JP2000252705A - Band pass filter, duplexer using it high frequency module using them and communication apparatus using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a band pass filter where an attenuation pole is formed at both sides of a pass band of the filter. SOLUTION: Microstrip line resonators 11, 12, 13, 14 are arranged side by side whose one-side ends act like open ends and whose other-side ends are connected to a ground electrode 2 acting like a ground end, the inner side microstrip line resonators 12, 13 are bent to be U-shaped, and the open ends of the outer microstrip line resonators 11, 14 are projected from the inner side microstrip line resonators 12, 13. Thus, the microstrip line resonators 11, 14 are placed under good visibility, a static capacitance is formed between them to form an attenuation pole at both sides of the pass band of the filter thereby improving the attenuation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a band-pass filter, a duplexer using the same, a high-frequency module using the same, and a communication device using the same, particularly a band used in an RF stage of a mobile communication device in a microwave band. The present invention relates to a pass filter, a duplexer using the same, a high-frequency module using the same, and a communication device using the same.

[0002]

2. Description of the Related Art With the recent miniaturization of mobile communication devices, especially mobile phones, and the use of higher frequencies, their RFs have been increased.
Demands for miniaturization and narrowing of the band-pass filters and duplexers used in stages and the like are also increasing.

FIG. 10 shows an electrode pattern of a conventional comb-line type band-pass filter. In FIG.
The band-pass filter 1 has a ground electrode 2 and a distributed constant line type in which the length is about ４ of the wavelength of the target frequency, one end is an open end, and the other end is connected to the ground electrode 2 to form a ground end. Microstrip line resonators 3, 4, 5, and 6, which are resonators;
It comprises an input terminal 7 and an output terminal 8. here,
The input terminal 7 and the output terminal 8 are connected to the microstrip line resonators 3 and 6, respectively. These are formed on a part of the other main surface of a printed circuit board having a ground electrode formed on substantially the entire surface of one main surface and are incorporated in a signal processing circuit, or as shown in FIG. Is formed on the other main surface of a small dielectric substrate 9 having a ground electrode formed on substantially the entire surface thereof and used as one chip component. In FIG. 11,
Parts that are the same as or equivalent to those in FIG. 10 are given the same symbols.

[0004] The band-pass filter 1 thus configured
In, a signal input from the input terminal 7 to the microstrip line resonator 3 is input to a filter circuit including the microstrip line resonators 3, 4, 5, and 6. Each microstrip line resonator 3, 4, 5, 6
Operate as a band-pass filter by resonating at a target frequency and being coupled to each other by a magnetic field generated particularly strongly near the ground end thereof, allowing signals to pass only in the vicinity of the target frequency. Are reflected. Then, the signal of the target frequency is output from the microstrip line resonator 6 to the output terminal 8.

FIG. 12 shows a pass characteristic and a reflection characteristic of the band-pass filter 1. In FIG. 12, the characteristic a indicates the insertion loss and the characteristic b indicates the reflection loss, and has a pass band of about 400 MHz around 4 GHz.

[0006]

However, in the above bandpass filter 1, as shown in FIG.
In the characteristic a of the insertion loss, the attenuation pole p1 is formed only on the high band side of the pass band. In general, in a band-pass filter, the larger the attenuation of the insertion loss in a band other than the pass band, the better. However, in a normal comb-line type filter, only one attenuation pole is formed, or no attenuation is formed. Since the poles are not formed, there is a problem in that it is not possible to obtain a sufficiently large amount of attenuation in an attenuation region that is a frequency band on both sides of the pass band.
Specifically, as shown in FIG.
At z, the insertion loss must be -40 dB or less (target value AL), and on the high frequency side, the insertion loss must be -40 dB or less at 4.6 GHz (target value AH).
22 dB and -23 dB.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems. A band-pass filter capable of forming attenuation poles on both sides of a pass band, a duplexer using the same, and a high-frequency module using the same are provided. And a communication device using the same.

[0008]

In order to achieve the above object, a band-pass filter according to the present invention comprises a plurality of distributed constant line resonators each having one open end and the other end grounded. In the configured comb-line type band-pass filter, the open end of the distributed constant line type resonator on the outside is
It is characterized in that it is formed so as to protrude from the distributed constant line type resonator on the inside.

Further, the bandpass filter according to the present invention is characterized in that the open ends of the distributed line resonator on the inner side are formed close to each other.

The band-pass filter according to the present invention further includes a ground electrode provided near the open end of the distributed constant line resonator, and a ground electrode provided between the open end of the distributed constant line resonator and the ground electrode. It is characterized by forming a capacitance.

