JPH08228165A - Antenna switch controller in radio communication equipment - Google Patents

Abstract

PURPOSE: To provide an attenuator function for varying an attenuation factor at the time of strong electric field reception by providing a reception signal attenuation means for preventing the input level of a reception circuit from becoming excessive in an antenna switch. CONSTITUTION: When a reception timing comes, a microcomputer 5 turns a control switch 3 to neutral and turns OFF a PIN diode D1. Then, from the output of a level detection circuit 9, the level of reception signals leaked through the PIN diode D2 which is completely turned OFF and inputted to the reception circuit 7 is detected. Then, the reception signal level is compared with a reference value, the resistance value of a voltage controlled type variable resistor (VCR) 4 is varied corresponding to the reception signal level and the control switch 3 is switched to reception. By the constitution, the PIN diode D2 functions as an attenuation factor variable type attenuator as well, and when the reception signal level is high, by appropriately enlarging the ON impedance of the PIN diode D2, the reception signals are attenuated.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a PHS (personal
The present invention relates to a TDD (Time Division Duplex) type wireless communication device typified by a digital mobile phone such as a handy phone system), and in particular, an antenna switch for switching and connecting a common antenna to a transmission / reception circuit during transmission and reception. Regarding the control device.

[0002]

2. Description of the Related Art In a digital portable telephone such as PHS, a transmitting operation and a receiving operation are alternately repeated at high speed. The same antenna is used for both transmission and reception. There is a switch circuit (called an antenna switch) that uses a PIN diode or FET between the antenna and the transmitting end and the receiving end, and the switching operation connects the transmitting end to the antenna during transmission and connects the antenna to the receiving end during reception. Repeat at high speed.

Also, in many wireless communication devices, not limited to this type of digital mobile phone, the high frequency amplifier circuit has an AGC in order to cope with the magnitude and fluctuation of the received signal level.
(Automatic gain control) An amplifier is provided. In a normal circuit configuration, an AGC voltage corresponding to the level of a received signal is generated in the intermediate frequency amplification circuit stage or the demodulation circuit stage, and the voltage controls the gain of the AGC amplifier. This constitutes a feedback loop that stabilizes the level of the received signal input to the demodulation circuit. That is, when the electric field strength of the radio wave of the communication partner is large, the gain of the AGC amplifier is small, and when the electric field strength is small, the gain is large.

[0004]

By the way, the above-mentioned AG
There is a limit to the dynamic range that can be handled by C, and even if the received signal has an excessive level that exceeds the limit, AGC cannot sufficiently reduce distortion. Then, JP-A-6-268
As disclosed in Japanese Patent No. 552, in a wireless communication device of the type in which a transmission / reception shared antenna is switched and connected to a transmission / reception circuit by the antenna switch, a switching element connecting the antenna and the reception circuit when the level of a reception signal is excessive. There is known a method of turning off the switch and guiding only the leak signal of this switching element to the receiving circuit. That is, the switching element that remains off serves as an attenuator of the received signal, and prevents an excessive signal from being input to the receiving circuit.

However, according to this conventional technique, the switching element of the antenna switch circuit is turned on and the AG
There is a too large difference in the total gain (total characteristics of the attenuation rate and the amplification rate) of the receiving system between the state in which the gain of the C amplifier is minimized and the state in which the switching element is turned off and the element functions as an attenuator. There is a problem that it is too difficult to create an intermediate state. In other words, turning off the switching element and receiving it as an attenuator is merely a measure for avoiding an abnormal situation, and does not appropriately attenuate the received signal according to the level of the strong electric field input.

Of course, if an attenuator circuit capable of controlling the attenuation rate with a voltage signal is provided in the first stage of the receiving circuit, the attenuation rate can be variably controlled appropriately according to the input level even for a strong electric field input. However, providing such an attenuator circuit separately complicates the circuit and causes another problem in terms of mounting design and price.

The present invention has been made in view of the above background, and an object of the present invention is to solve the above problems and to add a simple control means to an antenna switch so that input is performed when a strong electric field is received. It is an object of the present invention to provide an antenna switch control device in a wireless communication device that has an attenuator function in which the attenuation factor changes according to the level.

[0008]

In order to achieve the above object, in an antenna switch control device in a radio communication device according to the present invention, the antenna switch control device is inserted in series in a transmission signal path connecting a transmission circuit and an antenna and turned on at the time of transmission. In a wireless communication device including a first switching element that becomes: and a second switching element that is inserted in series in a reception signal path that connects the antenna and the reception circuit and that is turned on at reception, the reception signal level at reception The received signal attenuating means for preventing the input level of the receiving circuit from becoming excessive by appropriately changing the impedance of the second switching element according to the above is provided (claim 1).

