JP4339819B2 - High pass filter - Google Patents

Description

  The present invention relates to a high-pass filter, and in particular, by using first and second strip lines made of a flat U-shaped conductor and a connection conductor provided in a through hole provided in a multilayer substrate. The present invention relates to a high-pass filter that greatly reduces the signal attenuation in the vicinity of a cutoff frequency.

  Conventionally, as a high-pass filter in which a high-frequency cutoff frequency is set in the UHF band near 1.0 to 2.0 GHz, a high-pass filter having a configuration in which a plurality of lumped constant circuit elements are combined and connected in a T shape, A high-pass filter having a configuration in which a plurality of lumped constant circuit elements are used as elements and a pair of mutually connected strip lines are combined and connected as shunt elements is known.

  FIG. 4 is a circuit diagram showing an example of a high-pass filter having a configuration in which a plurality of lumped constant circuit elements are combined and connected in a T shape.

  As shown in FIG. 4, this high-pass filter has first and second capacitors 51 and 52 as series elements, and is connected in series between the connection point of the first and second capacitors 51 and 52 as a shunt element and the ground. It has an inductor 53 and a third capacitor 54 connected to each other. By selecting the capacitance values of the first to third capacitors 51, 52 and 54 and the inductance value of the inductor 53, the high-pass characteristics can be obtained. Can be

  FIG. 5 is a circuit diagram showing an example of a configuration of a high-pass filter having a configuration in which a plurality of lumped constant circuit elements are used as series elements and a pair of strip lines mutually coupled as shunt elements are connected in combination.

  As shown in FIG. 5, this high-pass filter has first to third capacitors 61, 62, 63 as series elements, and is connected between the connection point of the first and second capacitors 61, 62 as a shunt element and the ground. And a second strip line 65 connected between the connection point of the second and third capacitors 62 and 63 and the ground, and the first and second strip lines 64 and 65 are connected to each other. The capacitance values of the first to third capacitors 61, 62, and 63, the inductance values of the first and second strip lines 64 and 65, and the first and second strip lines 64 and 65 are mutually coupled. By selecting the mutual coupling coefficients, the high-pass characteristics can be made desired.

  Here, FIG. 6 is a characteristic diagram showing an example of a filter characteristic exhibited by the high-pass filter shown in FIG. 5, and has a high-frequency cutoff characteristic near a frequency of 1.8 GHz.

  In the characteristic diagram shown in FIG. 6, the horizontal axis represents the frequency expressed in GHz, and the vertical axis represents the attenuation expressed in dB. As shown in this characteristic diagram, the high-pass filter has a characteristic that has a peak of attenuation due to traps in a frequency part slightly higher than 1.5 GHz in the attenuation band, and almost all attenuation in the frequency part higher than 1.9 GHz in the pass band. Exhibits no characteristics.

  Each of the high-pass filters shown in FIGS. 5 and 6 has a configuration using a plurality of lumped constant circuit elements, and the reactance value of each lumped constant circuit element can be arbitrarily adjusted. While it has the advantage that it is relatively easy to adjust the pass and cut-off characteristics of the filter, the number of parts used in the high-pass filter increases, the high-pass filter itself can be downsized, and this high-pass filter can be used in other circuits. At the same time, it is difficult to integrate on the same substrate.

  In order to avoid such difficulties, the filter circuit can be reduced in size by providing two strip lines coupled to each other on the multilayer circuit board without using a lumped constant circuit element, although it is a band-pass filter. Such a multilayer circuit board has been proposed in Japanese Patent Application Laid-Open No. 2004-031601.

  FIG. 7 shows a configuration of a multilayer circuit board disclosed in Japanese Patent Application Laid-Open No. 2004-031601, and is a perspective view showing a part of the internal configuration in a see-through state.

