JPH0834399B2 - Bandpass filter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a band formed by magnetically coupling two resonance circuits in which an inductor and a capacitor are connected in parallel between a hot terminal and a ground terminal, between the inductors. Regarding the pass filter.

2. Description of the Related Art Conventional Techniques and Problems Thereof is generally known as an equivalent circuit of the bandpass filter shown in FIG. That is, hot terminal
Resonant circuit Q1 consisting of inductor L1 and capacitor C2 connected in parallel between H1 and ground terminal A1, and resonant circuit Q2 consisting of inductor L2 and capacitor C4 connected in parallel between hot terminal H2 and ground terminal A2. The circuit configuration is such that the inductors L1 and L2 are coupled to each other with a magnetic coupling degree M. In addition,
In the figure, C1 and C3 are capacitors for adjusting the input / output impedance, and L3 and L4 are the inductance components of the connecting portions connecting the resonant circuits Q1 and Q2 to the ground terminals A1 and A2.

FIG. 14 is a frequency characteristic diagram of a bandpass filter having the above equivalent circuit. As can be seen from this figure, in the conventional bandpass filter, the attenuation characteristic is gentle on both sides of the center frequency, that is, there is no pole that clearly defines both sides of the passband. However, there was a frequency range where the amount of attenuation was insufficient.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a bandpass filter that can secure a sufficient amount of attenuation as a frequency characteristic in which poles exist on both sides of a center frequency.

Means for Solving the Problems In order to achieve the above object, in a bandpass filter according to the present invention, two resonance circuits in which an inductor and a capacitor are connected in parallel are magnetically coupled to each other, and the ground side of both resonance circuits is It is connected to the ground terminal, and the hot side of one resonance circuit and the input hot terminal are connected with an impedance adjustment capacitor, and the hot side of the other resonance circuit and the output hot terminal are connected with an impedance adjustment capacitor. A line between the one impedance adjusting capacitor and the input hot terminal and a line between the other impedance adjusting capacitor and the output hot terminal are connected by a pole forming capacitor. There is.

Effect According to the configuration of the bandpass filter of the present invention, the electric signal input from the input hot terminal reaches the output hot terminal through the two resonance circuits in which the inductors are magnetically coupled, and the pole forming capacitor is formed. The signal passing through the resonance circuit and the signal passing through the pole-forming capacitor have opposite phases at a specific frequency around the center frequency of the pass band and Poles are formed at both ends of the frequency.

Embodiment FIG. 1 is an exploded perspective view showing an embodiment of the bandpass filter according to the present invention, and FIG. 2 is a front sectional view thereof. This filter is formed by appropriately stacking a green sheet made of unfired dielectric material and an electrode layer made of a conductive material on one side of the green sheet by printing or the like. It is manufactured by firing a connection terminal formed by printing or the like.

A protective layer 1 is formed at the bottom in the thickness direction, and shield electrode layers 2a and 2b, a dielectric layer 3, a printed coil 4 (consisting of 4a, 4b and 4c), a dielectric layer 5 and a pole are formed on the protective layer 1. Capacitor electrode layer 6, capacitor forming layer 7, input / output impedance adjusting capacitor electrode layers 8a, 8b, input / output impedance adjusting capacitor forming layer 9, resonance circuit capacitor electrode layers 10a, 10b, resonance circuit capacitor forming layer 1
1, the shield electrode layers 12a and 12b, the frequency adjusting capacitor forming layer 13, the trimming electrode layers 14a and 14b, and the protective layer 15 are sequentially formed, and the side surface has eight connecting terminals 16a having a U-shaped cross section. ~ 16h is formed.

As shown in FIG. 3, the printed coil 4 is provided with three printed coils 4a, 4b, 4c, and both ends of the two resonant circuit printed coils 4a, 4b are hot (input / output) connection terminals 16b, 16c is connected to the ground connection terminals 16e and 16h, and the two print coils 4a and 4b are connected to each other with the magnetic coupling degree M with the hot side being close to each other, and the ground side is the pole forming print coil 4c. It is connected.

Shield electrode layer 12 on the upper side of the print coil 4
As shown by the solid lines in FIG. 4, a and 12b are formed so as to be separated from each other, and the resonance circuit capacitor electrode layers 10a and 10b on the lower side thereof and on the upper side of the print coil 4 are the same. As shown by the broken line in the figure, it faces the shield electrode layers 12a and 12b.