Further, a duplexer according to the present invention is characterized in that any one of the above bandpass filters is connected to each other.

Further, a high-frequency module according to the present invention is characterized in that the high-frequency module is configured using any one of the above-described band-pass filters or duplexers.

Further, a communication apparatus according to the present invention is characterized by being constituted by using the above-mentioned high-frequency module.

With such a configuration, in the band-pass filter of the present invention, attenuation poles can be provided on both sides of the pass band.

Further, in the duplexer of the present invention,
The size can be reduced.

Further, in the high-frequency module of the present invention, the circuit configuration can be simplified to reduce the size and cost.

Further, in the communication device of the present invention, downsizing and cost reduction can be achieved.

[0018]

FIG. 1 shows an electrode pattern of an embodiment of a band-pass filter according to the present invention. 1, the same or equivalent parts as those in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 1, a band-pass filter 10 includes:
The ground electrode 2 and the length is about a quarter of the wavelength of the target frequency.
And microstrip line resonators 11, 12, 13, and 14 which are distributed constant line type resonators, one end of which is an open end and the other end is connected to the ground electrode 2 and serve as a ground end, and an input terminal 7 and an output terminal 8. , Ground electrodes 15 and 17, comb-shaped electrode pair 16,
18, 19, and 20. Here, a pair of comb-shaped electrodes 16 and 18 are provided between the open ends of the outer microstrip line resonators 11 and 14 and the ground electrodes 15 and 17, respectively, to form a capacitance. Also, the inner microstrip line resonator 1
2 and 13 are formed so that their open ends are bent in a U-shape so as to approach each other, and a capacitance is formed between them. Further, between the open ends of the microstrip line resonators 12 and 13 and the ground electrode 2, pairs of comb electrodes 19 and 20 are provided, respectively, to form a capacitance. These are formed, for example, on a part of the other main surface of a printed circuit board having a ground electrode formed on substantially the entire surface of one main surface and incorporated in a signal processing circuit, or as shown in FIG. Is formed on the other main surface of the small dielectric substrate 21 having a ground electrode formed on almost the entire surface thereof and used as one chip component. Note that, in FIG. 2, the same reference numerals are given to the same or equivalent parts as in FIG.

The band-pass filter 1 configured as described above
0, the microstrip line resonators 11, 1
The capacitance formed at the open ends of 2, 13, and 14 has a function of lowering the resonance frequency, and accordingly, the substantial length of each microstrip line resonator 11, 12, 13, 14 is reduced accordingly. There is an effect that the wavelength of the target frequency is made shorter than about one-fourth and the size of the band-pass filter 10 is reduced.

Further, since the inner microstrip line resonators 12 and 13 are formed by bending in a U-shape, the open ends of the outer microstrip line resonators 11 and 14 are connected to the inner microstrip line resonators. Projecting from vessels 12 and 13. Therefore, there is no obstacle between the open ends of the outer microstrip line resonators 11 and 14, and the mutual visibility is improved. As a result, the microstrip line resonator 11
And 14, a direct capacitance is formed between the open ends.

FIG. 3 shows the pass characteristics and the reflection characteristics of the band-pass filter 10 formed as described above. In FIG. 3, the characteristic c indicates the insertion loss, and the characteristic d indicates the reflection loss. As can be seen from the characteristic c of the insertion loss, it has a pass band of about 400 MHz around 4 GHz as in the conventional example, but two attenuation poles p2 and p3 are formed on both sides thereof. Therefore, the amount of attenuation in the attenuation region on both sides of the pass band is improved as compared with the related art. Specifically, on the low frequency side, the insertion loss is -43 dB at 3.4 GHz,
On the high frequency side, the insertion loss is -44 dB at 4.6 GHz, and both are -40 dB that satisfy the target values AL and AH.
B and below are achieved.

As described above, the microstrip line resonators 12 and 13 inside the band-pass filter 10 are bent in a U shape, and the microstrip line resonators 11 outside the band-pass filter 10 are bent.
And 13 are formed so that the open ends thereof protrude from the inner microstrip line resonators 12 and 13, thereby forming a direct capacitance between the open ends of the microstrip line resonators 11 and 14. Therefore, attenuation poles can be formed in attenuation regions on both sides of the pass band, and the amount of attenuation can be increased.

The pass band can also be obtained by making the open end sides of the inner microstrip line resonators 12 and 13 bent in a U-shape close to each other and forming a capacitance between them. Attenuation poles can be formed in the attenuation regions on both sides of, and the amount of attenuation can be improved.

