JP2538164B2 - 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 compact and low-cost stripline dual mode filter used for communication devices and measuring instruments in the UHF to SHF band.

[0002]

2. Description of the Related Art A stripline ring resonator filter usually uses a one-wavelength stripline ring resonator or the like in order to reduce radiation loss, but it has a drawback that it has a large shape even if the loss is small. To solve the shortcomings of this one wavelength stripline ring resonator filter,
Dual excitation of two quadrature modes in one resonator
A mode filter has also been proposed but has not been put to practical use.

A conventional stripline dual mode filter will be described below. FIG. 8 is a block diagram of a conventional stripline dual mode filter. This is a 1991 IEEE International Microwave Symposium Digest by JACurtis et al.
gest, pp.443-446 (N-1)) ".

In FIG. 8, 150 is a strip line ring resonator of one wavelength (electrical length of 360 °), 151, 1
Reference numeral 52 is an input / output line, 153 and 154 are gap capacitances that realize input / output coupling capacitances, and 155 is a strip line stub with an open tip. The electrical length between the input and output is 90 °, and the stripline stub 155 with open end and the input / output line
It is arranged so that the electrical length to the center of 1, 152 is 135 °.

The operation of the stripline dual mode filter having the above-described structure will be qualitatively described below with the concept of a traveling wave. First input line 1
The traveling wave propagated from 51 is field-coupled to the one-wavelength stripline ring resonator via the gap capacitance 153 that realizes the coupling capacitance, and a strong electric field is generated near the input line. This electric field propagates in the clockwise and counterclockwise directions as a traveling wave. First, consider the counterclockwise traveling wave. This traveling wave undergoes a 90 ° phase change and reaches the vicinity of the output line, but since the electric field is minimum here, the output line 1
Not bound to 52. When it goes further 135 ° from this, it reaches the position of the stripline stub 155 with the open end. Here, since the line has a discontinuous portion, a part thereof becomes a reflected wave, and the rest propagates to the vicinity of the input line 151 and is coupled to the input line 151 via the gap capacitance 153. The reflected wave at the open-ended stripline stub 155 is 135
Retreat to reach the vicinity of output line 152, but return 27
Since the phase difference is 0 °, the electric field is maximized here and electric field coupling occurs, and the traveling wave propagates to the output line 152. Similarly, as for the traveling wave in the clockwise direction, only the reflected wave at the strip line stub 155 having the open tip is output line 15.
2 is propagated. The magnitude of the reflection is remarkable when the discontinuity is large, so the stripline stub 1 with an open tip is used.
The magnitude of the traveling wave propagating with the line length of 55 can be controlled.
Considering this operation as a resonator, in the case of the configuration of FIG. 8, there are two orthogonal modes in the resonator, and the degree of coupling between these two resonant modes is the open-ended stripline stub 1.
It means that it can be controlled by the structure of 55. That is, dual
It operates as a mode filter, and one resonator has 2
It can be considered that it has a function corresponding to the stage filter, and it can be said that this configuration contributes to downsizing.

[0006]

However, in the above configuration, the coupling degree, that is, the pass band width as a filter is adjusted only by the strip line stub having an open tip, and the pass band cannot be made large, so that the application area of the filter is limited. There is a problem that it is difficult to construct a multistage filter.

The present invention solves the above-mentioned problems of the prior art, and provides a strip line dual mode filter having a wide band, a multistage filter having a simple structure, and active elements can be easily combined. To aim.

[0008]

To achieve this object, a stripline dual-mode filter according to the present invention has a uniform stripline that does not have discontinuities such as stubs in the stripline that constitutes a stripline ring resonator. A stripline dual-mode filter can be realized by using a line and by providing a phase shift circuit inside or outside the stripline ring resonator to excite two spatially orthogonal resonance modes. are doing.

[0009]

[Function] With this configuration, the two orthogonal
Since the resonator can be excited in one mode, 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 phase shift circuit, and the versatility of the circuit can be adopted, so the degree of freedom in filter design is expanded. Easy to apply.

[0010]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of a stripline dual mode filter according to a first embodiment of the present invention.

In FIG. 1, 101 is a strip line ring resonator of one wavelength (electrical length of 360 °), 106-1.
09 is the electrical length, and the coupling capacity is arranged every 90 °, 10
Reference numerals 2 and 105 are input / output terminals, 103 and 104 are connection terminals with a phase shift circuit, and 110 is a phase shift circuit. Phase shift circuit 110
Are connected by connection terminals 103 and 104.

