JPS6232702A - Band-stop filter - Google Patents

Abstract

PURPOSE:To constitute a simple and small-sized band stop filter for two frequency bands by arranging an internal conductor constituting a coaxial resonator having a resonance frequency band different from that of a rectangular waveguide resonator in the square waveguide resonator. CONSTITUTION:The rectangular waveguide resonator 1 is coupled with a coaxial line 7 through a probe 3 to constitute a filter for stopping a resonance frequency band. On the other hand, the coaxial resonator having the resonance frequency band different from that of the resonator 1 is formed by using the resonator 1 as an external conductor and arranging the internal conductor on the inside of the external conductor to constitute the other band stop filter. Since the filters for stopping two frequency bands re stored in the common external conductor and coupled with the coaxial line 7 through one probe 3, the number of constitutional parts can be reduced and an inexpensive, simple and small-sized product can be obtained. When a constant input impedance diplexer is constituted together with a hybrid circuit, the whole diplexer can be simplified and reduced at its size.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to a television broadcasting device or a general communication device in which unnecessary waves are removed, two signal waves are combined, or unnecessary waves are removed and two signal waves are combined. The present invention relates to a band-elimination filter suitable for the configuration of a constant input impedance diplexer, etc. used when synthesizing.

2. Description of the Related Art For example, in a color television broadcasting device, in order to synthesize an audio signal carrier wave fA and a video signal carrier wave fυ, a (1) bandpass filter as shown in FIG. 14 has conventionally been used. ing.

In Fig. 14, 15 is a rectangular waveguide resonator, 16 is a capacitive coupling probe, 17 is a λg/4, and 11 resonator (λ
g is the pipe wavelength), 18 is a capacitive coupling probe, and 19 is a transmission line. When a band-stop waveform with this configuration is combined with a hybrid circuit to form a constant input impedance diplexer, a rectangular conductor with a high load Q The audio signal carrier f8 is reflected by the wave tube resonator 15, and the color bee is reflected by the medium load Q λg/4 coaxial resonator 17.
fυ-fs (fs is a color subcarrier) is removed, and the B'2 voice transmission wave-1 history transmission wave f^ and the video signal carrier wave ``υ'' are combined and extracted from the output terminal of the hybrid circuit.

Problems to be Solved by the Invention The conventional band-elimination filter shown in FIG. Not only does the structure become large due to the need for cascading connections, but it also has a large number of component parts.
The cost cannot be avoided.

It is an object of the present invention to eliminate such conventional drawbacks and realize a filter for band I that is simple in structure, small in size, and inexpensive.

1st Embodiment for Solving Problems FIG. 1 is a sectional view (BB sectional view in FIG. 2) showing an embodiment of the present invention.
Fig. 2 is a cross-sectional view taken along the line A-A in Fig. 1, and Fig. 3 is a cross-sectional view taken along the line CC in Fig. 2. In each figure, 1 has an axial length of approximately λg/
2. A common outer conductor consisting of a rectangular hexahedron with a width a and a height b,
Reference numeral 2 denotes an internal conductor, which is provided in the internal space of the common external conductor 1 so that its axial direction is perpendicular to the electric field (ER) direction of the common external conductor 1, and its lower end is formed as a short-circuited end and its upper end is formed as an open end. It is. Ideally, it is desirable to position the lower end of the internal conductor 2 at the center of a square part that includes one of the short sides of the side wall of the common external conductor l, but it is also possible to place the lower end of the internal conductor 2 at an arbitrary location. The invention can be put into practice. 3 is yong! is a coupling probe that couples the external circuit to the λg/4 coaxial resonator formed by the common external conductor l and the internal conductor 2 via the distributed capacitance between the common external conductor l and the internal conductor 2. The rectangular waveguide resonator formed by the common external conductor 1 and the external circuit are coupled through the distributed capacitance between the common external conductor 1 and the external circuit. 4 is an insulator interposed between the periphery of the hole bored in the common external conductor 1 and the capacitive coupling probe 3;
is a resonant frequency fine adjustment element for the TEI o-mode wave excited in a rectangular waveguide resonator, for example, a conductor screw that can change the insertion length into the tube, or a long and thin electrode plate attached to the inner end of the rotating shaft, It is made of any suitable element among conventionally known elements, such as an element formed so that the electrode plate can be rotated. Reference numeral 6 denotes a resonant frequency fine adjustment element for a TEM mode wave excited in the λg/4 coaxial resonator portion formed by the common outer conductor 1 and the inner conductor 2, and is composed of an element having the same configuration as element 5. 7 is a coaxial line, and the outer end of the common capacitive coupling probe 3 is inserted into the line through a hole bored in the outer conductor 8 and connected to the inner conductor 9 of the coaxial line 7, and the external circuit is connected via this coaxial line. , for example, to a hybrid circuit or circulator.

