JPH0918368A - Variable attenuator - Google Patents

Abstract

PURPOSE: To reduce the wiring of an attenuator and an operation part for adjusting an attenuation amount constituted on separate substrates. CONSTITUTION: A main circuit board 74 and an operation part substrate 80 are provided inside a case body and this variable attenuator 70 provided on the main circuit board 74 changes the attenuation amount of high frequency signals supplied from an input terminal 76 corresponding to the current value of DC routes 108, 110 and 118 and performs output from an output terminal 78. An opening/closing switch 126 is connected through a high frequency stop coil 124 to the output terminal 86 of the operation part substrate 80 connected through a coaxial cable 88 connected to the input terminal 76. One end of the DC routes 108, 110 and 118 is connected to a DC power supply terminal 101 and the other end is DC-connected to the input terminal 76.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable attenuator capable of varying an attenuation amount, and more particularly to a variable attenuator housed in a housing together with other electronic circuits.

[0002]

2. Description of the Related Art Conventionally, as a variable attenuator provided in a housing together with other electronic circuits as described above, there is one provided in a booster used for receiving television broadcasting, for example. For example, in a booster used at home,
Since it is often mounted on a wall or the like, a first surface for wall mounting is provided on the housing. In order to improve the operability, the booster adjustment operation section and the input / output terminals are
Is provided on an operation portion substrate provided in the housing close to the second surface so that the second surface opposite to the second surface can be operated. Further, the high frequency amplifier and the variable attenuator that compose the main circuit of the booster are configured on a main circuit board different from the operation unit board and are provided in the housing for downsizing.

An example of such a booster is shown in FIG.
In this booster, as described above, the booster input terminal 4 and the output terminal 6 are provided on the operation unit substrate 2.
Of the television broadcast signals supplied to the booster input terminal 4, for example, a television broadcast signal in a band that does not require amplification, for example, a low frequency band television broadcast signal is supplied to the bandpass filter 8 having the low band as a pass band. It is supplied to the booster output terminal 6.

The television broadcast signal supplied to the input terminal 4 is supplied from the operation terminal board output terminal 10 to the main circuit board input terminal 16 of the main circuit board 14 via the coaxial cable 12. Of the television broadcast signals supplied to the input terminal 16, a band that requires amplification, for example, a high band, uses the high band as a pass band, and the main circuit board 14
Is extracted by the band pass filter 17 provided in the above, the attenuation amount is changed by the variable attenuator 22 including the PIN diodes 18 and 20, and is amplified by the high frequency amplifier 24. The output of the high frequency amplifier 24 is supplied to the input terminal 30 of the operation portion substrate via the output terminal 26 of the main circuit substrate 14 and the coaxial cable 28. Since this input terminal 30 is connected to the booster output terminal 6, the amplified high frequency television broadcast signal is combined with the low frequency television broadcast signal that has passed through the band pass filter 8 and output. It is output from the terminal 6.

The variable attenuator 22 includes a DC blocking capacitor 3
The band-pass filter 17 and the high-frequency amplifier 24 are connected via 2, 34. The attenuation amount of the variable attenuator 22 is changed by operating the changeover switch 36 provided on the operation portion substrate 2. That is, when the amount of attenuation is reduced, the changeover switch 36 is changed to the lower side in the figure.
Thereby, the power supply line 42 extending from the DC power supply terminal 38 of the main circuit board 14 to the operation circuit board 2 side, the operation circuit board 2
Changeover switch 36, operation circuit board 2 to main circuit board 1
4, the anode of the PIN diode 20 and the PIN diode 1 via the high-frequency blocking coil 46.
A DC voltage is applied to the cathode of No. 8. At this time, PI
Since the cathode of the N diode 20 is grounded via the resistor 48, a current flows to the PIN diode 20,
Conduct. On the other hand, since the voltage obtained by dividing the DC power supply voltage by the voltage divider 40 is applied to the anode of the PIN diode 18, the potential of the cathode is higher than the anode potential and does not conduct. Therefore, the attenuation by the variable attenuator 20 is very small.

