JPH01801A - CL circuit element and series resonant band rejection filter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an OL circuit element and a series resonant band-rejection filter used as a small antenna duplexer necessary for a wireless device with a relatively narrow transmission/reception frequency interval. .

"Prior Art" In recent years, wireless communication has become more and more popular, and as a result, interference and interference with neighboring stations has also increased, which has become a major problem. or,
In the age of new media, low-power radio stations have appeared on the data lines of computers and terminals, and radio wave interference is becoming a familiar problem.

Conventionally, we have tried to solve this problem by using high-frequency filter circuits to reduce unnecessary radio wave radiation, but as semiconductor technology progresses and electronic devices become smaller, there is a strong demand for smaller filter circuits. has been done.

For this reason, small filters such as crystal filters and surface acoustic wave filters have been developed for weak signals such as received waves, but materials with high dielectric constants have been developed for transmitting waves and high frequency devices. Attempts have been made to reduce the size of semi-coaxial filters using . For example, this compact filter has achieved great success in radio equipment for car telephones.

"Problems to be Solved by the Invention" Conventional small filters using dielectrics are parallel resonant band-pass filters, and in order to obtain the steep rise selection characteristics aimed at eliminating adjacent interference waves, many resonances are required. It required an element, and there was a limit to miniaturization.

"Means for Solving the Problems" The present invention provides a coaxial line by filling a dielectric material having a uniform permittivity between an inner conductor and an outer conductor, and forming a coaxial line between the inner conductor and the outer conductor at the bottom of the coaxial line. The conductors are short-circuited, and a first separation band and a second separation band that do not intersect with each other are formed around the outer conductor.

The outer conductor between these separation strips serves as a conductive power supply section.

"Example" Embodiments of the present invention will be described below based on the drawings.

First, a first embodiment will be explained.

1 cylindrical inner conductor (1) in Figures 1 and 2
A dielectric material (4) having a uniform permittivity is filled between the external conductor (3) and the conductive power supply (lO) to form a coaxial line (12).
), and at one end of the cuts at both ends of this coaxial line (12), the inner conductor (1) is shorted by the lower outer conductor (3) and the bottom conductor (6), and the upper conductor (7 ) is the first
is open as a separation strip (5,), and the outer conductor (3)
A second peeling band (52) is formed in a band shape with a constant width around the area between the conductive power supply portion (10) and the conductive power supply portion (10).

In the above configuration, the conductive power supply part (lO) and the internal conductor (1) form a capacitance (C1), and the internal conductor (1) becomes an inductance (shi), as shown in the equivalent circuit diagram of FIG. This becomes a series type CL circuit element (11).

This CL circuit element (11) connects the input terminal (13) and output terminal (14) to the conductive power supply part (10), and connects the external conductor (3) to the ground through the second separation band (5□). This results in a band rejection filter exhibiting the transmission characteristics shown in FIG.

In the above CL circuit element (11), the impedance Z due to the inductance (Ll) is given by the following equation (1).

Z L=j Z oe tanθ[Ω] ・(1)
In this formula (1), Zoe is the characteristic impedance of the coaxial line, Zoe and θ are the following formula (2)% formula % However, a is the outer diameter of the inner conductor (1) of the coaxial line (12).

b is the inner diameter of the outer conductor (3) of the coaxial line (12), E is the dielectric constant of the dielectric (4), and e is the base of the natural logarithm.

λg is the wavelength within the coaxial line (12), and Qe is the electrical length of the inductance (Ll). Here, the length of the internal conductor (1) which becomes the inductance (L,) is the length of the conductive power supply part (C4) which forms the capacitance (C4).
Q2. The width of the second release zone (5□) is d2
If Qe<ada<Qt, then approximately Qe:Ql.

As can be seen from equation (1), if Qe, that is, the length Q of the internal conductor (1), is λg O<Q<-, then ZL>0, and Zt is the inductance (Ll).

Next, the impedance due to the capacitance (C1) is given by the following equation (4).

In this formula (4), ω. is the frequency, C1 is the capacitance (
C1), and C1 is given by the following equation (5).

C = C, □Q2 [F co...(
5) log e − However, C01 is the capacitance per unit length (m), ξ. is the dielectric constant in vacuum.

Therefore.

