JP2002290268A - Antenna changeover circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna changeover circuit 10 of one kind that can effectively select and carry out the changeover of reception of a high frequency reception signal in two frequency bands. SOLUTION: The antenna changeover circuit 10 includes a transmitter side connection circuit 1 that is connected between an antenna 3 and a transmission section 5, a receiver side connection circuit 2 that is connected between the antenna 3 and a reception section 6, and turns on/off the transmitter side or receiver side connection circuits 1, 2 to switch the connection to the antenna 3 and the transmission section 5 or the reception section 6. The transmitter side connection circuit 1 includes a series circuit comprising a 1st diode 11 connected in series with a signal path and a 1st inductor 13 and a 1st capacitor 12 connected in parallel with the 1st diode 11 and 1st variable power supplies 17 , 18 that select and output two kinds of voltages. The receiver side connection circuit 2 includes a 2nd inductor 21 connected in series with the signal path, 2nd variable power supplies 27 , 28 that select and output two kinds of voltages, a parallel circuit comprising a 2nd capacitor 22 and a 1st resistor 25 connected between the signal path and ground, and a parallel circuit comprising a 2nd diode 23 and a 2nd resistor 26 connected between the signal path and the 2nd variable power supplies 27 , 28 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna switching circuit, and more particularly, to switching between a transmission / reception antenna and a transmission unit or a reception unit, a transmission signal in one frequency band and a reception signal in two frequency bands. And an antenna switching circuit adapted to cope with the above.

[0002]

2. Description of the Related Art Conventionally, in a time-division transmission / reception type telephone such as a portable telephone or a cordless telephone, a connection between a transmission / reception antenna and a transmission unit (transmission unit) and a connection between a transmission / reception antenna and a reception unit (reception unit) are switched. It has an antenna switching circuit. This antenna switching circuit generally includes a transmission-side connection circuit including a diode disposed between the transmission / reception antenna and the transmission unit, and a reception-side connection circuit including a diode disposed between the transmission / reception antenna and the reception unit. In response to transmission or reception, the diode on the transmission side connection circuit side and the diode on the reception side connection circuit side are turned on and off by the switching voltage, and the connection between the transmission and reception antenna and the transmission unit or the transmission and reception antenna and the reception unit The connection is switched.

FIG. 8 is a circuit diagram showing an example of the configuration of a known antenna switching circuit, and also shows the antenna switching circuit and its peripheral circuits.

As shown in FIG. 8, an antenna switching circuit 80 includes a transmission side connection circuit 81 and a reception side connection circuit 82. In addition, a transmission / reception antenna 83, an antenna shared circuit 44, and a transmission section (TX) 85 and the receiving unit (R
X) 86, a signal input terminal 87, and a signal output terminal 88. In this case, the transmission-side connection circuit 81
A first diode 81 ₁ , a first capacitor 81 ₂ , a first inductor 81 ₃ , a second capacitor 81 ₄ ,
Inductor 81 ₅ , isolation resistor 81 ₆ , DC power supply 81
It comprises a _7, a changeover switch 81 _8, an input terminal 81 _9, and an output terminal 81 _10. The receiving-side connection circuit 82 includes a third inductor 82 ₁ , a third capacitor 82 ₂ , a second diode 82 ₃ , a fourth capacitor 82 _4, and an input terminal 82.
It includes a ₅ and an output 82 _6. The antenna shared circuit 84 includes a fifth capacitor 84 ₁ and a sixth capacitor 8.
4 is equipped with a ₂ and.

[0005] The transmission side connection circuit 81 is connected to the input terminal 8.
₁₉ is connected to the output terminal of the transmitting unit 85, and the output terminal 81 ₁₀ is connected to the transmission input terminal of the antenna sharing circuit 84. The receiving-side connection circuit 82 has an input terminal 82 ₅ connected to the antenna sharing circuit 8.
Connected to the reception input of 4, output 82 ₆ receiving unit 86
Is connected to the input terminal of The antenna shared circuit 84 has an antenna connection end connected to the transmission / reception antenna 83. The transmitting unit 85 has an input terminal connected to the signal input terminal 87, and the receiving unit 86 has an output terminal connected to the signal output terminal 88. In the transmission-side connection circuit 81, the respective components 81 _{1 to} 81 ₁₀ are interconnected as shown in FIG. In the receiving side connection circuit 82, interconnected as each of the components 82 ₁ to 82 ₆ shown in FIG. 8, the antenna sharing circuit 84, as each of the components 84 ₁ and 84 ₂ shown in FIG. 8 It is connected to the.

[0006] Next, FIG. 9 is a characteristic showing a signal transmission characteristic and the signal reflection characteristics of the high frequency transmission signal of the first diode 81 ₁ and the second diode 82 _3-on of the transmitter-side connection circuit 81 in the antenna switching circuit 80 FIG.
Receiving-side connection circuit 82 when first diode 81 ₁ and second diode 82 ₃ in antenna switching circuit 80 are off
FIG. 4 is a characteristic diagram showing signal transmission characteristics and signal reflection characteristics of the high-frequency reception signal of FIG.