When the changeover switch 36 is changed over as shown in the figure, the DC power supply voltage divided by the voltage divider 50 attached to the changeover switch 36 is connected to the anode of the PIN diode 20 via the operation line 44 and the high frequency blocking coil 46. P
It is supplied to the cathode of the IN diode 18. At this time, since the voltage dividers 40 and 50 are configured such that the anode voltage of the PIN diode 18 becomes higher than the cathode voltage, the PIN diode 18 becomes conductive and the high frequency resistance value becomes small. Since the anode of the PIN diode 18 is grounded by the capacitor 52, the television broadcast signal from the bandpass filter 17 is made to flow to the ground potential. Further, since the voltage applied to the anode of the PIN diode 20 is small, the PIN diode
The current flowing through the diode 20 decreases, the high frequency resistance value increases, and the television broadcast signal from the bandpass filter 17 is greatly attenuated.

[0007]

However, in such a booster, the power supply line 42 and the operation line 44 are required to adjust the attenuation amount of the variable attenuator 22, and the wiring work is increased. In particular, in the booster as described above, in addition to the power supply line 42 and the operation line 44, the coaxial cables 12, 28 and the like are necessary because of the configuration thereof, and reducing the wiring as much as possible reduces the efficiency of the assembly work. It is very useful from the standpoint of conversion.

An object of the present invention is to reduce the wiring between the operating section and the attenuator when the operating section and the attenuator for adjusting the attenuation amount are formed on different substrates.

[0009]

In order to solve the above problems, the first invention has a casing and first and second substrates provided in the casing. Variable damping means is provided on the first substrate. The variable attenuator has a DC path, and changes the attenuation state of the AC signal supplied from the input side according to the value of the voltage or current in the DC path and outputs the AC signal from the output side. The second substrate is provided with a terminal that is connected to the variable attenuator via an AC signal transmission line. One end of the DC path is connected to one end of the DC power supply, and the other end is DC-connected to the transmission line on the first substrate. Between the terminal and the other terminal of the power source, a DC adjusting means for adjusting the voltage or current of the DC path is connected in a DC manner.

A second aspect of the present invention is the variable attenuator of the first aspect, wherein the casing has a first surface attached to the support and a second surface facing the first surface. However, the first substrate is attached in the vicinity of the second surface, and the DC adjusting means can be operated from the second surface side.

A third aspect of the present invention is the variable attenuator of the first or second aspect, wherein the DC adjusting means is an open / close switch, and the variable attenuating means is provided between the input side and a reference potential point. An AC-connected first PIN diode and a second PIN diode AC-connected between the input side and the output side, further including first and second conductive state changes It also has means. The first conductive state changing means has a conductive path and a control electrode for changing the conductive state of the conductive path, and the conductive path is connected in series to the first PIN diode in direct current to form a first series. It constitutes the circuit. The second conductive state changing means has a conductive path and a control electrode similarly to the first conductive state changing means, and the conductive path is connected to the second PIN diode in direct current to form a second line. Constitutes a series circuit of. The control electrodes of the first and second conductive state changing means are connected to the DC path.

[0012]

According to the first to third inventions, the first inside the housing
The other end of the DC path is connected to the transmission line connecting the input side or the output side of the attenuating means on the board of 1 to the terminal on the second board. The other end of the DC path via this transmission line is connected to the other terminal of the power supply via the DC adjusting means provided on the second substrate. One end of the DC path is connected to one terminal of the power supply. Therefore,
By adjusting the DC adjusting means, the current or voltage of the DC path changes, and the attenuation amount of the attenuating means changes. First
The wiring between the substrate and the second substrate is only the transmission line, and there is no special wiring for adjusting the attenuation amount.

In particular, according to the second aspect of the invention, since the DC adjusting means can be operated from the operation wall, the second adjustment method can be performed by approaching the operation wall.
The substrate is provided. On the other hand, the first substrate is provided separately from the second substrate in order to secure the installation space. The reduction of the wiring between the substrates thus separated is significant.

Further, according to the third aspect of the invention, since the state of the DC path can be changed by opening and closing the open / close switch, the conduction states of the two conduction state changing means are changed in response to this, and as a damping means. Function.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment shown in FIG. 1, attenuating means, eg, variable attenuator 70 and high frequency amplifier 72, are constructed on a first substrate, eg, main circuit board 74. Variable attenuator 7
0 attenuates the high frequency signal supplied from the main circuit board input terminal 76 and supplies it to the high frequency amplifier 72. The high frequency amplifier 72 amplifies the input high frequency signal and supplies it to the main circuit board output terminal 78. The high frequency amplifier 7
The variable attenuator 70 is provided on the input side of 2 because the excessive input is supplied to the high frequency amplifier 72,
This is to prevent the distortion of the output of.

