JPS6230403A - Strip line filter - Google Patents

Abstract

PURPOSE:To easily obtain large electrostatic capacity and to produce products of high quality inexpensively by opposing a part of a transmission line to one end of strip line resonators in the thickness direction of a dielectric base plate to form a capacitor. CONSTITUTION:Strip lines 4a-4c are formed on cut parts 2 of the main surface 1b of the dielectric base plate 1 and strip lines 5a-5d and 6-8 are formed on the other main surface 1a. The lines 6-8 are opposed to an earth electrode 3 on the surface 1b side to form a strip resonator and their one ends 6a, 7a, 8a are opposed to the lines 4a-4c through the base plate 1. The opposed part forms a capacitor having electrostatic capacity to be fixed in accordance with the opposed area, the thickness of the base plate 1 and a dielectric constant and the resonators 6-8 are connected to the transmission line 10 through the capacitor. Consequently, large electric capacity can be easily obtained and a filter of which dispersion of characteristics is reduced can be inexpensively produced.

Description

[Detailed Description of the Invention] The present invention provides a filter using a stripline resonator,
In particular, it relates to a stripline filter with band rejection characteristics.

As shown in Figure 3, the filter with band rejection characteristics is constructed by connecting resonators X to the transmission line E through capacitors C at intervals of approximately A wavelength (λg/4). It has a circuit configuration.

A conventional example in which this filter is constructed of strip lines is shown in FIG. That is, the transmission line 43 is formed on the other main surface 41a of the dielectric substrate 41, which has the ground electrode 42 formed on the entire surface of one main surface 41b, and the transmission line 43 has approximately two wavelengths (λg/4). Strip lines 44 are formed at intervals via gaps G. This strip line 44 forms a resonator by opposing the ground electrode 42 on one main surface 41b. Hereinafter, a resonator constituted by a strip line and a ground electrode facing each other will be referred to as a strip line resonator.

The length of the strip line resonator 44 is approximately equal to the wavelength A, and one end is connected to a short-circuit electrode 45 formed on the lower surface of the substrate.
It is connected to the ground electrode 42 via. A gap G existing between the open circuit 44a of the stripline resonator 44 and the transmission line 43 constitutes a capacitor C in the equivalent circuit of FIG.

In recent years, a large capacitance has been required as the capacitor C, but the conventional filter has a -ha 44 of the transmission line 43 and the strip line resonator, as described above.
Since the capacitor C is formed by the gap G between the capacitor and the capacitor C, the following problem arises. In other words, to obtain a large capacitance, the gap G must be narrowed.
Since capacitance is inversely proportional to the gap distance, a small dimensional error can cause large fluctuations in capacitance, resulting in extremely large variations in manufacturing.In order to reduce variations, high manufacturing precision is required, which increases costs. cause the amplifier.

The present invention aims to provide useful means for solving the above problems.

. In order to achieve the above-mentioned object of reducing the oscillation rate by 7°, the stripline filter according to the present invention includes the capacitor in which a part of the transmission line and one end of the stripline resonator face each other in the thickness direction of the dielectric substrate. It is characterized by its structure.

If a portion of the transmission line and one end of the strip line resonator are configured to face each other in the thickness direction of the dielectric substrate as described above, the capacitance can be adjusted by changing the facing area. In this case, the capacitance is linearly proportional to the facing area, so to obtain a large capacitance, the facing area should be increased. If the opposing area is made large, even if there is some dimensional error, it will not affect the capacitance much. Therefore, it is possible to manufacture capacitors with little variation without requiring high manufacturing precision.

Figure 1 (A) is a front view of a stripline filter as an embodiment of the present invention, Figure (B) is a rear view, Figure (C) is a sectional view taken along the line A-A, and Figure (D) is a front view of a stripline filter as an embodiment of the present invention. BB cross-sectional views are shown, and in these figures, ■ is a dielectric substrate made of, for example, alumina ceramic, and on one main surface 1b, a ground electrode 3 is formed except for a rectangular cutout 2. has been done.

Strip lines 4a+4b and 4c, which become part of the transmission line, are formed in the cutout portions 2....

4 arranged linearly on the other main surface 1a of the substrate 1.
An open end 6a, ? between the strip lines 5a, 5b, 5c, 5d and each strip line 5a, 5b...?
a, position 8a, and the other end 6b.

Strip lines 6.7.8 extending from 7b and 8b to the edge of the substrate l are formed.

