JP2730521B2 - Antenna measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an antenna measuring device, and more particularly to an antenna measuring device for measuring the beam directivity of a phased array antenna having a series-fed monopulse distributor.

[0002]

2. Description of the Related Art As a conventional method for measuring the beam directivity of a phased array antenna for performing a monopulse angle measurement, there is a method shown in FIG. FIG. 8 is a diagram showing a configuration of a conventional antenna measuring device.

[0003] Reference numeral 3 denotes a monopulse antenna capable of finely changing a beam scanning angle by electronic scanning.
3a is a sum signal (Σ) output terminal, 3b is a difference signal (Δ)
Output terminal. 1 is a transmitter for generating an RF signal, 14 is a transmitting antenna composed of a plurality of element antennas,
13 is a phase shifter connected thereto, 15 is a phase shifter controller for controlling the same, and 12 is a distribution for distributing and supplying the RF signal from the transmitter 1 to each of the element antennas 14-1 to 14-n. , 4 is a receiver for receiving an RF signal radiated from the transmitting antenna 14 via the monopulse antenna 3, 5 is a turntable for holding and rotating the monopulse antenna, 6 is a turntable controller for controlling its rotation, 7 is It is a signal processor that processes the received signal by the receiver 4 and controls the phase shifter controller 15 and the turntable controller 6.

Next, the operation will be described with reference to FIGS. 9 (a) and 9 (b). FIGS. 9A and 9B are functional explanations showing that the RF signals transmitted from the element antennas 14-1 to 14-n change at the element positions of the transmission antenna 14 depending on the shapes of the monopulse patterns Es and Ed. FIG. It is assumed that the minimum value direction of the difference pattern Ed and the maximum value direction of the sum pattern Es are both scanned from the direction of the mechanical boresight axis 3C by the angle δ.

The operation of the turntable 5 is controlled so that the opening 3 f of the monopulse antenna 3 faces the transmitting antenna 14. By setting the phase of the phase shifter 13 connected to the element antennas 14-1 to 14-n to a certain value, the excitation amplitude and phase of each of the element antennas 14-1 to 14-n are set to a constant initial state. Set. Element antennas 14-1 to 14
When the excitation phase of any one of -n is changed from the initial state by using the phase shifter 13 connected thereto, the phase of the radiated electric field from the transmission antenna 14 changes, thereby causing Each element antenna 14-1 represented by an arrow
The combined electric field of the radiated electric field of 14-n and the radiated electric field of the monopulse antenna 3 in the angular direction in which these elements are viewed changes.

The relative amplitude and relative phase (electric field vector E) with respect to the composite vector in the initial state of the transmitting antenna 14 in which the excitation phase has been changed can be obtained by arithmetically processing the change in the composite electric field. This method is called an element electric field vector rotation method.
This is disclosed as “antenna measurement method” in JP-A-7-93267.

This element electric field vector rotation method is performed while receiving the sum signal output terminal 3a and the difference signal output terminal 3b of the monopulse antenna 3, and all the element antennas 14-1
The absolute value | Ed / Es | of the ratio of the sum pattern reception electric field Es and the difference pattern reception electric field Ed for .about.14-n is determined.
Element antennas 14-1 to 14-1 arranged in the beam scanning direction
By performing an interpolation calculation for each of the absolute values corresponding to the 4-n element columns, the null point (zero point) direction (beam direction) can be obtained. This method is disclosed in Japanese Unexamined Patent Publication No. 3-258102 as an "antenna measuring device".

[0008]

The conventional antenna measuring apparatus is a plane aperture phased array antenna in which the transmitting antenna is composed of a plurality of elements, and it is expected that the aperture of the transmitting antenna is expected to some extent from the center of the aperture surface of the antenna to be measured. The aperture length needs to be large enough to cover the angle range in which the angle is measured. In order to maintain the measurement speed, it is necessary to reduce the element interval between a plurality of elements. This has the problem of increasing the number of elements of the transmitting antenna.

