JPS6333721B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an ultra-high frequency band isolator, and particularly to a small magnetic resonance type isolator. In order to configure communication equipment or broadcasting equipment in ultra-high frequency bands, especially in the UHF band, small isolators are essential to avoid the effects of unnecessary reflections at the connections between systems or individual circuits. However, in the past, especially for low microwave bands,
There are few small and inexpensive isolators, and small attenuators are often inserted to reduce the influence of unnecessary reflections, sometimes even at the expense of transmission loss. As an isolator for such applications, a conventional magnetic resonance isolator, as shown in Figure 1, has a cost advantage resulting from its simple structure and has the potential to be widely used. . As shown in Fig. 1, a conventional magnetic resonance isolator has a ferrimagnetic plate 2 inserted into a dielectric substrate 1, a ground conductor 3 on one side, and a main line on the other side. 11 and branch line 12 with open end
A branch line 13 with a short-circuited end is formed, and these are connected to the joining electrode 4 on the ferrimagnetic plate 2 so as to intersect with each other. A predetermined magnetic resonance DC magnetic field is applied to this joint portion by an external magnet 5. In this case, IEICE Microwave Study Group materials
As described in MW74-89 (pages 129 to 9137), the main line 11 is an input/output introduction line, and its characteristic impedance is 50Ω, which is the input/output impedance of the normal system and individual circuits. Impedance Z is set to ₀ . Further, the impedances Zc and _ZL of the branch lines 12 and 13 viewed from the main line side are expressed by the following equations. Zc＝−jZc ₀ cotβlc (1) Z _L ＝jZ _L0 tanβl _L (2) However, Zc ₀ and Z _L0 are branch path characteristic impedance, β
is the propagation constant, lc, l _L are the respective lengths (for simplicity, the length from the junction electrode end is used below, but it is also possible to use this as the length from the junction center or from the line end). (no fluctuation occurs). Then, if the width and length of the branch lines 12 and 13 are set to satisfy the condition Z ₀ = |Z _L | = | Zc | = Zc ₀ cotβlc = Z _L0 tanβl _L (3), the input/output VSWR
is 1, and at the same time, a rotating magnetic field is excited in the joint, and the applied DC magnetic field is said to exhibit isolator characteristics. The above conditional expression (3) means that when Z ₀ =Z _L0 =Zc ₀ , both lc and l _L are set to 1/8 the length of the wavelength of the operating frequency. However, when a conventional isolator satisfying the above conditions was prototyped, only the characteristics shown in FIG. 2A were obtained. In other words, the diameter of the bonding electrode is 6
mm・Ferimagnetic plate 2 has a diameter of 6 mm and a thickness of 1 mm.
4πMs: Use 480 Gauss, Z ₀ = Zc ₀ = Z _L0 =
The second characteristic is when setting 50Ω, lc = l _L = 27mm.
As shown in Figure A, the VSWR is approximately 1 near the frequency with a wavelength approximately 8 times the length of the branch line, and the forward loss is good at 0.5 dB, but the maximum reverse loss is only about 10 dB. It has been found. Therefore, even if the conventional structure of the isolator is simple, its characteristics are poor and it is difficult to put it into practical use. In order to increase such reverse direction loss, a method of connecting two of these isolators in series has been taken, but the structure becomes complicated, the size doubles, and the forward direction loss also doubles. Furthermore, even if the conventional isolator mentioned above is made smaller by bending the branch line, the
The board size was larger than a square, and there was a drawback that the size was quite large. SUMMARY OF THE INVENTION An object of the present invention is to overcome the drawbacks of the conventional structure as described above, and to provide an isolator with a new structure that has sufficient practical characteristics, is small in size, and is economical. According to the present invention, a ferrimagnetic plate is provided on a ground plane, which is magnetized by a magnetic field perpendicular to the plane, and further has a plane parallel to the ground plane on the top surface thereof, and is 90 degrees from each other.
