JP2869913B2 - Stripline filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strip line filter used in a communication circuit or the like.

[0002]

2. Description of the Related Art As shown in FIG. 9, a conventional stripline filter 49 has input / output terminal electrodes 50 and 51 provided on left and right end faces, respectively, and grounds are provided on front and back end faces, respectively. Terminal electrodes 52 and 53 were provided. The ground terminal electrodes 52 and 53 are connected to the filter 4
9 and a common ground electrode provided on the bottom surface of the filter 49. The electrode has a wide area enough to cover the front and rear end surfaces substantially entirely. there were. This stripline filter 49
Are surface-mounted on the printed wiring board 55. That is, the input / output terminal electrode 51 and the ground terminal electrode 52 are electrically connected to and fixed to the circuit conductors 56 and 57 provided on the surface of the printed wiring board 55 by the solders 60 and 61, respectively. The input / output terminal electrode 50 and the ground terminal electrode 53 also
Similarly, they are electrically connected and fixed by solder to circuit conductors provided on the surface of the printed wiring board 55, respectively.

On the other hand, this strip line filter 49
Is used in the high frequency band, the ground terminal electrode 52,
53 generates a residual inductance. The value of this residual inductance varies depending on the amount of the solder 61 and the spread area of the solder 61. Since the ground terminal electrodes 52 and 53 are wide-area electrodes, the amount of the solder 61 and the spread area of the solder 61 greatly vary. Therefore, the conventional stripline filter 49 has a problem that the value of the residual inductance generated in the ground terminal electrodes 52 and 53 fluctuates greatly, causing a large variation in filter characteristics.

An object of the present invention is to provide a strip line filter in which a variation in residual inductance generated in a ground terminal electrode is small.

[0005]

In order to solve the above problems, a strip line filter according to the present invention comprises:
Each strip line of the resonator is
Facing the command electrode, ground external terminal electrodes provided on the end surface of the stripline filter, disposed in between the Mashimashi and solder mounting portion extending from the soldering portion and the soldering portion
Is composed of a two arm portions which are common ground electrode of the resonator to the soldering portion is electrically connected to said arm portion
One end of the resonator of the strip lines to each of which is characterized in that are electrically connected.

In the above arrangement, the ground external terminal electrode is provided between the soldering portion and the soldering portion.
When the strip line filter is constituted by two arms and the surface of the strip line filter is mounted on a printed circuit board or the like, the soldered portion of the ground external terminal electrode is soldered to a circuit conductor provided on the surface of the printed wiring board. At this time, solder for mounting does not adhere to the arm of the ground external terminal electrode. The ground external terminal electrodes by the electrode width of the soldering portion to a predetermined value,
The electrode area is reduced. Therefore, the amount of solder and the spread area of the solder are smaller than those of the conventional filter. Also,
The value of the residual inductance generated in the ground external terminal electrodes, since there is no solder attachment for mounting the arm portion is determined by the distance from the common ground electrode up to the stripline through the ground external terminal electrodes.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a strip line filter according to the present invention will be described below with reference to the accompanying drawings. [First Embodiment, FIGS. 1 to 5] The first embodiment is a microstrip line filter having two resonators on a dielectric substrate, and a description will be given of a filter functioning as a bandpass filter.

As shown in FIG. 1, a pair of strip lines 2 and 3 are formed on the upper surface of a dielectric substrate 1. The lead portion 2a of the strip line 2 is exposed at the left edge of the dielectric substrate 1, and the lead portion 2b is exposed at a position on the left side of the front edge of the dielectric substrate 1. The lead portion 3a of the strip line 3 is exposed at the right edge of the dielectric substrate 1, and the lead portion 3b is exposed at a position on the right side of the front edge of the dielectric substrate 1. A common ground electrode 4 is formed on substantially the entire lower surface of the dielectric substrate 1. The lead portions 4a and 4b of the common ground electrode 4 are exposed at the center of the front edge and the rear edge of the dielectric substrate 1, respectively. The strip lines 2 and 3 and the common ground electrode 4 are made of, for example, Ag or Cu.
May be applied by a printing method and dried, or may be formed by a thin film method such as sputtering or photolithography. On the upper surface of the dielectric substrate 1,
The dielectric substrate 6 is integrally attached with an adhesive to form a strip line filter 15.

As shown in FIG. 2, the strip line filter 15 has an input / output terminal electrode 7 which is electrically connected to the lead 2a of the strip line 2 on the left end face.
Is provided. Similarly, an input / output terminal electrode 8 is provided on the right end face portion while being electrically connected to the lead portion 3a of the strip line 3. A ground terminal electrode 10 is provided on an end surface on the near side. The ground terminal electrode 10 includes a soldered portion 10a and arms 10b and 10c extending from both sides of the soldered portion 10a. The electrode width of the arms 10b and 10c is
It is designed to have a dimension smaller than the electrode width of 0a, so that the solder does not easily spread to the arms 10b and 10c during soldering. The arm part 10b is electrically connected to the lead part 2b of the strip line 2. Soldering part 10a
Are electrically connected to the lead portion 4a of the common ground electrode 4. The arm part 10c is a lead part 3b of the strip line 3.
Is electrically connected to Further, a ground terminal electrode 13 is provided at the center of the rear end surface in a state of being electrically connected to the lead portion 4b of the common ground electrode 4. Therefore, the strip lines 2 and 3 are electrically connected to the common ground electrode 4 via the ground terminal electrode 10.
The terminal electrodes 7, 8, 10, 13 are made of, for example, Ag or Ag-P
The paste such as d may be formed by applying and drying by a printing method, or may be formed by using a thin film method such as sputtering or photolithography. When the thin film method is adopted,
It is possible to form electrodes with higher precision, and the amount of solder and the spread area of the solder at the time of soldering become smaller.

