JP2001094376A - Filter and high frequency device using this - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently secure the attenuation of a filter in a high frequency device to be used at a television receiver, etc., for transmitting and receiving a signal related to CATV broadcasting. SOLUTION: This high frequency device is provided with an input terminal 1, a filter connected to this input terminal 1 and composed of serially connected plural filter elements, and an output terminal 13 connected to the output of this filter. Among respective filter elements to be connected with the ground of the filter, the grounds of ground terminals 21 and 23 connected as odd- numbered terminals are arranged approximately, otherwise the grounds of ground terminals 22 and 24 connected as even-numbered terminals are arranged approximately. Thus, the attenuation of the filter is sufficiently secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a filter used in a television receiver for transmitting and receiving signals related to CATV broadcasting, and a high-frequency device using the same.

[0002]

2. Description of the Related Art A conventional filter and a high-frequency device using the same will be described below.

As shown in FIG. 6, a conventional filter and a high-frequency device using the same include an input terminal 152, a low-pass filter 151 to which a signal from the input terminal 152 is supplied, and
An input / output terminal 150 connected to the output of the low-pass filter 151, a high-pass filter 153 supplied with a signal input to the input / output terminal 150, an attenuator 154 connected to the output of the high-pass filter 153; The amplifier 155 was connected to the output of the attenuator 154, and the output terminal 156 was connected to the output of the amplifier 155.

The input / output terminal 150 has a frequency of approximately 88 MHz to 8
60 MHz CATV signal etc. (sometimes a TV signal)
Is supplied. This CATV signal passes through a high-pass filter 153, and is attenuated by an attenuator 154.
Is controlled to a predetermined level so as not to be distorted, and is output from an output terminal 156 via an amplifier 155 at the subsequent stage.

On the other hand, the above-mentioned transmission signal is supplied to an input terminal 152 and is output from an input / output terminal 150 via a low-pass filter 151.

Here, the high-pass filter 153 is
While passing TV signals, approximately 5MHz to 42MHz
Are inserted to eliminate the transmission signal. Thus, the transmission signal is not output from the output terminal 156 via the high-pass filter 153.

[0007] The low-pass filter 151 has a characteristic of passing the transmission signal and attenuating the CATV signal. This is because the CATV signal is input to the high-pass filter 153 without being split into the low-pass filter 151.

FIG. 7 is a circuit diagram of the low-pass filter 151. The low-pass filter 151 is connected to the input terminal 101
And an inductor 102 connected to the input terminal 101
A capacitor 103 connected between the output of the inductor 102 and the ground; a capacitor 103 connected in series with the inductor 102;
Are connected in parallel with each other, a capacitor 106 is connected between the output of the first parallel connection and the ground, and is connected in series with the output of the first parallel connection. And a second parallel-connected body in which an inductor 107 and a capacitor 108 are connected in parallel, and a capacitor 10 connected between the output of this second parallel-connected body and ground.
9, a third parallel connection in which the inductor 110 and the capacitor 111 are connected in parallel with the output of the second parallel connection, and the output of this third parallel connection and the ground. Capacitor 112 connected between
And an output terminal 113 connected in series to the output of the third parallel connection body.

[0009]

However, in such a conventional configuration, there is a problem that the pass characteristic of the filter is deteriorated by the ground pattern. This is considered to be because unnecessary signal components return from the output side to the input side via the ground pattern, thereby deteriorating the attenuation characteristics of the filter.

The reason will be described in detail below. FIG. 8 is an equivalent circuit of FIG. 7 taking the ground pattern into consideration. 8, the same components as those in FIG. 7 are denoted by the same reference numerals. 8, reference numeral 114 denotes a capacitor 103
A ground pattern existing between the capacitor 103 and the capacitor 106; a ground pattern 116 existing between the capacitor 106 and the ground;
Ground pattern between capacitor and capacitor 109, 1
18, a ground pattern existing between the capacitor 109 and the ground; 119, a capacitor 109 and the capacitor 1
Reference numeral 120 denotes a ground pattern existing between the capacitor 112 and the ground.

