JPH07162206A - Filter device with resonator - Google Patents

Abstract

PURPOSE:To make a shift to a passing band abrupt by specifying the length of a distribution constant type transmission line connected between plural trap circuits consisting of series circuits of dielectric resonators and capacitances. CONSTITUTION:A band-pass filter consists of 1st and 2nd TEM-mode coaxial type dielectric resonators 1 and 2 and a multi-layered substrate 3 having a conductor layer and a ground conductor layer for a capacitor in combination. Here, an equivalent circuit of the filter is composed of the 1st and 2nd trap circuits 11 and 12 and the distribution constant type transmission line 13, the circuit 11 consists of the series circuit of the 1st resonator 1 and the capacitance C1 using the capacitor, and the circuit 12 also consists of the series circuit of the 2nd resonator 2 and the capacitance C2, and the circuit 11 is parallel between an input terminal 14 and a ground terminal 15 and the circuit 12 is parallel to the circuit 11 through the transmission line 13. The length D of the transmission line 13 is set to D=A+(lambda/2)n. Here, lambda is the wavelength of a basic wave having the center frequency of a stopping band, (n) is 0 or a plus integer, and A is a value different from 1/4 of the wavelength lambda.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a band stop filter device including a plurality of dielectric resonators.

[0002]

2. Description of the Related Art A plurality of trap circuits consisting of a series circuit of a dielectric resonator and a capacitor are connected between a signal transmission line and a ground, and the transmission line length between the plurality of trap circuits is λ / A band stop filter set to 4 (where λ is the wavelength of the fundamental frequency signal) is disclosed in, for example, Japanese Utility Model Application Laid-Open No. 58-16903.

[0003]

By the way, in the frequency characteristics of this type of band stop filter, it is desirable that the change from the pass band to the stop band is steep. As a method of obtaining this steep characteristic, there is a method of increasing the number of trap circuits composed of a series circuit of the above-mentioned dielectric resonator and capacitor. However, if this method is adopted,
Due to the increase in the number of parts, there is a problem that the cost is increased and the filter device is enlarged.

Therefore, an object of the present invention is to reduce the cost and size of a band stop filter device having steep characteristics.

[0005]

According to the present invention for achieving the above object, a plurality of trap circuits each comprising a series circuit of a dielectric resonator and a capacitance are connected to each other and the plurality of trap circuits are connected to each other. LC distributed constant type transmission line, wherein the length of the transmission line is A + (λ / 2) n
(Where λ is the wavelength of the fundamental wave to be blocked, n is zero or a positive integer, and A is a value different from ¼ of the wavelength λ). It is related. It is desirable that the transmission line be a strip line as described in claim 2. Also,
As shown in claim 3, the value of A is smaller than 1/4 of the wavelength λ and is 1/50 or more, or is larger than 1/4 of the wavelength λ and 9 / It is preferably 20 or less. Further, as shown in claim 5, A of claim 1 is set to A1 (where A1 is a value smaller than λ / 4) and A is set to A2 (where A2 is λ / 4).
A band stop filter can be configured by combining with a second filter set to a larger value).

[0006]

According to the present invention, the value of A is set to λ /
When it is larger than 4, the transmission line becomes a capacitance equivalently, and this capacitance, a trap circuit and a new resonance circuit are formed. As a result, the frequency characteristic curve transitioning from the stop band to the pass band becomes steeper on the higher frequency side than the center frequency of the stop band. On the contrary, when the value of A is smaller than λ / 4, the transmission line equivalently becomes an inductance, and a new resonance circuit is formed by this inductance and the trap circuit. As a result, the frequency characteristic curve transitioning from the stop band to the pass band becomes steeper on the low frequency side of the center frequency of the stop band. Therefore, according to the first to fourth aspects of the invention, it is possible to provide a band stop filter device in which the stop band has a sharp transition to the high-pass band or the transition from the stop band to the low-pass band. it can. Further, according to the invention of claim 5, both the high band side and the low band side of the stop band can be made steep.