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

First, when the input terminal 102 is excited, it is coupled to the strip line ring resonator 101 by electric field coupling. The wave propagating to the point A on the strip line ring resonator 101 has the maximum electric field at the point C at an electrical length of 180 ° and propagates to the connection terminal 104 via the coupling capacitance 108. Point A on stripline ring resonator 101
Point is the electrical length of 90 ° position from the B, electrodeposition in D
The field becomes the minimum and does not propagate to the connection terminal 103 and the output terminal 105. Similarly, when the connection terminal 103 is excited, the traveling wave propagates to the output terminal 105 but does not propagate to the input terminal 102 and the connection terminal 104. Therefore, the one-wavelength stripline ring resonator 101 is not coupled to each other.
It can be seen that there are two resonance modes.

When the input terminal 102 is excited and the wave propagating to the connection terminal 104 is applied to the connection terminal 103 via an appropriate phase shift circuit 110, this traveling wave is output.
Only propagate to 5. Therefore, a signal input from the input terminal 102 is output to the output terminal 105 via the connection terminal 104 and the terminal 103, which constitutes a circuit in which the signal is propagated in only one direction. That is, when the input terminal 102 is used as the input terminal, the output terminal 105 serves as the output terminal, and a two-stage filter can be realized by using one stripline ring resonator. The pass band width of the filter is mainly determined by the phase shift circuit 110 and the coupling capacitors 107 and 108 connecting the phase shift circuit 110. Further, various circuits can be adopted as the phase shift circuit 110, and a specific example of the present invention will be described below with reference to the drawings.

In FIG. 2, the phase shift circuit 110 of FIG. 1 is specifically realized by a strip line 111.
In the case of further downsizing with this configuration, although the strip line 111 is provided outside the strip line ring resonator 101 in FIG. 2, the strip line 111 may be provided inside the strip line ring resonator 101.

Further, in FIG. 3, the phase shift circuit 11 of FIG.
0 is specifically realized by a T-type high-pass filter. Here, the series capacitances on both sides of the T-type high-pass filter are replaced by the coupling capacitances 107 and 108, and the parallel inductor 112 is used.
Uses only chisel. With this configuration, it is possible to reduce the size and simultaneously reduce the attenuation in the low frequency range.

Further, in FIG. 4, the phase shift circuit 1 of FIG.
10 is realized by a π-type low-pass filter.
Here, the parallel capacitors 113 and 115, the series inductor 11
4 realizes a π-type low-pass filter. With this configuration, it is possible to reduce the size and at the same time improve the attenuation amount in the high frequency range.

Further, in FIG. 5, the phase shift circuit 11 of FIG.
0 is realized by the amplifier 116 and the strip line 117 for phase correction by the strip line. With this configuration, a filter having an amplification function, that is, a two-stage tuned amplifier can be realized. Usually the amplifier 11
Since 6 has a very small reverse transfer characteristic, in this configuration, there are no direct couplings between the two orthogonal resonance modes and independent 2
Since it operates as one single-stage filter, the first-stage fill
The bandwidth of the amplifier and the narrow band of the next stage
F can be improved and can be applied to the front end part of the receiver.

It goes without saying that the phase shift circuit 110 shown concretely with reference to FIGS. 2, 3, 4, and 5 can be realized by a combination of these circuits.

As described above, with the configuration shown in FIG. 1, since the stripline ring resonator 101 is a uniform line, almost perfect quadrature mode excitation can be realized, and the phase shift circuit 110 has various circuits. Can be selected, and coupling between modes can also be achieved by the phase shift circuit 110 and the coupling capacitance 10.
The excellent effect that it can be freely controlled by the external circuits 7 and 108 is obtained.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

In FIG. 6, reference numerals 121, 122 and 123 denote strip wavelength ring resonators having the same wavelength (electrical length of 360 °) as those shown in FIG. 1 and having coupling capacitances every 90 ° of electric length . 102 and 105 are input / output terminals, 12
Reference numerals 4, 125 and 126 are phase shift circuits. Here, for the sake of explanation, it is assumed that points on the line connecting the coupling capacitance from the strip line ring resonator are represented by points A, B, C and D as shown in FIG. The point C of the strip line ring resonator 121 and the point A of the strip line ring resonator 122, and the point C of the strip line ring resonator 122 and the point A of the strip line ring resonator 123 are connected by a coupling capacitance to form a strip line. The point B of the ring resonator 121 and the point B of the strip line ring resonator 122, the point D of the strip line ring resonator 122 and the point D of the strip line ring resonator 123 are connected by phase shift circuits 126 and 127, respectively. A point B and a point C of the strip line ring resonator 123 are connected by a phase shift circuit 124.

