JPH06268404A - High frequency signal switch - Google Patents

Abstract

PURPOSE:To obtain a compact and inexpensive high frequency signal switcher in which an isolation between a transmitter and a receiver can be satisfactory, and an insertion loss can be reduced. CONSTITUTION:An antenna terminal 1 is connected through a 1/4 wavelength transmission line 6 with a transmitter TX, and connected through a transmission line 9 with a receiver RX. The 1/4 wavelength transmission line 6 is grounded through a PIN diode 4 in high frequency mode, and a PIN diode 3 is serially inserted into the transmission line 9. In a transmission mode, an inverse bias voltage is impressed on those PIN diodes 3 and 4, and the PIN diodes 3 and 4 are turned into off states. A transmission signal is transmitted to the antenna terminal 1 without being transmitted to the PIN diode, so that the insertion loss in the transmission mode can be sharply reduced. Also, the snaking of the transmission signal to the receiver can be almost completely prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency signal switch, and more specifically, to a transmission signal output from a transmitter to a common input / output terminal and a reception signal applied from the common input / output terminal to a receiver. The present invention relates to a high-frequency signal switch for complementary switching between and in response to switching between a transmission mode and a reception mode.

[0002]

2. Description of the Related Art In recent mobile communication devices such as car phones and mobile phones, for example, TDMA (Time Div) is used.
An antenna switching device, which is an example of a high-frequency signal switching device, may be provided in order to carry out the communication of the multiple signals. This antenna switch is
This is to enable a single antenna to be shared by a transmitter and a receiver (using the same frequency) in the same station in a time-division manner. Transmission output from the transmitter to the antenna terminal The signal and the reception signal given to the receiver from the antenna terminal are complementarily switched.

FIG. 4 is a diagram showing a configuration of a conventional series-shunt type antenna switching device. In FIG. 4, the antenna terminal 1 is connected to the PIN via the quarter-wave transmission line 6.
It is connected to the anode of the diode 4 and the input terminal of the receiver RX. Further, the antenna terminal 1 is connected to the output end of the transmitter TX via the PIN diode 3.

In the antenna switching device shown in FIG. 4, in the transmission mode, a forward bias voltage is applied between the anode and cathode of PIN diodes 3 and 4, whereby both PIN diodes 3 and 4 are turned on. As a result, the transmission signal output from the transmitter TX passes through the PIN diode 3 and passes through the antenna terminal 1 to the antenna A.
Supplied to NT. Further, since the impedance of the ¼ wavelength transmission line 6 viewed from the antenna terminal 1 side is almost infinite, the reception signal supplied from the antenna ANT to the antenna terminal 1 and the transmission signal from the transmitter TX are 1 /
It does not propagate on the 4-wavelength transmission line 6 and is not input to the receiver RX.

On the other hand, in the reception mode, no bias voltage is applied to PIN diodes 3 and 4, and PIN diodes 3 and 4 are both turned off. As a result, 1/4
The wavelength transmission line 6 is simply a transmission line, and the antenna AN
The received signal supplied from T to the antenna terminal 1 is 1/4.
It propagates on the wavelength transmission line 6 and is input to the receiver RX. The reception signal supplied from the antenna ANT to the antenna terminal 1 is blocked by the PIN diode 3 and is not input to the transmitter TX.

[0006]

In the conventional series-shunt type antenna switching device shown in FIG. 4, as disclosed in, for example, Japanese Patent Laid-Open No. 57-73533, the PIN diode 4 is used in the receiving mode. On the other hand, no bias voltage is applied. Therefore, the PIN diode 4 is not completely turned off, and a leakage path for a high-frequency signal that escapes to the ground via the PIN diode 4 is formed. As a result, there is a problem that the insertion loss of the propagation path of the received signal increases in the reception mode.

Further, in the conventional series-shunt type antenna switching device, when the PIN diode 3 is turned on in the transmission mode, the impedance of the PIN diode 3 does not become completely 0 due to its on resistance. Therefore, in the transmission mode, there is a problem that the insertion loss of the transmission signal propagation path becomes large. Similarly, when the PIN diode 4 is turned on in the transmission mode, the PIN
The impedance of the diode 4 is not completely zero due to its ON resistance. Therefore, one end of the quarter-wave transmission line 6 is not completely grounded, and the impedance of the quarter-wave transmission line 6 viewed from the antenna terminal 1 does not become sufficiently large (almost infinite). As a result, the transmission signal sneak into the receiver RX side, that is, the isolation between the transmitter TX and the receiver RX is deteriorated, and the amplifier constituting the front end of the receiver RX may be destroyed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a high-frequency signal switcher which has good isolation between a transmitter and a receiver, has a small insertion loss, and is small in size and inexpensive.