Reference numeral 121 denotes a connection point between the capacitor 103, the ground pattern 114, and the ground pattern 115;
Reference numeral 122 denotes a connection point between the capacitor 106, the ground pattern 115, the ground pattern 116, and the ground pattern 117, and reference numeral 123 denotes a capacitor 109 and the ground pattern 1
17, ground pattern 118 and ground pattern 11
Reference numeral 9 denotes a connection point, and reference numeral 124 denotes a connection point between the ground pattern 119, the ground pattern 120, and the capacitor 112.

Here, the aforementioned connection point 122 and connection point 1
23. A signal component generated at the connection point 121 when an unnecessary signal is superimposed on the connection point 124 will be obtained by using a simple circuit.

The connection point 121 is the ground closest to the input terminal 101. By examining the potential of the unnecessary signal at the connection point 121, the feedback amount of the unnecessary signal is estimated.

For simplicity of calculation, it is assumed that all feedback signals flow through ground.

FIG. 9 shows a circuit obtained by extracting the ground pattern in FIG. 9, the same components as those in FIG. 8 are denoted by the same reference numerals. In order to simplify the calculation, the ground pattern 114 is a resistor 114, the ground pattern 115 is a resistor 115, the ground pattern 116 is a resistor 116, the ground pattern 117 is a resistor 117, the ground pattern 118 is a resistor 118, and the ground pattern 1
19 is a resistor 119, and the ground pattern 120 is a resistor 12
Replaced with 0.

In order to further simplify the calculation, an R-2R circuit is used. That is, the resistance value of the resistor 114 is R [Ω],
The resistance of the resistor 115 is R [Ω], the resistance of the resistor 116 is 2 R [Ω], the resistance of the resistor 117 is R [Ω], and the resistance of the resistor 11 is 11 [Ω].
8 is 2R [Ω], and the resistance of the resistor 119 is R
[Ω] and the resistance value of the resistor 120 is 2R [Ω].

The circuit will be briefly described. A resistance value looking left from the connection point 122 is obtained. The series resistance value of the resistor 114 and the resistor 115 is 2R [Ω]. The parallel resistance value of this 2R [Ω] and the resistance value 2R [Ω] of the resistor 116 becomes R [Ω]. After all, the resistance value seen from the connection point 122 to the left is R
[Ω]. The current flowing through the resistors R114 and R115 and the current flowing through the resistor R116 have the same value.

Next, the resistance value as viewed from the connection point 123 to the left will be determined. From the above result, the resistance value viewed from the connection point 122 to the left is R [Ω], so that the resistance value viewed from the connection point 123 to the left is R [Ω], similarly to the connection point 122. The currents flowing through the resistors 117 and 118 have the same value.

Similarly, it can be easily understood that the resistance value seen from the connection point 124 to the left also becomes R [Ω]. That is, the total resistance of the circuit is R [Ω]. The current flowing through the resistor 119 is the same as the current flowing through the resistor 120. That is, the current is shunted to exactly １ ／ at the connection points 122, 123 and 124.

Here, when the voltage of the unnecessary signal applied to the connection point 124 is 2 V [V], the current is 2 V / R [A] because the total resistance is R [Ω]. Resistance 119 and resistance 1
20 are 1/2 each, so that V / R
[A]. Similarly, the current flowing through the resistor 117 and the resistor 118 is V / (2R) [A], and the resistor 114 and the resistor 115
And the current flowing through the resistor 116 is V / (4R) [A].

Next, the voltage at the connection point 121 when a voltage of 2V "V" is applied as an unnecessary signal to the connection points 122, 123 and 124 will be obtained. It is calculated using the superposition theorem. That is, the current value when 2 V [V] is applied independently to the connection points 122, 123, and 124 is obtained, and the sum is calculated.

Calculation is performed sequentially from the connection point 124. When 2V [V] is applied to the connection point 124, as described above, the current flowing through the resistor 114 is V / (4R) [A]. Therefore, the voltage generated at the connection point 121 is V / 4
[V].

Next, calculation is performed for a case where 2V [V] is applied to the connection point 123. By the same calculation as in the case of the connection point 124, the current is V / (2R) [A]. Therefore, the voltage generated at the connection point 121 becomes V / 2 [V].

