JP2013162440A - Variable filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable filter using a resonator which produces an amount of suppression on an out-of-band high frequency side.SOLUTION: The variable filter using the resonator including a first coupling section and a second coupling section comprising transmission lines includes: a variable capacitance circuit having one end connected between the first coupling section and the second coupling section and the other end short-circuited; a first series resonance circuit having one end connected between the first coupling section and the second coupling section and the other end short-circuited; a second series resonance circuit having one end connected to a first input/output terminal connected to the side of the first coupling section opposite to the second coupling section, and the other end short-circuited; and a third series resonance circuit having one end connected to a second input/output terminal connected to the side of the second coupling section opposite to the first coupling section, and the other end short-circuited.

Description

  The present invention relates to a variable filter used in a radar, a wireless communication device, or the like.

  Conventionally, a circuit using a hairpin resonator is known as one of the variable filters (see, for example, Non-Patent Document 1). Hereinafter, the variable filter shown in Non-Patent Document 1 will be described with reference to the drawings.

  FIG. 7 is a circuit diagram showing a conventional variable filter. 7, the variable filter includes input / output terminals 101 and 102, control terminals 103, 104, 105, and 106, transmission lines 111 and 112, a hairpin resonator 121, variable capacitance elements 131, 132, 133, and 134, and a capacitor. 141, 142, 143, 144.

  Here, the input / output terminal 101 is connected to the other end of the transmission line 111 whose one end is short-circuited, and the input / output terminal 102 is connected to the other end of the transmission line 112 whose one end is short-circuited. The transmission lines 111 and 112 are provided in parallel with each other. The hairpin resonator 121 is provided between the transmission lines 111 and 112 and both ends are short-circuited.

  One end of the variable capacitance element 131 is connected to the input / output terminal 101, and the other end of the variable capacitance element 131 is connected to the other end of the capacitor 141 whose one end is short-circuited. 141 is connected to the control terminal 103.

  One end of the variable capacitance element 132 is connected to the center of the hairpin resonator 121, and the other end of the variable capacitance element 132 is connected to the other end side of the capacitor 142 whose one end is short-circuited. The control terminal 104 is connected between the element 132 and the capacitor 142.

  One end of the variable capacitance element 133 is connected to the center of the hairpin resonator 121, and the other end of the variable capacitance element 133 is connected to the other end side of the capacitor 143 whose one end is short-circuited. A control terminal 105 is connected between the element 133 and the capacitor 143.

  One end of the variable capacitance element 134 is connected to the input / output terminal 102, and the other end of the variable capacitance element 134 is connected to the other end side of the capacitor 144 whose one end is short-circuited. The control terminal 106 is connected to the terminal 144.

  In such a variable filter using the hairpin resonator 121 based on the λ / 2 line, a control signal is given to the control terminals 103, 104, 105, and 106, and the capacitance values of the variable capacitors 131, 132, 133, and 134 are given. Is changed to change the center frequency of the variable filter.

See Seong-Sik Myung et al. "Miniaturized Hairpin Tunable Filter with the Single Control Voltage", Art of Minimizing RF and Microwave Passive Components, 2008. IMWA 2008. IEEE MTT-S International Microwave Workshop Series, pp. 43-46, Dec. 2008

However, the prior art has the following problems.
In the conventional variable filter shown in Non-Patent Document 1, the center frequency is varied using a variable capacitance element. Therefore, in a variable filter using a resonator, there is a problem that the amount of suppression on the high frequency side outside the band is reduced.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a variable filter that can obtain a suppression amount on the high-frequency side outside the band in a variable filter using a resonator. And

  A variable filter according to the present invention is a variable filter using a resonator including a first coupling portion and a second coupling portion constituted by transmission lines, and includes one end between the first coupling portion and the second coupling portion. Is connected, and the other end is short-circuited, the first series resonant circuit having one end connected between the first coupling portion and the second coupling portion, and the other end short-circuited, and the first coupling portion The first input / output terminal connected to the anti-second coupling portion side is connected to the second series resonant circuit having one end connected to the other end and short-circuited to the second coupling portion on the anti-first coupling portion side. And a third series resonance circuit having one end connected to the second input / output terminal and the other end short-circuited.