If λK O × Ω2 (□), the conductive power supply part (10) and the internal conductor (1) have a sufficient function as a capacitance (C).When the CL circuit element (11) has series resonance, Since the condition is ZL+Zc::0, therefore.

Next, a second embodiment of the present invention will be described based on the drawings.

In Figures 6 and 7, (11) is the coaxial line (
The CL circuit element (11) consists of a cylindrical inner conductor (1), an outer conductor (2) (3), and a conductive power supply (lO). A coaxial line (
12), and this coaxial line (12) is connected to the inner conductor (1) by the cut top conductor (6) and bottom conductor (7).
) and the outer conductor (2) (3) are short-circuited, and between the outer conductor (2) (3), there is a first and second ′ separation band ( 5□) (5,
), and the conductive power supply portion (10) having a constant width is provided between the separation strips (5,) (5□). This sixth
The equivalent circuit of the C and L circuit elements (11) shown in Fig. 7 and Fig. 7 is expressed as shown in Fig. 8 using a coaxial line, and as shown in Fig. 4 when expressed using an inductance coil. Become. In FIG. 4, the capacitance (C1) required for series resonance is very approximately the capacitance (C, i) between the power supply part (10) and the external conductor (2) in the equivalent circuit diagram of FIG. The sum of the capacitance (CL□) between the power supply part (10) and the internal conductor (1), that is, C =
It is expressed as C z + cti. Here, C11 and C1□ are equivalent capacitors for forming C, and the following formula % formula % [] Next, 012 is C,, = Q, ・co, [F] as in the first embodiment. 0g- where a[ml is the outer diameter of the inner conductor (1) of the coaxial line (12), b[:ml is the outer conductor (2) of the coaxial line (12) (
3) Inner diameter.

K [kl is the complete elliptic integral of the first type d1 [III] is the peeling width of the first peeling zone (5,), C2
[111 is the conductor width of the power feeding section (10).

ff1o [F/m] is the dielectric constant in vacuum, ε is the dielectric material (4
), where e is the base of the natural logarithm.

Also, the impedance Zc created by the capacitance (C1) has a resonance frequency of ω. If so.

Next, the impedance zL due to the inductance (Ll) necessary for resonance with the impedance Zc created by the capacitance (C1) in FIG. 4 is given by an equation equivalent to equation (1) of the first embodiment.

ZL=j Zeo tanθ [Ωko 1st
As in the embodiment, series resonance occurs.

Next, a third embodiment of the present invention will be described based on the drawings.

In Figures 9 to 11, (11) is the coaxial line (
12), this CL circuit element (11) is connected between a cylindrical inner conductor (1), a square outer conductor (2) (3), and a conductive power supply part (10). is filled with a dielectric material (4) having a uniform permittivity, and this CL circuit element (11) is connected to the internal conductor (1) by the cut-out top conductor (6) and bottom conductor (7). The outer conductor (2) and the lower outer conductor (3) are shorted, and
Between these upper and lower external conductors (2) and (3), first and second peeling bands (51) are peeled off in a band shape and do not intersect with each other.
)(5□) are provided, and these first. Second release zone (
5,) (5□), the conductive power supply portion (10) is formed between them.

The second peeling band (58) is further formed in a concave shape so that the conductive power supply part (lO) protrudes and bites into the lower external conductor (3), so that the power supply part (10) has an integral part. A tongue portion (15) is formed. When the CL circuit element (11) configured as described above is developed, it appears as shown in FIG. The equivalent circuit that can be considered from the CL circuit element (11) having the shape shown in FIGS. 9 and 10 can be expressed using a capacitor and a coil as shown in FIGS. 12 to 15.
It will look like the figure. That is, the capacitance between the conductive power supply part (10) and the upper surface conductor (2) is
10) and the lower outer conductor (3), C2 is the capacitance between the tongue portion (15) and the lower outer conductor (3), C1 is the capacitance between the inner conductor (1), and the upper surface conductor (7).
) and the inductance due to the upper external conductor (2) is Ll, then C! When = 0, the equivalent circuit in Fig. 12,
When C3=0, the equivalent circuit shown in Fig. 13 is loud, and furthermore,
C,>01Cs>.

In this case, equivalent circuits as shown in FIGS. 14 and 15 can also be considered.

