JP2000349662A - Radio communication unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a radio communication unit where spurious radiation at application of power is prevented. SOLUTION: The radio communication unit is provided with a VCO 1 that acts like a carrier oscillator in the case of transmission and acts like a 1st heterodyne local oscillator in the case of reception. A control circuit 9 controls a mixer 8 and a buffer amplifier 4 to be inactive for a period until the oscillation of the VCO 1 is stable at application of power via switch circuits 10, 11 and controls the mixer 8 and the buffer amplifier 4 to be active after the oscillation of the VCO 1 is made stable, then it is prevented that an output from the voltage control oscillator at the application of power is leaked from the mixer 8 toward an antenna side via a reception front end 7 and the buffer amplifier 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication device,
More specifically, the present invention relates to a wireless communication device that reduces unnecessary radiation.

[0002]

2. Description of the Related Art As shown in FIG. 5, in a conventional radio communication apparatus having a super heterodyne receiving side, a structure near an antenna of a transmitting / receiving section is a modulation signal supplied to an audio processor 3 via a switch circuit 2 at the time of transmission. A voltage-controlled oscillator (hereinafter, referred to as V) used as a local oscillator of the first superheterodyne in which the modulated signal is cut off by the switch circuits 2 and 3 during reception and the modulated signal is cut off by the switch circuits 2 and 3 during reception.
The oscillation output from 1) is output from the buffer amplifier 4
The signal is amplified by the transmission amplifier circuit 5 and transmitted to the antenna via the low-pass filter 6, and the signal received by the antenna is guided to the reception front end 7 via the low-pass filter 6, and from the reception front end 7. Is mixed in the mixer 8 with the output from the VCO 1 amplified by the buffer amplifier 4 to obtain a first intermediate frequency signal.

In the above-described wireless communication device, when the power supply voltage is applied to the wireless communication device, the power supply voltage is applied to the VCO 1, the audio processor 3, the buffer amplifier 4, the reception front end 7, and the mixer 8. When the power supply voltage is turned on, the wireless communication device rises in the reception state, and when switched to the transmission state, the power supply voltage is applied to the switch circuit 2 and the transmission amplification circuit 5.

[0004]

However, during the period from when the power supply voltage is turned on until the power supply enters a steady state, each circuit is in an unstable state, and the leakage of the local oscillation output from the antenna may increase. There is a point.

[0005] The unstable period is a period until the power supply voltage supplied to each circuit when the power supply voltage is turned on is stabilized.
This is a period until the oscillation of the VCO 1 is stabilized and a period until the band of the band-pass filter in the reception front end 7 is stabilized. Usually, the reception front end 7 is provided with a band-pass filter having a fixed pass bandwidth in order to prevent interference of signals from outside the reception frequency band. In some cases, the bandwidth of this bandpass filter is set by voltage.

The leakage of the local transmission output from the antenna is shown in FIG.
As shown by a dashed line, the current flowing backward from the reception front end 7 via the transmission amplification circuit 5 and the mixer 8 is dominant.

The frequency spectrum of the oscillation output when the power supply voltage is applied to the VCO 1 will be described with reference to FIG.
As shown in (a), oscillation at a certain frequency is performed from the time when the power supply voltage is applied, and the required local oscillation frequency α is sequentially reached. On the other hand, the pass band width of the band-pass filter in the reception front end 7 is as shown in FIG. 6B, and when the local oscillation frequency rises, the VCO 1
As shown in FIG. 6C, a part of the oscillation frequency of the (local oscillator) is in the pass band of the band-pass filter in the reception front end 7, and this leaks from the antenna. These also occur when the power supply voltage is cut off.

An object of the present invention is to provide a radio communication device in which unnecessary radiation is prevented when a power supply voltage is applied.