Further, since the transmitting antenna is composed of a plurality of elements, the element electric field vector of each element is measured.
In order to measure the element electric field vector, it is necessary to provide a phase shifter connected to each element, a controller for controlling the phase shifter, and a distributor for distributing a transmission RF signal to each element.

[0010] For these reasons, the conventional method has a problem that the configuration of the transmitting antenna is complicated, the scale is large, the measuring means is complicated, and it takes time.

An object of the present invention is to provide an antenna measuring apparatus capable of measuring a beam directivity in a short time by using a measuring transmitting antenna having a simple configuration.

[0012]

According to the present invention, there are provided a plurality of radiating elements, element excitation condition changing means capable of individually changing the excitation phase conditions of these radiating elements, and a method for converting the received signals of the radiating elements. An antenna measuring apparatus for measuring the beam directivity of a phased array antenna having a monopulse power distribution means for generating a sum signal and a difference signal, wherein the phased array antenna is mounted and a rotation controllable antenna mounting means is provided. A transmitting antenna that radiates a signal to the phased array antenna, and mechanical scanning means capable of controlling movement of the transmitting antenna in a plane orthogonal to a mechanical reference plane or a line of the phased array antenna,
A frequency transmitting unit that divides a predetermined frequency range including a frequency to be measured at predetermined intervals and sequentially generates the transmission signal to the transmitting antenna at regular intervals, and a detection signal synchronized by the frequency transmitting unit at regular intervals. A detection signal generating means for generating, a calculating means for calculating a power ratio of the difference signal to the sum signal based on a timing of the detection signal, and a directional accuracy of the phased array antenna by detecting a zero-point frequency from the power ratio And an antenna measuring device characterized by including means.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention is as follows. That is, in order to know the angle of the difference pattern null point (zero point) direction of the series-fed monopulse antenna, by changing the frequency of the RF signal radiated from one transmitting antenna with the series-fed monopulse antenna fixed, The frequency scanning characteristics of the phased array antenna equipped with a series-fed monopulse power divider can be obtained by the series-fed line, so that a phased array composed of a plurality of elements required for measurement by a conventional antenna measuring device A complicated transmission antenna of the array antenna is not required and is simplified.

Further, since the frequency scanning characteristics of the serial feed line of the serial feed monopulse antenna are used,
The desired result can be obtained by one frequency scan without the necessity of measuring all the elements by the element electric field vector rotation method of a plurality of elements, which is required for the measurement by the conventional antenna measuring apparatus.

Furthermore, since the frequency scanning characteristic of the series feed line is used, the angular resolution depends on the number of divisions (adjacent frequency intervals) of the transmission frequency range, and high resolution can be easily obtained. In addition, by freely setting the adjacent frequency intervals in the transmission signal without making them equal intervals, the resolution can be freely adjusted within one measurement pattern.

An embodiment of the present invention will be described below in detail with reference to the drawings.

FIGS. 1A and 1B are block diagrams showing the configuration of an embodiment of the present invention, and FIG. 2 is a diagram for explaining functions. still,
8 and 9 are denoted by the same reference numerals. For convenience of explanation, the radiation normal 2a of the transmitting antenna 2 and the monopulse antenna reference line 3c are connected to the turntable 5 and the scanner 9 (mechanical) using an optical position detection device 9a mounted on the same line as the radiation normal 2a. By operating the plane scanning means), it is assumed that both directions of the x and y axes already coincide, and the x and y coordinate values of the scanner 9 and the rotation angle of the turntable 5 at this time are known. Further, the distance 1 between the transmitting antenna 2 and the monopulse antenna 3 is also known by a general optical surveying instrument such as transit.

Next, the operation will be described with reference to FIGS.
This will be described with reference to FIG. For convenience of explanation, the direction of the minimum value of the difference pattern Δ and the direction of the maximum value of the sum pattern Σ are all equal to the mechanical boresight axis 3c by the angle θ0 at the frequency f0.
From the direction, a beam controller 8 as an element excitation condition changing means
And phase scanning by the phase shifter 3-2.
Further, the transmission antenna 3 is located at y0 (y0 = tan θ0 · l) from the mechanical boresight axis 3c based on the relationship between θ0 and l.
It is assumed that only the scanner 9 is moving.