  As shown in FIG. 7, the multilayer circuit board is parallel to the first to third dielectric layers 71, 72, and 73 stacked in the vertical direction and between the second and third dielectric layers 72 and 73. The first and second inductor electrodes 74 and 75 that are spaced apart from each other and the first and second dielectric layers 71 and 72 are spaced apart from each other at positions facing the first and second inductor electrodes 74 and 75. A first through conductor 78 connected between the first inductor electrode 74 and the first capacitor electrode 76 through a first through hole provided in the second dielectric layer 71; A second through conductor 79 connected between the second inductor electrode 75 and the second capacitor electrode 77 through a second through hole provided in the second dielectric layer 71, and the first to third dielectric layers 71 and 72. , 73 through the third through hole provided in the first inductor The second inductor electrode 75 is passed through the first grounding through conductor 80 that connects the electrode 74 to the outermost ground conductor and the fourth through-holes provided in the first to third dielectric layers 71, 72, and 73. A second grounding through conductor 81 connected to the ground conductor of the outer layer, a first input / output line 82 branched from the first inductor electrode 74 in a right angle direction, and a second input branched from the second inductor electrode 75 in a right angle direction. And an output line 83.

According to the multilayer circuit board having such a configuration, the first and second inductor electrodes 74 and 75 and the first and second capacitor electrodes 76 and 77 are formed in different layers, and the first inductor electrode 74 and the first capacitor electrode are formed. 76 is connected by the first through conductor 78, and the second inductor electrode 75 and the second capacitor electrode 77 are connected by the second through conductor 78, so that the required reactance value can be obtained in a stable state, In addition, it is possible to suppress the influence on the filter characteristics due to the misalignment of the first to third dielectric layers 71, 72, 73.
JP 2004-031601 A

  By the way, the filter constituted by the multilayer circuit board disclosed in Japanese Patent Application Laid-Open No. 2004-031601 is constituted only by the distributed constant circuit formed on the multilayer circuit board and does not use the lumped constant circuit element. However, it is difficult to make the slope of the attenuation-pass characteristic near the cutoff frequency of the filter steep, and this type of filter may not be used depending on the application.

  The present invention has been made in view of such a technical background, and an object of the present invention is to form a trap circuit including a parallel resonant circuit in the vicinity of a cutoff frequency in the pass band of the high-pass filter, and in the vicinity of the cutoff frequency. It is an object of the present invention to provide a high-pass filter that greatly reduces the attenuation characteristic of the filter.

In order to achieve the above object, a high-pass filter according to the present invention is a flat U-shaped filter having one and other parallel portions and a connecting portion connecting the other end portions of the one and other parallel portions. The first and second strip lines are arranged on different dielectric layers of the multilayer substrate so that the connecting portions of the first and second strip lines are opposite to each other, and the first and second strip lines are arranged. The corresponding one and other parallel portions of the two strip lines are arranged opposite to each other, a signal input end is formed at one end of the one parallel portion of the first strip line, and one parallel portion of the second strip line is formed And forming a signal output end at one end of the
The other end of one parallel portion of the first strip line and the other end of the other parallel portion of the first strip line are connected by a first connection portion,
The other end of one parallel portion of the second stripline and the other end of the other parallel portion of the second stripline are connected by a second connection portion;
One end of one parallel portion of the first strip line and the other end of the other parallel portion of the second strip line are opposed to each other,
The other end of one parallel portion of the first strip line and one end of the other parallel portion of the second strip line are opposed to each other,
One end of the other parallel portion of the first strip line and one other end of the second strip line are opposed to each other,
The other end of the other parallel portion of the first stripline and one end of the second stripline are opposed to each other;
One end of the other parallel portion of the first strip line and one end of the other parallel portion of the second strip line are conductively connected to a ground conductor through a through hole provided in the multilayer substrate ;
A parallel resonant circuit comprising: a distributed capacitor component formed between the other parallel portion of the first strip line and the ground conductor; and an inductor component formed by the through hole connected to the first strip line. Let the resonant frequency be the passband,
A parallel resonant circuit comprising a distributed capacitor component formed between the other parallel portion of the second strip line and the ground conductor, and an inductor component formed by the through hole connected to the second strip line Let the resonant frequency be the passband.

