JP2013138319A - Semi-coaxial type band-pass filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semi-coaxial type band-pass filter capable of thickening coupling amounts among resonators required to secure a pass band width without changing a resonant frequency and a Q-value.SOLUTION: In a semi-coaxial type band-pass filter configured by coupling a plurality of resonators individually provided with central conductors 35a and so on, each of the central conductors 35a and so on is formed to have a coaxial structure by folding back a predetermined length of an upper portion of a cylindrical member, and a pair of coupling fins 39a and 39b protruding downward is provided at a lower side periphery of a folded-back portion 38 thereof with intervals of substantially 180°. Each of the central conductors 35a and so on is disposed such that the pair of coupling fins 39a and 39b is positioned so as to face coupling windows formed among individual ones of the plurality of resonators. By providing the coupling fins 39a and 39b at the folded-back portions 38 of the central conductors 35a and so on, coupling among the resonators is thickened, a pass band width of the semi-coaxial type band-pass filter is widened, increases in areas of the folded-back portions 38 are reduced and variations in a resonant frequency are suppressed to be small.

Description

  The present invention relates to a semi-coaxial bandpass filter having a folded coaxial structure used in, for example, a microwave band, a millimeter wave band, or the like.

Conventionally, semi-coaxial filters are generally used in very high frequency bands such as a microwave band and a millimeter wave band (see, for example, Patent Documents 1 and 2).
4A and 4B show a configuration when a conventional semi-coaxial filter is implemented in an antenna sharing device, where FIG. 4A is a side view with a part cut away, and FIG. 4B is a plan view. FIG. 4 shows an example in which the antenna sharing apparatus is configured by 10 stages of resonators.

  In FIG. 4, reference numeral 11 denotes a box formed of a metal plate in a box shape, and includes a bottom plate 12 and a top plate 13 that are detachably provided. The housing 11 is divided into a plurality of, for example, ten spaces by partition walls 14 provided in parallel with the side walls, and cylindrical central conductors 15a, 15b,... Are provided along the central axis of each space to provide a semi-coaxial type. Of the resonators 16a, 16b,. The center conductors 15a, 15b,... Are formed slightly lower than the height of the casing 11, and the lower ends are fixed to the bottom plate 12 of the casing 11 by high-temperature soldering, and are connected to the central axes of the resonators 16a, 16b,. Is held in place. .. Are inserted into the upper ends of the center conductors 15a, 15b,... By a synthetic resin (insulating material), for example, in a substantially cylindrical shape and a locking portion is formed at the head. , 18b,... Are sandwiched and held by the top plate 13.

  .. Are inserted into the inner ends of the center conductors 15a, 15b,... Through the through holes provided in the central axes of the spacers 18a, 18b,. The tuning rods 17a, 17b,... Have screw grooves formed on the outer periphery, and are screwed into screw holes provided in the top plate 13 and fixed by fixing nuts. The tuning rods 17a, 17b,... Can be adjusted in their insertion lengths into the center conductors 15a, 15b,... By loosening the fixing nuts, whereby the tuning frequencies of the resonators 16a, 16b,. Adjust.

  A coupling window is provided in the upper portion of the partition 14 between the resonators 16d, 16e, 16f, 16g, and 16h that require adjustment of the coupling amount. A connecting plate 20 shown in FIG. FIG. 5 shows a configuration of the coupling plate 20, (a) is a front view, (b) is a side view, and (c) is a top view. The coupling plate 20 has a crank-shaped coupling member 23 made of a metal plate attached to the lower end portion of the screw rod 21 via a holding plate (insulating material) 22 by screwing, and the screw rod 21 is attached to the top plate 13. It is screwed into the provided screw hole and fixed with a fixing nut. Since the screw rod 21, that is, the coupling plate 20, can be rotated by loosening the fixing nut, the coupling amount of the resonators 16a, 16b,... Is adjusted by the rotation angle of the coupling plate 20.

