JP2906863B2 - Stripline dual mode filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small, low-cost stripline dual mode filter used for communication equipment and measuring equipment in the UHF to SHF band.

[0002]

2. Description of the Related Art As a strip line ring resonator filter, a one-wavelength strip line ring resonator or the like is usually used to reduce radiation loss, but it has a drawback that the shape is large even if the loss is small. In order to solve the shortcomings of this one-wavelength stripline ring resonator filter,
A dual resonator that excites two orthogonal modes in one resonator
Mode filters have also been proposed, but have not been put to practical use.

A conventional stripline dual mode filter will be described below. FIG. 5 is a configuration diagram of a conventional stripline dual mode filter. This is a 1991 IEEE International Microwave Symposium Dig by JACurtis and others.
est (1991 EE International Microwave Symposium Digest), pp.443-446 (N-1).

In FIG. 5, reference numeral 201 denotes a single-wavelength (360 ° electrical length) stripline ring resonator;
03 is an input / output line, 204 and 205 are gap capacitances for realizing input / output coupling capacitance, and 206 is a strip line stub having an open end. The electrical length between the input and output is 90 °, the strip line stub 206 with the open end and the input and output line 20
It is arranged so that the electrical length is 135 ° to the center of 2,203.

The operation of the strip line dual mode filter configured as described above will be qualitatively described below with the concept of a traveling wave.

First, a traveling wave propagated from an input line 202 is electrically coupled to a one-wavelength stripline ring resonator 201 via a gap capacitance 204 for realizing a coupling capacitance, and generates a strong electric field near the input line. This electric field propagates in the stripline ring resonator 201 in the clockwise and counterclockwise directions as a traveling wave.

First, consider a traveling wave counterclockwise. The traveling wave reaches the vicinity of the output line 203 after undergoing a phase change of 90 °, but is not coupled to the output line 203 here because the electric field is minimized. 1 more than this
When the vehicle advances by 35 °, it reaches the position of the strip line stub 206 having the open end. Here, since a discontinuous portion exists in the line, a part of the line becomes a reflected wave, and the rest propagates to the vicinity of the input line 202 and passes through the gap capacitance 204 to the input line 202.
To rejoin. Now, the reflected wave from the open-end stripline stub 206 recedes by 135 °, and the output line 203
However, since the phase difference is 270 ° round trip, the electric field is maximized here and electric field coupling occurs, and a traveling wave propagates to the output line 203. Similarly, as for the traveling wave in the clockwise direction, only the reflected wave from the strip line stub 206 whose tip is open is propagated to the output line 203. Since the magnitude of the reflection is remarkable when the discontinuous portion is large, the magnitude of the traveling wave propagating by the line length of the strip line stub 206 having the open end can be controlled. When this operation is viewed as a resonator, in the case of the configuration shown in FIG. 5, there are two orthogonal modes in the resonator, and the degree of coupling between the two resonance modes can be controlled by the structure of the strip line stub 206 having an open end. Means things.

That is, it can be considered that it operates as a dual mode filter and one resonator has a function corresponding to a two-stage filter, and it can be said that the configuration contributes to downsizing.

[0009]

However, in the above configuration, the degree of coupling, that is, the pass band width of the filter is adjusted only by the strip line stub having the open end, and the pass band cannot be made large. Therefore, the application area of the filter is limited. However, there is a problem that the configuration of the multistage filter is difficult.

An object of the present invention is to provide a strip line dual mode filter which has a wide band, allows easy configuration of a multi-stage filter, and allows easy combination of active elements. And

[0011]

In order to achieve this object, a strip line dual mode filter according to the present invention uses an inductor for input and output and uses a strip line such as a stub or the like for a strip line constituting a strip line ring resonator. In addition to a uniform line without a continuous portion, a feedback circuit is provided inside or outside the strip line ring resonator,
Exciting two spatially orthogonal resonance modes, or forming a stripline loop resonator having a parallel coupling part with a uniform line without a discontinuous portion such as a stub, and two resonance modes are formed by parallel coupling. It has a configuration in which a dual mode filter can be realized by excitation.

[0012]

According to this construction, two orthogonally connected two which are not connected to each other
Since the resonator can be excited in two modes, a dual mode filter using one and a plurality of stripline ring resonators can be realized. In addition, the degree of coupling can be controlled by the feedback circuit, and the versatility of the circuit can be adopted, so the degree of freedom in filter design is expanded. This can be easily performed, and the effect of suppressing harmonics can be expected as compared with the case where a capacitor is used for using an inductor or the like for input and output.

