JP2001111302A - Low pass filter and electronic equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low pass filter that both transmission and reflection are reduced in an attenuating region and the power can be absorbed inside. SOLUTION: Inside a substrate 2 made of dielectric materials whose dielectric tangents in frequencies 1 MHz are >=0.001, two ground layers 3 and 5 and a line layer 4 interposed between the ground layers are included. In this case, ground electrodes 3a and 5a are formed over almost the whole face of the ground layers 3 and 5, and meandering line 4a is formed on the line layer 4 so that strip lines in a triplate structure can be constituted as a whole. Then, the both ends of the line 4a are connected with an input terminal 6 and an output terminal 7. In this case, the dielectric tangents of the dielectric materials are set larger than those of dielectric materials for general strip lines. Therefore, as the frequencies of a signal become higher, attenuating amounts due to the dielectric loss are increased so that a low pass filter that reflection in the attenuating area is reduced can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-pass filter and an electronic device using the same, and more particularly to a low-pass filter used for suppressing a harmonic component of a mobile communication device or a device using a high-frequency digital signal and an electronic device using the same. Related to the device.

[0002]

2. Description of the Related Art Generally, a low-pass filter is used for harmonic noise of a communication device and a harmonic of a high-frequency oscillator, and a noise filter is used for removing a harmonic of a digital circuit.

In a low-pass filter configured by combining general inductance components and capacitance components, a signal in a pass band (pass frequency band) is passed with low loss and is not reflected as much as possible. On the other hand, the signal in the attenuation band (non-pass frequency band) is configured to reflect most of the signal and pass through as little as possible. Therefore, there is almost no energy consumed as a loss inside the low-pass filter in both the pass band signal and the attenuation band signal.

[0004] Further, since the noise filter has a resistance component inside, the energy of the signal in the attenuation region is attenuated and output because part of the energy is consumed internally.

[0005]

However, in a low-pass filter formed by combining an inductance component and a capacitance component, almost all signals are reflected in an attenuation band (non-pass band) because the internal loss is small. Then, there is a problem that these reflected signals cause unnecessary radiation in the circuit.

In the noise filter, when the input impedance is set to be the same as the characteristic impedance of the connection partner, the internal resistance component becomes equal to the characteristic impedance of the connection partner. Only 50% can be absorbed internally, the remaining 50%
Is output. For this reason, there is a problem that the harmonic cannot be sufficiently attenuated. Then, even if the internal resistance component is increased or decreased, the reflection due to the mismatch increases, and the absorption inside the filter decreases. Further, there is a problem that an increase in reflection causes unnecessary radiation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-pass filter capable of reducing both transmission and reflection in an attenuation region and absorbing its power inside, and an electronic device using the same. .

[0008]

To achieve the above object, a low-pass filter according to the present invention has a frequency of 1M.
Providing a plurality of ground layers with a dielectric tangent at Hz sandwiching a dielectric material of 0.001 or more, forming a ground electrode on the ground layers, and providing one or more line layers between the plurality of ground layers; It is characterized in that a linear line is formed on the line layer.

Further, the low-pass filter according to the present invention is characterized in that the low-pass filter has a plurality of the line layers and connects the lines formed on the plurality of the line layers to each other.

The low-pass filter according to the present invention is characterized in that the line formed in the line layer has a spiral shape.

Further, in the low-pass filter according to the present invention, the lines formed spirally on the adjacent line layers have the same central axis and the same winding direction.

Further, in the low-pass filter according to the present invention, the line is self-resonant and has a pole periodically generated by the self-resonance.

Further, an electronic device according to the present invention uses any one of the low-pass filters described above.

With such a configuration, in the low-pass filter of the present invention, it is possible to increase the loss inside the filter in the attenuation region and attenuate both the transmission signal and the reflection signal.

Further, in the electronic device according to the present invention, unnecessary harmonic signals can be reduced, and generation of unnecessary radiation inside the electronic device can be reduced.