[0009]

The invention according to claim 1 is
A high-frequency signal for complementary switching between the transmission signal output from the transmitter to the common input / output terminal and the reception signal applied to the receiver from the common input / output terminal in response to the switching between the transmission mode and the reception mode. A switch, which is arranged between the transmitter and the common input / output terminal, is arranged between the receiver and the common input / output terminal, and is provided with a first high frequency signal propagation path for propagating a transmission signal. Second for propagating signals
Of the high frequency signal propagation path, the anode of which is connected to the first high frequency signal propagation path, and the cathode of which is serially inserted into the first switching diode and the second high frequency signal propagation path which are grounded at high frequencies. By applying a reverse bias voltage to the second switching diode and the first and second switching diodes in the transmission mode to turn off the first and second switching diodes, the first switching diode is turned off. Reverse bias voltage applying means for propagating a transmission signal on the high-frequency signal propagation path and blocking propagation of a reception signal on the second high-frequency signal propagation path is provided.

[0010]

In the invention according to claim 1, the first switching diode for the shunt is connected to the first high frequency signal propagation path (transmission path for transmitting the transmission signal), and the second high frequency signal propagation path ( A second switching diode is inserted in series in a propagation path for receiving signal transmission, and a reverse bias voltage is applied to these first and second switching diodes in the transmission mode to turn them off. Thus, the transmission signal is propagated on the first high-frequency signal propagation path, and the transmission signal propagation on the second high-frequency signal propagation path is blocked. As described above, in the present invention, the transmission signal is propagated to the common input / output terminal without passing through the diode, so that the insertion loss in the transmission mode is significantly reduced. In addition, the second switching diode almost completely prevents the transmission signal from sneaking into the receiver in the transmission mode.

[0011]

1 is a circuit diagram showing the configuration of an antenna switching device according to an embodiment of the present invention. In FIG. 1, an antenna terminal 1 to which an antenna ANT is connected is connected to one end of a quarter wavelength transmission line 6 whose length is selected as a quarter wavelength of a high frequency signal propagating, and a high frequency coil L1.
Is connected to the first bias terminal 11 via. 1/4
The other end of the wavelength transmission line 6 is connected to the anode of the PIN diode 4 and also has a DC cut capacitor C.
1 to the output of the final stage amplifier of the transmitter TX. Further, the cathode of the PIN diode 4 is grounded at a high frequency via a high frequency bypass capacitor C3. Further, the cathode of the PIN diode 4 is connected to the second bias terminal 12 via the high frequency coil L2. The antenna terminal 1 is connected to one end of the transmission line 9. This transmission line 9 has a PIN diode 3
Are inserted in series. The other end of the transmission line 9 is connected to the third bias terminal 13 via the high frequency coil L3, and is also connected to the amplifier forming the front end of the receiver RX via the DC cut capacitor C2.

As described above, the antenna switching device shown in FIG. 1 is constructed as a series shunt type antenna switching device, like the conventional antenna switching device shown in FIG. However, unlike the conventional antenna switching device shown in FIG. 4, the 1/4 wavelength transmission line 6 and the PIN diode 4 are provided on the transmitter TX side, and the PIN diode 3 is provided on the receiver RX side.

Here, in the conventional antenna switch shown in FIG. 4, since the reverse bias voltage is not applied to the PIN diode 4, when the PIN diode 3 is ON, the power of the transmitter is transmitted by 1/4 wavelength. When applied to the PIN diode 4 through the line 6, a leak current may flow in the PIN diode 4, which may distort the transmission signal reaching the antenna ANT. As a result, conventionally, it was not possible to adopt the configuration shown in FIG. 1 which emphasizes reduction of insertion loss. On the other hand, in the present embodiment, as described below, the reverse bias voltage is applied to turn the PIN diodes 3 and 4 into the OFF state.
It is possible to reduce the distortion of the PIN diodes 3 and 4 when it is OFF. As a result, it was possible to adopt a configuration as shown in FIG. 1 which emphasizes reduction of insertion loss.

Next, the operation of the embodiment shown in FIG. 1 will be described. In the reception mode, the transmitter TX is disabled and does not output a transmission signal.
First, in the transmission mode, a bias voltage of 0 V is applied to the first bias terminal 11, and a bias voltage of + Vs is applied to the second and third bias terminals 12 and 13. Since + Vs> 0V, the reverse bias voltage is applied between the anodes and cathodes of the PIN diodes 3 and 4. Therefore, P
Both the IN diodes 3 and 4 are turned off.

