JPS6230401A - Strip line filter - Google Patents

Abstract

PURPOSE:To obtain insertion loss and reflection loss making it possible to remove the influence of near-by frequency almost completely by forming the line width of U-shaped strip lines positioned on the I/O terminal sides differently from that of intermediate U-shaped strip lines. CONSTITUTION:The line width W1 of respective U-shaped arm parts 12 of the U-shaped strip lines 10L, 10R positioned on the I/O terminal sides out of the U-shaped strip lines 10L, 10, 10R is formed more narrowly than the line width W of other lines 10 formed on the intermediate position. A coupling interval l1 between each of the lines 10L, 10R and its adjacent line 10 is set up more narrowly than a coupling interval l2 among the three lines 10 formed on the center position. Namely, the line width W1 of the U-shaped arm parts 12 is made thinner than a calculated value without changing the effective length of the lines 10L, 10R and the line width W2 of curved parts 13 is made thicker the calculated value to change the LC component of the strip line formed by copper foil. Consequently, insertion loss and reflection loss making it possible to remove the influence of near-by frequency almost completely can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a stripline filter for frequencies in the gigahertz band.

(Prior art) Fig. 5 shows a strip line shown in Fig. 5 in which a full-scale electrode of silver or copper foil is formed on one surface of an electric substrate used as a conventional band-pass filter, and an etching process is performed on the other surface. forming a pattern.

The line pattern constituting this strip line filter is, for example, five U-shaped strip lines 10 as shown in the figure.
a, 10b, 10G, 10d, and 10e are arranged in sequence so that the U-shaped openings are in opposite directions.The wavelength used, the dielectric constant of the dielectric substrate, the thickness of the strip line, the line impedance, etc. All the strip lines 10a to 10e are formed to have the same line dimensions, with a line width (W>) calculated from the line width (W>) and an effective length (λ/2) based on the wavelength shortening rate.

(Problems to be Solved by the Invention) However, in the conventional strip line filter in which a plurality of U-shaped strip lines are arranged,
There is a limit to obtaining filter characteristics that provide a predetermined passband width, that is, sufficiently small insertion loss and sufficiently large reflection loss in the passband, and if left as is, the effects of local oscillation frequencies near the passband, etc. The problem was that it was easy to receive.

(Means for Solving the Problems) The present invention has been made in view of such conventional problems, and provides filter characteristics that can almost completely eliminate the influence of adjacent frequencies in the pass frequency band. That is, an object of the present invention is to provide a stripline filter having a stripline pattern in which appropriate insertion loss and reflection loss can be easily obtained.

In order to achieve this object, the present invention forms a full-surface electrode on one surface of a dielectric substrate, and a plurality of electrodes having a predetermined effective length and line width determined based on the wavelength used on the other surface. In a strip line filter consisting of U-shaped strip lines arranged in sequence so that the U-shaped openings are in opposite directions, the line width of the U-shaped strip lines located at the input and output ends is positioned in the middle. The width of the U-shaped strip line is different from that of other U-shaped strip lines. Specifically, the line width of the U-shaped arm part of the U-shaped strip line located at the input/output end is set in the middle. U-shaped strip
The width of the curved line is narrower than that of the curved line, and the width of the curved line is widened.

(Example) FIG. 1 is an explanatory diagram showing one embodiment of the present invention.

First, to explain the configuration, each of 10L and 10.10R is a U-shaped strip line formed by etching on one surface of a dielectric substrate such as glass epoxy or Teflon, and there are five U-axis strip lines. 101～
10R are sequentially arranged so that the U-shaped arm portions 12 are oriented in opposite directions. The U-shaped strip lines 10L and IOR located on both sides are formed integrally with input/output strip lines 14.15, and capacitor stubs 16 are provided on the input/output strip lines 14.15.

Here, the three U-shaped strip lines 10 formed between the U-shaped strip lines 10L and 1OR on both sides are calculated based on the wavelength used, the thickness of the silver or copper foil forming the strip lines, the line impedance, etc. The line width W and the effective length (λ/2) are based on the wavelength shortening rate, and both the U-shaped arm portion 12 and the bent portion 13 have the same line width W □.

On the other hand, the U-shaped strip line 10 located on both sides
Each of 1.10R is the track width W1 of the U-shaped arm portion 12.
is formed such that Wl<W is smaller than the track width W of the other strip line □ track 10 located between, and the track width W2 of the bent portion 13 is smaller than the track width W of the other strip line 10 located between □ From track width W
: It is formed with dimensions such that W2>W.

In addition, the strip lines 10L and 1 located on both sides
'U-shaped strip line 1 adjacent to each of the ORs
The coupling interval 11 between the three U-shaped strip lines 10 located at the center is set narrower than the coupling interval 12 between the three U-shaped strip lines 10 located at the center.

To summarize, the one U-shaped strip line 101.1OR located on both sides makes the line width W1 of the U-shaped arm part 12 thinner than the calculated value without changing its effective length (λ/2), and The line width W2 of No. 13 is made thicker than the calculated value, and the LC component of the strip line formed of copper foil is changed.

Next, the characteristics of the strip line filter of the present invention shown in the embodiment shown in FIG. 1 will be explained in comparison with the conventional example shown in FIG.

FIG. 2 is an electrical characteristic diagram showing the characteristics of a bandpass filter with a pass band of 3.7 GHz to 4.2 GHz for the conventional example shown in FIG. Measured data of insertion loss and return loss (VSWR) when all line widths W are the same is shown.

In the conventional example shown in Fig. 2, the insertion loss is 3°70H.
2 is -1,08dB, and 4.2GHz is -1°15dB, while the return loss is -17,32d at 3.7GHz.
B, 4.2G! -1z is -21.84dB.

FIG. 3 shows the line width of the U-shaped strip line 101.10R located on both sides of the U-shaped strip line 101. This shows the insertion loss and reflection loss when the width W1 is narrowed to W1 = (3/4)W and the line width W2 = (3/2>W) for the curved portion 13, and is compared to the conventional example in Fig. 2. In contrast, both insertion loss and reflection loss are improved in the passband of 3.7 GHz to 4.2 GHz.

A comparison of the insertion loss and reflection loss in the passbands of 3 and 7 to 4.2Gl-IZ shown in FIGS. 2 and 3 is as shown in Table 1 below.

From this measurement data, in contrast to the conventional example, in the embodiment shown in FIG.
The effects of improving insertion loss and reflection loss shown in Table 2 below can be obtained.

In the above embodiment, the line width of the U-shaped arm portions 12 of the U-shaped strip lines "IOL" and "IOR" located on both sides is made narrower than the calculated value W, and the line width W2 of the curved portion 13 is made narrower than the calculated value W. Although the case where the width is made wider than the calculated value W is taken as an example, in other embodiments, only the line width W1 is made narrower, or only the line width W2 is made wider. The effect of improving reflection loss can be obtained.

(Effects of the Invention) As described above, according to the present invention, in a strip line filter in which a plurality of U-shaped strip lines are sequentially arranged so that the U-shaped openings are in opposite directions, By making the line width of the U-shaped strip line located in the U-shaped strip line different from the line width of the other single-shaped strip line located in between, the LC component is changed. By simply performing an etching process to change the line width of the U-shaped strip line, it is possible to easily achieve appropriate filter characteristics with insertion loss and reflection loss that can almost completely prevent the effects of adjacent frequencies. .

[Brief Description of the Drawings] Fig. 1 is an explanatory diagram showing an embodiment of the present invention, Fig. 2 is a conventional filter characteristic diagram, Fig. 3 is a filter characteristic diagram of the present invention, and Fig. 4 is a conventional filter characteristic diagram. It is an explanatory diagram of an example. 10.101.10R: U-shaped strip line 12: U
Farm section 13: Bent section 14.15 strip line (for input/output) 16: Capacitance stub

Claims (3)

[Claims] (1) A full-surface electrode is formed on one surface of the dielectric substrate, and a plurality of U-shaped strip lines with a predetermined effective length and line width determined based on the wavelength used are formed on the other surface with a U-shaped opening. In a stripline filter in which the U-shaped striplines located at the input and output ends are sequentially arranged in opposite directions, A strip line filter characterized by having a line width different from the line width. (2) A patent characterized in that the U-shaped strip line located at the input/output end is formed so that the line width of the U-shaped arm portion is narrower than the line width of other U-shaped strip lines located in the middle. A stripline filter according to claim 1. (3) The U-shaped strip line located at the input/output end is formed so that the line width of the U-shaped arm portion is narrower than the line width of the other U-shaped strip line located in the middle,
2. The strip line filter according to claim 1, wherein the line width at the bent portion is wide.