Note that instead of the coaxial line 7, for example, a high frequency transmission line such as a coaxial cable or a striped spline may be used.

1 to 3 show a case in which a common capacitive coupling probe 3 is used as a coupling element with an external circuit to perform capacitive coupling with a rectangular waveguide resonator and a λg/4 coaxial resonator. Although illustrated, instead of the capacitive element, a magnetic coupling loop 10 with a length of approximately λg/4, as shown in the main part in FIG.
TE in a waveguide resonator with a rectangular loop surface,
If it is placed perpendicular to the magnetic field of the Q mode wave, it will be magnetically coupled to the rectangular waveguide resonator, without intersecting with the magnetic field component of the TEM mode wave excited in the λg/4 coaxial resonator. , λg/4 coaxial resonator side through distributed capacitance.

Furthermore, if the loop surface of the magnetic coupling loop lO is provided to form an angle of 45'' with the magnetic field direction of the TEI O mode wave in the rectangular waveguide resonator, the TEI O mode wave in the rectangular waveguide resonator In the magnetic field of the TEM mode wave in the λg/4 coaxial resonator, it intersects with the component perpendicular to the loop plane, and in the magnetic field of the TEM mode wave in the λg/4 coaxial resonator, it intersects with the component perpendicular to the loop plane, so magnetic coupling with both resonators is established. can be made to do so.

If the loop surface of the magnetic coupling loop 10 is provided at an arbitrary angle other than 450 degrees with respect to the magnetic field of the TEI O mode wave in the rectangular waveguide resonator, either one of the resonances will resonate depending on the installation angle. It is possible to achieve tight coupling with the resonator and loose coupling with the other resonator.

In addition, as shown in the main part in FIG. 5, coupling with the rectangular waveguide resonator was performed using the same capacitive coupling probe 3 as shown in FIGS. 1 to 3, and the λg/4 coaxial resonator and The combination of
The magnetic coupling loop 11 having a length of approximately λg/4 may be used, and as shown in FIGS. 6 and 7, a rectangular waveguide resonator and a λg/4 coaxial resonance A magnetic coupling loop 12 with a length of approximately λg/4 connects each coupling with the device.
and 13 may be configured to be performed separately.

Figure 5-? Of course, in FIG. 57, the degree of coupling can be changed by changing the distributed capacitance between the coupling element and the common external conductor and the area of intersection with the magnetic field of the magnetic coupling loop.

Note that FIG. 4 is a sectional view corresponding to FIG. 1.

tjS5 and FIG. 7 are sectional views corresponding to FIG. 3, and FIG. 6 is a sectional view corresponding to FIG. 2. or,
Reference numeral 14 in FIGS. 5 and 7 is a coaxial line, and other symbols in FIGS. 4 to 7 are the same as in FIGS. 1 to 3.

The no-load Q (QUR) on the rectangular waveguide resonator side constituting the band-elimination filter of the present invention can be determined by the following equation when the resonator is formed of copper.

Further, the no-load Q (Quc) on the λg/4 coaxial resonator side is determined by the following equation when the resonator is formed of copper.

Quc';42ff b 77...
...(2) In equations (1) and (2), the units of the width a and height b of the common external conductor 1 are Cff1, and the units of the transmission frequency f are GH2 in the case of equation (1), (2) In the case of formula MH
2, η is the efficiency.

To give a specific numerical example, for example, the transmission frequency f is f(O
OMH2, the width a of the common external conductor l is 35 cm, the height b is 10 cm, and the ratio f/fc of the cutoff frequency f and fC is 1.
In the case of 4, Quc': 42 H positive XIO no 10300.

Further, the video signal carrier wave fv introduced into the guiplexer in the extremely short wave band television broadcasting device is, for example, 5
97.25 MHz, color subcarrier fS is Goo, 8
3 MHl, audio signal carrier f^ is 601.75882
, Color Bee) 2fv-fs is 593.87 MHz
In case (7), if the load Q on the rectangular waveguide resonator side in the audio signal carrier wave FA is set to 1000, the resistance molecule on the rectangular waveguide resonator side becomes as follows.

