JPH0449804B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic scanning antenna using multiple phase shifters.

FIG. 1 shows a conventional electronic scanning antenna, in which 1a to 1n are element antennas, 2a to 2n are phase shifters, 3a to 3n are phase shifter drive circuits, and 4a to 4n are phase shifters.
5 is a power feeding transmission line, 5 is a control circuit, 6 is a transmission/reception switch, 7 is a transmitter, and 8 is a receiver. This electronic scanning antenna sends a control signal from the control circuit 5 to the phase shifter drive circuits 3a to 3n, and controls the amount of phase shift of each of the phase shifters 2a to 2n in accordance with the arrangement order of the phase shifters 2a to 2n. As shown in Figure A, linear functional change (dotted line)
The beam direction θ is controlled as shown in FIG. 2B.

By the way, in the conventional antenna of this kind, when scanning the beam, an electronic computer is used to calculate B=
Digital phase changes are performed using a phase angle of 2π/2p (P: number of bits) as the minimum unit, but each antenna element has ±B/2p as shown in Figure 3.
A phase error (quantized phase error) in two ranges occurs, and this has the disadvantage that a large sidelobe occurs in a particular direction in the radiation pattern of the electronic scanning antenna.

In order to eliminate the above-mentioned conventional drawbacks, the electronic scanning antenna according to the present invention changes the electrical length of the feeding transmission line so as to disperse the quantization phase error that causes a large sidelobe in a specific direction. Furthermore, in reality, it is not possible to continuously change the electrical length of the power feeding transmission line, so providing it stepwise as in the present invention is essential for realizing hardware.

FIG. 4 shows an embodiment of the present invention, which will be described in detail below.

In FIG. 4, 1a to 1n are element antennas,
2a to 2n are phase shifters, 3a to 3n are phase shifter drive circuits, 4a to 4n are power feeding transmission lines, 5 is a control circuit, 6 is a transmission/reception switch, 7 is a transmitter, 8 is a receiver, 9a to 4n 9n is a phase adjuster.

In such a configuration, the phase of the input signal of the phase shifter 2i related to the i-th element antenna 1i is adjusted using the phase adjuster 9i, for example, using the phase of the transmitter output end as a reference, as shown in equation (1). Adjust stepwise.

[−α{i−(n−1/2)} ^2m ] _D …(1) However, α is an arbitrary constant, i=1, 2,…, n,
m is a natural number (1, 2,...). However, [X]
The symbol _D means the value when the step width is the step width of D closest to X.

When the phase shift amount of the phase shifter 2i is set as shown in equation (2) using the control signal from the control circuit 5, the phase of the signal supplied to the element antenna 1i becomes as shown in equation (3).

[[α{i-(n+1/2)} ^2m ] _D -βi] _B ......(2) [[α{i-(n+1/2)} ^2m ] _D -βi] _B - [α
{i-(n+1/2)} ^2m ] _D ...(3) However, the symbol [X] _B means that the digital phase amount quantized by B closest to X is taken. β is a constant corresponding to the beam scanning angle.

From this, the radiation pattern E(θ) of the electronic scanning antenna as a whole is expressed by equation (4), where d is the antenna element spacing and k is the propagation constant, and in the main lobe direction where equation (4) is maximum. is expressed by equation (5).

E(θ)= _o 〓 〓 ⁱ⁼¹ Iie ^jkdisin 〓ej [[α{i-(n+1/2)} ^2m ] _D
−βi〕 _Bx e−j[α{i−(n+1/2)} ^2m ] _{D o} 〓 ^I=1 Iie ^j { ^kdisin 〓 ^- 〓 ⁱ }e ^jE ……(4) However, Ii is the i-th element The excitation amplitude of the antenna is E=[[α{i-(n+1/2)} ^2m ] _D −βi] _B − [[α{i-n+1/2)} ^2m ] _D −βi].

θ=sin ^-1 (β/kd) ...(5) Furthermore, E=[[α{i-(n+1/2)] listed in equation (4)
} ^2m ] _D −βi〕 _B −[[α{i−(n+1/2)} ^2m ] _D −βi
] is the quantization phase error (B
is 0, then D is also 0). This differs from the conventional quantization phase error in that it has less periodicity and is more dispersed.

Now, this principle will be explained using diagrams.

