JPS58221501A - Dielectric transmission line of low loss - Google Patents

Abstract

PURPOSE:To realize the transmission of a low loss over a frequency range from a microwave through a light region, by providing concentrically inner and outer cylindrical dielectric matters via a space part and then specify the thickness of the inner and outer cylindrical dielectric matters and the width of the space part. CONSTITUTION:The inner and outer dielectric matters 1 and 3 are made of glass, etc., and air or other gas is filled into space parts 2 and 4. The thickness of dielectric matters 1 and 3 are set at t1 and t3 rspectively, and the width of the part 2 is set at t2. At the same time, transmission constants of radius directions of parts 1, 2 and 3 are set at K1, K2 and K3 respectively along with m1, m2 and m3 set as odd numbers respectively. Under such conditions, t1, t2 and t3 are set so as to satisfy K1t1=pim1/2, K2t2=pim2/2 and K3t3=pim3/2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dielectric transmission line that can realize low-loss transmission in a frequency range from microwaves to light.

An O guide is known as a typical dielectric transmission line used in the above frequency range. , 0 guide concentrates the transmission power in a large part of the cylindrical refractive index distribution, and the loss of the material of the cylindrical dielectric determines the transmission loss, so it is essentially impossible to achieve low-loss transmission. It can be said.

The present invention has been made based on the above two points, and an object of the present invention is to provide a dielectric transmission line that can realize low-loss transmission in a frequency range from microwave to optical.

That is, in the dielectric transmission line of the present invention, inner and outer cylindrical dielectrics are arranged concentrically with a space between them, and the thicknesses of the inner and outer cylindrical dielectrics and the width of the space are specified.

FIG. 1 shows an example of a dielectric transmission line of the present invention, in which 1 is an inner cylindrical dielectric, 2 is a space, 6 is an outer cylindrical dielectric, and 4 is an inner cylindrical dielectric 1. This is the internal space that is formed.

The inner and outer cylindrical dielectric bodies 1 and 6 are made of a material such as glass, and the space 2.4 is filled with air or other gas.

Here, the thickness 'f of the inner cylindrical dielectric 1 is t1, the width of the space 2 is t2, the thickness of the outer cylindrical dielectric 2 is t8, and the radial propagation in each part 1, 2.3 is 1 for each constant. 2. to 8, and ml + m! If l + m s are each an odd number, then K 1 t 1 = 10 m l K 12t 11 2 m 2 and t 8°! ” 8, low-loss transmission is possible.

The reason for this will be explained with reference to FIG.

FIG. 2 shows a multilayer dielectric plate placed in air.

Here, the dielectric constants △ of air 5 and dielectrics 6, 7.8
△ △ △ X respectively with ε 0. ε 1+! 9+ ε 8 direction propagation constant △ constant k respectively. I kll k'l+ kll, and the dimensions of each part are t. + tin t2+ tB.

X direction propagation constant K. , to 1. 2. The imaginary parts of all 8 are small, so if we ignore this and approximate it using real numbers, the following equation holds true.

kO'-ni♂=kI-KIL=ni, Shini Akira-kj-ni♂
=β2=toδ(1-t') (1)
ml Note that t=T- (m: odd number, λ: wavelength in air 5).

From equation (1), KO=kot At this time, K1 t1==T1711+ K2 t2 7
3t3”” 2 ” 8 (m1+ ” 'J
+ m8 is an odd number)" l + t2e・i
When 't3 is set, the attenuation constant α of the fundamental wave is given by the following equation.

Since t is very small, (Equation 4 can generally be approximated by the following equation.

Here, if the dielectric material 7 is replaced with air, ε=1, so the equation (4) can be expressed as the following equation.

That is, by replacing the dielectric 7 with air or a substance with a dielectric constant similar to air, loss can be reduced.

The transmission loss at λ=1o and 6 μm is calculated from equation (5) as follows.

When t = 0.4m, a = 1.14 x 10
−”dB/n1t, :0.2m+111 when α==
1.78x10-'aB/mt, when = 0.3cm, a = 1.55x10''d B/mt, when = 0.4m, a = 2.22x 10-sa B/m or more,
Although the present invention enables low-loss transmission, there is loss in the cylindrical dielectric 1, which generates heat. Therefore, as shown in FIG. 6, the inner and outer spaces 4,
2. It is preferable to circulate cooling air to suppress heat generation.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an example of the dielectric transmission line of the present invention, and FIG.
The figure is a slab guide of a multilayer dielectric plate for detailed explanation of the present invention, and FIG. 6 is an explanatory drawing of another example of the present invention. 1: Inner cylindrical dielectric, 2: Space, 6: Outer cylindrical dielectric.

Claims (1)

[Claims] 1. An outer cylindrical dielectric is arranged concentrically around the outer periphery of the inner cylindrical dielectric with a space therebetween, and the thickness of the inner and outer cylindrical dielectrics is t □ + tB; Further, when the width of the space is t2, t1. A low-loss dielectric transmission line characterized in that it is configured by setting tQ+ta. Here, k1+ K2+ KR are the radial propagation constants in the inner cylindrical dielectric, the space, and the outer cylindrical dielectric, and m
1+"2+"8 are odd numbers. 2. The low-loss dielectric according to claim 1, characterized in that a cooling medium is circulated in the internal space of the inner cylindrical dielectric and the space between the inner and outer cylindrical dielectrics. line.