JPH09148836A - Antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an increase in side lobe, a decrease in gain, etc., by compensating the influence of mutual coupling between elements by multiplication by a measured value of array element directivity. SOLUTION: A signal whose frequency is converted by a receiver 2 is converted by an analog-digital converting circuit 3 into a digital signal, which is multiplied by a weight multiplying circuit 5 by a weight; and an adding circuit 5 adds a received signal outputted from another weight multiplying circuit to obtain desired array directiveity. Here, a weight controller 7 sends an ideal excitation distribution vector W=(W1 ...WN) forming a radiation pattern such as a desired side-lobe reduced beam and a shaped beam to an arithmetic unit 8. A storage device 7 sends the inverse matrix C<-1> of a stored mutual coupling matrix C between elements to the arithmetic unit 8. The arithmetic unit 8 calculates an excitation distribution vector W'=(W'1 ...W'N) from W'=WC<-1> and sets W' in the weight multiplying circuit 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna comprising an element antenna arranged on a plane or a curved surface, a weight multiplication circuit connected to each element antenna, and an addition circuit connected to each weight multiplication circuit and adding the outputs of the weight multiplication circuits. It relates to the device.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional antenna device, in which 1 is an N element antenna arranged on a plane, 2 is a receiver, 3 is an analog / digital conversion circuit, and 4 is weight multiplication. The circuit 5 is an adder circuit.

Next, the operation will be described. The reception signal received by the element antenna 1 is sent to the receiver 2 connected to each element antenna, and frequency conversion is performed. The signal frequency-converted by the receiver 2 is converted into a digital signal by the analog / digital conversion circuit 3, multiplied by a weight for forming a desired array directivity by the weight multiplication circuit 4, and then added by the addition circuit 5. And the received signal output from the weight multiplication circuit are added to obtain a desired array directivity.

Mutual coupling between elements exists between the element antennas. Mutual coupling between elements changes the element directivity (array element directivity) in the array operating state from the single element directivity, resulting in deterioration of antenna performance such as side lobe increase and gain decrease.

[0005]

Since the conventional antenna device is configured as described above, the antenna performance is deteriorated due to the influence of mutual coupling between the elements, such as an increase in side lobes and a decrease in gain.

The antenna device according to the present invention is for solving the above-mentioned problems, and in an antenna device in which elements are arranged on a curved surface or a plane, mutual coupling between elements is measured by array element directivity. It is an object of the present invention to provide an antenna device in which an increase in side lobes, a decrease in gain, and the like are reduced by multiplying by and compensating for the effect.

Further, the antenna device according to the present invention is
The object is to realize a circuit that is simple and can be realized even if the number of elements is increased.

Another object of the antenna device according to the present invention is to shorten the test adjustment time of the antenna.

[0009]

Embodiment 1 of the present invention
The antenna device by is in the observation range of the array element directivity.

[0010]

(Equation 3)

Is g_i Optimal near in the least-squares method of (θ)
Mutual coupling between elements so that it becomes a similar function c _inCalculating
Then, the mutual coupling matrix C between elements is calculated, and the mutual coupling row between elements is calculated.
Inverse matrix C of column C^-1Storage device that stores
Distribution vector W = [w₁ ... w_N ] Calculate or store
Between the weight control device and the element output from the storage device
Inverse matrix C of mutual coupling matrix C^-1And the weight control device
Calculation from the applied ideal excitation distribution vector W W '= W
C^-1The excitation distribution vector set for each weight multiplication circuit by
A computing device for computing the cuttle W'is provided.

The antenna device according to the second embodiment of the present invention includes an inner product calculating circuit adjacent to each weight multiplying device as the calculating device in the first embodiment.

[0013] The antenna device according to the third embodiment of the invention, 'by = WC ^-1 excitation distribution w of the element' operation W In calculating _i, the W 'using all the elements of the matrix C ^-1 Rather than calculating, the calculation is performed using only elements that correct the effect of mutual coupling between elements whose element spacing is narrower than a preset threshold value.

