JP2011035510A - High frequency filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust strength of combination between resonance elements by means of one filter structure when filtering characteristics has dispersion due to an etching error of a resonance element pattern. <P>SOLUTION: In a high frequency filter which has a substrate 100 where four resonance elements 140a to 140d formed by microstrip line paths are placed at regular intervals and a shield case 200 surrounding the substrate 100, the shield case 200 places three conductive rods 300 to 320 so as to face a gap between central resonance elements 140b and 140c from a ceiling surface of the shield case 200, so that a distance between the conductive rods 300 to 320 and the gap between the central resonance elements 140b and 140c is adjustable. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a high-frequency filter that handles high-frequency signals such as a microwave band and a millimeter wave band, and more particularly to a structure that adjusts filter characteristics.

  Conventionally, high-frequency devices that handle high-frequency signals are equipped with various high-frequency circuits such as amplifiers, mixers, and filters. Among these filters, there is a filter in which a plurality of resonant elements formed by microstrip lines on a substrate are arranged side by side at a predetermined interval to pass and suppress a predetermined frequency band. Such filters include a half-wavelength side coupling filter, an interdigital filter, a hairpin filter, and the like, and a predetermined filter characteristic is obtained depending on the resonance frequency of each resonance element, the characteristic impedance, and the coupling degree between the resonance elements. be able to.

  However, in the case of a filter in a high frequency band such as a microwave band, the dimensions such as the width and length of each resonant element and the distance (gap) between the resonant elements are slightly shifted from the design value. In order to affect the characteristics, the pattern dimension accuracy of the microstrip line is required to be high. The pattern of the microstrip line on the substrate is formed by etching a metal such as copper foil, but a predetermined filter characteristic may not be obtained due to an etching error at this time.

  Therefore, a structure for adjusting the variation in filter characteristics due to such an etching error has been proposed. As shown in FIGS. 6A and 6B, the structure for adjusting the variation in the filter characteristics includes a substrate 16 on which a plurality of hairpin resonators 11 are formed, and a shield case 30 surrounding the substrate 16. In the superconducting filter constituted by the structure, a plurality of conductor screws 12 are arranged at a certain height from each hairpin resonator 11 so as to be movable in parallel with respect to the hairpin resonator 11 from the side of the shield case 30. It has become.

  In this structure, the gap between the resonators 11 becomes wider than the design value due to the etching error of the pattern of the hairpin resonator 11, and the coupling between the resonators 11 becomes weak. When the bandwidth is narrowed, the distance between the conductor screw 12 and the resonator 11 is increased to increase the coupling between the resonators 11 so that the frequency bandwidth can be increased (for example, , See Patent Document 1).

  Further, as shown in FIG. 7 and FIG. 8, in each superconducting filter composed of a substrate 3 on which a plurality of microstrip line resonant elements 4 a to 4 f are formed and a shield case 1 surrounding the substrate 3. A plurality of partition plates 5a to 5e that hang in parallel with respect to the resonant elements 4a to 4f of the microstrip line from the ceiling surface of the shield case 1 are arranged at positions facing the gaps between the resonant elements 4a to 4f of the strip line. It has a structure.

  In this structure, the gap between the resonant elements 4a to 4f becomes narrower than the design value due to the etching error of the pattern of the resonant elements 4a to 4f of the microstrip line, and the coupling between the resonant elements 4a to 4f becomes stronger. When the frequency bandwidth becomes wider than the filter characteristics of the above, the presence of the plurality of partition plates 5a to 5e weakens the jumping coupling (coupling by spatial propagation) over the adjacent resonant elements and narrows the frequency bandwidth. (For example, refer to Patent Document 2).

  However, in the case of the above-mentioned Patent Documents 1 and 2, only the adjustment of either the frequency bandwidth is widened or narrowed depending on whether the coupling between the resonant elements is strengthened or weakened. Therefore, there is a drawback that both adjustments cannot be performed by one filter structure.

Japanese Patent Application Laid-Open No. 2007-208893 (2nd page to 5th page, FIG. 2) Japanese Patent Laid-Open No. 2001-102809 (2nd to 4th pages, FIGS. 1 and 2)

  In view of the above problems, an object of the present invention is to provide a high-frequency filter that can adjust the strength of coupling between resonant elements with a single filter structure when there is variation in filter characteristics due to etching errors in the pattern of the resonant elements. To do.

