JPH053922B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a constant impedance diplexer (hereinafter abbreviated as CIN diplexer) used for combining a video signal carrier wave and an audio signal carrier wave in, for example, a television broadcasting device. The present invention relates to a notch filter that is suitable as a component such as the above.

BACKGROUND ART FIG. 15 is a diagram showing an example of a CIN diplexer conventionally used to synthesize a video signal carrier wave and an audio signal carrier wave in a television broadcasting device, and 12 ₁ and 12 ₂ are hybrid circuits; 16 ₁ and 16 ₂ are resonators that resonate at the color beat frequency, that is, f _V −3.58 (MHz) (f _V is the frequency of the video signal carrier wave), and 17 ₁ and 17 ₂ are resonators that resonate at the audio signal carrier wave f _A (MHz). The resonator resonates, and the video signal carrier f _V and the video signal carrier f _V − generated in the video signal transmitter are connected to the input terminal 12 ₁₁ of the hybrid circuit 12 ₁ .
When a color beat of 3.58 is added, the non-reflection terminator 14 connected to the isolation terminal 12 ₁₂
The color beat f _V −3.58 is absorbed. When the audio signal carrier f _A is applied to the input terminal 12 ₂₁ of the hybrid circuit 12 ₂ , the isolation terminal 12
₂₂ , a video signal carrier wave _fV and an audio signal carrier wave _fA are sent out. And resonators 16 ₁ , 16 ₂ , 17 ₁ and 1 in the CIN diplexer shown in FIG.
_For example, a semi-coaxial cavity resonator whose cross section is shown in FIG. 16 or a rectangular waveguide cavity resonator whose cross section is shown in FIG. cavity resonators are required, and the number of connectors between the resonators is also relatively large, resulting in
The disadvantage is that the overall structure is complicated and large, and the cost is high.

The present inventor previously proposed a notch filter consisting of a dual-mode circular waveguide cavity resonator that is suitable as a component of a CIN diplexer and can eliminate the drawbacks of the CIN diplexer shown in FIG. −019121). Fig. 18 is a cross-sectional view showing its configuration, and Fig. 19 is a cross-sectional view taken along line A-A in Fig. 18. In both figures, 18 is a circular waveguide cavity resonator, and 19 is a hole in the short-circuit wall. A coupling hole, 20 a coupling line, and 21 a main line, which together with the coupling line 20 form a T-branch circuit. Coaxial terminals 22 and 23 connect each internal conductor to the end of the main line 21. Figure 20 shows a CIN using the above notch filter.
In the diagram showing the diplexer, 24 ₁ and 24 ₂ are the first
8 and 19, the coaxial terminal 22 of the notch filter 24 ₁ is connected to the coupling terminal 12 ₁₃ of the hybrid circuit 12 1, and the coaxial terminal 23 of the notch filter 24 ₁ is connected to the coupling terminal 12 13 of the hybrid circuit 12 1.
are connected to the coupling terminals 12 ₂₃ of the hybrid circuit 12 ₂ , respectively, and the coaxial terminals 22 and 23 of the notch filter 24 ₂ are respectively connected to the coupling terminal 12 ₁₄ of the hybrid circuit 12 ₁ and the coupling terminal 12 ₂₄ of the hybrid circuit 12 ₂ . .

When f _V waves and f _V -3.58 waves are applied to the input terminal 12 ₁₁ of the hybrid circuit 12 ₁ , the notch filter 24 ₁
Due to the magnetic coupling between each coupled line 20 and the coupling hole 19 of 24 _{and 2} , an electric field _{E 〓}
It has an angular difference of 45° and is perpendicular to the electric field E〓 _V , f _V −
The electric field E = _V-3.58 corresponding to the 3.58 wave coexists and resonates in the cavity resonator, and the f _V -3.58 wave is generated by the notch filter 2.
4 ₁ and 24 ₂ and absorbed by the non-reflection terminator 14 connected to the isolation terminal 12 ₁₂ , the _fV wave appears at the isolation terminal 12 ₂₂ of the hybrid circuit 12 ₂ . Further, the f _A wave applied to the input terminal 12 ₂₁ of the hybrid circuit 12 ₂ is reflected by the notch filters 24 ₁ and 24 ₂ and appears at the isolation terminal 12 ₂₂ , where it is combined with the f _V wave.

