JPH03141706A - Slot array antenna - Google Patents

Abstract

PURPOSE:To obtain high antenna efficiency by forming slot groups for which three slots making a prescribed angle to the advancing direction of radio waves are formed as one set, on the surface of a waveguide at the intervals of the guide wavelength of the waveguide. CONSTITUTION:On one magnetic field surface of a flat rectangular waveguide 10, a slot 1a is formed rectangularly to a straight line (a) along this straight line (a) rectangular to the advancing direction of the radio waves. A slot 1b is formed at 45 deg. to the advancing direction along a straight line (b) which is advanced by lambdag (guide wavelength of waveguide)/4 in the advancing direction from this straight line (a). A slot 1c is formed rectangularly to the slot 1b and at about 45 deg. to the advancing direction along a straight line (c) delayed from the straight line (a) by lambdag/4 in the advancing direction. The slot groups are formed with the slots 1a-1c as one pair and a lot of those slot pairs are formed at the intervals of about lambdag. Thus, in such a slot array antenna, the slot can be designed so that the effective area of the whole slot can be equal to an antenna opening surface, and the high efficiency can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a slot array antenna suitable for use as a broadcasting, communication antenna, etc.

[Conventional technology]

Conventionally, in a traveling wave type waveguide slot array antenna, the slots for generating circularly polarized waves are located at a certain point in the traveling direction and 45° in the traveling direction, as shown in Fig. 5.
While forming a slot x forming an angle of 90°, the slot A slot y is formed which is perpendicular to the slot y and forms an angle of 45 degrees with the traveling direction, and the composite wave emitted from the slot x and the slot Y rotates over time to generate a circularly polarized wave. It is known that pairs of slots consisting of and slot y are arranged at intervals of λ8 in the direction of travel, and also in a direction perpendicular to the direction of travel.

By the way, the length of the slot is usually about U/2 when the free space wavelength is λ, and if you try to form the slot pairs in a straight line, the interval between the slot pairs will be +5 in 45 degrees. )·2 = A, + is necessary, but in order to generate circularly polarized waves as described above, this interval is approximately λF1/4, so it must be G·λ × λg.

On the other hand, since λg is desirably set to 0.9λ or less in order to suppress grating lobes, the above inequality does not hold, and slots X and y intersect. For this reason, in the conventional slot array antenna described above, a method is used in which the two (slot x and thrower y) are moved in a direction perpendicular to the traveling direction to the extent that the phase difference between them (slot x and thrower y) is 90° and they do not intersect.

[Problem to be solved by the invention]

In this way, in the conventional slot array antenna as described above, the effective area of the slot is λ/4)・(λ/2〉
=^2/8 and assuming a shortening rate of 80%, the effective area of the entire slot excluding the area where this effective area overlaps is:
This is approximately 70% of the antenna aperture area. This means that there is a wasted S in terms of radiation efficiency for which no slot is formed in the direction of travel, and the antenna efficiency is at most 70
There is a problem that only % can be desired. Also,
In order to reduce this wasted area S, even if the shortening rate of the pipe wavelength is further reduced to shorten λg, the interval between the slot pairs λg will also become shorter, so the slot interval in the direction perpendicular to the direction of travel will decrease. There is also the problem that not only does this increase, but also the cost and loss of the slow wave circuit for reducing the shortening rate increase.

The present invention attempts to solve these problems, and aims to provide a slot array antenna in which slots are formed substantially uniformly over the antenna aperture and high antenna efficiency can be obtained.

[Means to solve the problem]

Therefore, in a traveling wave waveguide type slot array antenna, the slot array array is formed along the first straight line that is perpendicular to the direction of propagation of the radio wave, where λg is the internal wavelength of the waveguide. a first slot that is perpendicular to the traveling direction; and a second slot that is formed along a second straight line that extends approximately λg/4 in the traveling direction from the first straight line and makes an approximately 45° angle with the traveling direction. a second slot formed along a third straight line delayed by about λg/4 in the traveling direction from the first straight line, and making a right angle to the second slot and approximately 45° with the traveling direction; The waveguide is characterized in that a number of sets including the third slot and the third slot are formed on one surface of the waveguide at intervals of approximately λg.

[For production]

In the slot array antenna of the present invention described above, in the traveling wave type waveguide slot array antenna, the waveguide slot array antenna is formed along a straight line perpendicular to the traveling direction when the inner wavelength of the waveguide is λg. a first slot perpendicular to the direction; and approximately λg in the traveling direction from the first straight line.
A second slot is formed along a second straight line that is approximately 45° with respect to the traveling direction, and a third straight line is formed along a second straight line that is approximately λg/4 behind the first straight line in the traveling direction. A large number of slot groups including a third slot formed at right angles to the second slot and at an angle of about 45° to the traveling direction are arranged at intervals of about λg, so that the waveguide is When electric power travels through the tube, circularly polarized waves are radiated from these slots, and a slot array antenna can be obtained in which the slots are arranged almost uniformly over the antenna aperture.

