JP6904433B2 - Bandpass filter - Google Patents

Description

The present invention relates to a bandpass filter.

Conventionally, a bandpass filter is known. For example, according to International Publication No. 2007/11935 (Patent Document 1), an input / output capacitor electrode for connecting an input electrode and an output electrode to a predetermined electrode layer among a plurality of electrode layers by capacitance. A bandpass filter provided with is disclosed. The input / output capacitor electrode creates an attenuation pole on the high frequency side of the passband and two attenuation poles on the low frequency side of the passband. As a result, both the attenuation characteristic from the pass band to the low frequency side and the attenuation characteristic from the pass band to the high frequency side can be steep.

International Publication No. 2007/11935

In order to bring the frequency characteristics of the bandpass filter closer to the desired frequency characteristics, it is possible to change the decay poles that occur at frequencies higher than the passband without changing the frequencies of the decay poles that occur in the frequency band lower than the passband. May be needed. However, Patent Document 1 specifically describes a configuration capable of changing the frequency of the decaying pole generated in the frequency higher than the passband without changing the frequency of the decaying pole generated in the frequency band lower than the passband. Not disclosed.

The present invention has been made to solve the above problems, and an object of the present invention is to bring the frequency characteristics of a bandpass filter closer to a desired frequency characteristics.

One aspect of the stacked band passage filter according to the present invention is the first terminal and the second terminal, the first LC parallel resonator, the second LC parallel resonator, the third LC parallel resonator, the fourth LC parallel resonator, and the first capacitor. , A second capacitor, and a third capacitor. The first LC parallel resonator is electrically connected to the first terminal at the first connection point. The first LC parallel resonator includes a first inductor and a fourth capacitor. The first inductor and the fourth capacitor are connected in parallel between the first connection point and the grounding point. The second LC parallel resonator is electrically connected to the second terminal at the second connection point. The second LC parallel resonator includes a second inductor and a fifth capacitor. The second inductor and the fifth capacitor are connected in parallel between the second connection point and the grounding point. The third LC parallel resonator is magnetically coupled with the first LC parallel resonator. The fourth LC parallel resonator magnetically couples with the second LC parallel resonator and the third LC parallel resonator. The first capacitor and the second capacitor are connected in series between the first connection point and the second connection point. The third capacitor is connected between the grounding point and the third connection point of the first capacitor and the second capacitor.

According to the bandpass filter according to the present invention, the attenuation pole generated in the frequency band lower than the pass band by the third capacitor connected between the grounding point and the third connection point of the first and second capacitors. It is possible to change the frequency of the decaying poles that occur at frequencies higher than the passband with little change in frequency. As a result, the frequency characteristics of the bandpass filter can be brought close to the desired frequency characteristics.

It is an equivalent circuit diagram of the bandpass filter which concerns on embodiment. It is an external perspective view of the bandpass filter of FIG. It is an exploded perspective view which shows an example of the laminated structure of the bandpass filter of FIG. It is an equivalent circuit diagram of the bandpass filter which concerns on a comparative example. It is a figure which also shows the insertion loss of the bandpass filter of FIG. 1 and the insertion loss of the bandpass filter of FIG. It is an equivalent circuit diagram of the bandpass filter which concerns on the modification of embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In principle, the same or corresponding parts in the drawings are designated by the same reference numerals and the description is not repeated.

FIG. 1 is an equivalent circuit diagram of the bandpass filter 1 according to the embodiment. As shown in FIG. 1, the bandpass filter 1 includes input / output terminals P10 and P100, LC parallel resonators 11 to 14, and capacitors 103, 108, 111 to 113.

The LC parallel resonator 11 is electrically connected to the input / output terminal P10 at the connection point 114, and a signal is transmitted to and from the input / output terminal P10 without magnetic coupling. The LC parallel resonator 11 includes an inductor 101 and a capacitor 102. The inductor 101 and the capacitor 102 are connected in parallel between the connection point 114 and the grounding point GND.

The capacitor 103 is connected between the LC parallel resonator 12 and the connection point 114. The LC parallel resonator 12 includes an inductor 104 and a capacitor 105. The inductor 104 and the capacitor 105 are connected in parallel between the grounding point GND and the connection point 115 of the LC parallel resonator 12 and the capacitor 103.