  As described above, according to the high-pass filter of the present invention, the inductance component formed in the portion conductively connected to the ground conductor through the through hole provided in the multilayer substrate, and the first and second strips arranged to face each other. A parallel resonant circuit is formed by the capacitance component formed between the other parallel parts of the line, and the resonant circuit is configured to form a trap circuit in the vicinity of the cutoff frequency in the pass band of the high-pass filter. This trap circuit has the effect that the attenuation characteristic in the vicinity of the cutoff frequency within the pass band of the high-pass filter can be greatly reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 relates to an embodiment of a high-pass filter according to the present invention. FIG. 1 is a perspective view showing a part of the overall configuration in a transparent state, with a high-frequency cutoff frequency of 1.8 GHz. An example of selecting a nearby frequency is shown.

  As shown in FIG. 1, the high-pass filter according to this embodiment includes first to third dielectric layers 1, 2, and 3, and first and second dielectric layers 1, 2 that are stacked in the vertical direction. A connecting portion 4 (3) arranged between the first and second parallel portions 4 (1), 4 (2) and the other ends of the first and second parallel portions 4 (1), 4 (2). ) Between the second and third dielectric layers 2 and 3 and the first and second parallel portions 5 (1) and 5 (2). And a flat U-shaped second strip line 5 having a connecting portion 5 (3) connecting the other ends of the first and second parallel portions 5 (1) and 5 (2), and a first dielectric. A first ground conductor 6 formed on the upper surface of the body layer 1 and a second ground conductor 7 formed on the lower surface of the third dielectric layer 3 are provided.

  In addition, the high-pass filter according to this embodiment has one end of the second parallel portion 4 (2) of the first strip line 4 and the first ground conductor 6 through the first through hole 8 provided in the first dielectric layer 1. A first connection conductor 9 connected between the first and second end portions of the second parallel portion 5 (2) of the second stripline 5 through a second through hole 10 provided in the third dielectric layer 3 and a second ground conductor. 7, a second connection conductor 11 connected between the first strip portion 4, a signal input end 12 connected to one end of the first parallel portion 4 (1) of the first strip line 4, and a first parallel of the second strip line 5. A signal output end 13 connected to one end of the portion 5 (1), and third to sixth through holes 14, 15 provided at four corner portions of the first to third dielectric layers 1, 2, 3, respectively. Connected between the first connecting conductor 9 and the second connecting conductor 10 through 16 and 17. The and a third to sixth connection conductor 18, 19, 20, 21.

  In this case, the arrangement form of the flat U-shaped first strip line 4 and the flat U-shaped second strip line 5 arranged in the first to third dielectric layers 1, 2, 3 is as follows. The first parallel portion 4 (1) of the first stripline 4 and the second parallel portion 5 (2) of the second stripline 5 are arranged to face each other, and the second parallel portion 4 (2) of the first stripline 4 is disposed. And the first parallel portion 5 (1) of the second stripline 5 are arranged to face each other, and the connecting portion 4 (3) of the first stripline 4 and the connecting portion 5 (3) of the second stripline 5 are The first U-shaped strip line 4 and the second U-shaped strip line 5 are disposed in opposite directions.

  Further, a third through provided in the four corners of the first ground conductor 6 and the second ground conductor 7 so as to penetrate the first dielectric layer 1, the second dielectric layer, and the third dielectric layer 3. A hole 14, a fourth through hole 15, a fifth through hole 16, and a sixth through hole 17 are formed, and the first ground conductor 6 and the second ground conductor 7 are conducted in the third through hole 14. A third connection conductor 18 to be connected is provided in the fourth through hole 15, and a fourth connection conductor 19 for conductively connecting the first ground conductor 6 and the second ground conductor 7 is provided in the fifth through hole 16. A fifth connection conductor 20 that conductively connects the first ground conductor 6 and the second ground conductor 7, and a sixth connection conductor 21 that conductively connects the first ground conductor 6 and the second ground conductor 7 in the sixth through hole 17. Are formed, and the first ground conductor 6 and the second ground conductor 7 are formed by these configurations. There is set to be the same ground potential.

