JPH11346180A - Signal switching circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the wiring of a signal switching circuit which alternatively outputs one signal out of plural signals. SOLUTION: This circuit is composed of a left circularly polarized wave reception antenna 2 for receiving a left circularly polarized wave in a radio wave, a right circularly polarized wave reception antenna 3 for receiving a right circularly polarized wave in the radio wave, an amplifier circuit 4, an amplifier circuit 5, a band-pass filter 6 for having only the necessary components from an amplified reception signal pass through, an amplifier circuit 7, a capacitor C1 which is provided between the amplifier circuit 7 and an output terminal Tout and eliminates a DC component, a regulator circuit 8 which converts a bias voltage to the output terminal Tout into a specified voltage, a voltage detection circuit 9 which detects the bias voltage of an output terminal Tout and generates a control signal that becomes a high or a low level, and a changeover switch 10 which switches the bias voltage to the output terminal Tout to the drive voltage of the amplifier circuit 4 or the amplifier circuit 5, in accordance with the control signal generated by the voltage detection circuit 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a signal switching circuit, and more particularly, to a signal switching circuit for selectively outputting one signal from a plurality of signals.

[0002]

2. Description of the Related Art In recent years, with the development of digital technology,
DAB (Digital) which is a digitized radio broadcast
Audio Broadcasting) is being developed. DAB broadcasting uses satellite waves or terrestrial waves, and is configured to be capable of mobile reception. For this reason, as an antenna for receiving DAB broadcast radio waves, a planar antenna that can be miniaturized and that can be easily mounted has attracted attention.

In order to maintain a good reception state even while moving, a plurality of reception surfaces for receiving circularly polarized waves having different directions are provided on a planar antenna so that radio waves in a good reception state can be selectively received. Antenna units have been proposed. Such an antenna unit has a built-in signal switching circuit for selecting one reception signal from signals received from a plurality of reception surfaces in order to select a reception surface according to a reception state.

FIG. 4 shows a schematic configuration diagram of an example of the related art. The antenna unit 100 is connected to a receiving unit 200 that demodulates a received signal received by the antenna unit 100. Antenna unit 100 and receiving unit 200
Is a control for supplying a reception signal received by a planar antenna built in the reception unit 200 and selecting a signal line 300 for supplying driving power to the antenna unit 100 and a reception surface for receiving a broadcast wave by the antenna unit 100. It is connected to a control line 400 for supplying a signal.

FIG. 5 shows a block diagram of a conventional antenna unit. The antenna unit 100 includes a left-handed circularly polarized reception antenna 1 for receiving left-handed circularly polarized waves in radio waves.
10. Right-handed circularly polarized wave receiving antenna 120 for receiving right-handed circularly polarized wave in radio wave, first amplifier circuit 130 for amplifying left-handed circularly polarized wave reception signal received by left-handed circularly polarized wave receiving antenna 110 A second amplification circuit 140 that amplifies the right-handed circularly polarized wave reception signal received by the right-handed circularly polarized wave reception antenna 120;
A changeover switch 150 for selecting and outputting one of the received signals from the received signals amplified by the first amplifier circuit 130 or the second amplifier circuit 140, and passing only necessary components from the received signals selected by the changeover switch 150. It comprises a band-pass filter 160 and an output amplifier circuit 170 for amplifying a signal passed through the band-pass filter 160.

[0006] Left-handed circularly polarized receiving antenna 110, and
The right-handed circularly polarized wave receiving antenna 120 is formed on the same substrate as a planar antenna, for example. The left-handed circularly polarized reception signal received by the left-handed circularly polarized reception antenna 110 is the first
Is supplied to the amplifier circuit 130 of FIG. First amplifier circuit 130
Is composed of an LNA (Low Noise Amplifier), amplifies the left-handed circularly polarized wave reception signal supplied from the left-handed circularly polarized wave reception antenna 110, and supplies the signal to the changeover switch 150.

