JPH06318883A - Radio communication terminal equipment - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a wireless communication terminal apparatus capable of obtaining a stable reception output without causing intermodulation distortion even when an input of a large signal level is given. A transmission unit 13 for transmitting a signal and a reception unit 14 for receiving a signal are selectively connectable to a common antenna 11 via an antenna switching unit 12, and the antenna switching unit 12 has a forward current PIN diodes D1 and D2 having characteristics such that their internal resistance is reduced by increasing
Is provided to select the switching of the transmitting section 13 and the receiving section 14 with respect to the antenna 11 depending on whether the PIN diodes D1 and D2 are conductive or non-conductive, and the PIN diodes D1 and D2 are switched depending on the level of the input signal at the receiving section 14. The internal resistance is controlled to control the input signal level to the receiving unit 14 to be constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication terminal apparatus in which a transmitting section for transmitting a signal and a receiving section for receiving a signal can be selectively connected to a common antenna via antenna switching means.

[0002]

2. Description of the Related Art Unidirectional communication system and T using the same frequency
In a wireless communication terminal device used in a DD (Time Division Duplex) communication system, a transmitting unit and a receiving unit share one antenna.

FIG. 3 shows an example of this type of wireless communication terminal apparatus, in which an antenna switching section 2 is connected to a shared antenna 1 and a transmitting section 3 and a receiving section 4 are connected via this antenna switching section 2. is doing.

In this case, the antenna switching unit 2 is
The terminal is grounded via a capacitor C1 and is grounded via a series circuit composed of a coil L1, a PIN diode D1, a coil L2 and a PIN diode D2, and
Connect the connecting point of diode D1 and coil L2 to capacitor C4.
Grounded through.

In such an antenna switching section 2, the antenna 1 is connected to the connection point of the diode D1 and the coil L2 via the capacitor C3, and the coil L1 and the PIN are connected.
The power amplifier 31 of the transmitter 3 is connected to the connection point of the diode D1 via the capacitor C2, and the high frequency amplifier 41 of the receiver 4 is connected to the connection point of the coil L2 and the PIN diode D2 via the capacitor C5. There is.

The high frequency amplifying section 41 comprises an antenna switching section 2
The base of the transistor Q1 is connected to the connection point between the coil L2 and the PIN diode D2 via the capacitor C5. The transistor Q1 has its base grounded via a series circuit of a resistor R1 and a capacitor C6, its emitter grounded via a parallel circuit of a capacitor C7 and a resistor R2, and its collector connected to a primary circuit of a transformer T and a parallel circuit of a capacitor C8. And the capacitor C9 to ground, and the connection between the primary winding of the transformer T and the capacitor C9 is connected to the VCC terminal via the resistor R3. Then, the RF output is taken out from the secondary winding side of the transformer T. In this case, the VAGC terminal is connected to the connection point between the resistor R1 and the capacitor C6.

In such a wireless communication terminal device, the control voltage VCTL is not applied to the VCTL terminal of the antenna switching section 2 during reception (VCTL (R shown in FIG. 4
X)). Then, since the PIN diodes D1 and D2 have the forward current-internal resistance characteristics as shown in FIG. 4, the internal resistance is largely non-conductive, and the radio wave received from the antenna 1 is received by the coil on the receiving unit 4 side. L2, capacitor C
It is given as an input signal to the transistor Q1 through 2 through. Then, it is amplified by the transistor Q1 and the transformer T
Is taken out as an RF output from the secondary winding side. In this case, since the transistor Q1 suppresses the fluctuation of the output level with respect to the fluctuation of the received signal, the control voltage VAG from the detection circuit (not shown) corresponding to the output level of the transistor Q1 is applied.
Automatic gain control (AGC) is performed by feeding back C to the VAGC terminal on the base side.