The former strip lines 5a to 5d have through holes 9 formed at one end and both ends, and the strip lines 4a, 4b, 5c on the one main surface lb side are connected through the through holes 9. are connected in series.

These amphibious surface stri-knob lines 4a, 4b, 4c,
5a to 5d constitute a transmission line 10.

The latter stripline 6.7.8 is on one main surface lb
A strip resonator is formed by facing the ground electrode 3 on the side. This strip line resonates! 6,7.
The length of 8 is the A wavelength, and one end (open end) 6a
,? a, 8a are strip lines 4a,
4b and 4c face each other. These opposing parts form a capacitor with a capacitance determined by the sum of the opposing surfaces, the thickness of the substrate 1, and the dielectric constant of the substrate 1, and the strip line resonators 6, 7.8 are connected to the transmission line 10 via this capacitor. Connected. The other ends 6b, 7b of the stripline resonator,
8b is connected to the ground electrode 3 via a shorting electrode 11 formed on the side surface of the substrate. The interval between adjacent stripline resonators 6, 7.8 is approximately equal to wavelength A. Note that the ground electrodes and strip lines 4a to 5a..., 6
, 7゜8 is a known method such as vapor deposition, sputtering, etc.
The pattern shown is formed on a dielectric substrate using a No. 1 formation technique.

According to the above configuration, the capacitor interposed between the transmission line and the stripline resonator is formed by making a part of the transmission line and one end of the stripline resonator face each other in the thickness direction of the substrate. As described in the section of operation, a large static gravity capacity can be easily obtained with little variation during manufacturing.

Next, FIG. 2 shows another embodiment of the present invention. In this embodiment, strip lines 6, 7.
8.10 is formed. Stripline 6.7.
8 constitutes a resonator, and 10 constitutes a transmission line. On the other hand, on the other main surface 1b, the ground electrode 3 is cut out 11a, llb, 11C in a portion facing the range including a part of the transmission line 10 and one ends 6a, 7a, 8a of the strip line resonator. Another isolated electrode 12... is formed. Each isolated electrode 12 is connected to the transmission line 10 via a through hole 13. One end 6a, 7a, 8a of the stripline resonator 6, 7.8 faces this isolated electrode 12, and is therefore connected to the transmission line 10 via a capacitor formed by this facing portion. In addition, in Figure 2, through hole E 3
was formed between the transmission line 10 and the isolated electrode 12, but one end 6a of the stripline resonator, ? a, 8a and isolated electrode! 2, the isolated electrode 12 becomes a part of the strip line resonator 6, 7.8, and the isolated 3χ electrode 12
A capacitor in a predetermined field can also be formed by the opposing portion of the transmission line 10 and the transmission line 10.

As explained above, according to the present invention, the capacitor that couples the stripline resonator to the transmission line has a structure in which one end of the stripline resonator and a part of the transmission line face each other in the thickness direction of the substrate. Since the capacitor is formed using a gap, it is easier to obtain a large capacitance compared to the conventional capacitor formed by a gap, and the influence of manufacturing errors on capacitance has not been large in the past, so the characteristics This has the excellent effect that a filter with little variation can be manufactured at low cost.

[Brief explanation of drawings]

i1 Figure (A) is a plan view of a stripline filter as an embodiment of the present invention, Figure (B) is a rear view, Figure (C) is a sectional view taken along line A-A in Figure (A), Figure (D) is is B- in figure (a)
A sectional view taken along the line B, FIG. 2(A) is a plan view of a stripline filter according to another embodiment of the present invention, and FIG.
Figure (c) is a sectional view taken along the line C-C in figure (a), Figure 3 is an equivalent circuit diagram of the present invention and the conventional stripline filter, and Figure 4 is
Figure (a) is a plan view of a conventional stripline filter.
Figure (b) is a sectional view taken along line D-D. ■...Dielectric substrates 4a, 4b, 4c, 12...Part of transmission line 6.7.
8... Stripline resonator 6a, ? a, 8a...
・One end, 10... Transmission line C... Capacitor Patent applicant Murata Manufacturing Co., Ltd. 11oIZ IIC11

Claims (1)

[Scope of Claim] A stripline filter in which a transmission line is formed on a dielectric substrate, and stripline resonators are connected to the transmission line via capacitors at approximately wavelength intervals, comprising: A stripline filter characterized in that a capacitor is formed with a structure in which a part of a transmission line and one end of a stripline resonator face each other in the thickness direction of a dielectric substrate.