Here, at the start of reception, first, with the second switching element turned off, the element concerned is leaked and the received signal level input to the receiving circuit is checked,
If the level at this time is small, the second switching element is turned on with the minimum impedance, and if the level is large, the control method of turning on the second switching element with an appropriately large impedance can be adopted (claim 2).

As another solution, a first switching element that is inserted in series in a transmission signal path connecting a transmission circuit and an antenna and is turned on during transmission, and a reception signal path connecting the antenna and the reception circuit. In a wireless communication device including a second switching element that is connected between a ground and a ground and is turned on at the time of transmission, the second switching element is turned on at an appropriate impedance in accordance with a reception signal level at the time of reception. A received signal attenuating means for preventing the input level of the receiving circuit from becoming excessive may be provided (claim 3).

At the start of reception, first, the level of the received signal input to the receiving circuit is checked while the second switching element is turned on with the minimum impedance,
If the level at this time is low, the second switching element is turned off, and if the level is high, the control method of appropriately increasing the impedance of the second switching element can be adopted.

[0012]

According to the first aspect of the present invention, the second switching element inserted in series in the reception signal path also functions as an attenuation factor variable attenuator. That is, not only is the binary control of the second switching element completely ON and completely OFF performed, but when the level of the received signal is high, the ON impedance of the second switching element is appropriately increased according to the degree. , Attenuate the received signal appropriately.

On the other hand, the second aspect of the present invention comprises claim 3 and claim 4.
In the invention, the second switching element connected between the reception signal path and the ground also functions as an attenuation factor variable attenuator. In other words, not only the second switching element is binary-controlled to be completely on and completely off, but when the level of the received signal is high, the second switching element is turned on with an appropriate impedance according to the degree of the received signal, and the received signal By leaking a part to the ground side through the second switching element, the signal input to the receiving circuit is appropriately attenuated.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of an antenna switch control device for a wireless communication device according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an embodiment of the first invention. As shown in the figure, here, PIN diodes D1 and D are used as the first and second switching elements.
2 is used. That is, the PIN diode D1 is inserted in series in the transmission signal path connecting the transmission end TX and the antenna 1, and the PIN diode D2 is inserted in series in the reception signal path connecting the antenna 1 and the reception end RX. Transmission end T
Between X and the diode D1, the diode D2 and the receiving end RX
Between the cathodes of both diodes D1 and D2 and the antenna 1
Between capacitors C1 and C for cutting DC,
2, C3 are connected. Furthermore, both diodes D1,
The cathode of D2 is connected to ground via an inductor L3 for cutting high frequencies.

There is a DC power supply 2 and a control switch 3 for alternately turning on / off the PIN diodes D1 and D2. The "transmission" terminal of this control switch 3 and the diode D
An inductor L1 is connected between the anodes of the voltage control variable resistor (VCR) 4 and the inductor L between the "reception" terminal of the control switch 3 and the anode of the diode D2.
2 are connected in series. The control switch 3, the VCR 4, and the like are controlled by the microcomputer 5 that performs various controls of this wireless communication device.

When the control switch 3 is connected to the "transmission" terminal, the DC power supply 2 is connected to the resistor 6 → inductor L1 → PIN.
A direct current flows in the loop of the diode D1 → inductor L3, and this bias current causes the PIN diode D1
Turns on. At this time, the transmission signal from the transmission terminal TX is supplied to the antenna 1 through the diode D1.

When the control switch 3 is connected to the "receive" terminal, the DC power source 2 is connected to the resistor 6 → VCR 4 → inductor L.
A direct current flows through the loop of 2 → PIN diode D2 → inductor L3, and this bias current turns on the PIN diode D2. At this time, the received signal from the antenna 1 is supplied to the receiving end RX through the diode D2 (input to the receiving circuit 7). The bias current supplied to the PIN diode D2 is variably controlled by the VCR4. The VCR 4 is controlled by the microcomputer 5 as follows. A change in the bias current of the PIN diode D2 changes the on-impedance of the diode D2. The change in the on-impedance of the diode D2 changes the attenuation rate of the reception signal input to the reception circuit 7.

The receiving circuit 7 includes the AGC amplifier 8 and the level detecting circuit 9 described above. A signal indicating the received signal level is output from the level detection circuit 9, and the level detection signal is introduced into the microcomputer 5. As described in detail below, the microcomputer 5 controls the gain of the AGC amplifier 8 and the resistance value of the VCR 4 based on the output of the level detection circuit 9.

