JPS625537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna for high frequency energy;
In particular, it relates to antennas using planar arrays of slotted waveguides.

In the field of radar antennas for target detection and tracking systems in guided missiles, so-called resonant slot arrays are often used. In the past, for example, arrays have been formed over a predetermined aperture by mounting rectangular waveguides having a plurality of slots of approximately the same size in close proximity to each other. An electrical short circuit is formed at one end of each waveguide to create a resonant structure within which standing waves are created to optimize excitation of the slot. A cooperative feeding device of a configuration known per se is connected to the other end of the waveguide so that the resonant slot array can be operated as a transmitting or receiving antenna, such as a monopulse antenna, for example.

Generally, when using a resonant slot array antenna for a guided missile, the following is required.
(1) First, the horizontal pencil beam should be formed so that the antenna gain is maximized and the sidelobe level is kept as low as possible. (2) Second, the energy in the beam should be linearly polarized, and the effects of cross-polarization, that is, components in orthogonal directions, should be as small as possible. In order to achieve these things within the limited effective space within the cylindrical body of a guided missile, the opening of a typical slot array is circular, and the array itself is aligned with respect to the pitch (PITCH) and yaw (YAW) axes. The slots are mounted for controllable orientation such that the orientation of all slots relative to the longitudinal axis of the waveguide is constant. Furthermore, if the slot array is to be operated as a monopulse antenna, the number of waveguides and the arrangement of the slots are such that the same number of slots are disposed in each quadrant of the aperture. In addition, it is necessary to consider the suppression conditions for the grating globe and the slot array necessary to avoid a decrease in efficiency. That is, for a given operating frequency, proper attention must be paid to the waveguide dimensions, the spacing between slots, and the location of electrical short circuits in each waveguide. As a typical example,
The antenna aperture inside the guided missile is 5 inches.
If conventional techniques are used to design such an array, an X-band slot array can have up to 20 slots. Since the antenna gain of a slotted array directly corresponds to the number of slots, the antenna gain of the array is limited.

There are other problems with conventional slot arrays that use waveguides of the same size. Because the position of each waveguide slot (along the length of the waveguide) is fixed, it is difficult to obtain a symmetrical pencil beam. As a result, the performance of conventional slot arrays varies depending on the direction of the target from the aim.

In view of the above points, the first object of the present invention is to obtain a slot array in which the number of slots can be increased in the case of circular apertures compared to when this type of array is constructed using the prior art. .

Another object of the invention is to provide a slot array which incorporates a greater number of slots in a circular aperture than was hitherto conceivable and at the same time can be used as a monopulse antenna.

Still another object of the present invention is to provide an improved slot array in which the slot spacing is optimized to produce a symmetrical pencil beam.

The above and other objects of the present invention are to provide a resonant slot array having circular apertures in which a plurality of rectangular waveguides having slots of different dimensions are arranged in close proximity to each other to form said circular apertures. This can be achieved by spacing the slots and providing the necessary electrical short circuits within each waveguide depending on its chosen dimensions.

The figure shows waveguides 10u, 12u, 14u, 14l, 12l and 1 of a typical resonant slot array.
The arrangement of slots in the 0l is shown as a resonant slot array for use in the X-band in guided missiles, with the maximum allowable aperture 11 being circular with a diameter of 5 inches. Therefore, the ratio between the diameter of the aperture and the wavelength of the radiated energy of the antenna is approximately 5:1. waveguide 10
Since the slots in 1, 12l and 14l are arranged in the same manner as the slots in waveguides 10u, 12u and 14u, respectively, and the dimensions of like numbered waveguides are the same, the latter waveguide will be referred to below. Let me explain about the tube. Note that the thickness of each wall portion of each waveguide and the required power supply device, which is known per se, are not shown.

The width W14 (meaning the inner dimension of the wide wall of the rectangular waveguide) of the waveguide 14u is selected such that the cutoff frequency of the fundamental TE ₀₁ mode in this waveguide is near the reduced end of the X-band. has been done.
The thickness (not shown, but refers to the inner dimensions of the narrow walls of the rectangular waveguide) is such that the cutoff frequency of the next higher order mode (TH ₁₀ or TE ₂₀ mode) is higher than the highest frequency in the X-band. It has been selected to be. Here, we will use a normal rectangular waveguide for the X band (with internal dimensions of 0.900 [inch]
[inch]) is used.

The waveguide wavelength of the X-band energy in waveguide 14u is longer than the wavelength of the X-band energy in free space, and the slots must be spaced a distance determined by the waveguide wavelength. Even so, if you have an aperture of 5 inches in diameter and also have a shunt slot, you can insert 6 slots at half-wavelength intervals (measured in the waveguide along the axis 14 ua) and the last An electrical short circuit may be provided 1/4 wavelength away from the slots 14u, 3'.

