JP2002009507A - Multi-frequency branching filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-frequency branching filter that is more downsized than a conventional multi-frequency branching filter without deteriorating its electric characteristic and can reduce its loss. SOLUTION: The multi-frequency branching filter has a 1st band pass filter that passes a 1st high frequency signal with a wavelength of λL, a 2nd band pass filter that is connected to a common terminal via a transmission line and passes a high frequency signal with a 2nd frequency higher than the 1st high frequency and whose wavelength is λHL, and a 3rd band pass filter that is connected to the common terminal via the transmission line and passes a high frequency signal with a 3rd frequency higher than the 2nd frequency and whose wavelength is λHH. The length of a coupling line in the 1st band pass filter is (λHL+λHH /8, the length of a coupling line in the 2nd band pass filter is (λHH/4), the length of a coupling line in the 3rd band pass filter is (λHL/4), and the length of the transmission line is (λLL/4)-(λHH/4).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-frequency demultiplexer, and more particularly to a technique effective in demultiplexing a multi-frequency high-frequency signal in, for example, radio communication equipment, mobile communication base station equipment and the like. .

[0002]

2. Description of the Related Art FIG. 17 is a diagram for explaining a schematic configuration of a conventional multi-frequency splitter. Note that in FIG.
1. 9 GHz band signal, 1.5 GHz band signal, and
A case where a signal in the 0 GHz band is split will be described. As shown in FIG. 2, the signal is input from a common terminal (Tc).
The signal in the 0 GHz band is a band-pass filter (hereinafter simply referred to as BPF) 23 that allows the signal in the 2.0 GHz band to pass through.
The signal passes through 0p and is output from the terminal (T ₃₁ ). Also,
The signals in the 0.9 GHz band and the signals in the 1.5 GHz band input from the common terminal (Tc) pass through a band elimination filter (hereinafter, simply referred to as BEF) 230 e that removes the signal in the 2.0 GHz band. Output from the terminal (T ₃₂ ). The 1.5 GHz band signal output from the terminal (T ₃₂ ) and input to the terminal (T ₂₀ ) passes through the BPF 220 p that allows the 1.5 GHz band signal to pass, and is output from the terminal (T ₂₁ ). . The 0.9 GHz band signal output from the terminal (T ₃₂ ) and input to the terminal (T ₂₀ ) is 1.5
After passing through the BEF 220e which removes the signal in the GHz band,
Output from the terminal (T ₂₂ ). The signal in the 0.9 GHz band output from the terminal (T ₂₂ ) and input to the terminal (T ₁₀ ) is a BPF 210p that passes a signal in the 0.9 GHz band.
And output from the terminal (T ₁₁ ).

[0003]

However, in the above-mentioned conventional multi-frequency demultiplexer, three BPFs (210p,
220p, 230p) and two BEFs (210e, 2p).
20e) constituted a multi-frequency demultiplexer. Therefore, the conventional multi-frequency demultiplexer has a problem that the size is increased as a whole and the number of the resonance circuit elements is increased, so that the loss is large. On the other hand, in a mobile communication system,
It has been studied to install a relay antenna in a tunnel or in a building in order to enable use of the terminal device in a tunnel or in a building, or to take measures against non-sensing. Even when such a relay antenna is installed, a multi-frequency splitter is required, but such a multi-frequency splitter is required to be small in size and low in loss. However, the conventional multi-frequency demultiplexer described above is
Because of its large size and large loss, there is a problem that it is unsuitable for the above-mentioned applications.

[0004] Therefore, the inventor of the present application has proposed a compact,
As a low-loss multi-frequency duplexer, a multi-frequency duplexer shown in FIG. 18 was prototyped. FIG. 18 is a diagram for explaining a multifrequency duplexer prototyped by the inventor of the present application before filing the present application. In the figure, reference numeral 310 denotes a BPF that passes a signal in the 0.9 GHz band, 320 denotes a BPF that passes a signal in the 1.5 GHz band, and 330 denotes a BPF that passes a signal in the 2.0 GHz band. The multi-frequency splitter shown in FIG. 18 includes three BPFs (310, 320, 330),
Each is connected to a common terminal (Tc). According to the multi-frequency demultiplexer shown in FIG. 18, no BEF is required as compared with the multi-frequency demultiplexer shown in FIG. 17, so that the overall size can be reduced and a resonance circuit element for the BEF is required. Because there is no loss, the loss can be reduced.