[0007] The right-handed circularly polarized reception signal received by the right-handed circularly polarized wave receiving antenna 120 is supplied to a second amplifier circuit 140. The second amplifier circuit 140 has an LNA (Low Noise).
Amplifier), amplifies the right-handed circularly polarized reception signal supplied from the right-handed circularly polarized wave receiving antenna 120,
It is supplied to the changeover switch 150. Selector switch 150
Is a signal passing type switch IC (Integrated Circuit)
it), and outputs the output signal of the first amplifier circuit 130, that is, the left circularly polarized reception signal, or the second amplifier circuit 140 in accordance with the control signal supplied to the control terminal Tcont.
, Ie, one of the right-hand circularly polarized reception signals. The output signal of the changeover switch 150 is supplied to the band pass filter 160.

[0008] The band-pass filter 160 extracts a signal component of a required band from the received signal supplied from the changeover switch 150. The output signal of bandpass filter 160 is
It is supplied to the output amplifier circuit 170. Output amplification circuit 170
Amplifies the received signal selected by the band-pass filter 160 and supplies it to the output terminal Tout. FIG. 6 is a diagram illustrating the operation of an example of a conventional antenna unit. FIG. 6 (A)
6 is a control signal supplied to the control terminal Tcont, FIG.
6B is a diagram showing the switching state of the changeover switch 150, and FIG. 6C is a diagram showing the output state of the signal at the output terminal Tout.

At time t10, when the control signal supplied to the control terminal Tcont is at a low level as shown in FIG. 6A, the input terminal c of the changeover switch 150 is connected to the output terminal a. When the input terminal c of the changeover switch 150 is connected to the output terminal a, the first amplifying circuit 13
0 is connected to the band-pass filter 160.
Therefore, as shown in FIG. 6B, the left-handed circularly polarized reception signal received by the left-handed circularly polarized wave receiving antenna 110 is supplied to the output terminal Tout via the band-pass filter 160 and the amplifier circuit 170. You.

Next, at time t11, when the control signal supplied to the control terminal Tcont goes high as shown in FIG. 6A, the input terminal c of the changeover switch 150 is connected to the output terminal b. When the input terminal c of the changeover switch 150 is connected to the output terminal b, the second amplifier circuit 140 is connected to the band-pass filter 160. Therefore, as shown in FIG. 6B, the right-handed circularly polarized wave reception signal received by the right-handed circularly polarized wave receiving antenna 120 is transmitted to the output terminal Tout via the band-pass filter 160 and the amplifier circuit 170. Supplied.

[0011]

However, the conventional signal switching circuit requires a control line for supplying a switching control signal in addition to a signal line for supplying a DC-biased main signal. There have been problems such as complicated wiring and high cost. Further, since the signal passing type changeover switch 150 is inserted between the signal lines through which the reception signal passes, there is a problem that the reception signal loss due to the changeover switch 150 occurs.

The present invention has been made in view of the above points, and has as its object to provide a signal switching circuit capable of simplifying wiring.

[0013]

According to a first aspect of the present invention, there is provided a signal switching circuit for selecting one input signal from input signals input to a plurality of input terminals and outputting the selected signal from an output terminal. A voltage detection unit that detects a voltage, the voltage detection unit is connected between the plurality of input terminals and the output terminal, and among the plurality of input terminals according to a result of detection of a voltage of the output terminal by the voltage detection unit; Switching means for selectively connecting any one of the output terminals is provided.

According to the first aspect, the voltage of the output terminal is detected by the voltage detecting means, the voltage is connected between the plurality of input terminals and the output terminal by the switching means, and the detection result of the voltage of the output terminal is detected by the voltage detecting means. The signal can be switched by controlling the bias voltage of the output terminal by selectively connecting one of the plurality of input terminals to the output terminal according to the control signal, and a dedicated control line for performing the switching. Is unnecessary, so that the wiring can be simplified.

