JP5102403B1 - Radar test equipment - Google Patents

Abstract

When a radar device to be calibrated is mounted on a moving body and is moving, it is difficult to install a calibration target in a direction in which an antenna beam is directed. Since the position of the calibration target deviates from the beam direction, the accuracy of beam directivity adjustment and absolute calibration of the radar decreases. As the moving object, an artificial satellite in orbit and a running car are assumed.
By installing two or more radar test apparatuses, it is possible to measure a beam pointing error and perform absolute calibration of a radar even when a mounted moving body is moving.
[Selection] Figure 1

Description

  The present invention relates to a radar test apparatus used for absolute calibration of a radar mounted on a moving body such as an automobile, an aircraft, and an artificial satellite.

  In recent years, a radar mounted on a moving body such as an automobile uses an antenna device using an active phased array including a large number of antenna elements. This antenna device can obtain arbitrary directivity as a whole by electrically controlling individual modules. The directivity of the array antenna is controlled by adjusting the amplitude and phase with an amplitude adjuster and a variable phase shifter attached to each antenna.

In an array antenna, the amplitude characteristics and phase characteristics of each antenna element deviate from intended values due to variations in circuit characteristics corresponding to each antenna element, variations in element arrangement, and the like, resulting in errors in antenna beam directivity. For this reason, conventionally, a calibration target is installed in the direction in which the antenna beam is directed, and a correction value is added to the amplitude / phase characteristics of the antenna element to adjust the beam directivity.

In the beam center direction, the antenna pattern changes slowly, and when the radar device to be calibrated is stationary, it is easy to install the calibration target in the beam center direction. Radar calibration is possible. A method of using the null point of the antenna pattern for the purpose of adjusting the beam directivity
There is also.

  However, when the radar device to be calibrated is mounted on the moving body and is moving, it is difficult to place the calibration target in the direction of the center of the antenna beam or the null point of the antenna pattern. When the position of the calibration target is shifted from the center of the beam, the accuracy of the beam directivity adjustment and the absolute calibration of the radar is lowered. As the moving object, an artificial satellite in orbit and a running car are assumed.

  In order to solve the above problems, the first invention uses two or more radar test apparatuses having a transmission / reception function as calibration targets, measures a beam pointing error, and corresponds to an installation position of the radar test apparatus. After calculating the weighting of the radar, absolute calibration of the radar is performed.

The second invention is designed so that the radio wave transmitted from the radar test apparatus does not overlap with the received power from other targets at the reception time of the receiver of the radar apparatus to be calibrated. The reception power value can be measured, the directivity error of the reception beam of the radar device to be calibrated, and the absolute calibration of the receiver are performed.

According to the present invention, it is possible to measure the beam pointing error and perform absolute calibration of the radar even when the mounted moving body is moving. The beam pointing error can be separated into a component in the traveling direction of the moving body and a component in the direction perpendicular to the traveling direction.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the radar apparatus 10 to be calibrated and the arrangement of the radar test apparatus in the antenna beam. A radar test apparatus is arranged along the installation surface 13 within the range 12 of the antenna main beam. When viewed from another angle, radar test apparatuses 21, 22, and 23 are distributed in the beam footprint 15. Each position is recorded by the GPS receiver 5 (FIG. 2). In the case of close arrangement, the positional relationship is measured.

The radar test apparatus of FIG. 2 has a function of receiving radio waves transmitted from the antenna 11 of the radar apparatus 10 and a function of transmitting radio waves toward the antenna 11 of the radar apparatus 10. Those functions are controlled by the controller 4.

P 受信電力(W)、PT 送信電力(W)、l 電波の波長(m)、r 送信/受信アンテナ間距離(m)、GT 送信側アンテナゲイン(絶対利得、単位：倍)、G 受信側アンテナゲイン(絶対利得、単位：倍) A method for measuring the beam pointing error when using two radar test apparatuses 22 and 23 will be described with reference to FIG. Here, Friis' transmission formula is expressed by Equation (1).

P Received power (W), PT Transmitted power (W), l Radio wave wavelength (m), r Transmitter / receiver antenna distance (m), GT transmitter antenna gain (absolute gain, unit: times), G receiver Antenna gain (absolute gain, unit: times)

Equations 2 and 3 are established by the Friis transmission formula between the radar device 10 to be calibrated, the antenna 11, and the radar test devices 22 and 23.

It is assumed that the antenna gains G1 and G2 of the radar test apparatuses 22 and 23 are measured in advance in an anechoic chamber or the like. The antenna gains GT1 and GT2 of the antenna 11 of the radar device to be calibrated can be expressed by equations 4 and 5.

