JPH11163602A - Distribution constant line type filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter which increases attenuation quantity in a rejection band. SOLUTION: This filter 10 arranges micro strip line resonators 3 and 4 which are distribution constant line type resonators with one end being an open terminal and the other end connected to a 1st ground electrode 2 to be a ground terminal side by side, making the linear parts of the ground terminals adjacent as a column type and provides an input electrode 5 and an output electrode 6 by performing capacitive coupling between open terminals of the resonators 3 and 4 through a pair of comb-shaped electrodes 7 and 8 that consist of two comb-shaped electrodes which engage and face each other. In such a case, a 2nd ground electrode 11 is provided adjacently to the electrodes 5 and 6 through gaps 12 and 13. Thus, ground capacity is formed in the part of the gaps 12 and 13 between the electrodes 5 and 6 and the electrode 11 and this increases attenuation quantity in a rejection band.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed line filter, and more particularly to a distributed line filter used in an RF stage of a mobile communication device.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a conventional distributed constant line type filter. In FIG. 7, a distributed constant line type filter 1
Is a distributed constant line resonator whose length is about one-fourth of the wavelength of the target frequency, one end is an open end, and the other end is connected to the first ground electrode 2 to serve as a ground end. It comprises stripline resonators 3 and 4, an input electrode 5 and an output electrode 6.

Here, the two microstrip line resonators 3 and 4 are bent in a meandering shape, and are arranged close to each other so as to connect the linear portions on the ground end side connected to the ground end 2 to each other. Each open end is connected to the input electrode 5 and the output electrode 6 via two comb-shaped electrode pairs 7 and 8 which are in mesh with each other and face each other. The input electrode 5 and the output electrode 6 are also connected via a comb-shaped electrode pair 9 composed of two opposing comb-shaped electrodes which are also meshed with each other. Distributed line filter 1 is formed on the surface of a dielectric substrate having a ground electrode formed on the entire back surface, for example, and input electrode 5 and output electrode 6 are connected to an external circuit by wire bonding, for example.

In the distributed-constant-line filter 1 configured as described above, the signal input from the input electrode 5 passes through the microstrip line resonators 3 and 4 via the attenuation pole capacitance formed by the comb-shaped electrode pair 7. , And resonates only in the vicinity of the target frequency, and signals of other frequencies are reflected. The signal resonated by the resonance circuit composed of the microstrip line resonators 3 and 4 is output from the output electrode 6 via the capacitance formed by the comb-shaped electrode pair 8. In this way, the distributed constant line filter 1 operates as a band-pass filter.

FIG. 8 shows the transmission characteristic of the distributed constant line type filter 1. In FIG. 8, a characteristic x indicates an insertion loss, and indicates a band-pass characteristic in which the insertion loss is reduced in a pass band a around about 2 GHz. The portion where the insertion loss is large at the frequencies on both sides of the passband a is due to the attenuation pole capacitance formed by the comb-shaped electrode pair 9 in FIG.

[0006]

However, in the above-mentioned distributed constant line type filter 1, as shown in FIG. 8, in the stop band b on both sides of the pass band a, the amount of attenuation is only about 18 dB and sufficient attenuation is obtained. There was a problem that characteristics could not be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a distributed constant line type filter having a large attenuation in a stop band.

[0008]

To achieve the above object, a distributed constant line type filter according to the present invention comprises a plurality of filters each having one open end and the other end connected to a first ground electrode to form a ground end. Are arranged at least partially in close proximity to each other, and are provided with an input electrode and an output electrode by capacitively coupling with each open end of the distributed constant line resonator located at both ends. In the comb-line type distributed constant line type filter configured as described above, a second ground electrode is provided by being capacitively coupled between the input electrode and the output electrode.

The distributed constant line type filter according to the present invention is characterized in that the second ground electrode, the input electrode and the output electrode are arranged close to each other.

Further, in the distributed constant line type filter according to the present invention, the second ground electrode, the input electrode, and the output electrode may be connected to each other via a comb-shaped electrode pair including two comb-shaped electrodes which mesh with each other and face each other. It is characterized by being arranged.