[0016]

1 to 3 show one embodiment of a low-pass filter according to the present invention. FIG. 1 is a perspective view of a low-pass filter according to an embodiment of the present invention, and FIG. 2 is a plan view of the low-pass filter of FIG. 1 and 2 are partially see-through views. FIG. 3 is a sectional view taken along line AA of the low-pass filter shown in FIG.

1 to 3, a low-pass filter 1 has a base 2. Here, the material constituting the base 2 has a dielectric loss tangent at a frequency of 1 MHz of 0.00.
One or more dielectric materials are used. Such a dielectric material can be realized by, for example, ceramics mixed with metal powder such as copper powder.

The base 2 is a laminated multilayer substrate having two ground layers 3 and 5 therein, and one line layer 4 between the ground layers 3 and 5. On the ground layers 3 and 5, ground electrodes 3a and 5a are formed over almost the entire surface, respectively. However, the display is omitted in FIG. Also,
In the line layer 4, the line 4a is formed in a substantially meandering shape. As a result, the line 4a and the ground electrodes 3a and 5a
Thus, a strip line having a triplate structure is formed. In this case, the characteristic impedance of the strip line is determined by the relative permittivity of the dielectric material, the width of the line 4a, and the distance between the line 4a and the two ground electrodes 3a and 5a. Therefore, the characteristic impedance of the strip line can be determined according to the characteristic impedance (for example, 50 ohms) of the connection partner of the low-pass filter 1 (for example, a signal processing circuit or the like).

On the end face of the base 2, there are formed an input terminal 6 and an output terminal 7 connected to both ends of the line 4a, and six ground terminals 8 connected to both the ground electrodes 3a and 5a. . Here, the input terminal 6 and the output terminal 7 are insulated from the ground electrodes 3a and 5a.

The low-pass filter 1 configured as described above
, The attenuation due to the dielectric loss of the strip line is αd = (27.3 / λg) × tan δ [dB / m] where λg = λ / sqrt (εr). Here, λg represents the wavelength of the signal in the dielectric material, λ represents the wavelength of the signal in vacuum, εr represents the relative permittivity of the dielectric material, and tanδ represents the dielectric loss tangent of the dielectric material. . Further, λ and λg are inversely proportional to the frequency of the signal.
nδ and εr may also have frequency dependence. From this equation, it can be seen that in a stripline, basically, the higher the frequency of the signal, the greater the amount of attenuation due to dielectric loss, and a low-pass filter with less reflection in the attenuation region. The dielectric loss tangent of a dielectric material used for a general strip line is about 0.0005 (at 1 MHz), whereas the dielectric loss tangent of the low-pass filter of the present invention is 0.001 (at 1 MHz) or more. , This tendency becomes remarkable, and a low-pass filter with less reflection in the attenuation region can be realized.

Further, since the inside of the low-pass filter has a strip line structure, the input impedance and the output impedance can be freely designed by changing the width of the line, the interval between the line and the ground electrode, and the like. In addition, unnecessary reflection of signals can be reduced even in a pass band, and unnecessary radiation can be reduced.

Here, FIGS. 4 to 6 show that the dielectric loss tangent at 1 MHz is 0.0008, 0.0013, 0.00.
The frequency characteristics of a low-pass filter made using 16 materials A, B, and C are shown. 4 to 6
, The horizontal axis indicates frequency, and the vertical axis indicates the reflection characteristics (S1
1, reflection loss) and transmission characteristics (S21, insertion loss). S11 is 10 dB on one scale, and S21 is 1 dB on one scale. However, in FIG. 6 only, S21 is 2 dB on one scale. The input and output impedance of each low-pass filter is the impedance of the measurement system.
It is set to be ohm.