  In order to solve the above-mentioned problems, the present invention provides a high-frequency filter having a substrate configured by arranging a plurality of resonant elements formed of microstrip lines at predetermined intervals, and a shield case surrounding the substrate. A plurality of conductor rods are arranged on the shield case so as to face a gap between the predetermined resonance elements from a ceiling surface of the shield case, and a gap between the plurality of conductor rods and the predetermined gap between the resonance elements is The distance is adjustable.

  According to a second aspect of the present invention, in the high-frequency filter according to the first aspect, the shield case has a partition protruding from a side surface of the shield case toward both sides of a gap between the predetermined resonant elements. It becomes the composition which becomes.

  According to the present invention, when there is variation in filter characteristics due to etching error of the pattern of the resonant element, it is possible to realize a high frequency filter that can adjust the strength of coupling between the resonant elements with one filter structure.

It is sectional drawing which shows the high frequency filter by this invention. It is a perspective view which shows the state which looked at the high frequency filter by this invention from the upper surface side. It is a figure which shows the filter characteristic before adjustment of the high frequency filter by this invention, and an adjustment state. FIG. 4 is a diagram illustrating filter characteristics before and after adjustment when the gap between the resonant elements in FIG. 3 is wider than a design value. FIG. 4 is a diagram illustrating filter characteristics before and after adjustment when a gap between resonant elements in FIG. 3 is narrower than a design value. It is a figure explaining the conventional superconducting filter, (a) is a perspective view which shows the state which abbreviate | omitted the shield case, (b) is sectional drawing which shows the state accommodated in the shield case. It is sectional drawing which shows the other conventional superconducting filter. It is a perspective view which shows the state which looked at the superconducting filter of FIG. 7 from the upper surface side.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The high-frequency filter according to the present invention is, for example, a band-pass filter that passes a predetermined frequency band, and is used in a high-frequency circuit mounted on a high-frequency device that handles high-frequency signals such as a microwave band and a millimeter wave band.

  As shown in FIGS. 1 and 2, the high frequency filter includes a substrate 100 in which a plurality of resonant elements 140a to 140d formed by microstrip lines are arranged at predetermined intervals, and shields electromagnetic waves from the outside surrounding the substrate 100. And a box-shaped metal shield case 200. The shield case 200 of the present embodiment is divided into two vertically.

  The substrate 100 is composed of a dielectric 110, a ground conductor 120 formed on the entire back surface of the dielectric 110, and an input line 130 composed of a microstrip line composed of a signal line formed on the surface of the dielectric 110, four lines. Resonating elements 140a to 140d and an output line 150 are provided. In the present embodiment, these microstrip line patterns are formed by etching a metal such as a copper foil as a half-wavelength side-coupled bandpass filter.

  As the high-frequency filter, a bandpass filter such as an interdigital bandpass filter or a hairpin bandpass filter may be formed in addition to the half-wavelength side-coupled bandpass filter. Further, the present invention can be applied not only to a band pass filter but also to a low pass filter and a high pass filter.

  The shield case 200 includes an input terminal 210 connected to the input line 130 and an output terminal 220 connected to the output line 150 so that a high-frequency signal can be input / output by the input terminal 210 and the output terminal 220. It has become.

  In addition, three conductor rods 300 to 320 are arranged on the ceiling surface of the shield case 200 so as to face the gap between the central resonant elements 140b and 140c. The conductor rods 300 to 320 are each provided with a thread groove so that the distance between the conductor rods 300 to 320 and the gap between the central resonant elements 140b and 140c can be adjusted.

  Further, partition portions 230 and 240 protrude from the side surface of the shield case 200 toward both sides of the gap between the central resonant elements 140b and 140c. Although details will be described later, the partitions 230 and 240 and the three conductor rods 300 to 320 weaken the coupling due to the spatial propagation of the high-frequency signal between the respective resonant elements 140a to 140d.

