JP2005236839A - Lamination filter and high frequency switching circuit using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compose a low pass filter which can suppress a transmission loss, and obtain high attenuation for a wide-band of a harmonics wave region, and to improve isolation property of a high frequency switching circuit using a part of the filter. <P>SOLUTION: In the lamination low pass filter which is so composed that impedance between insulation layers is shortened in a frequency band higher than a cut off frequency seen from an input terminal side, it is characterized to use a series resonance circuit which is composed of chip capacitors mounted on an upper surface of the insulation layers through a pattern circuit and a via coordinating with a frequency in which rebound occurs between the laminated low pass filter and a pattern line connecting an output terminal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an antenna switch module used for, for example, an information communication terminal, and a multilayer filter and a high frequency switch circuit for switching signals of a communication device using the antenna switch module.

  Conventionally, a filter as shown in FIG. 3 has been used for an information communication terminal. The operating principle will be briefly described.

  The capacitors 1 and 2 connected to the shunt are open to the low frequency component and shorted to the high frequency component. The inductor 3 connected in series is shorted to the low frequency component and the high frequency component is shorted. It becomes open. Therefore, the low-pass filter transmits only low frequency components.

  However, in the low-pass filter shown in FIG. 3, since the steep attenuation cannot be obtained unless the number of stages is increased, the circuit must be increased in size. In addition, in order to obtain steep attenuation with a small number of stages, the constants of each element of the low-pass filter may be set to those of the Chebyshev type low-pass filter. It was difficult to do. When a distributed constant line is used to further reduce the cost, when a certain frequency is exceeded, for example, the distributed constant line with inductivity becomes capacitive and the distributed constant line with capacitive becomes inductive, and the input impedance However, the function as a filter was lost.

  Therefore, a polar low-pass filter as shown in FIG. 4 has been devised. The operation principle will be briefly described below.

The polar low-pass filter 10 includes LC series circuits 16, 18, and 20. As shown in FIG. 5, three poles Ω ₂ ⁻¹ , Ω ₄ ⁻¹ , and Ω ₆ ⁻¹ appear in the attenuation region in the frequency characteristic of the low-pass filter 10. Here, for example, if the resonance frequency of the LC series resonance 18, that is, the pole frequency pole Ω ₄ ⁻¹ is adjusted to be small, the distance between the pole Ω ₂ ⁻¹ and the pole Ω ₄ ⁻¹ is narrowed, and attenuation between the poles The amount gets bigger.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP-A-61-77408

  However, when this is composed of distributed constant lines, when a certain frequency is exceeded, for example, distributed constant lines with inductivity become capacitive, and distributed constant lines with capacitance become inductive, and the input impedance varies greatly with frequency. The function as a filter is lost. Further, as the harmonic component is doubled and tripled, the bandwidth is also doubled and tripled, and it is difficult to obtain high attenuation in a wide band.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems by constructing a low-pass filter capable of suppressing transmission loss and obtaining high attenuation over a wide band in the harmonic region, and using a part of the low-pass filter to isolate the high-frequency switch circuit. The purpose is to improve the vibration characteristics. If this can be realized, for example, in an antenna switch, the fundamental wave signal amplified by the power amplifier can be transmitted with low loss, and the harmonic component generated by the power amplifier can be removed with a wide band and high attenuation. The amount of the signal that wraps around the receiving side can be suppressed, and the above problem can be improved.

  In order to achieve the above object, the invention described in claim 1 of the present invention is a laminated low-pass circuit that is configured so that impedance in a frequency band higher than the cutoff frequency viewed from the input terminal side is short-circuited between insulator layers. In the filter, a multilayer resonant circuit comprising a chip capacitor mounted on a top surface of an insulator layer via a distributed constant line and a via between the multilayer low-pass filter and a line connecting the output terminal is used. It is a filter. The series resonant circuit can be installed at a desired position without the need for impedance matching with the multilayer low-pass filter. By providing this series resonant circuit, the rebound component due to the fluctuation of the input impedance in the harmonic component can be easily removed. The second and third harmonic components can be sufficiently attenuated.

  The invention according to claim 2 of the present invention is a multilayer high pass filter configured such that an impedance in a frequency band higher than a cut-off frequency viewed from the input terminal side is short-circuited between insulator layers. A multilayer filter using a series resonant circuit constituted by a chip capacitor mounted on an upper surface of an insulator layer via a distributed constant line and a via between a line connecting output terminals. The series resonance circuit can be provided at a desired position without the need for impedance matching with the multilayer high-pass filter, and by providing the series resonance circuit, the series resonance circuit can be rapidly attenuated at a frequency lower than the cutoff frequency.

  The invention according to claim 3 of the present invention is the multilayer filter according to claims 1 and 2, in particular, the series resonant circuit is formed by an open stub by a distributed constant line between the insulator layers. By using an open stub, the number of mounted parts can be reduced, and the manufacturing process can be reduced at low cost.

  The invention according to claim 4 of the present invention is the multilayer filter according to claims 1 and 2, in particular, the series resonant circuit is formed by a short stub by a distributed constant line between insulator layers. By configuring with a show and a stub, the number of mounted parts can be reduced, and the cost and manufacturing man-hours can be reduced.