As can be seen by comparing FIGS. 4 to 6,
In the material A having a dielectric tangent of 0.0008, S21 is not so large, but in the material B having a dielectric tangent of 0.0013, it is slightly larger, and in the material C having a dielectric tangent of 0.0016, it is significantly larger. Also, S11 is about 10 dB or more, which indicates that energy is consumed inside the filter. Specifically, for example, at 9.6 GHz, the material A has S11 = −13 dB and S21 = −2.6 dB, and the absorption amount is about 40%. On the contrary. S for material B
11 = −16 dB, S21 = −3.6 dB, the absorption amount becomes about 54%, and in the material C, S11 = −7 dB, S21 =
At -10 dB, the amount of absorption is about 70%, and more than 50% of the energy is absorbed inside the filter.
Accordingly, the dielectric loss tangent of the dielectric material is set to 0.001 (1 MH).
It can be seen that by setting z) or more, a low-pass filter with little reflection in the attenuation region and a large amount of attenuation can be realized.

FIGS. 7 and 8 show another embodiment of the low-pass filter of the present invention. FIG. 7 is a plan view of a part of a low-pass filter according to another embodiment, and FIG. 8 is a cross-sectional view of the low-pass filter shown in FIG. The perspective views of the low-pass filter shown in FIGS.
It is omitted here. 7 and 8, FIG.
The same or equivalent parts as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

In FIGS. 7 and 8, the low-pass filter 10 has another ground layer 12 between the ground layers 3 and 5. The line layer 11 is provided between the ground layers 3 and 12, and the line layer 13 is provided between the ground layers 12 and 5.
have. The line layer 11 has a spiral line 11 a having one end connected to the input terminal 6. On the ground layer 12, a ground electrode 12a is formed over almost the entire surface. In the line layer 13, a line 13a having a straight line and one end connected to the output terminal 7 is formed. The other end of the line 11a and the other end of the line 13a are connected via a via hole 14. Note that the ground electrode 12a is not formed at a portion where the via hole 14 penetrates, and both are insulated.

The low-pass filter 1 thus configured
0, the ground electrodes 3a and 12a and the line 1
Although the strip line composed of the strip line 1a, the ground electrodes 5a and 12a, and the strip line composed of the line 13a are formed in two layers, the low pass filter 1 shown in FIGS.
Are exactly the same as those described above, and have the same effect. Moreover, in the low-pass filter 10, the line 1
1a is formed in a spiral shape, so that the line 11
The inductance component of “a” increases, and the choke effect of the inductance component makes it difficult to pass a high-frequency signal, so that the amount of attenuation in the attenuation region can be further increased.

FIGS. 9 and 10 show still another embodiment of the low-pass filter of the present invention. FIG. 9 is a plan view of a part of a low-pass filter according to still another embodiment, and FIG. 10 is a cross-sectional view taken along line CC of the low-pass filter shown in FIG. The perspective views of the low-pass filters shown in FIGS. 9 and 10 are omitted here. 9 and 10, the same or equivalent parts as those in FIGS. 1 to 3 are denoted by the same reference numerals, and description thereof will be omitted.

9 and 10, the low-pass filter 20 has two line layers 21 and 22 adjacent between the ground layers 3 and 5. The line layer 21 has a spiral shape, one end of which is connected to the input terminal 6.
a is formed. The line layer 22 has a spiral line 22 a having one end connected to the output terminal 7. The other end of the line 21a and the other end of the line 22a are connected via a via hole 23.

FIG. 11 shows only the line layers 21 and 22 extracted because they are difficult to understand in FIG. FIG.
FIG. 11A shows the line layer 21, and FIG. 11B shows the line layer 22. As shown in FIG. 11, the line 21a and the line 22a are wound in the same direction with the via hole 23 as the same central axis.

The low-pass filter 2 configured as described above
At 0, since the spiral lines 21a and 22a are wound in the same direction between the ground electrodes 3a and 5a, the lines 21a and 22a are magnetically coupled, and
The inductance components of 1a and the line 22a are further increased. Therefore, the line 21a and the line 22a
The choke effect due to the inductance component described above further increases, and attenuation due to dielectric loss is added to the choke effect, so that the attenuation characteristics in the attenuation region can be further increased.