  In the present embodiment, the three conductor rods 300 to 320 are arranged on the gap between the central resonant elements 140b and 140c, and the partition portions 230 and 240 are arranged on both sides of the gap between the central resonant elements 140b and 140c. However, the present invention is not limited to this, and the three conductor rods 300 to 320 are arranged between the resonance elements 140a and 140b other than the center, or on the gap between the resonance elements 140c and 140d. 230 and 240 may be provided between the same resonance elements 140a and 140b, or on both sides of the gap between the resonance elements 140c and 140d, or may be provided in a plurality of gaps. Moreover, you may provide the conductor bars 300-320 and the partition parts 230 and 240 with respect to a separate gap.

  Next, a method for adjusting the filter characteristics of the high frequency filter described above will be described. In the case of a high-frequency filter such as a microwave band, the filter characteristics are affected only by the gap size between the resonant elements 140a to 140d slightly deviating from the design value, and the required filter characteristic (design value) cannot be obtained. . Therefore, when there is an etching error in the pattern of each of the resonant elements 140a to 140d of the microstrip line, an error occurs in the dimension of the gap between the resonant elements 140a to 140d, so that it is necessary to adjust the filter characteristics.

  In general, the filter characteristics of a high-frequency filter configured by arranging a plurality of resonant elements 140a to 140d by microstrip lines at a predetermined interval as in this embodiment are shown in the table before adjustment in FIG. When the gap between the elements 140a to 140d is wider than the designed value, the coupling between the resonant elements 140a to 140d is weakened so that the frequency band is narrowed and the resonant frequency is increased. It becomes impossible.

  At this time, as shown in the adjustment table of FIG. 3, the middle conductor rod 300 is lowered to bring the distance between the conductor rod 300 and the gap between the resonant elements 140b and 140c close to a predetermined distance, and the resonant elements 140b and 140c. By strengthening the coupling, the frequency bandwidth can be widened, the resonance frequency can be lowered, and the filter characteristics can be adjusted to the design values. When the distance between the conductor rod 300 and the gap between the resonant elements 140b and 140c becomes too close, the filter characteristics deteriorate due to an increase in passage loss, etc., but the resonant elements are separated at a predetermined distance where the filter characteristics do not deteriorate. The coupling between 140b and 140c can be adjusted to be strongest and weaker as the distance increases. FIG. 4 shows filter characteristics before and after adjustment in the case of excessive etching.

  On the other hand, as shown in the table before adjustment in FIG. 3, when the gap between the resonant elements 140a to 140d is narrower than the design value due to insufficient etching, the coupling between the resonant elements 140a to 140d is strengthened. Since the frequency band is wide and the resonance frequency is low, the filter characteristics as designed cannot be obtained in this case as well.

  At this time, as shown in the adjustment table of FIG. 3, the three conductor bars 300 to 320 are lowered. The three conductor rods 300 to 320 are arranged in parallel at a predetermined interval sufficiently shorter than the half wavelength λ / 2 of the wavelength λ of the high-frequency signal input / output from the input terminal 210 and the output terminal 220. Further, the distances between the conductor rod 310 and the partition portion 230 and between the conductor rod 320 and the partition portion 240 are set in the same manner as the distance between the conductor rods 310 to 320 described above. Since the high-frequency signal to be propagated in the waveguide mode in the shield case 200 has an electric field component parallel to the conductor rods 300 to 320 and the partition portions 230 and 240, the conductor rods 300 to 320 and the partition portion 230, Reflected by 240, propagation in the waveguide mode is suppressed.

  For example, in the case of a half wavelength of a 12 GHz high frequency signal of 12.5 mm and a half wavelength side coupled band-pass filter, each resonant element is considered in consideration of the wavelength shortening rate (for example, 0.6) due to the dielectric 110 of the substrate. The length of 140a to 140d is approximately 7.5 mm. Here, when the thickness of each of the three conductor rods 300 to 320 is 2 mm and arranged at equal intervals in parallel with the resonant elements 140b and 140c, each interval becomes 4.25 mm or less, and a half wavelength of a high frequency signal of 12 GHz. The interval is sufficiently shorter than 12.5 mm. If the distance between the three conductor rods 300 to 320 and the gap between the resonant elements 140b and 140c becomes too close, the filter characteristics deteriorate due to an increase in the passage loss, etc., but they are separated by a predetermined distance that does not deteriorate the filter characteristics. The coupling between the resonant elements 140b and 140c by spatial propagation at the position is weakest and can be adjusted strongly as the distance increases.

