JP2001157125A - Rf switching circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an RF switching circuit capable of preventing RF signal of an antenna input from being distorted. SOLUTION: In this RF-switching circuit, which supplies A 2nd RF signal to a 2nd terminal 18 by turning on 1st and 2nd transistors Q1 to Q3 and supplies a 1st RF signal to the terminal 18 by turning off the 1st and 2nd transistors, the parts between bases and emitters of the 1st and 2nd transistors Q1 to Q3 are subjected to reverse bias, to completely interrupt the parts between collectors and the emitters because a negative voltage is supplied to the bases of the transistors Q1 to Q3, to turn on the transistors Q1 to Q3 so that the 1st RF signal can be prevented from being distorted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RF switch circuit, and more particularly, to an RF switch circuit for switching an RF (high frequency) signal.

[0002]

2. Description of the Related Art Conventionally, a VTR (Video Tape Recorder) or the like is provided with an RF modulator. When reproducing a VTR, the frequency of a VTR reproduction signal is converted to an RF signal and supplied to an antenna terminal of a television receiver. ing. In addition, an RF switch circuit is provided in the RF modulator to supply an antenna input to the antenna terminal of the television receiver when recording or stopping the VTR.

FIG. 4 shows a conventional R switch including an RF switch circuit.
FIG. 2 shows a circuit diagram of an example of an F modulator. In the figure, an antenna input terminal 10 is connected to an antenna,
Power supply + B is supplied from TR, and VT
An audio signal and a video signal are supplied from R, and ground terminals 11,
13 is grounded. Further, the RF output terminal 18 is connected to an antenna terminal of a television receiver.

The integrated circuit 20 operates by being supplied with a power supply + B from a terminal 12, performs multiplexing and frequency conversion of audio signals and video signals supplied from terminals 14 and 16, and performs RF conversion.
It generates a signal outputted from the fifth terminal 20 _5. Npn transistors Q1, Q2, Q forming an RF switch circuit
The bases 3 are supplied with power + B from a terminal 12 and turned on. The antenna input terminal 10 is connected to the ground terminal 11 by turning on the transistors Q1 and Q2, and the RF of the antenna input coming from the antenna input terminal 10 is turned on. signal is grounded, RF signal output from the fifth terminal 20 ₅ of the integrated circuit 20 by the on of the transistor Q3 is supplied to the RF output terminal 18, is supplied to the antenna terminal of the television receiver.

When the power supply + B is not supplied from the VTR to the terminal 12, the integrated circuit 20 stops operating and the transistors Q1, Q2 and Q3 are turned off. Transistor Q1, the antenna input terminal 10 by Q2 off is released from the ground terminal 11, pin 5 20 ₅ RF output terminal of the integrated circuit 20 by the off transistors Q3 1
The RF signal of the antenna input, which is released from the antenna input terminal 8 and enters from the antenna input terminal 10, is supplied from the RF output terminal 18 to the antenna terminal of the television receiver through the capacitors C1, C2, and C3.

[0006]

In the above conventional circuit,
When the power supply + B is not supplied to the terminal 12 from the VTR, the voltage of the terminal 12 becomes substantially 0 V, but the transistors Q1 and Q2
Have a residual voltage at the base of the transistor Q1,
Q2 was not completely off. For this reason, there is a problem that the collector-emitter of the transistors Q1 and Q2 is not completely cut off, and the RF signal of the antenna input supplied from the RF output terminal 18 to the antenna terminal of the television receiver is distorted.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been made in consideration of the above circumstances.
It is an object to provide a switch circuit.

[0008]

According to a first aspect of the present invention, a first terminal (10) to which a first RF signal received by an antenna is supplied and a second terminal connected to an antenna terminal of an external device are provided. A first transistor (Q1, Q2) having a collector connected to a signal line connecting the terminal (18) of the first transistor and a grounded emitter, a collector connected to the signal line, and a second RF connected to the emitter. A second transistor (Q3) to which a signal is supplied, and turning on the first and second transistors (Q1, Q2, Q3) to produce the second RF signal
An RF switch circuit for supplying a signal to the second terminal (18), turning off the first and second transistors and supplying the first RF signal to the second terminal (18); First and second transistors (Q1, Q2, Q
The base is turned off by supplying a negative voltage to the base.

As described above, by supplying a negative voltage to the bases of the first and second transistors (Q1, Q2, Q3), the base-emitter between the first and second transistors (Q1, Q2, Q3) is reduced. Is reverse-biased to completely shut off the collector and the emitter, thereby preventing the first RF signal from being distorted. Note that the reference numerals in the parentheses are provided for easy understanding, and are merely examples.

[0010]

FIG. 1 is a circuit diagram of a first embodiment of an RF modulator including an RF switch circuit according to the present invention.
4, the same parts as those in FIG. 4 are denoted by the same reference numerals. In FIG. 1, an antenna input terminal 10 is connected to an antenna, and a power supply + B is supplied to a terminal 12 from a VTR.
An audio signal and a video signal are supplied to the VTR 16 from the VTR, and the ground terminals 11 and 13 are grounded. Further, the RF output terminal 18 is connected to an antenna terminal of a television receiver. The antenna input terminal 10 and the RF output terminal 18 are connected via capacitors C1, C2, and C3.

The terminal 30 is always supplied with a voltage -E (-E is, for example, -1 V) from the VTR.
Is supplied to the terminal a of the switch 32. The terminal b and the control terminal of the switch 32 are connected to the terminal 12 and the switch 3
2 terminal c is connected to n via resistors R1, R2, coil L1, etc.
It is connected to the bases of pn transistors Q1, Q2, Q3. The switch 32 connects the terminals b and c when the power supply + B is supplied to the control terminal, and connects the terminals a and c when the power supply + B is not supplied to the control terminal. Transistor Q
Collectors 1 and Q2 are connected to one ends of the capacitors C1 and C2, respectively, and their emitters are connected to the ground terminal 11. The collector of the transistor Q3 is connected to the RF output terminal 18 via the capacitor C4, the emitter is connected in parallel with the coil L2 and the capacitor C5, and connected to the _fifth terminal 205 of the integrated circuit 20 via the resistor R5 and the capacitor C6. I have.

When a power supply + B is supplied to the terminal 12 from the VTR, the integrated circuit 20 operates by receiving the power supply + B from the terminal 12, and multiplexes the audio signal and the video signal supplied from the terminals 14 and 16. It converts the frequency output from the RF signal (second RF signal) pin 5 20 ₅ to produce the. Further, the switch 32 is supplied with power + B to the control terminal, connects the terminals b and c, and connects the transistors Q1, Q2,
Supply power + B to the base of Q3. This gives R
Transistors Q1, Q2, Q constituting an F switch circuit
3 is turned on, the antenna input terminal 10 is connected to the ground terminal 11 by turning on the transistors Q1 and Q2, and the RF signal (first RF signal) of the antenna input coming from the antenna input terminal 10 is grounded, and the transistor Q3 is turned on. RF signal output by turning on the fifth terminal 20 ₅ of the integrated circuit 20 is supplied to the RF output terminal 18, it is supplied to the antenna terminal of the television receiver.

When the power supply + B is not supplied to the terminal 12 from the VTR, the integrated circuit 20 stops operating. At this time, the switch 32 connects the terminals a and c without supplying the power + B to the control terminal, and supplies the voltage -E to the bases of the transistors Q1, Q2, and Q3. Therefore, the bases and the emitters of the transistors Q1, Q2, and Q3 are reverse-biased, and the transistors Q1 and Q1, which constitute the RF switch circuit,
Q2 and Q3 are completely turned off.

The antenna input terminal 10 is opened from the ground terminal 11 by turning off the transistors Q1 and Q2, and the fifth terminal 2 of the integrated circuit 20 is turned off by turning off the transistor Q3.
0 ₅ is opened from the RF output terminal 18, RF signals of antenna input coming from the antenna input terminal 10 is supplied from the RF output terminal 18 through a capacitor C1, C2, C3 to the antenna terminal of the television receiver. As described above, since the collector and the emitter of the transistors Q1 and Q2 are completely cut off, distortion of the RF signal of the antenna input supplied from the RF output terminal 18 to the antenna terminal of the television receiver can be prevented.

FIG. 2 is a circuit diagram of an R switch including the RF switch circuit of the present invention.
FIG. 4 shows a circuit diagram of a second embodiment of the F modulator. In the figure,
1 are given the same reference numerals. In FIG. 2, the antenna input terminal 10 is connected to the antenna. A power supply + B is supplied to the terminal 34 from the VTR at the time of reproduction, and a voltage -E (-E is, for example, -1 V) is supplied at times other than the reproduction. This terminal 34 is an npn transistor via resistors R1, R2, coil L1 and the like. It is connected to the bases of Q1, Q2, and Q3, and to the terminal a and the control terminal of the switch 36.

Further, audio signals and video signals are supplied to terminals 14 and 16 from a VTR, and ground terminals 11 and 13 are grounded. Further, the RF output terminal 18 is connected to an antenna terminal of a television receiver. A capacitor C1 is connected between the antenna input terminal 10 and the RF output terminal 18.
They are connected via C2 and C3. Switch 3 above
6 terminal b is is connected to one end of a capacitor C10~C16 of and connected to the power supply terminal 20 ₁ of the integrated circuit 20. The switch 36 connects the terminals a and b when the power supply + B is supplied to the control terminal, and opens the terminals a and b when the voltage −E is supplied to the control terminal.

The collectors of the transistors Q1 and Q2 are connected to one ends of the capacitors C1 and C2, respectively.
Each emitter is connected to a ground terminal 11.
The collector of the transistor Q3 is connected to the RF output terminal 18 via a capacitor C4, the emitter is a parallel connection of a coil L2 and a capacitor C5, a resistor R5 and a capacitor C6.
Is connected to the _fifth terminal 205 of the integrated circuit 20 via the.

When the power supply + B is supplied from the VTR to the terminal 34, the terminals a and b of the switch 36 are connected, and the integrated circuit 20 is operated by the power supply + B supplied from the switch 36 and supplied from the terminals 14 and 16. It is subjected to multiple and frequency conversion of the audio signal and the video signal outputted from the fifth terminal 20 ₅ to generate an RF signal. In addition, transistors Q1, Q
2, the power supply + B is supplied to the base of Q3, the transistors Q1, Q2, and Q3 constituting the RF switch circuit are turned on. When the transistors Q1 and Q2 are turned on, the antenna input terminal 10 is connected to the ground terminal 11 and the antenna input terminal The RF signal of the antenna input coming from 10 is grounded, and the transistor Q3 is turned on so that the 5
RF signal RF output terminal that is output from the turn pin 20 ₅ 1
8 and supplied to the antenna terminal of the television receiver.

When the voltage -E is supplied from the VTR to the terminal 34, the terminal a and the terminal b of the switch 36 are opened.
The integrated circuit 20 stops operating. Since the voltage -E supplied to the terminal 34 is supplied to the bases of the transistors Q1, Q2, Q3, the bases and the emitters of the transistors Q1, Q2, Q3 are reverse-biased, and the transistors Q1, Q2 and Q3 are completely turned off.

The antenna input terminal 10 is opened from the ground terminal 11 by turning off the transistors Q1 and Q2, and the fifth terminal 2 of the integrated circuit 20 is turned off by turning off the transistor Q3.
0 ₅ is opened from the RF output terminal 18, RF signals of antenna input coming from the antenna input terminal 10 is supplied from the RF output terminal 18 through a capacitor C1, C2, C3 to the antenna terminal of the television receiver. As described above, since the collector and the emitter of the transistors Q1 and Q2 are completely cut off, distortion of the RF signal of the antenna input supplied from the RF output terminal 18 to the antenna terminal of the television receiver can be prevented.

FIG. 3 is a circuit diagram of an R including an RF switch circuit according to the present invention.
FIG. 4 shows a circuit diagram of a third embodiment of the F modulator. In the figure,
1 are given the same reference numerals. In FIG. 3, an antenna input terminal 10 is connected to an antenna, and a power supply + B is constantly supplied to a terminal 12 from a VTR.
6 is supplied with an audio signal and a video signal from the VTR, and the ground terminals 11 and 13 are grounded. Further, the RF output terminal 18 is connected to an antenna terminal of a television receiver. The antenna input terminal 10 and the RF output terminal 18 are connected via capacitors C1, C2, and C3.

The terminal 40 is connected to an antenna terminal of the VTR. The antenna input terminals 10 are coils L6, L7
Is connected to one end of the capacitor C1 via a resistor R6, and further connected to a terminal 40 via a resistor R6. Terminal 4
2 is supplied with a control signal from the VTR, and this control signal is supplied to the _thirteenth terminal 5013 of the integrated circuit 50. The 14th terminal of the integrated circuit 50 is connected to the bases of the npn transistors Q1, Q2, Q3 via resistors R10, R1, R2, coil L1 and the like. The integrated circuit 50 has the 13th terminal 5
When a control signal for reproducing instruction is supplied to 0 ₁₃ ,
0 ₁₄ outputs a voltage + B (e.g., + 5V) from, and outputs a voltage -E 13 Pin 50 when ₁₃ is supplied a control signal for recording or stop instruction to the Pin 14 50 _14. The collectors of the transistors Q1 and Q2 are connected to the capacitors C1 and
C2 is connected to one end of each, and each emitter is connected to the ground terminal 11. The collector of the transistor Q3 is connected to the RF output terminal 18 via the capacitor C4, and the emitter is connected in parallel with the coil L2 and the capacitor C5, and the integrated circuit 50 is connected via the resistor R5 and the capacitor C6.
It is connected to the 15th pin 50 _{1 5.}

When a reproduction instruction control signal is supplied from the terminal 42, the integrated circuit 50 performs multiplexing and frequency conversion of the audio signal and the video signal supplied from the terminals 14 and 16 to perform RF conversion.
To generate a signal output from the 15 Pin 50 _{1 5.} The integrated circuit 50 is supplied from the 14 Pin 50 ₁₄ voltage + B to the base of the transistor Q1, Q2, Q3. Thereby, the transistor Q constituting the RF switch circuit
1, Q2 and Q3 are turned on, and the antenna input terminal 10 is connected to the ground terminal 11 by turning on the transistors Q1 and Q2, the RF signal of the antenna input coming from the antenna input terminal 10 is grounded, and the transistor Q3 is turned on. R output from 15 pin 50 _{1 5} of the integrated circuit 50
The F signal is supplied to the RF output terminal 18 and supplied to the antenna terminal of the television receiver.

When a recording or stop instruction control signal is supplied from the terminal 42, the integrated circuit 50 stops the multiplexing and frequency conversion operations. The integrated circuit 50 14 Pin 50 ₁₄ transistor Q1 the voltage -E from, Q2, Q3
Supply to the base. Thereby, the transistor Q
The transistors Q1, Q2 constituting the RF switch circuit are reverse-biased between the base and the emitter of the transistors Q1, Q2, Q3.
2 and Q3 are completely turned off.

When the transistors Q1 and Q2 are turned off,
When the antenna input terminal 10 is released from the ground terminal 11,
Terminal 15 of integrated circuit 50 by turning off transistor Q3
50 _{1 5}Is opened from the RF output terminal 18 and the antenna input
The RF signal of the antenna input coming from the input terminal 10
From the RF output terminal 18 through the capacitors C1, C2 and C3
It is supplied to the antenna terminal of the revision receiver. This
Thus, between the collector and emitter of the transistors Q1 and Q2
Is completely shut off, so that the
The antenna input supplied to the antenna terminal of the vision receiver
Distortion of the force RF signal can be prevented.

The antenna input terminal 10 corresponds to the first terminal, the RF output terminal 18 corresponds to the second terminal, the transistors Q1 and Q2 correspond to the first transistor, and the transistor Q3 Corresponds to the second transistor.

[0027]

As described above, the first aspect of the present invention provides
A collector is connected to a signal line connecting between a first terminal supplied with the first RF signal received by the antenna and a second terminal connected to the antenna terminal of the external device, and the emitter is grounded. A first transistor having a collector connected to the signal line and a second transistor supplied with a second RF signal to an emitter, turning on the first and second transistors to generate the second transistor; An RF switch circuit that supplies an RF signal to the second terminal, turns off the first and second transistors, and supplies the first RF signal to the second terminal. The transistor is turned off by supplying a negative voltage to the base of the transistor.

Thus, by supplying a negative voltage to the bases of the first and second transistors, the base and emitter of the first and second transistors are reverse-biased, and the collector and emitter are completely cut off. Thus, the first RF signal can be prevented from being distorted.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of an RF modulator including an RF switch circuit according to the present invention.

FIG. 2 is a circuit diagram of an RF modulator including an RF switch circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of an RF modulator including an RF switch circuit according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram of an example of an RF modulator including a conventional RF switch circuit.

[Explanation of symbols]

 Reference Signs List 10 antenna input terminal 18 RF output terminal 20, 50 integrated circuit 32, 36 switch C1-C4 capacitor Q1, Q2, Q3 npn transistor L1, L2 coil R1-R10 resistance

Continued on front page F-term (reference) 5C025 AA22 BA09 BA21 CA15 DA08 5J012 BA04 5J055 AX05 AX53 AX66 BX03 CX03 DX04 DX55 DX83 EX06 EX22 EY01 EY05 EY10 EY17 FX12 FX17 FX36 GX01 5K062 AA06 AB01 BB06 BB06

Claims (1)

[Claims] A collector connected to a signal line connecting between a first terminal to which a first RF signal received by an antenna is supplied and a second terminal connected to an antenna terminal of an external device; A first transistor having an emitter grounded; a second transistor having a collector connected to the signal line and having a second RF signal supplied to the emitter; turning on the first and second transistors; An RF switch circuit that supplies the second RF signal to the second terminal and turns off the first and second transistors to supply the first RF signal to the second terminal. An RF switch circuit, wherein a negative voltage is supplied to the bases of the first and second transistors to turn them off.