JPH0215122B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention consists of a plurality of element antennas, a variable phase shifter is connected to each element antenna, and the phase of these phase shifters is controlled to electronically perform beam scanning or pattern shaping. Array antenna, or phased array antenna
The present invention relates to an antenna measurement method that can accurately measure the excitation amplitude and phase of each element antenna in the operating state of all element antennas.

In order to obtain a desired radiation pattern using a phased array antenna, such as a low sidelobe pattern, a shaped pattern (cosec ² pattern, fan beam, monopulse pattern, etc.), or a scanning beam pattern, the excitation amplitude and phase of each element antenna must be adjusted. must be set to the required value, but this depends on the state in which all element antennas are operating (hereinafter referred to as the "all array operating state"), that is, the feeding circuit characteristics of the phased array as a whole, the mutual coupling between element antennas, and the It has no practical meaning unless it is set in a state that takes into account various influences and conditions such as variations in characteristics.To do this, it is necessary to accurately know the excitation amplitude and phase of each element antenna in all the array operating states. is necessary.

Normally, a phased array antenna basically has a configuration as shown in FIG. That is, the first
In the figure, 1 is an element antenna, 2 is an array antenna consisting of a plurality of element antennas 1, 3 is a variable phase shifter, 4 is a power divider, and 5 is a transmission source.

FIG. 1 shows an example of transmission, and if the transmission source 5 is replaced with a receiver, the structure becomes a phased array antenna for reception. In FIG. 1, signal power generated by a transmission source 5 is distributed to each phase shifter 3 at a required distribution ratio by a power divider 4, and is radiated into space from an element antenna 1. In this case, the excitation distribution that should be given to the array antenna 2 to obtain the desired radiation pattern, that is, the excitation amplitude and phase that should be given to each element antenna 1, is determined by the so-called directional synthesis theory of conventional antenna engineering. be done. Therefore, in the phased array antenna shown in FIG. Set by adjusting the phase. However, as a practical matter, the distribution ratio and the set phase of the phase shifter always involve errors. That is, since the element antennas 1 are arranged relatively close to each other, the input impedance of the element antenna 1 is different from when the element antenna 1 is placed alone due to coupling between the element antennas, and the set phase is different. deviates from the desired value. Moreover, variations occur in the characteristics of the power divider 4, phase shifter 3, and element antenna 1 due to manufacturing precision. Furthermore, since the surrounding environment is different between the central part and both ends of the array antenna 2, the characteristics (input impedance, radiation pattern, etc.) of the element antenna 1 are different. Therefore, in order to realize a low sidelobe pattern and an excitation distribution necessary for precise pattern forming, it is first necessary to accurately know the amplitude and phase of each element antenna 1 in the operating state of the entire array as shown in FIG. 1, for example. This is because if the amplitude and phase are accurately known, the amount of correction for the excitation amplitude and phase that is originally required can be found, and the correct amplitude and phase can be set. A conventional method for measuring the amplitude and phase of element antennas in all array operating conditions will be explained with reference to FIG.

First, in the operating state of the entire array shown in FIG. 1, the combined electric field vector is represented by the sum of the electric field vectors from each element antenna 1, as shown in FIG. 2a. Here, the n-th element antenna 1 (hereinafter,
If the electric field vector of the n-th element is E _oe ^j 〓 ⁿ and this phase φn is changed, the electric field vector of the entire array composition changes with the rotation of the electric field vector of the n-th element. By measuring only the change in the amplitude of this composite electric field vector, the relative amplitude, phase En/E ₀ , and φn−φ ₀ of the n-th element can be determined as follows.

The combined electric field vector when the phase of the n-th element is changed by Δ is expressed by the following equation.

E〓 ₁ =E ₀ e ^j 〓 ^o −Ene ^j 〓 ⁿ (1−e ^j △) (1) Therefore, if we set X=φn−φ ₀ (2) and transform equation (1), we get It will look like this:

E〓 ₁ = {(E ₀ cosX＋Encos△−En)+j(−E ₀ sin
X+Ensin△)}e ^j(X+ 〓 ₀ ⁾ (3) Therefore, by setting k=E _o /E ₀ (4), the following equation is derived from equation (3).

｜E ₁ ｜ ² /E ₀ ² =Y ² +k ² +2kycos (△+△ ₀ ) (5) However, Y ² = (cosX−k) ² +sin ² X (6) tan△ ₀ = sinX／cosX−k (7) That is, due to the phase change of the n-th element, the combined power level changes at cosine from equation (5) as shown in FIG. 2b. Here, if the ratio between the maximum value and the minimum value of the cosine change is r ² , then from equation (5), r ² =(Y+k) ² /(Y-k) ² (8). Also, from equation (5), _-Δ0 is the amount of phase change that gives the maximum value of the cosine change. These r and △ ₀
is the amount obtained by measuring the relative power in equation (5), and from this r and △ ₀ , the relative amplitude of the nth element (k =
En/E ₀ ) and relative phase (X=φn−φ ₀ ) are determined as follows.

From equation (8), r=±(Y+k/Y-k) (9), and considering the case of a positive sign, Y=(r+1/r-1)k(10), and equation (7) Therefore, sin△ ₀ = sinX/Y (11) cos△ ₀ = cosX−k/Y (12). Therefore, if Y is eliminated from equations (10), (11), and ( ₁₂ ), the simultaneous equation of k and r-1 cos△ ₀ )k (14) is obtained, and by solving this, the following equation is obtained.