“Examples” Below, examples of the present invention will be explained with reference to the drawings.
Figures 1 to 3c show a slot array antenna as a first embodiment of the present invention, and Figure 1 is a perspective view thereof, and Figure 2
The figure is a plan view of the slot part, Figures 3a, 3b, and 3c are explanatory diagrams of circularly polarized wave generation in the slot, and Figure 4 is a diagram of the slot part of the slot array antenna according to the second embodiment of the present invention. FIG. 5 is a plan view of a slot portion of a conventional slot array.

First, to explain the first embodiment of the present invention, as shown in the examples of FIGS. 1 and 2, the width of the magnetic interface is
is formed along the first straight line a perpendicular to the direction of propagation of the radio wave, on either one of the magnetic surfaces of the flat rectangular waveguide 10 with an electric surface width of about λg/4 and more than 4 times A second slot 1a is formed perpendicular to the traveling direction, and a second straight line is formed along a second straight line extending approximately λg/4 in the traveling direction from the first straight line a, making an angle of approximately 45° with the traveling direction. λg/4 in the traveling direction from the second slot 1b and the first straight line a.
A group of slots is formed including a third slot 1c that is formed along the delayed third straight line C and is perpendicular to the second slot 1b, and also makes an angle of about 45° to the traveling direction. . A large number of sets are formed at intervals of approximately λg (the interval between straight line a and straight line n is approximately λg). In this case, slots la, lb, 1. The length of c is selected to be 0.45λ.

Note that the slot length is generally around 0.5λ, but the optimum value is around this due to the slow wave factor, the presence of dielectric materials, etc.

Further, a horn-shaped waveguide 3 equipped with a radio wave lens 2 is connected to one opening of the rectangular waveguide l as a power feeding section, and the other opening can be used depending on the presence or absence of surplus power. An arbitrary terminating resistor 4 is provided. This terminating resistor can be aligned with the slot at the end, and the resistor can be omitted.

With the above configuration, when the horn-shaped waveguide 3 is excited in the TE mode in which the electric field component is perpendicular to the magnetic interface of the rectangular waveguide 1, the radio waves spread by the horn-shaped waveguide 3 are transmitted by the radio lens 2. A flat TE mode whose phase is compensated and whose wavefront is substantially parallel to the opening of the rectangular waveguide 1 is generated and propagates into the rectangular waveguide 1. T.E. The power supplied in the mode is gradually radiated to the outside space from the slots 1a to 1c arranged in a row on the magnetic surface of the rectangular waveguide 1, and if any power remains, it is consumed by the terminating resistor 4.

To explain in detail the radiation of power from the slots with reference to FIGS. 3a, 3b, and 3c, first, slots 1b and 1c are at right angles to the direction of propagation of radio waves, and slots 1b and 1c are at 45 degrees. For the same length, the ratio of the electromagnetic field inside the rectangular waveguide 1 coupled to the slot is approximately 1.
:1/ri, and the surface current 5 in the figure flows in the direction indicated by the arrow, and has a sine distribution with the largest value at the center of the arrow. Next, the pattern of the surface current at a certain time t and the electric field component of the power radiated from the slot in that case are as shown in Figure 3a, but the value of the surface current flowing through the point of slot 1b is the largest; If G is 1, an electric field of magnitude G is generated from slot 1b in the direction of 45°, and an electric field of magnitude G is generated from slot 1c in the direction of 135°. At this time, no current flows at the point of the slot 1a and no electric field is generated. Therefore, slot 1 a, 1
The combined electric field 6 radiated from b, 1 c becomes an electric field of magnitude 1 in the 90° direction. Next, assuming that one cycle is T, the pattern of the surface current at time t+T/8 and the electric field component of the power radiated from the slot in that case are in the direction of 180° from the slot 1a, as shown in Figure 3b. An electric field of magnitude 1/(", magnitude 1/2 in the direction of 45° from slot lb, and magnitude 1/2 in the direction of 135@ from slot 1c is generated, and the resultant electric field 6 is 135 It has a magnitude l in the direction of °.Next, the pattern of the surface current at time t+-T/4 and the electric field component of the power radiated from the slot in that case are as shown in Fig. 3c, from the slot 1a. An electric field having a magnitude of 1 is generated in the 180° direction, no electric field is generated from the slots 1 b and 1 c, and the composite electric field 6 has a magnitude of 1 in the 180° direction.