According to the variable filter according to the present invention, the capacitance variable circuit having one end connected between the first coupling portion and the second coupling portion and the other end short-circuited, and the first coupling portion and the second coupling portion One end is connected to the first input / output terminal connected to the anti-second coupling portion side of the first coupling portion and one end is short-circuited at the other end. And a third series resonance circuit having one end connected to the second input / output terminal connected to the second coupling portion on the side opposite to the first coupling portion and the other end short-circuited.
Here, the center frequency of the variable filter is varied by the variable capacitance circuit, and the suppression amount is obtained on the high frequency side outside the band by the series resonance circuit.
Therefore, in a variable filter using a resonator, a suppression amount can be obtained on the high frequency side outside the band.

It is a circuit diagram which shows the variable filter which concerns on Embodiment 1 of this invention. (A) is explanatory drawing which shows the pass characteristic of the conventional variable filter, (b) is explanatory drawing which shows the pass characteristic of the variable filter which concerns on Embodiment 1 of this invention. It is another circuit diagram which shows the variable filter which concerns on Embodiment 1 of this invention. It is a circuit diagram which shows the variable filter which concerns on Embodiment 2 of this invention. It is another circuit diagram which shows the variable filter which concerns on Embodiment 2 of this invention. It is a circuit diagram which shows the series resonance circuit of the variable filter which concerns on Embodiment 3 of this invention. It is a circuit diagram which shows the conventional variable filter.

  Hereinafter, preferred embodiments of a variable filter according to the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts will be described with the same reference numerals.

Embodiment 1 FIG.
1 is a circuit diagram showing a variable filter according to Embodiment 1 of the present invention. In FIG. 1, the variable filter includes a first input / output terminal 1, a second input / output terminal 2, a first control terminal 3, a first transmission line 11, a second transmission line 12, a first hairpin resonator 21, The circuit includes a variable capacitance circuit 30, a first series resonance circuit 40, a second series resonance circuit 50, and a third series resonance circuit 60.

  The first capacitance variable circuit 30 includes a variable capacitance element 31 and a capacitor 32. The first series resonant circuit 40 includes a capacitor 41 and an inductor 42. The second series resonant circuit 50 includes a capacitor 51 and an inductor 52. The third series resonance circuit 60 includes a capacitor 61 and an inductor 62.

  Here, the first input / output terminal 1 is connected to the other end of the first transmission line 11 whose one end is short-circuited, and the second input / output terminal 2 is the other end of the second transmission line 12 whose one end is short-circuited. Connected to the side. The first transmission line 11 and the second transmission line 12 are provided in parallel to each other.

  The first hairpin resonator 21 is provided between the first transmission line 11 and the second transmission line 12, and both ends are short-circuited. The first transmission line 11, the second transmission line 12, and the first hairpin resonator 21 constitute a hairpin bandpass filter including a first coupling portion and a second coupling portion.

  In the first capacitance variable circuit 30, one end of the variable capacitance element 31 is connected to the center of the first hairpin resonator 21, and the other end of the variable capacitance element 31 is in addition to the capacitor 32 whose one end is short-circuited. Connected to the end side. The first control terminal 3 is connected between the variable capacitance element 31 and the capacitor 32.

  In the first series resonance circuit 40, one end of the capacitor 41 is connected to the center of the first hairpin resonator 21, and the other end of the capacitor 41 is connected to the other end of the inductor 42 whose one end is short-circuited. Has been.

  In the second series resonant circuit 50, one end of the capacitor 51 is connected to the first input / output terminal 1, and the other end of the capacitor 51 is connected to the other end of the inductor 52 whose one end is short-circuited.

  In the third series resonance circuit 60, one end of the capacitor 61 is connected to the second input / output terminal 2, and the other end of the capacitor 61 is connected to the other end of the inductor 62 whose one end is short-circuited.

  In such a variable filter using the first hairpin resonator 21 based on the λ / 2 line, a control signal is given to the first control terminal 3 and the capacitance value of the variable capacitor 31 is changed to change the first hairpin shape. By changing the resonance frequency of the resonator 21, the pass frequency of the hairpin bandpass filter (the center frequency of the variable filter) is varied.