In this CIN diplexer, since only two cavity resonators are required, the overall structure can be made simpler and smaller, and the load on each of the two waves of different frequencies that co-resonate in the cavity resonator. Although it has the advantage that Q is equal to each other, the structure of the coupling part in the cavity resonator is complicated, and there are relatively many parts that require adjustment such as coupling holes and coupling lines, so it is relatively difficult to manufacture a notch filter. However, it cannot avoid the disadvantage of high cost.

Problems to be Solved by the Present Invention The present invention solves the above-mentioned drawbacks of the conventional art, that is, when constructing a diplexer etc., generally a relatively large number of notch filters are required, and even in a notch filter constructed so that a relatively small number is sufficient. The purpose of this invention is to eliminate the drawbacks of high cost due to the complicated structure and difficulty in manufacturing, and to realize a notch filter that is simple and easy to adjust in structure and manufacturing, reduces costs, and is suitable as a component of a diplexer, etc. do.

Means for Solving the Problems (Embodiment 1) FIG. 1 is a sectional view showing one embodiment of the present invention, FIG. 2 is a sectional view taken along line A-A in FIG. 1, and FIG. 1
In each figure, 1 is a cylindrical side wall of a circular waveguide cavity, whose axial length, that is, the resonance length, is approximately 1/2 of the tube wavelength λg. be. 2 is a short circuit wall, and 3 is a coupling probe, which is made of a rod-shaped conductor inserted into the tube from the cylindrical side wall 1, and its insertion direction into the tube is made to substantially coincide with the radial direction of the cylindrical side wall 1. 4 is a coaxial terminal, and 5 is an H-mode resonant frequency fine adjustment element, which is made of a rod-shaped conductor inserted into the tube from the cylindrical side wall 1, and can minutely change the insertion length into the tube, and whose insertion direction into the tube can be adjusted depending on the connection. Probe 3 and 45° and 135° (or almost 45°
and approximately 135°). 6 is a V mode resonant frequency fine adjustment element;
It has the same configuration as element 5 except that its insertion direction into the tube is formed at right angles (or approximately at right angles) to element 5. Reference numeral 7 denotes a mode coupling fine adjustment element, which has the same configuration as elements 5 and 6, except that its insertion direction into the tube has an angular difference of 45° (or approximately 45°) from that of elements 5 and 6, respectively. . Note that the adjustment effect can be maximized when the elements 5 to 7 are provided at approximately 1/2 of the axial length of the cylindrical side wall 1;
It may be provided at a location appropriately separated from the above location in the axial direction. Further, although the figure shows an example in which two elements 5 are provided at side wall locations symmetrical about the central axis, one of them may be omitted, and one of the elements 6 may be similarly omitted. Furthermore, instead of providing four elements 7 as shown in the figure, among the four elements,
The directions of insertion into the pipe are perpendicular to each other and 45° with elements 5 and 6.
Alternatively, a mode coupling fine adjustment element may be formed using two elements having an angular difference of 135°.

Functions and Effects When a circular waveguide cavity is excited by two waves with different frequencies through the coaxial terminal 4 and the coupling probe 3, the electric field E〓 _H and
The fact that the H mode and V mode, in which E = _V are orthogonal to each other, resonates at the same time.This is similar to the notch filter shown in FIGS. 18 and 19, but as is clear from FIGS. In addition, the connecting portion is made of a simple rod-shaped conductor, and has a much simpler structure and is easier to manufacture than the connecting portion in the notch filter shown in FIGS. It has the following characteristics.

