JPH0465562B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a filter device using Ferrimagnetic resonance.

Background technology and its problems Yttrium/iron with good crystallinity has been developed by liquid phase epitaxial growth of a garnet magnetic thin film on a gadolinium gallium garnet (GGG) substrate, which has become popular in recent years through the development of magnetic bubble memory elements.・It is possible to produce garnet (YIG) thin films. This YIG thin film is processed into a circular or rectangular shape by selective etching.
By utilizing this Ferrimagnetic resonance, a microwave device can be constructed. In this case, ordinary photolithography technology can be used, so processability is excellent, and since a large number of elements can be obtained from one GGG substrate, mass production is excellent. Furthermore, since it is a thin film material, it has the advantage that it can be easily integrated into a microwave integrated circuit (MIC) as a transmission line such as a microstrip line.

FIG. 1 is an example of a conventional band-pass filter using a YIG thin film converted into an MIC. Reference numeral 1 denotes an alumina substrate, on the back surface of which a ground conductor 2 is adhered, and on the surface thereof parallel input and output transmission lines (microstrip lines) 3 and 4 are formed. and 4 are connected to the ground conductor 2. 2 on the surface of this alumina substrate 1
A GGG substrate 7 having two circular YIG thin films 5 and 6 is brought into contact. Both YIG thin films 5 and 6 are placed on the GGG substrate 7 so as to be perpendicular to the input/output transmission lines 3 and 4.
A coupling transmission line (microstripline) 8 for coupling is formed and both ends of the transmission line 8 are connected to the ground conductor 2. First YIG thin film 5
is placed at a position where the input transmission line 3 and the coupling transmission line 8 intersect, and the second YIG thin film 6 is placed at a position where the output transmission line 4 and the coupling transmission line 8 intersect. In order to steeply increase the insertion loss outside the passband, the distance between the two YIG thin films 5 and 6 is selected to be equal to λ/4 (1/4 wavelength) at the center frequency of the passband. be.

By the way, in a bandpass filter, it is desirable to increase the isolation between the input and output terminals in the stopband as much as possible, but in the bandpass filter shown in Figure 1, the isolation is not sufficiently large due to two reasons. I can't take it. The first cause is
The electrical length from the tip short circuit to the point where the two lines intersect becomes longer as the frequency increases, and as it approaches λg/4, the electric field at the point of intersection becomes stronger, resulting in larger capacitive coupling between the lines. It is what happens. The second cause is direct coupling between input and output lines. This is because, as shown in Figure 4, the high-frequency magnetic field 9 of the electromagnetic waves propagating through the microstrip line is widely distributed in a loop shape to a considerable distance from the line in a plane perpendicular to the propagation direction. This is because the lines are inductively coupled.

Of these two causes, the first cause does not pose a problem if the frequency used as a filter is not too high because the electrical length from the tip short circuit to the point where the two lines intersect can be ignored. Therefore, in this case, the isolation of the input and output of the filter is
It is determined by the magnitude of direct coupling between input and output lines, which is the cause of To reduce inductive coupling between input and output lines, make the input and output lines face each other or connect them to each other.
Although it is conceivable to arrange them so that they form an angle of 90 degrees, it is not always easy to adopt such a configuration due to the restriction that it is necessary to short-circuit the tips of the input/output lines and both ends of the coupling line. Another way to reduce inductive coupling is to increase the distance between the input and output lines, which can be done by changing the distance between the two YIG films from λ/4 to 3λ/4. However, this method increases the size of the element and, accordingly, also increases the size of the magnet for applying the DC magnetic field, making it very disadvantageous in terms of size and economy.

Purpose of the Invention In view of the above points, the present invention provides a filter device using Ferri magnetic resonance that can improve isolation between input and output terminals in the stopband with a simple configuration. .

Summary of the Invention The present invention provides a ground conductor on one main surface of at least a first dielectric substrate of first and second dielectric substrates facing each other, and a ground conductor of the first dielectric substrate. first and second striplines are formed in parallel on the main surface of the dielectric substrate, and these first and second striplines are connected to the ground conductor of the second dielectric substrate. A third stripline is formed in a direction intersecting the first and second striplines on the main surface without a strip line and connected to the ground conductor, and the first and third striplines are connected to the ground conductor. A first magnetic resonance device electromagnetically coupled to these striplines is provided at the intersection of the second and third striplines, and a second magnetic resonance device electromagnetically coupled to these striplines is provided at the intersection of the second and third striplines. A magnetic resonance apparatus is provided, and a ground conductor is provided on the outside in parallel and close to the first and second striplines. In this invention, the inductive coupling between the input and output striplines is suppressed to a very low level, and the isolation between the input and output terminals of the filter is improved.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 2 and 3.