The transmitter 1 changes the beam direction shift angle due to the frequency change from the scan angle θ0 at the frequency f0 to + Δ
frequencies f0 + Δf, f0−Δf and f0 that result in θ, −Δθ
Are transmitted to the transmitting antenna 2 via the coaxial cable 1a as one continuous transmitting signal 11 at a constant time interval. An example of this transmission frequency is shown in FIG. The transmitting antenna 2 sends out the transmitting signal 11 to the monopulse antenna 3 via a space.

The monopulse antenna 3 includes a sum signal distributor 3-3a and a difference signal distributor 3-3 of a series-fed monopulse distributor.
3b, the frequency f0-Δf, f0,
f0 + Δf, corresponding to frequency shift angles θ1, θ0,
The sum signal Σ and the difference signal Δ in the direction of the transmitting antenna 2 when the beam is directed to θ2 are transmitted to the receiver 4 via the sum signal output cable 3a and the difference signal output cable 3b, respectively.

The transmitter 1 determines the frequency f0-Δ of the transmission signal 11.
The reception trigger 1b is transmitted to the receiver 4 at the intermediate point between the transmission times of f, f0, f0 + Δf. The receiver 4 samples the ratio Δ / Σ with the difference signal Δ using the sum signal Σ as a comparison reference signal by the reception trigger 1b and sends out the received data to the signal processor 7 via the control cable 7a.

The signal processor 7 has a frequency f0-.DELTA.f, f0,
From the received data of f0 + Δf, a null point (Δ / Σ ratio minimum point) frequency is detected, and a beam direction is calculated. The Δ / Σ ratio of each of the obtained frequencies f0−Δf, f0, f0 + Δf is P0, P1, P2 as shown in FIG.
Since the Δ / Σ ratio is minimum at the frequency f0, it can be known that the monopulse beam is oriented in the direction of θ0 at the frequency f0.

Next, the measurement angle resolution will be described with reference to FIGS. FIG. 5 shows the results obtained in this example. In FIG. 4, E1, E2, and E3 are the measurement results (Δ / Σ voltage ratio) of the frequencies f0−Δf, f0, f0 + Δf of the transmission signal 11, respectively, and are series-feed monopulse distributors 3-3a and 3-3b. It can be seen that in the monopulse antenna 3 having the following, the beam directions are directed in the θ0, θ1, and θ2 directions due to the beam shift corresponding to each frequency constituting the transmission signal 11.

E1 and E2 in FIG. 4 are beam angles at which the frequency interval Δf of the transmission signal 11 and the Δ / Σ ratio become 1, that is, the frequency interval of the transmission signal 11, the sum pattern モ ノ of the monopulse pattern, and the difference pattern Δ intersect. The frequency interval Δf of the transmission signal 11 is the resolution of the measurement angle.

From this, as shown in FIG. 5, the frequency interval of the transmission signal 11 is changed from the frequency f0−Δf to the frequency f0 +
The transmission signal 11 is divided by n (n is 3 or more) up to Δf, the transmission signal 11 whose frequency interval is fs is generated by the transmitter 1, and transmitted from the transmission antenna 2 to the monopulse antenna 3. The monopulse antenna 3 and the receiver 4 operate as described above, and the signal processor 7 generates the Δ corresponding to each frequency constituting the transmission signal 11.
Take the correlation of the / Σ ratio.

E1 to En shown in FIG. 5 show the results, from which it is understood that the measurement angle resolution can be determined by the transmission frequency interval of the transmission signal 11.

Next, a method of measuring the beam direction will be described with reference to FIGS. For convenience, when the beam phase scanning angle set at the frequency f0 is θ0, it is assumed that the true beam direction is shifted from θ0 by θM.

As in the above embodiment, the frequency range where the Δ / Σ ratio is 1/1 (frequency f0−Δf to frequency f0 + Δf)
Is divided by n which can obtain a sufficient angular resolution, a transmission signal 11 whose frequency interval is fs is generated by the transmitter 1, and transmitted from the transmission antenna 2 to the monopulse antenna 3.