In general, if the diameter of a circular waveguide cavity is D, the cutoff wavelength λ _c of the H ₁₁ mode is λ _c = 1.706D...(1) The internal wavelength λ _g is, if the free space wavelength is λ, λ (mm) = 300/f (GHz) In addition, the resonance length of a circular waveguide cavity is approximately 1/2 of the wavelength in the tube, and depending on the load Q (Q _L ), it is less than 1/2 of the wavelength in the tube. Changes to

Binding probe 3 in the Notti filter of the present invention
is provided at a location separated by λg/4 = _c from one of the shorting walls 2 in the central axis direction, one of the resonant frequency fine adjustment elements 5 and 6, for example 6, is omitted, and furthermore, a mode coupling fine adjustment element is provided. Adjustment element 7 is omitted, and the angular difference θ _H between element 5 and coupling probe 3 is set to 0° or 180°.
In other words, when the configuration is the same as that of a conventional circular waveguide cavity resonator, and the load Q is Q _LO , the diameter of the probe 3 is D _P and its insertion length in the pipe is
For _P , Q _LO increases proportionally to D _P ^-4 and increases proportionally to _P ^-2 . If θ _H is kept at 0° or 180° as described above and the load Q is Q _{L c} when _c is changed, then Q _{L c} = Q _LO /sin ² _c π/ …(3) Element 5 and 7 is omitted, element 6 and coupling probe 3
The same holds true when the angular difference θ _V is 0° or 180°.

In the notch filter of the present invention, the distance _c between the coupling probe 3 and the shorting wall 2 is maintained at approximately λ _g /4, and the sum of the angular difference θ _H between the element 5 and the probe 3 and the angular difference θ _V between the element 6 and the probe 3, If the magnitudes of θ _H and θ _V are changed while holding θ _H + θ _V at 90°, the load Q in H mode becomes Q _L 〓 _H , and the load Q in V mode
When Q _L 〓 _V , each load Q can be obtained from the following formula.

Q _L 〓 _H = Q _LO /sin ² θ _H …(4) Q _L 〓 _V = Q _LO /sin ² θ _V …(5) While _c is arbitrarily changed, the sum of θ _H and θ _V is set to 90°. The load _Q in H mode when changing the magnitudes _of θ _H and _{θ V} while maintaining
If the load Q in the mode is Q _{L c} 〓 _V , each load Q is given by the following equation.

Q _{L c} θ _V = Q _LO /sin ² _c /π・sin ² θ _H …(6) Q _{L c} θ _V = Q _LO /sin ² _c /π・sin ² θ _V …(7) The notch filter of the present invention is As shown in the equivalent circuit in Fig. 4, it operates as an independent resonant circuit for H mode and V mode, and the admittance Y for H mode = the admittance Y for _H and V modes = _V is calculated by equation (8) and It can be obtained from equation (9).

Y〓 _H = [Q _{L c} θ _H (f/f _OH −f _OH /f)] ^-1 …(8) Y〓 _V = [Q _{L c} θ _V (f/f _OV −f _OV /f)] ^-1 ...(9) However, f: arbitrary frequency f _OH : resonant frequency in H mode f _OV : resonant frequency in V mode The basic matrix [F〓 _HV ] of the equivalent circuit shown in Figure 4 is [F〓 _HV ]=1 Y〓 _H 0 11 Y〓 _V 0 1=1 Y〓 _H +Y〓 _V 0 1=A〓 B〓 C〓 D〓 …(10) Equation (8), Equation (9) and (10) From the formula, the transmission characteristic L _HV is: L _HV = 10og | A〓 + B〓 + C〓 + D〓 | ² / 4 = 10og |
1+0+( _Y〓H + _Y〓V )+1｜ ² /4=10og｜1+ _Y〓H + _Y〓V /2｜ ² =20og｜1
+Y〓 _H +Y〓 _V /2｜…(11) The actual measured value obtained by the inventor for the prototype is (11)
It agrees extremely well with the theoretical value obtained from the formula, and its transmission characteristic curve is shown in Figure 5 (the horizontal axis is the frequency fMHz,
The vertical axis is as shown in the attenuation amount (ATTdB).

Means for Solving Problems (Embodiment 2) FIG. 6 is a diagram showing another embodiment of the present invention.
1 is a notch filter of the present invention shown in FIGS. 1 to 3; 9 is an inductive compensation circuit consisting of a short-circuited coaxial stub having an axial length of λg/4 or less; and a cruciform branch circuit 10 consisting of a coaxial line. It is connected to the coaxial terminal 4 via.