Further, when the load Q on the λg/4 coaxial resonator side in color beat 2fυ-fs is set to 600, the resistance molecule 3 on the λg/4 coaxial resonator side is as follows.

FIG. 8 is a block diagram showing the band-elimination filter of the present invention,
NF is the first band-stop filter portion having an attenuation pole at frequency f1, and is the common outer conductor 1 in FIGS. 1 to 3.
The part corresponding to the rectangular waveguide resonator formed by N
F2 is a second band-stop waver section having an attenuation pole at frequency f2, and is a common outer conductor 1 in FIGS. 1 to 3.
and a portion corresponding to the λg/4 coaxial resonator formed by the inner conductor 2, T is a coupling terminal with an external circuit.

FIG. 9 is an equivalent circuit diagram of the band-elimination filter of the present invention, and R1
is a resonant circuit formed by a rectangular waveguide resonator formed by the common external conductor l in FIGS. 1 to 3,
C1 is the capacitance, Ll is the inductance, rl is the resistance, R2 is the resonant circuit formed by the common outer conductor l and the inner conductor 2, C2 is the capacitance, L2 is the inductance, and 2 is the resistance. It is.

The composite admittance 9 of the admittance Y1 of the resonant circuit R1, the admittance Y2 of the resonant circuit R2, and the admittance Y1.92 is calculated by the following equation.

Y+= 1/ (r++j(ωL1-ωC1))=1
/(r+ +jx+) ...(3)Y
2: l/'(r2+j(ωL2-ωc2))=
1 / (r2+ jx2) ・ ・ ・
・ (4) v=y1+y2 ・
・ ・ ・ (5) However, ω: Angular frequency 2Q and 1°. l -QLI ”” (6)QL 2 °. 2-0.10 -°- (7) QLI: Load Q of resonant circuit R1 Q[2: Load Q of resonant circuit R2 Qu+: No load Q of resonant circuit R1 QU2: No load Q of resonant circuit R2 f: Arbitrary Transmission frequency BW3 3dB attenuation frequency bandwidth BV1 of resonant circuit R1
32: 3 dB attenuation frequency bandwidth of resonant circuit R2 The equivalent circuit diagram shown in FIG. 9 can be shown from equation (5) using the block diagram in FIG.
O) is expressed by the formula.

The transmission characteristic between the two terminal pairs in Figure 10 is obtained from the equation (lO) using the equation (11), and in the case of decibel display, it is
2) It is determined by the formula.

When any one terminal pair in FIG. 10 is terminated with the load impedance 21, the human power impedance ZIN seen from the other terminal pair side is determined by the following equation.

If the load impedance is 1, then the input admittance YIN is YIN=1+Y
...(15).

If the characteristic admittance of the circuit shown in FIG. ) can be obtained using the formula.

FIG. 11 is a block diagram of a diplexer configured by combining two band-elimination filters of the present invention with two hybrid circuits. vessel, HYB+ and 1
(YB2 is)\Ibrid circuit, TO and T1 are input terminals, T'2 is output terminal, T3 is isolation terminal,
T1, T2, Th and T1 are coupling terminals, and RT is a non-reflection terminator.

Figure 12 shows the /\ibrid circuit HY in Figure 11.
12 is a block diagram showing a portion of B+, and the reference numerals are the same as in FIG. 11.

In Fig. 12, the input voltage of the input terminal TO is EIN, the voltages of the coupling terminals TI and T2 are 1 and 2, the voltage of the isolation terminal T3 is E3 (=O), and the coupling coefficient of the hybrid circuit HYB+ When the electrical angle of C1 is set to 0, there are relationships between the voltages at each terminal as shown in the following equations.

From this voltage relationship, Figure 12 (Scano 1)
The ringing matrix is given by the following equation.

・ ・ ・ ・ (18) However, formula (18) is based on the assumption that the input reflection coefficient at each terminal is zero when all terminals other than the measurement terminal among the four terminals in Fig. 12 are non-reflection terminated. It is.

The above relationship holds true in exactly the same way for the hybrid circuit HYB2 in the fIS11 diagram.

From the above relationship, the hybrid circuit HY in Figure 11
When a voltage of 1υIN is applied to the terminal To of B+, the voltages output to each terminal To to T3 are Eoo and EO, respectively.
I, EO2 and EO3, these voltages are (
19) can be obtained using equation 19).

That is, the voltages EOI and EO2 of the terminals T1 and T2 are determined by a linear equation.

