JPS603201A - Strip line filter - Google Patents

Abstract

PURPOSE:To attain ease of connection between input/output electrodes and an external line and to decrease the characteristic impedance by windening the width of the input/output electrodes of a strip conductor within a permissible range of matching with the external line. CONSTITUTION:A strip conductor 2 is formed, which has a pattern comprising capacitance parts C1-C3 of broad width, inductance parts L1-L4 of narrow width, the input and output electrodes 4, 5 on one major plane of a dielectric substrate 1. An earth conductor 3 is formed on the other major plane of the substrate 1. In selecting a specific dielectric constant epsilonr of the substrate 1 as nearly 90 and the thickness as 2mm., the electrode width of the input electrode 4 and the output electrode 5 becomes nearly 0.2mm.. Thus, the characteristic impedance of the strip line filter is 40ohm and the impedance is lower than the characteristic impedance of an external line of the 50ohm system, but the width of the input/ output electrodes 4, 5 is as large as 0.2mm. and the connection with the external line is attained easily.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a strip line filter, and more particularly to an IJ tube line filter in which a low loss dielectric substrate is sandwiched between a strip conductor and a ground conductor.

(Prior Art) In general, a stripline filter has a well-known pattern on one main surface of a dielectric substrate corresponding to the characteristics of the filter. A ground conductor facing the strip conductor is formed on the surface, and a resonator formed by the strip conductor and the ground conductor, as well as inductance and capacitance, constitute a filter.

Conventionally, this type of stripline filter has had a characteristic impedance of 50 ohms in order to achieve matching with an external line connecting the stripline filter.

By the way, assuming that the characteristic impedance of the stripline filter is 50 ohms as mentioned above, for example, in a low-pass filter that has a cutoff region in the 700 MHz frequency band, the dielectric constant εr of the dielectric substrate is εr〉90. As a result, the widths of the input and output electrodes of the strip conductor became very thin, less than O11ηm, and it was difficult to connect these input and output electrodes to an external line by soldering or the like.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances regarding conventional strip line filters, and its object is to
By widening the input and output electrodes of the IJ tube conductor within the allowable range of matching with the external line, it is possible to easily connect the input and output electrodes to the external line, and to reduce the characteristic impedance. The object of the present invention is to obtain a stripline filter whose shape is more compact.

(Structure of the Invention) To summarize the present invention, on one main surface of a dielectric substrate,
A stripline filter comprising an IJ tube conductor and a ground conductor facing the strip conductor described in - on the main surface of a curved edge of a dielectric substrate, wherein the input electrode and the output electrode of the strip conductor are It is characterized in that the width is set wider than the width determined in accordance with the characteristic impedance of the external line to which the stripline filter is connected, within the allowable range of matching with the characteristic impedance.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 fa1. The stripline filter shown in plan and front views in Figure 1 (1) and Figure 1 (1), respectively, has a diameter of approximately 70 mm.
A low-pass filter having a cutoff band in the 0MHz frequency band, ] is a dielectric substrate, 2 is an IJ tube conductor,
3 is a ground conductor.

The dielectric substrate 1 is formed by forming a high-quality dielectric material into a rectangular plate shape, and one main surface thereof has wide capacitance portions C1, C2, and C3. A strip conductor 2 having a well-known pattern consisting of an inductance portion L t = L 2 , L 3 , L 4 , an input electrode 4 and an output electrode 5 is formed.

On the other main surface of the dielectric substrate 1, a ground conductor 3 is formed which faces the strip conductor 2 with the dielectric substrate 1 in between.

As shown in FIG. 2, the strip line filter has an inductance of inductance L1 to L4 of the strip conductor 2 between the input electrode 4 and the output electrode 5, and the inductance of the inductance of the strip conductor 2. C1
It has an equivalent circuit of a well-known low-pass filter in which capacitances C1 to C3 of fh to C3 are connected in a ladder shape.

In the stripline filter having the above-described configuration, the relative permittivity εr of the dielectric substrate 1 is set to εr÷90.
, ) When the voltage is 2 t,ryB, the width of the input electrode 4 and the output electrode 5 is approximately 0.2 tn.

In the above manner, the characteristic impedance ZQ of the strip line filter becomes lower than the characteristic impedance of the external line of the 50 ohm system, where Z0=i=40 ohms and rλ, but the input electrode 4 and the output electrode 5 of [1
] is as large as 0.2 yrm, making it easy to connect to external lines. In addition, in the case of 2140 ohms, the lengths of the capacitance portions C1 to C3 and the inductance portions to L4 of the strip conductor 2 are 1 bit shorter than when ZO = 50 ohms, and the strip line filter The shape can be made smaller.

By the way, as mentioned above, when the characteristic impedance ZQ of the stripline filter is set to z□=-4o ohm, and when the above stripline filter is connected to an external line of 50 ohm system, the input chamber (to 4, output electrode 5 The standing wave ratio (VSWR) at the contact with the external line and the reading point is approximately 1.25, but in practical terms, when constructing an IJ tube line filter with a standing wave ratio of approximately 2.0, No problem.

Next, the plane (2
) and a front view of the stripline filter shown in FIG. 1(al, %) and FIG. 1(b). I-5
, and a capacitance part C2 and an inductance part L
2-1-3, an inductance section L6 is formed between the capacitance section C3 and the inductance section L6.
An inductance portion L7 is formed between a and L4, and it is a low-pass filter having an equivalent circuit as shown in FIG.

(S) Even in a stripline filter in which the IJ conductor 2 has a pattern as described above, the upper half of the dielectric substrate 1 ε1 is set to εr 90. When the thickness is 2 mm, the input type (electrode 4 and output electrode 5 (return width is 0.2; am
By setting, the characteristic impedance Zo becomes Z□
It becomes 140 ohms, ta+ in Fig. 1 and Fig. 1 (1)
) can achieve the same effect as the string line filter.

The present invention can be applied not only to IJ line filters having low-pass characteristics but also to strip-line filters having bypass characteristics or band-pass characteristics.

(Effects of the Invention) -1 As is clear from the detailed description, the present invention provides a strip line filter in which the widths of the input electrode and output electrode of the strip conductor are widened within an allowable range. Since the input type (7) and output electrodes can be easily connected to external lines, it is easy to incorporate the stripline filter into other circuits or cases. It can also be made smaller.

[Brief explanation of the drawing]

FIG. 1(al) and FIG. 1[1(bl are respectively a plan view and a front view of an embodiment of the stripline filter according to the present invention, FIG. 2 is a stripline filter of FIG. 1ta+ and FIG. 1(bl). An equivalent circuit diagram of FIG. 3(a) and FIG.
The figure is an equivalent circuit diagram of the strip line filter in FIGS. 3(a) and 3(bl). 1... Dielectric substrate, 2... Strip conductor, 3...
...Earth conductor, 4...Input electrode, 5...Output electrode. Patent applicant Murata Manufacturing Co., Ltd.

Claims (1)

[Claims] (1) A strip line filter in which a strip conductor is formed on one main surface of a dielectric substrate, and a ground conductor facing the strip conductor is formed on the main surface of the dielectric substrate as viewed from above, comprising: F, the width of the input and output electrodes of the +7 conductor should be within the permissible range for matching with the characteristic impedance of the external line connecting the stripline filter, rather than the width determined in accordance with the characteristic impedance of the external line connecting the stripline filter. A strip characterized by a wide setting. line filter.