[0015]

FIG. 1 is a block diagram showing an embodiment of the present invention. In this embodiment, the signal switching circuit is DAB
(Digital Audio Broadcasting) An embodiment provided in the receiving antenna unit 1 will be described. The antenna unit 1 includes a left-handed circularly polarized wave receiving antenna 2 that receives left-handed circularly polarized waves in radio waves, a right-handed circularly polarized wave receiving antenna 3 that receives right-handed circularly polarized waves in radio waves, and a left-handed circularly polarized wave reception. Amplifying circuit 4 for amplifying the left-handed circularly polarized reception signal received by the antenna 2 for reception, and the second amplification for amplifying the right-handed circularly polarized reception signal received by the right-hand circularly polarized reception antenna 3 A circuit 5, a band-pass filter 6 for passing only necessary components from a received signal amplified by the first amplifier circuit 4 or the second amplifier circuit 5, an amplifier circuit 7 for amplifying a signal passing through the band-pass filter 6,
A capacitor C1 provided between the amplifier circuit 7 and the output terminal Tout for removing a DC component; a regulator circuit 8 for converting a bias voltage supplied to the output terminal Tout to a predetermined voltage; a bias voltage supplied to the output terminal Tout Is provided between the band-pass filter 6 and the voltage detection circuit 9 for generating a control signal of a high or low level in accordance with the bias voltage. A changeover switch 10 for selectively outputting the output of the first amplifier circuit 4 or the output of the second amplifier circuit 5 to the band-pass filter 6 in response to a control signal of the circuit 9, and an output terminal Tout
, And a second noise filter L2 that removes a signal component from the voltage of the output terminal Tout, and a second noise filter L2 that removes a signal component from the voltage of the first amplifier circuit 4 and supplies the signal component as a drive voltage of the first amplifier circuit 4. It is composed of a resistor R that drops the voltage from which the signal component has been removed by the noise filter L2 and supplies it to the second amplifier circuit 4 as a drive voltage. Left circularly polarized wave receiving antenna 2 and right circularly polarized wave receiving antenna 3
Is formed, for example, by separately forming a conductive thin film for a left-handed circularly polarized wave receiving antenna and a conductive thin film for a right-handed circularly polarized wave receiving antenna on the same insulating substrate in an insulated state. The conductive thin film for the left-handed circularly polarized wave receiving antenna is formed so as to easily receive the left-handed circularly polarized wave, and the conductive thin film for the right-handed circularly polarized wave receiving antenna is made easy to receive the right-hand circularly polarized wave. Formed.

The left-handed circularly polarized wave reception signal received by the left-handed circularly polarized wave receiving antenna 2 is supplied to a first amplifier circuit 4. The first amplifier circuit 4 includes an LNA (Low Noise Amplifier).
r), amplifies the left-hand circularly polarized reception signal supplied from the left-hand circularly polarized wave receiving antenna 2 and supplies the amplified signal to the band-pass filter 6. The first amplifier circuit 4 has an output terminal T
A drive voltage is supplied from out through a noise filter L1. The first amplifier circuit 4 has a predetermined driving voltage (2
When [V]) is applied, it operates normally,
The right-handed circularly polarized reception signal supplied from the left-handed circularly polarized wave receiving antenna 2 is amplified and supplied to the terminal Ta of the switch circuit 10.

The first amplifier circuit 4 does not operate normally when a driving voltage of 3 [V] is applied. The right-handed circularly polarized wave reception signal received by the right-handed circularly polarized wave receiving antenna 3 is supplied to the second amplifier circuit 5. Second amplifier circuit 5
Is composed of an LNA (Low Noise Amplifier), amplifies the right-handed circularly polarized reception signal supplied from the right-handed circularly polarized wave receiving antenna 3, and supplies the amplified signal to the input terminal Tb of the switch circuit 10.

The second amplifier circuit 4 includes a noise filter L
2. The DC voltage component of the output terminal Tout is supplied as a drive voltage via the resistor R. When the DC voltage component at the output terminal Tout is 3 [V], the resistance R
, A driving voltage of 2 [V] is supplied. The second amplifying circuit 5 receives the drive voltage of 2 [V], that is, the DC voltage component of the output terminal Tout becomes 3V.
It operates normally at the time of [V], amplifies the right-handed circularly polarized reception signal supplied from the right-handed circularly polarized wave receiving antenna 3, and
It is supplied to the input terminal Tb of the switch circuit 10.