The high frequency signal input to the variable attenuator 70 is a second board, for example, an operation section board input terminal 82 provided on the operation section board 80, a DC blocking capacitor 84, an operation section board output terminal 86, and a coaxial cable 88. It is supplied to the main circuit board input terminal 76 via.

The variable attenuator 70 includes a PIN diode 90.
Is connected to the input terminal 76 via the DC blocking capacitor 92, and the cathode is connected to the input side of the high frequency amplifier 72 via the DC blocking capacitor 94. That is, the anode of the PIN diode 90 is connected to the input terminal 76, and the cathode thereof is connected to the input side of the high frequency amplifier 72 in a high frequency manner.

Similarly, the anode of the PIN diode 96 is connected to the connection point between the capacitor 92 and the anode of the PIN diode 90 via the DC blocking capacitor 98, and the cathode of the PIN diode 96 is connected to the reference potential point.
For example, it is connected to the ground potential point. This gives P
The IN diode 96 is also connected between the input terminal 76 and the reference potential point in high frequency.

The anode of the PIN diode 90 is connected via a resistor 100 to one electrode of a DC power source (not shown) provided on the main circuit board 74, for example, the positive terminal 101. The other electrode of this DC power supply, for example, the negative terminal, is grounded. The cathode of the PIN diode 90 is grounded via the resistors 102 and 104. Further, the conductive point changing means, for example, the emitter of the PNP transistor 106 is connected to the connection point of the resistors 102 and 104, and the collector is grounded. As a result, the conductive path of the transistor 106, that is, the emitter-collector conductive path is connected in series with the PIN diode 90 via the resistor 102 in a direct current manner. Also, the control electrode of the transistor 106, for example the base, and the resistor 10
A resistor 108 is connected between the connection point of 2 and 104, and the base is also connected to the input terminal 76 through a series circuit of the resistor 110 and the high frequency blocking coil 112. Further, the emitter of the transistor 106 is the resistor 1
It is connected to one electrode 101 of the DC power supply via 03.

The anode of the PIN diode 96 is connected to a conductive state changing means such as N via a resistor 114.
The emitter of the PN transistor 116 is connected.
The collector of the transistor 116 is connected to the positive terminal 101 of the DC power supply. This gives P
The IN diode 96 and the collector-emitter conduction path that is the conduction path of the transistor 116 are connected in series in a direct current manner. Further, a resistor 118 is connected between the collector of the transistor 116 and the control electrode, for example, the base. Further, the base is a high frequency blocking coil 11
It is connected to the input terminal 76 via 2.

Between the power supply terminal 101 and the input terminal 76,
The resistors 103, 108, 110, 118 and the high frequency blocking coil 112 described above form a DC path. The capacitors 120 and 122 are bypass capacitors.

Between the output terminal 86 of the operation portion substrate 80 and the ground potential point, a direct current adjusting means, for example, an open / close switch 126 is connected via a high frequency blocking coil 124, that is, in terms of direct current.

In the thus constructed booster, the high frequency signal received by the antenna or the like is supplied to the input terminal of the operation portion substrate 80, and the input of the main circuit substrate 74 is made via the capacitor 84, the output terminal 86 and the coaxial cable 88. It is supplied to the terminal 76. When the open / close switch 126 is closed in this state,
The base of the transistor 116 is the high frequency blocking coil 11
2. Since it is grounded via the coaxial cable 88, the high frequency blocking coil 124, and the open / close switch 126, the transistor 116 becomes non-conductive. As a result, the PIN diode 96 is also non-conductive, and its high frequency resistance value is large. On the other hand, from the base of the transistor 106 to the resistor 11
0, high-frequency high-frequency blocking coil 112, coaxial cable 8
8, the base current flows to the ground potential point through the high frequency blocking coil 124, the open / close switch 126, and the transistor 10
6 becomes conductive. As a result, the power supply terminal 101 and the resistor 10
0, the PIN diode 90, the resistor 102, and the transistor 106, a current flows, the PIN diode becomes conductive, and its high frequency resistance value becomes very small.

Since the high frequency resistance value of the PIN diode 96 is large and the high frequency resistance value of the PIN diode 90 is very small as described above, the high frequency signal supplied to the input terminal 76 is hardly attenuated, and the capacitor 92 and PI are not attenuated.
It is input to the high frequency amplifier 72 via the N diode 90. The capacitor 92 and the high frequency blocking coil 112 constitute a separating means for separating a high frequency signal and a direct current signal. Similarly, the capacitor 84 and the high frequency blocking coil 124
Also constitutes a means for separating a high frequency signal and a DC signal.

