JP2001044779A - Attenuator and high frequency device using it - Google Patents

Abstract

(57) [Problem] To reduce a radiation voltage generated by an attenuator in a high-frequency device used for a television receiver or the like for transmitting and receiving signals related to CATV broadcasting. SOLUTION: A diode 10 is connected between one terminal and the other terminal, a first choke coil 11 is connected between one terminal and the ground, and a diode is connected between the other terminal and the ground. Second choke coil 1 connected to
2, the first choke coil 11 and the second choke coil 12 are arranged close to and parallel to the diode 10 in order to reduce a loop composed of these circuit elements and ground. Therefore, the radiation voltage can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an attenuator 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 attenuator and a high-frequency device using the same will be described below.

As shown in FIG. 4, a conventional high-frequency device includes an input terminal 101, a low-pass filter 102 to which a signal from the input terminal 101 is supplied,
02 forms a transmission system with the input / output terminal 103 connected to the output of the high-pass filter 104 to which the signal of the input / output terminal 103 is supplied, and the attenuation connected to the output of the high-pass filter 104. Vessel 105,
An amplifier 106 connected to the output of the attenuator 105;
The output terminal 107 was connected to the output of the amplifier 106.

The input / output terminal 103 has a frequency of approximately 88 MHz to 8
A 60-MHz CATV signal is supplied. The CATV signal is controlled to a predetermined level by an attenuator 105 so that a subsequent amplifier 106 is not distorted.
, And is output from the output terminal 107.

On the other hand, a transmission signal of approximately 5 MHz to 42 MHz is supplied to an input terminal 101, and is output from an input / output terminal 103 through a low-pass filter 102 through which only this signal passes. At this time, this signal is removed by the high-pass filter 104 and is not output from the output terminal 107. Further, since the CATV signal of about 88 MHz to 860 MHz is attenuated by the low-pass filter 102, it does not leak to the input terminal 101 side.

FIG. 5 is a circuit diagram of the attenuator 105. The attenuator 105 includes an input terminal 131 and the input terminal 131.
And a first diode 13 for attenuation connected to the capacitor 132.
3, a DC blocking capacitor 134 connected to the first diode 133, an output terminal 135 connected to the capacitor 134, and a first choke connected to a connection point between the capacitor 132 and the first diode 133. A coil 136, a parallel connection of a bias resistor 137 and a high-frequency grounding capacitor 138 connected between the other end of the first choke coil 136 and the ground;
32 and a second diode 139 for attenuation connected to a connection point between the first diode 133 and the first diode 133, and a resistor 1 for impedance matching connected to the second diode 139.
40 (substantially the same as the characteristic impedance, usually a small resistance of about 75 ohms), a high-frequency grounding capacitor 142 connected between the resistor 140 and the ground, and a first high-frequency grounding capacitor connected to the connection point between the resistor 140 and the capacitor 142. DC power supply 1
41, a second choke coil 143 connected to a connection point between the first diode 133 and the capacitor 134, a high-frequency grounding capacitor 145 connected between the other of the second choke coil 143 and the ground, And a second DC power supply 144 connected to a connection point between the choke coil 143 and the capacitor 145.

Next, the operation will be described. The first DC power supply 141 has a lower voltage value than the second DC power supply 144 and has a fixed voltage. Here, 3
V. On the other hand, the second DC power supply 144 is a variable power supply to which a voltage value corresponding to the signal level supplied to the input / output terminal 131 is applied.

First, the operation when the signal level supplied to the input terminal 131 is low will be described. A voltage sufficiently higher than a value obtained by adding the diode forward voltage of approximately 0.7 V to the voltage value of the first DC power supply 141 is applied to the second DC power supply 144. Here, it is set to 5V. At this time, the anode voltage of the first diode 133 is changed to the second diode 139.
The first diode 133 is turned on and the second diode 139 is turned off because the voltage is approximately 2 V higher than the anode voltage.
Therefore, the signal is hardly attenuated and the output terminal 135
Output from

Next, the operation when the signal supplied to the input terminal 131 is excessive will be described. In this case, the second DC power supply 144 is shifted to a voltage value lower than 5 V in order to reduce the signal level output from the output terminal 135 so that the subsequent amplifier 106 is not distorted. For example, it is set to 3V. At this time, the anode voltage of the first diode 133 and the anode voltage of the second diode 139 become substantially equal, and both the first diode 133 and the second diode 139 are turned on. Therefore, a part of the signal flows to the ground via the second diode 139, the resistor 140, and the capacitor 142, so that the signal level output from the output terminal 135 is reduced.