However, three BPFs (310, 3
20, 330) is composed of a comb-line BPF or an inter-digital BPF.
The PF or the interdigital BPF has a coupling line (or coupling loop element) inside.
This coupling line is set to a wavelength that is one fourth of the wavelength of the high-frequency signal passing through the BPF. For example,
In the case of the BPF 320 that allows a signal in the 1.5 GHz band to pass therethrough, the line length of the internal coupling line is a quarter (50 (= 2) of the wavelength (200 mm) of the 1.5 GHz signal.
00/4) mm). In FIG. 18,
l _2.0 ≒ 38 mm is the line length of the coupled line inside the BPF 330, l _1.5 ≒ 50 mm is the line length of the coupled line inside the BPF 320, and l _0.9 ≒ 83 mm is the BPF 31
0 shows the line length of the coupled line inside.

That is, the line length (83 mm) of the coupling line inside the BPF 310 is set to a wavelength of 2.0 GHz (150 m).
m) is close to half the wavelength (75 (= 150/2)), and the tip of the internal coupling line is connected to the BPF housing, and the tip of the internal coupling line is at the reference potential (earth). (That is, the terminal is short-circuited). Therefore, the multi-frequency demultiplexer shown in FIG. 18 has a problem that, when viewed from the common terminal, the signal of 2 GHz is short-circuited by the coupling line inside the BPF 310, and the characteristics of the signal of 2 GHz deteriorate. The present invention has been made to solve the problems of the prior art, and an object of the present invention is to reduce the size of the conventional device without lowering the electrical characteristics, and
An object of the present invention is to provide a multi-frequency demultiplexer capable of reducing a loss. The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0007]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows. That is, the present invention provides m (m ≧ 2) band-pass filters each having a coupling line internally connected to a common terminal, and a connection point between the common terminal and the coupling line of the m band-pass filters. A transmission line having one end connected thereto, and n (n ≧ 2) band-pass filters each having therein a coupling line connected to the other end of the transmission line, Each of the n band-pass filters is a multi-frequency demultiplexer that passes a high-frequency signal higher in frequency than each of the m band-pass filters.
The line length of the coupling line in each of the band-pass filters is defined as the length of the high-frequency signal passing through each of the n band-pass filters from one end of the transmission line to the short-circuit end at the end of the coupling line. The length of the transmission line is set to a length at which the impedance becomes substantially infinite, and the line length of the transmission line is set to be n from one end of the transmission line in each of the high-frequency signals passing through the m band-pass filters. It is characterized in that the impedance is set to a length at which the impedance up to the short-circuit end at the end of the shortest coupling line among the coupling lines in each band-pass filter becomes substantially infinite.

Further, the present invention provides a first band-pass filter having a coupling line connected to a common terminal therein for passing a first high-frequency signal having a wavelength of λ _L; The first band-pass filter includes a transmission line having one end connected to a connection point with the coupling line, and a coupling line internally connected to the other end of the transmission line. A second band-pass filter for passing a high-frequency signal of a second frequency having a wavelength of λ _HL at a frequency higher than the frequency of _HL , and a coupling line internally connected to the other end of the transmission line. A third band-pass filter that passes a high-frequency signal having a frequency higher than the second frequency and a third frequency having a wavelength of λ _HH , wherein: pass filter, the line length of the inside of the coupling line is (λ _HL + λ _HH A / 8, the second band-pass filter, the line length of the inside of the coupling line is (lambda _HH / 4)
In the third band pass filter, the line length of the internal coupling line is (λ _HL / 4), and the line length of the transmission line is (λ _LL / 4) − (λ _HH / 4). It is characterized by being.

Further, the present invention has a structure in which a common terminal is internally connected.
And the wavelength is λ_LLThe first high-frequency signal
1st band pass filter that passes the signal
A coupling line connected to a terminal;
High frequency, wavelength λ_LHThrough the second high-frequency signal
A second band-pass filter passing through the common terminal;
The first band pass filter and the second band pass
One end is connected to the connection point of the filter with the coupling line.
Connected to the other end of the transmission line.
Having a coupled line connected thereto and having a higher frequency than the second frequency.
Wave, wavelength λ _HLThrough the high frequency signal of the third frequency
A third band-pass filter having the transmission line therein
A coupled line connected to the other end of the road,
Higher than the frequency of_HHThe fourth frequency that is
A fourth band-pass filter for passing a number of high-frequency signals;
A multi-frequency demultiplexer having the first and second
In the band-pass filter, the line length of the internal coupling line is (λ_HL
+ Λ_HH) / 8, wherein the third bandpass filter is:
The line length of the internal coupling line is (λ_HH/ 4), and the
The bandpass filter of No. 4 has a line length of the internal coupling line.
(Λ_HL/ 4), and the transmission line has a line length of (λ_LL
/ 4)-(λ_HH/ 4).