One resonance circuit capacitor electrode layer 10a is connected to the input connection terminal 16b to which one end side of the print coil 4a is connected, and the shield electrode layer 12a facing this capacitor electrode layer 10a is the other end side of the print coil 4a. The resonance circuit capacitor forming layer 11 made of a dielectric material is connected to the connected earth connection terminal 16e, and is provided between the two electrode layers 12a and 10a.
, The resonance circuit capacitor C2 is formed. Then, the capacitor C2 and the printed coil 4a
The inductor L1 formed in 1 is connected via the connection terminals 16b and 16e to form an LC resonance circuit. The resonance frequency of this LC resonance circuit is opposed to the shield electrode layer 12a via the frequency adjustment capacitor forming layer 13 and forms a frequency adjustment capacitor C2x with the shield electrode layer 12a. The trimming electrode layer 14a is made variable by removing the protective layer 15 and scraping it off. The shield electrode layers 2a and 2b below the printed coil 4 are also provided with 2 as shown by the solid line in FIG.
Although it is composed of two separated pieces, they may be integrated without separation.

The other resonance circuit capacitor electrode layer 10b is connected to the input connection terminal 16c to which one end side of the print coil 4b is connected, and the shield electrode layer 12b facing the capacitor electrode layer 10b is the other end side of the print coil 4b. The resonance circuit capacitor forming layer 11 made of a dielectric material is connected to the connected earth connection terminal 16h, and is provided between the two electrode layers 12b and 10b.
, The resonance circuit capacitor C4 is formed. Then, the capacitor C4 and the printed coil 4b
The inductor L2 formed in 1 is connected via the connection terminals 16c and 16h to form an LC resonance circuit. The resonance frequency of this LC resonance circuit is opposed to the shield electrode layer 12b via the frequency adjustment capacitor forming layer 13 and forms a frequency adjustment capacitor C4x with the shield electrode layer 12b. The trimming electrode layer 14b is made variable by subjecting the protective layer 15 to removal and shaving.

Between the print coil 4b forming the LC resonance circuit and the print coil 4a forming the LC resonance circuit described above,
It is connected by the above-mentioned pole forming print coil 4c. The inductor of the print coil 4c is L5.

A fourth electrode is provided below the capacitor electrode layers 10a and 10b, which are one of the electrodes forming the capacitors C2 and C4 for the resonance circuit.
As shown by the alternate long and short dash line in the figure, L-shaped input / output impedance adjusting capacitor electrode layers 8a and 8b are formed apart from each other, and the input impedance adjusting capacitor layer 8a and the resonance circuit capacitor electrode layer 10a are formed. In between, the input impedance adjusting capacitor C1 is formed via the input / output impedance adjusting capacitor forming layer 9 made of a dielectric material, and one input capacitor electrode layer 8a forming this capacitor C1 is connected to the input connecting terminal 16a. It is connected.

On the other hand, output impedance adjustment capacitor electrode layer 8b
Between the resonance circuit capacitor electrode layer 10b and the resonance circuit capacitor electrode layer 10b, the output impedance adjusting capacitor C3 is formed via the input / output impedance adjusting capacitor forming layer 9 made of a dielectric material. The capacitor electrode layer 8b is connected to the output connection terminal 16d.

Below the above-mentioned input / output impedance adjusting capacitor electrode layers 8a and 8b, a capacitor forming layer 7 is provided.
One pole forming capacitor electrode layer 6 is formed, and both sides of this capacitor electrode layer 6 are opposed to the capacitor electrode layers 8a and 8b, and pole forming capacitors C5 and C5 are formed. Therefore, input / output capacitor electrode layers 8a, 8b
Are connected to the pole-forming capacitor electrode layer 6 via capacitors C5 and C5 formed between both ends of the pole-forming capacitor electrode layer 6.