Similarly, calculation is performed for a case where 2V [V] is applied to the connection point 122. The current is V / (R) [A]
It is. Therefore, the voltage generated at the connection point 121 is V
[V].

The voltage V [V] generated when 2V [V] is applied to the connection point 122 and the connection point 123
Is generated by applying 2V [V] to the
When the sum of 2 [V] and the voltage V / 4 [V] generated by application of 2 V [V] to the connection point 124 is obtained, the voltage generated at the connection point 121 is 7/4 V [V]. Become.

As described above, the voltage of the unnecessary signal is 2 V [V], the points where the unnecessary signal is superimposed are the connection points 122, 123 and 124, and the voltage of the unnecessary signal that returns to the connection point 121 on the input side is: It becomes 7 / 4V [V].

Although the pattern is replaced with a resistor to simplify the circuit calculation, it is considered that the unnecessary signal is fed back through the ground pattern, and thus the attenuation characteristic of the filter is degraded.

The present invention solves this problem.
It is an object of the present invention to provide a filter having a sufficient attenuation characteristic.

[0029]

In order to achieve this object, a filter according to the present invention comprises: an input terminal; a filter connected to the input terminal and having a plurality of filter elements connected in series; An output terminal connected to the output, and among the filter elements connected to the ground of the filter, the ground terminals connected to the odd-numbered ground terminals or the ground terminals connected to the even-numbered ground terminals Are arranged close to each other. With this configuration, the amount of feedback of the ground circuit formed by the ground pattern is reduced, so that the amount of attenuation of the pass characteristic of the filter can be sufficiently ensured.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention provides an input terminal, a filter connected to the input terminal and having a plurality of filter elements connected in series, and a filter connected to the output of the filter. Output terminal, and among the filter elements connected to the ground of the filter,
This is a filter in which the ground terminals connected to the odd-numbered ground terminals or the ground terminals connected to the even-numbered ground terminals are arranged close to each other. By doing so, the amount of feedback of the unnecessary signal is reduced, so that the attenuation of the pass characteristic of the filter can be sufficiently ensured.

According to a second aspect of the present invention, there is provided the filter according to the first aspect, wherein a ground pattern is disposed so as to surround the filter. The ground is formed in a loop shape, whereby the ground is stabilized. , The attenuation of the pass characteristic can be sufficiently secured. In addition, since the ground of the component can be arranged at any point in the loop, the ground pattern impedance can be reduced.

According to a third aspect of the present invention, the filter element is connected between a parallel connection of an inductor and a first capacitor inserted into a signal line, and between an input of this parallel connection and ground. A second capacitor, and a third capacitor connected between the output of the parallel circuit and the ground. / 2
2. The filter according to claim 1, wherein the filter is set to have a capacitance value of か ら to.
Since the impedance is increased, it is possible to reduce a signal component that passes through the filter from the ground and returns to the input.

According to a fourth aspect of the present invention, the filter element includes a series connection of a first capacitor and a second capacitor inserted into a signal line, the first capacitor and the second capacitor. A third capacitor connected between the connection point of the capacitor and the ground is formed by a series connection of the inductor and the inductor constituting the filter element on the output terminal side. 2. The filter according to claim 1, wherein the inductance value is set to twice to four times, and by increasing the value of the inductor, the impedance increases, so that the signal component passing from the ground through the filter to the input can be reduced. .

According to a fifth aspect of the present invention, there is provided an input terminal, a low-pass filter to which a signal of the input terminal is supplied, an input / output terminal connected to an output of the low-pass filter, and an input / output terminal. A high-pass filter to which a signal input to the high-pass filter is supplied, an attenuator connected to an output of the high-pass filter, an amplifier connected to an output of the attenuator, and an output terminal connected to an output of the amplifier. The high-frequency device using the filter according to any one of claims 1 to 3, wherein the low-pass filter is configured to output a harmonic signal of a signal input from an input terminal. Since the filter can be reduced in size, a high-frequency device resistant to interference can be provided.