  Therefore, the distance between the conductor rods 300 to 320 arranged in parallel at a predetermined interval and the gap between the resonant elements 140b and 140c is adjusted, and the conductor rods 300 to 320 and the partition portions 230 and 240 cause spatial propagation. By suppressing the coupling between the resonant elements 140b and 140c and consequently weakening the coupling between the resonant elements 140b and 140c, the frequency bandwidth can be narrowed, the resonant frequency can be increased, and the filter characteristics can be adjusted to the design values. FIG. 5 shows filter characteristics before and after adjustment in the case of insufficient etching.

  Here, the horizontal ends of the respective partition portions 230 and 240 are prevented from reaching the gaps between the opposing resonant elements 140b and 140c. Thereby, the partition parts 230 and 240 do not have the function of strengthening the coupling between the resonant elements 140b and 140c, but only the function of suppressing the spatial propagation of the high-frequency signal in combination with the conductor rods 300 to 320.

  Therefore, according to the present embodiment, the necessary number of conductor rods 300 to 320 may be arranged at a predetermined interval in the range of the length of each of the resonance elements 140a to 140d, and the coupling between the resonance elements 140b and 140c is weakened. If the adjustment is made to reduce the spatial propagation of the high-frequency signal with the minimum number of conductor rods, and the adjustment is made to strengthen the coupling between the resonant elements 140b and 140c, the adjustment is made only with the conductor rod 300. The degree of freedom and width of adjustment can be realized at the same time. Further, depending on the filter characteristics, the conductor bar to be adjusted to strengthen the coupling between the resonant elements 140b and 140c may be either the conductor bar 310 or 320 instead of the conductor bar 300.

  It should be noted that adjustment to weaken the coupling between the resonant elements 140b and 140c is performed only on the conductor rods 300 to 320, depending on conditions such as the horizontal dimension of the shield case 200 of FIG. If possible, the partition portions 230 and 240 may be omitted. Moreover, you may arrange | position a conductor rod instead of the partition parts 230 and 240. FIG. In the present embodiment, the description has been given assuming that there are a plurality of resonant elements. However, one resonant element may be used depending on the required filter characteristics. Furthermore, in this embodiment, the conductor rods 300 to 320 are provided with screws for adjustment. However, the present invention is not limited to this as long as the conductor rods 300 to 320 can be moved up and down.

  According to the high-frequency filter according to the present invention described above, a substrate 100 configured by arranging a plurality of resonant elements (four resonant elements 140a to 140d) formed of microstrip lines at predetermined intervals, and a shield case surrounding the substrate 100 200, a plurality of conductor rods (three conductors) are provided on the shield case 200 so as to face a gap between predetermined resonance elements (gap between the resonance elements 140b and 140c) from the ceiling surface of the shield case 200. The rods 300 to 320) are arranged so that the distance between a plurality of conductor rods and a gap between predetermined resonance elements can be adjusted.

  The shield case 200 is characterized in that the partition portions 230 and 240 protrude from the side surface of the shield case 200 toward both sides of a gap between predetermined resonance elements (a gap between the resonance elements 140b and 140c).

  As a result, if there is an etching error in the pattern of each resonant element of the microstrip line and the filter characteristics vary, the strength of coupling between the resonant elements can be adjusted by one filter structure, and the filter characteristics can be adjusted to the design value. can do.

DESCRIPTION OF SYMBOLS 100 Substrate 110 Dielectric 120 Ground conductor 130 Input line 140a-140d Resonant element 150 Output line 200 Shield case 210 Input terminal 220 Output terminal 230, 240 Partition part 300-320 Conductor bar

Claims (2)

  In a high frequency filter having a substrate configured by arranging a plurality of resonant elements formed of microstrip lines at predetermined intervals, and a shield case surrounding the substrate, the predetermined resonant element from the ceiling surface of the shield case to the shield case A high frequency filter comprising: a plurality of conductor rods arranged so as to face a gap therebetween, and the distance between the plurality of conductor rods and a predetermined gap between the resonance elements can be adjusted.   2. The high-frequency filter according to claim 1, wherein the shield case has partitioning portions protruding from the side surface of the shield case toward both sides of a predetermined gap between the resonance elements.

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