JP2003110320A - Resonance circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resonance circuit, which is capable of easily removing a frequency component and has a high no-load Q. SOLUTION: A series circuit composed of a capacitor element C1, a thin film capacitor element C2, which varies in capacitance when a control voltage is applied, and a strip line Re is interposed in between a transmission line S which transmits high-frequency signals and a ground potential. A control voltage terminal CONT, where the control voltage is applied, is provided between the capacitor element C1 and the thin film capacitor element C2.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonance circuit such as a notch circuit whose frequency characteristic is changed by voltage control. 2. Description of the Related Art In transmitting a high-frequency signal between a resonance circuit, a filter, and other high-frequency circuit units, a series resonance circuit called a notch circuit is used to remove harmonic components and unnecessary noise components. Was provided. This allows
It can remove only a predetermined frequency component of a high-frequency signal, and is often used not only for removing the above-described harmonic components and noise, but also for, for example, relaxing the filter characteristics at the subsequent stage. Also, arbitrarily changing the frequency of the predetermined frequency component is often used to stabilize the control method and characteristics of the entire high-frequency circuit. FIG. 8 shows a conventional resonance circuit whose resonance frequency can be controlled. In FIG. 8, Re is a strip line as a resonance element, C is a capacitor, and DV is a variable capacitance diode. S is a transmission line connecting between the two high-frequency circuit units A and B. The configuration of this resonance circuit is such that a capacitor C and a variable capacitance diode D are provided between the transmission line S and the ground.
V and a strip line Re are connected in series. That is, the anode of the variable capacitance diode DV is connected to the capacitor C
, And the cathode is connected to one end of the strip line Re. A control voltage terminal CONT is arranged at the anode of the variable capacitance diode DV via a control voltage control circuit R including a coil LR and a capacitor CR. That is, the capacitor C, the variable capacitance diode DV,
The strip line Re is shunt-connected to the transmission line S. [0006] Since the series combined capacitance of the variable capacitance diode D and the capacitor C changes according to the control voltage applied to the variable capacitance diode DV, the series resonance circuit includes the variable capacitance diode D, the capacitor C, and the strip line Re. , The impedance becomes 0 with respect to the controlled resonance frequency, and only the frequency component of the high-frequency signal flowing through the transmission line can be dropped (poured) to the ground. As shown in FIG. 8, in the resonance circuit in which the variable capacitance diode DV is connected in series to the strip line Re, the control voltage supplied to the variable capacitance diode DV causes the high frequency signal component flowing through the transmission line S to have the configuration shown in FIG. As shown in (5), for example, the resonance frequency can be arbitrarily changed from the frequency f1 to the frequency f4. However, the variable capacitance diode DV has a low no-load Q, for example, about 10 to 20, so that the strip line Re itself has a high no-load Q. As a result, the Q value of the entire resonance circuit deteriorates,
As a result, there is a problem that the attenuation waveform of the resonance frequency is deteriorated. In addition, since the capacitance change rate of the variable capacitance diode DV is not completely linear with respect to the applied voltage (the linearity is poor), when setting the resonance frequency to a desired value, the control voltage is accurately controlled. Needed. Therefore, when used as a notch circuit, the selectivity of the resonance frequency is reduced, and
The Q value of the entire circuit depends on the variable capacitance diode DV which is bad, and even if the Q value of the strip line Re is made good, the characteristics deteriorate. The present invention has been devised in view of the above-mentioned problems, and provides a resonance circuit which can easily remove unnecessary frequency components having a predetermined value and has a high no-load Q. It is in. [0011] The present invention relates to a tunable capacitor, a strip line, and a tunable capacitor whose capacitance component changes when a control voltage is applied between a transmission line through which a high-frequency signal is transmitted and a ground potential. Are arranged in series, and a control voltage terminal to which the control voltage is applied is provided between the capacitive element and the tunable capacitor. As described above, according to the present invention, a series resonance circuit is formed by arranging a strip line, a tunable capacitor whose capacitance component changes by application of a control voltage, and a capacitance element in series. By changing the control voltage, the capacitance component of the tunable capacitor can be controlled with good linearity, and the high selectivity of the tunable capacitor makes the overall selectivity stable and good (the characteristics are steep). , A sufficient amount of attenuation can be obtained. The fixed capacitance element performs an operation for preventing a DC control voltage from flowing into the transmission line. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a resonance circuit according to the present invention will be described in detail with reference to the drawings. FIG. 1 is an equivalent circuit diagram of the resonance circuit of the present invention, FIG. 2 is an exploded perspective view of components of a resonance circuit component having the resonance circuit, and FIG. 3 is a top view thereof. Referring to FIG. 1, the resonance circuit of the present invention mainly comprises a strip line Re, a tunable capacitor C2, and a capacitive element C1 for blocking a DC signal. The tunable capacitor C2 has a coil L
There is provided a control voltage control circuit R connected to R and the capacitor CR. And the tunable capacitor C2
The control voltage is supplied to the control voltage terminal CONT via the control signal control circuit R. In the figure, a capacitive element C1, a tunable capacitor C2 and a strip line Re for blocking a DC signal are connected in series between the transmission line S and the ground potential from the transmission line S side. The other end of the strip line Re is connected to the ground potential. That is,
A shunt connection is made to the transmission line S. A control voltage is supplied to a connection between the capacitor C1 and the tunable capacitor C2 via a control voltage control circuit R. The control voltage control circuit R operates as a high-frequency cutoff circuit to prevent a high-frequency component flowing through the transmission line S from flowing to the control terminal CONT or the ground potential via the capacitive element C1 and the tunable capacitor C2. ing. Specifically, the high frequency signal is cut off by the coil LR, and the control signal is not dropped to the ground potential by the capacitor CR. In such a structure, the resonance circuit is shunt-connected to the transmission line S, and the control voltage is supplied to the tunable capacitor C through the control voltage control circuit R.