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments, components having the same functions are denoted by the same reference numerals, and repeated description thereof will be omitted. [First Embodiment] FIG. 1 is a diagram showing a schematic configuration of an example of a multifrequency duplexer according to a first embodiment of the present invention. The multi-frequency demultiplexer shown in FIG. 1 is a multi-frequency demultiplexer in the case of common use for transmission. Like the multi-frequency demultiplexer shown in FIG.
GHz band signal, 1.5 GHz band signal, and 2.0
The multi-frequency demultiplexer according to the present embodiment will be described using a case where a signal in the GHz band is demultiplexed as an example. In the figure,
110 is a BPF for passing a signal in the 0.9 GHz band,
120 is a BPF for passing a signal in the 1.5 GHz band,
Reference numeral 130 denotes a BPF that allows a signal in the 2.0 GHz band to pass. Reference numeral 2 denotes a housing, and the housing 2 and an internal conductor (11
_{1 to} 11 ₄ ), which allows a signal in the 0.9 GHz band to pass through
PF110 is out with the housing 2 and the inner conductor (12 ₁ to 12 _4), passing signals in a 1.5GHz band BPF120
But out with casing 2 and the inner conductor (13 ₁ ~13 _4), 2.0G
The BPF 130 that passes a signal in the Hz band is configured. 24 is a BPF 110 and a BPF (120, 1
30) is a transmission line composed of a coaxial cable, a microstrip line, and the like.

Reference numeral 21 denotes a coupling line inside the BPF 110 connected to the common terminal (Tc), and reference numeral 25 denotes a terminal (Tc).
_0.9 ), a coupled line inside the BPF 110 connected to
2 is a BPF 1 connected to the other end of the transmission line 24.
20 is a coupled line inside the BPF 120 connected to the terminal (T _1.5 ), 23 is a coupled line inside the BPF 130 connected to the other end of the transmission line 24, and 27 is a coupled line inside the BPF 130 connected to the other end of the transmission line 24. , BPF1 connected to terminal (T ₂ )
30 is a coupling line inside. The _0.9 GHz band signal input from the common terminal (Tc) passes through the BPF 110, is output from the terminal (T _0.9 ), and is supplied to the antenna. Similarly, 1.5 input from the common terminal (Tc)
The signal in the GHz band passes through the BPF 120 and is supplied to the terminal (T
_1.5 ), and a signal in the 2.0 GHz band input from the common terminal (Tc) passes through the BPF 130, is output from the terminal (T ₂ ), and is supplied to the antenna. These BPFs (110, 120, 130)
Is a comb-line type BPF, and each BPF (110,
FIG. 2 shows an example of the damping characteristics of (120, 130).

FIG. 3 shows each BPF (110, 1) shown in FIG.
20 and 130) are diagrams for explaining the line length of the coupled line and the line length of the transmission line 24. In FIG. 3, l ₂₃ ≒ 50 mm is the line length of the coupling line 23 inside the BPF 130, l ₂₂ ≒ 38 mm is the line length of the coupling line 22 inside the BPF 120, and l ₂₁ ≒ 44 mm is the BP
The line length of the coupling line 21 inside the F110 is l ₂₄ ≒ 45
mm indicates the line length of the transmission line 24. Each line length shown in FIG. 3 is obtained by the following equations (1) and (2).

## EQU1 ## l ₂₁ = (λ _1.5 / 4 + λ _2.0 / 4) / 2 = (λ _1.5 + λ _2.0 ) / 8 l ₂₂ = λ _2.0 / 4 l ₂₃ = λ _1.5 / 4 l ₂₄ = λ _0.9 / 4-λ _2.0 / 4 (1) where λ _0.9 , λ _1.5 and λ _2.0 are _0.9 GH
z, 1.5 GHz, and 2 GHz, and λ _0.9 ≒ 33 mm, λ _1.5 ≒ 200 mm, λ _0.9
By substituting _2.0 ≒ 150 mm, the following equation (2) is obtained.