As a result, the 1/4 wavelength transmission line 6 becomes a simple transmission line, and the transmission signal from the transmitter TX is 1/4.
It propagates on the wavelength transmission line 6 and is supplied to the antenna terminal 1. In this way, the transmission signal propagates only through the quarter wavelength transmission line 6 and is supplied to the antenna terminal 1 without passing through the PIN diode. Therefore, the insertion loss in the propagation path of the transmission signal becomes extremely small. Further, since the PIN diode 4 is completely turned off by applying the reverse bias voltage, the high frequency signal transmitted through the PIN diode 4 as in the conventional series-shunt type antenna switching device shown in FIG. No leak path is formed.
Therefore, it is possible to prevent an increase in insertion loss in the propagation path of the transmission signal.

On the other hand, in the transmission line 9, the PIN diode 3 blocks the signal propagation almost completely. Therefore, the transmission signal from the transmitter TX is not input to the receiver RX. Therefore, the isolation between the transmitter TX and the receiver RX in the transmission mode can be maintained in a good state, and the receiver RX can be prevented from being damaged by the sneak of the transmission signal.

Next, in the reception mode, a bias voltage of + Vs is applied to the first bias terminal 11, and a bias voltage of 0V is applied to the second and third bias terminals 12 and 13. Since + Vs> 0V, PI
A forward bias voltage is applied between the anodes and cathodes of the N diodes 3 and 4.
Therefore, PIN diodes 3 and 4 are both turned on.

As a result, the reception signal supplied from the antenna ANT to the antenna terminal 1 is input to the receiver RX via the transmission line 9 and the PIN diode 3. On the other hand, 1
The quarter wavelength transmission line 6 has a PIN diode 4 at one end.
Since it is grounded via the capacitor C3, the impedance of the quarter-wave transmission line 6 viewed from the antenna terminal 1 side increases. Therefore, the reception signal supplied from the antenna ANT to the antenna terminal 1 does not propagate on the quarter wavelength transmission line 6 and is not input to the transmitter TX.

In the present embodiment, when the PIN diode 3 is turned on in the reception mode, the impedance of the PIN diode 3 is not completely zero due to its on resistance. Therefore, in the present embodiment, the insertion loss of the propagation path of the reception signal in the reception mode increases by the ON resistance of the PIN diode 3. On the other hand, in the conventional series-shunt type antenna switching device shown in FIG. 4, the ON resistance of the PIN diode 3 increases the insertion loss of the transmission path of the transmission signal in the transmission mode. Such a problem is caused by using a high gain amplifier in the front end portion of the receiver RX in this embodiment, and in the conventional antenna switching device shown in FIG. 4, an amplifier in the front end portion of the transmitter TX. Can be solved by using a high gain one. However, the amplifier in the transmitter TX is generally large and expensive due to its high power compared to the amplifier in the receiver RX. Therefore, when a high gain amplifier is used as the amplifier in the transmitter TX, the structure of the transmitter TX becomes large and expensive. On the other hand, even if a high-gain amplifier is used as the amplifier in the receiver RX, the size of the receiver RX does not increase so much and the cost does not increase. Therefore, the present embodiment is advantageous in terms of downsizing and cost of the device, as compared with the conventional antenna switching device shown in FIG.

FIG. 2 is a graph showing the voltage-current characteristics of the PIN diode. The ideal method of determining the bias voltage Vs in the above embodiment will be described below with reference to FIG. In FIG. 2, Vf is the rising voltage of the diode, and Vaf is the reverse breakdown voltage.
Here, assuming that the intermediate voltage between the rising voltage Vf and the reverse breakdown voltage Vaf is Vs ', Vs' becomes Vs'≈ (Vf + Vaf) / 2. Generally, Vf≈0.5 to 0.8 V, and V
af <−7V. Therefore, if the bias voltage Vs is selected so that −Vs ′ = + Vs, the forward bias voltage + Vs becomes sufficiently higher than the rising voltage Vf, and the diode is in a complete ON state. On the other hand, the reverse bias voltage −Vs is sufficiently lower than 0V and is sufficiently higher than the reverse breakdown voltage Vaf. Therefore, the diode can be completely turned off while expecting a certain safety factor so that the diode is not destroyed.

FIG. 3 is a circuit diagram showing the structure of an antenna switching device according to another embodiment of the present invention. In FIG.
The same bias voltage as that of the first bias terminal 11 in the embodiment shown in FIG. 1 is applied to the first bias terminal 11. The bias voltage applied to the first bias terminal 11 is supplied to each one end of the quarter wavelength transmission line 6 and the transmission line 9 via the high frequency coil L1, and
It is supplied to the input terminal of the inverter 20. The input terminal of the inverter 20 has a capacitor C4 for high frequency bypass.
Is grounded via a high frequency. The output of the inverter 20 is supplied to the PI via the resistor R1 and the high frequency coil L2.
The resistor R1, the high frequency coil L2, the resistor R2 and the high frequency coil L3 are provided to the cathode of the N diode 4.
And to the cathode of the PIN diode 3 via the transmission line 9. Here, the inverter refers to a logic element whose output voltage is "low" when the input voltage is "high" or whose output voltage is "high" when the input voltage is "low". Can be used. A resonance coil L4 is connected in parallel to the PIN diode 3. The other configurations of the embodiment shown in FIG. 3 are similar to those of the embodiment shown in FIG. 1, and corresponding parts are designated by the same reference numerals and the description thereof will be omitted.