[0009]

SUMMARY OF THE INVENTION A radio communication apparatus according to the present invention includes a voltage controlled oscillator which operates as a carrier oscillator during transmission and operates as a local oscillator of a first heterodyne during reception. First switch means for selectively controlling the non-operation / operation of the mixer on the unit side, and second control means for selectively controlling the non-operation / operation of the buffer amplifier for guiding the oscillation output of the voltage controlled oscillator to the antenna side.
And the first and second switch means, the mixer and the buffer amplifier are made inoperative until the oscillation of the voltage controlled oscillator is stabilized when the power is turned on, and after the oscillation of the voltage controlled oscillator is stabilized, the mixer and Control means for activating the buffer amplifier.

According to the radio communication device of the present invention, in a radio communication device provided with a voltage-controlled oscillator that operates as a carrier oscillator during transmission and operates as a local oscillator of the first heterodyne during reception, the control means controls the first radio communication device. And the mixer and the buffer amplifier are controlled to be in an inoperative state until the oscillation of the voltage-controlled oscillator is stabilized when the power is turned on via the second switch means, and the mixer and the buffer amplifier are operated after the oscillation of the voltage-controlled oscillator is stabilized Since the state is controlled, the output from the voltage-controlled oscillator when the power is turned on is suppressed from leaking from the mixer to the antenna side via the reception front end and the buffer amplifier.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a radio communication device according to the present invention will be described with reference to an embodiment.

FIG. 1 is a block diagram showing a configuration of a radio communication device according to an embodiment of the present invention, and shows a configuration near a transmitting / receiving antenna of a radio communication device having a superheterodyne configuration on the receiving side.

FIG. 1 is a block diagram showing a configuration of a wireless communication device 30 having a superheterodyne configuration on the receiving side according to an embodiment of the present invention in the vicinity of an antenna of a transmission / reception unit. A voltage control which is used as a carrier oscillator for outputting a carrier signal modulated by a modulation signal supplied to the first superheterodyne and is used as a local oscillator of the first superheterodyne when the modulation signal is cut off by the switch circuits 2 and 3 during reception. An oscillation output from an oscillator (hereinafter also referred to as a VCO) 1 is amplified by a buffer amplifier 4 and then amplified by a transmission amplifier circuit 5 and sent to an antenna via a low-pass filter 6. A signal received by the antenna is The signal is guided to the reception front end 7 through the low-pass filter 6 and output from the reception front end 7. It is configured to obtain a first intermediate frequency signal by frequency mixing the output with the mixer 8 from VCO1 amplified by the buffer amplifier 4.

The wireless communication device 30 further includes a switch circuit 10 for controlling the non-operation / operation of the buffer amplifier 4 in cooperation with the buffer amplifier 4 and a non-operation / operation of the mixer 8 in cooperation with the mixer 8. A switch circuit 11 for controlling operation;
And a control circuit 9 for controlling the switch circuits 10 and 11.

The switch circuit 10 is composed of, for example, an NPN transistor, and is inserted on the ground side of the buffer amplifier 4 and is connected to the buffer amplifier 4 through the switch circuit 10.
Are selectively connected to the ground, the buffer amplifier 4 is in a state where the ground is not connected during the OFF period of the switch circuit 10 and is controlled to be in an inactive state, and the buffer amplifier 4 is connected during the ON period of the switch circuit 10. Is controlled to an operating state.

The switch circuit 11 is also formed of, for example, an NPN transistor, and is inserted into the ground side of the mixer 8 and connected to selectively ground the mixer 8 via the switch circuit 11. The mixer 8 turns off the switch circuit 11. During the period, the ground is not connected, and the switch circuit 11 is controlled to be in an inoperative state. During the ON period of the switch circuit 11, the ground is connected and controlled to be in an operation state.

The control circuit 9 is provided with a microcomputer including a shift register, and sends a signal to the wireless communication device 30 as shown in FIG.
Except for the application of the power supply voltage to the mixer 8 and the buffer amplifier 4 from the time when the power supply voltage is turned on as shown in 1), the power supply voltage is applied to other necessary circuits and the circuit is started up in the receiving state. After a predetermined best delay time t elapses, for example, after elapse of one second, until the oscillation of the circuit becomes stable, the control circuit 9 turns on the switch circuits 10 and 11 from the off state as shown in FIG. Control the state.