The LC parallel resonator 14 is electrically connected to the input / output terminal P100 at the connection point 117, and a signal is transmitted to and from the input / output terminal P100 without magnetic coupling. The LC parallel resonator 14 includes an inductor 109 and a capacitor 110. The inductor 109 and the capacitor 110 are connected in parallel between the connection point 117 and the grounding point GND.

The capacitor 108 is connected between the LC parallel resonator 13 and the connection point 117. The LC parallel resonator 13 includes an inductor 106 and a capacitor 107. The inductor 106 and the capacitor 107 are connected in parallel between the grounding point GND and the connection point 116 of the LC parallel resonator 13 and the capacitor 108.

Capacitors 111 and 112 are connected in series between connection points 114 and 117. The capacitor 113 is connected between the grounding point GND and the connection points 118 of the capacitors 111 and 112.

A magnetic coupling M15 is formed between the inductors 101 and 104. A magnetic coupling M16 is formed between the inductors 104 and 106. A magnetic coupling M17 is formed between the inductors 106 and 109.

When a signal is input to the input / output terminal P10, the signal is transmitted to the LC parallel resonator 11 without going through magnetic coupling. The signal transmitted to the LC parallel resonator 11 is transmitted to the LC parallel resonator 12 via the magnetic coupling M15, transmitted to the LC parallel resonator 13 via the magnetic coupling M16, and LC parallel via the magnetic coupling M17. It is transmitted to the resonator 14. The signal transmitted to the LC parallel resonator 14 is transmitted to the input / output terminal P100 without going through magnetic coupling, and is output from the input / output terminal P100.

When a signal is input to the input / output terminal P100, the signal is transmitted to the LC parallel resonator 14 without going through magnetic coupling. The signal transmitted to the LC parallel resonator 14 is transmitted to the LC parallel resonator 13 via the magnetic coupling M17, transmitted to the LC parallel resonator 12 via the magnetic coupling M16, and LC parallel via the magnetic coupling M15. It is transmitted to the resonator 11. The signal transmitted to the LC parallel resonator 11 is transmitted to the input / output terminal P10 without going through magnetic coupling, and is output from the input / output terminal P10.

In the following, LC parallel resonators such as LC parallel resonators 11 and 14 are electrically connected to the input terminal to which the signal is input and the signal is transmitted to and from the input terminal without via magnetic coupling. (LC parallel resonator on the input side) and LC parallel that is electrically connected to the output terminal to which the signal from the input terminal is output and the signal is transmitted to and from the output terminal without magnetic coupling. The resonator (LC parallel resonator on the output side) is called an LC parallel resonator at both ends. Further, LC parallel resonators such as LC parallel resonators 12 and 13 that transmit signals from LC parallel resonators at both ends via magnetic coupling are arranged between the LC parallel resonators at both ends. It is called an LC parallel resonator.

The impedance of the signal path from the input terminal to the LC parallel resonator on the input side is the impedance of each signal path from the input terminal to the LC parallel resonator arranged between the LC parallel resonators at both ends, and from the input terminal. It is smaller than any of the impedances of the signal path leading to the LC parallel resonator on the output side.

In the bandpass filter 1, the impedance of the signal path from the input / output terminal P10 to the LC parallel resonator 11 is smaller than the impedance of each signal path from the input / output terminal P10 to the LC parallel resonators 12-14. The impedance of the signal path from the input / output terminal P100 to the LC parallel resonator 14 is smaller than the impedance of each signal path from the input / output terminal P100 to the LC parallel resonators 13 to 11.

When the two circuit elements are electrically connected, the two circuit elements are directly connected, and the two circuit elements are indirectly connected via another circuit element (for example, a capacitor). Both cases are included.

FIG. 2 is an external perspective view of the bandpass filter 1 of FIG. With respect to the coordinate axes, the X-axis and the Y-axis are orthogonal, and the Z-axis (stacking direction) is orthogonal to the X-axis and the Y-axis. The same applies to the coordinate axes shown in FIG.

As shown in FIG. 2, the bandpass filter 1 has, for example, a rectangular parallelepiped shape. The outermost surface of the bandpass filter 1 perpendicular to the stacking direction is the upper surface UF and the lower surface BF.