FIG. 5 explains this principle, and in the figure, a represents the phase shifters 2a to 2 before they are made into a stepped shape.
b is the phase distribution of the input signals of the phase shifters 2a to 2n after making them stepwise; c is the phase distribution of the input signals of the phase shifters 2a to 2n; d is the phase distribution of the input signals of the phase shifters 2a to 2n; is the phase shift amount of beam scanning, e is the phase shifter 2
A phase distribution obtained by adding the phase distribution c that cancels the phase distribution of the input signals a to 2n and the beam scanning phase shift amount d, f
is the phase distribution obtained by digitizing e. a is the phase distribution of the input signal of the phase shifters 2a to 2n before being made into a step shape, which is expressed by the expression in brackets [ ] in equation (1), and b is a which is made into a step shape. , is the phase distribution expressing equation (1). The phase adjuster supports this phase distribution of b. c is a phase distribution that cancels the phase distribution of the input signals of the phase shifters 2a to 2n, and is the first term [α{i−(n+1/2)} ^2m ] in [ ] of equation (2) _.
is the phase distribution indicated by , where d is the phase shift amount of beam scanning and is expressed as
It shows βi in [ ] in (2). e is a distribution that is the sum of the phase distribution of c and the phase distribution of d, and represents the expression in [ ] in equation (2). f is the digitized portion of e and represents equation (2).
Therefore, the combination of curves f and b is element antenna 1a~
This is the phase distribution given to 1n.

As mentioned above, the electrical length of the power supply transmission line can be changed stepwise, so
This makes hardware implementation possible.

As a result of the above, the quantization phase error is By non-periodicizing, the side lobe level caused by quantization phase error is improved and good antenna performance can be obtained.

FIG. 6 shows another embodiment of the present invention, in which digital phase shifters 9a to 9n for phase adjustment are used as the phase adjusters 9a to 9n shown in FIG. 4, and the principle is the same as described above. It is similar to

FIG. 7 shows another embodiment of the present invention, which is a semi-fixed phase shifter 9a to 9n that can be manually adjusted and then fixed as the phase adjusters 9a to 9n shown in FIG.
9n was used. FIG. 8 is a diagram showing the amount of phase shift applied to each semi-fixed phase shifter. 8th
In the figure, 9a to 9n are semi-fixed phase shifters, φ ₀ to
φ ₃ indicates the amount of phase shift. As shown in FIG. 8, step-like phase shifts φ ₁ to _{φ 3} are given corresponding to the element position. Therefore, since each semi-fixed phase shifter is given a phase shift amount corresponding to its element position, the phase shift amount is changed and given to each block. Moreover, this principle is similar to that described above.

FIG. 9 shows another embodiment of this invention,
As the phase adjusters 9a to 9n shown in FIG. 4, fixed phase shifters that can fixedly provide different phase shifts by changing the electrical length are used in combination. The amount of phase shift applied to each fixed phase shifter is blocked in the same way as shown in FIG. 7, and this principle is the same as that described above. Further, this fixed phase shifter may be of any type as long as it can change the electrical length, for example, it may be one in which the length of a coaxial line or waveguide is changed.

That is, according to the present invention, side lobes due to quantization phase errors are dispersed and reduced from a specific direction, and large side lobes occurring in a specific direction can be reduced.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing a conventional electronic scanning antenna, Figure 2 is an explanation of the directional characteristics, Figure A is a diagram showing the amount of phase shift of each phase shifter, Figure B is a diagram showing the electronic scanning antenna. FIG. 3 is a diagram showing the quantization phase error in a conventional antenna, FIG. 4 is a schematic diagram showing an embodiment of the antenna according to the present invention, and FIG. 5 is a diagram showing the principle of the present invention. FIG. 6 is a schematic diagram showing one embodiment of the invention, FIG. 7 is a schematic diagram showing another embodiment of the invention, FIG. 8 is a diagram showing the amount of phase shift applied to the phase shifter, and FIG. FIG. 2 is a schematic diagram showing another embodiment of the present invention. 1a to 1n are element antennas, 2a to 2n are phase shifters, 3a to 3n are phase shifter drive circuits, 4a to 4n are power feeding transmission lines, 5 is a control circuit, 6 is a transmission/reception switch, 7 is a transmitter, 8 is a receiver, and 9a to 9n are phase adjusters. It should be noted that the same or corresponding parts in the figures are indicated by the same reference numerals.

Claims (1)

[Claims] 1. A plurality of element antennas, a plurality of phase shifters provided corresponding to each of the plurality of element antennas,
A phase shifter drive circuit provided corresponding to each of the plurality of phase shifters, and a control circuit that provides a control signal corresponding to the beam direction to the phase shifter drive circuit, and the control circuit is provided with a control signal that is sent from a transmitter. In an electronic scanning antenna in which the main beam direction is controlled by generating a phase shift of a predetermined amount in a microwave signal, the input signal phase of the phase shifter is set to [-α{i-(n+1/2)}.
^{2 m} ] As shown in _D , give it in a stepwise manner, adjust it with a phase adjuster, and use the adjusted phase to determine the phase shift amount of each phase shifter [[a{i-(n+1/2)} ^2m ] _D − βi ]
An electronic scanning antenna characterized in that side lobes caused by quantization phase errors during beam scanning are reduced by setting the value to _B. However, B and D are the minimum unit phase angle, α is an arbitrary constant, β is a constant corresponding to the beam scanning angle, n is the number of arrayed antenna elements, i is the arrangement number of the element antenna, m is a natural number, [X] _B and [X] _D is the digital phase amount quantized by B or D closest to X,
D is the step width of the staircase.