Slots 14u, 3, 14u, 1 and 14u,
2' are spaced one wavelength apart along axis 14ua. Similarly, slots 14u, 2, 14
u, 1' and 14u, 3' are spaced apart from each other by one wavelength, and slots 14u, 3, 14u, 1
The interval from 14u and 2' is 1/2 wavelength. Furthermore, the slots 14u, 1 and 14u,
1' is equidistant from axis 14ua (along the unnumbered YAW axis), and slots 14u, 2 and 14u, 2' are equally spaced, and the last slot 14u , 3 and 1
4u and 3' are similarly spaced apart. Waveguide 14u
Each slot in the array constitutes a linear array in which the magnitude of the radiant energy varies gradually along the PITCH axis, which directs the beam generated by the wide portion of the array relative to the waveguide 14u. (meaning perpendicular to the plane defined by the PITCH and YAW axes)
has. Furthermore, the first side lobe (axis 14
(measured along ua) is determined by the degree to which the magnitude of the radiant energy is graded.

The width of the waveguide 12u is determined to be smaller than the width of the waveguide 14u. Therefore, the wavelength of the internal energy of the waveguide 12u is made larger than the wavelength of the waveguide 14u. As a result, slots 12u, 1, 12u, 2, 12u, 1', 12
The spacing between u, 2' (measured along axis 12ua) is greater than the spacing of the corresponding slots in waveguide 14u. Here, the energy is transferred to the waveguide 1 of the waveguide 12u.
When guided at the same end as 4u, an electrical short circuit (not shown) for the former is placed 1/4 wavelength from slot 12u, 2', where the corresponding ends of the two waveguides The direction of the electric field in each pair of slots is properly oriented along the YAW axis.

Each slot 12u, 1, 12u, 2, 12u,
The spacing of 1', 12u, and 2' (measured along the YAW axis) is determined to allow the magnitude of the radiated energy to be varied gradually along the YAW axis (excluding polarization effects). There is. That is, adjustments are made so that more energy is radiated from the element located at the center. Thus, each slot in waveguide 12u is spaced from axis 12ua by a distance greater than the distance of the corresponding slot in waveguide 14u from axis 14ua.

The waveguide 10u has at least two slots 1
0u,1 and 10u,1' are dimensioned to fit between the waveguide 12u and the line defining the maximum allowable aperture 11. Here, the width of the waveguide 10u is
It is 0.740 [inch]. Also, the wavelength of the energy in waveguide 10u is greater than the wavelength in waveguide 14u or 12u, and slots 10u, 1 and 1
0u, 1' are slots 12u, 1 and 12u,
1' or 14u, 1 and 14u, 1'. Further, the position of the electrical short circuit (not shown) near the slots 10u, 1' is determined by the wavelength of the energy in the waveguide 10u, and the direction of the electric field in the slots 10u, 1 and 10u, 1' is determined by the wavelength of the energy in the waveguide 10u. slots 14u, 1 and 14u, respectively;
1' is the same as the direction of the electric field.

Each waveguide 14u, 12u, 10
The amount of energy introduced into u, 14l, 12l, 10l is adjusted in a suitable manner in a combined power supply (not shown). 10 more slots
The position of u, 1, 10u, 1' (measured along the YAW axis) is varied to grade the radiant energy as desired, so that the beam shape along the YAW axis is optimized and the sidelobes is suppressed to a minimum value.

A slot antenna with a small circular aperture (meaning about 5 inches in diameter) is
When designed for bands, the design flexibility afforded by using waveguides of different widths is beneficial. That is, the relative positions of corresponding slots in different waveguides can be adjusted without changing the orientation of the slots, so that the antenna gain is maximum in the direction of the pencil beam with relatively small side lobes, and Does not affect polarization. In this regard, the length of each slot may be adjusted to change the phase distribution of the aperture. Using conventional knowledge about the effects caused by varying the length of the resonant slot, the phase distribution across the aperture can be adjusted in each case by routine experimental techniques. Thus, when the beam width measured along the YAW axis is the same as the beam width along the PITCH axis, as in the case of the present invention, the length of the slot can be adjusted by adjusting the phase distribution along these axes. can be modified to optimize. It will be understood by those skilled in the art that the present invention is not limited to the embodiments disclosed herein, and that various modifications can be made within the scope of the invention.

[Brief explanation of the drawing]

The figure is a plan view showing a linearly polarized slot array antenna according to the present invention. 10u, 10l, 12u, 12l, 14u, 1
4l... Waveguide, 11... Opening, 10u, 1, ~10
u, 1', 10l, 1~10l, 1', 12u, 1
~12u, 2', 12l, 1~12l, 2', 14
u, 1~14u, 3', 14l, 1~14l,
3'...Slot.

Claims (1)

[Claims] 1. A linearly polarized slot array antenna having a substantially circular aperture in which the ratio between the diameter of the aperture and the wavelength of radio frequency energy at the rated frequency of the antenna is approximately 5:1. (a) a first plurality of rectangular waveguide resonators sized to occupy half of the opening when juxtaposed with narrower walls, a first plurality of rectangular waveguide resonators, the width of the wider wall of the waveguide resonators decreasing outward from the center of the aperture; b) a second plurality of rectangular waveguide resonators similar to the first plurality of rectangular waveguide resonators occupying the other half of the aperture; and (c) each of the rectangular waveguides. a plurality of radiation slots formed in the wide wall of the type resonator;
The slots are parallel to each other with the center of each slot located within the maximum electric field of the corresponding rectangular waveguide resonator, and the distance of the slots from the center line of the resonator is adjusted toward each end of the resonator. A linearly polarized slot array antenna consisting of a radiating slot increasing according to .