Of the control performed by the microcomputer 5, the processing functions relating to the present invention are shown in the flowchart of FIG. At the time of transmission, the control switch 3 is set to "transmission" to turn on the PIN diode D1 (S101, S102). When the reception timing comes, the control switch 3 is set to "neutral" to turn off the PIN diode D1 (the PIN diode D2 is still off), and the output of the level detection circuit 9 is read in that state (S103, S104). ).

At this time, what is detected by the level detecting circuit 9 is the received signal level which is leaked from the PIN diode D2 which is completely off and input to the receiving circuit 7.
The microcomputer 5 uses the received signal level A at this time as the reference value B
And are compared (S105). If the reception signal level A is lower than the reference value B, the resistance value of the VCR 4 is minimized and the control switch 3 is switched to "reception" (S106,
S107). Then, the maximum bias current flows through the PIN diode D2, and the diode D2 is completely turned on. The reception signal is input to the reception circuit through the diode D2 which is completely on. In this state, the microcomputer 5
Checks the output of the level detection circuit 9 as needed, and controls the gain of the AGC amplifier 8 appropriately according to the received signal level (S108). This keeps the received signal level in the receiving circuit 7 in an appropriate state.

In step 105, if the completely off PIN diode D2 leaks and the received signal level A input to the receiving circuit is larger than the reference value B, the process branches to the step 109 side. In this case, A
The gain of the GC amplifier 8 is minimized and the control switch 3 is switched to "reception" (S109, S110).

Then, a bias current flows through the PIN diode D2. The reception signal is input to the reception circuit 7 through the PIN diode D2 which is turned on by this bias current. In this state, the microcomputer 5 checks the output of the level detection circuit 9 at any time, and according to the received signal level, the VCR 4
The resistance value of is controlled appropriately (S111). That is, PI
The bias current flowing through the N diode D2 is appropriately changed, the on-impedance of the PIN diode D2 is appropriately changed, and the attenuation factor of the reception signal passing through the PIN diode D2 is appropriately changed. This keeps the received signal level in the receiving circuit 7 in an appropriate state.

FIG. 3 shows an embodiment of the second invention. As shown in the figure, in this embodiment, the circuit configuration of the antenna switch is different from that of the embodiment shown in FIG. That is, the PIN diode D1 is inserted in series in the transmission signal path connecting the transmission end TX and the antenna 1. On the other hand, PIN
The diode D3 is connected between the receiving signal path from the antenna 1 to the receiving end RX and the ground.

When the control switch 3 is connected to "transmission", the DC power source 2 is connected to the resistor 6 → the inductor L1 → PIN.
A direct current flows through the loop of the diode D1 → the phase shifter 10 → the PIN diode D3. This DC current becomes a bias current for both PIN diodes D1, D3, and both diodes D1, D3 are completely turned on. At this time, the transmission signal is supplied to the antenna 1 through the diode D1.

On the other hand, the control switch 3 is set to "reception" in the neutral position.
Then, the DC power supply 2 is disconnected, and both PIN diodes D1 and D3 are completely turned off. At this time, the reception signal from the antenna 1 is not substantially attenuated and the reception circuit 7
Is input to

When the control switch 3 is connected to "attenuation", the DC power supply 2 is connected to the resistance → VCR4 → inductor L3 →
A direct current flows through the loop of the phase shifter 10 → PIN diode D3, and this current turns on the PIN diode D3. However, at this time, the bias current supplied to the PIN diode D3 is variably controlled by the VCR 4.

The VCR 4 is controlled by the microcomputer 5 as follows. A change in the bias current of the PIN diode D3 changes the on-impedance of the diode D3. By turning on the diode D2 with an appropriate impedance instead of completely turning off the antenna 1,
A part of the received signal transmitted from the signal path to the receiving circuit 7 leaks to the ground through the diode D3. The amount of leakage changes depending on the on-impedance of the diode D3, and as a result, the attenuation rate of the reception signal input to the reception circuit 7 changes.