In this equation, θ1 and θ2 are angles shown in FIG. When there is no beam pointing error (that is, Δ = 0), the beam direction coincides with the radar line-of-sight direction 14. G0 is the antenna peak gain, and function f is the antenna pattern, which is expressed as a function of angle. As the antenna pattern f, any of a model based on a Gaussian function or a Sinc function, an actual antenna pattern calculated or measured in advance can be used (the same applies to f1, f2, and f3).

FIG. 4 illustrates the beam pointing error Δ. Due to the beam pointing error Δ, the antenna gain 34 increases to the antenna gain 33, while the antenna gain 35 decreases to the antenna gain 36.

By substituting Equations 4 and 5 into Equations 2 and 3, an unknown number (product of PTG0, Δ) can be obtained. P1 and P2 are values measured by the radar test apparatuses 22 and 23, and r1, r2, θ1, and θ2 are values determined from position information of each apparatus. The method using two radar test apparatuses is particularly effective when the scanning direction of the antenna beam is limited to the left and right directions, as in the case of an onboard radar.

With reference to FIG. 5, a method for measuring a beam pointing error when using three radar test apparatuses 21, 22, and 23 will be described. Here, the case where each radar test apparatus is arranged on the vertex of the right triangle 31 is considered.
According to Friis' transmission formula, Equation 6 is established between the radar device to be calibrated and the radar test device 21 in the same manner as Equations 2 and 3.

The lower left diagram in FIG. 5 shows a relationship between a triangle having the antenna 11 and the radar test apparatuses 22 and 23 as apexes and a straight line 18a obtained by orthogonally projecting the radar line-of-sight direction 18 onto the triangle. Expressions 7 and 8 are established for the antenna gains GT1 and GT2 using the variables in this figure. Here, the peak value of the antenna gain in the cross-sectional direction of the triangle is G′0, and the antenna pattern in the same plane is the function f2.

The lower right diagram in FIG. 5 shows a relationship between a triangle having the antenna 11 and the radar test apparatuses 21 and 22 as vertices and a straight line 18b obtained by orthogonally projecting the radar line-of-sight direction 18 onto the triangle. Equations 9 and 10 are established for the antenna gains GT1 and GT3 using the variables in this figure. Here, the peak value of the antenna gain in the cross-sectional direction of the triangle is G ″ 0, and the antenna pattern in the same plane is the function f3.

6 shows a sphere 33 centered on the antenna 11. When the spherical trigonometry is applied, Expression 11 is established for the beam directing error Δ and Δ2 and Δ3 of Expressions 7 to 10. (An angle is defined as an angle viewed from the center of the sphere 33).

As shown in FIG. 5, by arranging the three radar test apparatuses 21, 22, and 23 on the apex of the right triangle 31, Equation 11 can be expressed in a simple form by applying the cosine law of the spherical trigonometry.

When the radar test apparatuses 21, 22, and 23 are arranged so that one side of the right triangle 31 is parallel to the traveling direction of the moving body, the beam pointing error Δ is perpendicular to the traveling direction component (for example, Δ2) and the traveling direction. It is possible to calculate by separating into components in various directions (for example, Δ3).

Substituting Equations 7 and 8 into Equations 2 and 3 and Substituting Equations 9 and 10 into Equations 2 and 6 yields unknown numbers (product of PTG'0, product of PTG ″ 0, Δ2, Δ3). P3, P1, and P2 are values measured by the radar test apparatuses 21, 22, and 23, and r1, r2, r3, θ1, θ2, θ'1, and θ3 are values determined from position information of each apparatus.

The relationship between Δ obtained from Equation 11 and the radar line-of-sight direction 18c when there is a beam pointing error is shown in the lower part of FIG. Equation 12 is established for the angle θ in the triangle 32. The value of PTG0 is obtained by using the equality of Equations 12 and 7, 9 and the value of PTG'0 or PTG ″ 0.

When the radar line-of-sight direction 18c can be predicted to some extent when there is a beam pointing error, such as when performing repetitive calibration operations, the antenna pattern function (f1, f2, f3) is obtained by installing a radar test device in that direction 18c. Calibration can be performed directly without using it.

Next, a description will be given of a case where the pointing error of the received beam of the antenna 11 of the radar device 10 to be calibrated and the receiver of the radar device 10 are calibrated. In this case, the radio wave 1b transmitted from the antenna 2b of the transmitter 3b of the radar test apparatus of FIG.

Based on the positional relationship between the antenna 11 of the radar device 10 and the radar test devices 21, 22, and 23 using the Friis transmission formula, the beam pointing error measurement and the absolute calibration of the radar device 10 are performed as follows. The same.

