JPH0356004B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic scanning antenna with 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 adjusts the phase shift amounts of the phase shifters 2a to 2n according to the arrangement order of the phase shifters 2a to 2n, as shown in FIG. Like A, linear functional change (dotted line)
The beam direction θ is controlled as shown in FIG. 2B.

Conventionally, in this type of antenna, when scanning the beam, an electronic computer was used to calculate B=2π/2 ^P (P
Digital phase changes are performed using the phase angle (=number of bits) as the minimum unit, but each antenna element has a phase error (quantized phase error) in the range of ±B/2 as shown in Figure 3. arise, and for this reason,
A drawback of electronic scanning antennas is that large side lobes occur in specific directions in the radiation pattern.

In order to eliminate the above-mentioned conventional drawbacks, the electronic scanning antenna according to the present invention changes the feeding phase so as to disperse the quantization phase error that causes large side lobes in a particular direction.

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, 5 is a control circuit, 6 is a transmission/reception switch, 7 is a transmitter, 8 is a receiver, and 9a to 9n are supplied via space. A wave receiving element antenna 10 is a waveguide slot array antenna which has approximately the same size as the entire element antenna group constituting the array antenna 11. It has a structure with multiple slots cut in it. This waveguide slot array antenna 10
is a power distribution primary radiator that distributes and supplies power to the array antenna 11 through space. That is, the radiation power from the waveguide slot array antenna 10 is received by each of the wave receiving element antennas 9a to 9n of the array antenna 11, and the radiation power is received by the phase shifter 2.
It passes through a to 2n and is radiated into space again from each element antenna 1a to 1n. Also, 12
is a radio wave absorber for absorbing power that is not irradiated to the array antenna 11 and eliminating unnecessary reflections.

FIG. 5 is a front view of the waveguide slot array antenna 10. This waveguide slot array antenna 10 is of a standing wave feeding type in which the terminal end is short-circuited with a metal plate 15. , slots 13 are cut in the broad face of the rectangular waveguide at intervals of λg/2 (λg is the internal wavelength of the waveguide).

In this device, the i-th element antenna 1i
The phase of the input signal of the phase shifter 2i is adjusted using the waveguide slot array antenna 10, for example, using the phase of the transmitter output end as a reference, as shown in equation (1).

-α{i-(n+1/2)} ^2m ...(1) However, α is an arbitrary constant, i=1, 2,...n, m
are natural numbers (1, 2,...).

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

As a result, the radiation pattern E(θ) of the entire electronic scanning antenna is determined by the antenna element spacing being x,
The propagation constant is expressed by Equation (4), where k is the propagation constant, and the main lobe direction where Equation (4) is maximum is expressed by Equation (5).

However, Ii is the excitation amplitude of the i-th element antenna, D=[α{i-(n+1/2)} ^2m -βi] _B - [α{i-(n+1/2)} ^2m -βi].

θ=sin ^-1 (β/kx) ...(5) Furthermore, D listed in equation (4) = [α{i-(n+1/2)} ^2m -βi] _B −[α{i-(n+1/ 2)} ^2m - βi] is the quantization phase error caused by the discontinuity of the phase shifter (if B is 0, D is also 0), but as shown in Figure 6, it is the quantization phase error caused by the discontinuity of the phase shifter. Unlike this, it becomes a curved line, and the slope and direction are distributed to the left and right. That is,
Side lobes due to quantization phase errors are dispersed from a specific direction and become smaller, making it possible to reduce large side lobes occurring in a specific direction.