  The invention according to claim 5 of the present invention is a multilayer filter characterized in that a distributed constant line in which a series resonance circuit is formed between insulator layers is formed in a tapered shape. By forming the taper, the frequency band that needs to be attenuated can be attenuated over a wide band.

  According to a sixth aspect of the present invention, in particular, on the upper surface of the upper insulator layer of the multilayer filter according to the first and second aspects, a first terminal connected to the output terminal of the multilayer filter, and a second A high-frequency switch circuit having a second terminal that is a signal input terminal, a third terminal that is a first signal output terminal, and a fourth terminal that is a second signal output terminal. A chip capacitor is connected between the second terminal and the high-frequency switch circuit, and the total of the distributed constant line of the series resonance circuit and the distributed constant line provided between the chip capacitor and the high-frequency switch circuit. The high-frequency switch circuit is characterized in that the electrical length is adjusted to be ½ wavelength. By providing the series resonant circuit, the same effect as in the first and second aspects can be obtained, and the total electric power of the distributed constant line of the series resonant circuit and the distributed constant line provided between the chip capacitor and the high frequency switch circuit can be obtained. By adjusting the length to be ½ wavelength, there is an effect of configuring a high-frequency switch circuit with high isolation characteristics between the input terminals.

  The invention according to claim 7 of the present invention is the high-frequency switch circuit according to claim 6 in which the distributed constant line of the series resonant circuit is composed of a chip inductor in the same plane as the high-frequency switch circuit. Thus, the effect of the sixth aspect can be obtained, and the frequency adjustment can be easily performed by using the mounted component.

  The invention according to an eighth aspect of the present invention is the high-frequency switch circuit according to the sixth aspect, wherein the series resonant circuit chip capacitor is replaced with a variable capacitance diode. Thereby, the effect shown in claim 6 can be obtained, and the frequency adjustment can be easily performed.

  A multilayer filter and a high-frequency switch circuit using the multilayer filter according to the present invention, for example, in a wireless LAN module, transmit a fundamental wave signal amplified by a PA on the transmission side with low loss, and a harmonic component generated by the PA has a wide band. The antenna switch circuit can be removed with high attenuation, and the amount of the fundamental wave signal sneaking to the receiving side can be suppressed, so that an antenna switch circuit having an isolation characteristic of 20 decibels or more can be formed between the input and output terminals. .

  Furthermore, depending on the configuration, the number of parts can be reduced, leading to cost reduction.

(Embodiment 1)
Hereinafter, the first aspect of the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram of the multilayer low-pass filter according to Embodiment 1 of the present invention.

  As shown in FIG. 1, a basic circuit configured by a capacitor 22, an inductor 23, and a capacitor 24 so that an impedance in a frequency band higher than a cutoff frequency viewed from the input terminal side from the signal input terminal 21 to the insulating layer is short-circuited. A series resonance circuit (SRC) is provided at a connection point between the capacitor 24 and the signal output terminal 25 of a typical low pass filter (LPF). The series resonance circuit has a distributed constant line 26 and a via 27 whose characteristic impedance is inductive. And a chip capacitor 28 as a mounting component.

  Here, in the present embodiment, the series resonant circuit is provided so as to resonate with the rebound component due to the fluctuation of the input impedance with the harmonic component of the low-pass filter, so that it can be easily removed, The second and third harmonic components can be sufficiently attenuated.

  In the first embodiment of the present invention, the low-pass filter as shown in FIG. 1 is specified. However, the impedance in the frequency band higher than the cutoff frequency when the low-pass filter is viewed between the insulating layers from the input terminal side is short-circuited. When such a high-pass filter is configured, a steep attenuation characteristic can be obtained at a frequency lower than the cutoff frequency by connecting a series resonance circuit.

  Further, in the first embodiment of the present invention, the series resonance circuit as shown in FIG. 1 is specified, but the same characteristics can be obtained even when the open stub, the short stub, or the tapered stub is configured.

(Embodiment 2)
Hereinafter, the invention described in the sixth to eighth aspects of the present invention will be described using the second embodiment with reference to the drawings.

  FIG. 2 is a circuit diagram of the multilayer filter according to Embodiment 2 of the present invention.

  As shown in FIG. 2, the basic structure is configured by a capacitor 30, an inductor 31, and a capacitor 32 so that an impedance in a frequency band higher than a cutoff frequency viewed from the input terminal side is shorted between the signal input terminal 29 and the insulator layer. A series resonance circuit (SRC) is provided at the connection point between the capacitor 32 and the signal output terminal 33 of the low-pass filter (LPF). The series resonance circuit is mounted on the distributed constant line 34 and the via 35 whose characteristic impedance is inductive. The chip capacitor 36 is a component. The signal output terminal 33 is connected as an input terminal of the high-frequency switch circuit. The high-frequency switch circuit further includes a high-frequency switch circuit input terminal 37 and high-frequency switch circuit output terminals 38 and 39, and the high-frequency switch circuit input terminal. However, the first switch circuit SW1 that conducts / cuts off between the signal output terminal 33 and the high-frequency switch circuit output terminals 38, 39, the high-frequency switch circuit input terminal 37, the high-frequency switch circuit output terminal 38, and the high-frequency switch circuit output terminal. A high-frequency switch circuit including a second switch circuit SW2 that conducts and cuts off the circuit 39 is configured.