The switch circuit 10 is the same as the conventional changeover switch 150, and is a signal passing type switch IC.
(Integrated Circuit). The switch circuit 10 outputs an output signal of the first amplifier circuit 130, that is, a left-hand circularly polarized wave reception signal, or an output signal of the second amplifier circuit 140, according to a control signal supplied to the control terminal Tcont.
That is, one of the right-hand circularly polarized reception signals is output. The output signal selected by the switch circuit 10 is supplied to the band pass filter 160.

The band-pass filter 6 includes a first amplifying circuit 4
A signal component in a required band is extracted from either the left-handed circularly polarized reception signal output from or the received right-handed circularly polarized reception signal output from the second amplifier circuit 5. The output signal of the bandpass filter 6 is supplied to an output amplifier circuit 7. The output amplifying circuit 7 amplifies the received signal selected by the band-pass filter 6 and supplies it to the output terminal Tout via the capacitor C1.

A DC bias voltage is applied to the output terminal Tout from the receiving unit described later. Output terminal Tout
Is applied to an output terminal T described later.
Out is connected to the receiving unit via a cable connected to out, and is supplied to the regulator 8 and the voltage detection circuit 9. A DC bias voltage of 2 [V] or 3 [V] is selectively applied to the output terminal Tout.

The regulator 8 is supplied with an output signal including an output signal and a DC bias voltage from an output terminal Tout. The regulator 8 includes an output signal supplied from an output terminal Tout and a center voltage 2 including a DC bias voltage.
The output voltage of [V] or 3 [V] is converted to a constant voltage of 2 [V]. The constant voltage of 2 [V] converted by the regulator 8 is supplied to the output amplifier circuit 7.

The constant voltage of 2 [V] supplied from the regulator 8 to the output amplifier circuit 7 is used as a drive voltage for the output amplifier circuit 7. The output amplifying circuit 7 includes a regulator 8
Stable operation with a constant voltage of 2 [V] supplied from the
The voltage detection circuit 9 supplies an output signal including an output signal and a DC bias voltage from the output terminal Tout to the detection terminal T1.
Supplied to The voltage detection circuit 9 includes, for example, a reset IC having an open collector output, detects the voltage supplied to the detection terminal T1, and outputs a high or low level control signal from the control terminal T2.

If the voltage supplied to the detection terminal T1 is about 2 [V], the voltage detection circuit 9 turns on the output transistor, short-circuits the control terminal T2, and sets the voltage supplied to the detection terminal T1 to If it is about 3 [V], the output transistor is turned off and the control terminal T2 is opened. The control terminal T2 of the voltage detection circuit 9 is connected to the control terminal T of the switch circuit 10.
Supplied to cont.

As described above, the switch circuit 10 has the input terminal Ta connected to the output terminal of the first amplifier circuit 4, the input terminal Tb connected to the output terminal of the second amplifier circuit 5, and the output terminal Tc connected to the bandpass filter 160. The input terminal Ta and the input terminal Tb are selectively connected to the output terminal Tc according to the level of the control terminal Tcont to which the control terminal T2 of the voltage detection circuit 9 is connected.

In the switch circuit 10, the control terminal Tcont is at the high level, that is, the voltage detection circuit 9 outputs the output terminal Tcont.
When 3 [V] is detected as the voltage of out and the output transistor is turned off and the control terminal T2 is opened, the input terminal Tb is connected to the output terminal Tc, and the control terminal Tcont is at a low level, that is, the voltage detection circuit 9 Output terminal Tou
When 2 [V] is detected as the voltage of t and the output transistor is turned on and the control terminal T2 is opened, the input terminal Ta is connected to the output terminal Tc.

