JPH0218602B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission line switching device, and particularly to a high frequency transmission line switching device that maintains a constant characteristic impedance even when switching transmission lines.

Broadband transmission line switching from DC to SHF bands is described in US Pat. No. 3,500,263, and distributed circuit resistive film attenuators are described in US Pat. No. 3,227,975.

A variable attenuator using this transmission line switching method and a distributed circuit resistive thin film attenuator has a substantially constant amount of attenuation over a wide frequency range from DC to SHF band.

Conventional variable attenuators have structures shown in FIGS. 1 to 3. That is,
The tip of the strip center conductor 2 extending from one end (not shown) of the ground conductor 1 is sandwiched on both sides by guide members 3 made of insulating material, and the guide members 3 are moved left and right by a sliding device 4. By bending the strip center conductor 2, the leading end of the strip center conductor 2 is brought into contact with the through conductor 5 side provided on both sides of the tip of the strip center conductor 2, or the distributed circuit resistance thin film 6 side. The transmission line was switched while keeping the characteristic impedance constant. Note that numerals 7 and 8 are dielectric materials.

The switching of the transmission line used in this variable attenuator is based on the following principle. In Figure 4, the strip center conductor 9 is parallel to the ground conductor 1.
0 and 11, and the long axis of the cross section of the strip center conductor 9 is perpendicular to the ground conductors 10 and 11. In such a case, the electromagnetic field is concentrated on the ground conductors 10, 11 and on the edge portions of the strip center conductor 9 facing the ground conductors 10, 11. Now, assuming that the distance between the ground conductors 10 and 11 is h, and the length of the major axis of the cross section of the strip center conductor 9, that is, the width, is w, the characteristic impedance shown in FIG. 4 is determined by the ratio w/h. Even if the strip center conductor 9 is translated in parallel to the left and right, the electromagnetic field distribution at the edge portion of the strip center conductor 9 remains substantially the same, and its characteristic impedance does not change.

By the way, in switching the transmission line of the variable attenuator shown in FIGS. 1 to 3, as explained above, the characteristic impedance is determined by the width of the strip center conductor 2 and the distance between the ground conductors, that is, the distance between the ground conductors 1 and 2. It is determined by the ratio of the distance in the long axis direction of the cross section of the strip center conductor 2,
For example, in order to downsize the variable attenuator, it is necessary to reduce the width of the strip center conductor 2 and the distance between the ground conductors 1. For this reason, the distance between the strip center conductor 2 and the ground conductor 1 is, for example, in order to maintain the characteristic impedance at 50Ω, when the width w of the strip center conductor 2 is 2.3 mm and the distance between the ground conductors h is 2.75 mm (2.75- 2.3)/2=
It is extremely narrow, such as 0.225 mm, and requires strict precision in processing and assembly accuracy, and has the disadvantage that the effects of these errors on characteristics at high frequencies cannot be ignored. In addition, when it is desired to vary the thickness of the strip center conductor 2, the distance between the ground conductors must be changed, so the ground conductor 1 must be made uneven, which has the drawback of making machining extremely difficult.

In FIG. 5, the strip center conductor 12 is equally spaced between the parallel ground conductors 13 and 14, and the short axis of the cross section of the strip center conductor 12 is perpendicular to the ground conductors 13 and 14. ing. That is, the strip center conductor surface 12
a is parallel to the ground conductor 13. In this case, the electromagnetic field is distributed on the ground conductors 13, 14 and on the strip center conductor surface 12a facing the ground conductors 13, 14 of the strip center conductor 12, respectively. Now, the strip center conductor 12 is placed in the center of the ground conductors 13 and 14, the distance between the ground conductors 13 and 14 is b, the length of the major axis of the cross section of the strip center conductor 12, that is, the width is w,
Assuming that the thickness is t, the characteristic impedance shown in FIG. 5 is determined by the ratio of w/b and t/b.
In order to maintain the characteristic impedance at 50Ω, which is the same as explained in FIG. The thickness t of the strip 12 is 0.125 mm, and the distance between the strip center conductor surface 12a and the ground conductor 13 is (2-0.125)/2=0.9375 mm, which is wider than 0.225 mm shown in FIG. This suggests that the precision of processing accuracy and assembly accuracy can be relaxed. Even if the strip center conductor 12 is moved vertically in parallel, for example, the strip center conductor surface 12
As long as the characteristic impedance is determined by the distribution of the electromagnetic field between the strip center conductor 12 and the ground conductor 13, if the distance between the strip center conductor 12 and the ground conductor 13 is kept approximately constant, the distribution of the electromagnetic field will be approximately the same. Therefore, its characteristic impedance does not change.
In other words, the characteristic impedance remains constant.