[0013]

L ₂₁ = (λ _1.5 + λ _2.0 ) / 8 = (200 + 150) / 8 ≒ 44 mm l ₂₂ = λ _2.0 / 4 = 150/4 ≒ 38 mm l ₂₃ = λ _1.5 / 4 = 200/4 ≒ 50 mm l ₂₄ = λ _0.9 / 4-λ _2.0 / 4 = (333-150) / 4 ≒ 45 mm (2)

In the multi-frequency splitter shown in FIG. 1, a BPF 1 is connected to a branch point (B1) connected to a common terminal (Tc).
The line length up to the short-circuited end of the coupled line 21 inside 44 is 44
mm, λ _1.5 / 4 (≒ 50 mm), and λ _2.0 /
4 (≒ 38 mm), the BP viewed from the branch point (B1) at 1.5 GHz and 2.0 GHz
The impedance up to the short-circuited end of the coupling line 21 of F110 becomes substantially infinite. Thereby, the degradation of the 1.5 GHz band signal and the 2.0 GHz band signal by the BPF 110 can be prevented. The line length from the branch point (B1) connected to the common terminal (Tc) to the short-circuit end of the coupling line 121 inside the BPF 120 via the transmission line 24 is 83 (45 + 38) mm, and λ _0.9 / 4 ($ 83mm)
BPF1 viewed from the branch point (B1) at 0.9 GHz
The impedance up to the short-circuit end at the end of the 20 coupling lines 121 becomes substantially infinite. Thereby, the BPF (120,
130), it is possible to prevent the deterioration of the signal in the 0.9 GHz band. Furthermore, since the line length of the coupling line 121 of the BPF 120 is set to (λ _2.0 / 4) and the line length of the coupling line 131 of the BPF 130 is set to (λ _1.5 / 4), the signal in the 2 GHz band is deteriorated compared to the BPF 120, and It is possible to prevent the signal in the 1.5 GHz band from being deteriorated by the BPF 130.

FIG. 4 is a diagram showing a schematic configuration of another example of the multi-frequency demultiplexer according to the first embodiment of the present invention. The multi-frequency demultiplexer shown in FIG. 4 is different from the multi-frequency demultiplexer shown in FIG. 1 in that a BPF 100 for passing a signal in the 0.8 GHz band is added in parallel with a BPF 110 for passing a signal in the 0.9 GHz band. Different from the vessel. The BPF 100 includes a housing 2 and internal conductors (10 ₁ to 10 ₄ ), and 20 is a common terminal (T
c) a coupled line inside the BPF 100 connected to
Is a coupled line inside the BPF 100 connected to the terminal (T _0.8 ). Each BPF (100, 11) shown in FIG.
0, 120, and 130) are shown in FIG.
Further, each of the BPFs (100, 110, 120,
FIG. 6 shows the line length of the coupling line 130) and the line length of the transmission line 24. As shown in FIG. 6, in the multi-frequency splitter shown in FIG. 4, the line length (l ₂₀ ) of the coupling line 20 inside the BPF 100 is 44 mm, like the line length (l ₂₁ ) of the coupling line 21 of the BPF 110. It is said. The same effect as that shown in FIG. 1 can be obtained by the multi-frequency splitter shown in FIG. In addition, similarly to the case shown in FIG.
Is added, it is possible to configure a multi-frequency splitter that splits 5, 6, 7, and 8 waves. in this way,
According to the multi-frequency demultiplexer of the present embodiment, it is possible to reduce the size and reduce the loss without deteriorating the electrical characteristics, and to further reduce the cost. It becomes possible.

In the above description, the case where the multi-frequency transmission wave is demultiplexed has been described. However, the case where the multi-frequency reception wave is demultiplexed or the multi-frequency transmission and reception wave is demultiplexed is also described. The present invention is applicable. When demultiplexing a multi-frequency transmission / reception wave, each BPF (100, 110, 120,
Since the pass band of 130) needs to be widened, an interdigital BPF is suitable. FIG. 7 is a sectional view of a main part showing a schematic structure of an interdigital type BPF.
FIG. 3A is a cross-sectional view of a main part cut along a plane along the length direction of the resonance rod, and FIG. 3B is a cross-sectional view of a main part cut along a plane perpendicular to the length direction of the resonance rod. In FIG. 8, reference numeral 1 denotes a resonance rod, 2 denotes a housing, 3 denotes a coupling line (coupling loop), and 4 denotes an input connector. FIG. 8 shows an interdigital BPF equalizing circuit. Next, as shown in FIG. 9, the interval between the resonance bars 1 is D, the diameter of the resonance bar 1 is d, and the length l of the resonance bar 1.
Where λo / 4 (λo is the resonance frequency) and the width of the housing 2 is W, the inter-stage coupling coefficient (M _{k, k + 1} ) of the interdigital BPF is expressed by the following equation (3). You.