When the signal level supplied to the input terminal 131 further increases, the voltage value of the second DC power supply 144 is further reduced. For example, it is approximately 2.3V. The first diode 133 is completely turned off and the second diode 139
Is completely turned on, so that the attenuation is maximized. Therefore,
The output level from the output terminal 135 is minimized.

[0011] As shown in FIG. 4, the attenuator 105 is set before the amplifier 106. In order to realize a high-frequency device with good sensitivity, the insertion loss of the attenuator is usually 1 dB.
The following low losses must be achieved: Therefore, the input terminal 131 to which the signal shown in FIG. 5 is supplied, the capacitor 132, the first diode 133, the capacitor 134,
The output terminal 135 is connected so as to have the shortest distance as far as the component arrangement allows.

On the other hand, the first choke coil 136 and the second choke coil 143 which require a mounting space in addition to being used for the purpose of blocking a signal are not particularly limited in mounting location, so that the And is mounted where the mounting space is available. In particular, when the input signal frequency is low, it is necessary to increase the inductance value in order to increase the impedance. Therefore, the pattern is actively routed, and this pattern is also used as an inductance.

FIG. 6 is a layout diagram of a conventional high-frequency device. 6, the same parts as those in FIGS. 4 and 5 are denoted by the same reference numerals. The first diode 133 and the second diode 139 are mounted on the same package.

As shown in FIG. 6, the first diode 133 is connected to the high-pass filter 10 in order to shorten the signal line.
4 is connected to the input of the amplifier 106 in a substantially straight line. On the other hand, the first choke coil 136
The second choke coil 143 is mounted at a position separated from the high-pass filter 104 and the amplifier 106 due to the mounting space. As a result, a sufficient space between components can be ensured.

[0015]

However, in such a conventional configuration, the loop L1 formed by the signal line of the attenuator 105 and the ground pattern becomes long. Therefore, the area A of the loop L1 is also increased, and as a result, there is a problem that a radiation voltage due to a high frequency signal component flowing through the loop L1 increases.

The reason will be described in detail below.

In general, the radiation voltage E generated by the current flowing through the loop circuit is as shown in (Equation 1).

[0018]

(Equation 1)

From this equation, it can be seen that the radiation voltage E increases in proportion to the area A.

The first choke coil 136 and the second choke coil 143 are mounted in the circuit for the purpose of blocking a signal, but cannot block all the signal components. Therefore, some signal components flow to the ground via the first choke coil 136 and the second choke coil 143. There are also components jumping into the first choke coil 136 and the second choke coil 143, which similarly form a loop via the ground.

Therefore, in addition to the first choke coil 136 and the second choke coil 143 being routed on the pattern as described above, the diodes 133, 139
Since it is mounted at a position separated from the ground, the ground pattern also becomes long. As a result, there is a problem that the area A surrounding the loop L1 becomes very large, and the radiation voltage also increases accordingly.

The present invention has been made to solve the above problems, and has as its object to provide an attenuator having a sufficiently low radiation voltage.

[0023]

To achieve this object, an attenuator according to the present invention comprises a diode connected between one terminal and the other terminal, and a diode connected between one terminal and ground. A first choke coil, and a second choke coil connected between the other terminal and the ground, in order to reduce a loop formed by these circuit elements and the ground, And the second choke coil are arranged close to and substantially parallel to the diode. With this configuration, the area for forming the loop can be reduced.
The radiation voltage can be reduced.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a diode connected between one terminal and the other terminal, and a first diode connected between one terminal and the ground. A choke coil, a second choke coil connected between the other terminal and the ground, in order to reduce a loop composed of these circuit elements and ground, the first choke coil and An attenuator in which the second choke coil and the diode are arranged close to and in parallel with the diode, and the area surrounded by the loop is reduced, so that the radiation voltage generated by the current flowing through the loop can be reduced.