Note that the above-mentioned C construction includes not only the capacitance C1L between the power supply part (10) and the upper external conductor (2), but also the capacitance C12 on the inside, C13 up to the upper surface conductor (7), and the internal conductor (
The sum with C0 up to 1), that is, C2=C11+C1
□+c0. +c,.

It is expressed as C3 is almost determined by the width of the tongue portion (15), the groove width of the second separation band (5□), and its length = Also, Ll is the electrical length determined from the mechanical length Q1 in Figure 2. Qe, outer diameter a of inner conductor (1), outer conductor (2) (3
) is the equivalent inductance determined by the characteristic impedance determined from the dielectric constant ε of the dielectric (4).

In such a configuration, the electrical length Q0 of the lower external conductor (3) is smaller than λ/4 (λ is the resonance frequency) and larger than 0, which is +nλ×Ω in the general formula. <')(2n+1)λ (n=0,1,2
．． ), C3 becomes a capacitance.

Next, the equivalent circuits that can be considered from the CL circuit element (11) shown in FIG. 9 are the circuits shown in FIGS. 12 to 15. As shown in FIG. 18, the circuit of FIG. 14,
Three CL circuit elements and a series resonant band rejection filter (11) (1
1) (11) may be connected in cascade with inductors (LO) (LO) interposed between them.

Note that the tongue portion (15) and the lower external conductor (3) are connected to the second
When separated via a separation zone (52),
Said Denki Nagai. If is longer by λ/4, ie.

+ (2n+1)λ×Ω. 〈+(n+1)λ (n=o
, 1, 2. ), the tongue portion (15) has an equivalent inductance.

In addition, the outer shape of the inner conductor (1) can be elliptical, polygonal, or any other arbitrary shape in addition to the cylindrical shape. ) can similarly be any shape other than a rectangle. Further, the tongue portion (15) is connected to the power feeding portion (1
It is not limited to the case where it extends at right angles from 0), but it may be arbitrarily bent as shown in FIG. Further, the number of tongue portions (15) is not limited to one, but may be two or more as shown by the chain line in FIG.

Next, a fourth embodiment of the present invention will be described. Figure 20 shows
An example is shown in which the tongue portion (15) is integrally connected to the lower external conductor (3). In this way - when connected to the body.

+nλkuα. <+(2n+1)λ (n=o, 1, 2.
...), this tongue portion (15) has an inductance L2. This L2 is determined by the length and width of the tongue portion (15) and the groove width of the second peeling bands (5□) on both sides thereof. The equivalent circuit that can be considered from this Figure 20 is C2
In addition to the circuit shown in FIG. 22 when χ0, the circuits shown in FIGS. 2 and 24 are also conceivable when C2>0.

Such a CL circuit element (1]) connects the input/output terminals (i3) (14) to the power supply part (10) and connects the lower external conductor (
When 3) is connected to ground, it operates as a high-frequency rejection filter circuit as shown in the characteristic diagram of FIG.

When configuring a filter circuit as shown in FIG. 26, as shown in FIG. 27, three CL circuit elements ( 11
)(11) Inductor (shi, ) with (11) in the middle
(Lo) may be used for cascade connection.

In addition, in the case where the tongue portion (15) and the outer conductor (3) are integrally connected, the electrical length Q. is longer by λ/4, i.e. +(2n+1)λ< Q o < z (n+1)λ
In the case of (n=0.l, 2..=), the tongue portion (15) has an equivalent capacitance.

Furthermore, if the filter circuit shown in Fig. 12 and the filter circuit shown in Fig. 27 are connected in combination through an inductor L (L) and a capacitor (2CO), an antenna duplexer as shown in Fig. 28 can be obtained. becomes.

Note that the tongue portion (15) may be arbitrarily bent as shown in FIG. 29. Further, the number of tongue pieces (15) is not limited to one, but two or more can be formed as shown by the chain line in FIG.

Next, a fifth embodiment of the present invention will be described based on the drawings.

In FIGS. 30 and 31, (11) shows the entire CL circuit element consisting of a coaxial line (12), and this CL
The circuit element (11) includes an outer conductor (3) and a conductive power supply part (10) whose tips are tapered upward in the figure, and an inner conductor (1) whose tips are also tapered upward in a small diameter.
A dielectric (4) is filled between the CL circuit element (1) and
1) The top surface conductor (7) is peeled off, and the first peeled part (5
1) and the outer conductor (3) by the bottom conductor (6)
and the inner conductor (1) are short-circuited, and the outer conductor (3) is short-circuited between the conductive power supply part (10) and the outer conductor (3).
A second circumferential release strip (52) is provided.