[0017]

M _{k, k + 1} = M _{Ek, k + 1} + M _{Hk, k + 1} M _{Ek, k + 1} = 10 ^{Mek, k + 1} M _{ek, k + 1} = (− 1.37D _{k , k + 1 /W+0.91d/W-0.048) M Hk,} k + 1 = 10 -LH / 20 LH = 54.6D k, k + 1 (1-0.3d / W) F (λo) / 2WF (λo) = (1− (2W / λo) ² ) ^1/2 (3) where M _{Ek, k + 1} is an interstage electric field coupling coefficient, _{MHk, k + 1} is an interstage magnetic field coupling coefficient, and LH is an interstage magnetic field attenuation.

FIG. 10 is a sectional view of a principal part showing a schematic structure of a comb line type BPF. FIG. 10A is a sectional view of the principal part cut along a plane along the length direction of the resonance rod. FIG. 2B is a cross-sectional view of a main part taken along a plane perpendicular to the length direction of the resonance rod. In FIG. 11, reference numeral 2 denotes a housing, 3 denotes a coupling line (coupling loop), 4 denotes an input connector, and 5 denotes an internal conductor. FIG. 11 shows an equalizing circuit of this comb-line type BPF. next,
As shown in FIG. 12, the interval between the internal conductors 5 is D, the diameter of the internal conductor 5 is d, the length 1 of the internal conductor 5 is λo / 4 (λo is the resonance frequency), and the width of the housing 2 is W. At this time, the inter-stage magnetic field coupling coefficient (M _{Hk, k + 1} ) of the comb line type BPF is expressed by the following equation (4).

^MH _{k, k + 1} = 10 ^{−LH / 20} LH = 54.6D _{k , k + 1} (1−0.3d / W) F (λo) / 2W F (λo) = (1- ( 2W / λo) ² ) ^1/2 (4) where LH is the magnetic field attenuation.

Next, a description will be given of a case in which a BPF having a passband shown in FIG. 13 having a Chievishev characteristic and an attenuation band having a Wagner-type characteristic is designed based on the Chiebishev-type normalized low-pass filter. Assuming that the voltage standing wave ratio (VSWR) in the pass band allowed in the design of the BPF is S, the allowable ripple L _r in the pass band is represented by the following equation (5).

Equation 5] with obtaining the allowable ripple L _r from _{L r = 10log ((s +} 1) 2 / 4S) ··········· (5) This Equation 5, defines the circuit order n, the following From the equation (6), the element values g ₁ to g _n
Ask for.

G ₁ = 2a ₁ / γ g _k = (4 a _k−1 a _k ) / b _k−1 b _k (k = 1, 2,..., N) γ = sinh (β / 2n) β = ln (coth (L _r /13.37)) a _k = sin ((2k−1) π / 2n) b _k = γ ² + sin ² (kπ / n)・ ・ ・ ・ ・ ・ ・ ・ ・ (6)

The element values g ₁ to g _n obtained by the above equation (6), the required center frequency f _{o of} the BPF, and the pass bandwidth B
_{From wr} , the inter-stage coupling coefficient M _{k, k + 1} can be obtained by the following equation (7).

M _{k , k + 1} = (4 / g _k g _{k + 1} ) ^1/2 B _wr / f _o (7) The transmission characteristic of the BPF created using the above equations and having a passband of the Chibishev type characteristic and an attenuation band of the Wagner type characteristic can be obtained by the following equation (8).

ATT = 10 log (1+ (S−1) ² T ² _n (x) / 4S) T _n (x) = cosh ² ( _n cos ⁻¹ x) x = B _wr (f / f _o −f _{o) / f) / f o ····················· (} 8) where, ATT transmission loss, T _n (x) is a polynomial of Chiebishiefu, f _o Is a center frequency in a pass band of the BPF, f is an arbitrary frequency, and _Bwr is an allowable pass frequency bandwidth of the BPF.