[0007]

[First Embodiment] A band stop filter including a TEM mode dielectric resonator according to a first embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, this band stop filter is a multi-layer substrate 3 having first and second TEM mode coaxial type dielectric resonators 1 and 2, and a conductor layer for capacitance (capacitor) and a ground conductor layer. It is composed of a combination of. First
As is clear from FIG. 3, the second dielectric resonators 1 and 2 are made of a columnar or cylindrical porcelain having a relative permittivity of about 88, and an inner conductor 6 provided in the resonance hole 5. And an outer conductor 8 provided on the outer peripheral surface 7 of the dielectric 4. In addition,
A connection conductor 9 is continuously provided on the inner conductor 6. The connecting conductor 9 extends to the outer peripheral surface 7 through one end surface of the dielectric 4. A short-circuit conductor 10 for connecting the inner conductor 6 to the outer conductor 8 is provided on the other end surface of the dielectric 4. An inner conductor 6, an outer conductor 8, a connecting conductor 9,
Each of the short-circuit conductors 10 can be composed of a conductor film coated with silver paste and baked, or copper plating or the like.

The first and second resonators 1 and 2 and the multilayer substrate 3
Are configured to obtain the equivalent circuit shown in FIG.
The band stop filter of FIG. 6 includes first and second trap circuits 11 and 12 and a distributed constant type transmission line 13. The first trap circuit 11 comprises a series circuit of the first resonator 1 and the capacitance C1. The second trap circuit 12 comprises a series circuit of the second resonator 2 and the capacitance C2. The first and second resonators 1 and 2 are shown as a parallel circuit of a capacitance C and an inductance L. The first trap circuit 11 is connected between the input terminal 14 and the ground terminal 15. The second trap circuit 12 is connected in parallel to the first trap circuit 11 via the transmission line 13. That is, the transmission line 13 having the length D is connected in series between the input terminal 14 and the output terminal 16 and between the first and second trap circuits 11 and 12. The length D of the transmission line 13 is determined by the wavelength λ of the fundamental wave having the center frequency of the stop band of this filter.
Is set to be larger than 1/4. That is, the length D is expressed by A + (λ / 2) n, where n is zero,
The length is set so that A has a value larger than λ / 4.

The multi-layer substrate 3 for constructing the filter circuit of FIG. 6 is divided into first and second layers as shown in FIG.
Of dielectric layers 3a and 3b and various conductor layers. The multilayer substrate 3 is obtained by applying a conductive paste to a green sheet (unfired porcelain sheet) for obtaining the first and second dielectric layers 3a and 3b by applying a conductive paste in a predetermined pattern and laminating and firing. Later on the first and second dielectric layers 3
Although a and 3b are integrated, they are separated here for convenience of description.

On the surface 17 of the multi-layer substrate 3, that is, the surface of the first dielectric layer 3a, as shown in FIG. 3, the ground conductor layer 18 and the conductor layers 19 for the first and second connection and capacitance,
And 20 are provided. The ground conductor layer 18 has a portion corresponding to the outer conductor 8 of the first and second resonators 1 and 2, and is formed so as to cover most of the surface 17, and as shown in FIG. The outer conductors 8 of the first and second resonators 1 and 2 are fixed to each other by the solder 21. The first and second connection and capacitance conductor layers 19 and 20 are arranged so as to correspond to the connection conductors 9 of the first and second resonators 1 and 2, and these are fixed by solder 22 respectively. .
Under the ground conductor layer 18 of the first dielectric layer 3a, via holes 23 and 24 are provided from the front surface to the back surface of the dielectric layer 3a, and are filled with conductors.

As shown in FIG. 4, on the surface 25 of the second dielectric layer 3b, the conductor layers 26 and 27 for ground connection, the conductor layers 28 and 29 for capacitance, and the conductor layer 30 for transmission line are provided.
Is provided. The ground conductor layers 26, 27 are shown in FIG.
It is arranged so as to correspond to the via holes 23 and 24 of
It is connected to the ground conductor layer 18 on the surface 17 by the conductor filled therein. Capacitance conductor layer 2
8 and 29 are arranged to face the first and second connection and capacitance conductor layers 19 and 20 of the first dielectric layer 3a,
Form the first and second capacitances C1 and C2 of FIG. The transmission line conductor layer 30 is disposed so as to connect between the first and second capacitance conductor layers 28 and 29, and the length (path) D thereof satisfies the condition of D> λ / 4. It is set. The conductor layer 30 for the transmission line
Faces the ground conductor layer 18 via the first dielectric layer 3a, and thus functions as a strip line, that is, a distributed constant transmission line, and provides the TEM mode transmission line 13.