As in the above embodiment, when the Δ / す る ratio corresponding to each frequency constituting the transmission signal 11 is measured and output, as shown in FIG. 6, the null point (Δ / （ratio minimum point) frequency of the monopulse pattern is obtained. Is a point fM instead of f0 because the beam phase scanning angle is shifted by θM. At this time, if the angular resolution based on the frequency interval fs is θs, the true beam scanning angle θM is θM = θ0 − [(f0−fM) × θs / fs], and the true beam scanning angle can be measured.

[0030]

As described above, according to the present invention, an antenna beam directivity measuring method utilizing a frequency characteristic of a series feed line of a monopulse antenna using a series feed type distribution system is used, as in the prior art. In addition, there is an effect that the transmitting antenna is not large and complicated, and the frequency scanning time can be measured in an extremely short time.

Further, according to the present invention, since the antenna beam directivity measuring method utilizing the frequency characteristics of the series feed line of the monopulse antenna using the series feeding type distribution system is used, the measurement angular resolution is limited to the frequency range to be transmitted. It is possible to determine the frequency intervals adjacent to each other at the time of division, and thus it is effective to change the frequency intervals according to the required measurement resolution.

[Brief description of the drawings]

1A and 1B are diagrams showing an embodiment of the present invention, in which FIG. 1A is a configuration diagram, FIG. 1B is a functional block diagram thereof, and FIG. 1C is a diagram showing a frequency of a transmission signal for measurement.

FIG. 2 is a functional block diagram for explaining the operation of the configuration of FIG. 1;

3A is a diagram showing a relationship between a monopulse pattern frequency and a received signal, FIG. 3B is a monopulse pattern frequency scan diagram,
(C) is a reception trigger waveform diagram, and (d) is a diagram showing the relationship between the monopulse pattern frequency and the Δ / Σ ratio.

FIG. 4 is a diagram illustrating the resolution of an embodiment of the present invention.

FIG. 5 is a diagram illustrating a change in resolution in an embodiment of the present invention.

FIG. 6 is a diagram illustrating a beam direction measurement technique according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating transmission and reception timings in the embodiment of the present invention.

FIG. 8 is a configuration diagram illustrating an example of a conventional antenna measurement device.

FIG. 9 is an explanatory diagram of functions in the example of FIG. 8;

[Explanation of symbols]

 Reference Signs List 1 transmitter 2 transmission antenna 3 monopulse antenna 4 receiver 5 turntable 6 turntable controller 7 signal processor 8 beam controller 9 scanner 10 scanner controller 11 transmission signal

Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01Q 25/02 H01Q 25/02

Claims (3)

(57) [Claims] 1. A plurality of radiating elements, element excitation condition changing means capable of individually changing excitation phase conditions of these radiating elements, and a monopulse for generating a sum signal and a difference signal from each received signal of the radiating elements. An antenna measuring device for measuring the beam directivity of a phased array antenna having power distribution means, comprising: an antenna mounting means mounted with the phased array antenna and capable of rotation control, and radiating a signal to the phased array antenna. A transmitting antenna, mechanical scanning means capable of controlling the movement of the transmitting antenna in a plane orthogonal to a mechanical reference plane or a line of the phased array antenna, and a predetermined frequency range including a frequency to be measured at predetermined intervals. Frequency transmitting means for transmitting the transmission antenna while dividing and generating it at regular time intervals; and A detection signal generation means for generating a detection signal in synchronization with each of the predetermined time that a calculation means for calculating a power ratio of the difference signal to the sum signal by the timing of the detection signal,
Means for detecting a zero-point frequency from the power ratio to calculate the directional accuracy of the phased array antenna. 2. An antenna measuring apparatus according to claim 1, wherein said mechanical scanning means has one detecting means for optically matching a radiation normal of said transmitting antenna with said reference plane or line. . 3. The antenna measuring apparatus according to claim 1, wherein the number of divisions of the predetermined frequency range is three or more.