[Embodiment 2] FIG. 14 shows an embodiment of the present invention.
FIG. 9 is a cross-sectional view of a principal part showing a configuration of a multifrequency duplexer according to a second embodiment.
FIG. 3A shows a plane orthogonal to the length direction of the inner conductor.
FIG. 4B is a sectional view of a main part showing a cut section, and FIG.
Main section showing a section cut along a plane along the length of the body
FIG. In the figure, 7 is provided inside the housing 2.
The housing 2, the partition 7, and the inner conductor (11₁~
11_Four) And a BP that allows signals in the 0.9 GHz band to pass
F110 is the housing 2, the partition 7, and the inner conductor (12₁~ 1
2_Four) And a BPF that allows signals in the 1.5 GHz band to pass
120 is the housing 2, the partition 7, and the inner conductor (13₁~ 1
3_Four) And a BPF that allows signals in the 2.0 GHz band to pass
130 are respectively configured. Multi-frequency component of this embodiment
The wave device has an inner conductor (11₁~ 11_Four) And inner conductor (12 ₁
~ 12_Four) Are arranged in a U-shape, and the housing 2 is
It is designed to be more compact by passing through. The connection line
The line lengths of the roads (21, 22, 23) are as described above.
Set to length. Further, the transmission line 24 has a strip shape.
And the line length of the transmission line 24 is also
The length is set to Also in the present embodiment,
Operation and effect similar to those of the first embodiment can be obtained.
It is. In FIG. 14, 31 to 35 are resonance frequencies.
This is a number adjustment screw.

[Embodiment 3] FIG. 15 shows an embodiment of the present invention.
FIG. 9 is a sectional view of a principal part showing a configuration of a multifrequency duplexer according to a third embodiment.
FIG. 3A shows a plane orthogonal to the length direction of the inner conductor.
FIG. 4B is a sectional view of a main part showing a cut section, and FIG.
Main section showing a section cut along a plane along the length of the body
FIG. The multi-frequency demultiplexer of the present embodiment is
In the multifrequency duplexer according to mode 2, the terminal (T_1.5) And terminal
(T_Two) Are integrated. That
For this reason, in this embodiment, as shown in FIG.
_{1.5 / 2}), The coupling line 2 inside the BPF 120
Line length of 6 (l₂₆) Is 38 (≒ λ_2.0/ 4) mm,
The line length of the coupled line 27 inside the BPF 130 (l₂₇)
Is 50 (≒ λ _1.5/ 4) mm. Real truth
In the present embodiment, the same operation and effect as in the first embodiment are described.
The effect can be obtained. As described above,
The invention made will be specifically described based on the above embodiment.
However, the present invention is limited to the above-described embodiment.
And various changes are possible without departing from the gist
Of course, it is capable.

[0023]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows. ADVANTAGE OF THE INVENTION According to the multifrequency splitter of this invention, it becomes possible to attain miniaturization and to reduce loss compared with the prior art, without lowering an electrical characteristic.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of an example of a multi-frequency splitter according to a first embodiment of the present invention.

FIG. 2 is a graph showing an example of an attenuation characteristic of each band pass filter shown in FIG.

FIG. 3 is a diagram for explaining a line length of a coupling line of each band-pass filter shown in FIG. 1 and a line length of a transmission line.

FIG. 4 is a diagram illustrating a schematic configuration of another example of the multifrequency duplexer according to the first embodiment of the present invention.

5 is a graph showing an example of an attenuation characteristic of each band pass filter shown in FIG.

6 is a diagram for explaining a line length of a coupling line of each band-pass filter shown in FIG. 4 and a line length of a transmission line.

FIG. 7 is a sectional view of a main part showing a schematic structure of an interdigital band-pass filter.

FIG. 8 is a circuit diagram showing an equalizing circuit of an interdigital band-pass filter.

FIG. 9 is a diagram for explaining an inter-stage coupling coefficient (M _{k, k + 1} ) of an interdigital band-pass filter.

FIG. 10 is a sectional view of a main part showing a schematic structure of a comb line type band pass filter.

FIG. 11 is a circuit diagram showing an equalizing circuit of a comb-line type band-pass filter.

FIG. 12 is a diagram for explaining an inter-stage coupling coefficient (M _{k, k + 1} ) of a comb-line type band-pass filter.

FIG. 13 is a diagram illustrating an example of an attenuation characteristic of a band-pass filter having a passband having a Chibishev type characteristic and an attenuation region having a Wagner type characteristic.