Further, the antenna device according to the fourth embodiment of the present invention measures the array element directivity at every constant interval frequency of the operating frequency band, obtains the mutual coupling matrix C between elements, and extends the matrix element over the operating frequency. interpolation, to calculate the inverse matrix C ^-1, stores the inverse matrix C ^-1 of operating frequency all the bands in the storage device.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 is a configuration diagram showing a first embodiment of the present invention, in which 1 is an N element antenna arranged on a plane or a curved surface, 2 is a receiver, 3 is analog / analog
A digital conversion circuit, 4 is a weight multiplication circuit, 5 is an addition circuit, 6 is a weight control device, 7 is a storage device, and 8 is an arithmetic device.

Next, the operation will be described. The reception signal received by the element antenna 1 is sent to the receiver 2 connected to each element antenna, and frequency conversion is performed. The signal frequency-converted by the receiver 2 is converted into a digital signal by the analog / digital conversion circuit 3, multiplied by the weight by the weight multiplication circuit 5, and received by the addition circuit 5 from another weight multiplication circuit. Is added to obtain the desired array directivity. Here, the weight control device 7 uses the single element directivity f _n (θ) to form an ideal excitation distribution vector W = [w ₁ ... - Send a w _N] to the computing device 8. The storage device 7 sends the stored inverse matrix C ⁻¹ of the interelement mutual coupling matrix C to the arithmetic device 8. Arithmetic unit 8
Is the excitation distribution vector W '= by the calculation W' = WC ^-1
[W ′ ₁ ... w ′ _N ] is calculated, and the weight multiplication circuit 5
Set W'to.

Here, the inter-element mutual coupling matrix C in the storage device 7 is obtained as follows. FIG. 2 is a diagram showing mutual coupling between elements on a plane or a curved surface. In the figure, 1 is N element antennas arranged on the curved surface, and f _n.
(Θ) is the element directivity of the element n, g _i (θ) is the array element directivity of the element i, and c _in is the mutual coupling between elements n to i. The array element directivity of the element i is expressed by the following equation.

[0018]

(Equation 4)

In the equation (4), g _i (θ) is a desired function in the optimal value problem, f _n (θ) is an expansion function, and c _in
Can be regarded as the expansion coefficient. Therefore, c _in can be calculated as a coefficient that minimizes the mean square error shown _in “Equation 5”.

[0020]

(Equation 5)

[0021] theta ₁ in "Number 5" measurement start angle g _i (θ), θ ₂ denotes the measurement end angle g _i (θ).
By expanding “Equation 5”, the following equation is obtained.

[0022]

(Equation 6)

Here,

[0024]

(Equation 7)

[0025]

(Equation 8)

[0026]

(Equation 9)

[0027]

(Equation 10)

In order to minimize ε in "Equation 5", the following equation may be established.

[0029]

[Equation 11]

Therefore,

[0031]

(Equation 12)

Similarly,

[0033]

(Equation 13)

Re () in "Equation 12" and "Equation 13"
Indicates the real part of the variable, and Im () indicates the imaginary part of the variable. "Number 1
The following equation is obtained from 2 ”and“ Equation 13 ”.

[0035]

[Equation 14]

Under the condition of "Equation 14" = 0, the following N linear expressions are obtained.

[0037]

(Equation 15)

Representing "Equation 15" using a matrix,

[0039]

(Equation 16)

Therefore, the mutual coupling c _in between the elements n to i is calculated by the following equation.

[0041]

[Equation 17]

C for all elements (i = 1 ... N)
Obtaining _in gives the following formula.

[0043]

(Equation 18)

Next, by using the mutual coupling matrix between elements,
It will be described that the rise of the side lobe and the decrease of the gain can be reduced. An ideal excitation distribution vector for forming a desired radiation directivity of a side-lobe-reduced beam, a shaped beam, or the like using the element directivity f _n (θ) is W = [w ₁ ... w _N ]
(W _i is the ideal excitation distribution be set to the element i) a.
By using W, the radiation directivity F of the desired array antenna
(Θ) is represented by the following equation.

[0045]

[Equation 19]

By substituting "Equation 18" into "Equation 19",

[0047]

(Equation 20)

From "Equation 20", the excitation distribution vector W '=
The following expression is obtained as [w ′ ₁ ... W ′ _N ] (w ′ _i is the excitation distribution set for the element i).