Via holes 31 and 32 are provided below the conductor layers 26 and 27 for ground connection of the second dielectric layer 3b, and via holes 33 and 34 are provided below the conductor layers 28 and 29 for capacitance. Filled with conductor.
As shown in FIG. 5, a ground terminal conductor layer 36, an input terminal conductor layer 37, and an output terminal conductor layer 38 are provided on the back surface 35 of the second dielectric layer 3b, that is, the back surface of the multilayer substrate 3.
The ground conductor layer terminal 36 has via holes 23, 24, 3
The conductors 1 and 32 are connected to the ground conductor layer 18 on the surface. The input and output terminal conductor layers 37 and 38 are connected to the capacitance conductor layers 28 and 29 by the conductors of the via holes 33 and 34. The ground terminal conductor layer 36, the input terminal conductor layer 37, and the output terminal conductor layer 38 on the back surface 35 of FIG. 5 correspond to the ground terminal 15, the input terminal 14, and the output terminal 16 of the circuit of FIG.

A solid line A1 in FIG. 7 is a characteristic curve showing the relationship between the frequency and the attenuation amount of the band stop filter in FIG. 6, and a dotted line B1 is a conventional curve in which the length D of the transmission line 13 in FIG. 6 is λ / 4. 3 is a characteristic curve of the filter of FIG. 6 shows in detail the constants of the respective parts, the resonance frequency f1 of the first resonator 1 is 923 MHz, and the resonance frequency f2 of the second resonator 2 is f2.
Is 923 MHz, the capacitance of capacitance C1 is 2 pF,
The capacitance of the capacitance C2 is 2 pF, the length D of the transmission line 13 is 0.2777λ (where λ is the wavelength of the fundamental wave of 1000 MHz), and the characteristic impedance Z0 of the transmission line 13 is
Is 50Ω.

The characteristic curve of the solid line A1 in FIG. 7 according to the present invention has a steeper rise on the high frequency side of the center frequency f0 'of the stop band (attenuation band) and a lower frequency band than the conventional characteristic curve shown by the dotted line B1. The rising on the side is gentle. Therefore, it can be used in a circuit which is required to rise steeply on the high frequency side.

FIG. 8 shows the length D of the transmission line conductor layer 30 of FIG.
1 shows an equivalent circuit of a band stop filter having the same configuration as that of FIGS. 1 to 5 except that is shorter than λ / 4. The characteristic curve of the filter constructed in this way becomes a solid line A2 in FIG. In FIG. 9, the length D of the transmission line 13 is λ /
The characteristic curve of the conventional filter set to 4 is shown by the dotted line B1. In each part of FIG. 8, the constants of each part other than the length D of the transmission line 13 are the same as those in FIG. 6, and D is 0.16.
66λ.

The characteristic curve according to the present invention shown by the solid line A2 in FIG. 9 has a steeper rise on the low frequency side than the center frequency f0 'of the stop band (attenuation band) as compared with the conventional characteristic curve shown by the dotted line B1. , The rising is gentle on the high frequency side. Therefore, it is suitable for a circuit that requires a sharp rise on the low frequency side.

Next, the reason why the frequency characteristic changes by changing the length D of the transmission line 13 will be described with reference to FIGS. 10 shows only the first and second trap circuits 11 and 12, and FIG. 11 shows the relationship between the frequency f and the reactance X of the circuit of FIG. The resonance frequency of each of the trap circuits 11 and 12 is f10, and the resonance frequency of each of the dielectric resonators 1 and 2 is f20. Each trap circuit 1
The reactances X of Nos. 1 and 12 are zero at this resonance frequency f10 and show maximum attenuation. The reactance X becomes negative on the low frequency side of the resonance frequency f10. This means that each trap circuit 11 and 12 acts as a capacitance. On the contrary, the reactance X becomes positive on the higher frequency side than the resonance frequency f10. This means that each of the trap circuits 11 and 12 works as an inductance.

