JPH0583012A - Circular waveguide-coaxial line converter - Google Patents

Abstract

PURPOSE:To facilitate the manufacture of a converter by bonding a coaxial line to a circular waveguide coaxially in the converter converting an electromagnetic wave transmitted through the circular waveguide in a TE11 mode into an electromagnetic wave through the coaxial line in a TEM mode. CONSTITUTION:The coaxial line 12 is bonded coaxially to the circular waveguide 10 through which the electromagnetic wave in the TE 11, and a shielding plate 13 shielding a half of a diameter of an in-guide cross section of a coaxial line outer conductor 12b perpendicular to the electric field in the TE11 mode is bonded to the center conductor 12a of the coaxial 12. Moreover, the inner diameter of the outer conductor 12b is selected so that the interrupting frequency is higher than the frequency of the electromagnetic wave to be transmitted in the TE11 mode of the coaxial line 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a converter for connecting coaxial lines to circular waveguides for transmitting TE11 mode electromagnetic waves so that their central axes coincide with each other, and for propagating them as TEM mode electromagnetic waves in the coaxial lines. Regarding

[0002]

2. Description of the Related Art As shown in FIG. 6, one end of a circular waveguide 20 for transmitting an electromagnetic wave of TE11 mode is terminated (21), and an odd quarter wavelength of the electromagnetic wave is placed on the opening side from the end face. A coaxial line 22 that is orthogonal to the central axis of the circular waveguide 20 at the double position
To join. The central conductor 23 of the coaxial line 22 is extendedly inserted into the circular waveguide 20 and is coupled with an electric field of TE11 mode parallel to the central conductor 23, so that the electromagnetic wave of TE11 mode of the circular waveguide 20 is coaxial. The line 23 was converted to electromagnetic waves in TEM mode.

[0003]

It is not easy to manufacture a structure in which cylindrical pipes whose central axes are orthogonal to each other are accurately joined.
High-precision machining requires complicated machining procedures, resulting in poor productivity and high cost. The present invention provides a means for making a transducer easy to manufacture by coaxially joining a circular waveguide that transmits TE11 mode electromagnetic waves and a coaxial line that transmits TEM mode electromagnetic waves.

[0004]

[MEANS FOR SOLVING THE PROBLEMS] At one end of a circular waveguide for transmitting an electromagnetic wave of TE11 mode, a coaxial line having a pipe inner diameter and a central conductor diameter having a cutoff frequency higher than the frequency of the electromagnetic wave is provided with their central axes. They are aligned and joined together, and a shield plate that shields half of the inner cross section of the pipe up to the plane including the diameter perpendicular to the electric field of the TE11 mode is adhered to the center conductor of the same coaxial line near the joint surface.

[0005]

The TE11 mode electric field distribution in the circular waveguide 10 is antisymmetric with respect to the central axis of the circular waveguide 10 as shown in FIG. 2 (a), while the TEM mode electric field distribution of the coaxial line 12 is obtained. As shown in FIG. 7C, they are distributed symmetrically with respect to the central axis of the coaxial line 12. TE of the inner cross section of the circular waveguide 10
One of the electric field distributions of the space divided by the diameter perpendicular to the 11-mode electric field is similar to the TEM mode electric field distribution of the coaxial line 12, and the other electric field distribution has an electric field direction opposite to that of the same TEM mode. ing.

Therefore, the TE of the inner cross section of the circular waveguide 10 is
By shielding half of the electric field divided by the diameter perpendicular to the 11-mode electric field, the TE11 mode electromagnetic wave of the circular waveguide 10 is coaxially bonded to the circular waveguide 10 as shown in FIG. 2 (b). It can be propagated as electromagnetic waves in the TEM mode to the coaxial line 12 thus formed. However, the TE of the coaxial line 12
If the cutoff frequency for the 11-mode electromagnetic wave is lower than the frequency of the transmitted electromagnetic wave, on the same coaxial line 12 side of the shielding plate 13, there is an electric field on the non-shielded side via the central conductor 12a of the same coaxial line 12. Electric fields in the same direction and / or electric fields in the opposite direction are generated.