According to a sixth aspect of the present invention, there is provided an input terminal, a low-pass filter to which a signal of the input terminal is supplied, an input / output terminal connected to an output of the low-pass filter, and an input / output terminal. A high-pass filter to which a signal input to the high-pass filter is supplied, an attenuator connected to an output of the high-pass filter, an amplifier connected to an output of the attenuator, and an output terminal connected to an output of the amplifier. The high-pass filter is a high-frequency device as the filter according to any one of claims 1, 2 and 4, wherein a signal supplied from an input terminal and a signal supplied from an input / output terminal are mixed. As a result, the interference signal generated can be reduced, so that a high-frequency device not affected by the interference can be realized.

According to a seventh aspect of the present invention, there is provided an input terminal, a low-pass filter to which a signal of the input terminal is supplied, an input / output terminal connected to an output of the low-pass filter, and an input / output terminal. A high-pass filter to which a signal input to the high-pass filter is supplied, an attenuator connected to an output of the high-pass filter, an amplifier connected to an output of the attenuator, and an output terminal connected to an output of the amplifier. Wherein the low-pass filter is a filter according to any one of claims 1 to 3, and the high-pass filter is a high-frequency device using the filter according to any one of claims 1, 2, and 4. Since the filter according to any one of claims 1, 2 and 4 is used for a high-pass filter, a signal supplied from an input terminal does not flow to the high-pass filter and is an input / output terminal. Is supplied, a small transmitting high-frequency device can be realized loss. Further, since the filter according to any one of claims 1 to 3 is used for a low-pass filter, the signal supplied from the input / output terminal does not flow to the low-pass filter, passes through the high-pass filter, and is output to the output terminal. An output and high-frequency receiving high-frequency device with high sensitivity can be realized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is an equivalent circuit diagram including a ground pattern of a filter according to Embodiment 1 of the present invention. The filter of the present invention is a low-pass filter that attenuates signals of approximately 42 MHz or higher. The filter of the present invention is connected in series to an input terminal 1, an inductor 2 connected to the input terminal 1, a capacitor 3 connected between the output of the inductor 2 and the ground, and an output of the inductor 2. Inductor 4 and capacitor 5
Are connected in parallel with each other, the capacitor 6 is connected between the output of the first parallel connection 31 and the ground, and the output of the first parallel connection 31 is connected in series. A second parallel connection body 32 connected to the inductor 7 and the capacitor 8 in parallel, a capacitor 9 connected between the output of the second parallel connection body 32 and the ground, A third parallel connection body 33 connected in series with the output of the parallel connection body 32 and having the inductor 10 and the capacitor 11 connected in parallel; and a third parallel connection body 33 connected between the output of the third parallel connection body 33 and the ground. And the output terminal 13 connected to the output of the third parallel connection body 33.

Here, the capacitor 3, the capacitor 6, and the parallel connection body 31 constitute one filter element. Similarly, one filter element is formed by the capacitor 6 and the capacitor 9 and the parallel connection body 32, and one filter element is formed by the capacitor 9 and the capacitor 12 and the parallel connection body 33.

Then, the ground of the capacitor 3 which becomes the first ground counted from the input terminal 1 and the ground of the capacitor 9 which becomes the third ground counted from the input terminal 1 are arranged close to each other, and counted from the input terminal 1. Thus, the ground of the capacitor 6 serving as the second ground and the ground of the capacitor 12 serving as the fourth ground counted from the input terminal 1 are arranged close to each other. Further, the ground pattern is formed in a loop shape so as to surround the entire filter so that the ground is stabilized.

In FIG. 1, reference numeral 14 denotes a ground pattern existing between the capacitor 3 and the ground; 15 denotes a ground pattern existing between the capacitor 3 and the capacitor 9;
Is a ground pattern existing between the capacitor 9 and the ground, 17 is a ground pattern existing between the capacitor 6 and the ground, 18 is a ground pattern existing between the capacitor 6 and the capacitor 12, and 19 is a ground existing between the capacitor 12 and the ground. It is a pattern.

Reference numeral 21 denotes a connection point between the capacitor 3, the ground pattern 14, and the ground pattern 15, and reference numeral 23 denotes a capacitor 9, the ground pattern 15, and the ground pattern 1.
6 is the connection point, 22 is the capacitor 6 and the ground pattern 1
Reference numeral 24 denotes a connection point between the capacitor 7 and the ground pattern 18, and reference numeral 24 denotes a connection point between the capacitor 12 and the ground pattern 18.