  Here, the capacitor 32 of the first capacitance variable circuit 30 cuts a DC component when a control signal is supplied to the variable capacitance element 31. Further, the capacitor 41 of the first series resonance circuit 40, the capacitor 51 of the second series resonance circuit 50, and the capacitor 61 of the third series resonance circuit 60 are shunt connected to the transmission line, so that the effective line length of the line is increased. shorten.

Further, the capacitor 41, the capacitor 51, and the capacitor 61 are connected in cascade with the inductor 42 of the first series resonance circuit 40, the inductor 52 of the second series resonance circuit 50, and the inductor 62 of the third series resonance circuit 60, respectively. The amount of suppression can be obtained at an arbitrary suppression frequency ω _s on the high frequency side outside the band.

For example, at this time, each element value for obtaining the suppression amount at the suppression frequency ω _s is given by the following equations (1) and (2).

In the above formulas (1) and (2), Z _ee indicates the even mode impedance in the coupled line, Z _oe indicates the odd mode impedance in the coupled line, ω ₀ indicates the center frequency, and θ indicates the coupled line impedance. The track length is shown. The suppression frequency ω _s can be arbitrarily selected at a frequency to be suppressed on the high frequency side. In the first series resonance circuit 40, the second series resonance circuit 50, and the third series resonance circuit 60, all have the same frequency. It may be a different frequency.

  FIGS. 2A and 2B show calculation examples of the pass characteristics of the conventional variable filter and the pass characteristics of the variable filter according to Embodiment 1 of the present invention, respectively. In the conventional variable filter, as described above, in the variable filter using the resonator, there is no countermeasure against the reduction of the suppression amount on the high frequency side outside the band. On the other hand, in the variable filter according to Embodiment 1 of the present invention, the amount of suppression can be obtained on the high frequency side outside the band by the series resonance circuit.

As described above, according to the first embodiment, the first transmission line and the second transmission line that are provided in parallel to each other and whose one ends are short-circuited, and between the first transmission line and the second transmission line, respectively. A hairpin resonator having both ends short-circuited, wherein the first coupling portion and the second coupling portion are each a coupling portion between the hairpin resonator, the first transmission line, and the second transmission line. In the filter, one end is connected between the first coupling unit and the second coupling unit, one end is connected between the first coupling unit and the second coupling unit, and one end is connected between the first coupling unit and the second coupling unit. The first series resonance circuit with the other end short-circuited and the second series resonance circuit with one end connected to the first input / output terminal connected to the side opposite to the second coupling portion of the first coupling portion and the other end short-circuited And one end is connected to the second input / output terminal connected to the second coupling portion on the side opposite to the first coupling portion. The other end and a third series resonant circuit is short-circuited.
Here, the center frequency of the variable filter is varied by the variable capacitance circuit, and the suppression amount is obtained on the high frequency side outside the band by the series resonance circuit.
Therefore, in a variable filter using a resonator, a suppression amount can be obtained on the high frequency side outside the band.

  In the first embodiment, the variable filter using one hairpin resonator has been described as an example. However, the present invention is not limited to this, and two or more resonators are used as shown in FIG. Even if it is used, the same effect can be obtained.

  FIG. 3 is another circuit diagram showing the variable filter according to Embodiment 1 of the present invention. In FIG. 3, the variable filter includes a first input / output terminal 1, a second input / output terminal 2, a first control terminal 3, a second control terminal 4, a first transmission line 11, a second transmission line 12, and a first hairpin. Resonator 21, second hairpin resonator 22, first capacitance variable circuit 30, second capacitance variable circuit 70, first series resonance circuit 40, second series resonance circuit 50, third series resonance circuit 60, and fourth A series resonance circuit 80 is used.

  The first capacitance variable circuit 30 includes a variable capacitance element 31 and a capacitor 32. The second capacitance variable circuit 70 includes a variable capacitance element 71 and a capacitor 72. The first series resonant circuit 40 includes a capacitor 41 and an inductor 42. The second series resonant circuit 50 includes a capacitor 51 and an inductor 52. The third series resonance circuit 60 includes a capacitor 61 and an inductor 62. The fourth series resonance circuit 80 includes a capacitor 81 and an inductor 82.