According to a second aspect of the present invention, an input / output terminal to which a high-frequency signal is input, a high-pass filter connected to the input / output terminal, and an output of the high-pass filter are connected. An attenuator described, an amplifier connected to the output of the attenuator, and a high-frequency device having an output terminal connected to the output of the amplifier, and the area surrounded by the loop is reduced. A high-frequency device that generates less radiation voltage can be realized.

According to a third aspect of the present invention, there is provided the high-frequency device according to the second aspect, wherein the first choke coil is arranged close to the high-pass filter in the preceding stage. Since the ground is close, the ground area is reduced, and the radiation voltage generated by the current flowing through the loop can be reduced.

According to a fourth aspect of the present invention, a low-pass filter is provided between an input / output terminal and an input / output terminal, and the low-pass filter is housed in a substantially rectangular metal housing, and the input / output terminal is connected to the output terminal. 3. The high-frequency device according to claim 2, wherein the terminal is provided on an opposite side surface, and the input / output terminal is provided on a side surface adjacent to the opposite side surface, and the input / output terminal, the output terminal, and the output terminal can be separated. In addition, air propagation between the input and output terminals can be reduced.

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

FIG. 1 is a circuit diagram of a high-frequency device according to one embodiment of the present invention. The high-frequency device according to the present invention includes an input terminal 1, a low-pass filter 2 to which a signal of the input terminal 1 is supplied, an input / output terminal 3 connected to an output of the low-pass filter 2, and a signal of the input / output terminal 3. , An attenuator 5 connected to the output of the high-pass filter 4, an amplifier 6 connected to the output of the attenuator 5, and an output terminal 7 connected to the output of the amplifier 6. Is formed from. Reference numeral 2 denotes a low-pass filter that passes frequencies of 42 MHz or less. The input / output terminal 3 and the output terminal 7 are provided on opposite metal side surfaces, and the input terminal 1 is provided on a side surface adjacent to the input / output terminal 3. By arranging in this way, air propagation between the terminals can be reduced.

The high-pass filter 4 includes a capacitor 20 connected to its input, a capacitor 23 connected to the output of the capacitor 20, a capacitor 26 connected to the output of the capacitor 23,
6, a signal output connected to the output of the capacitor 6, a series connection of the inductor 21 and the capacitor 22 connected between the connection point of the capacitor 20 and the capacitor 23 and the ground, and a connection between the connection point of the capacitor 23 and the capacitor 26 and the ground. And a series connection of the inductor 24 and the capacitor 25, and is designed to pass a frequency of about 88 MHz or more.

The attenuator 5 is connected to a common cathode (a common cathode of the diodes 51 and 52) of the attenuating diode 10 integrated so that its input is close to the capacitor 26 on the output side of the high-pass filter 4. ,
The choke coil 11 is connected so as to be close to the connection point between the capacitor 26 and the diode 10, and a parallel connection of a resistor 27 and a capacitor 28 is connected between the other terminal of the choke coil 11 and the ground. A series connection of a resistor 29 and a capacitor 30 is connected between the anode of a ground-side diode 52 of the attenuating diode 10 and the ground, and a first DC power supply 53 is connected to a connection point between the resistor 29 and the capacitor 30. I have. The choke coil 12 is connected so as to be close to the anode of the diode 51 on the signal line side of the attenuating diode 10, and the capacitor 31 is connected between the other terminal of the choke coil 12 and the ground. Further, a second DC power supply 54 connected to a connection point between the choke coil 12 and the capacitor 31 is provided.

The amplifier 6 is connected such that the capacitor 32 is close to the connection point between the diode 51 on the output side of the attenuator 5 and the choke coil 12, and the base of the transistor 33 is connected close to the output of the capacitor 32. And
A parallel connection of a capacitor 34 and a resistor 35 is connected between the emitter of the transistor 33 and the ground. A parallel connection of a resistor 37 and a capacitor 38 is connected to the collector of the transistor 33, and a resistor 36 is connected in series between the other of the parallel connection of the resistor 37 and the capacitor 38 and the base of the transistor 33. . And
A choke coil 39 is connected to the collector of the transistor 33, and a capacitor 41 is connected between the other terminal of the choke coil 39 and the ground. A DC power supply 8 is connected to a connection point between the choke coil 39 and the capacitor 41, and is connected from the collector of the transistor 33 to the output terminal 7 via the capacitor 40.