For comparison with the conventional example, the connection point 2
2. A signal component generated at the connection point 21 when an unnecessary signal is superimposed on the connection points 23 and 24 will be obtained by using a simple circuit.

The connection point 21 is the ground closest to the input terminal 1. By checking the potential of the unnecessary signal at the connection point 21, the feedback amount of the unnecessary signal is estimated. In the conventional example, in order to simplify the calculation, it is assumed that all the feedback signals flow through the ground. Similarly, since the connection points 22 and 24 and the connection point 21 are not connected,
It can be intuitively understood that feedback of unnecessary signals is reduced.

FIG. 2 shows a circuit obtained by extracting the ground pattern in FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals. Ground pattern 14
, The resistor 14, the ground pattern 15 as the resistor 15, and the ground pattern 16 as the resistor 16.

According to the conventional example, the resistance of the resistor 14 is set to R
[Ω], the resistance of the resistor 15 is R [Ω], the resistance of the resistor 16 is 2R [Ω], and the voltage applied to the connection point 23 is 2 [Ω].
V [V]. The voltage generated at the connection point 21 is the resistance 1
The voltage is divided by 4 and the resistor 15 to become V [V].

In the conventional example, since it was 7/4 V [V], it can be seen that feedback is reduced. When the power ratio between the voltage of the conventional example and the voltage of the present embodiment is calculated, the power of the present embodiment is reduced by about 5 [dB].

FIG. 5 shows a pass characteristic 50 of the filter according to the first embodiment of the present invention and a pass characteristic 51 of the conventional example. As can be seen from FIG. 5, it can be seen that the attenuation is particularly improved in the 500 [MHz] to 800 [MHz] band.

In this embodiment, the capacitance of the capacitor 12 connected closest to the output terminal 13 is preferably set to a capacitance value that is 1/2 to 1/4 that of the other ground terminals. In the present embodiment, the capacity of the capacitor 3 (about 68
[PF]), the capacitance of the capacitor 6 (approximately 56 [pF]),
The capacitance of the capacitor 9 is set to approximately 56 [pF], and the capacitance of the capacitor 12 is set to approximately 1/3 of 18 [pF]. The attenuation characteristic is improved by increasing the impedance.

(Embodiment 2) FIG. 3 is an equivalent circuit diagram including a ground pattern of a filter according to Embodiment 2 of the present invention. The filter of the present invention is a high-pass filter that attenuates signals of approximately 42 MHz or less. The filter of the present invention includes an input terminal 40, a capacitor 41 connected to the input terminal 40, a series connection body 60 of a capacitor 42 and an inductor 43 connected in series between the output of the capacitor 41 and the ground. A capacitor 44 connected to a connection point between the connection body 60 and the capacitor 41
And a series connection body 6 of a capacitor 45 and an inductor 46 connected in series between the output of the capacitor 44 and the ground.
1; a capacitor 47 connected to a connection point between the series connection body 61 and the capacitor 44;
A series connection 62 of a capacitor 48 and an inductor 49 connected in series between the output of
It comprises a capacitor 50 connected to a connection point between the capacitor 2 and the capacitor 47, and an output terminal 51 connected to the output of the capacitor 50.

Here, the capacitors 41 and 44
And the series connection body 60 form a first filter element. Hereinafter, similarly, the second filter element is formed by the series connection body 61 with the capacitor 44 and the capacitor 47, and the third filter element is formed by the series connection body 62 with the capacitor 47 and the capacitor 50.

The ground of the inductor 43, which is the first ground counted from the input terminal 40, and the input terminal 4
The ground of the inductor 49, which is the third ground counted from 0, is arranged close to. In addition, the ground pattern including the ground of the inductor 46, which is the second ground counted from the first ground, the third ground, and the input terminal 40, is loop-shaped so as to surround the entire filter so that the ground is stabilized. I have to.