Further, since the line 21a and the line 22a are in a positional relationship substantially opposed to each other, a capacitance component is generated therebetween. This capacitance component self-resonates with the inductance components of the line 21a and the line 22a. Since these inductance components and capacitance components are generated as distributed constants, they self-resonate periodically, and periodic poles are generated in reflection characteristics and transmission characteristics, thereby further reducing the attenuation characteristics in the attenuation region. It is getting bigger.

Even if there is only one line layer, a capacitance component is generated in the line itself by, for example, a meandering or spiral shape, and the same effect as that of the low-pass filter 20 can be obtained. However, since the resonance frequency is increased due to the small capacitance value and the period thereof is also widened, it is not clearly shown in FIGS.

FIG. 12 shows the frequency characteristics of the low-pass filter 20 made of the material C having a dielectric loss tangent of 0.0016 at 1 MHz. 12, the horizontal axis indicates frequency, and the vertical axis indicates reflection characteristics (S11, reflection loss) and transmission characteristics (S21, insertion loss). S11 is 10 dB on one scale, and S21 is 5 dB on one scale.
B. The input / output impedance of each low-pass filter is set to be 50 ohm, which is the impedance of the measurement system.

As can be seen by comparing FIG. 12 with FIG. 6, which is a characteristic of a low-pass filter made of the same material C, S21 in the attenuation region is significantly reduced by increasing the inductance component of the line. . From this, it can be seen that by increasing the inductance component, a low-pass filter with less reflection in the attenuation region and a larger attenuation can be realized.

In the low-pass filter 20,
Although two adjacent line layers 21 and 22 are provided between the ground layers 3 and 5, three or more adjacent line layers are provided, and spiral lines formed on the respective line layers are formed by spiral lines. They may be connected to each other and magnetically coupled.

In each of the above-described embodiments, the portion where the line layer is formed between the two ground layers is regarded as one layer, and is formed as one layer (the low-pass filters 1 and 2 shown in FIGS. 1 to 3). And the low-pass filter 10) shown in FIGS. 7 and 8 or the two layers (the low-pass filter 20 shown in FIGS. 9 to 11). However, the number of layers may be three or more. Is played.

In each of the above embodiments, the outermost ground layers (ground layers 3 and 5) are formed inside the base 2, but they may be formed on the top and bottom surfaces of the base 2, respectively. Not something.

The low-pass filter 1 has one input terminal, one output terminal, and one line connecting the two terminals. However, the low-pass filter 1 has a plurality of input terminals and output terminals and a plurality of lines connecting them. You may have it.

Further, the line formed on the line layer is not limited to a meandering or spiral shape, but may have any shape including a linear shape.

FIG. 13 shows an embodiment of the electronic device of the present invention. In FIG. 13, an electronic device 30 shows a frequency conversion device used for an output stage or the like of a wireless communication device.
Input terminal 31, amplifier 32, low-pass filter 1 of the present invention, local oscillator 33, mixer 34, band-pass filter 3
5, an amplifier 36, and an output terminal 37. Here, the input terminal 31 is connected to one input of the mixer 34 via the amplifier 32 and the low-pass filter 1 in this order.
The local oscillator 33 is connected to the other input of the mixer 34. The output of the mixer 34 is connected to an output terminal 37 via a band-pass filter 35 and an amplifier 36 in this order.

In the electronic device 30 configured as described above, the signal input from the input terminal 31 is amplified by the amplifier 32, unnecessary harmonics are removed by the low-pass filter 1, and the signal from the local oscillator 33 is output by the mixer 34. The frequency is converted by multiplying the signal by the bandpass filter 35, and only the required frequency is extracted by the band-pass filter 35, amplified by the amplifier 36, and output from the output terminal 37. Here, since the low-pass filter 1 of the present invention is provided on the output side of the amplifier 32, unnecessary harmonics generated in the amplifier 32 can be efficiently removed. In addition, since there is little signal reflection at the low-pass filter 1, unnecessary radiation hardly occurs between the amplifier 32 and the low-pass filter 1.

As described above, in the electronic device 30, the use of the low-pass filter of the present invention can reduce the generation of harmonics and unnecessary radiation.