FIG. 2 is a diagram for explaining the operation of one embodiment of the present invention. FIG. 2A shows a bias voltage of the terminal Tout, and FIG.
2 (B) is a control signal of the voltage detection circuit 9, FIG. 2 (C) is a state of the switch circuit 10, FIG. 2 (D) is an operation state of the first amplifier circuit 4, and FIG. 2 (E) is a second amplifier. The operating state of the circuit 5,
FIG. 2F shows the state of the signal output from the output terminal Tout.

First, at time t0, when the bias voltage applied from the receiving unit to the output terminal Tout is 2 [V], the control signal of the voltage detection circuit 9 is set to low level. When the control signal of the voltage detection circuit 9 is at a low level, the input terminal Ta of the switch circuit 10 is connected to the output terminal Tc. Therefore, the output signal of the first amplifier circuit 4 is supplied to the bandpass filter 6. At this time, as shown in FIG. 2 (D), the first amplifier circuit 4 has two output terminals Tout.
Since the signal component of the bias voltage [V] is removed by the noise filter L1 and supplied as drive power, the device operates normally.

On the other hand, the second amplifier circuit 5 has an output terminal T
Since the signal component is removed by the noise filter L2 from the bias voltage of 2 [V] out, the voltage is further dropped by the resistor R and supplied as a voltage of 2 [V] or less.
It does not operate normally as shown in FIG. Therefore,
Only the first amplifier circuit 4 operates normally, the signal is amplified, and the output signal is selected by the switch circuit 10, so that the left-handed circularly polarized reception signal received by the left-handed circularly polarized wave receiving antenna 2 is The signal is normally amplified by the first amplifier circuit 4 and supplied to the band-pass filter 6. For this reason, FIG.
As shown in the figure, a left-hand circularly polarized reception signal is output from the output terminal Tout.

Next, at time t1, when the bias voltage applied from the receiving unit to the output terminal Tout becomes 3 [V], the control signal of the voltage detection circuit 9 becomes high level.
When the control signal of the voltage detection circuit 9 is at a high level, the input terminal Tb of the switch circuit 10 is connected to the output terminal Tc. Therefore, the output signal of the second amplifier circuit 5 is supplied to the bandpass filter 6.

At this time, as shown in FIG. 2 (D), the bias voltage of 3 [V] at the output terminal Tout of the first amplifying circuit 4 has its signal component removed by the noise filter L1.
It is supplied as drive power. Since the first amplifier circuit 4 operates normally when the drive voltage is 2 [V], the first amplifier circuit 4 does not operate normally at this time. On the other hand, in the second amplifying circuit 5, the bias voltage of 3 [V] at the output terminal Tout is removed from the signal component by the noise filter L2, and further the voltage is dropped by the resistor R to a voltage of 2 [V]. Supplied. The second amplifier circuit 5 has a drive voltage of 2
Since normal operation is performed in [V], a normal operation state is established as shown in FIG.

Therefore, only the second amplifier circuit 4 operates normally, the signal is amplified, and the output signal is selected by the switch circuit 10, so that the signal is received by the right-handed circularly polarized wave receiving antenna 3. The left-hand circularly polarized reception signal is normally amplified by the second amplification circuit 5 and supplied to the band-pass filter 6. For this reason, as shown in FIG.
Outputs a right-handed circularly polarized wave reception signal.

As described above, according to this embodiment, the signal can be switched by controlling the bias voltage of the output terminal, and a dedicated control line for performing the switching is not required.
Wiring can be simplified. Next, a DAB broadcast receiving system using the antenna unit 1 of the present embodiment will be described.

FIG. 3 is a block diagram showing an application example of one embodiment of the present invention. The antenna unit 1 is connected to a receiving unit 20 for receiving a DAB broadcast. At this time,
The antenna unit 1 and the receiving unit 20 are connected only by the signal cable 30. The receiving unit 20
When receiving a left-handed circularly polarized wave reception signal from the left-handed circularly polarized wave reception antenna 2, the DC bias voltage of the signal cable 30 is set to 2 [V].