  2 is a circuit configuration diagram illustrating the configuration of the high-pass filter illustrated in FIG. 1 with an equivalent circuit, and FIG. 3 is a characteristic diagram illustrating an example of filter characteristics exhibited by the high-pass filter illustrated in FIG. Thus, this corresponds to the characteristic diagram shown in FIG. In FIG. 2, the same constituent elements as those shown in FIG. In FIG. 3, the horizontal axis represents the frequency expressed in GHz, and the vertical axis represents the attenuation expressed in dB.

As shown in FIG. 2, the high-pass filter includes a first parallel portion 4 (1) of the first stripline 4 and a second parallel portion 5 (2) of the second stripline 5, which are coupled to each other. One end of the parallel portion 4 (1) is connected to the signal input end 12, and one end of the second parallel portion 5 (2) is grounded through the second connection conductor 11. Further, the second parallel portion 4 (2) of the first strip line 4 and the first parallel portion 5 (1) of the second strip line 5 are mutually coupled, and one end of the second parallel portion 4 (2) is the first. The connection conductor 9 is grounded and one end of the first parallel portion 5 (1) is connected to the signal output end 13. In addition, the other ends of the first parallel portion 4 (1) and the second parallel portion 4 (2) are connected to each other by the first connection portion 4 (3), and the second parallel portion 5 (2) and the second parallel portion 4 (2) are connected to each other. One parallel portion 5 (1) is connected to each other by a second connection portion 5 (3).

  The high-pass filter having the above-described configuration operates as follows.

When the UHF signal is supplied to the signal input terminal 12 on one end side of the first parallel portion 4 (1) of the first stripline 4, the UHF signal is converted into the first parallel portion of the first stripline 4 which is mutually coupled. 4 (1) and the second parallel part 5 (2) of the second stripline 5 are transmission coupled from the first parallel part 4 (1) to the second parallel part 5 (2). The UHF signal is transmitted from the other end side of the first parallel portion 4 (1) of the first stripline 4 to the other end side of the second parallel portion 4 (2) of the first stripline 4 through the connection portion 4 (3). And transmitted simultaneously from the other end side of the second parallel portion 5 (2) of the second stripline 5 to the other end side of the first parallel portion 5 (1) of the second stripline 5, and these UHF A signal is supplied to the second parallel portion 4 (2) of the first stripline 4 and the second parallel portion 4 (2) of the first parallel portion 5 (1) of the second stripline 5 which are coupled to each other. Thereafter, the UHF signal transmitted to the second parallel portion 4 (2) is added to the UHF signal transmitted and coupled from the second parallel portion 4 (2) to the second parallel portion 5 (2) and added. The UHF signal is output from the signal output terminal 13 on one end side of the first parallel portion 5 (1) to the subsequent circuit.

  At this time, the distributed capacitor component formed between the second parallel portion 4 (2) of the first strip line 4 and the first ground conductor 6 is connected between one end of the second parallel portion 4 (2) and the ground point. The parallel circuit with the inductor component formed by the first connection conductor 9 in the through-hole 8 is resonated at a first frequency near the high-frequency cut-off frequency, for example, the frequency f1 shown in FIG. A trap circuit is formed, and the distributed capacitor component formed between the second parallel portion 5 (2) of the second strip line 5 and the second ground conductor 7 is in contact with one end of the second parallel portion 5 (2). A parallel circuit with an inductor component formed by the second connection conductor 11 in the through hole 10 connected between the points is a second frequency in the vicinity of the high-frequency cutoff frequency, for example, the frequency f2 shown in FIG. Resonate at Since the two trap circuit is configured, as is apparent from the comparison of the characteristic diagram shown in FIG. 3 and the characteristic diagram shown in FIG. Attenuation characteristics in the vicinity of the high-frequency cutoff frequency are greatly reduced, and a rising characteristic in the vicinity of the high-frequency cutoff frequency can be improved.