FIG. 14 is a fragmentary cross-sectional view showing a configuration of a multifrequency duplexer according to Embodiment 2 of the present invention.

FIG. 15 is a cross-sectional view of a principal part showing a configuration of a multifrequency duplexer according to a third embodiment of the present invention.

16 is a diagram for explaining a line length of a coupling line of each band-pass filter shown in FIG. 15 and a line length of a transmission line.

FIG. 17 is a diagram for explaining a schematic configuration of a conventional multi-frequency demultiplexer.

FIG. 18 is a diagram for explaining a multi-frequency demultiplexer prototyped by the inventor of the present application before filing the application of the present application.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Resonant rod, 2 ... Housing, 3, 20-23, 25, 26,
27, 29: coupling line (coupling loop), 4: input connector, 5, 10 ₁ to 10 ₄ , 11 _{1 to} 11 ₄ , 12 _{1 to} 12 ₄ ,
13 _{1 to} 13 ₄ ... internal conductor, 7 ... partition wall, 24 ... transmission line,
31 to 35: resonance frequency adjusting screws, 100, 110,
120, 130, 210p, 220p, 230p, 31
0, 320, 330... Band-pass filter, 220 e, 2
30e ... band rejection filter.

Claims (3)

[Claims] An m (m ≧ 2) band-pass filter having a coupling line connected to a common terminal therein, and a connection point between the common terminal and a coupling line of the m band-pass filters. A transmission line to which one end is connected, and n (n ≧ 2) band-pass filters each having therein a coupling line connected to the other end of the transmission line; Each band-pass filter is a multi-frequency demultiplexer that passes a high-frequency signal higher in frequency than each of the m band-pass filters, and sets a line length of a coupling line in each of the m band-pass filters. In each of the high-frequency signals passing through each of the n band-pass filters, the length from one end of the transmission line to the short-circuited end of the coupling line is set to be substantially infinite, and The line length of the transmission line In each of the high-frequency signals passing through each of the m bandpass filters, one end of the transmission line is connected to the end of the shortest coupling line among the coupling lines in each of the n bandpass filters. A multi-frequency duplexer characterized in that the impedance up to the short-circuit end is set to a length that is almost infinite. 2. A first band-pass filter having therein a coupling line connected to a common terminal and passing a first high-frequency signal having a wavelength of λ _L , the common terminal and the first band. A transmission line having one end connected to a connection point of the pass filter with the coupling line, and a coupling line internally connected to the other end of the transmission line, and having a frequency lower than the first frequency. High frequency, wavelength λ _HL
A second band-pass filter that passes a high-frequency signal having a second frequency, and a coupling line connected to the other end of the transmission line, and a frequency higher than the second frequency, Wavelength is λ _HH
And a third band-pass filter that passes a high-frequency signal of a third frequency, wherein the first band-pass filter has an internal coupling line having a line length of (λ _HL + Λ _HH ) / 8, wherein the second band-pass filter has a line length of an internal coupling line (λ _HH / 4), and the third band-pass filter has a line length of an internal coupling line. Is (λ _HL / 4), and the transmission line has a line length of (λ _LL / 4) − (λ _HH / 4).
A multi-frequency demultiplexer characterized in that: 3. A first band-pass filter having a coupling line internally connected to a common terminal and passing a first high-frequency signal having a wavelength of λ _LL , and a coupling internally connected to a common terminal. Having a line, the first
A second band-pass filter for passing a second high-frequency signal having a wavelength of λ _LH at a frequency higher than the frequency of the first band-pass filter and the first and second band-pass filters. At a connection point with the coupling line, a transmission line having one end connected thereto, and a coupling line internally connected to the other end of the transmission line, having a frequency higher than the second frequency, Wavelength is _λHL
A third band-pass filter that passes a high-frequency signal having a third frequency, and a coupling line connected to the other end of the transmission line, and a higher frequency than the third frequency; Wavelength is λ _HH
And a fourth band-pass filter that passes a high-frequency signal having a fourth frequency, wherein the first and second band-pass filters have a line length of an internal coupling line. (Λ _HL + λ _HH ) / 8, wherein the third band-pass filter has a line length of an internal coupling line (λ _HH / 4), and the fourth band-pass filter has an internal coupling line _Has a line length of (λ _HL / 4), and the transmission line has a line length of (λ _LL / 4) − (λ _HH / 4).
A multi-frequency demultiplexer characterized in that: