JP2579651Y2 - Signal switching circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal switching circuit, and more particularly to a signal switching circuit for switching an input high-frequency signal and selectively outputting the signal.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram of a part of a channel selection circuit to which an example of a conventional signal switching circuit for high frequency signals is applied.
In the figure, 10 shows a conventional signal switching circuit, an intermediate frequency signal a is input high frequency signal amplified by the transistor Q _1, the control signal input terminal 5 and 11
Is output to one of the output terminals 3 and 4 according to the binary control signal input to.

The intermediate frequency signal a is, for example, 12
950-18 in the GHz band
This intermediate frequency signal is converted to a high frequency signal of the 00 MHz band, amplified, mixed with a local oscillation frequency whose oscillation frequency is controlled by desired channel data, and frequency-converted to 402.78 MHz.

This intermediate frequency signal a has a bandwidth of 27 MHz in the case of a Japanese broadcasting satellite. But,
As is well known, the bandwidth of a commercial communication satellite may differ depending on the satellite. For example, in the case of "JC-SAT", the bandwidth is 27 MHz as in the case of the broadcast satellite, whereas in the case of "super bird", the bandwidth is 36 MHz.

Therefore, the intermediate frequency signal a of the communication satellite to be received is supplied to the output terminals 3 and 4 of the signal switching circuit 10, respectively.
The surface acoustic wave filters 6 and 7 having different passbands in accordance with the bandwidths are connected to limit a predetermined band to prevent noise. Hereinafter, the circuit of FIG. 2 will be briefly described.

[0006] The transistor Q ₁ is in total over the scan input terminal 2
More intermediate frequency signal a is input RF signal through a capacitor C _5, and outputs the collector amplifies the intermediate frequency signal a. The collector of the transistor Q ₁ is connected to the power supply voltage V _CC2 via the resistor R ₄ (+ 12V).

On the other hand, the diodes D ₁ and D ₅ have their commonly connected cathodes grounded via a resistor R _3, and the output intermediate frequency signal a of the transistor Q ₁ is passed through a capacitor C ₆ to the diodes D ₁ and D 5. It is supplied to ₅ common connection points.

The anodes of the diodes D ₁ and D ₅ are:
They are connected to control signal input terminals 5 and 11 via resistors R ₁ and R ₂ . The control signal input terminals 5 and 11 are supplied with binary control signals V _C1 and V _C2 that set + 12V to a high level and 0V to a low level according to the communication satellite to be received.

When V _C1 is high and V _C2 is low, the diode D ₁ is turned on and the diode D ₅ is turned off, so that the intermediate frequency signal a is output to the output terminal 3 via the capacitor C _1. .

At this time, since V _C1 becomes high level, the diode D ₃ disposed between the output of the surface acoustic wave filter 6 and the output terminal 8 turns on, and the output of the surface acoustic wave filter 7 and the output terminal transistor Q ₄ which is arranged between the 8 are turned off. Therefore, the intermediate-frequency signal a is bandwidth limited to pass through the surface acoustic wave filter 6, is output to the output terminal 8 via the diode D _3.

[0011] When V _C1 is at a low level V _C2 is at high level, the diode D ₅ is turned on to diode D ₁ is turned off, an intermediate frequency signal a is outputted to the output terminal 4 via a capacitor C ₂ . At this time, since V _C1 becomes low level, the diode D ₃ is turned off and the transistor Q ₄ operates to amplify the band-limited intermediate frequency signal a passing through the surface acoustic wave filter 7 to adjust the gain. And outputs it to the output terminal 8.

The intermediate frequency signal a which has been subjected to a predetermined band limitation and output to the output terminal 8 is amplified and then FM-demodulated to extract a desired signal.

[0013]

However, in a conventional signal switching circuit, a resistor R ₁ is used to switch a signal.
It requires components of R ₃ and R ₅ and diodes D ₁ and D ₅ ,
Power consumption by the resistor R ₃ also can not be ignored. Also, two types of control signals, V _C1 and V _C2 , were required.

In view of the above, it is an object of the present invention to provide a signal switching circuit that can reduce the number of components and power consumption and can switch signals with one type of control signal.

[0015]

In order to solve the above-mentioned problems, the present invention provides a coil having one end connected to a power supply voltage.
And amplify the input high frequency signal and supply it to the other end of the coil
Connection point of the amplifier circuit, and the coil and the amplifier circuit
A first diode having a cathode connected to the carp
The anode is connected to the connection point between the
Two diodes and a binary control signal at one end
A first end connected to the anode of the first diode;
And the binary control signal is input to one end and the other end is
A second resistor to which the cathode of the second diode is connected
And wherein the binary control signal is at a first level.
Connection between the first diode and the first resistor
A point between the second diode and the second resistor.
The potential of the connection point is higher than the power supply voltage by the first diode.
Larger than the forward on-state voltage of the
Turn on the diode, turn off the second diode,
When the value control signal is at the second level, the first diode
A connection point between the diode and the first resistor, and the second die
The potential at the connection point between the diode and the second resistor is equal to the power supply voltage.
Voltage which is equal to or higher than the forward ON voltage of the second diode.
The first diode is turned off, and the second diode is turned off.
Turn on the diode, and apply the input high frequency signal to the first
A connection point between an electrode and the first resistor or the second
Select one of the connection points between the diode and the second resistor
Output the binary control signal and the power supply voltage.
Be determined .

[0016]

According to the present invention, one of the first diode whose cathode is biased by the power supply voltage and the second diode whose anode is biased by the power supply voltage is turned on by the binary control signal. The input high-frequency signal amplified by the transistor acts so as to be selectively output to the other end of one of the first and second resistors.