In FIG. 3, reference numeral 52 denotes a ground pattern existing between the inductor 43 and the ground; 53, a ground pattern existing between the inductor 43 and the inductor 49; 54, a ground pattern existing between the inductor 49 and the ground; A ground pattern existing between 46 and the ground, 56 is a connection point between the inductor 43 and the ground pattern 52 and the ground pattern 53,
7 is a connection point between the inductor 46 and the ground pattern 55;
Reference numeral 58 denotes a connection point between the inductor 49, the ground pattern 53, and the ground pattern 54.

In the second embodiment, the inductance of the inductor 49 connected closest to the output terminal 51 is approximately twice that of the other inductors. In the present embodiment, the inductance of the inductor 43 is set to approximately 180
[NH], the inductance of the inductor 46 is approximately 200
[NH], the inductance of the inductor 49 is approximately 360
[NH], and the inductance of the inductor 49 is
The attenuation characteristic is improved by increasing the impedance to 360 [nH] which is approximately twice as large.

The effect remains unchanged even if the positions of the capacitors and inductors of the series-connected bodies 60, 61, 62 are reversed.

(Embodiment 3) FIG. 4 is a block diagram of a high-frequency device according to Embodiment 3. As shown in FIG. 4, the high-frequency device according to the third embodiment includes an input terminal 72.
A low-pass filter 71 to which the signal of the input terminal 72 is supplied, an input / output terminal 70 connected to the output of the low-pass filter 71, and a high-pass filter 73 to which the signal input to the input / output terminal 70 is supplied. , An attenuator 74 connected to the output of the high-pass filter 73, an amplifier 75 connected to the output of the attenuator 74, and an output terminal 76 connected to the output of the amplifier 75.

As described above, from the input terminal 72, approximately 5
A signal from MHz to 42 MHz is supplied. This signal is
Very high levels (approximately 60 dBmV) are provided because they are transmitted to the system side 00 km away. For this reason,
An amplifier that outputs a signal of approximately 60 dBmV is distorted, and at the same time, a high-level harmonic signal is also input.

For example, when a signal of 29 MHz is supplied from the input terminal 72, approximately 8 MHz supplied from the input / output terminal 70 is supplied.
The third harmonic of 87 MHz, which is substantially the same as the 8 MHz signal, is also input. That is, an interference signal is generated approximately 1 MHz away from the desired signal. However, the low-pass filter 7
1 uses the low-pass filter of the first embodiment, the third harmonic of approximately 87 MHz can be made sufficiently small by the low-pass filter 71 and does not cause interference. This jamming signal includes not only the above-mentioned combination but also a plurality of combinations, all of which are in the low-pass filter 7.
1 can be sufficiently reduced. Therefore, a high-frequency device resistant to interference can be realized.

On the other hand, approximately 42 supplied from the input terminal 72
MHz signal and approximately 8 signals supplied from the input / output terminal 70
By mixing 8 MHz, approximately 4
6 MHz, and a component of about 92 MHz as its second harmonic. However, since the high-pass filter 73 according to the second embodiment is used, the interference signal of approximately 46 MHz is attenuated by the high-pass filter 73, and thus these harmonic signals are sufficiently small. Although a plurality of combinations of the interference signal are generated by the signal supplied from the input terminal 72 and the signal supplied from the input / output terminal 70, the high-pass filter 73 can sufficiently reduce the combination, so that a high-frequency device having good interference characteristics is provided. I can do it.

Further, the signal supplied from the input terminal 72 does not flow into the high-pass filter 73 because the attenuation of the high-pass filter 73 is large and the impedance is high for signals of approximately 5 MHz to 42 MHz. . Therefore, this signal can be output from the input / output terminal 70 with little loss. As a result, signals can be efficiently transmitted to a system that is several hundred kilometers away.

Since the attenuation of the low-pass filter 71 is large, the signal supplied from the input / output terminal 70 does not flow through the low-pass filter 71. Therefore, it is possible to output from the output terminal 76 with little loss. Since the high-pass filter 73 is connected to the input / output terminal 70 of the high-frequency device, it has the greatest effect on the reception sensitivity. However, since the loss of the high-pass filter 73 is small, a high-sensitivity high-frequency device can be realized.