In the distributed constant line type filter according to the present invention, the second ground electrode, the input electrode, and the output electrode may be overlapped with each other with an insulator interposed therebetween.
It is characterized by being arranged via an MIM electrode pair consisting of two planar electrodes.

With such a configuration, in the distributed constant filter according to the present invention, the amount of attenuation in the stop band can be increased.

[0013]

FIG. 1 shows an embodiment of a distributed constant line type filter according to the present invention. In FIG. 1, the same or equivalent parts as those in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 1, the distributed constant line type filter 10 is a second type.
One end 11 of the second ground electrode 11
“a” protrudes toward the input electrode 5 and is disposed close to the input electrode 5 via the gap 12. The other end 11 b of the second ground electrode 11 protrudes toward the output electrode 6 and is arranged close to the output electrode 6 via the gap 13. Thus, by providing the second ground electrode 11 close to the input electrode 5 and the output electrode 6, a ground capacitance is formed between the two.

FIG. 2 shows the transmission characteristics of the distributed constant line type filter 10. FIG. 2 shows the insertion loss, and the same or equivalent parts as those in FIG. 8 are denoted by the same reference numerals and description thereof will be omitted.

In FIG. 2, the characteristic x indicates the insertion loss of the conventional distributed constant line type filter 1, and the characteristic y indicates the insertion loss of the distributed constant line type filter 10 of the present invention. As can be seen by comparing the characteristic x and the characteristic y, while the passband a shows almost the same characteristic, the characteristic y has an attenuation of about 28 dB in the stop band b. About 10 dB higher.

As described above, the input electrode 5 and the output electrode 6
By providing the second ground electrode 11 in close proximity to and forming a ground capacitance between them, the amount of attenuation in the stop band b can be improved.

In FIG. 1, the second ground electrode 11 is formed so as to be close to the input electrode 5 and the output electrode 6 only at its one end 11a and the other end 11b to form a ground capacitance. As shown in the constant line filter 20, the second ground electrode 21 may be formed in a substantially rectangular shape, and the whole may be formed close to the input electrode 5 and the output electrode 6. In this case, the capacitance between the input electrode 5 and the output electrode 6 and the second ground electrode 21 can be increased, and the attenuation of the stop band b can be further increased. In FIG. 3, the same or equivalent parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

In FIG. 1, the input electrode 5 and the output electrode 6 are connected via an attenuation pole capacitance formed by a comb-shaped electrode pair 9 composed of two opposing comb-shaped electrodes. , The distributed constant line type filter 3 shown in FIG.
As shown in FIG. 0, the portion connecting the input electrode 5 and the output electrode 6 may be eliminated to eliminate the attenuation pole capacitance. In this case, the same operation and effect as in FIG. In FIG. 4, the same or equivalent parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

FIG. 5 shows still another embodiment of the distributed constant line type filter of the present invention. In FIG. 5, the same or equivalent parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 5, the second line of the distributed constant line type filter 40 is shown.
One end 11a of the ground electrode 11 protruding toward the input electrode 5 and the input electrode 5 are connected via a comb-shaped electrode pair 41 composed of two opposing comb-shaped electrodes which mesh with each other. The other end 11b of the second ground electrode 11 protruding toward the output electrode 6 is connected to the output electrode 6 via a comb-shaped electrode pair 42 composed of two opposing comb-shaped electrodes.

Thus, the input electrode 5 and the output electrode 6
By connecting the second ground electrode 11 and the second ground electrode 11 via the comb-shaped electrode pairs 41 and 42, a ground capacitance is formed between the two and the same operation and effect as in FIG. 1 can be obtained. In this case, since the ground capacitance can be increased in the comb-shaped electrode pair having a small area as in the case of the distributed constant line type filter 20 in FIG. 3, the attenuation of the stop band can be increased or the second ground electrode can be reduced. The size can be reduced.