Further, an antenna connection terminal 25 is provided on one side surface of the housing 11, and a transmission terminal 26 and a reception terminal 27 are provided on the other side surface.
As described above, the antenna sharing apparatus is configured by coupling the resonators 16a, 16b,... In multiple stages, but the pass bandwidth and attenuation characteristics are determined by the coupling amount between the resonators 16a, 16b,. FIG. 6 shows the relationship between the passband width and the coupling amount between each stage of the resonator in the semi-coaxial filter. The horizontal axis represents frequency and the vertical axis represents attenuation. In FIG. 6, a characteristic a indicates a pass bandwidth when the resonators are coupled with a reference coupling amount, a characteristic b indicates a pass bandwidth when the coupling amount between the resonators is a rough coupling, Characteristic c represents the passband width when the coupling amount between the resonators is tightly coupled. When the resonators are roughly coupled, the pass bandwidth is narrower than the reference property a as shown by the characteristic b in FIG. 6, and when the resonators are tightly coupled, the pass is greater than the reference property a as shown by the property c. Increases bandwidth.

In order to increase the passband width of the semi-coaxial filter, it is necessary to tightly couple the resonators. And in order to tightly couple the resonators,
(1) Reducing the size of the resonator and shortening the distance between the central conductors.
(2) Insert a coupling plate between the stages of the resonator.
There are methods.

In order to increase the passband width of the semi-coaxial filter, the method of reducing the size of the resonator and shortening the distance between the center conductors as in (1) above, and tightly coupling the resonators, The Q value may drop and the desired characteristics may not be satisfied.
The antenna sharing apparatus shown in FIG. 4 uses the method (2) described above, that is, the method in which the coupling plates 20 are inserted between the stages of the resonators to tightly couple the resonators. In this way, in the method of inserting the coupling plate 20 between the resonator stages, the number of parts is increased, the parts management is troublesome, and the assembling work of the parts and the adjustment by the work are required, so that the working efficiency is deteriorated. As a result, the cost increases. Further, in the conventional method in which the coupling plate 20 is provided between the resonator stages and the coupling degree between the resonators is adjusted by the rotation angle, it is difficult to finely adjust the rotation angle of the coupling plate 20. The adjustment of the degree is very troublesome.

  Further, as a method for reducing the size of the resonator, there is a method in which the upper end portions of the center conductors 15a, 15b,... Have a folded coaxial structure as shown in FIG. This folded coaxial structure is a technique for shortening the length that should be a quarter wavelength of the resonance frequency. FIG. 7 is a perspective view showing a configuration example of the central conductor 15 (15a, 15b,...). In this folded coaxial structure, the upper end portion of the central conductor 15 having a total length L1 is folded back by a length L2 to be coaxial.

  FIG. 8A shows an example of combination of dimensions when the total length L1 of the central conductor 15 is set to 260 mm and 180 mm, and the length L2 of the folded portion 28 is set to 45 mm and 70 mm, and FIG. It is a resonance characteristic figure which shows the relationship between the combination dimension of L1, L2, and the resonance frequency. In FIG. 8B, the characteristic a is a resonance characteristic when the total length L1 of the center conductor 15 is 260 mm and the length L2 of the folded portion 28 is 70 mm, and the characteristic A is a reference when L1 is 260 mm and L2 is 45 mm. Resonance characteristics and characteristic b are resonance characteristics when L1 is set to 180 mm and L2 is set to 70 mm, and characteristics c are resonance characteristics when L1 is set to 180 mm and L2 is set to 45 mm.

  When L2 is set to 70 mm with respect to the reference resonance characteristic A when L1 is 260 mm and L2 is 45 mm, the resonance frequency is displaced to be lower than the reference characteristic A as shown by the characteristic a. Further, in a state where L2 is set to 70 mm, when L1 is set to 180 mm short, the resonance frequency is displaced higher than the reference characteristic A as shown by the characteristic b. When L1 is set to 180 mm and L2 is set to 45 mm short, the resonance frequency is displaced higher than the characteristic b as shown by the characteristic c.

As described above, the resonance frequency of the center conductor 15 having the folded coaxial structure varies depending on the total length L1 and the length L2 of the folded portion 28.
In the center conductor 15 of the folded coaxial structure, the folded portion 28 also contributes to the coupling between the resonators. If the folded portion 28 is lengthened, the coupling between the resonators can be made dense. . However, if the folded portion 28 is lengthened, the resonance frequency also changes to the lower side at the same time. At this time, in order not to change the resonance frequency, it is necessary to shorten the length L1 of the center conductor 15.