[0049]

(Equation 21)

The excitation distribution vector W'is calculated by the arithmetic unit 8 as is clear from "Equation 21", and the weight multiplication circuit 5
By setting to, it is possible to set the excitation distribution that compensates for the effect of mutual coupling between elements to each element, and it is possible to suppress the rise of side lobes and the decrease of gain due to mutual coupling between elements. is there. In FIG. 3, an example of an array radiation pattern when the excitation distribution vector W that does not compensate mutual coupling between elements is set in the weight multiplication circuit 5 is shown by a dotted line, and the excitation distribution vector W ′ that compensates mutual coupling between elements is weight multiplied. An example of the array radiation pattern when it is set in the circuit 5 and used is shown by a solid line. It can be seen that the side lobe is reduced and the gain is increased by setting the excitation distribution that compensates for the effect of mutual coupling between elements in each element.

Embodiment 2 FIG. 4 shows a weight control device 6
It is a block diagram which shows Embodiment 2 which calculates W'in the inner product arithmetic circuit adjacent to each weight multiplication circuit from W output from. In FIG. 4, W output from the weight control circuit 6 is sent to the inner product calculation circuit 9 adjacent to each weight multiplication device 4. The storage device 7 stores the stored element c ⁻¹ _ni (n = 1 ... N) of the matrix C ⁻¹ in the inner product arithmetic circuit 9 of the element i.
Output to The inner product calculating circuit 9 of the element i calculates w ′ _{i according} to “Equation 22”.

[0052]

(Equation 22)

In the second embodiment shown in FIG. 4, since the weight calculation is performed in parallel for each element, the calculation time can be shortened, and the simplification can be realized even if the number of elements is increased.

Embodiment 3 FIG. When the number of elements in the antenna device of the first or second embodiment increases, the amount of calculation in the arithmetic unit 8 or the inner product arithmetic circuit 9 increases. However, as shown in FIG. 5, when the distance between the elements is large, the mutual coupling amount between the elements becomes small. Therefore, the shaded portion of the matrix C in FIG. Therefore, it is assumed that the inverse matrix C ⁻¹ also has a shaded portion substantially equal to 0, and that the shaded portion of the matrix C ⁻¹ is 0, even if the operation of “Equation 21” or “Equation 22” is performed. The top is safe. Therefore, "Number 2
In case of 2 ”,

[0055]

(Equation 23)

W ′ _i can be calculated as Here, D (i, n) represents the distance between the element i and the element n, and
_th is a constant determined by the shape of the element antenna. Therefore, the amount of calculation in the arithmetic unit 8 and the inner product arithmetic circuit 9 can be reduced, and even when the number of elements is large, the arithmetic circuit can be simplified and the beam direction switching time can be shortened.

Embodiment 4 FIG. In the antenna device of the first or second embodiment, when the operating frequency is not single, the array element directivity g _i in the entire operating frequency band
It is necessary to measure (θ) and calculate C ^-1 . However, as shown in FIG. 6, the mutual coupling between elements c _ni shows a gradual change with frequency. Therefore, g _i (θ) is calculated at all operating frequencies, the mutual coupling matrix C between elements is calculated, and C _i
^-1 is not calculated, but the array element directivity g _i (θ) is measured at regular intervals of the frequency band, the interelement mutual coupling matrix C is calculated, and the elements are interpolated over the frequency band, By calculating C ^-1 at each operating frequency and storing it in the storage device 7, it is possible to reduce the number of times the array element directivity g _i (θ) is measured and shorten the antenna test adjustment time.

Although the digital beam forming antenna device has been described in the above first to fourth embodiments,
The present invention is not limited to this, and can be applied to, for example, a phased array antenna device including a microwave attenuator and a phase shifter.

[0059]

According to the first embodiment of the present invention, it is possible to set the excitation distribution in which the influence of mutual coupling between elements is compensated for in each weight multiplication circuit, and suppress the rise of side lobe and the decrease of gain. can do.

According to the second embodiment of the present invention, each element w _i 'in the operation W' = WC ^-1 is calculated in parallel by the inner product operation circuit, so that the configuration is simple and inexpensive, and the beam direction is reduced. It is possible to shorten the switching time.