FIGS. 4 to 6 show electrode patterns of another embodiment of the bandpass filter of the present invention. 4 to 6, the same or equivalent parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

First, referring to FIG.
5 is the ground electrode 2 and the length is about 4 wavelengths of the target frequency.
A microstrip line resonator 26, 27, 28, 29 which is a distributed constant line type resonator whose one end is an open end and the other end is connected to the ground electrode 2 to be a ground end; An output terminal 8 is provided. The bandpass filter 25 differs from the bandpass filter 10 of FIG. 1 in that the microstrip line resonators 26, 27, 28,
The only difference is that there is no comb-shaped electrode pair for forming a capacitance between the open end of 29 and the ground electrode.

The band-pass filter 2 configured as described above
5, the same operation and effect as the band-pass filter 10 can be obtained except that there is no effect of miniaturization by forming a capacitance between the open end of the microstrip line resonator and the ground electrode. it can.

In FIG. 5, the band-pass filter 30 is connected to the ground electrode 2 and has a length approximately one-quarter of the wavelength of the target frequency, one end being open and the other end being connected to the ground electrode 2. And a microstrip line resonator 31, 32, 33, 34, which is a distributed-constant-line-type resonator serving as a ground end, and an input terminal 7 and an output terminal 8. The bandpass filter 30 differs from the bandpass filter 25 of FIG. 4 in that the inner microstrip line resonators 32 and 33 are formed in an L-shape, and the open ends thereof are brought close to each other so as to allow static between them. It is only that capacitance was formed.

The band-pass filter 3 configured as described above
0, the outer microstrip line resonator 3
Since the open ends of 1 and 34 are formed to protrude from the inner microstrip line resonators 32 and 33, a capacitance is formed between the open end of the microstrip line resonator and the ground electrode. The same operation and effect as the band-pass filter 10 can be obtained except that there is no effect of downsizing.

Further, in FIG. 6, the band-pass filter 35 is connected to the ground electrode 2 and has a length approximately one-quarter of the wavelength of the target frequency, one open end and the other end connected to the ground electrode 2. A microstrip line resonator 36, 37, 38, 39, which is a distributed constant line type resonator having a ground end, and an input terminal 7 and an output terminal 8. The bandpass filter 35 differs from the bandpass filter 30 of FIG. 5 in that the outer microstrip line resonators 36 and 39
Is also formed in an L-shape, with its open ends facing each other.

The bandpass filter 3 configured as described above
5, the outer microstrip line resonator 3
The open ends of 1 and 34 not only protrude from the inner microstrip line resonators 32 and 33 but also the outer microstrip line resonators 36 and 3
9, the capacitance formed between the open ends of the band-pass filter 9 can be further increased, and in addition to the same operation and effect as the band-pass filter 30, the attenuation poles on both sides of the pass band can be easily formed. There is also an effect.

In each of the above embodiments, the bandpass filter is constituted by using the microstrip line resonators, which are four distributed constant line type resonators. However, the number of microstrip line resonators is four. The present invention is not limited to this, and any structure may be used as long as it is configured using three or more microstrip line resonators. 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 line resonator having a triplate structure. Things.

FIG. 7 is a block diagram showing an embodiment of a duplexer using the band-pass filter of the present invention. In FIG. 8, a duplexer 60 includes two band-pass filters 61 and 62 of the present invention having different frequency bands from each other, one of the terminals being connected to each other to form an antenna terminal 63, and the other terminal of the band-pass filter 61 being transmitted. The side terminal 64 and the other terminal of the band-pass filter 62 are configured as a reception side terminal 65.

In the duplexer configured as described above, the antenna terminal 63 is connected to an external antenna, the transmitting terminal 64 is connected to a transmitting circuit, and the receiving terminal 65 is connected to a receiving circuit to form a communication device. During transmission and reception using an antenna, a transmission signal is prevented from entering a reception circuit and a reception signal is prevented from entering a transmission circuit. In particular,
By using the band-pass filter of the present invention, the attenuation in the pass band of the partner band-pass filter can be increased, and sufficient isolation between the transmitting terminal 64 and the receiving terminal 65 can be obtained. it can.

FIG. 8 shows an embodiment of a high-frequency module using the band-pass filter of the present invention. 8, a high-frequency module 40 includes a band-pass filter 10 of the present invention as an RF filter, an RF amplifier 41, a local oscillator 42, a mixer 43, an IF filter 44, an IF amplifier 45, an input terminal 46 and an output terminal 47. Down converter. Here, the input terminal 46 is connected to the mixer 43 via the band pass filter 10 and the RF amplifier 41 in this order. The local oscillator 42 is also connected to the mixer 43. The output of the mixer 43 is connected to an output terminal 47 via an IF filter 44 and an IF amplifier 45 in this order.