In FIGS. 9 and 10, the horizontal axis represents the frequency expressed in GHz, and the vertical axis represents the attenuation expressed in dB. The solid line indicates signal transmission characteristics, and the dotted line indicates signal reflection characteristics.

[0008] The antenna switching circuit 10 having the above-described configuration includes:
In general, it operates as follows.

[0009] Now, at the time of transmission timing of the transmission portion 85, the switching signal supplied from the control unit (not shown), the changeover switch 81 ₈ is switched connections moving contact state shown in the drawing, i.e. to the DC power supply 81 ₇ side You. In this state, the DC voltage of the DC power supply 81 ₇ is supplied to the switched switch 81 ₈ , the isolation resistor 81 ₆ , the second inductor 81 ₅ , and the first diode 81 ₁ , and then the third inductor 82 ₁ , It flows to ground through the second diode 82 ₃ , whereby the first diode 81 ₁
And to turn on the second diode 82 _3. At this time, the transmission signal supplied to the signal input terminal 87 is frequency-converted by the transmission unit 85 to a transmission frequency in a predetermined frequency band, in this case, a 1.4 GHz band, and is power-amplified to a predetermined transmission level. As the transmission side connection circuit 81
It is input to the input terminal 81 _9. In the transmission-side connection circuit 81, the input high-frequency transmission signal is supplied to the second capacitor 8
After passing through the 1 _4, supplied from the output terminal 81 ₁₀ through the first diode 81 ₁ which is turned to the antenna sharing circuit 84. In the antenna sharing circuit 84, the high frequency transmission signal supplied to the transmit input terminal is supplied from the antenna connection terminal through a sixth capacitor 84 ₂ to the transmission and reception antenna 83, it is transmitted as a radio wave in the transmitting and receiving antenna 83. In this case, the high-frequency transmission signal supplied to the antenna sharing circuit 84 is transmitted through the reception input terminal to the reception-side connection circuit 82.
Although also to be transmitted, the second diode 82 ₃ because it is on, the flow to the ground point through the second diode 82 _3, and it is not transmitted to the receiving unit 86 side.
The same applies when a radio wave arrives at the transmission / reception antenna 83 and a high-frequency reception signal formed by the arrival radio wave is transmitted to the reception side connection circuit 82 through the reception input end.

At this time, as shown by the solid line in FIG. 9, the signal transmission characteristics of the high-frequency transmission signal in the transmission-side connection circuit 81 have almost no signal attenuation including around the 1.4 GHz frequency band. The signal reflection characteristic of the high-frequency transmission signal in the transmission-side connection circuit 81 has a characteristic in which the amount of attenuation sharply increases near the frequency band of 1.4 GHz as shown by the dotted line in FIG.

On the other hand, when the reception timing of the
Then, the switching signal is supplied by the control unit,
Itch 81₈Indicates that the movable contact is in the opposite state to that shown,
That is, it is switched to the ground point side. In this state,
Changed changeover switch 81 ₈DC power supply 81₇Or
When the supply of the DC voltage is cut off, the first diode 81₁Passing
And the second diode 82_ThreeSince there is no current passing through
1 diode 81₁And the second diode 82_ThreeTurn
Turn off. At this time, a signal radio wave is
In this case, when the radio wave of the frequency of the 1.4 GHz band arrives,
The high-frequency reception signal formed by the
The formed high-frequency reception signal is formed in the tenor shared circuit 84.
The signal from the receiving input terminal to the input terminal 82 of the receiving side connection circuit 82
_FiveSupplied to In the receiving side connection circuit 82, the input terminal
82_FiveSupplied to the second diode 8
2_ThreeIs turned off, the third inductor 82₁When
Fourth capacitor 82_FourThrough the output end 82₆Transmitted to
Output terminal 82₆Is supplied to the receiving unit 86 from Receiver
At 86, the high frequency received signal is amplified to a predetermined level.
And demodulated, converted to a baseband signal,
The obtained baseband signal is supplied to a signal output terminal 88.
It is. In this case, the height formed in the antenna shared circuit 84 is
The frequency reception signal is transmitted to the transmission side connection circuit 8 through the transmission input end.
1, the first diode 81₁Is off
Output in the frequency band of the high-frequency reception signal
End 81_ThreeInternal impedance of the transmission side connection circuit 81 from the
Signal is a very large value,
Does not flow into the transmission-side connection circuit 81,
The transmission signal does not adversely affect the transmission side connection circuit 81.
No.

At this time, the signal transmission characteristics of the high-frequency reception signal in the reception-side connection circuit 82 have almost no signal attenuation including around the 1.4 GHz frequency band, as shown by the solid line in FIG. As shown by the dotted line in FIG. 10, the signal reflection characteristic of the high-frequency reception signal in the reception-side connection circuit 82 is such that the attenuation increases sharply near the frequency band of 1.4 GHz.

[0013] Thus, the antenna switching circuit 80 switches the changeover switch 81 ₈ by a switching signal supplied from the control unit at the time of transmission timing and reception timing,
By turning on both the first diode 81 ₁ and the second diode 82 ₃ or turning off both, the transmission connection circuit 81 is turned on, the reception connection circuit 82 is turned off, and the transmission / reception antenna 83 is connected to the transmission unit 85. Or the transmission-side connection circuit 81 is turned off, the reception-side connection circuit 82 is turned on, and the transmission / reception antenna 83 can be connected to the reception unit 86.