According to the third embodiment of the present invention, in calculating the excitation distribution w'i of the element _i , among the elements of the inverse matrix C ^-1 of the inter-element mutual coupling matrix C, the elements in the vicinity of the element of interest. By using only the element that corrects the effect of mutual coupling with, it is possible to reduce the amount of calculation in the arithmetic unit and inner product arithmetic circuit, and even if there are many elements, the configuration is simple and inexpensive, and the beam direction switching time Can be shortened.

According to the fourth embodiment of the present invention, the array element directivity g ₁ (θ) is measured at every constant interval of the frequency band, the interelement mutual coupling matrix C is calculated, and the element is set to the frequency band. It is possible to reduce the number of times the array element directivity is measured and to shorten the test adjustment time of the antenna by interpolating over C, calculating C ^-1 at each operating frequency, and storing it in the storage device.

[Brief description of the drawings]

FIG. 1 is a first embodiment of an antenna device according to the present invention.
FIG.

FIG. 2 is a first embodiment of the antenna device according to the present invention;
FIG. 3 is a diagram showing mutual coupling between elements in FIG.

FIG. 3 is a first embodiment of the antenna device according to the present invention.
It is a figure which shows the effect in.

FIG. 4 is a second embodiment of the antenna device according to the present invention;
FIG.

FIG. 5 is a third embodiment of the antenna device according to the present invention.
FIG.

FIG. 6 is a fourth embodiment of the antenna device according to the present invention.
FIG.

FIG. 7 is a diagram showing a configuration of a conventional antenna device.

[Explanation of symbols]

1 element antenna, 2 receiver, 3 analog / digital conversion circuit, 4 weight multiplication circuit, 5 addition circuit,
6 weight control device, 7 storage device, 8 arithmetic device,
9 Inner product calculation circuit.

Claims (4)

[Claims] 1. N (N) arranged on a plane or a curved surface.
Is a natural number of 2 or more), a weight multiplication circuit connected to each element antenna, and an adder circuit connected to each weight multiplication circuit and adding the outputs of the N weight multiplication circuits. A weight controller that calculates an ideal excitation distribution vector W = [w ₁ ... w _N ] from f _i (θ) (i = 1 ... N), and array element directivity g _{i of} all element antennas (Θ)
(I = 1 ... N) is measured, and the mutual coupling c _in between elements, which is the cause of the difference between the directivity of the single element and the directivity of the array element, is calculated from the measured values of the directivity of each array element for all the elements. “Equation 1” (θ ₁ is the measurement start angle, θ ₂ is the measurement start angle)
Then, the inter-element mutual coupling matrix C shown in “Equation 2” is obtained, and its inverse matrix C ⁻¹ is calculated to obtain the inverse matrix C.
^From the storage device for storing ⁻¹ , the ideal excitation distribution vector W output from the weight control device, and the inverse matrix C ⁻¹ of the inter-element mutual coupling matrix output from the storage device,
Calculating W '= WC excitation distribution vector W to be set to each weight multiplier circuit by _{^{-1' = [w 1 '···}} w N'] antenna apparatus characterized by having an arithmetic unit for calculating the. (Equation 1) (Equation 2) Wherein said arithmetic unit, when the inner product computation circuit adjacent to each weight multiplication circuits provided, calculates the excitation distribution vector W to be set to each element _{'= [w 1' ··· w} N '] 2. The antenna device according to claim 1, wherein each element in the vector operation W '= WC ^-1 is calculated in parallel by each inner product operation circuit. 3. The arithmetic unit described above does not calculate W ′ by using all the elements of the matrix C ⁻¹ , but determines the influence of mutual coupling between elements whose element spacing is narrower than a preset threshold value. The antenna device according to claim 1 or 2, wherein the calculation is performed using only an element to be corrected. 4. The storage device described above measures array element directivity for each constant interval frequency of an operating frequency band, obtains an element mutual coupling matrix C, and interpolates and inverse matrix the matrix elements over the operating frequency. The antenna device according to claim 1 or 2, wherein C ^-1 is calculated and an inverse matrix C ^-1 of the entire operating frequency band is stored.