When the open / close switch 126 is opened, a base current flows from the power supply terminal 101 through the resistor 118, and the transistor 116 becomes conductive. As a result, a current flows from the power supply terminal 101 to the collector-emitter conductive path of the transistor 116, the resistor 114, and the PIN diode 96, and the high frequency resistance value of the PIN diode 96 becomes
Become smaller. On the other hand, since the open / close switch 126 is opened, the base current of the transistor 106 does not flow, and the transistor 106 is non-conductive. Therefore, current flows from the power supply terminal 101 to the resistor 100, the PIN diode 90, and the resistors 102 and 104, and the PIN diode 90
Since the current flowing through is smaller than that when the open / close switch 126 is closed, the high frequency resistance value becomes large.

Since the high frequency resistance value of the PIN diode 96 is small and the high frequency resistance value of the PIN diode 90 is large, the high frequency signal supplied to the input terminal 76 is greatly attenuated and supplied to the high frequency amplifier 72. It

In the state where the high frequency signal is attenuated as described above, the characteristic impedance of the variable attenuator 70 seen from the input terminal 76 and the characteristic impedance of the variable attenuator 70 seen from the input side of the high frequency amplifier 72 are as follows. Resistor 1 so that each maintains a specific value, for example 75 ohms
Adjusting the values of 14, 104, PIN diode 96,
The high frequency resistance value of 90 is adjusted.

FIG. 2 is a block diagram of a booster for receiving a television broadcast signal using the high frequency amplifier with a variable attenuator shown in FIG. The main circuit board 74 is provided with the variable attenuator 70 and the high frequency amplifier 72 as in the case of FIG. A band pass filter 128 is provided for extracting a high frequency television broadcast signal when the frequency band of the television broadcast is divided into a high frequency band and a low frequency band.

Further, the high-frequency blocking coil 112 forming a part of the DC path described above is connected to the input side of the bandpass filter 128, and the input side of the bandpass filter 130 of the operation section substrate 80 is connected via the coaxial cable 88. It is connected to the. The input side of the bandpass filter 130 is connected to the input terminal 82 via the DC blocking capacitor 84. Also, on the input side of the bandpass filter 130,
As in FIG. 1, the high frequency blocking coil 124 and the open / close switch 126 are connected. This bandpass filter 13
The pass band of 0 is selected so as to pass a band which does not need to be amplified by the high frequency amplifier 72, for example, the above low band. The output side of the bandpass filter 130 has a high-frequency amplifier 7 extracted by the coaxial cable 132.
2 is connected to the output side and is connected to the output terminal 134 provided on the operation unit substrate 80.

FIG. 3 shows the gain-frequency characteristic of such a booster, and the low-frequency television broadcast signal passes through as it is. On the other hand, the high-frequency television broadcast signal has a large gain as shown by the solid line when not attenuated by the variable attenuator 70, but has a large gain as shown by the dotted line when attenuated by the variable attenuator 70. Becomes smaller.

Such a booster can be provided in a casing 136 as shown in FIG. 4, for example. This case 1
The reference numeral 36 has a rear wall 138, which is used to attach the housing 136 to a support such as a wall, and an operation wall, for example, a front wall 140, which faces the rear wall 138. Input terminal 8
2, the operation unit substrate 80 provided with the output terminal 134 and the open / close switch 126 (only the open / close switch 126 is shown in FIG. 4) faces the front wall 140 in order to facilitate the operation. And are installed close to each other. The main circuit board 74 is attached to the rear side of the operation unit board 80. Although not shown, the main circuit board 74 and the operation unit board 80 are connected by coaxial cables 88 and 132. In this way, the main circuit board 7
4 and the operation unit substrate 80 are connected only by the two coaxial cables 88 and 132, and there is no need to perform special wiring in connection with the open / close switch 126. Further, the booster can be provided in the housing 136a as shown in FIG. 5, for example. The housing 136a has a front wall 140a,
The operation unit substrate 80 is provided so as to be opposed to and close to this. The main circuit board 74 is a bottom wall 1 that is perpendicular to the front wall 140a.
It is arranged so as to approach 42 and to face each other.
The connection between the main circuit board 74 and the operation unit board 80 is made only by the coaxial cables 88 and 132, as in the case of FIG.

In the above embodiment, as the DC adjusting means,
Although the open / close switch 126 is used, if a variable resistor is used instead of the open / close switch 126, the amount of attenuation can be adjusted steplessly. Further, in the above embodiment, the current control transistor is used as the conductive state changing means, but a voltage control FET may be used. In this case, the DC adjusting means may adjust the voltage of the DC path. Further, in the above embodiment, two PIN diodes are provided, but three PIN diodes are provided.
It is also possible to provide two PIN diodes to form a pie variable attenuator. Further, in the above embodiment, the DC path is connected to the input side coaxial cable 88, but the DC path may be connected to the output side coaxial cable 32.

[0033]

As described above, according to the first aspect of the invention, the DC path provided on the first substrate of the first and second substrates provided in one housing. Is connected to the DC adjusting means provided on the second substrate through the transmission line for originally transmitting the AC signal,
Since it is not necessary to provide a transmission line for the DC adjusting means between the first and second substrates, the manufacturing efficiency can be improved.

According to the second aspect of the present invention, the second substrate is provided close to the operation wall of the operation case, and the first substrate is provided in the case apart from the second board. It is significant that the transmission line for the DC adjusting means is not specially provided between the first and second substrates, and the manufacturing efficiency can be particularly improved.

According to the third aspect of the invention, the variable attenuating means is composed of two PIN diodes and two conducting state changing means, and the conducting state is set by operating the open / close switch which is the adjusting means. The conductivity of the adjusting means changes, the high frequency resistance value of the PIN diode changes accordingly, and the amount of attenuation changes. Since the conductive state adjusting means is provided in series with each PIN diode in this manner, the adjusting means does not require a voltage divider or the like, and a switch for simply turning the power supply on and off can be used. It can be simplified.

[Brief description of the drawings]

1 a high frequency amplifier with an attenuator according to the invention 1
It is a circuit diagram of an example.

FIG. 2 is a block diagram of a television broadcast receiving booster using the same embodiment.

3 is a gain vs. frequency characteristic diagram of the block diagram of FIG.

4 is a vertical cross-sectional view of the booster of FIG.

FIG. 5 is a perspective view of a modified example of the booster of FIG.

FIG. 6 is a circuit diagram of a television broadcast receiving booster including a conventional attenuator.

[Explanation of symbols]

 70 Variable Attenuator 74 Main Circuit Board (First Board) 80 Operation Section Board (Second Board) 90 96 PIN Diode 106 116 Transistor (Conductive State Adjusting Means) 108, 110, 118 Resistor (DC Path) 112 High Frequency Blocking coil (DC path) 126 Open / close switch (DC adjusting means) 136 Housing 138 First wall surface 140 Second wall surface

Claims (3)

[Claims] 1. A casing, first and second substrates provided in the casing, a direct current path provided on the first substrate, and having a direct current path according to a voltage or current value of the direct current path. Variable attenuation means for changing the attenuation state of the AC signal supplied from the input side and outputting from the output side, and the variable attenuation means provided on the second substrate and connected to the variable attenuation means via the transmission line of the AC signal. One end of the DC path is connected to one electrode of a DC power supply, and the other end is DC-connected to the transmission line on the first substrate, and the terminal and the power supply are connected. A variable attenuator in which a DC adjusting means for adjusting the voltage or current of the DC path is connected between the other electrode and the other in a DC manner. 2. The variable attenuator according to claim 1, wherein the housing has a first surface and a second surface different from the first surface, and faces the second substrate. It has operation walls arranged close to each other, the direct current adjusting means can be operated from the operation wall, and the first substrate is provided in the housing away from the second substrate. A variable attenuator. 3. The variable attenuator according to claim 1 or 2, wherein the DC adjusting means is an open / close switch, and the variable attenuating means is AC-connected between the input side and a reference potential point. A first PIN diode, a second PIN diode AC-connected between the input side and the output side, a conductive path and a control electrode for changing the conductive state of the conductive path, A first conductive state changing means that forms a first series circuit by connecting the conductive path to the first PIN diode in series in a direct current manner, and a conductive path and a control electrode that changes the conductive state of the conductive path. And a second conductive state changing means having a second serial circuit in which the conductive path is connected in series to the second PIN diode in a direct current manner, and The control electrode of the conductive state changing means of the Variable attenuator connected.