  In the first embodiment, the variable filter using one variable capacitance element in the capacitance variable circuit has been described as an example. However, the present invention is not limited to this, and is not limited to this, but is connected in series, parallel, back-to-back, or these Even when a variable capacitance element in which two or more are connected in combination is used, the same effect can be obtained.

Embodiment 2. FIG.
FIG. 4 is a circuit diagram showing a variable filter according to Embodiment 2 of the present invention. In FIG. 4, the variable filter includes a first input / output terminal 1, a second input / output terminal 2, a first control terminal 3, a first coupling line 91, a second coupling line 92, a first capacitance variable circuit 30, a first capacitor. The series resonance circuit 40, the second series resonance circuit 50, and the third series resonance circuit 60 are configured.

  The first capacitance variable circuit 30 includes a variable capacitance element 31 and a capacitor 32. The first series resonant circuit 40 includes a capacitor 41 and an inductor 42. The second series resonant circuit 50 includes a capacitor 51 and an inductor 52. The third series resonance circuit 60 includes a capacitor 61 and an inductor 62. The first coupled line 91 includes the first transmission line 13 and the second transmission line 14, and the second coupled line 92 includes the third transmission line 15 and the fourth transmission line 16.

  Here, the first input / output terminal 1 is connected to the input terminal of the first coupling line 91, and the second input / output terminal 2 is connected to the isolation terminal of the second coupling line 92. In the first coupling line 91, the first transmission line 13 and the second transmission line 14 are provided in parallel to each other, the passing terminal and the coupling terminal are short-circuited, and the isolation terminal is connected to the input terminal of the second coupling line 92. Has been.

  In the second coupling line 92, the third transmission line 15 and the fourth transmission line 16 are provided in parallel to each other, and the passing terminal and the coupling terminal are short-circuited. The second transmission line 14 and the third transmission line 15 constitute a λ / 2 resonator, and the first transmission line 13, the second transmission line 14, the third transmission line 15, and the fourth transmission line 16 provide the first transmission line 13. A λ / 2 resonator bandpass filter including the coupling portion and the second coupling portion is configured.

  Further, in the first capacitance variable circuit 30, one end of the variable capacitance element 31 is connected between the second transmission line 14 and the third transmission line 15, and the other end of the variable capacitance element 31 is short-circuited at one end. The other end side of the capacitor 32 is connected. The first control terminal 3 is connected between the variable capacitance element 31 and the capacitor 32.

  In the first series resonant circuit 40, one end of the capacitor 41 is connected between the second transmission line 14 and the third transmission line 15, and the other end of the capacitor 41 is in addition to the inductor 42 whose one end is short-circuited. Connected to the end side.

  In the second series resonant circuit 50, one end of the capacitor 51 is connected to the first input / output terminal 1, and the other end of the capacitor 51 is connected to the other end of the inductor 52 whose one end is short-circuited.

  In the third series resonance circuit 60, one end of the capacitor 61 is connected to the second input / output terminal 2, and the other end of the capacitor 61 is connected to the other end of the inductor 62 whose one end is short-circuited.

  In such a variable filter using a λ / 2 resonator, a control signal is given to the first control terminal 3, and the capacitance value of the variable capacitance element 31 is changed to change the resonance frequency of the λ / 2 resonator. Thus, the pass frequency of the λ / 2 resonator band pass filter (the center frequency of the variable filter) is varied.

  Here, the capacitor 32 of the first capacitance variable circuit 30 cuts a DC component when a control signal is supplied to the variable capacitance element 31. Further, the capacitor 41 of the first series resonance circuit 40, the capacitor 51 of the second series resonance circuit 50, and the capacitor 61 of the third series resonance circuit 60 are shunt connected to the transmission line, so that the effective line length of the line is increased. shorten.

Further, the capacitor 41, the capacitor 51, and the capacitor 61 are connected in cascade with the inductor 42 of the first series resonance circuit 40, the inductor 52 of the second series resonance circuit 50, and the inductor 62 of the third series resonance circuit 60, respectively. The amount of suppression can be obtained at an arbitrary suppression frequency ω _s on the high frequency side outside the band.

For example, at this time, each element value for obtaining the suppression amount at the suppression frequency ω _s is given by the above equations (1) and (2). The suppression frequency ω _s can be arbitrarily selected at a frequency to be suppressed on the high frequency side. In the first series resonance circuit 40, the second series resonance circuit 50, and the third series resonance circuit 60, all have the same frequency. It may be a different frequency.