The receiving unit 20 sets the DC bias voltage of the signal cable 30 to 3 [V] when the level of the left-handed circularly polarized wave reception signal from the left-handed circularly polarized wave receiving antenna 2 is small, By switching the output signal of the antenna unit 1 to the right-handed circularly polarized reception signal from the right-handed circularly polarized reception antenna 3, a reception signal having a high reception level is selected and reception is performed in a good reception state. .

At this time, the connection between the antenna unit 1 and the receiving unit 20 is made by a signal cable 3 for supplying the received signal received by the antenna unit 1 to the receiving unit 20.
Since only 0 DC bias voltage needs to be switched to 2 [V] or 3 [V], a dedicated signal line for antenna switching becomes unnecessary. In the present embodiment, a signal switching circuit used for selecting a reception signal received on one reception surface from a planar antenna having a plurality of reception surfaces for receiving radio waves in different circular polarization directions in the antenna unit is described. Although the description has been made, the present invention is not limited to this. For example, switching of a received signal at an antenna element having a different receiving direction of a diversity antenna can be applied.

Further, the present invention is not limited to the antenna,
In short, it can be applied as a circuit that switches between two input signals. Further, the input signal is not limited to two systems, but can be applied to switching to a plurality of input signals by enabling a plurality of voltages to be detected by a voltage detection circuit. In this embodiment, the bias voltage is set to 2 [V] and 3 [V].
Although the input signal is switched by switching with [V], the voltage is not limited to 2 [V] and 3 [V], and it is only necessary to use different voltages that can be detected.

[0038]

As described above, according to the first aspect of the present invention, the voltage of the output terminal is detected by the voltage detection means, and the voltage is detected between the plurality of input terminals and the output terminal by the switching means. The signal can be switched by controlling the bias voltage of the output terminal by selectively connecting one of the plurality of input terminals to the output terminal according to the detection result of the voltage of the output terminal by the means. This makes it possible to eliminate the need for a dedicated control line for switching, thereby simplifying the wiring.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of one embodiment of the present invention.

FIG. 3 is a block diagram of an application example of an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a conventional example.

FIG. 5 is a block diagram illustrating an example of a conventional antenna unit.

FIG. 6 is a diagram illustrating an operation of an example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna unit 2 Left-handed circularly polarized wave receiving antenna 3 Right-handed circularly polarized wave receiving antenna 4 First amplifier circuit 5 Second amplifier circuit 6 Bandpass filter 7 Amplifier circuit 8 Regulator 9 Voltage detection circuit 10 Switch circuit 20 Reception Unit 30 Signal cable C1 Capacitor L1, L2 Noise filter R Resistance Tout Output terminal

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[Procedure amendment]

[Submission date] September 1, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

[0015]