In Fig. 2, the upper part of the 5 dielectric (4) includes a point below the inner periphery (Pt), a point coincident with the inner periphery (P2), a point coincident with the outer periphery (P,), and a point below the outer periphery. Point (P4)
, the upper end (E) of the internal conductor (1) can be located at any point within these points (Pl) to (P4) as long as the first peeled part (5□) exists. It may be extended to the position. Conversely, if there is a first peeled part (51) between the upper end (E2) of the power feeding part (4) and the internal conductor (1), any of the points (Pl)-(P4) It may be extended to any position. CL shown in Fig. 30 and Fig. 31
Equivalent circuits considered from the circuit element (11) can be expressed using C and L as shown in FIGS. 4 and 13. In other words, the capacitance between the power supply section (10) and the internal conductor (1) is C, and the capacitance between the power supply section (10) and the external conductor (3) is C2.

Also, the electrical length of the mechanical length Q1 of the internal conductor (1) is αe
Then, +nλ< Q e < + (2n+ 1 )λ (n
If the inductance due to the inner conductor (1) and the outer conductor (3) at the time of "otttzt"' is Ll, then C,=
When O, the equivalent circuit shown in Figure 4 is shown, and when C,>O, the equivalent circuit shown in Figure 13 is shown.
This is the equivalent circuit shown in the figure. Note that the capacitance C1, C,
, the inductance L1 is determined by the shape and dimensions of each part and the dielectric constant of the dielectric (4). The transmission characteristics in the equivalent circuit of FIG. 4 show the transmission characteristics of a band rejection filter that blocks the passage of signals near frequency f0, as shown in the characteristic diagram of FIG. 5, and the transmission characteristics in the equivalent circuit of FIG. As shown in the characteristic diagram in the figure, the transmission characteristics of a band rejection filter for low frequency (f) rejection and high frequency (f2) passage are shown.

Next, a sixth embodiment of the present invention will be described. The one shown in FIG.
In the CL circuit element (11) in Figure 0, the power supply part (lO)
A second separation band (5□) between the outer conductor (3) and the outer conductor (3) is formed in a concave shape, and the electric wire is integrally connected to the power supply part (10). You can see the tongue part (15) of the CL circuit element (15).
1). The equivalent circuit that can be considered from this CL circuit element (11) can be expressed using C and L as shown in Figure 12 or 2.
It will look like Figure 4. That is, the capacitance between the power supply part (lO) and the internal conductor (1) is C, and the power supply part (10)
and the outer conductor (3) is 02, the capacitance between the tongue portion (15) and the outer conductor (3) is C1, and the inductance due to the inner conductor (1) and the outer conductor (3) is Ll. Then, the electrical length Q of the tongue part (15)
0 is +nλ< Q o < + (2n”l)λ (n”0
+L2+"'), the tongue portion (15) acts as a capacitance C1. In addition, λ is the wavelength of the resonant frequency. In this case, when C,=O, the equivalent circuit of FIG. 12, C2>0 When , the equivalent circuit is shown in Fig. 14 or 15. Also, the electrical length Ω is ”, (2n+1)λ<L<+(n+1)λ (n=0
,1,2. ), the space between the tongue portion (15) and the external conductor (3) acts as an inductance L3 instead of a capacitance C3. In this case, C2=0
When C2〉0, the equivalent circuit shown in Fig. 22, and when C2〉0, the first
The equivalent circuit is shown in FIG. 5 or 24.

In the above equivalent circuits, the equivalent circuits in FIGS. 12, 14, and 15 are equivalent to the equivalent circuit in FIG. 13, so the transmission characteristics in FIGS. 12, 14, and 15 are is the 161st! It shows the same transmission characteristics as 1.

The transmission characteristics of the equivalent circuit in Fig. 22 are as shown in Fig. 25, which shows the transmission characteristics of a band rejection filter for high frequency (f2) rejection and low frequency (fl) passage, and the equivalent circuits of Figures 8 and 24. The transmission characteristics of FIG. 16 or 25 are shown depending on the values of C, , C, , L□, and .