[0014]

The known antenna switching circuit 80 has a transmitting / receiving antenna 83 at the time of transmission.
Can be connected to the transmitting unit 85, and the transmitting / receiving antenna 83 can be connected to the receiving unit 86 at the time of reception. However, the setting is such that the frequency band of the high-frequency reception signal can correspond to a predetermined frequency band. Therefore, the antenna switching circuit 80 cannot be used as it is for another frequency band of the high-frequency reception signal, and can be used for another frequency band of the high-frequency reception signal. To do this, the antenna switching circuit 8 must be
The design of the antenna switching circuit 80 had to be changed, and the applicable range of each antenna switching circuit 80 was narrow.

The present invention has been made in view of such a technical background, and an object of the present invention is to effectively switch the reception of high frequency reception signals in two frequency bands by using one type of antenna switching circuit. An object of the present invention is to provide an antenna switching circuit capable of performing a selective execution.

[0016]

In order to achieve the above object, an antenna switching circuit according to the present invention comprises a transmission-side connection circuit connected between an antenna and a transmission unit, and a transmission-side connection circuit connected between the antenna and the reception unit. And a receiving side connection circuit to be connected.The transmission side connection circuit or the reception side connection circuit is alternately turned on and off to switch the connection between the antenna and the transmission unit or the reception unit. A receiving side connection circuit including a first diode connected in series to a signal path, a series circuit of a first inductor and a first capacitor connected in parallel to the first diode, and a first variable power supply for selectively outputting two types of voltages; Is a second inductor connected in series to the reception signal path,
A second variable power supply for selectively outputting two types of voltages, a parallel circuit of a second capacitor and a first resistor connected between the reception signal path and the reference voltage point, and a connection between the reception signal path and the second variable power supply. Means including a parallel circuit of the second diode and the second resistor.

According to the above means, the first variable power supply and the second variable power supply for supplying the operating voltage to the first diode and the second diode are each configured to selectively output two kinds of voltages. The connection state (switching connection to the transmission side) between the antenna and the transmission unit by the transmission side connection circuit or the disconnection state (switching connection to the reception side) is set by selecting two types of voltages output from the variable power supply. Further, when the transmission side connection circuit is set to the disconnected state (switch connection to the reception side), the operation state of the reception side connection circuit is switched by selecting two types of voltages output from the second variable power supply, Switching of the frequency band of the high-frequency reception signal (first frequency band, for example, 1.4 GHz band, or second frequency band, for example, 1.5 GHz band)
GHz band switching) setting, it is possible to selectively switch between high frequency reception signals of two frequency bands in the receiving side connection circuit, and to use the second variable power supply of the second variable power supply without using another antenna switching circuit. The kind of voltage is only the selected output,
Switching between high-frequency reception signals in two frequency bands can be performed, and an antenna switching circuit with an expanded application range can be obtained.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of an antenna switching circuit according to the present invention, which also shows a peripheral circuit portion together with the antenna switching circuit, and a transmission signal of 1.4 GHz. The frequency of the band is set to a frequency of the 1.4 GHz band or the 1.5 GHz band as the reception signal.

FIG. 1 shows a first embodiment.
The antenna switching circuit 10 includes a transmission-side connection circuit 1 and
The receiving side connection circuit 2, the transmission / reception antenna 3, and the antenna
Circuit 4, transmitting section (TX) 5, receiving section (RX) 6
And a signal input terminal 7 and a signal output terminal 8.
In this case, the transmission-side connection circuit 1 includes the first diode 1
₁And the first inductor 1_TwoAnd the first capacitor 1_ThreeWhen,
Second capacitor 1_FourAnd the second inductor 1_FiveAnd the buffer resistor
Anti-1₆And the first DC power supply 1₇And the first changeover switch 1 ₈
And input terminal 1₉And output 1_TenIs provided. Receiver connection times
The path 2 is the third inductor 2₁And the third capacitor 2
_TwoAnd the second diode 2_ThreeAnd the fourth capacitor 2_FourWhen,
1st resistor 2_FiveAnd the second resistor 2₆And the second DC power supply 2
₇And the second changeover switch 2₈And input terminal 2₉And the output end
2_TenIs provided. In addition, the antenna common circuit 4 is
Densa 4₁And the sixth capacitor 4_TwoIt has. here
Then, the first DC power supply 1₇And the second DC power supply 2₇Is 3V direct
A first DC power supply 1 ₇And the first switch
Switch 1₈Constitutes a first variable power supply and a second DC power supply 2
₇And the second switch 2₈Constitutes the second variable power supply
You. Also, the first resistor 2_FiveAnd the second resistor 2₆Means that the resistance value
Equally, for example, having a resistance value of 1 KΩ.

The transmission-side connection circuit 1 is connected to the input terminal 1 ₉
There is connected to the output end of the transmission unit 5, the output terminal 1 ₁₀ is connected to the transmit input terminal of the antenna duplexer circuit 4. Receiver-side connection circuit 2, input 2 ₉ is connected to the reception input terminal of the antenna duplexer circuit 4, the output terminal 2 ₁₀ is connected to an input end of the receiver 6. The antenna shared circuit 4 has an antenna connection end connected to the transmission / reception antenna 3. The transmitting unit 5 has an input terminal connected to the signal input terminal 7, and the receiving unit 6 has an output terminal connected to the signal output terminal 8.