2 is applied. As a result, a DC voltage is applied between the terminals of the tunable capacitor C2, and the capacitance of the tunable capacitor C2 changes. Then, the capacitance component of the series resonance circuit changes, and, for example, the notch frequency also changes. FIG. 2 is an exploded perspective view of each component of a resonance circuit component having the series resonance circuit of the present invention, and FIG. 3 is a top view thereof. The resonance circuit component is a laminated body 10 in which a plurality of dielectric layers, for example, four dielectric layers 10a to 10d are laminated.
It is mainly composed of For example, the upper dielectric layer 1
On the surface of Oa, three electrode patterns 13, 2a, to which a conductor film 6 serving as a ground potential, a chip coil 12 serving as a coil LR of the control voltage control circuit R, and a trimmer capacitor element 3 serving as a tunable capacitor C2 are connected. 9
Having. The electrode pattern 13 is connected to the control voltage terminal electrode 14 as it is. The electrode pattern 9 is directly connected to the via-hole conductor. In addition, between the first dielectric layer 10a and the second dielectric layer 10b from the top, for example, the dielectric layer 1
0b, an electrode pattern 2b facing the electrode pattern 2a and generating a capacitance component constituting the capacitor C1.
Is formed. A part of the electrode pattern 2b is extended to the end face of the laminated body 10 and the input / output terminal electrode 8
a, 8b. Also, between the second dielectric layer 10b and the third dielectric layer 10c from the top, for example, the dielectric layer 1
On the upper surface of Oc, a strip-shaped conductive film is formed, which is connected to the electrode pattern 9 via a via-hole conductor at one end and the other end becomes a strip line extending to the end surface of the multilayer body 10. A conductor film 7 having a ground potential is formed on the lower main surface of the lowermost dielectric layer 10d to be joined to the third dielectric layer 10c from the top. The control voltage terminal electrode 14, the input / output terminal electrodes 8a and 8b connected to the transmission line S, and the ground potential conductor film 5 are formed on the end face of the laminated body 10. The ground potential conductive film 5 is connected to the ground potential conductive films formed on both main surfaces of the laminate 10. That is, the control voltage terminal electrode 14 is
0, connected to the electrode pattern via the chip coil 12, connected to the electrode pattern via the chip coil 12, and further connected from the tunable capacitor C2 (3) to one end of the conductor film 1 serving as a strip line to the other end of the ground potential. Connected to.
This path becomes the flow of the control voltage supplied to the control terminal electrode 14. The input / output terminal electrodes 8a and 8b are connected to a tunable capacitor 3 serving as a tunable capacitor C2 via a capacitance component capacitor C1 generated at a portion where the electrode pattern 2b and the electrode pattern 2a face each other. One end of the conductor film 1 serving as a line is connected to the other end of the ground potential. This path becomes the flow of the high-frequency signal. FIG. 5 is a perspective view of this as viewed from the upper surface side of the laminate 10.