FIG. 1 is a block diagram showing an embodiment of the present invention. In this embodiment, the signal switching circuit is DAB
(Digital Audio Broadcasting) An embodiment provided in the receiving antenna unit 1 will be described. The antenna unit 1 includes a left-handed circularly polarized wave receiving antenna 2 that receives left-handed circularly polarized waves in radio waves, a right-handed circularly polarized wave receiving antenna 3 that receives right-handed circularly polarized waves in radio waves, and a left-handed circularly polarized wave reception. Amplifying circuit 4 for amplifying the left-handed circularly polarized reception signal received by the antenna 2 for reception, and the second amplification for amplifying the right-handed circularly polarized reception signal received by the right-hand circularly polarized reception antenna 3 A circuit 5, a band-pass filter 6 for passing only necessary components from a received signal amplified by the first amplifier circuit 4 or the second amplifier circuit 5, an amplifier circuit 7 for amplifying a signal passing through the band-pass filter 6,
A capacitor C1 provided between the amplifier circuit 7 and the output terminal Tout for removing a DC component; a regulator circuit 8 for converting a bias voltage supplied to the output terminal Tout to a predetermined voltage; a bias voltage supplied to the output terminal Tout Is provided between the band-pass filter 6 and the voltage detection circuit 9 for generating a control signal of a high or low level in accordance with the bias voltage, and the band-pass filter 6. A changeover switch 10 for selectively outputting the output of the first amplifier circuit 4 or the output of the second amplifier circuit 5 to the band-pass filter 6 in response to a control signal of the circuit 9, and an output terminal Tout
Voltage noise is removed from the first noise filter L1 supplied as the drive voltage of the first amplifying circuit 4, the second noise filter L2 to remove noise from the voltage of the output terminal Tout, a second noise filter The voltage at the output terminal Tout and the resistance R supplied to the second amplifier circuit 4 as a driving voltage by dropping the voltage from which the noise has been removed by the L2 are output.
The regulator 8, the voltage detection circuit 9, the first and second
To be supplied to the first and second noise filters L1 and L2
L3. The left-handed circularly polarized wave receiving antenna 2 and the right-handed circularly polarized wave receiving antenna 3 are, for example, a conductive thin film for the left-handed circularly polarized wave receiving antenna and a right-handed circularly polarized wave receiving antenna on the same insulating substrate. And the conductive thin films are separately formed in an insulated state. The conductive thin film for the left circularly polarized wave receiving antenna is formed so as to easily receive the left circularly polarized wave, and the conductive thin film for the right circularly polarized wave receiving antenna is formed so as to easily receive the right circularly polarized wave. Formed.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

The left-handed circularly polarized wave reception signal received by the left-handed circularly polarized wave receiving antenna 2 is supplied to a first amplifier circuit 4. The first amplifier circuit 4 includes an LNA (Low Noise Amplifier).
r), amplifies the left-hand circularly polarized reception signal supplied from the left-hand circularly polarized wave receiving antenna 2 and supplies the amplified signal to the band-pass filter 6. The first amplifier circuit 4 has an output terminal T
The drive voltage is supplied from out through the noise filters L1 and L3 . The first amplifier circuit 4 has a predetermined driving voltage (2
When [V]) is applied, it operates normally,
The right-handed circularly polarized reception signal supplied from the left-handed circularly polarized wave receiving antenna 2 is amplified and supplied to the terminal Ta of the switch circuit 10.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

The second amplifier circuit 5 includes a noise filter L
2 , a DC voltage component of the output terminal Tout is supplied as a drive voltage via a resistor R and a resistor R. When the DC voltage component at the output terminal Tout is 3 [V], a driving voltage of 2 [V] is supplied to the second amplifier circuit 5 due to the voltage drop of the resistor R. The second amplifier circuit 5 has a drive voltage of 2 [V]
Is supplied, that is, when the DC voltage component at the output terminal Tout is 3 [V], the normal operation is performed, and the right-hand circularly polarized wave reception signal supplied from the right-handed circularly polarized wave reception antenna 3 is received. The signal is amplified and supplied to the input terminal Tb of the switch circuit 10.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

[0022] to the regulator 8, from the output terminal Tout
DC bias voltage is subjected fed. Regulator 8, straight of 2 Ru supplied [V] or 3 [V] from the output terminal Tout
The current bias voltage is converted to a constant voltage of 2 [V]. The constant voltage of 2 [V] converted by the regulator 8 is supplied to the output amplifier circuit 7.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0023

[Correction method] Change

[Correction contents]

The constant voltage of 2 [V] supplied from the regulator 8 to the output amplifier circuit 7 is used as a drive voltage for the output amplifier circuit 7. The output amplifying circuit 7 includes a regulator 8
Stable operation with a constant voltage of 2 [V] supplied from the
The voltage detection circuit 9 has a DC bus from the output terminal Tout.
The bias voltage is supplied to the detection terminal T1 . The voltage detection circuit 9 includes, for example, a reset IC having an open collector output, detects the voltage supplied to the detection terminal T1, and outputs a high or low level control signal from the control terminal T2.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