The reactance X between the terminals 14 and 15 in FIG. 12 of the transmission line 13 consisting of a strip line (distributed constant circuit) changes with frequency as shown in FIG.
When the length of the transmission line 13 is λ / 4, the reactance X becomes infinite, and when the length of the transmission line 13 is shorter than λ / 4, the reactance becomes positive and functions as the inductance L. If the length is longer than λ / 4 and the reactance becomes negative, the capacitance C functions. When the length of the transmission line 13 is λ / 4 or in the vicinity thereof, the reactance between the terminals 14 and 15 has an infinite value or an extremely large value, so that the mutual influence of the first and second trap circuits 11 and 12 is prevented. It becomes possible to ignore.

The length of the transmission line 13 is A + (λ /
2) If A is set as described above even when setting to n,
The same effect can be obtained

Assuming that the input signal of the band stop filter has a stop band frequency, the reactance X of the second trap circuit 12 becomes zero due to resonance, and the resistance component is also zero, the output of the transmission line 13 Figure 1 at the end
As shown in 2, it is connected to the ground. Therefore, a circuit state in which the transmission line 13 is connected in parallel to the first trap circuit 11 is established. Next, the frequency characteristics when the length D of the transmission line 13 is changed in such a circuit state will be described.

FIG. 14 shows an equivalent circuit in the case where the length D of the transmission line 13 is λ / 4 as in the conventional case. In this case, since the reactance of the transmission line 13 is large in the stop band or in the vicinity thereof, it can be considered that only the first trap circuit 11 has the frequency characteristic shown in FIG.

According to the present invention, when the length D of the transmission line 13 is made longer than λ / 4, the transmission line 13 can be regarded as the capacitance C as described with reference to FIGS. 12 and 13, and as shown in FIG. Then, the capacitance C is connected in parallel to the first trap circuit 11. As a result, the resonance of the combination of the first trap circuit 11 and the capacitance C based on the transmission line 13 occurs at the frequency fa higher than the stop band center frequency f0 in FIG. As a result, the rising curve on the high frequency side of the stop band becomes steep as shown by the solid line. The characteristic curve shown by the dotted line in FIG. 17 is the same characteristic curve as that shown in FIG. 15 for comparison.

When the length D of the transmission line 13 is made shorter than λ / 4, the transmission line 13 becomes the inductance L equivalently. Therefore, the equivalent circuit in the vicinity of the resonance frequency in this case is as shown in FIG. As a result, a resonance circuit composed of a parallel circuit of the first trap circuit 11 and the inductance L of the transmission line 13 is formed, and this resonance is lower than the center frequency f0 of the stop band as shown by the solid line in FIG. Occurs at the frequency fb, and the rising edge on the low frequency side of the stop band becomes sharp. For comparison, FIG. 19 shows the same characteristic curve as that of FIG. 15 by a dotted line.

As is apparent from the above, according to the embodiment of the present invention, the rising curve of the blocking center frequency on the high frequency side or the low frequency side is made sharp without relying only on increasing the number of trap circuits. be able to. That is, the frequency characteristics can be improved without increasing the cost and increasing the size. Further, in this embodiment, since the first and second resonators 1 and 2 are juxtaposed with directions opposite to each other, they propagate in the air between the input terminals, that is, between the conductive layers 19 and 20. Signal leakage is prevented. In addition, the first and second resonators 1,
It becomes easy to form between the two using the capacitances C1 and C2, the transmission line 13, and the multilayer substrate 3.

[0025]

[Second Embodiment] Next, a second embodiment will be described with reference to FIGS.
The band stop filter of the embodiment will be described. However,
20 to 24 and FIGS. 25 to 31 described later,
The same parts as those in FIGS. 1 to 9 are designated by the same reference numerals and the description thereof will be omitted. FIG. 20 shows a band stop filter according to the second embodiment. This filter is obtained by adding a third resonator 40 to the filter shown in FIG. Third resonator 4
0 has the same configuration as that of FIG. 2 like the first and second resonators 1 and 2. In order to add the resonator 40 of FIG. 3, the third connection and capacitance conductor layer 4 is provided on the multilayer substrate 3.
1 is added, and the connection conductor 9 of the third resonator 40 is connected thereto by solder (not shown).