The principle of the control procedure executed by the microcomputer 5 may be the same as that of the first embodiment of the invention. That is, as shown in FIG. 4, the control switch 3 is kept in the “transmission” state for a while even after the reception tamming (the transmission operation ends), and P
The output of the level detection circuit 9 is checked in a state in which the attenuation rate (leak rate) of the received signal is maximized with the IN diode D3 kept completely on (S201 to 205). If the received signal level A at this time is smaller than the reference value B, the control switch 3 is switched to "reception" and normal control, that is, both PIN diodes D1 and D3 are completely turned off,
The signal received by the diode D3 is received in a state where the attenuation rate (leak rate) of the received signal is minimized.
The gain of the C amplifier 8 is appropriately controlled (S206 to S20).
8).

When the received signal level A when the received signal attenuation rate (leak rate) is maximum is larger than the reference value B, the gain of the AGC amplifier 8 is minimized and the control switch 3 is "attenuated". Switch to PIN diode D
Turn on 3 with appropriate impedance. In that state, the output of the level detection circuit 9 is checked at any time, the resistance value of the VCR 4 is appropriately changed according to the reception level, and the attenuation rate (leak rate) of the reception signal by the PIN diode D3 is appropriately controlled (S209-). S211).

[0030]

As described above, the antenna switch control device in the wireless communication device according to the present invention has the following effects. That is, in the first aspect of the invention, the switching element, which is inserted in series in the reception signal path and constitutes the antenna switch, also functions as an attenuator of variable attenuation factor. That is, not only is the binary control of the switching element completely ON and completely OFF performed, but when the level of the received signal is high, the ON impedance of the switching element is appropriately increased according to the level of the received signal so that the received signal is received. It can be appropriately attenuated.

In the second aspect of the invention, the switching element, which is connected between the reception signal path and the ground and constitutes the antenna switch, also functions as an attenuator of variable attenuation factor. That is, this switching element is not only binary-controlled to be completely on and completely off, but when the level of the received signal is high, the switching element is turned on with an appropriate impedance according to the degree thereof, and a part of the received signal is By leaking to the ground side through the switching element, the signal input to the receiving circuit can be appropriately attenuated.

In any of the inventions, by adding a simple control means to the antenna switch circuit for switching and connecting the antenna for both transmission and reception to the transmission / reception circuit, the attenuation rate changes according to the input level when a strong electric field is received. The attenuator function can be added, and by combining with the AGC function, the dynamic range of the antenna input that can be well received becomes wide.

[Brief description of drawings]

FIG. 1 is a main part configuration diagram showing an embodiment of a first invention.

FIG. 2 is a flowchart showing an operation / control procedure of the embodiment.

FIG. 3 is a main part configuration diagram showing an embodiment of a second invention.

FIG. 4 is a flowchart showing an operation / control procedure of the embodiment.

[Explanation of symbols]

1 Antenna 2 DC Power Supply 3 Control Switch 4 VCR (Voltage Controlled Variable Resistor) 5 Microcomputer 6 Resistance 7 Reception Circuit 8 AGC Amplifier 9 Level Detection Circuit 10 Phase Shifter TX Transmission End RX Reception End D1, D2, D3 PIN Diode ( Switching element) C1, C2, C3 capacitors L1, L2, L3 inductors

Claims (4)

[Claims] 1. A first switching element that is inserted in series in a transmission signal path connecting a transmission circuit and an antenna and is turned on at the time of transmission, and is inserted in series in a reception signal path connecting the antenna and a reception circuit. In a wireless communication device including a second switching element that is turned on during reception, the input level of the reception circuit is excessive by appropriately changing the impedance of the second switching element according to the reception signal level during reception. An antenna switch control device in a wireless communication device, comprising: a received signal attenuating means for preventing the occurrence of the above. 2. At the start of reception according to claim 1, first, while the second switching element is off, the element is leaked to check the level of a received signal input to the receiving circuit. An antenna switch control device in a wireless communication device, wherein when the level is low, the second switching element is turned on with a minimum impedance, and when the level is high, the second switching element is turned on with an appropriately large impedance. 3. A first switching element that is inserted in series in a transmission signal path that connects a transmission circuit and an antenna and that turns on during transmission, and is connected between a reception signal path that connects the antenna and the reception circuit and ground. In a wireless communication device including a second switching element that is turned on during transmission, the input level of the receiving circuit is increased by turning on the second switching element with an appropriate impedance according to the received signal level during reception. An antenna switch control device in a wireless communication device, comprising: a received signal attenuating means for preventing the signal from becoming excessive. 4. The reception signal level input to the reception circuit according to claim 3, when the reception is started, the second switching element is turned on with a minimum impedance, and the level at this time is small. An antenna switch control device for a wireless communication device, wherein, for example, the second switching element is turned off, and when the level is high, the impedance of the second switching element is appropriately increased.