JPH075236A - Antenna directivity error angle detection system - Google Patents

Abstract

PURPOSE:To detect directivity error angle in the direction of the maximum antenna gain relative to the arrival direction of radiowaves quickly with a handy construction. CONSTITUTION:An antenna 1 with known antenna gain pattern and having a non-circular antenna gain contour is connected to a rotary joint 2, turned centered on the axis in the direction of the maximum antenna grain receiving radiowaves with the direction of arrival unknown. The directivity error angle in the direction of the maximum antenna gain to the incoming direction of the radiowaves is determined by an arithmetic section 5 from a corresponding relationship between the receiving level of the incoming radiowave detected by a receiver 3 and the angle of rotation of the antenna indicated with an angle detector 4.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of terrestrial radio communication systems and satellite communication systems that require antenna pointing control. 2. Description of the Related Art In a wireless communication system, particularly in a satellite communication system that communicates with weak radio waves, it is necessary to make the maximum antenna gain direction coincide with the arrival direction of radio waves so that the reception level becomes maximum. If it is difficult to visually identify the direction of the transmitting station because the transmitting station is distant, it is necessary to use the incoming radio wave to determine the pointing error of the antenna with respect to the incoming direction of the radio wave, or to detect the pointing error angle. However, the conventional technologies are roughly classified into a roving method and a monopulse method. The roving method is a method of determining the pointing error of the antenna with respect to the arrival direction of radio waves by scanning the antenna beam by some method.
The step track method and the conical scan method have been put to practical use. The monopulse method is a method of detecting the pointing error angle of the antenna while the antenna beam is fixed, and is divided into a multiple horn method and a higher order mode method. The step track method is a method of determining the pointing error of the antenna from the increase / decrease in the reception level obtained by moving the pointing direction of the antenna stepwise by a small angle at regular time intervals. The conical scan method is a method of determining the pointing error of the antenna by slightly tilting the rotation axis of the antenna with respect to the axis of the maximum antenna gain and rotating the antenna beam conically while receiving incoming radio waves. When the reception level becomes constant due to the rotation of the antenna, the pointing error of the antenna is determined to be zero. The multiple horn method is a method for instantaneously obtaining the pointing error angle of the antenna by comparing the amplitude and phase of the received signal from each horn. Also in the higher-order mode method, the pointing error angle of the antenna is instantly obtained by comparing the amplitude and phase of the higher-order mode wave and the fundamental mode wave generated when the pointing direction of the antenna deviates from the arrival direction of the radio wave. It is a method. Although the step track system has a simple structure, it is impossible to obtain the pointing error angle of the antenna with respect to the direction of the incoming radio wave in this system, so that the pointing control of the antenna is controlled. As a result, there is a drawback that it takes time until the pointing error of the antenna is determined to be zero. The conical scan method has a major drawback that the antenna gain with respect to the arrival direction of radio waves decreases when the antenna is controlled so that the pointing error of the antenna becomes zero. Further, in the multi-horn method and the high-order mode monopulse method, the pointing error angle of the antenna is instantaneously obtained, but there is a drawback that the configuration for finding the pointing error angle becomes complicated. As described above, the conventional technique has a problem that it is difficult to quickly obtain the pointing error angle in the antenna gain maximum direction with respect to the arrival direction of the radio wave with a simple configuration. An object of the present invention is to quickly obtain the pointing error angle of the maximum antenna gain direction with respect to the arrival direction of radio waves with a simple configuration. In the present invention, attention is paid to the shape of the antenna gain contour, and an antenna having a non-circular antenna gain contour is rotated in a simple configuration around the axis in the maximum antenna gain direction. , And means for obtaining a pointing error angle in the antenna gain maximum direction with respect to the arrival direction of the radio wave by rotating the antenna about the axis. When an antenna having a non-circular antenna gain contour is rotated about the axis in the maximum antenna gain direction,
The antenna gain changes depending on the direction of arrival of the radio wave, and the reception level also increases or decreases according to the rotation of the antenna. From the relationship
Two parameters giving the pointing error angle are obtained, and the pointing error angle in the azimuth direction and the elevation direction of the antenna can be obtained by a simple calculation. FIG. 1 shows an essential part of an embodiment according to the present invention, which is a necessary component on the receiving side. 1 is an antenna whose antenna gain pattern is known and has a non-circular antenna gain contour. 2 is a rotary joint for rotating the antenna easily. 3 is a receiver. 4 is an angle detector. 5 is a pointing error angle. Is a calculation unit for.
An antenna is connected to the movable part of the rotary joint, and the antenna can be rotated about the axis in the maximum antenna gain direction. The angle detector is for knowing the rotation angle of the antenna, is attached in contact with the rotating portion of the rotary joint, and the antenna rotation angle θ is obtained as the output of the angle detector. Further, the reception level R of the incoming radio wave is obtained from the receiver. The operation of the present invention will be described in detail below with reference to the drawings. As a non-circular antenna gain contour,
An elliptical antenna gain contour will be described as an example. Figure 2
[Fig. 6] is a diagram when the antenna is directed in the vicinity of the arrival direction of radio waves. The ellipse shown in FIG. 2 is the elliptical antenna gain contour, and the point O is the center of the elliptical antenna gain contour, that is, the antenna gain maximum direction, and is aligned with the rotation axis of the antenna. Therefore, the direction of the rotation axis of the antenna passes through the point O and is perpendicular to the paper surface. The two broken lines are the major axis and the minor axis of the elliptical antenna gain contour, respectively. When the angle between the long axis and the horizontal direction is θ, this θ corresponds to the antenna rotation angle θ shown in FIG. 1 and can be obtained from the angle detector. S is the arrival direction of the radio wave, and the angle difference corresponding to the length of the line segment OS is φs, and the angle formed by the line segment OS and the horizontal direction is θs. By rotating the antenna,
If φs and θs can be obtained, it means that the pointing error angle of the point O with respect to the arrival direction of the radio wave is obtained. When the antenna is rotated by 180 degrees or more about its rotation axis, the antenna gain with respect to the arrival direction S of the radio wave changes according to the antenna rotation angle θ, so that the reception level R is the elliptical antenna gain of the line segment OS. It becomes maximum when it overlaps with the major axis of the contour, and it becomes minimum when it overlaps with the minor axis of the same antenna gain contour, and the reception level R with respect to the antenna rotation angle θ changes roughly as shown in FIG. Next, how to obtain θs and φs from the change of the reception level R in FIG. 3 will be described. Since θs corresponds to θ when the long axis of the elliptical antenna gain contour coincides with the line segment OS in FIG. 2, the antenna rotation angle when the reception level becomes maximum from the change in the reception level in FIG. You can read it, and you can easily find it. Next, how to obtain φs will be described. Figure 4
Is an example of an antenna gain pattern of an antenna having an elliptical antenna gain contour, and is a gain pattern of a major axis plane and a minor axis plane with respect to the angle of departure from point O. Here, the major axis surface and the minor axis surface are surfaces defined by the major axis and the minor axis of the elliptical antenna gain contour shown in FIG. 2 and the maximum antenna gain direction, that is, the antenna rotation axis. In an antenna having an elliptical antenna gain contour, the antenna gain for the same separation angle differs between the major axis surface and the minor axis surface, and the difference in gain between the major axis surface and the minor axis surface gradually increases as the deviation angle increases. Therefore, if the difference in antenna gain between the long-axis surface and the short-axis surface is given, the angle of departure from point O can be uniquely obtained from the antenna gain pattern. Assuming that the direction of arrival of the radio wave is the direction shown by the arrow in FIG. 4, the antenna gain with respect to the direction of arrival of the radio wave will change between points A and B in FIG. 4 by rotating the antenna. As shown in FIG. 3, the reception level R also changes between the maximum point A ′ and the minimum point B ′ of the reception level according to the change in the antenna gain. Therefore, if the antenna gain pattern and the reception level are expressed on the same scale, the length of the line segment AB and the length of the line segment A′B ′ match, and therefore, to obtain φs, the correspondence relation is reversed. You can follow it. From the change of the reception level in FIG. 3, from the point A ′ giving the maximum reception power and the point B ′ giving the minimum reception power to the length of the line segment A′B ′, that is, the length of the line segment AB in FIG. The difference in antenna gain between the corresponding long-axis surface and short-axis surface can be obtained, and φs can be obtained as the angle of departure from point O from the antenna gain pattern. From θs and φs obtained from the change in the reception level and the antenna gain pattern due to the rotation operation of the antenna, the directional error angle of the maximum antenna gain with respect to the arrival direction of the radio wave is the azimuth-elevation (Az-El) mount system. Taking the antenna pointing control mechanism of FIG. 2 as an example, the pointing error angle ΔAz in the azimuth direction and the pointing error angle in the elevation direction) El
Can be roughly calculated by the following equation. [Equation 1] As described above, according to the antenna pointing error angle detection method of the present invention, the pointing error angle in the maximum antenna gain direction with respect to the arrival direction of a radio wave can be quickly obtained with a simple structure. Therefore, quick antenna pointing control can be provided for small wireless communication equipment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a main part according to an embodiment of the present invention. FIG. 2 is an example showing a relationship between an antenna gain contour and a radio wave arrival direction when an antenna having an elliptical antenna gain contour as a non-circular antenna gain contour is directed in the vicinity of the radio wave arrival direction. FIG. 3 is an example of a change pattern of a reception level when an antenna is rotated. FIG. 4 is an example of an antenna gain pattern. [Explanation of Codes] R Reception Level θ Antenna Rotation Angle 1 Antenna 2 Rotary Joint 3 Receiver 4 Angle Detector 5 Operation Unit

Claims (1)

What is claimed is: 1. A receiving side that receives an unknown radio wave in the arrival direction uses an antenna having a non-circular antenna gain contour and rotatable about the axis in the maximum antenna gain direction to transmit the radio wave. The pointing error angle of the antenna gain maximum direction with respect to the arrival direction of the radio wave is obtained from the correspondence relationship between the antenna rotation angle and the change pattern of the reception level obtained by rotating the antenna about the axis during reception. Antenna pointing error angle detection method.