In the transmitting side connection circuit 1, the first diode
Do 1₁Is the output terminal 1_TenConnected to the anode
Is the second capacitor 1_FourAnd the second inductor 1_FiveAt each end of
Connected. First capacitor 1_TwoIs one output terminal_Ten
And the other end is connected to the first inductor 1_ThreeConnected to one end of
It is. 1st inductor 1_ThreeThe other end is the first diode 1
₁Connected to the anode of the second capacitor 1_FourIs the other end
Is the input terminal 1₉Connected to. Second inductor 1_FiveIs the other
End is isolation resistor 1₆Is connected to one end of the₆Is
The other end is the first switch 1₈Is connected to the movable contact.
1st DC power supply 1 ₇Is one end of the first switch 1₈One
And the other end is connected to a ground point.
1st changeover switch 1₈Indicates that the other fixed contact is
Continued. In the receiving side connection circuit 2, the third inductor
2₁Is one input terminal₉The other end is connected to the third
Densa 2_TwoAnd the fourth capacitor 2_FourAnd one end of the first resistor
2 _FiveAnd the second resistor 2₆And one end of the second diode 2_Threeof
Each is connected to the anode. Third capacitor 2
_TwoHas the other end connected to a ground point. Second diode 2_Three
Means that the cathode is the second resistor 2₆Other end and second switch
2₈Is connected to the movable contact. Fourth capacitor 2_FourIs
The other end is output end 2_TenConnected to. 1st resistor 2_FiveIs the other end
Is connected to the ground point. Second DC power supply 2₇Has one end
2 changeover switch 2 ₈Connected to one of the fixed contacts and the other
Is connected to the ground point. Second changeover switch 2₈Is the other
Are connected to the ground point. Antenna shared circuit 4
In the fifth capacitor 4₁Is one end of the 6th condensation
Sa4_TwoTo the transmission input end and the reception input end respectively.
And the other end is connected to a ground point. 6th capacitor
4_TwoHas the other end connected to the antenna connection end.

Here, FIG. 2 shows characteristics showing signal transmission characteristics and signal reflection characteristics of the high-frequency reception signal of the reception-side connection circuit 2 when the frequency band of the reception signal is set to 1.4 GHz in the antenna switching circuit 10. FIG. 3 is a diagram showing an example in which the frequency band of a received signal is 1.5 G in the antenna switching circuit 10.
FIG. 4 is a characteristic diagram showing a signal transmission characteristic and a signal reflection characteristic of a high-frequency reception signal of the reception-side connection circuit 2 when the frequency is set to Hz. FIG. 4 shows a first resistance ₂₅ and a second resistance in the antenna switching circuit 10. ₂₆ is a characteristic diagram showing a relationship between the resistance value of ₂₆ and the transmission loss of the high-frequency reception signal of the reception-side connection circuit 2. FIG.

In FIGS. 2 and 3, the horizontal axis represents the frequency expressed in GHz, and the vertical axis represents the signal attenuation (signal transmission characteristic) expressed in dB. The solid line indicates signal transmission characteristics, and the dotted line indicates signal reflection characteristics. FIG.
, The horizontal axis is the resistance value in ohms (Ω),
The vertical axis is the signal transmission loss expressed in dB.

The antenna switching circuit 10 according to the first embodiment having the above configuration operates as follows.

First, the frequency band of the high frequency transmission signal is 1.
The operation when the frequency band is 4 GHz and the frequency band of the high-frequency reception signal is also the same frequency band of 1.4 GHz will be described. In this embodiment, the first DC power supply 1
DC voltage and the DC voltage of the second DC power supply 2 _{7 7} are both set to 3V.

[0027] Now, at the time of transmission timing of the transmission unit 5, the switching signal supplied from the control unit, not shown, the first changeover switch 1 ₈ movable contact is in the state shown, namely a first direct-current power supply 1 ₇ side Switched to the second
Selector switch 2 ₈ movable contact is in the state shown, i.e. is switched connected to ground side. In this state, the DC voltage of the first DC power source 1 ₇ (3V), the first changeover switch 1 ₈ that is switched, isolation resistors 1 _6, second inductor 1 ₅ is supplied to the first diode 1 _1, then , the third inductor 2 _1, flows to the ground point through the second diode 2 _3, second change-over switch 2 ₈ that is switched, thereby turning on the first diode 1 ₁ and the second diode 2 _3.
At this time, the transmission signal supplied to the signal input terminal 7 is frequency-converted by the transmission unit 5 to a transmission frequency in a predetermined frequency band, in this case, a 1.4 GHz band, and is power-amplified to a predetermined transmission level. The signal is input to the input terminal ₁₉ of the transmission-side connection circuit 1 as a transmission signal. In the transmission-side connection circuit 1, the input high-frequency transmission signal is transmitted to the second capacitor 1
After passing through the _4, supplied from the output terminal 1 ₁₀ to the antenna sharing circuit 4 through the first diode 1 ₁ ON. In the antenna sharing circuit 4, a high frequency transmission signal supplied to the transmit input terminal is supplied from the antenna connection terminal through a sixth capacitor 4 ₂ to the transmission and reception antenna 3 is transmitted as a radio wave in the transmission and reception antenna 3. In this case, since the high frequency transmission signal supplied to the antenna sharing circuit 4 is also transmitted to the receiving side connection circuit 2 via the receiving input terminal, a second diode 2 ₃ is turned on, the second diode 2 _The impedance reaching the ground point through ₃ becomes almost zero, and is not transmitted to the receiving unit 6 side.
The same applies when a radio wave arrives at the transmission / reception antenna 3 and a high-frequency reception signal formed by the arrival radio wave is transmitted to the reception-side connection circuit 2 through the reception input end.