Generally, when the radius of the circular waveguide is R1 (mm), the cutoff frequency F1 (GHz) of the circular waveguide for the TE11 mode electromagnetic wave is expressed as F1 ≈ 300 / (3.412 × R1), and F1 Transmits electromagnetic waves with a frequency higher than (GHz). Therefore, the inner radius r1 (mm) of the circular waveguide 10 is
Cutoff frequency f1 lower than the transmitted electromagnetic wave frequency F0 (GHz)
(GHz) In other words, F0> f1≈300 / (3.412 × r1) Therefore, r1≈300 / (3.412 × f1)> 300 / (3.412 × F0) (1) Reduce transmission loss. Inner radius r1 of the circular waveguide 10
The upper limit of is set to a small value within a range satisfying the above-mentioned cutoff frequency so as to suppress generation of an electric field distribution of an unnecessary mode in the circular waveguide 10.

The radius of the outer conductor of the coaxial line is set to R2.
(mm) and the radius of the central conductor is R3 (mm), the cutoff frequency F2 (GHz) for the TE11 mode electromagnetic wave of the same coaxial line
Is expressed as F2≅300 / π (R2 + R3), but there is no cutoff frequency for TEM mode electromagnetic waves on the same coaxial line, and electromagnetic waves of all frequencies are transmitted. Therefore, the cutoff frequency f2 is higher than the frequency F0 (GHz) of the electromagnetic wave propagating in the coaxial line 12 in the TE11 mode.
(GHz) so that the outer conductor inside radius r2 of the coaxial line 12 becomes
(mm) and the center conductor radius r3 (mm).

That is, F0 <f2 ≈ 300 / π × (r2 + r3) to r2 + r3 ≈ 300 / (π × f2) <300 / (π × F0) (2) and the inner conductor radius r2 and the center conductor radius r3 (m
Select the coaxial line of m) and transmit the frequency of the electromagnetic wave F0 (GH
z), the cutoff frequency f2 (GHz) for the TE11 mode electromagnetic wave of the coaxial line 12 is increased to TE11.
The transmission loss of the electromagnetic waves of the mode is increased to suppress the generation of the electric field distribution of the same mode, and only the electromagnetic waves of the TEM mode are transmitted.

[0010]

EXAMPLE An example of the present invention will be described with reference to FIG.
A coaxial waveguide 12 is coaxially joined to one end of a circular waveguide 10 that transmits TE11 mode electromagnetic waves, with their central axes aligned with each other. Inner tube radius r2 of the outer conductor 12b of the coaxial line 12
And the radius r3 of the center conductor satisfy the condition expressed by the equation (2), and the lower limits of the outer conductor and center conductor radii r2, r3 of the coaxial line 12 increase as the outer conductor and the center conductor become thinner. In order to reduce the transmission loss of the electromagnetic wave to be generated, it is set to a large value within the range where the cutoff frequency is satisfied. The ratio of the inner conductor radius r2 to the center conductor radius r3 is determined by the characteristic impedance of the coaxial line 12.

If there is a gap at the joint surface between the circular waveguide 10 and the coaxial line 12 due to the difference in the inner diameter of the circular waveguide 10 and the outer diameter of the coaxial line 12, both outer conductors are electrically connected. It is sealed by a ring-shaped metal plate 11 connected to. On the joint surface of the circular waveguide 10 and the coaxial line 12, a shield plate 13 made of a semicircular metal that shields half of the cross section of the circular waveguide 10 is provided, and the linear portion of the shield plate 13 has the same circular shape. TE11 in the waveguide 10
The shield plate 13 is arranged so as to be perpendicular to the mode electric field, and the shield plate 13 is bonded to the tip of the central conductor 12a of the coaxial line 12 extending to the joint surface. The position of the shield plate 13 is near the joint surface of the circular waveguide 10 and the coaxial line 12, that is, the gap between the joint surface and the shield plate 13 is an electromagnetic wave wavelength transmitted in the opening direction of the circular waveguide 10. Less than 1/2 of the center conductor within the same range 12
Anything that interferes with the induction of the same electromagnetic wave may be used.

An extreme change in the inner diameter at the junction of the circular waveguide 10 and the coaxial line 12 is accompanied by a loss of electromagnetic waves to be transmitted. Therefore, as shown in FIG. It is also possible to connect the lines coaxially. That is, to explain with the example shown in FIG. 3, the intermediate coaxial line 14 is joined coaxially with the circular waveguide 10,
A coaxial line having an outer conductor tube inner radius r2 and a center conductor radius r3 shown in the equation (2) is used so that the TE11 mode cutoff frequency of 14 becomes smaller than the frequency of the electromagnetic wave to be transmitted. It goes without saying that the same condition is applied to the case where the number of the intermediate coaxial lines 14 is plural, and the frequency of the electromagnetic wave transmitted by the coaxial line 12 after the shielding plate 13 is the TE11 mode of the coaxial line 12. If the cut-off frequency is lower than the cut-off frequency, a plurality of coaxial lines with successively smaller tube diameters can be coaxially joined.