An operation flowchart of the radar apparatus 10 and the radar test apparatuses 21, 22, and 23 is shown in FIG. From the radar test apparatuses 21, 22, and 23, continuous waves are transmitted for a predetermined time after different delay times T101 to T103, and received by the antenna 11 of the radar apparatus 10. Specifically, the controller 4 performs a process of receiving the radio wave transmitted from the antenna 11 of the radar apparatus 10 by the radar test apparatus and delaying the transmission timing from the radar test apparatuses 21, 22, and 23 with reference to the reception time. Performed above [(1) Method without referring to GPS time data]. When the time passing through the installation position of the radar test apparatus can be predicted from the orbit information or the like as in the satellite-mounted radar, a method of referring to GPS time data on the radar test apparatus side can be used. In this method, after predicting the time when the moving body on which the radar apparatus 10 is mounted passes through the installation position of the radar test apparatus, time information is obtained from the GPS receiver 5 connected to the controller 4, and the time is used as a reference. Then, processing for delaying the timing of transmission from the radar test apparatuses 21, 22, 23 is performed on the controller 4 [(2) Method of referring to GPS time data].

The transmission time is adjusted so that the radio waves 41a to 43a transmitted from the radar test apparatuses 21 to 23 do not overlap each other (FIG. 8). The power received by the radar apparatus 10 has different received power values 41b to 43b depending on the radar test apparatus on the transmission side as shown in the right figure of FIG.

The range bin in which the echo 44a from the ground surface or the like is mixed is determined by the position of the antenna 11 of the radar device 10 at the time of calibration and the direction of the line of sight of the radar. The transmission timing is delayed (this is common to the methods (1) and (2)). As a method of delaying the timing, there are a method of delaying by the controller 4 and a method of delaying by adjusting the installation position as in Patent Document 2.

Based on the received power values 41b, 42b, and 43b thus obtained, the Friis transmission formula is applied between the radar apparatus 10 and the radar test apparatuses 21, 22, and 23.

Due to the feature that the radar apparatus 10 is mounted on a moving body, it is possible to substantially obtain test data for six units even with three radar test apparatuses (FIG. 9). The radar test apparatus before the movement of the beam footprint is denoted as 21b, 22b, 23b. Save the data at these locations. As an example of the case where the data of the previous position is used, the radar test data at the positions of the radar test apparatuses 21, 22, and 22b is selected to estimate the beam pointing error and perform absolute radar calibration (radar test apparatuses 21 and 22). , 22b is a right triangle).
When the radar test apparatus 23 is installed in the radar line-of-sight direction 18c, absolute calibration is possible without using the antenna pattern function (f1, f2, f3). However, in order to know the radar line-of-sight direction 18c, it is necessary to perform the operations 0010 to 0032 at least once in advance.

The industrial applicability of the present invention is useful as a radar test apparatus used for measurement of beam directivity and absolute calibration of a radar mounted on a moving body such as an automobile, an aircraft, and an artificial satellite.

It is a figure which shows embodiment of this invention. It is a block diagram of a radar test apparatus used in the present invention. It is a figure which shows the positional relationship in the case of using two radar test apparatuses, and the relationship of a radar gaze direction. It is a figure which shows an antenna gain and a beam pointing error. It is a figure which shows the positional relationship in the case of using three radar test apparatuses, and the relationship of a radar gaze direction. It is a figure which shows the beam directing error and the positional relationship of each apparatus. It is an operation | movement flowchart in the case of calibrating the receiver of a radar apparatus. It is a figure which shows the reception data according to the time of the receiver of a radar apparatus, and the reception timing of the electromagnetic wave from a radar test apparatus. It is a figure which shows the positional relationship of a radar test apparatus in case a beam footprint moves.

10: Radar apparatus to be calibrated 11: Antenna of radar apparatus 10
12: Main beam range of the antenna 11 13: Installation surface of the radar test apparatus 14: Radar line-of-sight direction 15: Beam footprint 16: Moving object 17: GPS receiver 21-23: Radar test apparatus

Patent 4070142 “Radio wave axis adjustment device and radio wave axis adjustment method” Patent 4812904 "Radar test equipment"

Claims (4)

A radar test apparatus used for calibration of a radar mounted on a moving body,
The radar test apparatus includes an antenna that transmits and receives radio waves to and from the radar;
A controller that controls transmission and reception of radio waves with the radar;
A device for acquiring position information and time of the radar test device,
A radar test apparatus, wherein two or more radar test apparatuses are installed to measure the radiation pattern of the radar at different positions. The radar test apparatus according to claim 1, wherein three radar test apparatuses according to claim 1 are used, and the three radar test apparatuses are arranged on a vertex of a right triangle. The controller of the radar test apparatus according to claim 1,
A radar test apparatus, wherein a radio wave is transmitted to the radar with a predetermined delay time after receiving the radio wave from the radar. The controller of the radar test apparatus according to claim 1,
A radar test apparatus, wherein a radio wave is transmitted to the radar with a predetermined delay time based on the position information of the radar test apparatus and a time obtained from a device that acquires the time.

Images