At this point, the transmission characteristics and reflection characteristics of the high-frequency transmission signal in the transmission-side connection circuit 1 are almost the same as the signal transmission characteristics and signal reflection characteristics shown in FIG. And almost no signal attenuation occurs before and after the frequency band of 1.4 GHz.
As shown by the dotted line in FIG. 9, the signal reflection characteristic of the high-frequency transmission signal in FIG. 9 has a characteristic in which the amount of attenuation sharply increases near the frequency band of 1.4 GHz.

On the other hand, at the time of the reception timing of the receiving section 6
And the first switching by the switching signal supplied from the control unit.
Switch 1₈Indicates that the movable contact is in the opposite state to that shown,
That is, the second changeover switch 2 is switched and connected to the ground point side.₈Is
The movable contact is still in the state shown in the figure,
The connection is switched. When this happens
The first change-over switch 1₈By the first
Power supply 1₇DC voltage (3V) supplied from the
First diode 1₁And the second diode 2_ThreeStraight through
Since there is no current flow, the first diode 1₁And the second da
Iod 2_ThreeTurns off. And the second Daio
Mode 2_ThreeIndicates that the DC voltage at both ends is
Since it is in an ias state, its junction capacitance value is relatively large,
For example, it is 2 pF. At this time,
3 is a signal radio wave, in this case a radio wave of a frequency in the 1.4 GHz band.
Arrives, the high frequency wave formed by the incoming radio wave
The received signal is formed in the antenna shared circuit 4 and formed.
The high frequency reception signal is transmitted from the reception input terminal to the reception side connection circuit 2.
Input terminal 2_FiveSupplied to In the receiving side connection circuit 2,
Input terminal 2_FiveIs supplied to the third inductor
TA2₁And the third capacitor 2_TwoContent
Quantity and second diode 2_ThreeAnd the total capacity of the
Determined series resonance circuit and fourth capacitor 2_FourThrough
Output terminal 2 ₆And output 2₆To receiver 6
Supplied. In the receiving unit 6, the high frequency received signal is
While being amplified to a constant level, it is demodulated and
And the resulting baseband signal is converted to a signal
It is supplied to the force terminal 8. In this case, the antenna shared circuit 4
The high-frequency reception signal formed at the
Of the first diode 1₁
Is turned off, so that the
Output terminal 1_ThreeInternal impedance of the transmission side connection circuit 1 from the
-The dance has a very large value,
The communication signal does not flow into the transmission side connection circuit 1 and the high frequency
The wave reception signal has no adverse effect on the transmission side connection circuit 1.
Absent.

At this time, the signal transmission characteristics and the signal reflection characteristics of the high-frequency reception signal in the reception-side connection circuit 2 exhibit the characteristics shown by the solid line and the dotted line in FIG. 2, and the signal transmission characteristics are 1.4 GHz. There is almost no signal attenuation including before and after the frequency band, and the signal reflection characteristic is 1.4G.
The characteristic is sharply increased near the frequency band of Hz.

Next, the frequency band of the high-frequency transmission signal is 1.4.
The operation when the frequency band of the high frequency reception signal is 1.5 GHz, which is a different frequency band from the high frequency reception signal, will be described.

First, the first time at the transmission timing of the transmission unit 5
Overall operation accompanying the switching state and the switching of the movable contact of the changeover switch 1 ₈ and the second changeover switch 2 _8, the first movable contact of the changeover switch 1 ₈ and the second changeover switch 2 ₈ at the time of transmission timing already mentioned Is exactly the same as the switching state and the entire operation accompanying the switching, and the obtained operation is also exactly the same. Therefore, further description of the operation at the transmission timing will be omitted.