The present invention provides a fourth method for switching transmission lines.
The electromagnetic field concentrated at the edge of the strip center conductor, which is equally spaced between the parallel ground conductors shown in the figure, is maintained almost the same even when the strip center conductor is moved in parallel, so that the characteristics From the transmission line switching method that maintains constant impedance, to the structure that maintains the distance from the ground conductor to the strip center conductor surface almost constant despite the movement of the strip center conductor.
Provided is a transmission line switching device that solves the above-mentioned drawbacks by using a transmission line switching method in which the electromagnetic effects between the strip center conductor surface and the opposing ground conductor are distributed almost in the same way, and the characteristic impedance is maintained constant. It is intended to. Therefore, the transmission line switching device of the present invention has first and second inner walls facing each other and extending in the axial direction, which are inclined so that the gap at one end is narrow and the gap at the other end is wide. an outer conductor, one end of which is disposed between an inner wall of the one end along the axis, the other end of which is movable reciprocally across the inner wall of the other end; and at least the other end is magnetic. a first microstrip line and a second microstrip line each having a center conductor formed of a conductor, a contact portion attached to each of the first and second inner walls and contactable to the other end of the center conductor; a line, an excitation means disposed outside the outer conductor for magnetizing the magnetic portion of the center conductor, an N pole on the first microstrip line side and an N pole on the second microstrip line side; Then, the magnetic material portion of the center conductor, which is arranged to have an S pole and is magnetized by the excitation means, is repelled and attracted, and the first microstrip line or the second microstrip line is It is characterized by being equipped with a magnet for contacting and holding the contact portion of the line. This will be explained below with reference to the drawings from FIG. 6 onwards.

FIG. 6 is an internal schematic sectional view for explaining the present invention, FIG. A cross-sectional view of a variable attenuator of one embodiment,
Fig. 9 is a perspective view of a microstrip distributed circuit resistive thin film attenuator, Fig. 10 is a perspective view of a microstrip through element, and Fig. 11 shows the operation of the variable attenuator shown in Fig. 8. FIG. 12 is a sectional view of another embodiment of the variable attenuator according to the present invention, FIG. 13 is a perspective view of a strip center conductor holder, and FIG. 14 is a diagram showing another example of the inner wall of the ground conductor. Figure 3 shows a partial cross-sectional view of the embodiment.

In the internal schematic cross-sectional view for explaining the present invention in FIG. 6, the transmission line switching device according to the present invention is schematically illustrated as two variable attenuators connected in series, excluding the excitation means. The earth conductor 15, which is an external conductor, has a first inner wall 15a and a second inner wall 15b which are inclined so that the gap at one end is narrow and the gap at the other end is wide. Each inner wall 15a, 15b is at the same potential. A strip center conductor 16 having a rectangular cross section is provided on the center axis inside the ground conductor 15, and one end of the strip center conductor 16 is supported by one end of the ground conductor 15 (see FIG. 8).
It is fixed by a circular strip center conductor 17. The other end of the strip center conductor 16 is a free end of a conductive material made of at least a magnetic material. At the position of the inner wall where the gap between the ground conductors 15 is widest and on both end surfaces of the free end of the strip center conductor 15, a microstrip distributed circuit resistive thin film attenuator, which is a first microstrip line, is installed. 18
and a microstrip through element 19 which is a second microstrip line. The strip center conductor 15 has flexibility, and the magnetic material at the tip of the strip center conductor 16 is activated by an excitation means not shown in FIG. It is bent toward the 18 side or the microstrip through element 19 side and electrically connected. At this time, the strip center conductor surface of the strip center conductor 16 and the first and second inner walls 15 of the ground conductor 15
a, 15b is the distance between the first and second inner walls 15 at any position of the strip center conductor 16.
Since a and 15b are sloped, they are almost the same.

Arrows A-A, B- in Figure 7 or Figure 6
Figures B, C-C, and D-D are shown, respectively. In the figure, since the circular strip center conductor 17 is fixed at the center of the ground conductor 15, the electromagnetic field is distributed around the outer periphery of the circular strip center conductor 17. The distribution is concentrated between the ground conductor and the opposing ground conductor.

In the figure, since the strip center conductor 16 is located approximately at the center of the ground conductor 15, the electromagnetic field is concentrated between the long surface of the short strip center conductor 16, that is, between the strip center conductor surface and the opposing ground conductor. The distribution is as follows.