Shown in Here, the dielectric layers 10a to 10d are dielectric materials composed of a dielectric ceramic material and an oxide or a low-melting glass material which can be fired at a low temperature. The electrode patterns 13, 2a, 9 and the various terminal electrodes 5, 8a, 8b, 13 on the end faces are made of a conductive material mainly composed of Ag, Cu, or the like which has relatively excellent high-frequency characteristics. In the structure described above, the control voltage control circuit R
Is not provided. In this case, as shown in FIG. 4, the capacitor CR is used as the chip capacitor 19, and a predetermined wiring of the printed wiring board 40 on which the resonance circuit components are mounted, that is, the wiring 42 of the ground potential and the wiring 41 for the control voltage supply Connect between. Further, the capacitor C may be arranged between the electrode pattern 13 of the resonance circuit component and the ground conductor film 6. In FIG. 4, the transmission line S is a wiring 43. Next, the tunable capacitor C2 (3)
Will be described. Tunable capacitor C2 (3)
As shown in FIGS. 5A and 5B, a supporting substrate 51, a lower electrode layer 52, a high dielectric layer 53 whose permittivity changes by applying a voltage, an upper electrode layer 54, and a protective film 55 are sequentially deposited. It is formed. The support substrate 51 is made of a ceramic, a sapphire substrate, or the like. On its surface, a lower electrode layer 52 made of Pt, Au or a solid solution thereof oriented to the (111) plane is formed. And this lower electrode 5
A high dielectric layer 53 composed of perovskite-type oxide crystal particles containing at least Ba, Sr, and Ti is formed on a part of 2. In the high dielectric layer, the range of x in (Ba _x Sr _{1 -x} ) TiO ₃ in the perovskite oxide is 0.4 to 0.6. The thickness of the high dielectric layer 53 is 1 μm or less, and the dielectric crystal grains constituting the dielectric layer are equiaxed, and the average grain size of the crystal grains is 0.5 μm or less. The high dielectric layer 53 has a composition (BaS
r) The range of x in Ti _x O ₃ may be 0.7 to 0.9. Then, on such a high dielectric layer 53,
The upper electrode layer 54 is provided. This upper electrode layer 54 is made of P
It is composed of a thin film conductor film such as t, Au or the like. Then, terminal electrodes 56, 56 such as solder bumps are formed on the lower electrode layer 52 and the upper electrode layer 54 so as to avoid the high dielectric layer 53, and only the terminal electrodes 56, 56 are exposed on the support substrate 51. Insulation protection 55 from resin, inorganic metal, etc.
Is coated. The tunable capacitor 3 having such a structure is connected to the electrode pattern 2a of the multilayer substrate 10.
And 9 (actually, land electrodes of via-hole conductors) are joined so that one terminal electrode 56 is attached. FIG. 6 shows the transmission characteristics of the series resonance circuit (notch circuit) when the control voltage is changed in the above-described resonance circuit. In the present invention, since the variable capacitance diode DV whose Q value has been deteriorated in the past is not used, deterioration of the Q value can be effectively suppressed as a resonance circuit component.
As a result, a steep attenuation characteristic is obtained as compared with the conventional transmission characteristic shown in FIG. Further, since the linearity of the tunable capacitor C2 is much better than the linearity of the variable capacitance diode DV, it is possible to control the frequencies f1 to f4 in proportion to the control voltage. As shown in FIG. 7, even when compared with the characteristics of a conventional resonance circuit using a variable capacitance diode DV at the same frequency, the no-load Q is high, and as a result, the attenuation is large. it can. Although the above-described resonance circuit component is an example in which an equivalent circuit of the resonance circuit shown in FIG. 1 is formed, the configuration of the resonance circuit component and the connection state with the printed wiring board are shown in FIGS. 4 is not limited, and various configurations can be changed. As described above, in the resonance circuit of the present invention, the transmission line connecting the high-frequency circuit units and the ground potential
A resonance circuit in which a capacitor, a tunable capacitor, a strip line, and the like are connected in series is shunt-connected. Since the high-Q tunable capacitor is connected in series, for example, a notch frequency of the resonance circuit can be changed by a control voltage for the tunable capacitor. In addition, since the Q value of the entire resonance circuit component can be kept high, the characteristics are steep and a large amount of attenuation can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an equivalent circuit diagram of a resonance circuit according to the present invention. FIG. 2 is an exploded perspective view of each element of a resonance circuit component including the resonance circuit of the present invention. FIG. 3 is a top view of a resonance circuit component including the resonance circuit of the present invention. FIG. 4 is an external view of a state in which a resonance circuit component including the resonance circuit of the present invention is mounted on a printed wiring board. FIG. 5 (a) shows a cross-sectional structure of a tunable capacitor used in the resonance circuit of the present invention, and FIG. 5 (b) is a plan view in which an insulating protective film is omitted. FIG. 6 is a characteristic diagram showing an attenuation characteristic of the resonance circuit of the present invention. FIG. 7 is a comparison diagram of characteristics of the resonance circuit of the present invention and a conventional resonance circuit at the same frequency. FIG. 8 is an equivalent circuit diagram of a conventional resonance circuit. FIG. 9 is a characteristic diagram showing an attenuation characteristic of a conventional resonance circuit. [Description of Signs] 1. Conductor films 2a and 2b to be strip lines ... Electrode pattern C1 to be capacitor C1 ... Capacitor 3 (C2) ... Tunable capacitors 8a and 8b ... I / O terminal electrodes 5 and 6 , 7, ground potential conductor film 9, electrode pattern (via hole conductor) 10 (10a to 10d), dielectric layer 12, chip coil 13, control voltage terminal electrode 19, chip capacitor (capacitor CR) R ..Control voltage control circuit Re..Strip line CONT: control terminal

Claims (1)

Claims: 1. A capacitance element, a tunable capacitor whose capacitance component changes by application of a control voltage, and a strip line are serially arranged between a transmission line for transmitting a high-frequency signal and a ground potential. And a control voltage terminal to which the control voltage is applied is provided between the capacitive element and the tunable capacitor.