JPS6137802B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a comb-line filter that is made smaller by filling it with a dielectric material.

First, a conventional combline filter will be explained. In FIG. 1, 1 to 5 are inner conductors, 6 is an outer conductor, 7 and 8 are coaxial terminals, 9 and 10 are center conductors of coaxial terminals 7 and 8, respectively, 11 is a dielectric, C ₁ ,
C ₂ and C ₃ are capacitors. In addition, FIG. 1b is a sectional view taken along line A-A in FIG.
C ₂ is the same as in Figure 1a.

The inner conductors 1 and 5 have one end connected to the outer conductor 6 and the other end connected to the center conductor 9 and 10, respectively, and operate as an impedance transformer. The inner conductors 2 to 4 have one end connected to the outer conductor 6, and the other ends to the outer conductor 6 via capacitors _C1 to _C3, respectively. The inner conductors 2 to 4, each of which is grounded at one end, serve as inductance when the length is 1/4 wavelength or less, and thus form a resonator together with the capacitors C ₁ to C ₃ connected thereto. At this time, the lengths of the inner conductors 2 to 4 are shortened by filling a dielectric between the inner conductors 1 to 5 and the outer conductor 6 to shorten the wavelength.
The comline filter can be made smaller.

Now, if the lengths of the inner conductors 2 to 4 are all the same and the capacitances of the capacitors C ₁ to _{C 3} are made equal, the inner conductors 2 to 4 all resonate at the same frequency o.
Therefore, the wave of frequency o incident on the coaxial terminal 7 sequentially passes through the inner conductor 2 to which capacitors C ₁ to _{C 3} are connected.
~4, it resonates and is taken out to the coaxial terminal 8. For frequencies other than frequency o, most of the power is reflected because the inner conductors 2 to 4 do not resonate. In this way, the combline filter shown in FIG. 1 has a function as a bandpass filter.

However, since conventional combline filters are filled with dielectric material, it is extremely difficult to finely adjust the amount of coupling by changing the spacing between adjacent inner conductors, making it difficult to obtain good filtering characteristics. There were flaws.

In order to eliminate these drawbacks, this invention uses a dielectric plate divided into two as the dielectric filling between the inner conductor and the outer conductor, and has a structure in which the inner conductor is sandwiched between the dielectric plates. A conductive plate is provided between adjacent inner conductors as a coupling amount adjusting element, and will be described in detail with reference to the drawings below.

FIG. 2 shows an embodiment of the present invention, and FIG.
is a sectional view taken along line B-B in FIG. In the diagram, 1~
10 is the same as in Figure 1, 11 is a dielectric plate, 12
is a rectangular thin conductor plate for adjusting the coupling amount, C ₁ ,
C ₂ and C ₃ are capacitors.

In FIG. 2, the inner conductors 1 to 5 are sandwiched between two dielectric plates 11 and embedded in grooves provided in the dielectric plates 11. Further, the conductor plate 12 is provided at the center between adjacent inner conductors, and the two dielectric plates 11
It is mechanically solidified by

Next, the function of the conductor plate 12 will be explained.

FIG. 3 shows the electromagnetic field distribution between adjacent inner conductors to explain the function of the conductor plate 12, and FIG. 3a shows an even symmetric mode, and FIG. 3 b shows an odd symmetric mode. In the figure, solid arrows indicate electric fields, and dashed arrows indicate magnetic fields. As shown in the figure, the conductor plate 12 has almost no effect on even symmetric modes, but increases the capacitance between the inner conductors in odd symmetric modes and lowers the characteristic impedance. Since the amount of coupling is proportional to the difference in characteristic impedance between both modes, the conductive plate 12 has the function of increasing the amount of coupling. In addition,
The degree of increase in the amount of coupling can be adjusted by adjusting the size of the conductive plate 12.

Therefore, the combline filter of the present invention is compact and allows easy adjustment of the coupling amount without impairing the function of the bandpass filter of the combline filter of FIG. This has the advantage that it is easy to obtain good filtering characteristics.

FIG. 4 shows another embodiment of the present invention.
This is a case in which a groove for embedding an inner conductor is not provided in one dielectric plate, and FIG. 4b is a sectional view taken along the line CC in FIG. 4a. The conductor plate 12 is provided at the center between adjacent inner conductors, and is fixed to the dielectric plate 11 using an adhesive. In this case as well, by providing the conductor plate 12, the amount of coupling can be easily adjusted without processing the dielectric plate 11 or changing the connection position between the outer conductor 6 and the inner conductors 1 to 5, resulting in a good result. This has the advantage that it is easy to obtain narrow wave characteristics.

In the embodiment, the case where the shape of the conductor plate 12 is rectangular has been described, but the present invention is not limited to this, and may be used in the case of a polygon such as a triangle or a convex shape, or an ellipse. Further, although the case where the number of stages of the filter is three has been described, the present invention is not limited to three stages.

As described above, the combline filter according to the present invention has a structure in which the inner conductor is sandwiched between two dielectric plates, and a conductive plate is provided between the inner conductors as a coupling amount adjusting element. This has the advantage that the amount of coupling can be easily adjusted and good filtering characteristics can be easily obtained.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of a conventional combline filter in which a dielectric is filled between the outer conductor and the inner conductor.
The figure is a schematic configuration diagram showing one embodiment of the present invention.
This figure shows the principle of operation of the conductor plate, and FIG. 4 is a schematic diagram showing another embodiment of the present invention. In the figure, 1 to 5 are inner conductors, 6 is an outer conductor, 7 and 8 are coaxial terminals, 9 and 10 are center conductors, 11 is a dielectric plate, 12 is a metal plate, and C ₁ , C ₂ , and C ₃ are capacitors. It is. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

Claims (1)

[Claims] 1 In a Comb-line filter in which a part or all of the space between the inner conductor and the outer conductor is filled with a dielectric, a dielectric plate divided into two is used as the dielectric, and the dielectric A combline filter having a structure in which the inner conductor is sandwiched between plates, and a conductor plate is provided between adjacent inner conductors.