  On the other hand, in order to widen the pass band, it is necessary to make the coupling between the resonator stages dense as shown in FIG. If the folded portion 28 of the center conductor 15 is lengthened, close coupling can be achieved. However, the resonance frequency is lowered correspondingly, and if the length L1 of the center conductor 15 is shortened to correct it, the Q value is deteriorated, and the filter performance. Will get worse.

JP 2008-205682 A JP 2007-300252 A

  As described above, in the conventional antenna sharing device using the semi-coaxial filter having the folded coaxial structure, the folded portion 28 of the center conductor 15 is lengthened to increase the coupling between the resonators in order to widen the pass bandwidth. At the same time, the resonance frequency also changes to the lower side. Further, if the length of the central conductor 15 is shortened to correct the decrease in the resonance frequency, there is a problem that the Q value is deteriorated and the filter performance is deteriorated.

  The present invention has been made in order to solve the above-described problems, and is a semi-coaxial type capable of obtaining coupling between resonators necessary for ensuring a pass bandwidth without changing the resonance frequency and the Q value. An object is to provide a bandpass filter.

  According to a first aspect of the present invention, there is provided a casing made of a conductive member having a bottom plate and a top plate, a partition provided in the top plate direction from the bottom plate and dividing the inside of the casing into a plurality of regions, and the top of the partition. A coupling window that is provided on the plate side and connects between the steps of the region; a hollow cylindrical central conductor that is disposed along the central axis of each region and has one end fixed to the bottom plate; A folded portion provided by folding the other end portion of the center conductor coaxially with a predetermined length; a pair of coupling fins provided by extending the folded tip periphery of the folded portion at an interval of approximately 180 °; A tuning rod that is mounted on the top plate corresponding to each of the regions, and that has a tip portion inserted into a tip opening portion of the center conductor, and each center conductor is connected to each of the folded portions. The fins are disposed so as to face the coupling window, and the step of each region is arranged. Wherein the degree of coupling is configured to be dense.

  According to a second aspect of the present invention, in the semi-coaxial bandpass filter according to the first aspect of the present invention, a screw hole is provided at a position corresponding to the step of each region of the top plate, and a coupling amount adjusting screw is provided in the screw hole. The front end portion is inserted into the coupling window by screwing, and the coupling amount between the steps of each region can be adjusted by the insertion length of the coupling amount adjusting screw into the coupling window. And

  According to the present invention, it is possible to widen the passband width by providing coupling fins at the folded portion of the central conductor and tightly coupling the resonators. Further, by providing the coupling fin only in the part facing the coupling window between each stage of the resonator, the increase in the area of the folded portion can be reduced, and the deviation of the resonance frequency can be reduced, and the Q value can be reduced. It can be surely prevented.

It is sectional drawing which shows the structure of the semi-coaxial type | mold band pass filter which concerns on one Embodiment of this invention. It is a perspective view which takes out and shows only the center conductor in FIG. It is a figure which shows the pass-band characteristic of the semi-coaxial type | mold band pass filter which concerns on the same embodiment. The structure at the time of implementing the conventional semi-coaxial filter in the antenna sharing apparatus is shown, (a) is a side view with a part cut away, and (b) is a plan view. The structure of the coupling plate in the antenna sharing apparatus of FIG. 4 is shown, (a) is a front view, (b) is a side view, and (c) is a top view. It is a figure which shows the relationship between the pass-band width in a semi-coaxial filter, and the coupling amount between each stage of a resonator. It is a perspective view which shows the structural example at the time of making the center conductor in the conventional semi-coaxial filter into a folding coaxial structure. It is a resonance characteristic figure which shows the relationship between the example of the setting dimension of the center conductor of a folding coaxial structure in the conventional semi-coaxial filter, and the resonance frequency.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing the configuration of a semi-coaxial bandpass filter 30 according to an embodiment of the present invention, and FIG. 2 is a perspective view showing only the central conductor in FIG. FIG. 1 shows an example in which a semi-coaxial bandpass filter 30 is configured by, for example, five stages of resonators.