In this way, the combined electric field rotates once in time T, generating circularly polarized waves.

Although the explanation has been made here in terms of time, the same thing can be said if the explanation is made in terms of the phase in which the traveling wave excites the slot.

As described above, in this embodiment, the rectangular waveguide 10 is flat, and radio waves propagate in TE and 0 modes, and surface currents flow in the same direction and period, although the magnitude is different in the direction perpendicular to the direction of travel. Therefore, slots la, lb, lc in this direction
By arranging them, in-phase circularly polarized waves can be emitted. Regarding the traveling direction, if the slots 181b and 181e are set as one set and a large number of sets are arranged at intervals of λg, circularly polarized waves having the same phase can of course be emitted.

Next, to explain the tube wavelength λg, if the tube wavelength when no slot is provided is λg', the width of the magnetic interface of the rectangular waveguide 10 in the above embodiment is very wide (the width of the flat waveguide is Therefore, λg' is almost equal to λ.Furthermore, since the slot length is 0.45λ, the actance component of the radiation impedance of the slot becomes inductive and has the effect of delaying the phase. Therefore, λg<λ
Therefore, grating lobes can be suppressed without providing a slow wave circuit.

By the way, in the above embodiment, there are three slots 1a,
1b and 1c are arranged vertically and horizontally as one internal wave generating element, but in this pattern, the interval between slots 1a in the direction perpendicular to the traveling direction is
must be greater than or equal to the length of slot 1 b, 1
It is not possible to increase the density of c.

However, in the slot array antenna of the present invention, these slots do not necessarily have to correspond in a 1:1:1 ratio, and as shown in FIG.

1c may be formed densely and the length of the slot may be appropriately selected so that the combined electric field radiated from these is balanced with the electric field radiated from the slot 1a.

Further, the delay or advance of the phase due to the slot actance component varies depending on the angle, length, etc., but in this case, the interval between each slot in the advancing direction may be adjusted.

Furthermore, although a horn-type waveguide was used as the power supply to the rectangular waveguide 10 in the above embodiment, any other power supply that can excite a substantially plane wave may be used. Although the experiment is performed using a flat waveguide, similar effects can be obtained using a general waveguide.

As described above, the slot array antenna as an embodiment of the present invention can be designed so that the effective area of the entire slot with respect to the antenna aperture surface is equal, so that a highly efficient slot array antenna can be obtained.

Also, the width of the magnetic interface ■ is such that the tube wavelength λg' without slots is almost equal to the free space wavelength λ.
Since it uses a rectangular waveguide 10 which is much longer than the resonant length, that is, a slot with a dielectric reactance shorter than the resonance length, λg is reduced, and a slow wave circuit is not required, simplifying the structure and reducing costs. The transformation is measured.

Incidentally, even in an antenna in which rectangular waveguides of a conventional size are arranged in a row, the same effect can be obtained by forming slots in the same pattern.

〔Effect of the invention〕

As described above, according to the slot array antenna of the present invention, the slots can be designed so that the effective area of the entire slot with respect to the antenna aperture surface is equal, and a highly efficient slot array antenna can be obtained.

[Brief explanation of the drawing]

Figures 1 to 30 show a slot array antenna as a first embodiment of the present invention; Figure 1 is a perspective view thereof, Figure 2 is a plan view of the slot portion thereof, and Figures 3a, 3b, and 3c. is an explanatory diagram of internal wave generation in the slot, FIG. 4 is a plan view of the slot portion of the slot array antenna according to the second embodiment of the present invention, and FIG. 5 is a plan view of the slot portion of the conventional slot array. FIG. la, lb, lc...slot, 2...radio wave lens, 3...horn type waveguide, 4...terminal resistor, 5...
...Surface current, 6...Synthetic electric field, 10...Rectangular waveguide.

Claims (1)

[Claims] In a traveling wave waveguide slot array antenna, when the wavelength in the waveguide is λg, the antenna is formed along a first straight line that is perpendicular to the direction of propagation of radio waves and is perpendicular to the direction of propagation. a second slot formed along a second straight line extending approximately λg/4 in the traveling direction from the first straight line and forming an angle of approximately 45° with the traveling direction; a set of third slots formed along a third straight line delayed by about λg/4 in the traveling direction from the straight line, making a right angle to the second slot and making an angle of about 45° with the traveling direction; A slot array antenna characterized in that a large number of sets are formed on one surface of a waveguide at intervals of about λg.