The second and fourth openings of the magnetic circuit junction are arranged with a junction electrode having four openings, first, second, third, and fourth in the order of angular direction, with angular intervals of By loading positive and negative reactance circuits whose values are equal to the magnitude of the junction impedance and setting the strength of the magnetic field to a predetermined magnitude, the entire junction including the ferrimagnetic plate is placed in a magnetic resonance state. The isolator is characterized in that an impedance conversion circuit having a predetermined conversion ratio corresponding to the impedance of the joint portion is connected to the first and third openings to serve as input/output ports. In the isolator with the conventional structure described above, when the applied magnetic field is strengthened, the peak of the reverse direction loss increases and shifts to the high frequency side along the dotted line P in Figure 2, and at a certain point, the characteristics as shown in Figure 2B occur. It was found that it was possible to obtain In this case, the reverse loss is 20dB
As a result, the 10 dB reverse loss band also increases to about 10%. However, the input/output VSWR shifts almost along the dotted line q, where the above-mentioned reverse direction loss is large.
VSWR deteriorates to 3-5. Therefore, the insertion loss also deteriorates to 1.5 to 2.0 dB. The dotted line q shows the frequency characteristics of VSWR when the applied magnetic field is sufficiently strong and the ferrimagnetic plate can almost be regarded as a dielectric.
Let the frequency that gives the minimum VSWR be f ₀ . Also, let f _r be the frequency that gives the maximum peak of the dotted line p.
The larger the joint size, the greater the separation of f ₀ and f _r , which cannot be explained by the conventional isolator design method that ignores the finite size of the joint. Therefore, we invalidated equation (3), which is the conventional isolator condition, and experimentally determined the changes in f ₀ and f _r by changing the dimensions of branch lines 12 and 13 and the strength of the applied magnetic field, as shown in Figure 3. The results were obtained. The horizontal axis of the figure is the length of the terminal short-circuited branch line 13 _{l L}
The vertical axis is the frequency, and the parameter is the length lc of the open-ended branch line 12. In the figure, points A and B indicate the state where characteristics A and B in FIG. 2 are obtained. According to FIG. 3, for example, C, where f ₀ and f _r match as a result of removing the conventional conditional expression (3),
We discovered that a new configuration such as point C′ exists. In the state where f ₀ f _r , the branch line impedance
Z _L and Zc indicate positive and negative reactance, respectively, and their magnitudes are almost the same. However, its value is significantly different from the main line impedance set in conventional designs, and therefore Z _L0 , Zc ₀
Even if lc ₀ and l L0 are made equal to Z ₀ , it is not necessary to make lc 0 and l _L0 equal. Now, the magnitude of these matching positive and negative reactances is defined as the junction impedance Zr, and when Zr is determined for various junction dimensions and ferrimagnetic materials, the results are as shown in Table 1. I discovered that it can become a thing. However, the second method simply matches the magnitude of the branch line reactance with the junction impedance Zr.
When determining the isolator characteristics using the state structure in Figure C,
As shown by the dotted line in Figure 4, it has become clear that although a large reverse loss can be obtained, the VSWR still worsens and the forward loss also increases. It was found that in this state, when applying a magnetic resonance magnetic field, the junction impedance loaded with the branch line still remains at a value that almost matches Zr, and the results show that the input/output aperture and the input/output line with impedance Zo Between
We found that when an impedance conversion matching circuit with a conversion ratio of Zr and Zo of Zo/Zr is inserted, the VSWR, forward loss, and reverse loss all exhibit very good characteristics, as shown by the solid line in Figure 4. Ta.

[Table] Based on the findings of the present inventors, the present invention loads a positive and negative reactance circuit as a branch line, which almost matches the impedance specific to the joint made of the ferrimagnetic plate 2 and the joint electrode 4, and By loading the output aperture with an impedance conversion matching circuit that converts the impedance inherent to the junction into the normal 50Ω input/output line impedance, the characteristics of the conventional isolator shown in Fig. 2A are changed to those of the present invention shown by the solid line in Fig. 4. As shown in the characteristics, this is an attempt to significantly improve reverse loss characteristics while maintaining good input/output VSWR and forward loss. In the past, sufficient isolation could not be obtained because the dimensions of the joint were made infinitely small, but with the fifth
As shown in the model in Figure a, the joint consisting of the ground conductor 3, ferrimagnetic plate 2, and joining electrode 4 always has finite dimensions, and the equivalent circuit resulting from this dimension is as shown in Figure 5 b. It is represented by a capacitor Cj and inductors Lj ₁ , Lj ₂ , Lj ₃ , and Lj ₄ . Usually 4
In the rotationally symmetric case, all inductances are equal, they are loaded with the permeability of the ferrimagnetic material in the applied magnetic field, and together with the capacitor they exhibit a junction-specific impedance Zr. Therefore, it is possible to realize a sufficiently good isolator for practical use only by the present invention, which loads a positive/negative reactance circuit and an impedance conversion matching circuit that are compatible with these. In other words, by loading a positive/negative reactance circuit and an input/output matching impedance conversion circuit suitable for the junction impedance, it is possible to solve the finite size that was ignored in the conventional example. A rotating magnetic field was excited over the entire joint, and the magnetic resonance caused by the applied magnetic field could be achieved over the entire joint, thus exhibiting a large magnetic resonance phenomenon. In the conventional example, only a part of the joint was excited by the rotating magnetic field, and although the magnetic resonance phenomenon was excited by the applied magnetic field, it was only partially, which is thought to be the reason why the peak of the isolation characteristic was small. The present invention will be described in detail below using examples. FIG. 6 is a plan view showing the first embodiment of the present invention. In the figure, a dielectric substrate 1 is placed on a single ground conductor (not shown), a ferrimagnetic plate 2 (dotted line) is inserted into a hole in the center of the dielectric substrate, and a bonding electrode 4 is placed on it. Together with this, they form a joint. Two opposing terminals of the four terminals of the bonding electrode 4 are provided with positive and negative reactance circuits for excitation of a rotating magnetic field, each consisting of a branch line 13 whose terminal end is short-circuited by the grounding electrode 3' and a branch line 12 whose terminal end is open. is connected to the remaining two terminals, and an impedance conversion circuit consisting of a series line 14 and a parallel line 15 is connected to the remaining two terminals, which are connected to the input/output main line 11 and the input/output connector 20. Furthermore, an isolator can be obtained by applying an external magnetic field perpendicular to the plane of the paper to the joint. In this embodiment, all the strip line conductor widths were formed to have a characteristic impedance that matched the input/output impedance of 50Ω. On the other hand, the junction impedance Zr is usually smaller than this as shown in Table 1, so the branch line 1
The length l _L of 3 is considerably smaller than 1/8 wavelength of the operating frequency, and the length lc of branch line 12 is set considerably larger than 1/8 wavelength of the operating frequency, but shorter than 1/4 wavelength. A reactance whose absolute value is approximately equal to Zr is applied to the joint. This provides a sufficiently large isolation. Further, the junction impedance of Zr is converted and matched to an input/output impedance of 50Ω by an impedance conversion equivalent LC circuit consisting of a series line 14 and a parallel line 15. This makes it possible to improve input/output VSWR and forward loss while maintaining large isolation. The dielectric substrate 1 includes Teflon (trade name, the same applies hereinafter) - a high frequency printed board such as a glass printed board,
So-called inorganic glass or ceramic dielectric plates such as alumina, quartz, and Ba-TiO ₂ are used. Further, as the ferrimagnetic plate 2, Ca-V,
A microwave garnet plate such as Y-I type or a garnet plate mixed with Gd can be used. The conductor pattern of the circuit is obtained by microwave IC fabrication techniques. In addition, the externally applied magnetic field can be applied using a normal electromagnet or a permanent magnet such as AlNiCo, Ba, Sr, etc. The entire structure is housed in a magnetic circuit case and made into individual components, which is similar to the structure of a normal microwave circulator or isolator. Needless to say, it can be done. FIG. 7 is a plan view showing a second embodiment of the present invention. In this embodiment, the same junction and branch line as in FIG. 6 are used, and a 1/4 A wavelength conversion line 16 is used and connected to a 50Ω input/output connector. 1/4
By using the wavelength impedance conversion line 16, a simpler circuit pattern can be achieved. All the same components as in the first embodiment of FIG. 6 are indicated by the same numbers. FIG. 8 is a diagram showing a third embodiment of the present invention,
A and b are perspective views of a magnetic circuit section and a main body circuit section, respectively, and c is an equivalent circuit of the main body circuit section. In FIG. 8, a joint portion consisting of a ground conductor 3, a ferrimagnetic plate 2, and a joint electrode 4 is fixedly arranged in the center of a magnetic metal plate 10 such as soft iron, and its second and fourth terminals are respectively A lumped constant inductor 130 and a lumped capacitor 120 are connected to the ground terminal 30 to form a positive and negative reactance circuit, respectively, and a parallel lumped capacitor 150 is connected to the first and third terminals via a series lumped inductor 140. are connected to the input/output terminal 200, and these constitute an input/output impedance conversion circuit. These equivalent circuits are expressed as c. Further, a top cover 51 made of magnetic metal with a permanent magnet 50 attached thereto is placed over the top and fixed to the set screw 101 with a set screw 101', thereby magnetizing the ferrimagnetic plate 2 and serving as a cover for the magnetic circuit section. At the same time that is constructed, a small isolator with mounting holes 102, 102' is completed. In this embodiment, since the positive/negative reactance circuit and the input/output impedance conversion circuit are all composed of lumped constant elements, they can be made extremely compact not only in the high frequency band of the UHF band but also in the low frequency band. Furthermore, since the number of component parts is small and the conventionally widely used capacitors and inductors are used, the cost can be extremely reduced.
In addition, as shown in the figure, the ferrimagnetic plate 2 is made by bonding and fixing a ground conductor 3 that has been metalized on the back side of the magnetic plate 2 to the magnetic metal plate 10 by soldering or the like, or by directly bonding the ground conductor 3 to the magnetic metal plate 10 using an adhesive or the like. It may be fixed by adhesive to 10. In either case, a magnetic metal plate 10 is usually fixed directly to the heat sink.
Since the ferrimagnetic plate 2 and the ferrimagnetic plate 2 are directly bonded, the temperature characteristics and power characteristics are also good. In this embodiment, a magnetic metal plate 1 is used as the support.
0, and by using a magnetic metal as the case top cover 51, the magnetic circuit and the case can be used for both. Needless to say, it can be constructed using the body and the upper lid. It is also possible to use two permanent magnets to magnetize the ferrimagnetic plate from above and below to form a more uniform magnetic field. FIG. 9 is a perspective view showing a fourth embodiment of the present invention, showing only the main circuit section corresponding to FIG. 8b. Further, the same components as those in the third embodiment shown in FIG. 8 are indicated by the same numbers. In this embodiment, the inductor 130 for the positive reactance circuit, the inductor 140 for the input/output impedance conversion circuit, the connection terminal, the grounding conductor 3', etc. are all formed as conductive patterns on the surface or side surface of the dielectric substrate 1 with a hole in the center. The whole is mounted and fixed on the magnetic metal plate 10 together with the ferrimagnetic plate 2 to which the bonding electrode 4 is fixed, and then the bonding electrode terminal and the circuit pattern are connected, and the negative reactance circuit capacitor 120 and the input are connected. By mounting and connecting the output impedance conversion circuit capacitor 150 on the circuit pattern, it is possible to configure a small isolator with fewer manufacturing parts. As described in the first embodiment, as the dielectric substrate 1, if an ordinary Teflon glass fiber or other printed board, or an inorganic ceramic dielectric substrate such as alumina is used, a conductive circuit pattern can be formed using current electronic circuit technology. It is extremely easy to form them in large quantities and with high precision. It goes without saying that the grounding conductor 3' does not need to be turned around the entire side surface as shown in the figure, and that through-hole metallization may be used instead. FIG. 10 is a perspective view a showing a fifth embodiment of the present invention and a sectional view b taken along line AA' in the same figure, and like the previous figure, only the main body circuit section corresponding to FIG. 8b is shown. Identical components are indicated using the same numbers. In this embodiment, the ferrimagnetic plate 2 is fitted into the through hole of the dielectric substrate 1 and the whole is sintered, or the gap is filled with glass or the like, and the upper and lower surfaces are polished as necessary. After forming one substrate, a single ground conductor 3 is formed on one surface, and a single conductor pattern is formed on the other surface by microwave IC techniques such as vapor deposition, plating, and photoetching, and a bonding electrode is formed on the other surface. 4. Inductor 130 for positive/negative reactance circuit and input/output impedance conversion circuit,
140 and capacitor electrodes 120, 150 are formed at one time, and the whole is fixed on the magnetic metal plate 10. All capacitor capacities are. ,
Using the substrate itself as a dielectric, the capacitor electrode 12
0,150 and the ground conductor 3,4. Furthermore, the extension of the positive reactance inductor 130 is
The short-circuit conductor strip 130' has a length of 1/4 wavelength of the operating frequency, and the inductor 13
0 is equivalently shorted to ground at this connection.