[0013]

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 101 denotes a one-wavelength (360 ° electrical length) stripline ring resonator;
Numeral 03 denotes an input / output inductor connected to positions A and B separated by 90 ° in electrical length from each other on the stripline ring resonator 101, 104 and 105 denote input / output terminals of the input / output inductors 102 and 103, and 106 denotes a stripline. This is a feedback circuit connected between positions C and D on the ring resonator 101. Positions A, B, C, and D are adjacent to each other.
And the interval is 90 degrees in electrical length. A connection point between the input / output inductances 102 and 105 and the feedback circuit 106 is a strip line ring resonator 101.
Connected to the outer and inner ends, but with an electrical length of 9
For every 0 °, the stripline ring resonator 10
1 may be connected to the center.

The operation of the stripline dual mode filter configured as described above will be described with reference to FIG.

First, when the input / output terminal 104 is excited, the input / output terminal 104 is coupled to the stripline ring resonator 101 via the input / output inductor 102 by electric field coupling. The electric wave of the wave propagating at the position A on the stripline ring resonator 101 has the maximum electric field at the position C at an electric length of 180 ° and propagates to the feedback circuit 106. Similarly, the wave excited at the position D propagates to the position B, and propagates to the output of the input / output terminal 105 via the input / output inductor 103.

In B and D, which are 90 ° in electrical length from position A on stripline ring resonator 101,
The electric field is minimized and no waves propagate. Similarly, when the position D is excited, the traveling wave propagates to the position B but does not propagate to the positions A and C. Therefore, it can be seen that the one-wavelength stripline ring resonator 101 has two resonance modes that are not coupled to each other.

When the position A is excited and the wave propagated to the position C is applied to the position D via a suitable feedback circuit 106, the traveling wave propagates only to the position B. Therefore, a circuit in which a signal is propagated in only one direction such that a signal input from the position A is output to the position B via the positions C and D can be configured. That is, when the terminal 104 is used as an input terminal, the terminal 105 becomes an output terminal, and a two-stage filter can be realized using one strip line ring resonator. The pass band width of the filter is mainly determined by the feedback circuit 106. Various circuits such as a capacitance, an inductor, a strip line, and an amplifier circuit can be used for the feedback circuit 106. Needless to say, the feedback circuit 110 specifically shown here can also be realized by a combination of these circuits. In FIG. 2, the inductor in FIG. 1 is constituted by a strip line having a higher characteristic impedance than the input / output lines 110 and 111 or the characteristic impedance of the single-wavelength strip line ring resonator.
The operation is similar to the operation shown in FIG.

The strip line dual according to the present embodiment
The attenuation of a conventional stripline dual mode filter due to capacitive coupling is shown in comparison with (Table 1) with the same circuit configuration as the attenuation at the harmonic of the mode filter.

[0020]

[Table 1]

This table shows the results of circuit analysis, and the capacitance and inductor are analyzed as ideal elements.
Actually, the effect as shown in (Table 1) cannot be expected,
Obviously, the stripline dual mode filter according to this embodiment has an excellent effect in terms of harmonic suppression.

As described above, by adopting the configuration shown in FIG. 1, the strip line ring resonator 101 is a uniform line, so that almost perfect quadrature mode excitation can be realized, and various circuits are selected as feedback circuits. The coupling between modes can be freely controlled by an external circuit, and the use of an inductor or a strip line for input and output can provide an excellent effect of suppressing harmonics as compared with capacitive coupling.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to FIG.

In FIG. 3, reference numeral 107 denotes a one-wavelength (360 ° electrical length) stripline loop resonator.
At 7A, a parallel coupling portion is formed. 102, 10
3 is a section 1 in the stripline loop resonator 107
07A, the input / output inductors 104, 105 connected to the ends of the opposing lines
103 is an input / output terminal. FIG. 3 is different from FIG. 1 in that a strip line dual mode filter is configured using a parallel coupling section by a section 107A instead of the feedback circuit 106. The input / output inductor 10
The positions A and B connecting the terminals 2 and 103 are separated by 90 ° in electrical length, and their terminals are symmetrical with respect to a center line XX ′ parallel to the parallel coupling portion.

The operation of the stripline dual mode filter configured as described above will be described with reference to FIG.

First, the strip line loop resonator 107
At position B, which is 90 degrees in electrical length from position A above, the electric field is minimized , so that no wave propagates to position B. On the other hand, the wave excited at the position A is clockwise and counterclockwise in the section 1 in the stripline loop resonator 107.
07A are respectively electromagnetically coupled at opposing parallel coupling portions,
There is a mode in which the electric field is maximized at the terminal B. Therefore, a single-wavelength stripline ring resonator has two resonance modes that are not coupled to each other.