On the other hand, at the time of transmission, when a control voltage VCTL of a predetermined level is applied to the VCTL terminal of the antenna switching unit 2 (VCTL (TX) shown in FIG. 4), a forward current shown by a broken line A in the drawing flows and the PIN is applied. The diodes D1 and D2 are shown in FIG.
Due to the characteristics shown in (1), the internal resistance is reduced and the device becomes conductive.
In this state, the transmission wave amplified by the power amplification unit 31 on the transmission unit 3 side is sent to the antenna 1 via the capacitor C2, the diode D1 and the capacitor C3, and the antenna 1
More space is output. In this case, since the diode D2 is in a conducting state, the parallel circuit formed by the capacitor C4 and the coil L2 is in a resonance state, and the transmission wave sent to the receiving section 4 side is attenuated and is not added to the transistor Q1. I have to.

[0009]

However, in the wireless communication terminal apparatus configured as described above, automatic gain control is performed even when a high signal level signal is input to the receiving section 4. Then, the control voltage VAGC applied to the base of the transistor Q1 lowers the amplification factor of the transistor Q1 and suppresses the fluctuation of its output level, but the intermodulation distortion is caused by the large level input signal at this time. However, there is a problem that stable reception output cannot be obtained.

The present invention has been made in view of the above circumstances, and provides a wireless communication terminal apparatus capable of obtaining a stable reception output without causing intermodulation distortion even when a large signal level input is given. The purpose is to provide.

[0011]

SUMMARY OF THE INVENTION The present invention is a wireless communication terminal device in which a transmitting section for transmitting a signal and a receiving section for receiving a signal can be selectively connected to a common antenna via an antenna switching means. The antenna switching means uses a semiconductor element having characteristics such that its internal resistance is reduced by an increase in forward current, and the semiconductor element is electrically connected,
Switching between the antennas of the transmitter and the receiver is selected by non-conduction, and the internal resistance of the semiconductor element is controlled according to the level of the input signal in the receiver to keep the input signal level to the receiver constant. To control.

[0012]

As a result, according to the present invention, the internal resistance of the semiconductor element is controlled in accordance with the input signal level of the receiving section so that the input signal level in the receiving section can be controlled to be constant. Intermodulation distortion can be suppressed even if the signal level greatly varies.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of the same embodiment. In the figure, 11 is a shared antenna, an antenna switching unit 12 is connected to this shared antenna 11, and a transmitting unit 13 and a receiving unit 14 are connected to this antenna switching unit 12.

In this case, the transmission unit 13 is the power amplification unit 13
Have one. In addition, the reception unit 14 is the high frequency amplification unit 1.
41, a reception frequency converter 142, a local oscillator 143, an intermediate frequency amplifier 144, a detector 145 and the like.
A level detector 146 for detecting the level of the received signal is connected to the intermediate frequency amplifier 144, and the output from the level detector 146 is fed back to the antenna switching unit 12 as a control voltage VAGC.

FIG. 2 shows a specific structure of the same embodiment. In the figure, the antenna switching unit 12, the power amplification unit 131 of the transmission unit 13, and the high frequency amplification unit 141 of the reception unit 14 are shown.
Only the details of the antenna switching unit 12 and the high frequency amplification unit 141 are shown in FIG.
The same reference numerals are given to the same portions as.

In the antenna switching unit 12, the coil L1,
The VAGC / CTL terminal is connected to the series circuit composed of the PIN diode D1, the coil L2, and the PIN diode D2, and the control voltage VCTL and the control voltage VAGC from the level detection unit 146 described above are applied to the VAGC / CTL terminal. , PIN diode D1 by this control voltage VAGC
, D2 to control the internal resistance of the attenuator.

In the transmitter 13, the power amplifier 131 is connected to VST.
By connecting the BY terminal and applying the control voltage VSTBY to the VSTBY terminal, the output impedance of the power amplifier 131 is set high, and it is possible to cope with the change in the resistance value of the PIN diode D1. In the receiving section 14, the amplification factor of the transistor Q1 of the high frequency amplifying section 141 is fixed.

Others are the same as those in FIG. 3, and the description thereof is omitted here. Then, in such a wireless communication terminal device, first, at the time of transmission, the antenna switching unit 12
A control voltage VCTL of a predetermined level is applied to the VAGC / CTL terminal of (VCTL (TX) shown in FIG. 4). Then, coil L1,
Since a forward current shown by a broken line A in the figure flows in a series circuit composed of the PIN diode D1, the coil L2, and the PIN diode D2, the PIN diodes D1 and D2 have internal resistances due to the forward current-internal resistance characteristic shown in FIG. It becomes smaller and becomes conductive. As a result, the transmission wave amplified by the power amplification unit 131 of the transmission unit 13 becomes the capacitor C.
2, it is sent to the antenna 11 via the PIN diode D1 and the capacitor C3 and is output to the space.

On the other hand, during reception, the control voltage VCTL of the VAGC / CTL terminal of the antenna switching section 2 is not applied (VCTL (RX) shown in FIG. 4). Then PIN
The diodes D1 and D2 have a large internal resistance due to the characteristics shown in FIG. The electric wave received from the antenna 1 in this state is given as an input signal to the transistor Q1 through the coil L2 and the capacitor C2 of the receiving section 4, amplified by the transistor Q1, and taken out as an RF output from the secondary winding side of the transformer T. Be done.

In this case, when the signal level input to the receiver 4 changes, the intermediate frequency amplifier 144 shown in FIG.
The output from the level detection unit 146 according to the fluctuation of the signal level at V is the control voltage VAGC which is V of the antenna switching unit 2.
It is given to the AGC / CTL pin. Then, the control voltage VAGC at this time controls the forward current flowing in the series circuit of the coil L1, the PIN diode D1, the coil L2, and the PIN diode D2, and the PIN diodes D1 and D2 are forward current-internal shown in FIG. The internal resistance is changed according to the resistance characteristics. As a result, the input signal applied to the transistor Q1 is controlled to be constant, so that the level of the output amplified by the transistor Q1 is maintained in a stable state and the RF output from the transformer T is stable. Obtained as.

Therefore, in this way, the PIN diodes D1 and D2 corresponding to the control voltage VAGC in the antenna switching unit 2 with respect to the fluctuation of the input signal level of the receiving unit 4.
The input signal of a constant level is always applied to the transistor Q1 of the high frequency amplifier 141 by the attenuator function of controlling the internal resistance of the
Therefore, even if a large fluctuation occurs in the input signal level of the receiving section 4, intermodulation distortion does not occur in the transistor Q1 and a stable output can be obtained.

The present invention is not limited to the above-mentioned embodiments, but can be modified and implemented as appropriate without departing from the scope of the invention.
For example, the PIN diode is used in the above-mentioned embodiments, but another semiconductor element may be used as long as it has a characteristic that the internal resistance thereof is decreased by increasing the forward current. it can.

[0023]

According to the present invention, since the internal resistance of the semiconductor element can be controlled according to the input signal level of the receiving section, the input signal level in the receiving section can be controlled to be constant.
Even if the input signal level fluctuates significantly, intermodulation distortion can be suppressed and a stable reception output can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a specific configuration of one embodiment.

FIG. 3 is a diagram showing an example of a conventional wireless communication terminal device.

FIG. 4 is a diagram showing forward current-internal resistance characteristics of a PIN diode.

[Explanation of symbols]

11 ... Antenna, 12 ... Antenna switching section, 13 ... Transmission section, 131 ... Power amplification section, 14 ... Reception section, 141 ... High frequency amplification section, 142 ... Reception frequency conversion section, 143 ... Local oscillation section, 144 ... Intermediate frequency amplification Part, 145 ... Detection part, 14
6 ... Level detector, L1, L2 ... Coil, D1, D2 ...
PIN diode, Q1 ... Transistor.

Claims (1)

[Claims] 1. A wireless communication terminal device in which a transmitting section for transmitting a signal and a receiving section for receiving a signal can be selectively connected to a common antenna via an antenna switching means, wherein the antenna switching means comprises a forward current. Of the semiconductor element having a characteristic such that its internal resistance is reduced by an increase of the, and switching between the transmitting section and the receiving section for the antenna is selected by conduction or non-conduction of the semiconductor element, and at the receiving section. A wireless communication terminal device, wherein the internal resistance of the semiconductor element is controlled according to the level of an input signal to control the input signal level to the receiving unit to be constant.