On the other hand, the reception timing of the receiver 6
At the time, by the switching signal supplied from the control unit,
1st changeover switch 1₈Indicates that the movable contact is in the opposite state as shown
State, that is, connected to the ground point side, and the second switch
Chi 2₈Indicates that the movable contact is in a state opposite to the state shown in FIG.
Second DC power supply 2₇Side is switched and connected. this
The first changeover switch 1 that has been switched when the state₈
1st DC power supply 1₇Supply of DC voltage (3V)
Supply is cut off and the first diode 1 based on its DC voltage₁
And the second diode 2_ThreeThe current flowing through the
1 diode 1 ₁And the second diode 2_ThreeTurns off
become. And the second diode 2_ThreeIs connected to the cathode
2 DC power supply 2₇DC voltage (3V) is applied to the anode
DC power supply 2₇DC voltage of the first resistor 2_FiveAnd the second resistor 2₆
Voltage (1.5 V) is applied,
Second diode 2_ThreeReverse bias voltage (−1.5
V) is applied, the junction capacitance value is zero.
Low bias, for example, about 0.5 pF
It has become. At this time, a signal
Wave, in this case, a radio wave with a frequency of 1.5 GHz band arrives
And the high-frequency reception signal formed by the incoming radio wave
High-frequency reception formed in the antenna shared circuit 4
The signal is input from the receiving input terminal to the input terminal 2 of the receiving side connection circuit 2._Five
Supplied to In the receiving side connection circuit 2, the input terminal 2_Five
Is supplied to the third inductor 2₁No
The conductance value and the third capacitor 2_TwoCapacity and second
Diode 2_ThreeSeries determined by the total capacitance with the junction capacitance of
Resonant circuit and fourth capacitor 2_FourAnd through the output end
2₆And output 2₆Is supplied to the receiving unit 6 from
You. In the receiving unit 6, the high-frequency reception signal has a predetermined level.
And demodulated to a baseband signal.
The converted and obtained baseband signal is supplied to a signal output terminal 8.
Supplied to Also in this case, the antenna shared circuit
The high-frequency reception signal formed at 4 is transmitted through the transmission input end.
The first diode 1 is also supplied to the transmission side connection circuit 1.
₁Is off, the frequency band of the high-frequency received signal
Output 1 at_ThreeOf the transmission side connection circuit 1 from the
Because the impedance is quite large,
The received signal does not flow into the transmitting side connection circuit 1 and is high.
That the high frequency reception signal has an adverse effect on the transmission side connection circuit 1
There is no.

At this time, the signal transmission characteristics and the signal reflection characteristics of the high-frequency reception signal in the reception-side connection circuit 2 exhibit the characteristics as shown by the solid line and the dotted line in FIG. 3, and the signal transmission characteristic is 1.5 GHz. There is almost no signal attenuation including before and after the frequency band, and the signal reflection characteristic is 1.5G.
The characteristic is sharply increased near the frequency band of Hz.

By the way, the first resistor ₂₅ and the second resistor ₂₆ connected to the receiving side connection circuit 2 are connected to the second diode 2.
_This is for stabilizing the reverse bias voltage applied to both ends of the _third diode 23. Their resistance values can achieve the stabilization of the reverse bias voltage of the second diode 23, as well as the first resistor ₂₅ and the first resistor ₂₅ . (2) Set to a value that reduces the signal transmission loss due to the resistor ( ₂₆ ).

As shown in FIG. 4, as the resistance values of the first resistor ₂₅ and the second resistor ₂₆ are increased, the first resistor 2 5
₅ and the signal transmission loss due to the second resistor 2 ₆ is reduced, but if you increase their resistance, stabilization of the reverse bias voltage of the second diode 2 ₃ can not be sufficiently achieved. From these points, when the signal path impedance of the receiving side connection circuit 2 is 50Ω, the resistance value of the first resistor ₂₅ and the second resistor ₂₆ is about 20 to 1000 times the resistance value, that is, 1KΩ to It is preferable to select a value of about 50 KΩ.

In the first embodiment, the first
Although the DC voltage and the DC voltage of the second DC power supply 2 ₇ of the DC power source 1 ₇ has been described by way of example is 3V, respectively, of these DC voltage according to the present invention is not limited if it is 3V, other It is needless to say that a DC voltage having a value of?

[0038] Thus, according to the antenna switching circuit 10 according to this embodiment, the second diode 2 ₃ into two voltages, i.e., the receiving side connection circuit 2 by selecting supplying the ground voltage and a negative voltage Switching the operation state, switching the frequency band of the high-frequency reception signal (first frequency band, for example, 1.4 GHz band, or second frequency band, for example, 1.5
GHz band switching) setting, it is possible to selectively switch high frequency reception signals of two frequency bands in the receiving side connection circuit 2, and to use the ground voltage without using another antenna switching circuit. It is possible to switch between high-frequency reception signals in two frequency bands only by selectively supplying the high-frequency signal and the negative voltage.

By the way, the antenna switching circuit 10 according to the above-described embodiment includes a high-frequency transmission signal having a frequency of 1.4 GHz and a high-frequency reception signal having a frequency of 1.4 GHz or a high-frequency reception signal having a frequency of 1.5 GHz. In this antenna switching circuit 10, two frequency bands of a switchable high-frequency transmission signal and a high-frequency reception signal are switched between a 1.4 GHz band and a 1.5 GHz band. not stay in can be carried out, the transmitting side connection circuit first diode 1 ₁ other circuit elements except one ₂ or reactance value of 1 _5, and the like or in 1, second diode 2 ₃ in the receiving side connection circuit 2 by changing other circuit elements 2 _1, 2 _2, 2 reactance value such as _4, except for the, you to higher frequency band than those of the frequency band Switching between two frequency bands in a high-frequency transmission signal and a high-frequency reception signal, or switching between two frequency bands in a high-frequency transmission signal and a high-frequency reception signal in a frequency band lower than those frequency bands.