A direction identification mark DM is formed on the upper surface UF. Input / output terminals P10 and P100 and a ground terminal G120 are formed on the bottom surface BF. The ground terminal G120 forms a ground point GND. The input / output terminals P10 and P100 and the ground terminal G120 are, for example, LGA (Land Grid Array) terminals in which planar electrodes are regularly arranged on the bottom surface BF. The bottom surface BF is connected to a substrate (not shown).

FIG. 3 is an exploded perspective view showing an example of the laminated structure of the bandpass filter 1 of FIG. As shown in FIG. 3, the bandpass filter 1 is a laminated body in which a plurality of dielectric layers 121 to 132 are laminated in the Z-axis direction.

Capacitor conductor patterns 141 and 143 and line conductor patterns 142 are formed on the dielectric layer 121. The capacitor conductor pattern 141 is connected to the input / output terminal P10 by the via conductor pattern 181. The capacitor conductor pattern 141 is connected to the via conductor pattern 184. The line conductor pattern 142 is connected to the ground terminal G120 by the via conductor pattern 182. The capacitor conductor pattern 143 is connected to the input / output terminal P100 by the via conductor pattern 183. The capacitor conductor pattern 143 is connected to the via conductor pattern 187.

A ground conductor pattern 144 is formed on the dielectric layer 122. The ground conductor pattern 144 is connected to the line conductor pattern 142 by the via conductor patterns 185 and 186. The capacitor conductor pattern 141 and the ground conductor pattern 144 form the capacitor 102. The capacitor conductor pattern 143 and the ground conductor pattern 144 form the capacitor 110.

Capacitor conductor patterns 145 and 146 are formed on the dielectric layer 123. The ground conductor pattern 144 and the capacitor conductor pattern 145 form the capacitor 105. The ground conductor pattern 144 and the capacitor conductor pattern 146 form the capacitor 107.

Capacitor conductor patterns 147 to 149 are formed on the dielectric layer 124. The capacitor conductor pattern 147 is connected to the via conductor pattern 184 by the via conductor pattern 188. The capacitor conductor patterns 145 and 147 form the capacitor 103. The ground conductor pattern 144 and the capacitor conductor pattern 148 form the capacitor 113. The capacitor conductor pattern 149 is connected to the via conductor pattern 187 by the via conductor pattern 190. The capacitor conductor patterns 146 and 149 form the capacitor 108.

A capacitor conductor pattern 150 is formed on the dielectric layer 125. The capacitor conductor pattern 150 is connected to the capacitor conductor pattern 148 by the via conductor pattern 196. The capacitor conductor patterns 147 and 150 form the capacitor 111. The capacitor conductor patterns 149 and 150 form the capacitor 112. The connection portion between the capacitor conductor pattern 150 and the via conductor pattern 196 includes a connection point 118. The dielectric layer 124 on which the capacitor conductor pattern 148 is formed is arranged between the dielectric layer 122 on which the ground conductor pattern is formed and the dielectric layer 125 on which the capacitor conductor pattern 150 is formed.

Line conductor patterns 151 to 153 are formed on the dielectric layer 126. The line conductor pattern 151 is connected to the capacitor conductor pattern 147 by the via conductor pattern 188. The line conductor pattern 152 is connected to the ground conductor pattern 144 by the via conductor pattern 186. The line conductor pattern 153 is connected to the capacitor conductor pattern 149 by the via conductor pattern 190.

Line conductor patterns 154 to 156 are formed on the dielectric layer 127. The line conductor pattern 154 is connected to the line conductor pattern 151 by the via conductor patterns 188 and 197. The line conductor pattern 155 is connected to the line conductor pattern 152 by via conductor patterns 186, 194, 195. The line conductor pattern 156 is connected to the line conductor pattern 153 by via conductor patterns 190 and 198.

Line conductor patterns 157 to 159 are formed on the dielectric layer 128. The line conductor pattern 157 is connected to the line conductor pattern 154 by the via conductor patterns 188 and 197. The line conductor pattern 158 is connected to the line conductor pattern 155 by via conductor patterns 186, 194, 195. The line conductor pattern 159 is connected to the line conductor pattern 156 by via conductor patterns 190 and 198.

