JPH057882B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency demultiplexing device using a frequency selective surface plate for demultiplexing electromagnetic waves.

In general, frequency-selective surface plates used as splitters for high-frequency waves propagating in space have low loss over a wide range of predetermined frequencies, and have little difference in characteristics depending on the plane of polarization when high-frequency waves are incident obliquely. required.

Conventionally, as a frequency-selective surface plate, a plurality of rectangular grids 1 each having a vertical strip 3 and a horizontal strip 4 of different widths and made of conductors are combined so that a window 2 is formed as shown in FIG. There is a duplexer configured as shown in FIG. 2 (Japanese Patent Application No. 56-017831 (Japanese Unexamined Patent Publication No. 57-132401)).
When the frequency selection plate constituting such a duplexer is used at an oblique incidence (incidence angle of 20°) as shown in Fig. 3, when the TE incident wave (the incident electric field E is
(perpendicular to the plane of the figure) and TM incident wave (when the incident electric field E is perpendicular to the incident electric field E and the traveling direction of the TE incident wave)
When used as a duplexer, there is a dip point 15 where the transmittance sharply decreases in the frequency characteristics for the TM incident wave, as shown in the characteristic diagrams in Figures 4a and b. , this becomes a constraint on usage, such as limiting the band. As a specific example of this, FIG. 5 shows an example of the characteristics of a duplexer using three rectangular gratings of two types shown in FIGS. 4a and 4b. This data shows that the dip point 15 of a single rectangular grid also appears when it is composed of three pieces,
This has the disadvantage that the passband of the TM incident wave is limited. Such drawbacks cannot be sufficiently improved only by selecting the dimensions of the rectangular grid.

The occurrence of such dips can be explained as follows. That is, normally the current flowing on the metal surface of the grating flows parallel to the strips of the grating, but in the case of a TM incident wave, there is a current that flows around the intersections of the grating, as shown in FIG. This current causes resonance, and this resonance is the cause of the appearance of dip points. Note that the wavelength λ _d1 at the time of resonance is determined from the condition that the length of this current element is equal to 1/2 of the wavelength. The length of this current element is more than a/2+b/2 than the geometric dimension of the grid.
It is clear that dx/2+dy/2 or less.
Therefore, the resonant wavelength λ _d1 is a+b≦λ _d1 ≦dx+dy (1).

The purpose of the present invention is to shift the arrangement of the windows of the rectangular lattice by about half the lattice dimension between adjacent rows, thereby moving the frequency of the dip point of the TM incident wave to a higher frequency band and widening the frequency transmission band. The object of the present invention is to provide a high frequency demultiplexing device that can perform

The present invention will be explained in detail below with reference to the drawings.

FIG. 7 is a plan view of a rectangular array used in an embodiment of the invention. This rectangular array (pattern) is
The windows 2 made up of rectangular grids 6 of conductors are arranged in a brick arrangement with adjacent rows shifted by 1/2 period in the x-axis direction. With such a rectangular array, the position of the dip point relative to the TM incident wave can be adjusted. That is, in the rectangular arrangement according to the present invention, the bending current flowing from the horizontal strip to the vertical strip is as shown in FIG. The length of this current element is a/2+b/2-
Since it is greater than or equal to dx/4 and less than or equal to dx/4+dy/2, the wavelength λ _d2 of the dip point (abnormal resonance point) is a+b−dx/2≦λ _d2 ≦dx/2+dy (2). Equation (2) is the abnormal resonant wavelength λ _d1 of the conventional grating.
shorter than Therefore, the dip point 15 for the TM incident wave moves toward higher frequencies and can be removed out of the band.

An embodiment of the present invention is shown in FIGS. 9a to 9c.

By constructing a duplexer by combining three rectangular gratings C and D having the characteristics shown in FIGS. 9a and 9b in the order of C-D-C from the incident direction,
The characteristics are shown in . When compared with the conventional characteristic shown in Fig. 5, this characteristic shows the dip point 15 of the TM incident wave.
moves to a higher frequency band, and the passing frequency band becomes wider accordingly.

In the above explanation, we have explained a rectangular lattice with rectangular windows made in a thin metal plate, but the same idea can be applied to a complementary lattice shape as shown in Fig. 10, in which the metal part and the space part of this rectangular lattice are replaced. is applicable. That is, due to the principle of complementarity of electromagnetic fields, the characteristics of the grating become the transmission characteristics and reflection characteristics of the original grating replaced.

As explained above, if the frequency selective face plate according to the present invention is used, the dip point can be moved to a higher frequency band by displacing the array of rectangular windows or rectangular metal pieces on the face plate between adjacent rows. This makes it possible to improve the transmission characteristics.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a conventional rectangular grating, FIG. 2 is a side view of three stacked rectangular gratings in FIG.
Figures 4a and b are frequency characteristic diagrams of Figure 3, Figure 5 is a characteristic diagram of a duplexer using multiple gratings of Figure 1, and Figure 6 explains the abnormal resonance of a conventional rectangular grating. figure,
FIG. 7 is a plan view of a rectangular grid used in an embodiment of the present invention, FIG. 8 is a diagram illustrating the current flowing on the metal surface in FIG. 7, and FIGS. FIG. 10, which is a diagram showing an example of the characteristics, is a plan view showing another embodiment of the present invention. 1... Rectangular grid, 2... Window, 6... Rectangular grid,
10...incident wave, 11...transmitted wave, 12...reflected wave, 15...dip point.

Claims (1)

[Scope of Claims] 1. A plurality of frequency-selective surface plates each having a rectangular periodic pattern formed of thin metal plates, each of the plurality of frequency-selective surface plates having an inductance component and a capacitance component due to the pattern. High frequency TM incident wave and TE
the plurality of frequency selectivity tables such that the resonant frequency and Q of each of the plurality of frequency selective surface plates are substantially the same for each of the polarized waves; A high frequency demultiplexing device characterized in that the periodicity and pattern dimension of each pattern of the face plate are determined, and further the adjacent periodic patterns of each of the plurality of frequency selective face plates are displaced by about half the grating dimension. .