The multilayer substrate 3 has first, second and third capacitances C1, C2 and C3 for forming the filter circuit of FIG. 21 in the same manner as in FIGS. 3 to 5 and the first and second capacitances. Transmission lines 13 and 42 are provided. The filter circuit of FIG. 21 is similar to the filter circuit of FIG.
And a third trap circuit 43 are added. The third trap circuit 43 is composed of a series circuit of a third resonator 40 and a third capacitance C3, and is connected between the output terminal of the second transmission line 42 and the ground terminal 15. Like the first transmission line 13, the second transmission line 42 is composed of a strip line, that is, an LC distributed constant circuit, and is connected between the second and third trap circuits 12 and 43. The lengths D1 and D2 of the first and second transmission lines 13 and 42 are both formed to be larger than λ / 4 (where λ is the wavelength of the fundamental wave at the center frequency of the stop band of the filter).

The solid curve in FIG. 22 shows the frequency characteristic of the filter in FIG. However, the constants of each part in FIG. 21 are as follows. C1 = 1.16pF, C2 = 1.72pF,
C3 = 1.63 pF, the first, second and third resonators 1,
The resonance frequencies f1, f2 and f3 of 2, 40 are 823 MH.
z, 826 MHz, 825 MHz, and the lengths D1 and D2 of the first and second transmission lines 13 and 42 are both 0.361λ.
(Where λ is the wavelength of the waveform of 800 MHz). Figure 2
The curve indicated by the dotted line 2 is D1 and D in FIG. 21 for comparison.
The frequency characteristics when 2 is λ / 4, that is, 0.25λ are shown. The constants of each part of the conventional filter for this comparison are as follows. C1 = 1.20pF, C2 = 2.00p
F, C3 = 1.20 pF, f1 = 824 MHz, f2 =
830MHz, f3 = 824MHz, D1 = 0.25
λ, D2 = 0.25λ (where λ is the wavelength of the 800 MHz waveform).

The filter of FIG. 21 can be seen from the comparison between the solid line characteristic curve of FIG. 22 and the dotted line characteristic curve of FIG.
It has the same function and effect as the filter of.

FIG. 23 shows a filter in which the length D1 of the transmission lines 13 and 42 of the filter shown in FIG. 21 is shorter than λ / 4, that is, 0.25λ. The frequency characteristic of the filter of FIG. 23 becomes the solid curve of FIG. The constants in FIG. 23 are C1 = 1.59 pF, C2 = 3.42 pF, C3 =
3.11pF, f1 = 817MHz, f2 = 860MH
z, f3 = 883 MHz, D1 = 0.0833λ, D2
= 0.118λ (where λ is the wavelength of the waveform of 800 MHz). The dotted characteristic curve in FIG. 24 is shown in FIG.
The same thing as the dotted characteristic curve is shown.

As is clear from the solid curve of FIG. 24, the filter of FIG. 23 can also obtain the same effect as the filter of FIG.

[0031]

[Third Embodiment] Next, a band stop filter of a third embodiment shown in FIGS. 25 and 26 will be described. This filter has a configuration in which the first and second dielectric resonators 1a and 1b are modified as shown in FIG. 6, and the transmission line conductor layer 30 is provided on the surface of the dielectric substrate 3c. Resonators 1a, 2
2a has a configuration in which the conductor layer 9 on one end face of the resonators 1 and 2 in FIG. 2 is removed. Therefore, in FIG. 26, the inner conductor 6
And the connection conductor 9a are electrically separated from each other and face each other via the dielectric 4. Therefore, the inner conductor 6 and the connecting conductor 9
Capacitances C1 and C2 can be obtained with a.

On the surface of the dielectric substrate 3c, the ground conductor layer 18 and the first and second connection conductor layers 19, as in FIG.
20 is provided, a transmission line conductor layer 30 formed of a strip line is provided, and the connection conductor layers 19 and 20 are provided.
It is connected to the. The length D of the transmission line composed of the conductor layer 30 is larger or smaller than λ / 4 as in the first and second embodiments. A ground conductor layer and a terminal conductor layer are provided on the back surface of the dielectric substrate 3c as in FIG.
The conductors of the grooves 51, 52 and 53 formed on the side surface of c are connected to the ground conductor layer 18 and the connection conductor layers 19 and 20 on the surface.