FIG. 6 shows still another embodiment of the distributed constant line type filter of the present invention. 6, the same or equivalent parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 6, the distributed constant line type filter 50
One end 11a of the ground electrode 11 protruding toward the input electrode 5 and the input electrode 5 are connected via an MIM electrode pair 51 composed of two planar electrodes stacked with an insulator 51a interposed therebetween. The output electrode 6 of the second ground electrode 11
The other end 11b protruding to the side is connected to the output electrode 6 and the insulator 5 therebetween.
M composed of two planar electrodes superimposed on both sides of 2a
They are connected via the IM electrode pair 52. Where MI
M is an abbreviation of Metal Insulator Metal, and represents a structure in which one metal layer sandwiches one insulating layer to form a capacitor. Further, since the ground capacitance can be increased as in the case of the distributed constant line type filter 40 of FIG. 5, the attenuation of the stop band can be increased, and the size of the second ground electrode can be reduced.

As described above, the input electrode 5 and the output electrode 6
And the second ground electrode 11 are connected via the MIM electrode pairs 51 and 52, respectively, whereby a ground capacitance is formed between them and the same operation and effect as in FIG. 1 can be obtained.

In each of the above embodiments, the distributed constant line type filter is constituted by using two distributed constant line type resonators, that is, the microstrip line type resonators. Is not limited to two, and may be configured using three or more microstrip line resonators. Further, in each of the above embodiments, the microstrip line resonator is bent in a meandering shape, but this may be another shape such as a linear shape or a spiral shape.
Further, in each of the above embodiments, the microstrip line resonator is used as the distributed constant line type resonator, but this may be another distributed constant line type resonator such as a strip resonator.

[0024]

According to the distributed constant line type filter of the present invention, at least one distributed constant line type resonator having one open end and the other end connected to the first ground electrode to serve as a ground end is provided. A comb-line type distributed-constant-line-type filter in which an input electrode and an output electrode are provided by disposing a part thereof close to each other and capacitively coupling between the open-ended ends of the distributed-constant-line-type resonators at both ends thereof, By providing the second ground electrode by capacitively coupling the input electrode and the output electrode, the attenuation in the stop band can be improved. Further, the capacitance between the input electrode and the output electrode and the second ground electrode is changed to a comb-shaped electrode pair consisting of two comb-shaped electrodes which are in mesh with each other and two plane-shaped electrodes stacked with an insulator interposed therebetween. By forming the MIM electrode pair including electrodes, it is possible to increase the amount of attenuation in the stop band and to reduce the size of the second ground electrode.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a distributed constant line filter according to the present invention.

FIG. 2 is a diagram showing a transmission characteristic of a distributed constant line type filter of the present invention.

FIG. 3 is a diagram showing the configuration of another embodiment of the distributed constant line filter of the present invention.

FIG. 4 is a diagram showing the configuration of yet another embodiment of the distributed constant line filter of the present invention.

FIG. 5 is a diagram showing a configuration of still another embodiment of the distributed constant line filter of the present invention.

FIG. 6 is a diagram showing a configuration of a distributed constant line type filter according to yet another embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a conventional distributed constant line type filter.

FIG. 8 is a diagram showing pass characteristics of a conventional distributed constant line filter.

[Explanation of symbols]

 2 First ground electrode 3, 4 Microstrip line resonator 5 Input electrode 6 Output electrode 7, 8, 9 Comb electrode pair 10 Distributed line filter 11 Second ground electrode 11a Second One end of the ground electrode 11b 11b ... The other end of the second ground electrode 12, 13 ... Gap

Claims (4)

[Claims] 1. A plurality of distributed-constant-line-type resonators, one end of which is an open end and the other end of which is connected to a first ground electrode and serves as a ground end, are arranged at least partially in close proximity to each other, In a comb-line type distributed constant line type filter configured by providing an input electrode and an output electrode by capacitively coupling between each open end of the distributed constant line type resonator and the input electrode and the output electrode, Characterized in that a second grounding electrode is provided by capacitively coupling between the two. 2. The distributed constant line filter according to claim 1, wherein the second ground electrode, the input electrode, and the output electrode are arranged close to each other. 3. The second ground electrode, the input electrode, and the output electrode are opposed to each other by meshing with each other.
The distributed constant line type filter according to claim 1, wherein the filter is arranged via a comb-shaped electrode pair including two comb-shaped electrodes. 4. The method according to claim 1, wherein the second ground electrode, the input electrode, and the output electrode are arranged via an MIM electrode pair including two planar electrodes that are overlapped with an insulator interposed therebetween. The distributed constant line type filter according to claim 1, wherein