Actions and Effects FIG. 7 is its equivalent circuit diagram, where Y _L is the admittance of the compensation circuit 9. The basic matrix [F〓 _HVL ] of this equivalent circuit is [F〓 _HVL ]=1 Y〓 _H +Y〓 _V +Y〓 _L 0 1 …(12) The transmission characteristic is L _HVL = 20og｜1+Y〓 _H +Y〓 _V +Y〓 _L /2 | ...(13), and the transmission characteristic curve is as shown in Figure 8 (the horizontal and vertical axes are the same as Figure 5), and as is clear from the figure, the inductive By adding a compensation circuit, it is possible to form a notch filter suitable for cases where there is a relationship of f _V <f _A between the video signal carrier f _V and the audio signal carrier f _A , such as in the NTSC television system. That is, approximately f _V -3.58MHz to approximately f _V +4.18MHz (color subcarrier f _S = f _V +3.58M
Including Hz. ) can form a notch filter with good transmission characteristics and group delay time characteristics.

Means for solving the problem (Embodiment 3) FIG. 9 is also a diagram showing another embodiment of the present invention,
Reference numeral 11 denotes a capacitive compensation circuit, which is composed of, for example, an open coaxial stub with an axial length of λg/4 or less. Other codes are 6th
It is similar to the figure.

Actions and Effects Figure 10 shows its equivalent circuit, where Y〓 _C is the admittance of the capacitive compensation circuit. The basic matrix [F〓 _HVC ] of this equivalent circuit is [F〓 _HVC ]=1 Y〓 _H +Y〓 _V +Y〓 _C 0 1...(14), and the transmission characteristic is L _HVC = 20og｜1+Y〓 _H +Y 〓 _V + Y〓 _C /2 | …(15)

Figure 11 (horizontal and vertical axes are the same as Figure 5):
FIG. 9 is a curve diagram showing the transmission characteristics of the notch filter of the present invention. As is clear from the diagram, by adding a capacitive compensation circuit, it is suitable for television systems etc. which have a frequency relationship of f _V > f _A. A notch filter can be formed.

Figure 12 shows the transmission characteristics and frequency f of the notch filter of the present invention to which an inductive or capacitive compensation circuit is added.
This is a diagram explaining the relationship between the voltage reflection coefficient Γ〓(f) and the input power (frequency f) of the notch filter 8 as P _IN (f), the output power as P _OUT (f), and the frequency f as
The admittance of the resonant circuit and the compensation circuit at Y〓 _H (f), Y〓 _V (f), Y〓 _L (f) and Y〓 _C (f)
Then, if the compensation circuit is inductive, P _IN (f)/P _OUT (f) = 1/1 - |Γ ² 2 (f)
|=|1+Y〓 _H (f)+Y〓 _V (f)+Y〓 _L (f)/2|
² Therefore, 1/|1+Y _H (f)+Y _V (f)+Y _L (f)/2|
² =1-｜Γ〓 ² (f)｜｜Γ〓 ² (f)｜=1-1/｜1+Y _H (f)+Y _V
(f)+Y _L (f)/2｜ ² ｜Γ〓(f)｜=[1-1/｜1+Y _H (f)+Y _v
(f)+Y _L (f)/2 | ² ] ^1/2 …(16) The return loss L _r (f) at frequency f is L _r (f)=1/|Γ ² (f) |=1 /[1-1/|
1+Y _H (f)+Y _V (f)+Y _L (f)/2 | ² ]...(17) If the compensation circuit is capacitive, |Γ〓(f)|=[1-1/|1+Y _H ( f)+Y _V (
f)+Y _C (f)/2 | ² ] ^1/2 …(18) Lγ(f)=1/[1-1/|1+Y _H (f)+Y _V (
f)+Y _C (f)/2 | ² ]...(19) A diplexer can be constructed by combining the notch filter of the present invention with a hybrid circuit or a circulator, and FIG. 13 shows the notch filter of the present invention in a hybrid circuit. 8 ₁ and 8 ₂ are the notch filters of the present invention explained with reference to FIGS. 1 to 3, and 12 ₁ and 12 ₂ are hybrid circuits.
12 ₁₁ and 12 ₂₁ are input terminals, 12 ₁₂ and 12 ₂₂
are isolation terminals, 12 ₁₃ , 12 ₁₄ , 12
₂₃ and 12 ₂₄ are coupling terminals, 13 ₁ and 13 ₂ are T branch circuits, for example, made of coaxial lines, and each branch terminal is connected to the coupling terminal 1 of the hybrid circuits 12 ₁ and 12 ₂ .
2 ₁₃ , 12 ₂₃ and 12 ₁₄ , 12 ₂₄ as well as coaxial terminals 4 ₁ and 4 ₂ (4 in FIGS. 1 and 3) of notch filters 8 ₁ and 8 ₂ . 14 is a non-reflection terminator.