When the DC bias voltage supplied to the detection terminal T1 is about 2 [V], the voltage detection circuit 9 turns on the output transistor, short-circuits the control terminal T2, and is supplied to the detection terminal T1. When the voltage is about 3 [V], the output transistor is turned off and the control terminal T2 is opened. The control terminal T2 of the voltage detection circuit 9 is connected to the switch circuit 1
0 is supplied to the control terminal Tcont.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

In the switch circuit 10, the control terminal Tcont is at the high level, that is, the voltage detection circuit 9 outputs the output terminal Tcont.
out DC bias voltage 3 [V] is detected as the, the output transistor is turned off by the control terminal T2 in an open state, connects the input terminal Tb to the output terminal Tc, the control terminal Tcont is low, i.e., the voltage detection When the circuit 9 detects 2 V as the DC bias voltage of the output terminal Tout, and turns on the output transistor and opens the control terminal T2, the input terminal Ta is connected to the output terminal Tc.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction contents]

First, at time t0, when the bias voltage applied from the receiving unit to the output terminal Tout is 2 [V], the control signal of the voltage detection circuit 9 is set to low level. When the control signal of the voltage detection circuit 9 is at a low level, the input terminal Ta of the switch circuit 10 is connected to the output terminal Tc. Therefore, the output signal of the first amplifier circuit 4 is supplied to the bandpass filter 6. At this time, as shown in FIG. 2 (D), the first amplifier circuit 4 has two output terminals Tout.
Bias voltage [V] noises are removed by the noise filter L1, L3, since it is supplied as a driving power source,
Works fine.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

On the other hand, the second amplifier circuit 5 has an output terminal T
out 2V is applied to the noise filter L2 ,
Since noise is removed by L3, the voltage is further dropped by the resistor R, and supplied at a voltage of 2 [V] or less, the circuit does not operate normally as shown in FIG. Therefore, only the first amplifier circuit 4 operates normally, the signal is amplified, and the output signal is selected by the switch circuit 10, so that the left-handed circularly polarized wave reception signal received by the left-handed circularly polarized wave receiving antenna 2 is received. The signal is normally amplified by the first amplifier circuit 4,
The signal is supplied to the band pass filter 6. Therefore, FIG.
As shown in (F), a left-hand circularly polarized reception signal is output from the output terminal Tout.

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0030

[Correction method] Change

[Correction contents]

At this time, as shown in FIG. 2 (D), the bias voltage of 3 [V] of the output terminal Tout is removed by the noise filters L1 and L3 in the first amplifier circuit 4, and the first amplifier circuit 4 is used as a drive power supply. Supplied. The first amplifier circuit 4
Since the normal operation is performed when the drive voltage is 2 [V], the first amplifier circuit 4 does not operate normally at this time. On the other hand, the bias voltage of 3 [V] at the output terminal Tout is removed by the noise filters L2 and L3 in the second amplifier circuit 5, the voltage is dropped by the resistor R, and the voltage of 2 [V] is reduced. Supplied and supplied. Since the second amplifier circuit 5 operates normally when the drive voltage is 2 [V], it enters a normal operation state as shown in FIG.

[Procedure amendment 11]

[Document name to be amended] Statement

[Correction target item name] Explanation of sign

[Correction method] Change

[Correction contents]

[Description of Signs] 1 Antenna unit 2 Left circularly polarized wave receiving antenna 3 Right circularly polarized wave receiving antenna 4 First amplifier circuit 5 Second amplifier circuit 6 Bandpass filter 7 Amplifier circuit 8 Regulator 9 Voltage detection circuit Reference Signs List 10 switch circuit 20 receiving unit 30 signal cable C1 capacitor L1, L2 , L3 noise filter R resistor Tout output terminal

[Procedure amendment 12]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

Claims (1)

[Claims] 1. A signal switching circuit for selecting one input signal from input signals input to a plurality of input terminals and outputting the selected signal from an output terminal, wherein: a voltage detection means for detecting a voltage of the output terminal; Connected between an input terminal and the output terminal,
Switching means for selectively connecting any one of the plurality of input terminals to the output terminal in accordance with a detection result of the voltage of the output terminal by the voltage detection means. .