The final coaxial line 12 is coaxially joined to the other end of the intermediate coaxial line 14 joined to the circular waveguide 10, and the center of the intermediate coaxial line 14 and the coaxial line 12 in the vicinity of the joining surface is joined. The shield plate 13 is bonded to the conductor 12a. Further, as shown in FIG. 4, the intermediate coaxial line 14 is a taper pipe in which the difference between the inner diameters of the circular waveguide 10 and the coaxial line 12 is continuously changed.
Alternatively, a part or all of the tip of the central conductor in the tapered tube 18 may be a conical column.

The intermediate coaxial line 14 or the circular waveguide
As shown in FIG. 5, the circular waveguide 10 and the rectangular waveguide 15 orthogonal to the central axis of the coaxial line 12 are joined to the other end of the coaxial line 12 to which the 10 is joined. The center conductor 12a of the coaxial line 12 is extended and inserted through the tube wall of the same to form a probe for the rectangular waveguide 15 and a rectangular parallelepiped is formed via a relay shaft 16 made of an insulating material fixed to the central conductor 12a. The central conductor 12 is fixed to the rotating shaft of a motor 17 arranged outside the waveguide 15.
The shield plate 13 fixed to the central conductor 12a together with a may be rotated.

[0015]

As described above, since the circular waveguide and the coaxial line are coaxially joined to each other, it is possible to achieve high precision by relatively simple processing, and to provide a product that is easy to handle and inexpensive. be able to.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a circular waveguide-coaxial line converter of the present invention.

FIG. 2 is an explanatory diagram showing an electric field distribution of the above.

FIG. 3 is an explanatory diagram showing an electric field distribution according to another embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a configuration of the shield plate rotation of the above.

FIG. 6 is a partially cutaway perspective view of a conventional circular waveguide-coaxial line converter.

[Explanation of symbols]

 10 circular waveguide 11 ring-shaped metal plate 12 coaxial line 12a same center conductor 13 shield plate 14 intermediate coaxial line 15 rectangular waveguide 16 relay shaft 17 motor 18 taper pipe

Claims (4)

[Claims] 1. A converter for propagating an electromagnetic wave propagating in a circular waveguide in a TE11 mode in a coaxial line joined to the circular waveguide by a TEM mode electromagnetic wave, wherein the frequency of the electromagnetic wave to be transmitted is in the TE11 mode. A coaxial line with a diameter that increases the cutoff frequency is coaxially joined to the same circular waveguide, and a half of the inner cross section of the pipe up to a diameter perpendicular to the electric field of TE11 mode is attached to the tip of the center conductor of the same coaxial line near the joint surface. A circular waveguide-coaxial line converter characterized in that a shielding plate for shielding is adhered to allow electromagnetic waves in a TEM mode to propagate in the same coaxial line. 2. The circular waveguide is coaxially joined with a plurality of coaxial lines whose outer conductor inner diameters are successively reduced, and the coaxial waveguides are transmitted with a diameter having a cutoff frequency in a TE11 mode lower than the frequency of an electromagnetic wave to be transmitted. 2. The circular waveguide according to claim 1, wherein the shield plate is bonded to a central conductor of the coaxial line in the vicinity of a joint surface of the coaxial line having a diameter that provides a higher cutoff frequency in a TE11 mode than the frequency of electromagnetic waves. A coaxial line converter. 3. The center axes of the circular waveguide and the coaxial line are mutually aligned between the circular waveguide and the coaxial line having a diameter such that the cutoff frequency of the TE11 mode is higher than the frequency of the electromagnetic wave to be transmitted. Join with a tapered taper, make a part or all of the tip of the central conductor in the same tapered tube a conical column, and near the joint surface of the tapered tube and the same coaxial line, the shielding plate to the central conductor of the same coaxial line. The circular waveguide-coaxial line converter according to claim 1, wherein the circular waveguide-coaxial line converter is bonded. 4. A rectangular waveguide in which a rectangular waveguide whose central axes are orthogonal to each other is joined to the other end of the coaxial waveguide where the circular waveguides are joined, and the central conductor of the coaxial line is extended. The same central conductor is further extended by a relay shaft made of an insulating material and fixed to the rotation shaft of the motor provided outside the rectangular waveguide, and the shield is fixed to the same central conductor. The circular waveguide-coaxial line converter according to claim 1, wherein the plate is rotatable.