Therefore, as shown in FIG. 5, the band-pass filter having the above-mentioned configuration has the first inductor L1 and the capacitor C2.
In contrast to the basic configuration in which the LC resonance circuit Q1 and the second LC resonance circuit Q including the inductor L2 and the capacitor C4 are coupled with a magnetic coupling degree M between the inductors L1 and L2,
The frequency adjustment capacitors C2x and C4x are connected in parallel with C2 and C4. Furthermore, between the two resonant circuits Q1 and Q2, the hot input / output connection terminal side, in this example, the input / output impedance A pole forming capacitor C5 is connected in parallel between the adjusting capacitors C1 and C3, and a pole forming inductor L5 is connected between the two resonance circuits Q1 and Q2 between the ground connection terminals. It has a circuit configuration. Further, this filter has a structure in which both sides are shielded by the shield electrode layers 2a, 2b, 12a, 12b. Note that L3 and L4 are the inductance of the ground connection terminal 16e connected to the shield electrode layer 12a and the ground connection terminal 16h connected to the shield electrode layer 12b.

FIG. 6 is a frequency characteristic diagram of the bandpass filter having this configuration, where the solid line shows the attenuation factor and the broken line shows the insertion loss. As understood from this figure, in the present invention, the poles P1 and P2 can be formed on both sides of the center frequency f ₀ .

FIG. 7 is a frequency characteristic diagram when the trimming electrode layers 14a and 14b of the filter shown in FIG. 1 are completely removed by using a laser or the like (a solid line is an attenuation factor, a broken line is an insertion loss). As can be understood from this figure, the trimming electrode layer 14
By removing a and 14b, the center frequency f ₀ can be increased by about 18 MHz from the state of FIG. 6 in the presence of the poles P1 and P2.

FIG. 8 is an exploded perspective view showing another embodiment of the present invention, and FIG.
The drawing is a front sectional view thereof, FIG. 10 is a plan view mainly showing an inductor portion, and FIG. 11 is a plan view showing a capacitor portion. In this filter, the hot side with the input / output terminals is on the right and the ground side with the ground terminals is on the left, that is, it is the reverse of that of FIG.

The inductor (L1) of one resonance circuit which constitutes this filter is one resonance coil print coil 4a 'among the three print coils 4a', 4b ', 4c' formed as shown in FIG. The resonance circuit capacitor (C2) is composed of a shield electrode layer 12a 'shown by a solid line in FIG. 10 on the upper side of the printed coil 4a', and a resonance circuit capacitor forming layer 11 made of a dielectric material therebetween. ′ And a resonance circuit capacitor electrode layer 10a ′ formed as shown by the broken line in FIG. One end of the resonance circuit print coil 4a 'is connected to the resonance circuit capacitor electrode layer 10a' via a hot connection terminal 16a ', and the other end of the resonance circuit print coil 4a' is connected to a ground connection terminal 16a.
It is connected to the shield electrode layer 12a 'through
It forms a resonant circuit. The resonance frequency of this LC resonance circuit is opposed to the shield electrode layer 12a 'via the frequency adjustment capacitor forming layer 13 and is provided between the shield electrode layer 12a' and the shield electrode layer 12a 'for frequency adjustment capacitor C2x'. The trimming electrode layer 14a 'for forming is made variable by removing the protective layer 15 and scraping it off.

The inductor (L2) of the other resonance circuit has three printed coils 4a ', 4b', 4c 'formed as shown in FIG.
Of the resonant circuit printed coil 4b ', and the capacitor (C4) of the resonant circuit is located between the shield electrode layer 12b' shown by the solid line in FIG. 10 and above the printed coil 4b '. And a resonance circuit capacitor forming layer 11 'made of a dielectric material and a resonance circuit capacitor electrode layer 10b' formed as shown by a broken line in the figure. One end of the resonance circuit print coil 4b 'is connected to the resonance circuit capacitor electrode layer 10b' through a hot connection terminal 16d ', and the resonance circuit print coil 4b' is formed.
The other end of is connected to the shield electrode layer 12b 'through a grounding connection terminal 16g', forming an LC resonance circuit. The resonant frequency of this LC resonant circuit is
Between the b'and the frequency adjustment capacitor forming layer 13
The trimming electrode layer 14b ', which faces the shield electrode layer 12b' and forms the capacitor C4x 'for frequency adjustment with the shield electrode layer 12b', can be changed by removing the protective layer 15 and scraping it off. It has been done.

The print coil 4b 'forming the LC resonance circuit and the print coil 4a' forming the LC resonance circuit described above are connected by a pole forming print coil 4c '(inductor L5) on the side of the ground connection terminal. (See Figure 10). Print coils 4a 'and 4b' of both resonance circuits
A magnetic coupling degree M is used to connect between and.