The strip line filter 15 thus obtained is, for example, as shown in FIG.
Used for surface mounting. That is, the input / output terminal electrode 8 and the ground terminal electrode 10 are soldered to the circuit conductors 21 and 22 provided on the surface of the printed wiring board 20, respectively.
4, 26, and are electrically connected and fixed.
In particular, the solder 26 for this mounting adheres to the soldering portion 10a of the ground terminal electrode 10, but the arm portions 10b, 1
The solder 26 does not adhere to 0c. Input / output terminal electrode 7
Similarly, the ground terminal electrodes 13 are also electrically connected to circuit conductors provided on the surface of the printed wiring board 20 by soldering and fixed.

The soldering portion 10a of the ground terminal electrode 10
Since the electrode has a small electrode area, the variation in the amount of the solder 26 and the spread area of the solder 26 is smaller than in the conventional filter. Further, since no solder is attached to the arms 10b and 10c for mounting, a residual inductance determined by the distance from the common ground electrode 4 to the strip lines 2 and 3 via the ground terminal electrode 10 occurs. I do.
Therefore, the value of the residual inductance can be easily predicted at the time of designing, and this residual inductance can be taken in as a circuit component when designing a filter.

FIG. 4 is an equivalent electric circuit diagram of the strip line filter 15. The inductance L1 of the strip line 2 and the capacitance C1 formed between the strip line 2 and the common ground electrode 4 constitute one resonator, and the inductance L2 of the strip line 3 and the inductance of the strip line 3 and the common ground electrode 4 The capacitance C2 formed therebetween constitutes the other resonator. The two resonators are electrically coupled by a mutual inductance M. L3 and L4 are the strip lines 2 and 3 from the common ground electrode 4 via the ground terminal electrode 10.
Is the residual inductance determined by the dimensions up to.

FIG. 5 is a band characteristic diagram of the strip line filter 15 having the above configuration. In the figure, solid line A
1 and A3 are each in a reference state (1.2 mm on a circuit conductor of the printed wiring board 20 using a mask having a thickness of 0.10 mm).
(A state where the solder paste is applied to an area of 1.5 mm and the filter 15 is soldered.) The attenuation and insertion loss of the filter 15 are shown. The solid line A2 indicates a comparative state (a thick paste of solder paste is applied to an area of 1.2 mm × 1.5 mm on the circuit conductor of the printed wiring board 20 using a 0.35 mm thick mask, and then the filter 15 is soldered. The state (attenuation) of the filter 15 is displayed. For comparison, the band characteristics of a conventional filter having a large ground terminal electrode are also indicated by dotted lines B1, B2, and B3. Dotted line B
Reference numerals 1 and B3 indicate the attenuation and insertion loss of the filter in the reference state, respectively, and the dotted line B2 indicates the attenuation of the filter in the comparison state. Based on FIG. 5, Table 1 shown below is obtained. Table 1 shows the difference between the filter characteristic in the comparison state and the filter characteristic in the reference state.

[0014]

[Table 1]

In the filter 15 of the first embodiment, the poles a and b located on both sides of the pass band have a difference of 15 to 2 due to a difference in the amount of solder.
Only 0 MHz (1.5 to 2.5 in attenuation)
dB difference). On the other hand, in the filter of the conventional example, the poles a and b located on both sides of the pass band are shifted by 40 to 50 MHz (a difference of 3.5 to 5.0 dB in attenuation). Therefore,
The filter 15 of the first embodiment can suppress the variation in the filter characteristics to about 40% of the conventional filter.

[Second Embodiment, FIGS. 6 and 7] As shown in FIG. 6, the strip line filter 31 of the second embodiment has a dielectric green sheet 32 having a pair of strip lines 35 and 36 provided on the surface. And a dielectric green sheet 33 provided with a common ground electrode 37 on the surface and a dielectric green sheet 34, stacked, pressed, fired and integrated.

The lead portion 35a of the strip line 35 is exposed at the left edge of the dielectric green sheet 32, and the lead portion 35b is exposed at a position on the left side of the front edge of the dielectric green sheet 32. The lead portion 36a of the strip line 36 is exposed at the right edge of the dielectric green sheet 32, and the lead portion 36b is exposed at a position on the right side of the front edge of the dielectric green sheet 32. The lead portions 37a, 37b, and 37c of the common ground electrode 37 are exposed at the left, center, and right positions of the front edge of the dielectric green sheet 33, respectively. Further, the leading portions 37d, 37e, 3 of the common ground electrode 4
7f are exposed at the left, center, and right positions of the rear edge of the dielectric green sheet 33, respectively.

As shown in FIG. 7, the integrated strip line filter 31 has a strip line 3 on its left end face.
The input / output terminal electrode 39 is provided in a state of being electrically connected to the fifth lead portion 35a. Similarly, an input / output terminal electrode 40 is provided on the right end face in a state of being electrically connected to the lead portion 36a of the strip line 36.
A ground terminal electrode 42 is provided on the end surface on the near side. The ground terminal electrode 42 has a soldered portion 42a and arms 42b extending from both sides of the soldered portion 42a.
42c. The arm portion 42b is electrically connected to the lead portion 35b of the strip line 35 and the lead portion 37a of the common ground electrode 37. Soldering part 4
2a is electrically connected to the leading portion 37b of the common ground electrode 37a. The arm part 42c is electrically connected to the lead part 36b of the strip line 36 and the lead part 37c of the common ground electrode 37. Further, the drawing portion 37 of the common ground electrode 37
d, a ground terminal electrode 44 is provided in a state where it is electrically connected, a central position is provided with a ground terminal electrode 45 in a state where it is electrically connected to the lead portion 37e, and a lead portion is provided in a position closer to the right. The ground terminal electrode 46 is provided so as to be electrically connected to 37f. Therefore, the strip lines 35 and 36 are respectively connected to the ground terminal electrodes 4.
2 and is electrically connected to the common ground electrode 37 via the second electrode 2.

The strip line filter 31 having the above-described configuration operates similarly to the filter 15 of the first embodiment.
It works. [Other Embodiments] The strip line filter according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the gist.

The shape of the ground terminal electrode having the arm portion is as follows.
Various modifications are made to meet the specifications of the stripline filter. For example, as shown in FIG. 8, the ground terminal electrode 10 of the filter 15 described in the first embodiment may be a T-shaped ground terminal electrode 48 having a soldered portion 48a and arms 48b and 48c. Good. Alternatively, the surface of the arm of the ground terminal electrode may be coated with an insulating material so that solder for mounting does not reliably adhere to the arm.

[0021]

As is apparent from the above description, according to the present invention, the ground external terminal electrode is connected to the soldering portion and the soldering portion.
When the strip line filter is surface-mounted on a printed wiring board, etc., the soldered part of the ground external terminal electrode should be attached to the surface of the printed wiring board. Are electrically connected and fixed by soldering to the circuit conductor provided in the above. Since the soldered portion has a small electrode area, the amount of solder and the spread area of the solder can be reduced as compared with a conventional filter. Since this filter is the arm of the ground external terminal electrode does not adhere to the solder for mounting, ground out from the common ground electrode
Residual inductance value determined by the distance up to the stripline through the Department terminal electrode is obtained. Based on the above results, a strip line filter with little variation in the residual inductance generated in the ground external terminal electrode can be obtained.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a stripline filter according to the present invention.
FIG. 2 is an assembled perspective view showing the embodiment.

FIG. 2 is a perspective view showing an appearance of the strip line filter shown in FIG.

3 is a perspective view showing a state where the strip line filter shown in FIG. 2 is surface-mounted on a printed wiring board.

FIG. 4 is an equivalent electric circuit diagram of the strip line filter shown in FIG. 2;

FIG. 5 is a graph showing band characteristics of a strip line filter after surface mounting.

FIG. 6 shows a second example of the stripline filter according to the present invention.
FIG. 2 is an assembled perspective view showing the embodiment.

FIG. 7 is an exemplary perspective view showing the appearance of the stripline filter shown in FIG. 6;

FIG. 8 is a perspective view showing another embodiment.

FIG. 9 is a perspective view showing a conventional example.

[Explanation of symbols]

 1, 6 dielectric substrate 2, 3 strip line 4 common ground electrode 10 ground terminal electrode 10a soldered portion 10b, 10c arm 15 strip line filter 31 strip line filter 32, 33, 34 Dielectric sheets 35, 36 Strip line 37 Common ground electrode 42 Ground terminal electrode 42a Soldering parts 42b, 42c Arm 15 'Stripline filter 48 Ground terminal electrode 48a Soldering parts 48b, 48c Arm

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-284003 (JP, A) JP-A-4-306003 (JP, A) JP-A-63-13000 (JP, A) 9201 (JP, U) 1-81004 (JP, U) (58) Fields surveyed (Int. Cl. ⁶ , DB name) H01P 1/203 H01P 1/205

Claims (1)

(57) [Claims] 1. A stripline filter comprising at least two resonators, wherein each of the resonators has a stripline .
Opposed to the common ground electrode, the ground external terminal electrodes provided on the end face of the stripline filter, extends from the soldering part and the soldering portion and the solder mounting portion
Is composed of a two arms disposed in between, a common ground electrode of the resonator to the soldering portion is electrically connected to strip line of the resonator in each of the arms
Wherein one end of the strip line filter is electrically connected.