In the embodiment shown in FIG. 3, in the transmission mode, a bias voltage of 0 V is applied to the first bias terminal 11. Therefore, a bias voltage of 0 V is applied to each anode of the PIN diodes 3 and 4. At this time, the inverter 20 inverts the bias voltage of 0V applied from the first bias terminal 11, so that the output voltage thereof becomes + Vs. Therefore, the cathodes of the PIN diodes 3 and 4 are +
A bias voltage of Vs is applied. As a result, the PIN diodes 3 and 4 are in the off state with the reverse bias voltage applied to both. Therefore, 1/4
The wavelength transmission line 6 is simply a transmission line, and the transmission signal from the transmitter TX propagates on the quarter wavelength transmission line 6 and is supplied to the antenna terminal 1. On the other hand, PIN diode 3
Prevents the transmission signal from the transmitter TX from sneaking into the receiver RX. The resonance coil L4 cooperates with the PIN diode 3 to form a parallel resonance circuit, and cancels the capacitive component generated in the PIN diode 3. This can further increase the isolation between the transmitter TX and the receiver RX.

In the embodiment shown in FIG. 3, in the reception mode, a bias voltage of + Vs is applied to the first bias terminal 11. Therefore, a bias voltage of + Vs is applied to each anode of the PIN diodes 3 and 4. At this time, the inverter 20 inverts the + Vs bias voltage applied from the first bias terminal 11, so that the output voltage thereof becomes 0V. Therefore, a bias voltage of + Vs is applied to each cathode of the PIN diodes 3 and 4. As a result, P
A forward bias voltage is applied to each of the IN diodes 3 and 4, and they are in an ON state. Therefore, the reception signal supplied from the antenna ANT to the antenna terminal 1 is given to the receiver RX via the transmission line 9. On the other hand, since the one end of the quarter wavelength transmission line 6 is grounded via the PIN diode 9, the reception signal supplied from the antenna ANT to the antenna terminal 1 propagates on the quarter wavelength transmission line 6. No input to transmitter TX.

Although each of the embodiments described above is constructed as an antenna switching device, the present invention is
If the configuration has one common input / output terminal and switches between the transmission signal output from the transmitter to the common input / output terminal and the reception signal supplied from the common input / output terminal to the receiver, then other than the antenna switch It can also be applied to a high-frequency signal switch. For example, the common input / output terminal may be coupled to another system by a coaxial cable or an optical cable.

[0025]

As described above, according to the present invention, since the second switching diode is completely off in the transmission mode, the electric power leaking through the second switching diode is reduced. It is possible to significantly reduce the insertion loss in the transmission mode. Further, by turning off the second switching diode in the transmission mode, the sneak of the transmission signal to the receiver is almost completely blocked, so that the isolation between the transmitter and the receiver can be kept in a good state. it can. Therefore, it is possible to prevent the amplifier in the receiver from being destroyed by the sneak of the transmitted signal.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an antenna switching device according to an embodiment of the present invention.

FIG. 2 is a graph showing voltage-current characteristics of a PIN diode.

FIG. 3 is a circuit diagram showing a configuration of an antenna switching device according to another embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional series-shunt type antenna switching device.

[Explanation of symbols]

 1: Antenna terminal 3, 4: PIN diode 6: Quarter wave transmission line 9: Transmission line 11: First bias terminal 12: Second bias terminal 13: Third bias terminal 20: Inverter TX: Transmitter RX: Receiver

Claims (1)

[Claims] 1. A transmission signal output from a transmitter to a common input / output terminal and a reception signal applied to a receiver from the common input / output terminal are complemented in response to switching between a transmission mode and a reception mode. A high-frequency signal switching device for switching between the transmitter and the common input / output terminal, the first high-frequency signal propagation path for propagating the transmission signal; A second high-frequency signal propagation path for propagating the received signal, the anode being connected to the first high-frequency signal propagation path, and the cathode being grounded at a high frequency. A first switching diode, a second switching diode inserted in series in the second high-frequency signal propagation path,
Switching diode, and in transmission mode,
A reverse bias voltage is applied to the first and second switching diodes to turn off the first and second switching diodes, thereby propagating a transmission signal on the first high-frequency signal propagation path. A high-frequency signal switch, comprising reverse bias voltage applying means for blocking the propagation of the received signal on the second high-frequency signal propagation path.