In the figure, the strip center conductor 16 is bent and deviates from the center of the ground conductor 17.
The electromagnetic field has a distribution that is substantially concentrated between the rectangular strip center conductor 16 and the ground conductor to which the strip center conductor 16 is close. However, in reality, an electromagnetic field is generated and distributed between the ground conductors on the opposite side and between the upper and lower edge portions of the strip center conductor 16 and the ground conductor, so the spacing is smaller than the design value of the microstrip line. It is common to take a wide range.

In the figure, since the dielectric material 20 is inserted between the strip center conductor 16 and the ground conductor 15, the electromagnetic field is distributed entirely between the strip center conductor 16 and the ground conductor.

Here, the strip center conductor 16, circular strip center conductor 17, microstrip distributed circuit resistance thin film attenuator 18, microstrip through element 19, etc., together with the ground conductor 15, satisfy a characteristic impedance of a predetermined value. The dimensions are determined and arranged accordingly.

Therefore, the electromagnetic field distribution as described above remains exactly the same even when the rectangular strip center conductor 16 is moved from the microstrip distributed circuit resistive thin film attenuator 18 side to the microstrip through element 19 side. form a distribution. Therefore, switching can be performed without changing the characteristic impedance.

FIG. 8 shows a cross-sectional view of a variable attenuator according to an embodiment of the present invention.
a, 15b, 17 to 19 correspond to those in FIG. Reference numerals 21 and 22 indicate strip center conductors having a rectangular cross section, which correspond to the strip center conductor 16 in FIG. Therefore, the tips of the strip center conductors 21 and 22 are made of at least a magnetic conductive material.

A microstrip distributed circuit resistive thin film attenuator 18 and a microstrip through element 19 are provided in the center of the ground conductor 15, respectively. The microstrip distributed circuit resistance thin film type attenuator 18 has a microstrip distributed circuit resistance thin film 32 attached to the surface of a dielectric 31 as shown in FIG. 33 is installed. In addition, the code 34,
35 is a ground conductor, and 25 is a magnet.

As shown in FIG. 10, the microstrip-through element 19 has a microstrip-through conductor 24 attached to the surface of a dielectric 36, and a ground conductor 37 attached to the back surface of the dielectric 36. The thickness of the dielectric 36 is made to be the same as the thickness of the dielectric 31 shown in FIG. 9.

On the back sides of the dielectrics 31 and 36, magnets 25 and 26 having the polarities shown in FIG.
the first and second inner walls 15a,
It has the same potential as 15b.

One excitation coil 28 wound around a bobbin 27 is provided approximately at the center of the outside of the earth conductor 15, and the strip center conductor 21, 2 made of a magnetic material is changed depending on the direction of the excitation current flowing through the excitation coil 28.
Magnetize the tip of 2. The tips of the magnetized strip center conductors 21 and 22 and the magnet 2
An anti-attractive action occurs between the magnetic poles 5 and 26,
The strip center conductors 21 and 22 are bent,
The tips of the strip center conductors 21, 22 are brought into contact with either side of the microstrip distributed circuit resistive film attenuator 18 or the microstrip through element 19. At this time, as explained above, the distances between the bent strip center conductor surface, for example, the strip center conductor surface of 21, and the ground conductor 33 and the first inner wall 15a, or the distances between the ground conductor 37 and the second inner wall 15b, are formed to be equal. Therefore, the characteristic impedance is maintained almost constant. The same applies to the other strip center conductors 22, and the characteristic impedance is also maintained substantially constant. Moreover, since the thicknesses of the inductors 31 and 36 are the same, the strip center conductors 21 and 22 are connected to the microstrip distributed circuit resistance thin film attenuator 18 side or the microstrip through-hole by the action of the excitation coil 28. No matter how many times the element 19 is contacted, the distance to the ground conductor 33 or 37 is always kept constant, and therefore the characteristic impedance is always constant.

Next, the operation of the variable attenuator shown in FIG. 8 will be explained using FIG. 11. In the figure, reference numeral 17
to 19 correspond to those in FIG. 6, and 21, 2
2, 25, 26, and 28 correspond to those in FIG. The excitation coil 28 is originally wound around the center of the ground conductor 15, but is drawn below the magnet 26 to make the explanation easier to understand.