The filter of the third embodiment is also basically the first filter.
Since it is the same as the embodiment described above, it has the same effect as this.

[0034]

[Fourth Embodiment] FIG. 27 shows a filter according to a fourth embodiment. The filter shown in FIG. 27 is obtained by adding open stubs 61, 62 and 63 to the second or third harmonics in the filter shown in FIG. 21 or 23. The open stubs 61, 62, 63 are connected to one ends of the first, second and third capacitances C1, C2, C3. Each of the open stubs 61, 62, 63 is formed of a strip line, and acts equivalently as a capacitor on the low frequency side of the resonance frequency of the trap circuits 11, 12, 43. As a result, the same effect as that of the circuit shown in FIG. 28 can be obtained. The open stubs 61, 6
21 and FIG. 23 are the same as those of FIGS.

[0035]

[Fifth Embodiment] FIG. 28 shows a filter obtained by adding stray capacitances 71, 72 and 73 to the filter shown in FIG. 21 or 23. This stray capacitance 71, 72,
73 is generated between one end of the trap circuits 11, 12, 43 and the ground. The stray capacitances 71, 72 and 73 of this kind have the same effects as those in FIG.
The stray capacitances 71, 72, 73 may be necessarily generated in the multilayer substrate 3 or may be positively formed.

[0036]

[Sixth Embodiment] The filter of FIG. 29 is the same as that of FIG.
This filter is provided with trap circuits 81, 82 and 83 for removing the second or third harmonics.
The trap circuits 81, 82 and 83 are the main trap circuit 1
The capacitors 84, 85, 86 and the dielectric resonators 87, 88 are connected between one end of each of the terminals 1, 12, 43 and the ground.
It is composed of a series circuit with 89, and is set to attenuate the second or third harmonic. Others are the same as those in FIG. 21 or FIG. 23, and thus have the same effects as these. Note that the stubs 61, 62 and 63 of FIG. 27, the capacitances 71, 72 and 73 of FIG. 28 and the trap characteristics of the trap circuits 81, 82 and 83 of FIG.
It can be changed by adjusting the lengths D and D2 of 3, 42.

[0037]

[Seventh Embodiment] The band stop filter shown in FIG.
This is a composite filter in which a first band stop filter 91 which is the same as that in FIG. 21 and a second band stop filter 92 which has the same configuration as the band stop filter in FIG. 23 are connected in cascade. As shown in FIG. 31, the filter of FIG. 30 has steep rises on both the high band side and the low band side of the stop band, and an excellent narrow stop band can be obtained.

[0038]

MODIFICATION The present invention is not limited to the above-mentioned embodiments, and the following modifications are possible. (1) The transmission lines 13 and 42 may be coaxial cables or the like. (2) The resonators 1, 2 and 40 can be stripline dielectric resonators. (3) The length of the resonators 1, 2, 40 may be set to 1/2 of the wavelength λ of the fundamental wave, and the short-circuit conductor 10 may be omitted. (4) The resonators 1, 2 and 40 can be modified into a configuration in which the dielectric 4 is rectangular. Further, instead of providing the connection conductor 9, the lead member may be connected to the inner conductor 6. (5) Capacitances C1, C2, and C3 can be individual capacitors such as chip capacitors, and some or all of these capacitors can be inserted into the resonance holes 5 of the resonators 1, 2, and 40. (6) A filter similar to the trap circuits 11, 12, 43 can be further added to form a filter having four or more stages. (7) The length D of the transmission lines 13 and 42 is preferably (1
/ 50) λ ≦ D <(1/4) λ range, and (1/4)
It can be changed within the range of λ <D ≦ (9/20) λ. (8) In the embodiments other than the first embodiment, the length of the transmission line 13 can be set so as to follow the equation of A + (λ / 2) n.

[Brief description of drawings]

FIG. 1 is a perspective view showing a filter according to a first embodiment.

FIG. 2 is a cross-sectional view showing the resonator shown in FIG.

3 is a plan view showing the surface of the multilayer substrate of FIG. 1. FIG.

4 is a plan view showing a second dielectric layer in FIG. 1. FIG.

5 is a bottom view of the second dielectric layer of FIG. 1. FIG.

FIG. 6 is an equivalent circuit diagram of the filter of FIG.

7 is a frequency characteristic diagram of the filter of FIG.

8 is an equivalent circuit diagram showing a filter in which the transmission line length D of the filter of FIG. 1 is smaller than λ / 4.

9 is a frequency characteristic diagram of the filter of FIG.

10 is an equivalent circuit diagram showing the trap circuit of FIG. 6 or FIG.

11 is a diagram showing the relationship between the frequency and reactance of the trap circuit of FIG.

12 is an equivalent circuit diagram showing the transmission line of FIG. 6 or FIG.

13 is a diagram showing the relationship between the reactance and the frequency and transmission line length of the transmission line of FIG.

14 is a circuit diagram showing a state where the length of the transmission line in FIG. 6 or FIG. 8 is λ / 4 and the reactance of this transmission line is infinite.

15 is a frequency characteristic diagram of the circuit of FIG.

16 is an equivalent circuit diagram of FIG. 6 at a frequency higher than the center of the filter stop band of FIG.

17 is a frequency characteristic diagram of the circuit of FIG.

18 is an equivalent circuit diagram of FIG. 8 at a frequency lower than the center of the stop band of the filter of FIG.

19 is a frequency characteristic diagram of the circuit of FIG.

FIG. 20 is a plan view showing a filter according to a second embodiment.

21 is an equivalent circuit diagram when the transmission line length of the filter in FIG. 20 is larger than λ / 4.

22 is a frequency characteristic diagram of the filter of FIG. 21. FIG.

23 is an equivalent circuit diagram when the transmission line length of the filter in FIG. 20 is smaller than λ / 4.

FIG. 24 is a frequency characteristic diagram of FIG. 23.

FIG. 25 is a plan view showing a filter according to a third embodiment.

26 is a cross-sectional view of the resonator of FIG. 25.

FIG. 27 is a circuit diagram showing a filter according to a fourth embodiment.

FIG. 28 is a circuit diagram showing a filter of the fifth embodiment.

FIG. 29 is a circuit diagram showing a filter of the sixth embodiment.

FIG. 30 is a circuit diagram showing a filter of the seventh embodiment.

31 is a frequency characteristic diagram of the filter of FIG. 30. FIG.

[Explanation of symbols]

 1, 2 Resonator 3 Multilayer substrate 11, 12 Trap circuit 13 Transmission line

Claims (5)

[Claims] 1. A plurality of trap circuits each comprising a series circuit of a dielectric resonator and a capacitance, and a distributed constant type transmission line connected between the plurality of trap circuits. The length is A + (λ / 2) n (where λ is the wavelength of the fundamental wave to be blocked, n is zero or a positive integer,
A is set to a value different from 1/4 of the wavelength λ). 2. The band stop filter device according to claim 1, wherein the transmission line is a strip line. 3. The length of the transmission line is 1 of the wavelength λ.
The band stop filter device according to claim 1, 2 or 3, wherein the band stop filter device is smaller than / 4 and is 1/50 or more. 4. The length of the transmission line is 1 of the wavelength λ.
4. The bandpass filter device according to claim 1, wherein the bandpass filter device is larger than / 4 and 9/20 or less. 5. A band-stop filter device in which first and second filters are connected in cascade, wherein the first and second filters are a plurality of trap circuits each including a series circuit of a dielectric resonator and a capacitance. And a transmission line connected between the plurality of trap circuits, wherein the length of the transmission line of the first filter is A1 +
(Λ / 2) n (where λ is the wavelength of the fundamental wave to be blocked, n is zero or a positive integer, and A1 is a value smaller than ¼ of the wavelength λ). The transmission line of the second filter has A2 + (λ / 2) n (where λ is the wavelength of the fundamental wave to be blocked, n is zero or a positive integer, and A2 is a value greater than ¼ of the wavelength λ. ) Is set to a band stop filter device.