  In FIG. 1, reference numeral 31 denotes a casing formed of a metal plate in a box shape, and includes, for example, a bottom plate 32 and a top plate 33 that are detachably provided. For example, the casing 31 is set to have a height H1 of about 273 mm and a lateral width W1 of 210 mm. The housing 31 is divided into a plurality of, for example, five spaces by partition walls 34a, 34b,..., And cylindrical center conductors 35a, 35b,... Are provided along the central axis of each space to provide a semi-coaxial resonator 36a. , 36b,... Each of the partition walls 34a, 34b,... Has a height H2 from the bottom plate 32 of about 162 mm, and is provided with coupling windows 37a, 37b,... That connect the resonators 36a, 36b,. Further, the interval W2 between the partition walls 34a, 34b,... Is set to about 40 mm.

  As shown in detail in FIG. 2, the center conductors 35a, 35b,... Are made of a cylindrical member having a diameter (outer diameter) D1 of about 12 mm, and a folded portion 38 is provided on the upper end side. The center conductors 35a, 35b,... Are set to have a total length L11 of about 260 mm, a height L12 of the folded portion 38 of about 50 mm, and a diameter (outer diameter) D2 of the folded portion 38 of about 30 mm, for example. The folded portion 38 is provided with a pair of coupling fins 39a and 39b extending downward at an interval of approximately 180 ° on the lower peripheral edge. The length L13 of the coupling fins 39a and 39b is set to about 20 mm, and the lateral width W3 is set to about 10 mm.

  The center conductors 35a, 35b,... Are disposed along the central axis of the resonators 36a, 36b,..., And the lower ends are fixed to the bottom plate 32 of the housing 31 by high-temperature soldering. In this case, the center conductors 35a, 35b,... Are provided so that the coupling fins 39a, 39b of the folded-back portion 38 are located opposite to the coupling windows 37a, 37b,. Further, the lower ends of the spacers 41a, 41b,..., Which are formed in, for example, a substantially cylindrical shape and have locking portions at the heads, are press-fitted inside the upper ends of the center conductors 35a, 35b,. The locking portion is held in pressure contact with the top plate 33.

  .. Are inserted into through holes provided in the central axes of the spacers 41a, 41b,... Inside the upper ends of the central conductors 35a, 35b,. The tuning rods 42 a, 42 b,... Have screw grooves formed on the outer periphery, are screwed into screw holes provided in the top plate 33, and are fixed by a fixing nut 43. The tuning rods 42a, 42b,... Can be adjusted in insertion length into the center conductors 35a, 35b,... By loosening the fixing nut 43, thereby tuning the resonators 36a, 36b,. Adjust the frequency.

  Further, the top plate 33 has a predetermined amount of coupling amount adjusting screws 44a, 44b made of metal in screw holes provided between the tuning bars 42a, 42b,..., That is, at positions corresponding to the coupling windows 37a, 37b,. Are screwed and fixed to the top plate 33 by a fixing nut 45. The coupling amount adjusting screws 44a, 44b,... Are inserted into coupling windows 37a, 37b,... Provided between the resonators 36a, 36b,. The coupling amount adjusting screws 44a, 44b,... Can be rotated by loosening the fixing nut 45, and the coupling amount between the resonators 36a, 36b,. adjust.

  The casing 31 is provided with an input / output terminal 51 on the side surface on the resonator 36a side, and an input / output terminal 52 on the side surface on the resonator 36e side. The outer conductor of the input / output terminal 51 is electrically connected to the side surface of the casing 31, and the central conductor is connected to the bottom plate 32 of the casing 31 through the input / output loop 53 made of a conductive member in the resonator 36a. Is done. Further, the outer conductor of the input / output terminal 52 is electrically connected to the side surface of the casing 31, and the center conductor is connected to the bottom plate 32 of the casing 31 via the input / output loop 54 made of a conductive member in the resonator 36e. Connected. The height H3 of the input / output terminals 51 and 52 is set to about 102 mm.