[0017]

1 is a circuit diagram of a part of a tuning circuit to which an embodiment of the present invention is applied. 2, the same components as those in FIG. 2 are denoted by the same reference numerals. In FIG. 1, reference numeral 1 denotes a signal switching circuit according to an embodiment of the present invention, which converts an intermediate frequency signal a, which is an input high frequency signal amplified by a transistor Q ₁ , into a binary signal input to a control signal input terminal 5. The signal is output to one of the output terminals 3 and 4 according to the control signal.

[0018] The transistor Q ₁ is in total over the scan input terminal 2
More intermediate frequency signal a is input RF signal through a capacitor C _5, and outputs the collector amplifies the intermediate frequency signal a. The collector of the transistor Q ₁ is connected to the power supply voltage V _CC1 via the coil L ₁ (+ 5V). Collector load of the transistor Q ₁ is a coil load in order to match the operating point with respect to the power supply voltage V _CC1 of + 5V.

On the other hand, the cathode of the diode D1 as the _first diode and the diode D1 as the second diode
The _second anode is connected directly connected in common to the collector of the transistor Q _1.

The anode of the diode D ₁ is connected to a control signal input terminal 5 via a resistor R ₁ which is a first resistor, and the cathode of the diode D ₂ is connected to a control signal input terminal 5 via a resistor R ₂ which is a second resistor. It is connected. The control signal input terminal 5 is supplied with a binary control signal V _C1 whose state changes according to the bandwidth of the receiving communication satellite. The binary control signal V _C1 is
+ 12V is at a high level, and 0V is at a low level.

Therefore, when the binary control signal V _C1 becomes high level (+12 V), the diode D ₁ has its anode connected to +12 V V _C1 through the resistor R ₁ and its cathode connected to +5 V V through the coil L ₁ . It is turned on because it is connected to the power supply voltage V _CC1 and is forward biased.

On the other hand, at this time, the diode D ₂ has its cathode connected to +12 V V _C1 via the resistor R ₂ and its anode connected to the +5 V power supply voltage V _CC1 via the coil L ₁ and is reverse biased. Turn off. Therefore, the intermediate frequency signal a amplified by the transistor Q ₁ is output to the output terminal 3 via the diode D ₁ and the capacitor C ₁ and is supplied to the surface acoustic wave filter 6.

At this time, since V _C1 is at the high level, the diode D ₃ is turned on and the transistor Q ₄ is turned off. Therefore, the intermediate-frequency signal a after being a predetermined band restriction through the surface acoustic wave filter 6, is output to the output terminal 8 via the diode D _3.

When the binary control signal V _C1 is at a low level (0
V), the diode D ₁ has an anode grounded via a resistor R ₁ and a cathode connected to +5 V via a coil L _1.
Off to be connected to the power supply voltage V _CC1 in reverse bias.

Further, the diode D ₂ has a cathode connected to a resistor R
Via ₂ is grounded, the anode through the coil L ₁ +
It is turned on because it is connected to the power supply voltage V _{CC1 of} 5 V and is forward biased. Therefore, the intermediate-frequency signal a amplified by the transistor Q ₁ is, the diode D ₂ and the capacitor C
_{The signal} is output to the output terminal 4 via ₂ and supplied to the surface acoustic wave filter 7.

On the other hand, when V _C1 is at a low level, the diode D ₃ is turned off and the transistor Q ₄ operates to pass the band-limited intermediate frequency signal a through the surface acoustic wave filter 7.
Is amplified to adjust the gain and output to the output terminal 8.

As described above, according to the above embodiment, a circuit having a smaller number of components than a conventional signal switching circuit can be used.
The intermediate frequency signal a, which is an input high-frequency signal, is amplified, output to one of two types of surface acoustic wave filters having different pass bandwidths by a binary control signal, and subjected to band limitation according to the bandwidth, thereby increasing the gain. It can be adjusted and output to the output terminal.

[0028]

As described above, according to the present invention, it is possible to select and output an input high-frequency signal by using a single type of binary control signal by using a circuit having a smaller number of components than in the prior art. Therefore, there is an advantage that power consumption can be reduced as compared with the conventional circuit.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a part of a tuning circuit to which an embodiment of the present invention is applied.

FIG. 2 is a circuit diagram of a part of a channel selection circuit to which an example of a conventional signal switching circuit for a high-frequency signal is applied.

[Explanation of symbols]

1,10 signal switching circuit Q ₁ transistor L ₁ coil R ₁ resistor (first resistor) R ₂ resistor (second resistor) D ₁ diode (first diode) D ₂ diodes (second diode) V _C1 Binary control signal V _CC1 power supply voltage

Claims (1)

(57) [Scope of request for utility model registration] 1. A coil having one end connected to a power supply voltage and an input high-frequency signal amplified and supplied to the other end of the coil.
A cathode is connected to an amplifier circuit and a connection point between the coil and the amplifier circuit.
Anode is connected to the connected first diode and a connection point between the coil and the amplifier circuit.
A second control signal is input to one end and the first diode is connected to the other end.
A first resistor to which an anode of an anode is connected; the binary control signal input to one end;
A second resistor connected to the cathode of the diode.
When the binary control signal is at the first level, the first
A connection point between an electrode and the first resistor;
The potential at the connection point between the diode and the second resistor is
A forward ON voltage of the first diode from the power supply voltage;
As described above, when the first diode is turned on,
Turning off the second diode, and the binary control signal
At the level, the first diode and the first resistor
And the second diode and the second
The potential at the connection point with the resistor is higher than the power supply voltage by the second
It becomes smaller than the forward ON voltage of the
Turning off the second diode, turning on the second diode,
The input high-frequency signal is supplied to the first diode and the first
Or the second diode and the second node.
Selective output to one of the connection points with the resistor
A signal switching circuit configured to set a binary control signal and the power supply voltage .