The operation of the multistage stripline dual mode filter constructed as described above will be described below.

First, the waves excited at the input terminal 102 are A of the strip line ring resonator 121, C of the strip line ring resonator 121, and the strip line ring resonator 1.
22 A, strip line ring resonator 122 C, strip line ring resonator 123 A, strip line ring resonator 123 C, strip line ring resonator 123 B, strip line ring resonator 123 D,
Strip line ring resonator 122 D, strip line ring resonator 122 B, strip line ring resonator 121 B, strip line ring resonator 121 D
Are transmitted in this order and are output to the output terminal 105. The waves propagating as described above are excited in orthogonal modes in each strip line ring resonator.

As described above, the strip line ring resonators are arranged on a straight line, and the coupling of each strip line ring resonator is provided with a coupling capacitance or a phase shift circuit. It operates in quadrature mode and can realize a 6-stage filter with three stripline ring resonators. In addition, the phase shift circuit φ ₁ ~
φ ₃ can be realized by the circuits of the specific examples shown in the first embodiment and a combination thereof. Furthermore, an elliptic function type filter can be realized by appropriately designing the phase shift circuit. Although the embodiment shown in FIG. 6 is an example using three stripline ring resonators, it goes without saying that a dual mode filter can be realized regardless of the number.

(Third Embodiment) A third embodiment of the present invention will be described below with reference to the drawings. FIG. 7 shows a stripline dual mode circuit according to a third embodiment of the present invention.
It is a top view of a filter.

In FIG. 7, 131 and 132 are strip line ring resonators of one wavelength (electrical length of 360 °),
133 and 134 are 90 degree hybrid, 135 and 139
Is an input / output terminal, and 136 to 138, 140 to 142 are 90
The hybrid terminals 143 and 144 are phase shift circuits. The stripline ring resonators 131 and 132 connect the phase shift circuits 143 and 1 so as to connect the respective resonance modes.
Connected at 44. In the stripline ring resonator, when the terminal 135 is used as an input terminal and the terminal 139 is used as an output terminal, the 90 ° hybrid 133 functions as a 90 ° distributor and 134 functions as a 90 ° combiner.

The operation of the stripline dual mode filter constructed as described above will be described below.

Now, when the input terminal 135 is excited, a wave is equally distributed by the 90 ° hybrid 133 to the hybrid terminals 136 and 137 with a phase difference of 90 ° and propagates to the strip line ring resonator 131 to cause two orthogonal mode resonances. Which also causes the stripline ring resonator 132 to excite the orthogonal mode resonance.
The wave propagating through the strip line ring resonator 132 is output to the hybrid terminals 140 and 141, combined by the 90 ° hybrid 134, and output from the output terminal 139. In this case, stripline ring resonators 131, 1
The dual mode filter using 32 operates as a two-stage two-channel filter.

As described above, a plurality of one-wavelength strip line ring resonators having four terminals capacitively coupled at an electrical length of 90 ° are used, two adjacent terminals are connected, and a 90 ° hybrid is provided on both sides. By providing the filter, it becomes possible to configure a 2-channel filter, and a high power filter is provided.
It can be applied as a filter. In addition, the phase shift circuits 143 and 144
By using a power amplifier with uniform phase characteristics and amplitude characteristics, it can be used as a filter for a large power amplifier in parallel operation.

Although the strip line dual mode filter has been shown in the first to third embodiments, the line to be used has a laminated structure such as a microstrip line or a triplate structure and is incorporated inside. It may be constituted by a track.

[0032]

As described above, the present invention utilizes orthogonal resonance modes by connecting a phase shift circuit to a one-wavelength stripline ring resonator having terminals capacitively coupled at every 90 ° electrical length. It is possible to realize an excellent stripline dual mode filter with high performance and wide band by selecting various circuits for the phase shift circuit.

[Brief description of 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 a detailed plan view of a main part of the stripline dual mode filter.

FIG. 3 is a detailed plan view of a main part of the stripline dual mode filter.

FIG. 4 is a detailed plan view of a main part of the stripline dual mode filter.

FIG. 5 is a detailed plan view of a main part of the stripline dual mode filter.