FIGS. 5 to 7 show characteristic diagrams of the antenna switching circuit 10 according to the second embodiment. The frequency band of the high-frequency transmission signal is 1.8 GHz.
The two frequency bands of the high-frequency reception signal are 1.8 GHz and 1.
When the frequency is 9 GHz, the second antenna switching circuit 1
It shows the signal transmission characteristics and signal reflection characteristics obtained at 0. FIG.
FIG. 6 shows signal transmission characteristics and signal reflection characteristics of a high-frequency transmission signal in a frequency band of 8 GHz, and FIG. 6 shows signal transmission characteristics and signal reflection characteristics of a high-frequency reception signal in a frequency band of 1.8 GHz in the receiving-side connection circuit 2; FIG. 7 shows the receiving side connection circuit 2
5 shows the signal transmission characteristics and signal reflection characteristics of the high-frequency reception signal in the 1.9 GHz frequency band.

6 to 8, the horizontal axis represents the frequency expressed in GHz, and the vertical axis represents the signal attenuation (signal transmission characteristic) expressed in dB. The solid line indicates signal transmission characteristics, and the dotted line indicates signal reflection characteristics.

Also, in the antenna switching circuit 10 of the second embodiment, the reception-side connection circuit 2
When processing a high-frequency reception signal in the frequency band of
Supplying a bias voltage of zero voltage to the diode 2 _3, the junction capacitance value of the second diode 2 ₃ is relatively large (e.g., 2 pF) is set to the reception-side connection circuit 2
There when processing high-frequency reception signal in the frequency band of 1.9GHz supplies a reverse bias voltage to the second diode 2 _3, the junction capacitance value of the second diode 2 ₃ is reduced (for example, 0.5 pF) as You have set.

The antenna switching circuit 10 according to the second embodiment
Has the following frequency characteristics.

First, as shown by the solid line in FIG. 6, the signal transmission characteristics of the high-frequency transmission signal having the frequency band of 1.8 GHz in the transmission-side connection circuit 1 are substantially the same as those before and after the frequency band of 1.8 GHz. There is almost no attenuation, and as shown by the dotted line in FIG. 6, the signal reflection characteristic of the high-frequency transmission signal in the transmission-side connection circuit 1 is such that the amount of attenuation sharply increases near the 1.8 GHz frequency band. ing.

As shown by the solid line in FIG. 7, the signal transmission characteristics of the high-frequency reception signal having a frequency band of 1.8 GHz in the receiving-side connection circuit 2 are substantially the same as those before and after the frequency band of 1.8 GHz. There is almost no attenuation, and as shown by the dotted line in FIG. 7, the signal reflection characteristic of the high-frequency reception signal in the receiving-side connection circuit 2 is such that the attenuation increases sharply in the vicinity of the 1.8 GHz frequency band. ing.

Further, as shown by the solid line in FIG. 8, the signal transmission characteristic of the high-frequency reception signal having the frequency band of 1.9 GHz in the receiving-side connection circuit 2 is substantially equal to that of the 1.9 GHz frequency band. There is almost no attenuation, and as shown by the dotted line in FIG. 8, the signal reflection characteristic of the high-frequency reception signal in the reception-side connection circuit 2 is such that the attenuation increases rapidly in the vicinity of the 1.9 GHz frequency band. ing.

[0047] Thus, according to the antenna switching circuit 10 according to the second embodiment, similarly to the antenna switching circuit 10 according to the embodiment described above, the second diode 2 ₃ 2
By selectively supplying various voltages, that is, a ground voltage and a negative voltage, the operation state of the receiving side connection circuit 2 is switched, and the frequency band of the high-frequency reception signal is switched (first frequency band, for example, 1.8 GHz band, or Second frequency band, for example, 1.
9 GHz band switching) setting, it is possible to selectively switch high frequency reception signals of two frequency bands in the receiving side connection circuit 2, and to use the ground voltage without using another antenna switching circuit. It is possible to switch between high-frequency reception signals in two frequency bands only by selectively supplying the high-frequency signal and the negative voltage.

[0048]

As described above, according to the present invention, the first diode for supplying the operating voltage to the first diode and the second diode is provided.
The variable power supply and the second variable power supply are each configured to selectively output two types of voltages. The selection of the two types of voltages output from the first variable power supply causes the transmission side connection circuit to connect the antenna and the transmission unit. Connected (switching to the transmitting side) or disconnected (switching to the receiving side)
When the transmission side connection circuit is set to the disconnected state (switching to the reception side), the operation state of the reception side connection circuit is switched by selecting two types of voltages output from the second variable power supply, and the high frequency reception signal is switched. Switching of frequency band (first frequency band, for example, 1.4 GHz band, or second frequency band, for example, 1.
Since the setting of 5 GHz band) is performed, it is possible to selectively switch the high frequency reception signals of the two frequency bands in the receiving side connection circuit, and to use the second variable power supply of the second variable power supply without using another antenna switching circuit. The switching of the high-frequency reception signals in the two frequency bands can be performed only by the selection output of the kind of the voltage, and there is an effect that an antenna switching circuit whose application range is expanded can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an antenna switching circuit according to the present invention, in which a peripheral circuit portion is shown together with the antenna switching circuit.

FIG. 2 shows a second example of the antenna switching circuit shown in FIG.
FIG. 4 is a characteristic diagram illustrating signal transmission characteristics and signal reflection characteristics of a high-frequency reception signal of a reception-side connection circuit when an applied voltage to a cathode of a diode is a ground voltage.

FIG. 3 shows a second example of the antenna switching circuit shown in FIG.
FIG. 9 is a characteristic diagram showing signal transmission characteristics and signal reflection characteristics of a high-frequency reception signal of the reception-side connection circuit when the voltage applied to the cathode of the diode is 3 V DC of the second DC power supply.

FIG. 4 shows a first example of the antenna switching circuit shown in FIG.
FIG. 9 is a characteristic diagram illustrating a relationship between resistance values of the resistor and the second resistor and transmission loss of a high-frequency reception signal of the reception-side connection circuit.

FIG. 5 is a characteristic diagram illustrating a signal transmission characteristic and a signal reflection characteristic of a high-frequency transmission signal of a transmission-side connection circuit when a first diode and a second diode are on in the antenna switching circuit according to the second embodiment;

FIG. 6 is a diagram illustrating a signal transmission characteristic and a signal reflection characteristic of a high-frequency reception signal of a reception-side connection circuit when a voltage applied to a cathode of a second diode is a ground voltage in the antenna switching circuit according to the second embodiment; FIG.

FIG. 7 is a diagram illustrating a signal transmission characteristic of a high-frequency reception signal of the reception-side connection circuit when the voltage applied to the cathode of the second diode is the DC voltage of 3 V of the second DC power supply in the antenna switching circuit according to the second embodiment; FIG. 4 is a characteristic diagram showing signal reflection characteristics.

FIG. 8 is a circuit diagram showing an example of a configuration of a known antenna switching circuit, and also shows a peripheral circuit portion together with the antenna switching circuit.

FIG. 9 shows a first example of the antenna switching circuit shown in FIG.
FIG. 4 is a characteristic diagram illustrating signal transmission characteristics and signal reflection characteristics of a high-frequency transmission signal of a transmission-side connection circuit when a diode and a second diode are on.

FIG. 10 shows a first example of the antenna switching circuit shown in FIG.
FIG. 4 is a characteristic diagram illustrating signal transmission characteristics and signal reflection characteristics of a high-frequency reception signal of a reception-side connection circuit when a diode and a second diode are off.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Transmission side connection circuit 1 ₁ 1st diode 1 ₂ 1st inductor 1 ₃ 1st capacitor 1 ₄ 2nd capacitor 1 ₅ 2nd inductor 1 ₆ Buffer resistance 1 ₇ 1st DC power supply 1 ₈ 1st changeover switch 1 ₉ Input terminal 1 ₁₀ connected an output terminal 2 receiving side circuit 2 ₁ third inductor 2 ₂ third condenser 2 ₃ second diode 2 ₄ 4 capacitor 2 ₅ first resistor 2 ₆ second resistor 2 ₇ second DC power supply 2 ₈ second switch Switch 2 ₉ Input terminal 2 ₁₀ Output terminal 3 Transmit / receive antenna 4 Antenna shared circuit 4 ₁ Fifth capacitor 4 ₂ 6th capacitor 5 Transmitter (TX) 6 Receiver (RX) 7 Signal input terminal 8 Signal output terminal 10 Antenna switching circuit

Claims (5)

[Claims] 1. A transmission-side connection circuit connected between an antenna and a transmission unit, and a reception-side connection circuit connected between the antenna and a reception unit, wherein the transmission-side connection circuit or the reception unit An antenna switching circuit that alternately turns on and off a side connection circuit to switch the connection between the antenna and the transmission unit or the reception unit, wherein the transmission side connection circuit includes a first diode connected in series to a transmission signal path, A series circuit of a first inductor and a first capacitor connected in parallel to the first diode, and a first variable power supply for selectively outputting two types of voltages, wherein the receiving side connection circuit is connected in series to a reception signal path; A second inductor, a second variable power supply for selectively outputting two types of voltages, a parallel circuit of a second capacitor and a first resistor connected between the reception signal path and a reference voltage point, Second An antenna switching circuit including a parallel circuit of a second diode and a second resistor connected between variable power sources. 2. The antenna switching circuit according to claim 1, wherein the first resistor and the second resistor have the same resistance value. 3. The first variable power supply is characterized in that two kinds of voltages are a reference voltage and a constant positive voltage, and the second variable power supply is such that the two kinds of voltages are a reference voltage and a constant positive voltage. The antenna switching circuit according to claim 1. 4. The transmission signal according to claim 1, wherein the transmission signal is a high frequency signal in a 1.4 GHz band, and the reception signal is a high frequency signal in a 1.4 GHz band or a 1.5 GHz high frequency signal. The described antenna switching circuit. 5. The transmission signal according to claim 1, wherein the transmission signal is a 1.8 GHz band high frequency signal, and the reception signal is a 1.8 GHz band high frequency signal or 1.9 GHz high frequency signal. The described antenna switching circuit.