Now, when the anode and cathode of the DC power source are respectively applied to the terminals 38 and 39 of the excitation coil 28, an excitation current flows through the excitation coil 28 in the direction of the arrow shown in the figure. Due to the excitation current flowing in this direction, the tip of the strip center conductor 22 made of a magnetic material disposed inside the excitation coil 28 is magnetized to the north pole, and the strip center conductor 21 made of a magnetic material is magnetized to the north pole. Since the tip faces the strip center conductor 22, it is magnetized to the south pole. Due to this magnetization, the tip of the strip center conductor 21 is attracted to the N pole of the magnet 25, and
A repulsion occurs at the south pole of the magnet 26, bending the strip center conductor 21, and the tip of the strip center conductor 21 comes into contact with the microstrip distributed circuit resistive film attenuator 18. On the other hand, the tip of the strip center conductor 22 is also attracted by the S pole of the magnet 25, and the magnet 2
A repulsion occurs at the N pole of 6, the strip center conductor 22 is bent, and the strip center conductor 22
The tip makes contact with a microstrip distributed circuit resistive film attenuator 18. That is, the strip center conductor 21 and the strip center conductor 22 are connected to the microstrip distributed circuit resistive thin film attenuator 18.
electrically connected via. Even when the excitation current flowing through the excitation coil 28 is cut off, the attractive force with which the N and S poles of the magnet 25 attract the tips of the strip center conductor 21 and the strip center conductor 22, respectively, is Since the elastic force is greater than the elastic force of each bent strip center conductor 21, 22, the electrical connection between the strip center conductor 21 and the strip center conductor 22 via the microstrip distributed circuit resistive thin film attenuator 18 is maintained. be done.

Next, when the cathode and anode of the DC power source are respectively applied to the terminals 38 and 39 of the excitation coil 28, an excitation current flows through the excitation coil 28 in the direction opposite to the arrow shown in the figure, and the tip of the strip center conductor 21 is N The tip of the strip center conductor 22 is magnetized to the south pole. As a result, a repulsive force is generated between the tips of the strip center conductors 21 and 22 and the N and S poles of the magnet 25, and the strip center conductor 21 is connected to the strip center conductor 21 through the microstrip distributed circuit resistance thin film attenuator 18. The electrical connection between the strip center conductor 22 and the strip center conductor 22 is released. On the other hand, the tip of the strip center conductor 21 magnetized to the N pole is repelled by the N pole of the magnet 25, and
An attractive action occurs between the S pole of the magnet 26 and the strip center conductor 21 is bent, and the tip of the strip center conductor 21 comes into contact with the microstrip through element 19. Similarly, the tip of the strip center conductor 22 magnetized to the S pole is repelled by the S pole of the magnet 25, and an attractive action is generated between it and the N pole of the magnet 26.
The strip center conductor 22 is bent, and the tip of the strip center conductor 22 comes into contact with the microstrip through element 19. That is, by passing an excitation current in the opposite direction to the excitation coil 28, the strip center conductor 21 and the strip center conductor 22
and are again electrically connected via the microstrip through element 19. As explained above, even if the excitation current flowing through the excitation coil 28 is cut off, the attractive force with which the S and N poles of the magnet 26 attract the tips of the strip center conductor 21 and the strip center conductor 22, respectively, is , is greater than the elastic force of each of the strip center conductors 21 and 22 which are being bent, so that the electrical connection between the strip center conductors 21 and 22 is maintained.

Here, when the strip center conductor 21 and the strip center conductor 22 are electrically connected via the microstrip distributed circuit resistive thin film attenuator 18, the microstrip distributed circuit resistive thin film attenuator 18 After the power is attenuated by the amount of attenuation provided by the conductor 18, the power is transmitted from the strip center conductor 21 to the strip center conductor 22 or vice versa. Furthermore, when the strip center conductor 21 is electrically connected to the strip center conductor 22 via the microstrip through element 19, the transmission power can be transferred from the strip center conductor 21 to the strip center conductor 22 or vice versa without attenuating the transmitted power. Power is transmitted in the direction of

In the above explanation, the transmission lines are switched in pairs, but it goes without saying that only one of the transmission lines can be switched.

FIG. 12 shows a sectional view of another embodiment of the variable attenuator according to the present invention, which corresponds to substantially two variable attenuators shown in FIG. 8 connected in series.

Reference numbers 15, 15a, 15b, and 17 correspond to those in Fig. 6, and numbers 18, 19, 27 to 30 correspond to those in Fig.
It corresponds to the one shown in the figure. Reference numerals 40, 41, and 42 are strip center conductors whose tips are made of at least a magnetic material, and 43 is a strip center conductor holder. The strip center conductor holder 43 has the strip center conductor 41 riveted thereto as shown in FIG.

Therefore, by appropriately combining the directions of the excitation currents flowing through the two excitation coils 28, the strip center conductors 40, 41, 42 can be connected to the microstrip distributed circuit resistance thin film attenuator 18 or the microstrip through-hole. It is connected to element 19 and can vary the amount of attenuation of transmitted power while keeping the characteristic impedance approximately constant.

FIG. 14 is a partial sectional view of another embodiment of the inner wall of the earth conductor, where numerals 15 and 17 correspond to those in FIG. 6, and 18, 19, 21, 22, and 29 are
It corresponds to the one shown in the figure. 15'a represents the first inner wall, and 15'b represents the second inner wall. Instead, it was experimentally confirmed that there is no problem in approximating the shape with a shape that can be easily machined. A first inner wall 15'a and a second inner wall 1 having approximate shapes as shown in FIG.
5'b can also be used to practically switch the transmission line.

In the above description, the magnets 25 and 26 are not limited to the rod-shaped magnets shown in the drawings, but a plurality of magnets may be used to provide the polarities shown in the drawings. It goes without saying that the polarities of the magnets 25 and 26 may all be reversed.

As explained above, according to the present invention, the distance between the strip center conductor surface of the strip center conductor having a rectangular cross section and the inner wall of the ground conductor is maintained substantially constant to switch the transmission line. In this case, the distance between the strip center conductor and the ground conductor can be increased, and the labor required for processing accuracy and assembly accuracy can be reduced, making it possible to provide an excellent transmission line switching device. The transmission line can be switched with the characteristic impedance kept almost constant, and the switching device has sufficient isolation and insertion loss characteristics at high frequencies.

Since the transmission line is switched without contacting the strip center conductor depending on the direction of the excitation current flowing through the excitation coil, the switching operation is stabilized.

In addition, by using the transmission line switching device of the present invention in a variable attenuator, a variable attenuator with excellent frequency characteristics that can attenuate the attenuation amount almost constant over a wide range of frequencies from DC to high frequencies can be obtained. Become.

[Brief explanation of drawings]

Fig. 1 is a partial sectional view of a conventional transmission line switching device, Fig. 2 is a view taken along the X-X arrow in Fig. 1, Fig. 3 is a view taken along the Y-Y arrow in Fig. 1, Figs. Fig. 5 is a principle explanatory diagram for explaining characteristic impedance, Fig. 6 is an internal schematic sectional view for explaining the present invention, and Fig. 7 is an explanation of the distribution of the electromagnetic field in each arrow direction in Fig. 6. 8 is a sectional view of a variable attenuator according to an embodiment of the present invention, FIG. 9 is a perspective view of a microstrip distributed circuit resistive thin film attenuator, and FIG. A perspective view of a through element, FIG. 11 is an explanatory diagram for explaining the operation of the variable attenuator shown in FIG. 8, and FIG. 12 is a sectional view of another embodiment of the variable attenuator using the present invention. FIG. 13 shows a perspective view of the strip center conductor holder, and FIG. 14 shows a partial sectional view of another embodiment of the inner wall of the ground conductor. In the figure, 15 is a ground conductor, 15a, 15'a are first inner walls, 15b, 15'b are second inner walls, 1
6 is a strip center conductor, 17 is a circular strip center conductor, 18 is a microstrip distributed circuit resistive thin film attenuator, 19 is a microstrip through element, 20 is a dielectric, 21 and 22 are strip center conductors, 24 is a microstrip through conductor, 25 and 26 are magnets, 27 is a bobbin, 2
8 is an excitation coil, 29 and 30 are input/output plugs, 31 is a dielectric, 32 is a microstrip distributed circuit resistance thin film, 33 to 35 are ground conductors, 36 is a dielectric, 37 is a ground conductor, 38 and 39 are terminal, 40
Reference numerals 42 to 42 represent strip center conductors, and 43 represents a strip center conductor holder, respectively.

Claims (1)

[Claims] 1. An outer conductor 15 having the same potential and having first and second inner walls that are inclined so that a gap at one end is narrow and a gap at the other end is wide and extend in the axial direction in opposition to each other; A central conductor 16 whose one end is arranged between the inner walls of the one end and whose other end is capable of reciprocating movement between the inner walls of the other end, and at least the other end is made of a magnetic material; a first microstrip line 18 and a second microstrip line 19 each having a contact portion attached to each of the first and second inner walls and capable of contacting the other end of the center conductor 16; excitation means 28 disposed outside the outer conductor 15 to magnetize the magnetic portion of the central conductor 16; an N pole on the first microstrip line 18 side; The side of the central conductor 16 is arranged so as to have an S pole, and attracts the magnetic part of the center conductor 16 magnetized by the excitation means.
A transmission line switching device comprising magnets 25 and 26 for contacting and holding contact portions of the first microstrip line 18 or the second microstrip line 19.