FIG. 6 is a plan view of a stripline dual mode filter according to a second embodiment of the present invention.

FIG. 7 is a plan view of a stripline dual mode filter according to a third embodiment of the present invention.

FIG. 8 is a plan view of a conventional stripline dual mode filter.

[Explanation of symbols]

101, 121, 122, 123, 131, 132 One-wavelength stripline ring resonators 102, 105, 135, 139 Input / output terminals 103, 104 Connection terminals 106-109, coupling capacitances 110, 124, 125, 126, 143, 144 Phase shift circuit 111 Strip line 112 Parallel inductor 113, 115 Parallel capacitance 114 Series inductor 116 Amplification circuit 117 Phase correction strip line 133, 134 90 ° hybrid 136, 137, 138, 140, 141, 1429
0 ° hybrid terminal 150 One-wavelength strip line ring resonator 151, 152 Input / output line 153, 154 Gap capacitance 155 Strip line stub

Claims (9)

(57) [Claims] 1. A one-wavelength stripline ring resonator having an electrical length of 360 ° is provided with four terminals capacitively coupled at an electrical length of 90 ° on the line.
One terminal of the two terminals is used as an input terminal, and a terminal at an electrical length of 90 ° and a terminal at an electrical length of 180 ° from the input terminal are connected through a phase shift circuit, Is a stripline dual-mode filter characterized in that the remaining terminals at an electrical length of 270 ° are used as output terminals. 2. The stripline dual mode filter according to claim 1, wherein the phase shift circuit is formed of a stripline. 3. The stripline dual mode filter according to claim 1, wherein the phase shift circuit is composed of lumped constant elements of a capacitor and an inductor. 4. The stripline dual mode filter according to claim 1, wherein an amplifier circuit is provided in the phase shift circuit. 5. For a one-wavelength stripline ring resonator having an electrical length of 360 °, four terminals capacitively coupled at an electrical length of 90 ° are provided on the line, and each terminal is clockwise. Alternatively, S pieces of the strip line ring resonators (where S is an integer of 2 or more) in the case where the terminal 1, the terminal 2, the terminal 3, and the terminal 4 are arranged in the counterclockwise direction are arranged in the m-th (however,
And an odd number of stripline phosphorus satisfying 1 ≦ m <S
Terminal 3 of the resonator and the mth stripline phosphorus
(M + 1) th strip line adjacent to the resonator
While connecting the terminal 1 of the ring resonator,
The two are connected by the m-th phase shift circuit, and the n-th (but
And even number of strip line phosphorus satisfying 2 ≦ n <S
Terminal 3 of the resonator and the nth stripline phosphorus
(N + 1) th stripline adjacent to the resonator
While connecting the terminal 1 of the ring resonator,
4 is connected by the nth phase shift circuit and S is an odd number
The Sth stripline ring resonator is connected to the terminal 3 and the end.
Child 2, and the Sth strip if S is even
The line ring resonator connects the terminals 3 and 4 to the Sth phase shift circuit.
Stripline dual-mode filter characterized by being connected by a road . 6. The stripline dual mode filter according to claim 5, wherein the phase shift circuit is formed of a stripline. 7. The stripline dual mode filter according to claim 5, wherein the phase shift circuit is composed of lumped constant elements of a capacitor and an inductor. 8. The stripline dual mode filter according to claim 5, wherein an amplifier circuit is provided in the phase shift circuit. 9. For a one-wavelength stripline ring resonator having an electrical length of 360 °, four terminals capacitively coupled at an electrical length of 90 ° are provided on the line, and each terminal is clockwise. terminal 1, terminal 2, terminal 3, and terminal 4
In this case, S strip line ring resonators (where S is an integer of 2 or more) are arranged, and n of the strip line ring resonators adjacent to each other (where n is 1 ≦ n ≦).
In the (n-1) th and (n + 1) th which satisfy S-1, the terminal 3 of the nth stripline ring resonator and the terminal 2 of the (n + 1) th stripline ring resonator
Are connected via a first phase shift circuit, and the terminal 4 of the n-th strip line ring resonator and the terminal 1 of the (n + 1) th strip line ring resonator are connected via a second phase shift circuit. On the other hand, the first 90 ° hybrid terminal is connected to the two terminals 1 and 2 left in the first stripline ring resonator, and the terminal 3 of the Sth stripline ring resonator is connected, A stripline dual-mode filter characterized in that a second 90 ° hybrid terminal is connected to terminal 4.