  Here, in the present embodiment, the series resonant circuit is provided to resonate at the rebound frequency due to the fluctuation of the input impedance with the harmonic component of the low-pass filter, so that it can be easily removed, and the first 2. The third harmonic component can be sufficiently attenuated.

  Further, the chip capacitor 36 of the series resonant circuit SRC is connected between the high-frequency switch circuit input terminal 37 and the second switch circuit SW2, and the distributed constant line 40, the chip capacitor 36, and the second switch of the series resonant circuit SRC are connected. A high frequency switch having high isolation characteristics between input terminals by adjusting the length of the distributed constant line 40 so that the total electrical length of the distributed constant line 40 provided between the circuit SW2 and the circuit SW2 is ½ wavelength. It has the effect of constituting a circuit.

  In the second embodiment of the present invention, the series resonant circuit SRC is expressed by the distributed constant line 40 and the chip capacitor 36. Instead of the chip capacitor 36, a chip inductor or a variable capacitance diode is used and a harmonic component of the low-pass filter is used. If it is provided so as to resonate at a rebound frequency due to fluctuations in the input impedance, an effect equivalent to that of a chip capacitor can be obtained.

  In the present invention, the series resonant circuit is provided so as to resonate at the rebound frequency due to the fluctuation of the input impedance with the harmonic component of the low-pass filter. It is also possible to provide the same, and the same effect can be obtained for the isolation characteristics of the high-frequency switch circuit.

  Further, in the present invention, the same effect can be obtained even if it is constituted by a laminated type and a coplanar type circuit.

  A multilayer filter and a high-frequency switch circuit using the multilayer filter according to the present invention, for example, in a wireless LAN module, transmit a fundamental wave signal amplified by a PA on the transmission side with low loss, and a harmonic component generated by the PA has a wide band. The antenna switch circuit can be removed with high attenuation, and the amount of the fundamental wave signal sneaking to the receiving side can be suppressed, so that an antenna switch circuit having an isolation characteristic of 20 decibels or more can be formed between the input and output terminals. .

  Furthermore, depending on the configuration, the number of parts can be reduced, leading to cost reduction.

Circuit diagram of multilayer filter in Embodiment 1 of the present invention Circuit diagram of multilayer filter in Embodiment 2 of the present invention Circuit diagram of conventional filter Circuit diagram of conventional filter Characteristics of conventional filter circuit

Explanation of symbols

21, 29 Signal input terminal 22, 24, 30, 32 Capacitor 23, 31 Inductor 25, 33 Signal output terminal 26, 34, 40 Distributed constant line 27, 35 Via 28, 36 Chip capacitor 37 High frequency switch circuit input terminal 38, 39 High frequency switch circuit output terminal

Claims (8)

A multilayer low-pass filter configured such that an impedance in a frequency band higher than a cutoff frequency viewed from the input terminal side is short-circuited between insulator layers, and a distributed constant line and a via are connected between the multilayer low-pass filter and a line connecting the output terminal. The multilayer filter using the series resonance circuit comprised by the chip capacitor mounted in the insulator layer upper surface through the. A multilayer high-pass filter configured such that an impedance in a frequency band higher than a cutoff frequency viewed from the input terminal side is short-circuited between insulator layers, and a distributed constant line and a via are connected between the multilayer high-pass filter and a line connecting the output terminal. The multilayer filter using the series resonance circuit comprised by the chip capacitor mounted in the insulator layer upper surface through the. The multilayer filter according to claim 1, wherein the series resonant circuit is formed by an open stub with a distributed constant line between insulator layers. The multilayer filter according to claim 1, wherein the series resonant circuit is formed by a short stub by a distributed constant line between insulator layers. The multilayer filter which formed in the series resonance circuit of Claims 3 and 4 the taper-shaped distributed constant line comprised between the insulator layers. A first terminal connected to an output terminal of the multilayer filter, a second terminal serving as a second signal input terminal, and a first terminal on an upper surface of the upper insulator layer of the multilayer filter according to claim 1, A high-frequency switch circuit having a third terminal that is a signal output terminal and a fourth terminal that is a second signal output terminal, wherein a chip capacitor of a series resonant circuit is connected to the second terminal and the high-frequency switch circuit The total electrical length of the distributed constant line of the series resonant circuit and the distributed constant line provided between the chip capacitor and the high frequency switch circuit is ½ wavelength. Switch circuit. 7. The high frequency switch circuit according to claim 6, wherein the distributed constant line of the series resonance circuit is constituted by a chip inductor in the same plane as the high frequency switch circuit. 7. The high frequency switch circuit according to claim 6, wherein the chip capacitor of the series resonant circuit is replaced with a variable capacitance diode.

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