As described above, by adopting the configuration shown in FIG. 3, the strip line ring resonator 101 is a uniform line, so that almost perfect quadrature mode excitation can be realized, and various circuits are selected as feedback circuits. The coupling between modes can be freely controlled by an external circuit, and the use of inductors or strip lines for input and output can provide an excellent effect of suppressing harmonics as compared with capacitive coupling. In FIG. 4, the inductor in FIG. 3 is constituted by a strip line having a higher characteristic impedance than the input / output lines 110 and 111 or the characteristic impedance of the single-wavelength strip line ring resonator, as in FIG. The operation is the same as the operation shown in FIG.

As described above, the strip line dual
An excellent effect of operating as a mode filter, controlling the pass bandwidth by the line spacing, and suppressing harmonics as compared to capacitive coupling by using inductors or strip lines for input and output is obtained.

In the first and second embodiments, the strip line dual mode filter has been described. However, the line to be used may be a microstrip line or a laminated line such as a triplate structure and incorporated in the inside. It may be configured.

[0030]

As described above, according to the present invention, an inductor is used for input and output, and a strip line constituting a strip line ring resonator is constituted by a uniform line having no discontinuous portion such as a stub. A feedback circuit is provided inside or outside the ring resonator, and a spatially orthogonal
Exciting two resonance modes, or forming a strip line loop resonator having a parallel coupling part with a uniform line without a discontinuous portion such as a stub, and exciting two resonance modes by parallel coupling, Since the resonator can be excited in two orthogonal modes that are not coupled, a dual mode filter using one and a plurality of stripline ring resonators can be realized. In addition, the degree of coupling can be controlled by the feedback circuit, and the versatility of the circuit can be adopted, so the degree of freedom in filter design is expanded. Compared to the case where a capacitor is used to use an inductor and the like for input and output.
The effect of suppressing harmonics can be expected.

[Brief description of the drawings]

FIG. 1 is a plan view of a stripline dual mode filter according to a first embodiment of the present invention.

FIG. 2 is another plan view of the stripline dual mode filter.

FIG. 3 is a plan view of a stripline dual mode filter according to a second embodiment of the present invention.

FIG. 4 is another plan view of the stripline dual mode filter.

FIG. 5 is a plan view of a conventional stripline dual mode filter.

[Explanation of symbols]

 101, 107 Stripline ring resonators 102, 103 I / O inductors 104, 105 I / O terminals 106 Feedback circuits 108, 109 Striplines 110, 111 I / O lines

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01P 1/20-1/219 H01P 7/00-7/10

Claims (7)

(57) [Claims] An electric length of a line is 360 °. Four terminals are provided on the line of a single-wavelength strip ring resonator at an electric length of 90 °, and an input inductor is connected to a first terminal. A second terminal located at an electrical length of 180 ° from the first terminal and one of a third terminal and a fourth terminal located at an electrical length of 90 ° are connected via a feedback circuit and output to the other terminal. Stripline dual mode filter with inductor. 2. The strip line dual mode according to claim 1, wherein the inductor used for input / output is constituted by a strip line having a higher characteristic impedance than the characteristic impedance of the strip line ring resonator and the input / output line. ·filter. 3. The strip line dual mode filter according to claim 1, wherein the feedback circuit is constituted by a strip line. 4. The strip line dual mode filter according to claim 1, wherein the feedback circuit is constituted by a lumped constant element of a capacitance and an inductor. 5. The strip line dual mode filter according to claim 1, wherein an amplifier circuit is provided in the feedback circuit. 6. An electric line provided with a parallel coupling portion has an electric length of about 3
For a single-wavelength stripline ring resonator having a uniform line width at 60 °, two terminals for connecting the input and output inductors are provided at a position separated by 90 ° in electrical length, and the terminals are parallel to the parallel coupling line. A strip-line dual mode filter characterized by being symmetrical with respect to a center line. 7. An electric line having a parallel coupling portion having an electric length of about 3
For a single-wavelength stripline ring resonator having a uniform line width at 60 °, two striplines having a high characteristic impedance compared to the single-wavelength stripline ring resonator and the characteristic impedance of the input / output line are connected. A strip line dual mode filter wherein terminals are provided at an electrical distance of 90 ° and the terminals are symmetrical with respect to a center line parallel to the parallel coupling line.