JPS5821848B2 - antenna - Google Patents

Description

Detailed Description of the Invention The present invention relates to a power feeding method for a top-loaded antenna. For example, by feeding power from two points on the top-loaded portion of a top-loaded slot antenna with equal amplitudes and opposite phases, the feeder can be connected with low loss. The purpose of this is to match the radiated electromagnetic field and remove unnecessary polarization components of the radiated electromagnetic field.

In a conventional slot antenna, when power is fed at the center of the slot, the input resistance is very large compared to the characteristic impedance of the feed line, so in order to achieve impedance matching with the feed line, a portion shifted from the center is used to reduce the impedance at the feeding point. A method is used in which a power feeding point is provided at

In the case of a top-loaded slot antenna, there are cases where it is not possible to find a feed point position on the slot other than the top-loaded portion to set the feed point impedance to a value appropriate for matching the characteristic impedance of the feed line.

Other methods of matching a top-loaded slot antenna with a feed line include making the entire slot a folded slot or feeding power from the center and connecting a matching circuit, but in the former case the structure of the antenna is complicated. In the latter case, losses occur in the matching circuit, reducing the gain of the antenna.

The present invention solves the above-mentioned drawbacks, and provides a top-loaded slot antenna that has a simple structure, has an input impedance that matches the feed line, does not radiate unnecessary polarization components, and has low loss.

An embodiment of the invention will be explained with reference to FIGS. 1, 2, and 3.

FIG. 1 shows an embodiment of a two-point feeding type partially loaded slot antenna according to the present invention. This is an antenna fed in phase.

In the figure, 1 is the main plate, 2 is a straight slot excluding the top loading part, 3 and 4 are slots for top loading, 5a, 5
b is the center point, 6a, 6b and 7a, 7b are the feeding points, 8
, 9 indicate power supply lines.

And these feeding points 6a and 7a and feeding points 6b and 7
b is symmetrical with respect to the central axis of the straight slot 2.

FIG. 2 is a diagram showing the voltage distribution along the slot 1 of FIG. 1 and the direction of the electric field on the slot.

In the figure, X and y are the coordinate axes along the slot, A and A are the voltage distribution curves along the slot, and ■1 (X), ■2 (y)
It is expressed as

The positions of the feed points are y=h and y=-h, and A is an arrow indicating the direction of the electric field on the slot.

Top-loading portion 3 of the top-loading slot antenna of FIG.
, 4, the input impedance at the center points 5a, 5b can be made to resonate, and the value of the resonance is defined as Zl.

If power is supplied simultaneously from feed points 6a, 6b and 7a, 7b with equal amplitude and in opposite phases to each other, and the input impedance at 6a, 6b is Z2, Z2 is expressed by the following equation from the voltage distribution curve A in Fig. 2. .

The characteristic impedance of the feeder line 8 is Z.

shall be. By changing the feed point positions 6a and 6b, Z2=Z
By determining the value of (2V2(ω/v1(o))2 that is 0, impedance matching with the feeder line 8 can be obtained without causing loss.

Impedance matching with the feed line can be obtained in exactly the same manner for the input impedance at the feed points 7a and 7b.

Further, on the top loading slot 3.degree.4, the electric field has equal amplitude and opposite phase at corresponding points above and below, so no horizontally polarized radio waves are radiated.

Therefore, the radio waves radiated from the top-loaded slot antenna fed from these two vertically symmetrical points are only vertically polarized waves.

The above description has been made based on the case where the antenna shown in FIG. 1 is used as a transmitting antenna, but similar operation can be obtained using the reversibility theorem even when it is used as a receiving antenna.

Figures 3a and 3b show another embodiment of the antenna of the present invention, which is a recessed antenna in which a cavity is attached to the rear of the two-point-fed top-loaded slot antenna of Figure 1 so that the antenna radiates only in one direction. be.

Figure 3a is a front view of this antenna, Figure 3 is a side view, 1 is the main plate, 2 is the slot excluding the top loading part, 3゜4
indicates a slot as top loading, 8 and 9 a feeder line, and 10 a cavity.

This antenna also allows impedance matching with the feed line based on the same principle as the antenna shown in FIG.

In the above embodiment, the power feeding points of the top-loaded slot antenna were set at two points at symmetrical positions, but the same procedure can be applied when multiple sets of two points symmetrical with respect to the central axis of the slot are provided and power is fed from these positions. Can be implemented.

As explained above, according to the present invention, it is possible to easily obtain impedance matching with a feed line with low loss in a top-loaded antenna, and also to prevent radiation of unnecessary polarization components. This is extremely effective as a power supply method.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an antenna showing one embodiment of the top loading slot antenna of the present invention, Fig. 2 is an explanatory diagram showing the principle of the invention, and Fig. 3a shows another embodiment of the invention. FIG. 3 is a side view of FIG. 3a, which is a block diagram of the antenna. In the figure, 1 is the main plate, 2 is the slot excluding the top loading part, 3 and 4 are the slots for top loading, 5a, 5b are the center points, 6a, 6b and 7a, 7b are the feeding points, 8゜9 is the feeding line , 10 is a cavity. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a slot-type top-loading antenna. a linear slot, first and second slot-type top loadings connected to opposite ends of the linear slot and symmetrical about a central axis of the linear slot, and at least one of the first and second top loadings; A top-loaded antenna characterized in that, on the one hand, power is fed from two points symmetrical about the central axis;