As described above, according to the second embodiment, the transmission line is configured by two transmission lines provided in parallel to each other, the input terminal is connected to the first input / output terminal, and the passing terminal and the coupling terminal are short-circuited. It is composed of one coupling line and two transmission lines provided in parallel to each other, the input terminal is connected to the isolation terminal of the first coupling line, the passing terminal and the coupling terminal are short-circuited, and the isolation terminal is the second And a second coupling line connected to the input / output terminal, wherein the first coupling unit and the second coupling unit are formed in the first coupling line and the second coupling line, respectively. A capacitance variable circuit in which one end is connected between the second coupling portion and the other end is short-circuited, and a first one in which one end is connected between the first coupling portion and the second coupling portion and the other end is short-circuited. Series resonant circuit and anti-second connection of first coupling part A second series resonant circuit having one end connected to the first input / output terminal connected to the section side and the other end short-circuited, and a second input / output terminal connected to the second coupling section on the side opposite to the first coupling section And a third series resonance circuit having one end connected to the other end and the other end short-circuited.
Here, the center frequency of the variable filter is varied by the variable capacitance circuit, and the suppression amount is obtained on the high frequency side outside the band by the series resonance circuit.
Therefore, in a variable filter using a resonator, a suppression amount can be obtained on the high frequency side outside the band.

  In the second embodiment, a variable filter using one λ / 2 resonator has been described as an example. However, the present invention is not limited to this, and there are two resonators as shown in FIG. Even if it is a case where it uses above, the same effect can be acquired.

  FIG. 5 is another circuit diagram showing a variable filter according to Embodiment 2 of the present invention. In FIG. 5, the variable filter includes a first input / output terminal 1, a second input / output terminal 2, a first control terminal 3, a second control terminal 4, a first coupling line 91, a second coupling line 92, and a third coupling. The line 93, the first capacitance variable circuit 30, the second capacitance variable circuit 70, the first series resonance circuit 40, the second series resonance circuit 50, the third series resonance circuit 60, and the fourth series resonance circuit 80 are configured.

  The first capacitance variable circuit 30 includes a variable capacitance element 31 and a capacitor 32. The second capacitance variable circuit 70 includes a variable capacitance element 71 and a capacitor 72. The first series resonant circuit 40 includes a capacitor 41 and an inductor 42. The second series resonant circuit 50 includes a capacitor 51 and an inductor 52. The third series resonance circuit 60 includes a capacitor 61 and an inductor 62. The fourth series resonance circuit 80 includes a capacitor 81 and an inductor 82.

  The first coupled line 91 includes the first transmission line 13 and the second transmission line 14, and the second coupled line 92 includes the third transmission line 15 and the fourth transmission line 16, and the third coupled line. 93 has a fifth transmission line 17 and a sixth transmission line 18.

  In the second embodiment, the variable filter using one variable capacitance element in the capacitance variable circuit is described as an example. However, the present invention is not limited to this, and is not limited to this, but is connected in series, parallel, back-to-back, or these Even when a variable capacitance element in which two or more are connected in combination is used, the same effect can be obtained.

Embodiment 3 FIG.
In the first and second embodiments, the case where the series resonant circuit is a fixed series resonant circuit including a capacitor and an inductor has been described. However, the present invention is not limited to this, and the series resonant circuit is a variable including a variable capacitance element and an inductor. A series resonant circuit may be used.

  FIG. 6 is a circuit diagram showing a series resonant circuit 40A of a variable filter according to Embodiment 3 of the present invention. This series resonance circuit can be used in place of the first series resonance circuit 40, the second series resonance circuit 50, and the third series resonance circuit 60 described above. In FIG. 6, the series resonance circuit 40A includes a control terminal 5, a variable capacitance element 41A, a capacitor 42A, and an inductor 43A.

  Here, the control terminal 5 is connected between the variable capacitance element 41A and the capacitor 42A, the variable capacitance element 41A is connected to one end of the capacitor 42A, and the other end of the capacitor 42A is connected to one end of the inductor 43A. ing.

