 5-152824 previously proposed by the present inventor. Needless to say.

In this embodiment, the inclination angle of the main beam with respect to the antenna surface is set to 42 for the planar antenna 20.
Since the plane antenna 21 is set to 34 degrees in degrees and the beam width in the elevation direction of the main beam is about 10 degrees, this antenna device is used in a reception area where the elevation angle of the broadcast satellite is 29 degrees to 47 degrees (Japan In Japan, satellite broadcasting can be received in a wide range from central Hokkaido to Kagoshima prefecture).
Also, when using in Tokyo where the elevation angle of the broadcast satellite is 38 degrees,
Since the satellite broadcast can be received even when the mobile body is traveling on a normal slope having an inclination angle of 9 degrees or less, the reception sensitivity can always be kept good by this antenna device.

When the first or second limited mode is selected, the reception can be performed satisfactorily by the planar antenna 20 in a region where the elevation angle of the broadcast satellite is large, and the reception can be satisfactorily performed by the plane antenna 21 in a region where the elevation angle is small. Therefore, when applying to satellite broadcast reception in Japan, the first limited mode may be selected in western Japan, and the second limited mode may be selected in eastern Japan.

In this embodiment, the antenna switching operation is performed when the reception intensity is lower than the threshold value Vs. However, when the reception intensity is higher than Vs but lower than the threshold value Vt, the antenna switching operation is performed. May be configured to be performed. In this case, if the planar antennas are switched during the vertical synchronization period of the video, a planar antenna having a higher reception strength can be selected without disturbing the received video.

In the present embodiment, the planar antennas 20,
Although each of the main beams 21 is set to have a different inclination angle with respect to the antenna surface, it is possible to develop a two-polarization compatible antenna device with a configuration substantially the same as this. For example, when the planar antenna 20 is for right-handed circular polarization and the planar antenna 21 is for left-handed circular polarization, the switch 8 can be used by switching between both circularly polarized waves.

[0029]

As described above, the microwave antenna device for mounting on a moving object according to the present invention can appropriately select a planar antenna that has a small deviation of the main beam from the geostationary satellite in the elevation angle direction. Even if the angle changes in the elevation direction, good or low sensitivity can be maintained by automatically or manually switching the selected planar antenna, so that the reception condition when traveling on a slope is improved and it can be used in a wide range of areas and versatility Has an excellent effect of being increased. In addition, since the pair of planar antennas arranged in this antenna device are rotated in the azimuth direction in synchronization with each other, there is no need to separately provide a drive motor and a rotation control mechanism, and thus it is possible to avoid complication of the tracking mechanism. Therefore, the present invention has an excellent effect that it is advantageous for reduction in size and weight and cost.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a moving object mounting antenna device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of the embodiment.

FIG. 3 is an explanatory diagram showing a tilt angle of a main beam of a pair of planar antennas with respect to an antenna surface in the embodiment.

FIG. 4 is a flowchart for explaining an automatic antenna switching operation in the embodiment.

FIG. 5 is an explanatory diagram showing a threshold value set in the control device and a change over time of the reception intensity in the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Antenna mechanism 2 Antenna part 3 LNB 4 Receiver 5 Reception intensity detection device 6 Control device 8 Mode selection switch 20, 21 Planar antenna 22 Motor (stepping motor) 26, 27 Belt 32 Electronic switch (antenna changeover switch) 38 Intermediate frequency signal Output terminal θ1, θ2 Tilt angle of main beam with respect to antenna surface

Claims (4)

(57) [Claims] 1. A pair of planar antennas installed substantially horizontally on a moving body with the azimuths of respective main beams matched, and the pair of planar antennas are rotated in the azimuth direction in synchronization with each other. Rotation driving means for setting the main beam of one of the planar antennas at a first inclination angle with respect to the antenna surface thereof, and setting the main beam of the other planar antenna at the first inclination angle with respect to the antenna surface. A microwave antenna device for mounting on a moving body, wherein a second tilt angle different from the tilt angle is set. 2. The antenna device according to claim 1, wherein the first inclination angle is set to be larger than the elevation angle of the broadcast satellite, and the first inclination angle is set to be larger than the elevation angle of the broadcast satellite. 2. A microwave antenna device for mounting on a moving body, wherein the inclination angle of 2 is set small. 3. The antenna changeover switch according to claim 1, wherein one of the pair of planar antennas is selected and connected to a receiving circuit, and one of the planar antennas connected to the receiving circuit. When the strength of the reception signal of the antenna is smaller than a predetermined value, the antenna changeover switch includes a control unit that selects the other planar antenna and outputs an automatic changeover signal for connecting to the reception circuit. A microwave antenna device for mounting on a moving object. 4. The automatic switching mode according to claim 3, wherein the planar antenna connected by the antenna switching switch is selected in accordance with the automatic switching signal, and whether the planar antenna is present or not, regardless of the presence or absence of the automatic switching signal. And a mode selection switch for switching between the three modes, the first mode being specified in the first mode and the second mode being specified in the other mode regardless of the presence or absence of the automatic switching signal. A microwave antenna device for mounting on a moving object.