The CL circuit element (11) itself constitutes a filter circuit, but when constructing a multistage filter circuit as shown in Fig. 17 using this element' (11), the circuit in Fig. 14 and the Three CL circuit elements (11) (11) (11) may be connected in cascade in the order of the circuit shown in FIG. 15 and the circuit shown in FIG. 14 with an inductor (t, +) (Lo) interposed between them.

Next, a seventh embodiment of the present invention will be described. What is shown in FIG. 33 is the tongue portion (1) of the CL circuit element (11) in FIG.
The tip of the CL circuit element (11) is short-circuited to the external conductor (3).
The equivalent circuit considered from 1) is that the electrical length Q0 of the tongue portion (15) is +nλ×Ω. < + (2n+1)λ (n=0,1,
2. ), the CL circuit element (11
), which acts as an inductance L, and becomes the equivalent circuit shown in FIGS. 22 to 24, with the electrical length n of the tongue portion (15). is + (2n 41)λ< Q a < + (
When n+1)λ (n: 0, 1, 2...), it acts as a capacitance C1, as shown in FIG.

The equivalent circuits are shown in FIGS. 14 and 15.

The 25th transmission characteristic obtained from the equivalent circuit in Figure 22 is
A diagram is obtained. Further, as the transmission characteristics obtained from FIGS. 23 and 24, the transmission characteristics shown in FIG. 16 or 25 can be obtained depending on the values of C1, C, and L. Since the transmission characteristics obtained from the equivalent circuits of FIGS. 12, 14, and 15 are equivalent to those of FIG. 13, FIG. 16 is obtained.

The CL circuit element (11) itself constitutes a filter circuit, but when constructing a multi-stage filter circuit as shown in Fig. 26 using this element (11), the circuit of Fig. 23 and the circuit of Fig. 3 cL in the order of the circuit in Figure 24 and the circuit in Figure 23.
The circuit elements (11) (11) (11) may be connected in cascade with an inductor (LO) (L(1) interposed between them).

Moreover, if the filter circuit shown in FIG. 17 and the filter circuit shown in FIG. 26 are connected in combination with an inductor (L, ) (to) and a capacitor (2C(1) interposed), the result as shown in FIG. It becomes an antenna duplexer.

In the above embodiments, the CL circuit element has a shape in which the tip is tapered upward, but the shape is not limited to this. For example, as shown in Fig. 34, a cylindrical inner conductor (1) and a square tubular outer conductor (2) (3
) is filled with a dielectric (4), and a release zone (5,) (
5□) with a stepped portion formed, a cylindrical internal conductor (1), a cylindrical power supply part (10), and 4 as shown in Fig. 35.
A dielectric (4) is filled between the rectangular cylindrical outer conductors (2) and (3), and a stepped portion is formed in the separation zone (51)-(5□), and the inner conductor (1) and the outer Conductor (2) (3) in other polygonal, elliptical, etc. shapes, internal conductor (1)
It may be shifted from the center. Further, the shape of the tongue portion (15) is not limited to a straight line, and if necessary, it may be formed into a meandering shape as shown in FIGS. 19 and 29, or may be formed into a spiral shape or other shape (not shown). . The dielectric (4) does not need to have a uniform dielectric constant as long as it does not change over time.

The number of tongue pieces (15) is not limited to one, but two or more may be formed.

Note that the capacitance C1 in FIG. 31 is actually not just the one shown in the diagram, but also the capacitance C1 shown in FIG.
It is the sum of 1□, C1□, CLl, and C1, and becomes C-work; C-work, +C1□+C43+C14.

Similarly, as shown in FIG. 24, the capacitance C2 becomes C2''C21''C2□.

The various shapes of external conductors (2) (3), internal conductors (
1), CL circuit element (
11), but the invention is not limited to these examples, and has outer conductors (2) and (3) and an inner conductor (1), and conductors (6) and (7) on the top and bottom parts. Short circuit, outer conductor (2) (3) or top conductor (7)
The first and second separation bands (51) (5□) may be provided in any shape as long as they form capacitance and inductance.