FIG. 2 is a layout diagram of a high-frequency device according to one embodiment of the present invention. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals. In FIG. 2, an inductor 21 and an inductor 2 constituting a high-pass filter 4 are shown.
4. The diode 10 forming the attenuator 5 and the transistor 33 forming the amplifier 6 are arranged close to each other.
By arranging these components on a substantially straight line, the components can proceed in the order of the circuit block, such as the inductor 21, the inductor 24, the diode 10, and the transistor 33, and a signal can be transmitted with less loss.

On the other hand, one end of the diode 10 and the first choke coil 11 are arranged at substantially the same position, and the pattern layout is almost eliminated. Further, the first choke coil 11 moves to the high-pass filter 4 side by one first choke coil as compared with the conventional example, and is arranged so as to be in close contact with the high-pass filter 4 at the preceding stage, so that the ground is shared. Thus, the area is reduced. In addition, the second choke coil 12 is also arranged close to and parallel to the first choke coil 11 within a range in which mounting is allowed, to reduce the ground area. Further, the ground of the high-pass filter 4, the ground terminal of the first choke coil 11, and the ground terminal of the second choke coil 12 are arranged so that they can be connected to the ground at substantially one point.
In addition, by arranging each terminal of the diode 10 and the first choke coil 11 and the second choke coil 12 in parallel, as shown by a dotted line in FIG.
0, the loop L2 formed by the first choke coil 11, the second choke coil 12, the wiring pattern and the ground pattern is reduced.

In order to shorten the wiring pattern, the diode 10 has a three-pole terminal in which one terminal and the other terminal and two terminals between the one terminal and the ground are included in one package. .

In this example, two diodes are used, but the same applies to one diode and three diodes.

FIG. 3 shows a pass characteristic 15 of the high-frequency device according to the embodiment of the present invention and a pass characteristic 16 of the conventional example.
Is shown. As can be seen from FIG. 3, the radiation voltage was reduced, and an improvement of the attenuation by 10 dB or more was obtained.

[0038]

As described above, according to the present invention, a diode connected between one terminal and the other terminal, a first choke coil connected between one terminal and the ground, A second choke coil connected between the other terminal and the ground, in order to reduce a loop formed by these circuit elements and the ground, the first choke coil and the second Since the choke coil and the choke coil were arranged near and parallel to the diode,
Radiation voltage can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a high-frequency device according to an embodiment of the present invention.

FIG. 2 is a layout diagram of a high-frequency device according to an embodiment of the present invention.

FIG. 3 is a diagram showing the pass characteristics of a high-frequency device according to an embodiment of the present invention and the pass characteristics of a high-frequency device according to a conventional example.

FIG. 4 is a block diagram of a conventional high-frequency device.

FIG. 5 is a circuit diagram of an attenuator of a conventional high-frequency device.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Diode 11 1st choke coil 12 2nd choke coil

Continued on the front page (72) Inventor Koji Kashima 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. 5J026 AA02 AA12 BA07 5J092 AA01 CA00 FA16 FA20 HA02 HA19 HA25 HA29 HA33 KA23 KA42 KA46 MA21 QA04 SA08 TA01 TA03 VL10 5K062 AA10 AB08 AD07 BB02 BB06 BB07 BB09 BB10 BB17 BC02 BC04 BF07

Claims (4)

[Claims] 1. A diode connected between one terminal and the other terminal, a first choke coil connected between one terminal and the ground, and a diode connected between the other terminal and the ground. With a second choke coil connected,
An attenuator in which the first choke coil and the second choke coil are arranged near and parallel to the diode in order to reduce a loop formed by these circuit elements and ground. 2. An input / output terminal to which a high-frequency signal is input,
A high-pass filter connected to the input / output terminal; an attenuator according to claim 1 connected to an output of the high-pass filter; an amplifier connected to an output of the attenuator; and an amplifier connected to an output of the amplifier. A high-frequency device having an output terminal. 3. The high-frequency device according to claim 2, wherein the first choke coil is arranged close to the high-pass filter in the preceding stage. 4. A low-pass filter is provided between an input terminal and an input / output terminal, is housed in a substantially rectangular metal housing, and the input / output terminal and the output terminal are provided on opposite sides of the housing. 3. The high-frequency device according to claim 2, wherein the input terminal is provided on a side surface adjacent to the opposite side surface.