However, p=r-1/r+1 (17) The above applies when the right side of equation (9) has a positive sign, but if it also has a negative sign, the following equation can be obtained in the same way.

In other words, if the phase of the n-th element is changed by the phase shifter 3 and the change in the combined power level is measured, a cosine-like level change (equation
(corresponding to (5)) is obtained, and the maximum/minimum ratio, r, and maximum point Δ ₀ are determined from the data. These r
and Δ ₀ to form equations (15), (16), or (18),
By calculating (19), the relative amplitude and phase of the element antenna whose phase has been changed can be determined. By repeating the same measurement, data processing, and calculation for all the element antennas 1 with the same initial settings, it is possible to know the relative amplitudes and phases of all the element antennas.

The conventional measurement method is as described above,
As shown in Figures 2a and b, as the number of element antennas increases, the relative amplitude of each element antenna decreases, and the change in relative power given by equation (5) also decreases, reducing the influence of measurement errors. Therefore, there is a drawback that the accuracy of the relative amplitude and phase calculated from the measured data decreases.

The antenna measurement method according to the present invention has been made to eliminate the above-mentioned drawbacks, and provides a measurement method that can prevent deterioration of measurement accuracy by dividing the array antenna into a plurality of subarrays and performing measurements. It is.

The antenna measurement method of the present invention will be explained below.

That is, as shown in FIG. 3, by dividing the array antenna 2 consisting of each element antenna 1 into N subarrays 2A to 2N, as shown in FIG. The relative amplitude of each element antenna 1 is expressed as the array antenna 2.
It can be increased depending on the number of elements. Therefore, the change in the combined power level obtained by changing the phase of the phase shifter 3 connected to each element antenna 1 in each sub-array 2A to 2N is as shown in FIG. 4b, compared to the conventional one. Since it can be increased, the maximum-to-minimum ratio r ² of the power level change and the amount of phase change Δ ₀ that gives the maximum value can be determined with high accuracy. For example, with normal measuring equipment, 0.1~
Since there is a measurement error of about 0.3 dB, in order to ensure measurement accuracy, it is necessary to make the change in the combined power level in each subarray 2A to 2N 1 dB or more. By doing this, each subarray 2
Applying the above-mentioned measurement method for each A to 2N, equations (15), (16) or equations (18), (19) are calculated using the maximum-to-minimum ratio r ² and the amount of phase change Δ ₀ that gives the maximum value. By calculation, the relative amplitude and phase of the phase-changed element antennas 1 in each sub-array 2A to 2N can be determined with high accuracy.

For example, when specifically measuring sub-array 2A, if the reference phase of the composite electric field vector of sub-array 2A is φ ₀ , then the phases of sub-arrays 2B to 2N are set to be in opposite phases to each other so as to differ by ±90° from φ ₀ , The combined electric field vector of subarrays 2B to 2N may be set to zero.

Also, the relative amplitude between each subarray 2A to 2N
The phase is determined by connecting the phase shifter 3 connected to the element antenna 1 of each subarray 2A to 2N to each subarray 2A to 2N.
Each subarray 2A is controlled to have the same phase.
By regarding ~2N as one element and applying the above-mentioned measurement method, it can be determined with high accuracy in the same manner as above.

In the above explanation, the phased array antenna shown in FIG. 3 was used as an example, but the antenna measurement method according to the present invention can be applied to any type of element antenna, array configuration of element antenna, configuration or type of feeding circuit, etc. It can be applied to all phased array antennas. Further, as a method of dividing the array antenna, it is possible to divide each subarray into small blocks one after another, regardless of the method of division or the number of divisions.

As described above, in the measurement method according to the present invention, each element antenna of a phased array antenna is divided into a plurality of subarrays, and the change in combined power with respect to the phase change of the phase shifter connected to each element antenna in each subarray is calculated. By measuring, it is possible to accurately measure the amplitude and phase of the element antennas in the entire array operating state, regardless of the number of elements in the phased array antenna, so it can be said that the practical effect is extremely large.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a phased array antenna, Fig. 2 a and b are explanatory diagrams and characteristic diagrams of the electric field vector and composite electric field vector of an element antenna measured by the conventional measurement method, and Fig. 3 is an antenna of the present invention. Configuration diagram for explaining the measurement method, Figure 4 a and b
FIG. 2 is an explanatory diagram and a characteristic diagram of an electric field vector and a composite vector of an element antenna according to the measurement method of the present invention. In the figure, 1 is an element antenna, 2 is an array antenna, 3 is a phase shifter, 4 is a power divider, and 5 is a transmission source. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

Claims (1)

[Scope of Claims] 1. An antenna measurement method for measuring the amplitude and phase of each element antenna of a phased array antenna consisting of a plurality of element antennas and a phase shifter connected to each element antenna. Divide the ray antenna into multiple subarrays, change the phase of the phase shifter connected to each element antenna in each subarray, measure the combined power of the phased array antenna, and measure the maximum power level change. Find the phase change amount △ ₀ that gives the minimum ratio r ² and the maximum value, calculate the amplitude and phase of each element antenna in each subarray from these r and △ ₀ , and measure the relative amplitude and phase between each of the above subarrays. To achieve this, by changing the phase shifter connected to each element antenna in each subarray in the same phase and performing the same measurements and calculations as above,
An antenna measurement method characterized by calculating the amplitude and phase of each element antenna of the phased array antenna. 2. The antenna measurement method according to claim 1, characterized in that the phases between each subarray other than the subarray to be measured are set to be opposite phases, and the combined electric field vector is made zero.