  Further, the capacitor 42A cuts a DC component when a control signal is given to the variable capacitance element 41A. Further, the variable capacitance element 41A and the inductor 43A constitute a variable series resonance circuit, which gives a control signal to the control terminal 5 and changes the capacitance value of the variable capacitance element 41A, thereby changing the series resonance frequency.

  As described above, according to the third embodiment, the series resonant circuit is a variable series resonant circuit composed of a variable capacitance element and an inductor, so that the resonant frequency of the series resonant circuit is changed and the high frequency side outside the band is changed. The suppression frequency can be varied.

  In the third embodiment, the variable filter using one variable capacitance element in the series resonance circuit has been described as an example. However, the present invention is not limited to this, and the series connection, the parallel connection, the back-to-back connection, or these Even when a variable capacitance element in which two or more are connected in combination is used, the same effect can be obtained.

  DESCRIPTION OF SYMBOLS 1 1st input / output terminal, 2nd 2nd input / output terminal, 3 1st control terminal, 4 2nd control terminal, 5 control terminal, 11 1st transmission line, 12 2nd transmission line, 13 1st transmission line, 14th 2 transmission lines, 15 3rd transmission line, 16 4th transmission line, 17 5th transmission line, 18 6th transmission line, 21 1st hairpin resonator, 22 2nd hairpin resonator, 30 1st capacitance variable circuit , 31 variable capacitance element, 32 capacitor, 40 first series resonance circuit, 41 capacitor, 42 inductor, 40A series resonance circuit, 41A variable capacitance element, 42A capacitor, 43A inductor, 50 second series resonance circuit, 51 capacitor, 52 inductor , 60 third series resonance circuit, 61 capacitor, 62 inductor, 70 second capacitance variable circuit, 71 variable capacitance element, 72 capacitor Motor, 80 a fourth series resonant circuit, 81 a capacitor, 82 an inductor, 91 first coupled line, 92 second coupled line, 93 third connection line.

Claims (8)

A variable filter using a resonator including a first coupling portion and a second coupling portion constituted by transmission lines,
A capacitance variable circuit having one end connected between the first coupling portion and the second coupling portion and the other end short-circuited;
A first series resonant circuit having one end connected between the first coupling portion and the second coupling portion and the other end short-circuited;
A second series resonant circuit having one end connected to the first input / output terminal connected to the second coupling portion side of the first coupling portion and the other end short-circuited;
A third series resonant circuit having one end connected to the second input / output terminal connected to the second coupling portion on the side opposite to the first coupling portion and the other end short-circuited;
A variable filter comprising: A first transmission line and a second transmission line which are provided in parallel with each other and whose one ends are short-circuited;
A hairpin resonator provided between the first transmission line and the second transmission line and short-circuited at both ends;
2. The variable filter according to claim 1, wherein each of the first coupling unit and the second coupling unit is a coupling unit between the hairpin resonator, the first transmission line, and the second transmission line. . A first coupling line composed of two transmission lines provided in parallel with each other, an input terminal connected to the first input / output terminal, and a passing terminal and a coupling terminal short-circuited;
It is composed of two transmission lines provided in parallel to each other, the input terminal is connected to the isolation terminal of the first coupling line, the passing terminal and the coupling terminal are short-circuited, and the isolation terminal is the second input / output terminal A second coupled line connected to
The variable filter according to claim 1, wherein the first coupling unit and the second coupling unit are formed in a first coupling line and a second coupling line, respectively. At least one of the first series resonance circuit, the second series resonance circuit, and the third series resonance circuit is a fixed series resonance circuit including a capacitor and an inductor. The variable filter according to any one of the above. The variable series resonance circuit including at least one of the first series resonance circuit, the second series resonance circuit, and the third series resonance circuit includes a variable capacitance element and an inductor. 4. The variable filter according to any one of 3 to 3. The first series resonance circuit, the second series resonance circuit, and the third series resonance circuit all have the same resonance frequency or different resonance frequencies. The variable filter according to item. 7. The variable capacitance circuit according to claim 1, wherein variable capacitance elements are connected in series connection, parallel connection, back-to-back connection, or a combination of two or more thereof. Variable filter. The variable filter according to any one of claims 1 to 7, wherein at least two resonators are used.

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