Line conductor patterns 160 to 163 are formed on the dielectric layer 129. The line conductor pattern 160 is connected to the line conductor pattern 157 by a via conductor pattern 197. The line conductor pattern 160 is connected to the ground conductor pattern 144 by the via conductor pattern 189.

The line conductor pattern 161 is connected to the capacitor conductor pattern 145 by the via conductor pattern 192. The line conductor pattern 161 is connected to the line conductor pattern 158 by the via conductor pattern 194.

The line conductor pattern 162 is connected to the capacitor conductor pattern 146 by the via conductor pattern 193. The line conductor pattern 162 is connected to the line conductor pattern 158 by the via conductor pattern 195.

The line conductor pattern 163 is connected to the line conductor pattern 159 by the via conductor pattern 198. The line conductor pattern 163 is connected to the ground conductor pattern 144 by the via conductor pattern 191.

Line conductor patterns 164 to 167 are formed on the dielectric layer 130. The line conductor pattern 164 is connected to the line conductor pattern 160 by the via conductor patterns 189 and 197. The line conductor pattern 165 is connected to the line conductor pattern 161 by the via conductor patterns 192 and 194. The line conductor pattern 166 is connected to the line conductor pattern 162 by the via conductor patterns 193 and 195. The line conductor pattern 167 is connected to the line conductor pattern 163 by the via conductor patterns 191, 198.

Line conductor patterns 168 to 171 are formed on the dielectric layer 131. The line conductor pattern 168 is connected to the line conductor pattern 164 by the via conductor patterns 189 and 197. The line conductor pattern 169 is connected to the line conductor pattern 165 by the via conductor patterns 192 and 194. The line conductor pattern 170 is connected to the line conductor pattern 166 by the via conductor patterns 193 and 195. The line conductor pattern 171 is connected to the line conductor pattern 167 by via conductor patterns 191, 198.

The via conductor pattern 184,188, the line conductor pattern 151,154,157, the via conductor pattern 197, the line conductor pattern 160,164,168, and the via conductor pattern 189 form the inductor 101.

The via conductor pattern 192, the line conductor pattern 161 and 165, 169, and the via conductor pattern 194 form the inductor 104.

The via conductor pattern 193, the line conductor pattern 162, 166, 170, and the via conductor pattern 195 form the inductor 106.

The via conductor pattern 187, 190, the line conductor pattern 153, 156, 159, the via conductor pattern 198, the line conductor pattern 163, 167, 171 and the via conductor pattern 191 form an inductor 109.

FIG. 4 is an equivalent circuit diagram of the bandpass filter 9 according to the comparative example. The equivalent circuit diagram of the bandpass filter 9 is an equivalent circuit diagram in which the capacitor 113 is removed from the equivalent circuit diagram of FIG. Other configurations are the same, so the description will not be repeated.

FIG. 5 is a diagram showing the insertion loss IL20 of the bandpass filter 1 of FIG. 1 and the insertion loss IL90 of the bandpass filter 9 of FIG. 4 together. It is assumed that the pass band of the bandpass filter 1 and 9 is the frequency band f41 to f42 (> f41). The frequencies f51 to f55 in which the attenuation poles are generated are higher in this order.

In FIG. 5, the attenuation amount (dB) on the vertical axis is a negative value. The larger the absolute value of the amount of attenuation, the larger the insertion loss. Insertion loss is an index showing the ratio of signals transmitted to other terminals of an electronic component among signals input to a certain terminal of an electronic component. The larger the insertion loss, the larger the proportion of the signal input to the electronic component that is lost inside the electronic component.

As shown in FIG. 5, in the insertion loss IL90, in the frequency band lower than the pass band, attenuation poles are generated at frequencies f51 (<f41) and f52 (<f41). In the frequency band higher than the pass band, attenuation poles are generated at frequencies f53 (> f42) and f55. By changing the capacitances of the capacitors 111 and 112 of FIG. 4, the frequency of the attenuation pole generated in the insertion loss IL90 can be changed. However, when the capacitances of the capacitors 111 and 112 are changed, the frequency of the decaying pole generated in the frequency band lower than the pass band and the frequency of the decaying pole generated in the frequency band higher than the pass band change to the same extent. In order to bring the frequency characteristics of the bandpass filter closer to the desired frequency characteristics, it is possible to change the decay poles that occur at frequencies higher than the passband without changing the frequencies of the decay poles that occur in the frequency band lower than the passband. May be needed.