In FIG. 11, 8a ′ and 8b ′ indicated by alternate long and short dash lines are input / output impedance adjusting capacitor electrode layers, and the capacitor electrode layers 8a ′ and 8b ′ and the resonance circuit capacitor electrode layers 10a ′ and 10b ′. Between the input and output via the input / output impedance adjusting capacitor forming layer 9'made of a dielectric material.
Form capacitors C1 and C3 for output impedance adjustment. Capacitors for adjusting these input and output impedances
C1 and C3 are connected by a pole-forming capacitor electrode layer 6'formed with both ends facing each other.

Also in the filter configured as described above, the frequency characteristic is such that the poles P1 and P2 exist on both sides of the center frequency as shown by the solid line in FIG. The broken line in the figure shows the insertion loss.

In the above two embodiments, the input / output impedance adjusting capacitors C1 and C3 are provided near the input / output terminals, but the present invention is not limited to this, and the input / output impedance adjusting capacitor is omitted. Of course, it can be applied to the one having the above configuration.

Further, in the above two embodiments, the hot side of the two resonance circuits is connected by the pole forming capacitor and the ground side is connected by the pole forming inductor. However, the present invention is not limited to this, and two resonance circuits are provided. The hot side of the resonance circuit may be connected by a pole forming inductor and the ground side may be connected by a pole forming capacitor.

Further, in the above two embodiments, the input / output impedance adjusting capacitor electrode layer 8a and the trimming electrode layer 14a are formed on the shield electrode layer 10a side (upper side) where the resonance circuit capacitor electrode layer 10a and the like are provided. However, the shield electrode layer 2a may be formed on the same side (lower side).

As described above, according to the bandpass filter of the present invention, the electric signal input from the input hot terminal reaches the output hot terminal through the two resonance circuits in which the inductors are magnetically coupled, and the pole signal is generated. In relation to the output hot terminal by the bypass path through the forming capacitor,
Since the signal passing through the resonant circuit and the signal passing through the pole forming capacitor have opposite phases at specific frequencies around the center frequency of the pass band, it is possible to form poles at both ends of the center frequency. Excellent filter characteristics can be realized.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a bandpass filter according to the present invention, FIG. 2 is a front sectional view thereof, FIG. 3 is a plan view mainly showing an inductor portion of the filter, and FIG. FIG. 5 is a plan view showing a capacitor portion of the filter, FIG. 5 is an equivalent circuit diagram of the filter of FIG. 1, FIG. 6 is a frequency characteristic diagram of the filter, and FIG. 7 is a frequency when all trimming electrodes of the filter are removed. FIG. 8 is a characteristic view, FIG. 8 is an exploded perspective view showing another embodiment of the present invention, FIG. 9 is a front sectional view thereof, FIG. 10 is a plan view mainly showing an inductor portion of the filter, and FIG. 12 is a plan view showing the capacitor portion of FIG. 12, FIG. 12 is a frequency characteristic diagram of the filter, FIG. 13 is an equivalent circuit diagram of a conventional bandpass filter, and FIG. 14 is a frequency characteristic diagram of the filter of FIG. 4a, 4b, 4a ′, 4b ′ …… Print coil (inductor), 4
c, 4c '... Pole-forming printed coil (pole-forming inductor), 6,6' ... Pole-forming capacitor electrode layer, 10a, 10b, 10a ', 10b' ... Resonant circuit capacitor electrode layer, 12a , 12b, 12a ', 12b' ... Shield electrode layer.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Ken Tonegawa 2-10-10 Tenjin, Nagaokakyo City, Kyoto Prefecture Murata Manufacturing Co., Ltd. (56) Reference JP-A-63-181514 (JP, A)

Claims (1)

[Claims] 1. Two resonance circuits in which an inductor and a capacitor are connected in parallel are magnetically coupled to each other, the ground side of both resonance circuits is connected to a ground terminal, and the hot side of one resonance circuit and the input hot terminal. Is a capacitor for impedance adjustment, the hot side of the other resonance circuit and the output hot terminal are connected by an impedance adjustment capacitor, and the line between the impedance adjustment capacitor and the input hot terminal is connected. A bandpass filter characterized in that a pole forming capacitor is connected between the other impedance adjusting capacitor and the line between the output hot terminals.