The voltages EOI and [02 of terminals T1 and T2 in the above equation
From the voltage reflection coefficient rIN of equation (17), the reflected voltages EVIN'l and Ev+sr2 at terminals T1 and T2 are determined by equations (22) and (23), respectively.

From equations (18), (22), and (23), the output voltages E'oo to total Eo,+ due to the reflected waves of the terminals TO to T3 of the circuit HYB+ in FIG. 11 can be determined by the following equations.

・ ・ ・ ・ (24) Therefore, the reflected wave output voltage of terminals To and T3 is oo
r and 6Q3r are determined by equations (25) and (26).

In formulas (25) and (26), C position 17f'i,
When θ is π/2, the reflected wave output voltage is generally −iυIN (where r='t/(2+9)).

When C job 1/ff and 0 job π/2, c2
=o, 5 and 5in2θ=1, so (25)
The formula is Eoor=0 −− ・−(25')
Then, the equation (26) becomes as follows.

The voltage transfer function TV of the band-elimination filters NF121 and NF122 of the present invention in FIG. 11 is calculated from equation (11) as (
27) can be obtained as Eq. In addition, when determining in decibel value, formula (12) is used.

Therefore, the voltages EOI and EO2 appearing at terminals TI and T2 in FIG.
When reaching the terminals T'o and T'3 of the hybrid circuit HYB2 via F121 and NF122, the terminal rc
and the input voltage ρ′o of T′3 and E′3 are (,20)
Equations, (21) and (27) to (28) and (2
9) Therefore, the output voltage of the terminals T'l and T' of the hybrid circuit HYB2 in FIG. 11 is (
It is determined by equation (30) from equation (18), equation (28), and equation (29).

・ ・ ・ ・ (30) That is, terminals TI and T'! The output voltage iL1 and i6
'2 is as shown in equations (31) and (32).

General conditions in high printed circuits, i.e. c=1
Substituting /f''i, o=π/2 into equation (31) yields 1 0, which means that the amount of attenuation between terminal To and terminal T'1 is infinite in principle. It shows.

However, the circuit configurations of the hybrid circuits HYBI and HYB2 are strictly asymmetric, and the band-stop filter WNF
12 + and NFI2' cannot be made completely the same, so in reality, the g is about 40 dB.

Also, by substituting the general conditions for hybrid circuits, c=17f'''i, and e π/2 into equation (32), we get (3
Equation 2) is as follows, which matches the voltage transmission characteristics of a general band-stop wave device.

Next, the power attenuation characteristic between terminals To and T'2 can be obtained using equation (33), and when expressed in decibel values, (1
2) Calculate using the formula.

(33) Substituting the following conditions: C no 1/month, 0 jobs π/2, we get (3
Equation 3) becomes Equation (34).

Since the circuit in FIG. 11 is a symmetrical circuit, its transmission characteristics are also symmetrical, and when input voltage EAIN is applied to terminal T'1, (
By replacing EIIIN in equation 26) with EAIN, the reflected wave output voltage E' at terminal T'2 can be obtained from equation (35).
02r can be found.

From equation (35), the power transfer characteristic between terminals T' and -72' can be obtained using equation (36), and when displaying the transmission characteristic Ll'-2'' in decibel values, it can be obtained using equation (37). I can do it.

(37) As is clear from the above explanation, the required voltages applied to the terminals To and T'1 are combined and outputted to the terminal T; and unnecessary waves are transmitted to the non-reflection terminator connected to the terminal T3. The human power impedance of the diplexer shown in FIG. 11 is always kept constant without any reflected wave being absorbed by RT and appearing at the terminal To.

Next, the transmission characteristics when the diplexer shown in FIG. 11 is used for combining the video signal carrier wave fv and the audio signal carrier wave fA in a very short wave band color television broadcasting apparatus will be explained using specific numerical values.

The size of the resonator constituting the band-elimination filter of the present invention, that is, the height b (cm) of the common outer conductor 1 and the resonant frequency f (
From MH7, ), the no-load Q (Qu) of the resonator can be found using equation (3).

qu=42. ffb... (
38) In the above formula, for example, f = Ei00MH7,
If b=10 cm, then Qu'=10200.

Video signal carrier fυ is 597.25MH2, color subcarrier fs is Eioo, 83MH1, audio signal carrier FA
If 601.75MHz, color beat 2
Since fv-rs is 593.87MH7, the load Q (QLA) of the resonator in the audio signal carrier fA is set to 100.
0, and when the load Q (QLS) of the resonator at color beat is 800, the equivalent resistance r of the resonator at the audio signal carrier b+ is equal to the equivalent resistance rs of the resonator at the color subcarrier f5, which is the audio signal carrier fA. To the capacitive reactance X of the resonator at the color subcarrier fs, the capacitive reactance B of the resonator at the color subcarrier fs is expressed as follows. [(
If OMH2 is selected, the admittance t of the resonator is r + j2 -7' becomes.