Of course, without using this, it is also possible to actually perform the grounding short circuit using through holes and side metallization. Further, the electrode 120' is a capacitance adjusting electrode. In this example, a ferrimagnetic plate and a dielectric substrate are used as a single substrate, and microwave ICs are installed on the upper and lower surfaces.
Since conductive patterns and the like are formed using technology, it is suitable for mass production and can easily ensure accuracy that can be used up to high frequencies. Further, in this embodiment, it is completely unnecessary to short-circuit between the upper and lower conductors, and the number of manufacturing steps can be significantly reduced. In particular, if a Ba-TiO ₂ ceramic plate is used as the dielectric substrate, the electrode and line lengths can be reduced, which is very effective. As in each of the above embodiments, the present invention provides an ultra-high frequency isolator that is small, economical, and has a simple structure. However, by mixing the configurations of each embodiment, for example, a lumped constant capacitor can be used as a negative reactance circuit. It goes without saying that an equally good isolator can be realized by using a strip line for the positive reactance circuit, or by using the reverse configuration.

[Brief explanation of the drawing]

FIG. 1 shows an isolator showing the structure of a conventional isolator, in which 1 is a dielectric substrate, 2 is a ferrimagnetic plate, 3 is a ground conductor, 4 is a junction electrode, 5 is a permanent magnet, 11 is a main line, 12, 13 is a branch line. Figures 2, 3, and 4 are characteristic diagrams for explaining the principle of the present invention, and Figure 5 is a joint model diagram a and its equivalent circuit diagram b, which are also used for explanation.
It is. 6 and 7 are plan views showing the first and second embodiments of the present invention, respectively, in which 1 is a dielectric substrate, 2 is a ferrimagnetic material, 4 is a bonding electrode, 11
1 is an input/output main line, 12 and 13 are branch lines, 14 is a series line, 15 is a parallel line, and 20 is a connector. FIG. 8 shows a third embodiment of the present invention, in which a and b are perspective views of a magnetic circuit section and a main circuit section, respectively, and c is an equivalent circuit diagram of the main circuit section.
In the figure, 10 is a magnetic metal plate, 3 is a ground conductor,
2 is a ferrimagnetic plate, 4 is a joining electrode, 30 is a ground terminal, 130 and 140 are lumped constant inductors, 1
20, 150 is a lumped constant capacitor, 200 is an input/output terminal, 150 is a permanent magnet, 51 is a top cover, 10
1 is a set screw hole, 101' is a set screw, 102,
102' is a mounting hole. 9 and 10a and 10b are diagrams showing the main circuit portions of the fourth and fifth embodiments of the present invention, respectively;
All components that are the same as those in the figures are indicated using the same numbers. 1 is a dielectric substrate, 3' is a grounding conductor, 13
0' is a shorting conductor strip.

Claims (1)

[Claims] 1. On the ground plane, there is a ferrimagnetic plate magnetized by a magnetic field perpendicular to the plane, and on the upper surface thereof, there are planes parallel to the ground plane, spaced apart at an angular interval of 90 degrees, and arranged in the order of the angular direction. The second and fourth openings of a magnetic circuit junction in which a junction electrode having four openings (second, third, and fourth) are arranged have positive electrodes whose absolute value is equal to the magnitude of the junction impedance. By applying a load to a negative reactance circuit and setting the strength of the magnetic field to a predetermined value, the entire joint including the ferrimagnetic plate is set to a magnetic resonance state, and the first and third openings are An isolator characterized in that an impedance conversion circuit having a predetermined conversion ratio according to the impedance of the junction is connected to serve as an input/output port.