"Effects of the Invention" Since the present invention is constructed as described above, a compact antenna duplexer required for a wireless device with a narrow transmission/reception frequency interval can be constructed in an extremely small size. It can be constructed using circuit elements.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a perspective view of a CL circuit element of the first embodiment, FIG. 2 is a sectional view of FIG. 1,
Figures 3 and 4 are equivalent circuit diagrams of the CL circuit element in Figure 1, Figure 5 is a frequency-transmission characteristic diagram of the circuit in Figure 4, and Figure 6 is the CL circuit element of the second embodiment. , FIG. 7 is a sectional view of FIG. 6, FIG. 8 is an equivalent circuit diagram of the CL circuit element of FIG. 6, FIG. 9 is a perspective view of the third embodiment, and FIG. 10 is a sectional view of FIG. , TI is a developed view of FIG. 9, FIGS. 12 to 15 are equivalent circuit diagrams of the CL circuit element in FIG. 9, and FIG. 16 is a frequency diagram of the circuit in FIGS. 12 to 15. -Transmission amount characteristic diagram, Fig. 17 is a circuit diagram of a filter following the CL circuit element of Fig. 9, Fig. 18 is a front view of a filter circuit following the CL circuit element of Fig. 9, Fig. 19 is a front view showing another aspect of the third embodiment, FIG. 20 is a perspective view of the fourth embodiment, FIG. 21 is a developed view of FIG. 20, and FIGS.
Figure 4 is an equivalent circuit diagram of the CL circuit element in Figure 20, Figure 25 is a frequency-transmission characteristic diagram of the equivalent circuits in Figures 22 to 24, and Figure 26 is an equivalent circuit diagram of the CL circuit element in Figure 20. Fig. 27 is a front view of a filter circuit which is followed by the CL circuit element shown in Fig. 20, and Fig. 28 is an antenna duplexer which is followed by the CL circuit element shown in Figs. 9 and 20. 29 is a front view showing another aspect of the fourth embodiment, FIG. 30 is a perspective view of the fifth embodiment, FIG. 31 is a sectional view of FIG. A perspective view of the embodiment, FIG. 33 is the seventh
FIGS. 34 and 35 are perspective views of still another embodiment, and FIGS. 36 and 37 are cross-sectional views for explaining details of the capacitance. (1)...Inner conductor, (2)...Upper outer conductor,
(3)... lower external conductor, (4)... dielectric,
(5,)...First release band, (54)...Second release band, (6)...Bottom part conductor, (7)...Top part conductor, (10)...・Conductive power supply part, (11)...CL
Circuit element, (12)... Coaxial line, (13)...
・Input terminal, (14)... Output terminal, (15)...
Tongue piece. Figure 3, Figure 5
Figure 20
22 2nd Figure 23 Figure 24
Figure 25 Figure 36 C, = C, , + C ro + C ro + CI4 Figure 37 C2 = C3 - C22

Claims (7)

[Claims] (1) A dielectric material having a uniform dielectric constant is filled between the inner conductor and the outer conductor to form a coaxial line, the inner conductor and the outer conductor are short-circuited at the bottom of the coaxial line, and the area around the outer conductor is A CL circuit element, characterized in that a first separation band and a second separation band that do not intersect with each other are formed, and an external conductor between these separation bands serves as a conductive power supply portion. (2) The CL circuit element according to claim 1, wherein the first and second separation bands are formed on the conductor on the upper surface of the coaxial line. (3) The CL circuit element according to claim 1, wherein the first separation band is formed on the conductor on the upper surface of the coaxial line, and the second separation band is formed on the outer conductor. (4) The CL according to claim 1, wherein the first and second release bands are both formed on the outer conductor.
circuit element. (5) A coaxial line is formed by filling a dielectric material having a uniform dielectric constant between the inner conductor and the outer conductor, and the inner conductor and the outer conductor are short-circuited at the bottom of the coaxial line, and the inner conductor and the outer conductor are short-circuited at the bottom of the coaxial line. , a first separation band and a second separation band that do not intersect with each other are formed, and the external conductor between these separation bands serves as a conductive power supply part, and this conductive power supply part has a tongue protruding toward the external conductor side. 1. A series resonant band-rejection filter, comprising a conductive power feeding section, an input terminal and an output terminal coupled to the conductive power feeding section, and an external conductor coupled to ground. (6) The series resonant band rejection filter according to claim 5, wherein the tongue portion is separated from the external conductor by a separation band to operate as a capacitor. (7) The series resonant band rejection filter according to claim 5, wherein the tongue portion is integrally connected to the external conductor at the tip portion to operate as an inductor.