Above, we have shown some of the results obtained by manually calculating the transmission characteristics, but the dimensions and transmission frequency of each component in the band-elimination filter of the present invention are appropriately selected, and the theoretical calculation values obtained by a computer and the prototype The results are in extremely good agreement with the actual values measured by the machine.

The above has explained the case where the rectangular waveguide resonator and the λg/4 coaxial resonator are excited by two waves with different modes, but only one of the resonators may be excited by a single wave. In this case as well, as shown in FIGS. 1 to 7, it is possible to excite by connecting the intermediate portions of the transmission lines 7 and 14 via a coupling element, but the end portions of the transmission lines 7 and 14 Of course, a coupling element may be connected to the .

Effects of the Invention As is clear from the above explanation, the band-elimination filter of the present invention has a rectangular waveguide resonator and a λg/4 coaxial resonator inside the outer conductor forming the rectangular waveguide resonator. By coexisting with the λg/4 coaxial resonator, there is no need for an external conductor for the λg/4 coaxial resonator.
Since there is no need for a transmission line for cascading the /4 coaxial resonator, the number of components as a whole is small, the cost can be reduced to paper storage, and the configuration can be made simple and compact. Furthermore, as shown by curve A in FIG. 13, which shows an example of the characteristics of the prototype, the transmission characteristics are also good, and when a constant input impedance diplexer is constructed using the band-stop filter of the present invention, the entire diplexer is The transmission characteristics between terminals 'ro and T'2 in FIG. 11 are exactly the same as the A curve in FIG. The transmission characteristics are extremely good, as shown by curve 8 in FIG.

In addition, in FIG. 13, the horizontal axis is the transmission frequency f (MHl
), and the vertical axis is the transmission loss L (dB).

[Brief explanation of the drawing]

1 to 3 are diagrams showing one embodiment of the present invention, and FIG.
7 to 7 are diagrams showing main parts of other embodiments of the present invention,
Figures 8 and 10 are diagrams for explaining the operation;
The figure is an equivalent circuit diagram thereof, Figure t511 is a diagram showing a constant input impedance diplexer constructed using the band-elimination filter of the present invention, and Figure 12 is a diagram for explaining its operation.
FIG. 13 is a diagram showing an example of the transmission characteristics of the band-elimination filter of the present invention, and FIG. 14 is a diagram showing a conventional band-elimination filter, where l: common outer conductor, 2: inner conductor, 3 .1B and 18
: Capacitive coupling probe, 4: Insulator, 5 and 6: Resonant frequency fine adjustment element, 7.14 and 19: Transmission line, 8:
Outer conductor of the line, 9: Inner conductor of the line, 10 to 13:
Magnetic coupling loop, 15: rectangular waveguide resonator, 17: coaxial resonator, NFl, NF2, NFI21 and NF
122: Band-stop filter, T, To to T3 and T
'o to T1: terminals, )IYB, and IYB2: hybrid circuit.

Claims (5)

[Claims] (1) Within a common outer conductor forming a rectangular waveguide resonator,
An internal conductor having an axial length of approximately λg/4 (λg is the tube wavelength) is provided such that the axial direction thereof is perpendicular to the electric field direction of the TE_1_0 mode wave excited in the rectangular waveguide resonator. A band-elimination filter characterized in that it forms a λg/4 coaxial resonator together with an external conductor, and further comprises a coupling element for coupling each of the resonators to an external circuit. (2) The band-stop filter according to claim 1, wherein the coupling element comprises a capacitive coupling probe common to the rectangular waveguide resonator and the λg/4 coaxial resonator. (3) The band-stop filter according to claim 1, wherein the coupling element comprises a magnetic coupling loop common to the rectangular waveguide resonator and the λg/4 coaxial resonator. (4) The band-stop filter according to claim 1, wherein the coupling element comprises a capacitive coupling probe coupled to a rectangular waveguide resonator and a magnetic coupling loop coupled to a λg/4 coaxial resonator. . (5) Claim 1, wherein the coupling element comprises a first magnetic coupling loop coupled to the rectangular waveguide resonator and a second magnetic coupling loop coupled to the λg/4 coaxial resonator. Bandstop filter.