JPH0235801A - Small ridge waveguide and coaxial line converter - Google Patents

Abstract

PURPOSE:To more satisfactorily execute the impedance matching in a small and wide band of one octave or above by changing the diameter of the coaxial core in the pipe of a mode converting part to two steps and providing it close to a pipe electric field wall. CONSTITUTION:A mode converting part 42 provided between a single ridge 40b and a coaxial line part 41 and to obtain the impedance matching of a ridge waveguide part 40 and the coaxial line part 41 is constituted by arranging plural coaxial cores 43 and 44 having a different diameter in an axial direction and provided close to a pipe electric field wall 45 so as not to abut to a pipe electric field wall 45. Thus, the impedance matching of the coaxial line part 41 and the ridge waveguide part 40 can be fine adjusted, the characteristic impedance of the converting part 42 is lowered, and can be sufficiently set to the characteristic impedance of the coaxial line part 41. Thus, the impedance matching can be easily and satisfactorily executed. By using the double ridge, by specifying the cross section accurately, the action frequency of the wide band of one octave or above can be secured, and the small waveguide of the aperture diameter of lambda/4 or below at a lower limit frequency can be formed.

Description

[Detailed description of the invention] (General S) One side is configured as a double ridge and the other side is configured as a single ridge, and a coaxial line is provided on the single ridge side, and the TEM of the coaxial line is
To provide a ridge waveguide/@axis line converter that converts a mode to a TE mode of a ridge waveguide, which is small and achieves better impedance matching in a wide band of one octave or more. For this purpose, a mode conversion section is provided between a single ridge and a coaxial line section to match the impedance of the ridge waveguide section and the coaxial line section, by arranging a plurality of coaxial cores with different diameters in the axial direction. and is arranged close to the upper boundary wall inside the tube so as not to come into contact with the electric field wall inside the tube.

[Industrial application field]

In the present invention, one side has a double ridge and the other side has a single ridge, and a coaxial line is provided on the single ridge side.
The present invention relates to a ridge waveguide/coaxial line converter that converts the TEM mode of an I-axis line to the TE mode of a ridge waveguide.

Fuji waveguide/coaxial line converters with such a configuration are used in ultra-small wideband antennas used in phased array anti-no systems such as microwave radar and communication equipment, and are used in recent communication systems. Research and development is actively being carried out in response to demand from various fields.

In general, in a phased array antenna, if the array pitch d between antenna elements does not satisfy the following conditions, unnecessary beams (referred to as grating lobes and at the same level as the main beam) will be generated in directions other than the main beam. . rH is the operating upper limit frequency, C is the speed of light, λH=C/f+,
If ±θ is the beam scanning range, the condition for the array pitch d to avoid generating unnecessary beams in the case of a linear array is d≦
λH/(1+sin 1 θI). Therefore 7
The higher the bandwidth of the Aze array antenna, the more severe the conditions for the array pitch d become. For example, frequency band 2:
1. When the beam scanning radius is ±45°, the array pitch d of the linear array that does not generate unnecessary beams is d = 0.59λH-
0,29AL(-C/ f L , f L G, t
It is necessary to set the operating frequency below the lower limit frequency a), and the antenna element is forced to be smaller.

Therefore, in order to satisfy this condition, there is a demand for a 1q ridge waveguide/coaxial line converter that is ultra-small and has good broadband impedance matching with the coaxial line and ridge waveguide. .

[Conventional technology]

FIG. 6 shows a configuration diagram of a general Norifuji waveguide/coaxial line converter. The electric field coupling type, not shown in Figure (A), has a structure in which the axial direction of the coaxial line 1 and the axial direction of the ridge waveguide 2 are at right angles, and has double ridges at both ends, and is not currently used. Most of the converters currently available are of this type.Since the axial direction of the coaxial line 1 and the axial direction of the ridge waveguide 2 are perpendicular to each other, a relatively large space is required for this type, and there is plenty of space for mounting. Cannot be used if it is not present.

The magnetic field coupling type (end launcher) shown in the same figure (B) is the same @
It has a structure in which the axial direction of the line 3 and the axial direction of the ridge waveguide 4 are parallel, with a double ridge at one end and a single ridge at the other end, which does not require much space, so there is no extra space for mounting. Use in case.

However, the internal dimensions of both the electric field coupling type and the magnetic field coupling type are 0.
4λL or more, external dimension is 05λL including waveguide wall thickness
This is the above (λL=c/'ffi:, fL is the lower limit frequency of operation, and C is the speed of light).

[Problem to be solved by the invention]

When high-density packaging is required, the conventional structure described above is too large, and if you try to downsize it, you cannot achieve a wide band.
Currently, nothing has been achieved that satisfies both parties. In general, miniaturization of waveguides and broadbandization are contradictory technologies.

Therefore, the present applicant previously proposed in Japanese Patent Application No. 19517/1983 (title of the invention 1: Ultra-small wideband antenna) "a coaxial waveguide conversion section provided in the antenna axis direction, and the coaxial waveguide conversion section. and a double ridge waveguide section that impedance matches the
It is composed of a dielectric material that matches the impedance between the double ridge waveguide section and the external space. 1. We proposed an ultra-small wideband antenna. In this device, the coaxial/waveguide conversion section is configured with a balun circuit for impedance matching consisting of a single ridge and a step transformer in order to position the power supply connector at the center of the axis of the antenna. A double ridge waveguide portion is gradually formed as a double ridge structure, and impedance matching is achieved. In addition, impedance matching with space is achieved by installing a dielectric material in the opening.

According to this product, by strictly defining the cross section of the double ridge waveguide, an operating frequency of more than one octave is secured, an aperture diameter of less than a quarter wavelength is realized at the lower limit frequency, and a small size is achieved. can be converted into In addition, good SWR (standing wave) characteristics are obtained over the entire band by matching the impedance from the coaxial connector where the signal is fed to the opening where the signal is sent out.

However, this method does not mention the detailed structure that allows for better impedance matching.
It is small and has a broadband performance of 1q.

SUMMARY OF THE INVENTION An object of the present invention is to provide a small ridge waveguide/coaxial line converter that is small and can perform impedance matching better in a wide band of one octave or more.

[Means to solve the problem]

FIG. 1 shows a diagram of the principle of the present invention. In the figure, 40 is a ridge waveguide section, and -r is a double ridge 40a.

The other end is constituted by a single ridge 40b.

A coaxial line portion 41 is provided on the single ridge 40b side. The transducer targeted by the present invention is coaxial with the axis of the ridge waveguide section 40! This is a magnetic field coupling type ridge waveguide/coaxial line converter in which the axis of the J path portion 47 is configured parallel to the axis.

The present invention provides a mode converter &; 42 provided between the single ridge 40b and the coaxial line section 41 for impedance matching between the ridge waveguide section 40 and the coaxial line section 41, which is connected to a plurality of coaxial cores having different diameters. 43° 44 are drawn side by side in the axial direction, and are provided close to the intra-tube electric field wall 45 so as not to come into contact with the intra-tube electric field wall 45.

(Function) By having a configuration in which the diameter of the coaxial core inside the pipe of the converting section 42 is changed in two stages (coaxial core 43, 44), the coaxial line section 4
1 and the ridge waveguide section 4o, and the coaxial core 4 of the conversion 8II42 can be finely adjusted.
By providing 3.44 close to the electric field wall 45 in the tube, the characteristic impedance of the conversion section 42 is lowered and can be set sufficiently close to the characteristic impedance of the line section 41, thereby making impedance matching easy and easy. , can perform well.

On the other hand, by using a double ridge and strictly defining its cross section, it is possible to secure a broadband operating frequency of one octave or more, and to create a small waveguide with an aperture diameter of λ/4 or less at the upper limit frequency. can be realized.

[Example] Figure 2 shows the amount of phosphoric acid in an example of the present invention. Same figure (A>
is a side sectional view, (B) is a BB cross-sectional view, and (C) is a side sectional view.
is a C-c''' top view.The unit of dimensions shown in each figure is shoes.This item has an inner dimension of 8# x 6IrMl (tmari, o, 21λL x O, 16λL), and λL
/4 or less, and the frequency band is 8 GHz to 18 GHz.

In the same figure, 10 is a double ridge, 10a is a 7 lunge, 11
is a single ridge, and forms a TE mode ridge waveguide section with the tapered section 12 in between. 13 is a 50Ω sympathy connector, which is surrounded by fluororesin 14 and has a diameter of 131φ (
Operating center frequency f.

A coaxial core 15 of 0806λ0) at 13 GHz is provided, forming a TEM mode coaxial line section. 16.17 are coaxial cores in the tube, each having a diameter of 2.4Hφ (0,
1λO) and 2Hφ, and is provided coaxially with the coaxial core 15 and in contact with the single ridge 11.

The coaxial cores 16 and 17 in the tube form a TE mode/TEM mode conversion section.

Here, the total length of the inner tube coaxial cores 16 and 17 is 0.13λ0 at the operating center frequency fo, and the diameter of the inner tube coaxial core 16 is set to about twice the diameter of the coaxial core 15 of the coaxial connector 13. ing. In this case, the diameter of the coaxial core inside the pipe of the converter is 2
Since it has a structure that changes in stages (coaxial cores in the tube 16 and 17), it is possible to finely adjust the impedance matching between the coaxial line part and the ridge waveguide part, and it is possible to perform good impedance matching. .

Further, the in-tube coaxial cores 16 and 17 are provided close to the in-tube electric field wall 18 to the extent that they do not come into contact with the in-tube electric field wall 18. As a result, the characteristic impedance of the converting section is lowered and can be set sufficiently close to the characteristic impedance of the coaxial line section, 50Ω. Usually, the inner coaxial core 16.17 corresponds to the mode conversion part
The length is set according to the tube wavelength, but the electromagnetic field distribution in the mode converter is generally very complex, and the tube wavelength cannot be easily calculated. The impedance matching between the coaxial line section and the ridge waveguide section cannot be achieved easily.

Therefore, in the present invention, the diameter of the inner coaxial core of the converting section is changed in two stages (inner coaxial core 16 and 17), and the diameter is changed in two steps (inner coaxial core 16 and 17), and by providing a structure close to the electric field wall 18, ,
Impedance matching is easily and satisfactorily achieved.

On the other hand, the single ridge 11 has the same characteristic impedance @
The characteristic impedance of the line section should be close to 50Ω (8
(63Ω at GHz, 48Ω at 18GHz), and the dimensions are optimized so that the cutoff frequency of the fundamental mode T E +i is sufficiently lower than the frequency band used. In this case, if the cutoff frequency is set high, the characteristic impedance will increase, making it difficult to match with the coaxial line section. As the actual value of the cutoff frequency, the cutoff frequency of the single ridge 11 is fc to = 5.4 GHz in the fundamental mode TE IG, and in the higher mode TE?
In Q, fc redundancy = 25 GHz, and the cutoff frequency of double ridge 10 is fcl in fundamental mode T E to
O=6.7GHz, f'c at higher mode T E 20
n=45GHz. Therefore, the actual usage band 8GH
The mode in the waveguide at z ~ 18 GHz is the fundamental mode T E
There will be only to.

With such a configuration, the mode conversion section performs mode conversion from the TEM mode of the line section to the TE mode of the ridge waveguide section, and at that time, impedance matching is performed satisfactorily. Also, similar to the aforementioned "reduced wideband antenna" previously proposed by the present applicant, a double ridge is used to change the cross section to Ii! By closely defining it, an operating frequency of one octave or more can be ensured, and a small waveguide with an aperture diameter of λ/4 or less at the lower limit frequency can be realized.

FIG. 3 shows a block diagram of another embodiment of the present invention.

The same figure (A) is a side sectional view, the same figure (B) is a BB-sectional view,
The same figure (C) is a CC cross-sectional view. Note that the unit of dimensions shown in each figure is ``1''.This antenna has a circular outer shape of 10φ in order to be applied to a wideband phased array antenna, and the frequency band is 8G, which is the same as the one in Figure 2.
Hz to 18 GHz, which results in an outer diameter of 0.27λL.

In the figure, 20 is a double ridge, 21 is a single ridge, and a TE mode ridge waveguide portion is formed with a tapered portion 22 in between. The inside of the waveguide is rounded to match the outer shape, and has a diameter of 9mm, with a diameter of 0.24λL. The characteristic impedance of the single ridge 21 is 84 at 8 GHz.
Ω, 51Ω at 18GHz. 23 is a 50Ω coaxial connector, which is an airline type, surrounded by a fluororesin 24, and connected to coaxial cores 25 and 1 of 0.7 tmφ.
A coaxial core 26 with a diameter of 3 mm is provided, and forms a coaxial line section in the TEM mode. In this case, coaxial connector 2
Since the coaxial core 3 is an airline type, the coaxial core is thinner than a normal coaxial core, so the coaxial core 25 and 26 of this embodiment are configured to gradually become thicker.

27 and 28 are coaxial cores in the pipe, each having an order of 2.3 and φ to 2.4a.
It is set to a+φ, 2am+φ, and the coaxial core is 252
6 and is in contact with the single ridge 21, and is provided close to the intra-tube electric field wall 29. The tube coaxial cores 27 and 28 form a TE mode/TEM mode conversion section. In this embodiment, since a central feeding system is adopted in which the coaxial connector 23 and the waveguide axis are aligned,
The waveguide size (4, 4 m) of the single ridge 21 is set smaller than the waveguide size (6, w 2 ) of the double ridge 20.

The above configuration is made in consideration of arrangement properties in a phased array antenna.

As an actual value of the cutoff frequency, the cutoff frequency of the single ridge 21 is f c to = 6.6 GHz in the fundamental mode T E to , and in the higher order mode T E m
The cutoff frequency of the double ridge 20 is f Ct in the fundamental mode T E to.
o = 6.6 GHz, fcn = 45 GHz in higher mode T E 2G. In this case as well, the only mode within the waveguide in the actual usage band of 8 GHz to 18 GHz is the fundamental mode T E to.

By the way, when measuring the insertion loss in each of the embodiments shown in FIGS. 2 and 3, as shown in FIG. An input wave is input, reflected by a metal plate, and extracted as a reflected wave.

When the insertion loss is measured from the respective levels of the human power wave and the reflected wave, the results are as shown in FIG. In the same figure, the -dotted chain line is 8
Insertion loss characteristics at GHz to 18 GH2 are 0.4 to 0.6 cE for each example.

〔Effect of the invention〕

As explained above, according to the present invention, the diameter of the coaxial core in the tube of the mode conversion section is changed in two steps, and the coaxial line section and the ridge waveguide are The impedance matching with the other parts can be easily and better performed, and it can be used in a wide band of one octave or more, and can be constructed in a small size.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a block diagram of one embodiment of the present invention, Fig. 3 is a block diagram of another embodiment of the present invention, and Fig. 4 is a method for measuring insertion loss. 5 is an insertion loss characteristic diagram of the present invention, and FIG. 6 is a configuration diagram of a general Norifuji waveguide/coaxial line converter. In the figure, 10.20.40a is a double ridge, 11.21 and 40b are single ridges, 12.22 is a taper part, 13.23 is a coaxial connector, 15.25.26 is a coaxial core of a coaxial connector, and 16.17
．． 27, 28, 43, and 44 are coaxial cores in the tube of the mode conversion section, 18, 29, and 45 are electric field walls in the tube, 40 is a ridge waveguide section, 41 is a coaxial line section, and 42 is a mode conversion section. Patent applicant Fujitsu Fujitsu Makamezu Co., Ltd.

Claims (1)

[Claims] An axis of a ridge waveguide section (40) consisting of a double ridge (40a) at one end and a single ridge (40b) at the other end, and a ridge provided on the side of the single ridge (40b). In a magnetic field coupling type ridge waveguide/coaxial line converter configured in parallel with the axis of the coaxial line section (41), the single ridge (40b) and the coaxial line section (41)
) for impedance matching between the ridge waveguide section (40) and the coaxial line section (41).
) (44) arranged in the axial direction, and provided close to the internal electric field wall (45) so as not to come into contact with the internal electric field wall (45). /
Coaxial line converter.