  The semi-coaxial bandpass filter 30 according to the above embodiment is opposed to the folded portions 38 of the central conductors 35a, 35b,... At the lower peripheral edge at an interval of 180 °, that is, to the coupling windows 37a, 37b,. The coupling fins 39a, 39b are provided only in the portions so that the resonators 36a, 36b,... Are tightly coupled, so that the resonance frequency shift in the resonators 36a, 36b,. And the deterioration of the Q value can be reliably prevented.

  FIG. 3 shows the passband characteristics of the semi-coaxial bandpass filter 30. The horizontal axis represents frequency [MHz] and the vertical axis represents attenuation [dB]. In FIG. 3, the characteristic a is obtained when the coupling fins 39a, 39b are provided in the folded portions 38 of the center conductors 35a, 35b,... And the resonators 36a, 36b,. The pass band characteristic when the resonators 36a, 36b,... Are roughly coupled without providing the coupling fins 39a, 39b at the folded portions 38 of the center conductors 35a, 35b,. Is shown.

  As is apparent from FIG. 3, the coupling fins 39a are provided by providing coupling fins 39a, 39b at the folded portions 38 of the center conductors 35a, 35b,. , 39b, the passband width of the filter can be increased compared to the case where 39b is not provided.

  Further, since the coupling fins 39a, 39b are provided only at portions facing the coupling windows 37a, 37b,... Between the stages of the resonators 36a, 36b,..., The spaces between the resonators 36a, 36b,. The increase in the area of the folded portion 38 can be reduced as compared with the case where the folded portion 38 is lengthened as a whole for tight coupling, and the deviation of the resonance frequency in the resonators 36a, 36b,. . Therefore, it is not necessary to shorten the lengths of the central conductors 35a, 35b,... To correct the resonance frequency shift in the resonators 36a, 36b,.

  Further, by providing coupling fins 39a, 39b to the folded portions 38 of the center conductors 35a, 35b,... And tightly coupling the resonators 36a, 36b,..., As coupling amount adjusting screws 44a, 44b,. The amount of coupling can be easily adjusted using a metal screw having a simple structure such as an M5 (millimeter screw / metric thread standard) screw, and there is no need to use a coupling plate having a complicated structure as in the prior art.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage.

  DESCRIPTION OF SYMBOLS 30 ... Semi-coaxial type band pass filter, 31 ... Housing, 32 ... Bottom plate, 33 ... Top plate, 34a-34d ... Partition, 35a-35e ... Central conductor, 36a-36e ... Resonator, 37a-37d ... Coupling window, 38 ... Folded portion of the central conductor, 39a, 39b ... Fin for coupling the central conductor, 41a to 41e ... Spacer, 42a to 42e ... Tuning rod, 43, 45 ... Fixing nut, 44a to 44d ... Coupling amount adjusting screw, 51 52, I / O terminals, 53, 54 ... I / O loops.

Claims (2)

A housing made of a conductive member having a bottom plate and a top plate;
A partition wall provided in the top plate direction from the bottom plate and dividing the inside of the housing into a plurality of regions,
A coupling window that is provided on the top plate side of the partition wall and couples the steps of the region;
A hollow cylindrical center conductor disposed along the central axis of each region, one end of which is fixed to the bottom plate;
A folded portion provided by folding the other end of the central conductor into a predetermined length coaxially;
A pair of coupling fins provided by extending the periphery of the folded portion at an interval of approximately 180 °;
A tuning bar that is mounted on the top plate corresponding to each of the regions, and a tip portion is inserted into a tip opening of the center conductor;
The center conductors are disposed so that the coupling fins provided in the folded portion are positioned to face the coupling window, so that the degree of coupling between the steps of the respective regions is dense. A semi-coaxial bandpass filter characterized in that it is configured as described above. The semi-coaxial bandpass filter according to claim 1,
A screw hole is provided at a position corresponding to the step of each region on the top plate, a coupling amount adjusting screw is screwed into the screw hole, a tip portion is inserted into the coupling window, and the coupling amount adjusting screw is A semi-coaxial bandpass filter characterized in that the coupling amount between the stages of each region can be adjusted by the insertion length into the coupling window.

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