FIG. 7A shows the center line 1 of the waveguide in slot 13.
It is the excitation amplitude for the deviation amount d from 4, and the seventh
Diagram B shows the excitation phase versus slot length l.
That is, the excitation amplitude expressed by equation (4) can be realized by adjusting the deviation amount d of the slot 13, and the excitation phase expressed by equation (1) can be realized by adjusting the slot length l.
This can be achieved by adjusting. First, when the excitation phase is leading, the slot susceptance is positive, and conversely, when the excitation phase is lagging, the slot susceptance is negative, making use of the fact that the phase amount and the slot susceptance are proportional. While making the excitation phase distribution expressed by equation (1),
The slot length l is selected so that the sum of the susceptances of each slot becomes 0. Next, by utilizing the fact that the excitation amplitude is proportional to the size of the slot conductance, the amount of deviation d is selected so that the excitation amplitude distribution becomes the required distribution and the sum of the conductances of each slot becomes 1. do. As described above, the amount of deviation d of each slot of the slot array antenna 10
By selecting and the slot length l, the input admittance of the slot array antenna 10 becomes 1 of the conductance component, and matching can be achieved. That is, an array antenna with arbitrary excitation amplitude and phase distribution can be constructed without deteriorating the input standing wave ratio of the slot array antenna 10. Therefore, in FIG. 4, by selecting the distance L between the waveguide slot array antenna 10 and the array antenna 11, power is received on the array antenna 11 side according to the excitation amplitude and phase distribution. According to numerical and experimental studies, this optimal distance is achieved at 3λ or less, where λ is the wavelength of the radio waves used.

Furthermore, according to the embodiment of the present invention, the antenna for distributing power is configured with a series-fed array antenna consisting of a plurality of radiating elements, so the configuration can be significantly simplified, and the antenna for distributing power can be significantly simplified. Efficient power distribution can be achieved by making the array antenna approximately the same size.

Although the present invention has been described with respect to the case where the elements are arranged in a straight line, it goes without saying that it can be similarly applied to the case where the elements are arranged in a planar manner. Also,
In the embodiment, a case has been described in which a standing wave feeding type waveguide slot array antenna using a rectangular waveguide is used. It can be implemented using a slot array antenna, a slot array antenna with a slot cut in the narrow face of a rectangular waveguide, a circular waveguide slot array antenna, or a coaxial cable. It can also be implemented using a slot array antenna in which slots are cut in the outer conductor.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing a conventional electronic scanning antenna, and Figure 2 explains its directional characteristics. 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 present invention, and FIG. 5 is a waveguide slot array used in the present invention. 6 is a diagram showing the quantization phase error in the antenna of the present invention; FIG. 7 is a diagram explaining the excitation amplitude phase characteristics of the slot; FIG. 6A is a diagram showing the excitation amplitude; FIG. is a diagram showing excitation phases, 1a to 1n are element antennas, 2a to 2n are phase shifters, 3a to 3n are phase shifter drive circuits, 5 is a control circuit, 6 is a transmission/reception switching circuit, 7 is a transmitter, 8 is a receiver, 9a to 9n are wave receiving element antennas, 10 is a waveguide slot array antenna, 11 is an array antenna, and 12 is a radio wave absorber. 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 in each of the plurality of element antennas, a phase shifter drive circuit provided in each of the plurality of phase shifters, and the above phase shifter. The transmitter is equipped with a control circuit that provides a control signal corresponding to the beam direction to the transmitter drive circuit, and a series-fed slot array antenna consisting of multiple radiating elements is used as an antenna to distribute power to each element antenna. In an electronic scanning antenna in which the main beam direction is controlled by producing a required amount of phase deviation in the microwave signal sent from the microwave signal, the above-mentioned Set the phase shift amount of the phase shifter to a value of [α{i−(n+1/2)} ^2m −βi] _B , and set the input signal phase shift of each phase shifter to −α{i−
(n+1/2)} ^2m , the slot length l was selected so that the sum of the susceptances of the slots arranged at intervals of 1/2 of the tube wavelength, which is proportional to the excitation phase, was 0. An electronic scanning antenna characterized in that a series-fed waveguide or coaxial tube slot array antenna of a continuous wave feeding or traveling wave feeding type is used in opposition to the electronic scanning antenna at a distance of three wavelengths or less. However, B is 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 array number of the element antenna, m is a natural number, [X] _B is the digital phase amount quantized with B closest to X.