In the electronic device 30, the case where the low-pass filter of the present invention is used for an analog circuit that handles high-frequency signals has been described. May be used,
The same operation and effect can be obtained.

[0044]

According to the low-pass filter of the present invention, a plurality of ground layers are provided with a dielectric material having a dielectric loss tangent of 0.001 or more at a frequency of 1 MHz, and a ground electrode is formed thereon. By providing one or more line layers between them and forming a linear line in the line layer, the internal loss due to dielectric loss increases,
The amount of attenuation can be increased by reducing reflection in the attenuation region.

Further, by having a plurality of line layers and connecting the lines formed on the plurality of line layers to each other,
By further increasing the internal loss, reflection and transmission in the attenuation region can be further reduced.

Further, by forming the line formed in the line layer into a spiral shape, the inductance component is increased, and the amount of attenuation in the attenuation region can be further increased.

Further, by making the spiral direction of the line formed in the adjacent line layer the same as that of the center axis, the inductance component is further increased, and the attenuation in the attenuation region can be further increased. .

In addition, since the line has self-resonance and thus has a periodically generated pole, the amount of attenuation in the attenuation region can be further increased.

According to the electronic device of the present invention, the use of the low-pass filter of the present invention can reduce the generation of harmonics and unnecessary radiation.

[Brief description of the drawings]

FIG. 1 is a partially transparent perspective view showing one embodiment of a low-pass filter of the present invention.

FIG. 2 is a plan view of the low-pass filter of FIG.

FIG. 3 is a sectional view taken along line AA of the low-pass filter of FIG. 2;

FIG. 4 is a diagram showing reflection characteristics and transmission characteristics of the low-pass filter of FIG.

FIG. 5 is another diagram showing reflection characteristics and transmission characteristics of the low-pass filter of FIG. 1;

FIG. 6 is still another diagram illustrating the reflection characteristics and the transmission characteristics of the low-pass filter of FIG. 1;

FIG. 7 is a plan view showing another embodiment of the low-pass filter of the present invention.

8 is a cross-sectional view of the low-pass filter of FIG. 7 taken along line BB.

FIG. 9 is a plan view showing still another embodiment of the low-pass filter of the present invention.

FIG. 10 is a cross-sectional view of the low-pass filter of FIG. 9 taken along line CC.

FIG. 11 is a diagram illustrating a line layer of the low-pass filter of FIG. 9;

12 is a diagram showing reflection characteristics and transmission characteristics of the low-pass filter of FIG.

FIG. 13 is a block diagram showing one embodiment of the electronic device of the present invention.

[Explanation of symbols]

 1, 10, 20: low-pass filter 2: base 3, 5, 12: ground layer 3a, 5a, 12a: ground electrode 4, 11, 13, 21, 22: line layer 4a, 11a, 13a, 21a, 22a: line 6 input terminal 7 output terminal 8 ground terminal 14, 23 via hole 30 electronic device

Continued on the front page (72) Inventor Haruhumi Bandai 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto F-term in Murata Manufacturing Co., Ltd. (Reference) 5J006 HB03 HB15 HD07 HD11 JA03 LA05 LA11 LA12 5J024 AA01 BA11 CA09 DA21 DA29 DA32 EA01 EA08

Claims (6)

[Claims] 1. The dielectric loss tangent at a frequency of 1 MHz is 0.
A plurality of ground layers are provided with 001 or more dielectric materials interposed therebetween, a ground electrode is formed on the ground layers, and one or more line layers are provided between the plurality of ground layers. A low-pass filter characterized by forming a line. 2. The low-pass filter according to claim 1, comprising a plurality of said line layers, wherein said lines formed on said plurality of line layers are connected to each other. 3. The low-pass filter according to claim 1, wherein the line has a spiral shape. 4. The low-pass filter according to claim 3, wherein the lines formed spirally in the line layers provided adjacent to each other have the same central axis and the same winding direction. 5. The low-pass filter according to claim 1, wherein the line self-resonates and has a pole periodically generated by the self-resonance. 6. An electronic device using the low-pass filter according to claim 1.