Therefore, in the embodiment, the capacitor is connected between the connection point and the ground point of the two capacitors connected in series between the LC parallel resonators at both ends. With this capacitor, the frequency of the decaying pole generated in the frequency band higher than the passband can be changed with almost no change in the frequency of the decaying pole generated in the frequency band lower than the passband.

With reference to FIG. 5 again, in the insertion loss IL20, in the frequency band lower than the pass band, an attenuation pole is generated near the frequencies f51 and f52, similarly to the insertion loss IL90. In the frequency band higher than the pass band, an attenuation pole is generated near the frequency f53 as in the insertion loss IL90, and an attenuation pole is generated at the frequency f54 (> f42). According to the bandpass filter 1 of FIG. 1, by changing the capacitance of the capacitor 113, the frequency of the decaying electrode generated in the frequency band lower than the pass band is hardly changed, and the frequency is generated in the frequency band higher than the pass band. The frequency of the decaying electrode can be changed.

FIG. 6 is an equivalent circuit diagram of the bandpass filter 1A according to the modified example of the embodiment. The equivalent circuit diagram of the bandpass filter 1A is an equivalent circuit diagram in which capacitors 103 and 108 are removed from the equivalent circuit diagram of FIG. Other configurations are the same, so the description will not be repeated.

As described above, according to the bandpass filter according to the embodiment and the modified example, the frequency characteristic can be brought close to the desired frequency characteristic.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

1,1A, 9 bandpass filter, 11-14 LC parallel resonator, 101,104,106,109 inductor, 102,103,105,107,108,110,111-113 capacitor, 121-132 dielectric layer, 141,143,145-150 Capacitor conductor pattern, 142,151-171 Line conductor pattern, 144 Ground conductor pattern, 181-198 Via conductor pattern, DM direction identification mark, G120 ground terminal, P10, P100 input / output terminal.

Claims (2)

It ’s a bandpass filter,
1st terminal and 2nd terminal,
A first LC parallel resonator electrically connected to the first terminal at the first connection point,
A second LC parallel resonator electrically connected to the second terminal at the second connection point,
A third LC parallel resonator that magnetically couples with the first LC parallel resonator,
A second LC parallel resonator and a fourth LC parallel resonator magnetically coupled to the third LC parallel resonator,
It includes a first capacitor, a second capacitor, and a third capacitor.
The first LC parallel resonator includes a first inductor and a fourth capacitor connected in parallel between the first connection point and the ground point.
The second LC parallel resonator includes a second inductor and a fifth capacitor connected in parallel between the second connection point and the ground point.
The first capacitor and the second capacitor are connected in series between the first connection point and the second connection point.
The third capacitor is connected between the grounding point and the third connection point of the first capacitor and the second capacitor .
The bandpass filter is formed as a laminate of a plurality of dielectric layers, and is formed.
The plurality of dielectric layers are
The first dielectric layer on which the ground conductor pattern is formed,
The second dielectric layer on which the first capacitor conductor pattern is formed, and
It includes a third dielectric layer on which a second capacitor conductor pattern connected to the first capacitor conductor pattern is formed.
The second dielectric layer is arranged between the first dielectric layer and the third dielectric layer.
The second capacitor conductor pattern includes the third connection point.
The third capacitor is a bandpass filter formed from the first capacitor conductor pattern and the ground conductor pattern. A sixth capacitor connected between the third LC parallel resonator and the first connection point,
A seventh capacitor connected between the fourth LC parallel resonator and the second connection point is further provided.
The third LC parallel resonator includes a third inductor and an eighth capacitor connected in parallel, and is connected between the sixth capacitor and the grounding point.
The bandpass filter according to claim 1, wherein the fourth LC parallel resonator includes a fourth inductor and a ninth capacitor connected in parallel, and is connected between the seventh capacitor and the grounding point.

Images