[0062]

As described above, according to the present invention, among the filter elements connected to the ground of the filter, the ground terminals connected to the odd number or the ground terminals connected to the even number are used. Since the grounds are arranged close to each other, the attenuation characteristics of the filter can be sufficiently ensured.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a filter according to a first embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of a part of the filter.

FIG. 3 is a circuit diagram of a filter according to a second embodiment of the present invention.

FIG. 4 is a block diagram of a high-frequency device according to Embodiment 3 of the present invention.

FIG. 5 is a diagram illustrating pass characteristics of a filter according to the first embodiment of the present invention and pass characteristics in a conventional example

FIG. 6 is a block diagram of a conventional high-frequency device.

FIG. 7 is a circuit diagram of a filter used in a conventional high-frequency device.

FIG. 8 is an equivalent circuit diagram of the same filter.

FIG. 9 is an equivalent circuit diagram of the ground of the filter.

[Explanation of symbols]

 1 Input Terminal 2 Inductor 3 Capacitor 4 Inductor 5 Capacitor 6 Capacitor 7 Inductor 8 Capacitor 9 Capacitor 10 Inductor 11 Capacitor 12 Capacitor 13 Output Terminal 14 Ground Pattern 15 Ground Pattern 16 Ground Pattern 17 Ground Pattern 18 Ground Pattern 19 Ground Pattern 21 Connection Point 22 Connection point 23 Connection point 24 Connection point

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Yasuaki Okura 1006 Kadoma, Kazuma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Term (reference) 5J024 AA01 BA18 BA19 CA10 CA14 DA01 DA25 EA01 EA02 FA01 5K062 AA10 AB01 AD07 AE04 BB01 BB03 BB09 BC02 BC04 BF07

Claims (7)

[Claims] An input terminal, a filter connected to the input terminal and having a plurality of filter elements connected in series, and an output terminal connected to an output of the filter, connected to a ground of the filter A filter in which grounds connected to odd-numbered ground terminals or grounds connected to even-numbered ground terminals are arranged close to each other among the filter elements. 2. The filter according to claim 1, wherein a ground pattern is arranged so as to surround the filter. 3. A filter element comprising: a parallel connection of an inductor and a first capacitor inserted into a signal line; a second capacitor connected between an input of the parallel connection and a ground; And a third capacitor connected between the output terminal and the ground, and the capacitor connected between the output terminal and the ground has a capacitance value that is approximately 1/2 to 1/4 that of the other capacitors. The filter according to claim 1, which is set. 4. A filter element is provided between a series connection of a first capacitor and a second capacitor inserted into a signal line, and a connection point between the first capacitor and the second capacitor and a ground. The value of the inductor, which is formed by the series connection of the third capacitor and the inductor connected to each other and forms the filter element on the output terminal side, is set to approximately twice to four times the inductance value of the other inductors. The filter according to claim 1. 5. An input terminal, a low-pass filter to which a signal of the input terminal is supplied, an input / output terminal connected to an output of the low-pass filter, and a high-pass to which a signal input to the input / output terminal is supplied. A low-pass filter comprising: a filter; an attenuator connected to an output of the high-pass filter; an amplifier connected to an output of the attenuator; and an output terminal connected to an output of the amplifier. A high-frequency device using the filter according to any one of items 1 to 3. 6. An input terminal, a low-pass filter to which a signal of the input terminal is supplied, an input / output terminal connected to an output of the low-pass filter, and a high-pass to which a signal input to the input / output terminal is supplied. A high-pass filter comprising: a filter; an attenuator connected to an output of the high-pass filter; an amplifier connected to an output of the attenuator; and an output terminal connected to an output of the amplifier. A high-frequency device using the filter according to any one of (2) and (4). 7. An input terminal, a low-pass filter to which a signal of the input terminal is supplied, an input / output terminal connected to an output of the low-pass filter, and a high-pass to which a signal input to the input / output terminal is supplied. A low-pass filter comprising: a filter; an attenuator connected to an output of the high-pass filter; an amplifier connected to an output of the attenuator; and an output terminal connected to an output of the amplifier. A high-frequency device according to any one of claims 1 to 3, wherein the high-pass filter is the filter according to any one of claims 1, 2, and 4.