The coupling coefficient of the hybrid circuit 12 ₁ is C, the electrical angle of the coupled line is θ, the characteristic impedance is Z _O , the load impedance connected to the coupling terminals 12 ₁₃ and 12 ₁₄ is Z _L , and Z _L = Z _O = 1. In this case, when the input voltage E〓 _IN is applied to the input terminal 12 ₁₁ , the coupling terminals 12 ₁₃ , 12 ₁₄ and the isolation terminal 12 ₁₂
The respective output voltages E〓 ₁₃ , E〓 ₁₄ and E〓 ₁₂ are E〓 ₁₂ ≒0 …(22) Terminals 12 ₁₃ and 12 when a load with voltage reflection coefficient Γ is connected to coupling terminals 12 ₁₃ and 12 _14
14 and 12 ₁₂ each output voltage E〓′ ₁₃ , E〓′ ₁₄ and E〓′ _1
2 is The reflected voltage E〓 ₁₁ 〓 to the input terminal 12 ₁₁ and the voltage reflection coefficient S _IN at the input terminal 12 ₁₁ are: S _IN = | E _IN | + | E ₁₁ 〓 | / | E _IN | − | E ₁₁ 〓 |…(27
).

14 is a diagram showing a diplexer constructed by combining the notch filter of the present invention shown in FIG. 7 with a hybrid circuit, where 8' ₁ and 8' ₂ are the notch filters of the present invention shown in FIG. 7, 15 ₁ and 15 ₂ is a cross-shaped branch circuit, and the other symbols are the same as in FIG.

Input terminal 12 in hybrid circuit 12 ₁
The input voltage and power with frequency f of ₁₁ is E〓 _11N (f)
and P _11N f), the input voltage and input power of the input terminal 12 ₂₁ in the hybrid circuit 12 ₂ are E〓 _21N (f)
and P _21N (f), the output voltage and output power of the isolation terminal 12 ₂₂ in the hybrid circuit 12 ₂ are E〓 _1OUT (f), E〓 _2OUT (f) and P _1OUT (f).
,
When P _2OUT (f), the voltage transmission characteristics and power transmission characteristics between the input terminal 12 ₁₁ of the hybrid circuit 12 ₁ and the isolation terminal 12 ₂₂ of the hybrid circuit 12 ₂ are as follows. P _11N (f)/P _1OUT (f)=20ogE _11N (f)/E _1OUT
(f) (dB) ...(29) Input terminal 12 ₂₁ of hybrid circuit 12 ₂ and isolation terminal ₁ of hybrid circuit 12 1
The voltage transmission characteristics and power transmission characteristics between 2 and ₁₂ are: P _2IN (f) / P _2OUT (f) = 20ogE _2IN (f) / E _2OUT
(f) (dB) ...(31) In equations (28) and (30), θ: electrical angle of the coupled line of the hybrid circuit at frequency f Input terminals 12 ₁₁ , 12 ₂₁ in the hybrid circuits 12 ₁ and 12 ₂ , Isolation terminal 12
₁₂ and 12 ₂₂ as E〓〓(f), and the input voltage of each terminal as _E〓K (f), the reflected voltage ratio at each terminal can be determined by the following formula.