FIG. 5 is a perspective view showing a part of the entire configuration in a perspective state according to one embodiment of the high-pass filter according to the present invention. FIG. 2 is a circuit configuration diagram illustrating a configuration of a high-pass filter illustrated in FIG. 1 by an equivalent circuit. It is a characteristic view which shows an example of the filter characteristic which the high pass filter illustrated in FIG. 1 exhibits. It is a circuit diagram which shows an example of the high-pass filter of the structure which combined and connected the some lumped constant circuit element to the T shape. FIG. 5 is a circuit diagram showing an example of a configuration of a high-pass filter having a configuration in which a plurality of lumped constant circuit elements are used as series elements and a pair of strip lines mutually coupled as shunt elements are connected in combination. FIG. 6 is a characteristic diagram illustrating an example of filter characteristics exhibited by the high-pass filter illustrated in FIG. 5. BRIEF DESCRIPTION OF THE DRAWINGS It is the perspective view which showed the structure of the multilayer circuit board disclosed by Unexamined-Japanese-Patent No. 2004-031601, and represented some internal structures in the see-through | perspective state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st dielectric layer 2 2nd dielectric layer 3 3rd dielectric layer 4 Flat U-shaped 1st stripline 4 (1) 1st parallel part 4 (2) 2nd parallel part 4 (3) Connection portion 5 Flat U-shaped second strip line 5 (1) First parallel portion 5 (2) Second parallel portion 5 (3) Connection portion 6 First ground conductor 7 Second ground conductor 8 First Through hole 9 First connecting conductor 10 Second through hole 11 Second connecting conductor 12 Signal input end 13 Signal output end 14 Third through hole 15 Fourth through hole 16 Fifth through hole 17 Sixth through hole 18 3rd connection conductor 19 4th connection conductor 20 5th connection conductor 21 6th connection conductor

Claims (2)

A flat U-shaped first and second strip line each having one and the other parallel portion and a connecting portion connecting each other end of the one and the other parallel portion are different from each other in the multilayer substrate. In the dielectric layer, the connecting portions of the first and second strip lines are disposed in opposite directions, and the corresponding one and other parallel portions of the first and second strip lines are disposed on the dielectric layer. A signal input end is formed at one end of one parallel portion of the first strip line, a signal output end is formed at one end of the one parallel portion of the second strip line,
The other end of one parallel portion of the first strip line and the other end of the other parallel portion of the first strip line are connected by a first connection portion,
The other end of one parallel portion of the second stripline and the other end of the other parallel portion of the second stripline are connected by a second connection portion;
One end of one parallel portion of the first strip line and the other end of the other parallel portion of the second strip line are opposed to each other,
The other end of one parallel portion of the first strip line and one end of the other parallel portion of the second strip line are opposed to each other,
One end of the other parallel portion of the first strip line and one other end of the second strip line are opposed to each other,
The other end of the other parallel portion of the first strip line and one end of the second strip line are opposed to each other;
One end of the other parallel portion of the first strip line and one end of the other parallel portion of the second strip line are conductively connected to a ground conductor through a through hole provided in the multilayer substrate ;
A parallel resonant circuit comprising: a distributed capacitor component formed between the other parallel portion of the first strip line and the ground conductor; and an inductor component formed by the through hole connected to the first strip line. Let the resonant frequency be the passband,
A parallel resonant circuit comprising a distributed capacitor component formed between the other parallel portion of the second strip line and the ground conductor, and an inductor component formed by the through hole connected to the second strip line high pass filter characterized by a passband and to Rukoto the resonant frequency.   The high-pass filter according to claim 1, wherein the ground conductor is a ground conductor formed and arranged on one surface of the multilayer substrate.

Images