The high-frequency module 4 configured as described above
At 0, since the band-pass filter 10 of the present invention is used, a large amount of attenuation in the attenuation region can be obtained, so that it is not necessary to use another component such as a notch filter for compensating for the insufficient amount of attenuation. . In addition, an input matching circuit such as an RF amplifier connected at a subsequent stage can be simplified. As a result, the size and cost of the high-frequency module 40 can be reduced.

It should be noted that in FIG.
Although the high-frequency module 40 is configured by using 0, the high-frequency module may be configured by using the band-pass filters 25, 30, and 35 and the duplexer 60 illustrated in FIGS. Is played.

FIG. 9 shows an embodiment of a communication device constituted by using the high-frequency module of the present invention. In FIG.
The communication device 50 includes a high-frequency module 40, an antenna 5
1. It is composed of a signal processing circuit 52. Here, the antenna 51 is connected to the high-frequency module 40, and the high-frequency module 40 is connected to the signal processing circuit 52.

In the communication device 50 configured as described above, by using the high-frequency module 40 of the present invention, size reduction and cost reduction can be achieved.

[0040]

According to the bandpass filter of the present invention, a plurality of distributed constant line type resonators having one open end and the other end grounded are arranged side by side, and the distributed distributed line type resonator on the outer side is arranged. By forming the open end so as to protrude from the inner distributed-constant-line-type resonator, attenuation poles can be formed on both sides of the passband to increase the attenuation in the attenuation region.
Also, by forming a capacitance between the open ends of the inner distributed-constant-line-type resonators, attenuation poles can be formed on both sides of the pass band to increase the attenuation in the attenuation range. . Further, by forming a capacitance between the open end of each distributed constant line resonator and the ground electrode, the size of the band-pass filter can be reduced.

Further, according to the duplexer of the present invention, the size can be reduced by using the band-pass filter of the present invention, and sufficient isolation between the transmitting terminal and the receiving terminal can be obtained.

According to the high-frequency module of the present invention, the size and cost can be reduced by using the band-pass filter of the present invention.

Further, according to the communication device of the present invention, the size and cost can be reduced by using the high-frequency module of the present invention.

[Brief description of the drawings]

FIG. 1 is a diagram showing an electrode pattern of an embodiment of a bandpass filter of the present invention.

FIG. 2 is a perspective view showing the configuration of the bandpass filter of FIG.

FIG. 3 is a diagram showing pass characteristics and reflection characteristics of the band-pass filter of FIG.

FIG. 4 is a diagram showing an electrode pattern of another embodiment of the bandpass filter of the present invention.

FIG. 5 is a diagram showing an electrode pattern of still another embodiment of the bandpass filter of the present invention.

FIG. 6 is a diagram showing an electrode pattern of still another embodiment of the bandpass filter of the present invention.

FIG. 7 is a block diagram showing an embodiment of a duplexer according to the present invention.

FIG. 8 is a block diagram showing one embodiment of the high-frequency module of the present invention.

FIG. 9 is a block diagram showing one embodiment of the communication device of the present invention.

FIG. 10 is a diagram showing an electrode pattern of a conventional band-pass filter.

FIG. 11 is a perspective view showing the configuration of the bandpass filter of FIG.

FIG. 12 is a diagram showing pass characteristics and reflection characteristics of a conventional band-pass filter.

[Explanation of symbols]

2, 15, 17: ground electrode 7: input terminal 8, output terminal 10, 25, 30, 35: band-pass filter 11, 12, 13, 14, 26, 27, 28, 29, 3
1, 32, 33, 34, 36, 37, 38, 39: Microstrip line resonator 16, 18, 19, 20: Comb electrode pair 21: Dielectric substrate 40: High frequency module 50: Communication device 60: Duplexer

Claims (6)

[Claims] 1. A comb-line type band-pass filter comprising a plurality of distributed-constant-line-type resonators each having an open end at one end and a grounding end at the other end. Characterized in that the open end of the band-pass filter protrudes from the distributed constant line type resonator on the inside. 2. The band-pass filter according to claim 1, wherein the open ends of the distributed constant line type resonator on the inner side are formed close to each other. 3. A method according to claim 1, wherein a ground electrode is provided near an open end of the distributed constant line resonator, and a capacitance is formed between the open end of the distributed constant line resonator and the ground electrode. The band-pass filter according to claim 1, wherein the band-pass filter is a filter. 4. A duplexer comprising two band-pass filters according to claim 1 connected to each other. 5. A high-frequency module comprising the band-pass filter according to claim 1 or the duplexer according to claim 4. 6. A communication device comprising the high-frequency module according to claim 5.