The voltage reflection coefficient S of each terminal above is S _K = 1 + |E〓(f)/|E _K (f)/1−|E〓(f)
|/|E _K (f)|...(33) In equations (32) and (33), K is each terminal 12 ₁₁ ,
11 corresponding to the subscripts of 12 ₂₁ , 12 ₁₂ and 12 ₂₂ ,
21, 12 and 22.

When the notch filter shown in FIG. 9, that is, the notch filter to which the capacitive compensation circuit 11 is added, is combined with a hybrid circuit, as shown in FIG. 14, (28)
By replacing Y〓 _L (f) in Equations, (30) and (32) with Y〓 _C (f), the voltage between the input terminal and isolation terminal of the hybrid circuit can be calculated in the same way as above. It is possible to determine the power transmission characteristics, the reflected voltage ratio and voltage reflection coefficient at each terminal, etc.

The present inventor determined the transmission characteristics of a diplexer prototype, and found that when a notch filter with an inductive compensation circuit was incorporated, the characteristic curve shown in Fig. 8 was obtained, and when a notch filter with a capacitive compensation circuit was incorporated. In this case, we were able to obtain results that matched extremely well with the characteristic curves shown in Figure 11.

Summary of the effects of the present invention As is clear from the above description, the notch filter of the present invention is simple and easy to configure and manufacture and adjust, has good electrical characteristics, and is a dual mode type, so it can be used in a hybrid circuit or circulator, etc. When combined to form a diplexer, the overall structure is simple and compact, and the cost is low.Especially when a notch filter with an inductive or capacitive compensation circuit is used, it is suitable for video and audio signals in the NTSC television system. It can constitute a CIN diplexer suitable for carrier wave synthesis, etc., and its effects are enormous.

[Brief explanation of the drawing]

1 to 3 are diagrams showing one embodiment of the present invention, FIG. 4 is an equivalent circuit diagram thereof, FIG. 5 is a transmission characteristic curve diagram thereof, and FIGS. 6 and 9 are diagrams of the present invention. Figures 7 and 10 showing other embodiments of the invention are as follows:
Its equivalent circuit diagram, FIGS. 8 and 11 are transmission characteristic curve diagrams, FIG. 12 is a diagram explaining the relationship between its transmission characteristic and voltage reflection coefficient, and FIGS.
The figure shows a diplexer using the notch filter of the present invention, FIGS. 15 and 20 show a conventional diplexer, and FIGS. 16 to 19 show conventional notch filters. Cylindrical side wall, 2... short circuit wall, 3... coupling probe,
4, 4 ₁ and 4 ₂ ... coaxial terminal, 5 and 6 ... resonant frequency fine adjustment element, 7 ... mode coupling fine adjustment element, 8, _{8 1} , 8 ₂ , 8' ₁ , and 8' ₂ ... Notch filter of the present invention, 9 and 11...compensation circuit, 10,
13 ₁ , 13 ₂ , 15 ₁ and 15 ₂ ...branch circuit, 1
2 ₁ and 12 ₂ ... hybrid circuit, 12 ₁₁ and 12 ₂₁ ... input terminal, 12 ₁₂ and 12 ₂₂ ... isolation terminal, 12 ₁₃ , 12 ₁₄ , 12 ₂₃ and 12 ₂₄ ... coupling terminal, 14 ... ...Reflectionless terminator, 1
6 ₁ , 16 ₂ , 17 ₁ and 17 ₂ ... conventional notch filter, 18 ... circular waveguide cavity resonator, 19 ...
...coupling hole, 20...coupling line, 21...main line,
22 and 23 are coaxial terminals.

Claims (1)

[Claims] 1. A coupling probe and an element for individually adjusting the resonance frequencies of H mode and V mode, which have different frequencies, are provided on the cylindrical side wall, and the insertion directions of the elements into the tube are at right angles to each other, A notch filter comprising a circular waveguide cavity resonator formed to have an angular difference of 45° or 135° with respect to the coupling probe. 2. The notch filter according to claim 1, wherein an inductive compensation circuit is added to the terminal of the coupling probe via a branch circuit. 3. The notch filter according to claim 1, wherein a capacitive compensation circuit is added to the terminal of the coupling probe via a branch circuit.