In the present invention, two circular YIG thin films 5 and 6 facing each other are formed on one main surface of the GGG substrate 7 by liquid phase epitaxial growth technology and selective etching technology. On the other hand, a dielectric substrate such as an alumina substrate 1 is provided, a ground conductor 2 is deposited on the back surface of the substrate, and an input microstrip line 3 and an output microstrip line 4 are deposited on the surface of the substrate, The respective ends of both microstrip lines 3 and 4 are connected to the ground conductor 2. On the surface of this alumina substrate 1, the GGG substrate 7 is arranged so that its respective YIG thin films 5 and 6 are in contact with the corresponding input microstrip line 3 and output microstrip line 4.
Then, on the other surface of the GGG substrate 7, a coupling microstrip line 8 for coupling both YIG thin films 5 and 6 is arranged so as to be perpendicular to the input/output microstrip lines 3 and 4 and across both YIG thin films 5 and 6. Both ends of the coupling microstrip line 8 are connected to the ground conductor 2. A ground conductor, ie, a metal wall 10, is placed on the side surface of the alumina substrate 1 and the GGG substrate 7, close to the input and output microstrip lines 3 and 4, respectively, and parallel to these strip lines.

According to such a filter device, YIG is installed at the intersection of the input and coupling microstrip lines 3 and 8.
In addition to providing a thin film 5, a YIG thin film 6 is provided at the intersection of the output and coupling microstrip lines 4 and 8, and furthermore, a YIG thin film 6 is provided at the intersection of the input and output strip lines 3 and 4.
Since the metal wall 10 is provided on the outside parallel to and close to the filter, the isolation between the input and output terminals of the filter can be easily improved without increasing the element size. The reason for this is that the metal wall 10 allows the high-frequency magnetic field 9 of the electromagnetic waves propagating through the input/output microstrip lines 3 and 4 to be concentrated relatively close to the microstrip lines 3 and 4, as shown in FIG. , This is because it becomes possible to suppress the inductive coupling between the input and output microstrip lines 3 and 4 to a very low level.

FIGS. 6 and 7 are frequency-insertion loss characteristic diagrams showing isolation between input and output, respectively. FIG. 6 shows the case of a conventional filter device, and FIG. 7 shows the case of the filter device of the present invention in which a metal wall with a height of 3 mm is placed. As can be seen from this characteristic diagram, the isolation between the input and output terminals of the filter is improved from 40 dB to 50 dB in the filter of the present invention in which a metal wall is placed compared to the conventional filter.

In the above example, a microstrip line was used as the transmission line, but the present invention can be similarly applied to other strip lines or suspended lines.

Effects of the Invention According to the present invention described above, the first magnetic resonance device electromagnetically coupled to the first and third striplines is provided at the intersection of the first and third striplines, and the first magnetic resonance device is provided at the intersection of the first and third striplines. A second magnetic resonance device electromagnetically coupled to the striplines is provided at the intersection of the striplines, and a grounding conductor is provided outside parallel to and adjacent to the first and second striplines. Therefore, the inductive coupling between the input and output striplines can be suppressed to a very low level, and the isolation between the input and output terminals of the filter can be easily improved using the magnetic resonance thin film.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an example of a conventional filter device, Figs. 2 and 3 are a plan view and a side view of a filter device according to the present invention, and Figs. 4 and 5 are provided for explanation of the present invention, respectively. FIG. 6 is a frequency-insertion loss characteristic diagram of a conventional filter device, and FIG. 7 is a frequency-insertion loss characteristic diagram of the filter device of the present invention. 1 is an alumina board, 2 is a ground conductor, 3 is an input stripline, 4 is an output stripline,
5 and 6 are YIG thin films, 7 is a GGG substrate, 8 is a strip line for coupling, and 10 is a metal wall.

Claims (1)

[Claims] 1. A grounding conductor is provided on one main surface of at least the first dielectric substrate of the first and second dielectric substrates facing each other, and a grounding conductor is provided on the main surface of the first dielectric substrate on which the grounding conductor is not provided. A first and a second stripline are formed in parallel, and the first and second striplines are connected to the ground conductor, and the main surface of the second dielectric substrate on which the ground conductor is not provided is connected to the ground conductor. a third strip line in a direction intersecting the first and second strip lines;
A stripline is formed and connected to the ground conductor, and a first magnetic resonance device is provided at the intersection of the first and third striplines and is electromagnetically coupled to the stripline. A second magnetic resonance device electromagnetically coupled to the second and third striplines is provided at the intersection of the second and third striplines, and a ground conductor is provided on the outside in parallel and close to the first and second striplines. A filter device comprising: