JPS595701A - Comb line type band-pass filter - Google Patents

Abstract

PURPOSE:To reduce the size of a comb line type band-pass filter (BPF) for microwaves even when a load is high by interposing aperture type coupling windows among resonators constituting the comb line type BPF. CONSTITUTION:The electric axial length of resonating elements 41-4n made of bar conductors is set to a quarter resonance length lambda when the width H of a housing 1 and the diameters of the resonating elements are relatively less (e.g. 0.1lambda and 0.2lambda) than the resonance wavelength lambda, and the electric axial length of the resonating element is made adequately less than a quarter the resonance wavelength; and ungrounded end parts of the resonating elements are held in electrically open or nearly open states. Then, aperture type coupling windows 51-5n-1 have upper, external, and lower edges in contact with intermediate parts of adjacent resonating elements, e.g. the upper wall, side wall, and bottom wall of the housing 1 corresponding to a half the center-axis interval while set parallel to the axial direction of the resonating elements, and also arranged at the facing interval between two facing conductor plates 51' and 5n-1' perpendicular to the side wall of the housing 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combline bandpass filter for microwaves. Hereinafter, the bandpass filter will be abbreviated as BPF.

The present inventor first proposed a combline type microphone for O-waves that has a simple structure, excellent voltage resistance characteristics, stable electrical characteristics without being affected by changes in ambient temperature, and is suitable for high power applications. I proposed BPF. (Japanese Patent Application No. 57-61315) Fig. 1 is a sectional view showing the structure (B-8 sectional view in Fig. 2), and Fig. 2 is a sectional view taken along A-A in Fig. 1. Here, l is an electromagnetic shielding case, 2I and 2 are input/output coaxial terminals, 3I and 32 are input/output coupling elements, 4I to 46 are resonant elements made of rod-shaped conductors, and the resonant wavelength is approximately 4.
It has an axial length of In this BPF, coupling is performed by the magnetic field generated by the resonant current flowing through the resonant element, and the magnetic field coupling attenuation between adjacent resonant elements, h, depends on the width H of the housing 1 and the cutoff wavelength. c=28
If there is a relationship such as =su(1<2H;); . , if there are two people,
t, h (dB)≠total ・・・・・・(2)
H Magnetic field coupling coefficient M between adjacent resonant elements. is expressed as Lh (rose) 1] M, = IO...1 (3).

Now, if we calculate the center axis spacing C of adjacent resonant elements when the load Q is 100 in the relationship M(0, 2λ), from equation (3), one collapse μ times M, = 1O20, so 1ogM, ”-Tanmu eaves 0 and then Lh (dB) = -201ogM.

Also, from equation (2), 54.60 r, h (as) circle □ H, so from the setting conditions 1 M, = −= −=O, 0I QL 100 Therefore, as is clear from the above equation, this BPF In the case, the load Q
In order to make 100, it is necessary to select the center axis spacing C of adjacent resonant elements to be approximately 1.5 times the width H of the housing 1, which is larger than that of the hole-coupled BPF or capacitively coupled BPR'. The size increases by approximately 50%.

In addition, FIG. 3 shows i (horizontal axis,
Evenly spaced scale) and magnetic field coupling coefficient yo (vertical axis, logarithmic scale)
It is a curve diagram showing the relationship.

In addition to the advantages of the above-mentioned combline BPF for microwaves, which was proposed by the present inventor, the present invention realizes a combline BPF for microwaves that can be configured in a small size even when the load Q is increased. The purpose is to

FIG. 4 is a sectional view (C in FIG. 5) showing one embodiment of the present invention.
-C sectional view), Figure 5 is the AA sectional view of Figure 4,
The figure is a sectional view taken along line B-8 in Figure 4. In each figure, 1 is an electromagnetic shielding case, 2+ and 2Q are input/output coaxial terminals, and 3I and 3λ are input/output coupling elements, such as strip lines. . Instead of using strip lines, input/output coupling may be performed by tap coupling, loop coupling, coupling using capacitance between the 1t ribbon conductor and the resonant element, or the like. 4I to 4yL are resonant elements made of rod-shaped conductors, and the width of the housing 1 (6th
H in the figure) and the diameter of the resonant element is relatively small (e.g. 0.1
0.2^), the axial length of the resonant element should be chosen to be the electrical length of the resonant wavelength, and if the width H of the housing l and the diameter of the resonant element are relatively large compared to the resonant wavelength. In this method, the axial length of the resonant element is made appropriately shorter than the resonant wavelength in electrical length, and the non-grounded end of each resonant element is kept electrically open or almost open. Next, 5+ to 5x- are diaphragm-type coupling windows, and the upper edge, outer edge, and lower edge are connected to the middle of the adjacent resonant elements, for example, the earth wall, side wall, and two opposing conductor plates 5 that are in close contact with the bottom wall, parallel to the axial direction of the resonant element, and perpendicular to the side wall of the housing 1;
Consists of 1 to 5 to -1 opposed castings. Note that one of the two opposing conductor plates may be omitted,
Furthermore, the upper edge of the conductor plate does not necessarily have to be in close contact with the earthen wall of the casing.

Now, assuming that the diaphragm-type coupling window 51 or hole 5-1 is not provided, the distance between the width H of the housing 1 and the resonance wavelength is H<0.2.
If there is a relationship between two people, the interstage magnetic field coupling attenuation Lh is
) From the formula, 1, 54.6G Lh (as) = - H Also, from the formula (3), the groin magnetic field coupling coefficient M0 is - foot theft 0 M, = IO Here, the volumetric efficiency is the best, and the no-load Q is Given a good condition, H-ring C, Lh (dB) ball history = 27.3 (dB) Therefore, it becomes.

Next, when the aperture-type coupling windows 51 to 5tt-t are provided, the magnetic field of each aperture-type coupling window portion is in the 90'' direction with respect to the direction parallel to the resonant element, and with respect to the side wall of the housing 1. The magnetic field coupling coefficient M at each crotch in this case can be changed by changing the ratio between the width H of the housing 1 and the aperture width D (Fig. 6), and D M =M6- It can be expressed as (5).

Substituting the above M = 0.04315 into the above formula, M = 0.04315-...
(6) Therefore, D = -1 (粍23.2MH... (7)
0.04315 Now, M = O + O1 (Q [= +00), H = 18
(mm), then from equation (7), o 輌23.2xo, o+ x +s = a, 2(mm
) That is, if the width of the housing 1 is 18 (mm), by setting the aperture width to IZ4.2 (mm), the load Q (
Qt) can be set to 100, but in this case, H'
, C. As mentioned above, C1+ is approximately +8 (mm). Load Q (Q
L) When tloO, B shown in Figures 1 and 2
As mentioned above, in a PF, it is necessary to select the center axis distance C between adjacent resonant elements to be approximately 1.5 times the width H of the housing. If the width H of each casing in the BPF of the present invention is selected equally, C of the BPF of the present invention will be approximately the same as C of the BPF shown in FIGS. 1 and 2, and the overall size can be reduced by that much. .

In addition, FIG. 7 shows l (horizontal axis,
It is a curve diagram showing the relationship between the magnetic field coupling coefficient M (vertical axis, logarithmic scale) and the magnetic field coupling coefficient M (vertical axis, logarithmic scale), and points A and B are points where the theoretical value and the measured value coincide.

Next, when designing a distributed parameter type BPF, it is common to design by finding the element values of a reference low-pass filter, that is, the geometric coefficients. For example, the element values of a Che and Sheff type reference low-pass filter. is 2a+ 6,=-・・・・・・(8) γ aaX−1e aK g”” bM−1” gH−+ ・・・・・・
・Represented by (9). However, γ= Binh (-”-) n β=fln (aoth ”) 17, 37 Allowable voltage standing wave ratio within the S2 passband aakπ b3=7+5 ink=l, 2,... nI) 1T
) The element value g associated with the resonant element 41 is expressed as (8) → the element value g2 associated with the four resonant elements is expressed as (9)
Substitute 2 for k in the formula to find each, and use the following 4 or 4
．． The element values g□ to grL related to are respectively determined by substituting 3 to n for k in equation (9).

Next, the magnetic field coupling coefficient between each stage in the Chebyshev type BPF is:
). However, BWF: allowable passband width f, number of center frequency resonators in two passbands, i.e. BPF order n1 passband width F3yp
and the center frequency f of the passband. etc., and set the magnetic field coupling coefficients M and M K of equations (6) and (lO) as appropriate.
, and +I are equal for each stage.
1 to 51-1. That is, since the width H of the housing 1 is given by the resonance wavelength λ and the insertion loss, the dimension of H and the center axis spacing C of adjacent resonant elements are formed to be approximately equal, By appropriately determining D in equation (6), it is possible to construct a combline BPP with Chebyshev-type characteristics in the passband and Wagner-type characteristics in the attenuation region, and its transmission characteristics are expressed by the following equation.

However, the attenuation amount T (X) is a Chebisch I polynomial, and when x<1, 7K (X) = cos (n cos-' x ) x>
For I, TrL(x) = coeh (n cash' x )
fa f f.

X = = (---) Bwr fa f Figure 8 is a characteristic curve diagram of this BPF', where the horizontal axis is the transmission frequency t (GH2) and the vertical axis is the attenuation amount L ((IB >).

FIG. 9 is a sectional view showing another embodiment of the present invention (CC sectional view in FIG. 10), FIG. 1θ is a sectional view taken along A-A in FIG. 9, and FIG. In the B-8 sectional view of the figure, in each figure,
61 to 671 are dielectric resonators, for example, as shown in an enlarged cross-sectional view in FIG. A metal coating such as silver or copper that forms the internal conductor of the device is deposited by vapor deposition, and its axial length is selected to be an electrical length that minimizes the resonance wavelength, and components such as heat dissipation and input/output coupling capacitance elements are placed inside it. A rod-shaped conductor +4 for attachment is inserted, and a screw hole 15 for insertion of a fixing screw is bored in the bottom of the rod-shaped conductor +4. A metal coating such as silver or copper that forms the external conductor of the resonator can be provided on the surface of the rectangular parallelepiped 12 made of a dielectric material, excluding the open surface and the coupling surface (the side wall surface facing the adjacent resonator). be. That is, in the case of the first stage resonator, as shown in the enlarged plan view in FIG. In this case, as shown in the enlarged plan view in FIG. 14, metal coatings 17 to 19 are attached to the surface portion of the rectangular parallelepiped +2 that is in contact with the end wall and both side walls of the housing 1,
In the case of other resonators, metal coatings 17 and 18 are attached to the surface portions of the rectangular parallelepiped 12 that are in contact with both side walls of the housing, as shown in an enlarged plan view in FIG. Incidentally, a metal coating 20 (FIG. 12) is attached to the bottom surface of each dielectric resonator.

Instead of the metal coatings I6 to 20, a shield plate may be fixed, and instead of attaching the metal coatings 6 to 20, and instead of fixing the shield plate, the end walls, both side walls and the bottom wall of the housing 1 may be fixed. may also be used as the outer conductor of the resonator. A metal coating 1 is applied to the inner wall surface of a through hole formed in a rectangular parallelepiped 12 made of a dielectric material.
The rod-shaped conductor 14 may be directly inserted into this through hole without attaching the conductor 3, and the rod-shaped conductor 14 may be formed so as to serve as the internal conductor of the resonator, the heat sink, the support of the component, etc. If the heat generation is small, the rod-shaped conductor 14 is omitted, a lead wire for connection to the component is attached to a part of the metal covering 111j13 attached to the inner wall surface of the through hole, and a screw hole is bored in the bottom wall of the rectangular parallelepiped 12. Good too.

Next, in Figures 9 to 1, 7I to 7g
-+ is a metal film forming a diaphragm-shaped coupling window, and is formed by depositing silver, copper, or the like on each coupling surface of rectangular parallelepiped +2 forming dielectric resonators 6I to 6FL- by vapor deposition or the like.

7K (k=1
．． 2,...n-1) is a metal coating that forms a diaphragm-shaped coupling window, and FIG. As shown, it may also be provided on the other open surface, and in this case, it may also be provided on the open surface of the final stage resonator as shown by the dotted line in FIG. 8+ in Figures 9 to 11
84 to 84 are set screws, 9I and 9 are input/output coaxial terminals, 101 and 102 are input/output coupling capacitance elements, 11+
to Hy(-+ is the air gap between adjacent dielectric resonators.

In this example, in the magnetic field generated by the resonant current of the dielectric resonator, the leakage magnetic field from the coupling surface is coupled via the coupling surface of the adjacent dielectric resonators facing each other, and the coupling characteristic is (1). By setting 8C in the equation to 2H (ε is the dielectric constant of the rectangular parallelepiped 12 forming the resonator), find the magnetic field attenuation of the electric body part, find the magnetic field attenuation of the air gap part from equation (2), and further ( 3) By finding the magnetic field coupling coefficient M0 from equation (6), the magnetic field coupling coefficient M can be found from FIG. By determining the aperture width of the shaped coupling window, the desired transmission characteristics can be obtained.

Instead of forming the dielectric part of the dielectric resonator into a rectangular parallelepiped, it is formed into a thick cylindrical body, and a metal coating that forms an external conductor is attached to the inside of the outer surface, excluding the open surface and the coupling surface. The present invention can also be practiced using a resonator made of.

FIG. 16 is a cross-sectional view showing an example (B-B in FIG. 17).
17 is a sectional view taken along the line A-A of No. 160, and in both figures, 6; to 6' are cylindrical dielectric resonators, and the other symbols are the same as in FIGS. 9 to 11. The same is true.

The coupling effect and transmission characteristics in this embodiment are similar to those in the previous embodiment, and the magnetic field coupling coefficient can be adjusted by changing the width of the coupling surface, that is, the ratio of the aperture width of the aperture-shaped coupling window to the diameter of the dielectric resonator. I can do it. As shown in the figure, by providing groove-shaped recesses with an arcuate cross section on the side walls and end walls of the housing 1 that are in contact with the cylindrical dielectric resonator, the resonator can be stably held and the contact area with the side wall of the resonator can be reduced. Because it can be made larger, the case 1
This is advantageous when used as an external conductor of a resonator, and by changing the thickness of the side wall of the casing corresponding to the air gap 111 to U-rL-, that is, the depth of the groove-like recess with an arcuate cross-section. The aperture width of the aperture-shaped combined window can be adjusted.

In each of the above embodiments, the case where the resonators are arranged in a line has been exemplified, but by arranging them in a U-shape, the overall size can be further reduced.

In addition, in any of the embodiments, among the resonators in a cascade connection, two or an integral multiple of the resonators are separated from each other by, for example, a coaxial line, a loop, or an internal conductor of the resonator and a capacitor. A polarized BPF can be constructed by indirectly coupling via a coupling element or the like. In this case, among the signals transmitted through the main circuit consisting of cascade-connected resonators, the phase of the voltage and current in each resonator is 90° ahead (δ) of a signal with a frequency higher (lower) than the passband. , the phase is 270 in the phase shift circuit formed in a cylindrical manner.
For example, the phase of the signal in the second-stage resonator and the phase of the signal in the fifth-stage resonator will be in the same phase because of the advance (lag). By making the constant of the indirect coupling circuit appropriate and making the coupling polarity between the resonator and the indirect coupling circuit appropriate, a signal is transmitted from the second stage resonator to the fifth stage resonator via the indirect coupling circuit. produces a phase difference of 180' between both resonators. Therefore, by adjusting the degree of coupling between the resonator and the indirect coupling circuit, the magnitude of the signal reaching the fifth stage resonator via the indirect coupling circuit and the main By equalizing the magnitude of the signal that reaches the fifth stage resonator via the circuit, it is possible to generate an attenuation pole at the frequency position of this signal. The present invention can be practiced by arbitrarily selecting the number of indirectly coupled resonators to carry out the invention.

Furthermore, in any of the above embodiments, the coupling adjustment is performed from the top wall or the bottom wall of the housing, or from both the top wall and the bottom wall, corresponding to the gap between the symmetry elements made of rod-shaped conductors or the gap between the dielectric resonators. The electric field component of the cut-off waveguide mode is adjusted according to the insertion length of the coupling adjustment screw by inserting the screw into the hollow part parallel to the internal conductor of the resonator and forming it so that it can be fixed at any insertion length. As a result, the electric field is concentrated on the coupling adjustment screw, the electric field becomes stronger, and the coupling magnetic flux density increases accordingly, so that the step-opening coupling can be made denser depending on the insertion length of the coupling adjustment screw.

As is clear from the above description, the present invention enables miniaturization even when the load Q is high (＼) by interposing a diaphragm-type coupling window between the resonators in which the combline type BPF is installed.
Not only is the design easy, but the configuration is simpler than that of a trapezoidal hole-type BPF or a capacitively coupled BPF, and during manufacturing, it is easy to perform surface treatment of the inner wall surface of the housing, the surface of the conductor plate for forming the coupling window, etc., and to adjust the assembly. It is possible to produce a highly reliable product at low cost from scratch, and its effects are enormous.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing a bandpass filter proposed by the present inventor, FIG. 3 is a diagram showing the relationship between the resonant element spacing and the magnetic field coupling coefficient, and FIGS. Figure 6 is a sectional view showing an embodiment of the present invention, Figure 7 is a diagram showing the relationship between the aperture width of the aperture type connection + window and the magnetic field coupling coefficient, and Figure 8 is a diagram showing the transmission of the filter of the present invention. Figures showing examples of characteristics, Figures 9 to 1
1, 16, and 17 are cross-sectional views showing other embodiments of the present invention, and FIGS. 12 to 15 are views showing examples of essential elements. 1: Electromagnetic shielding case , 21% 2
a. 9I and 9coni input/output coaxial terminals, 3t% 3a%
+01 and 10 coni input/output coupling elements T141 to 4 uni-resonant elements, 5I to 5rL-+: Diaphragm type coupling window, 51 to 5'Rule l: Conductor plate for forming the aperture type coupling window, 6t to 67L and 6- to 6;I
:Dielectric resonator, 7I to 7-I and 7:
Metal cover for forming an aperture-shaped coupling window, 81 to 8rL: Set screw, 11 to l11t-, : void, 12: Rectangular parallelepiped made of dielectric, 13 and 16 to 2o: metal coating, 14: rod-shaped conductor, 15 :It's insipid. Agent Souji Kiyosawa Figure 1 Figure 3 Figure 4 Figure 5 Figure 6 Figure 2゜Figure 7 U Day Figure 8 f. f□ Figure 9 Figure 10 Figure 11

Claims (1)

[Scope of Claims] (A plurality of resonators each having an internal conductor having an axial length approximately equal to one resonance wavelength are arranged in series in an electromagnetic shielding casing with the same polarity interposed through a gap, and A combline type bandpass filter characterized in that a diaphragm-type coupling layer is interposed in the air gap.(2) A plurality of resonators each having an inner conductor having an axial length approximately equal to the resonance wavelength The resonators have the same polarity in the electromagnetic shielding case and are arranged cascaded through a gap, with a diaphragm-shaped coupling window interposed in the gap i1j, and among the plurality of resonators, the number of resonators is two or an integral multiple thereof. A combline type bandpass filter characterized in that resonators separated by two resonators are indirectly coupled to each other. (3) A plurality of resonators each having an inner conductor having an axial length of approximately 4 times the resonant wavelength. The devices are arranged cascaded through a gap while maintaining the same polarity in the electromagnetic shielding body, and a diaphragm-shaped coupling window is interposed in the gap, and a coupling adjustment screw capable of changing the insertion length is inserted into the gap. A combline type bandpass filter characterized by: (4) A combline type bandpass filter according to any one of claims 1 to 3, wherein a plurality of resonators are arranged in a line. Filter. (5) The combline bandpass according to any one of claims 1 to 3, in which a plurality of resonators are arranged to form a U-shaped signal transmission path. Filter. (6) The combline according to any one of claims 1 to 3, wherein the resonator comprises a rod-shaped conductor forming an inner conductor and an electromagnetic shielding case forming an outer conductor. (7) The comb line according to any one of claims 1 to 3, wherein the resonator is formed by interposing a rectangular parallelepiped made of dielectric between the inner conductor and the outer conductor. (8) The comb according to any one of claims 1 to 3, wherein the resonator is formed by interposing a cylindrical body made of a dielectric material between the inner conductor and the outer conductor. Line-type bandpass filter. (9) The aperture-type coupling window has its outer edge and lower edge in close contact with the side wall and bottom wall of the electromagnetic shielding case, is parallel to the internal conductor of the resonator, and is parallel to the internal conductor of the electromagnetic shielding case. The combline type bandpass filter according to any one of claims 1 to 3, which is formed by a conductor plate perpendicular to the side wall of the body. A combline type bandpass filter according to any one of claims 1 to 3, which is formed by a metal coating attached to the joint surface of the body part and whose side edges and lower edge are in close contact with the outer conductor. Wave equipment. (11) Claim 1 in which the aperture-shaped coupling window is formed by the side wall of the electromagnetic shielding case corresponding to the gap between the resonators in which a cylindrical body made of dielectric material is provided on the outer periphery of the internal conductor.
The combline type bandpass filter according to any one of Items 1 to 3. (12) The resonator consists of a cylindrical body made of a dielectric turtle provided on the outer periphery of an internal conductor, and an electromagnetic shielding casing having a groove-shaped recess with an arcuate cross section on the inner wall surface in contact with the side surface of the cylindrical body. A combline type bandpass filter according to any one of claims 1 to 3.