Therefore, the buffer amplifier 4 and the mixer 8 are controlled to be in an inactive state during the delay time t until the oscillation of the VCO 1 is stabilized, and leakage of the oscillation output from the VCO 1 when the power is turned on is reduced. This prevents radiation from the antenna when the power is turned on. After the oscillation of the VCO 1 is stabilized, the buffer amplifier 4
Then, the ground of the mixer 8 is connected, and the buffer amplifier 4 and the mixer 8 are activated. At this time, V
CO1 performs stable oscillation.

In the wireless communication device 30, the delay time t drives the switch circuits 10 and 11 by the output from the output port at a predetermined stage of the shift register of the control circuit 9. For this reason, the delay time t is adjusted by the switch circuit 10.
And 11 can be easily performed by changing the output port of the shift register that sends the drive signal to the shift register. As a result, the delay time t for each wireless communication device 30 can be easily adjusted.

Next, the operation when the power supply voltage is cut off will be described. When the power supply voltage is cut off, the output of the shift register is also turned off by the control circuit 9 as shown in FIG. 2 (b-2) at the same time as the power supply voltage cut off shown in FIG. 2 (b-1). Control is performed. Therefore, the buffer amplifier 4 and the mixer 8 become inactive at the same time as the power supply voltage is cut off, and then the operation of other circuits is stopped.
Leakage of the oscillation output of No. 1 is suppressed.

Further, as shown in FIG.
Control circuit 9 for turning on / off switch circuit 10 inside
1 and a control circuit 9 for controlling on / off of the switch circuit 11
2, the operation control of the buffer amplifier 4 and the operation control of the mixer 8 may be made independent, and the delay times may be controlled independently. Also, as shown in FIG. 3B, the output of the control circuit 9 is supplied to time constant circuits 93 and 94 having different time constants, and the output of the time constant circuit 93 controls the on / off of the switch circuit 10. The on / off control of the switch circuit 11 is controlled by the output of the constant circuit 94,
The operation control of the buffer amplifier 4 and the operation control of the mixer 8 may be made independent, and the delay times may be controlled independently.

Next, the case where the reception front end 7 is provided with a variable band-pass filter whose bandwidth is set by a voltage will be described.

FIG. 4A is a circuit diagram showing a configuration of a variable-band bandpass filter provided in the reception front end 7 and having a bandwidth set by a voltage.

This kind of variable band-pass filter provided in the reception front end 7 includes a capacitor 15,
18 and 20, coils 17 and 19, varactor diode 16 connected in series to capacitor 15, and varactor diode 21 connected in series to capacitor 20.
And the capacitor 15 and the varactor diode 1
The output voltage from the control circuit 9A is applied to the connection point with the capacitor 6 and the connection point between the capacitor 20 and the varactor diode 21 to control the bandwidth.

During the period from the time when the power supply voltage is applied to the band pass filter having the variable bandwidth to the time when the band pass filter is brought into a stable state, the pass bandwidth is changed by the sequentially increasing output voltage change from the control circuit 9A shown in FIG. It changes as shown in FIG. Also in this case, the oscillation output from the VCO 1 may leak to the antenna due to the change in the bandwidth.

Therefore, when the power supply voltage is turned on, VC
Until the oscillation of O1 is stabilized, the output voltage from the control circuit 9A is cut off, and a switch circuit (not shown) for guiding the output voltage from the control circuit 9A to the band-pass filter after the stabilization is provided at the output terminal of the control circuit 9A. Thus, leakage of the oscillation output of the VCO 1 when the power supply voltage is applied and when the power supply voltage is cut off can be reduced.

[0027]

As described above, according to the wireless communication device of the present invention, the VCO in the unstable state when the power supply voltage is applied.
Can be suppressed by a simple configuration. Also, separate power supply for each circuit of the wireless communication device,
There is no need to finely set the timing of turning on / off the power supply voltage.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a main part of a wireless communication device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining an operation of the wireless communication device according to the embodiment of the present invention;

FIG. 3 is a block diagram showing a configuration of another example of switch circuit control in the wireless communication device according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram for explaining a bandpass filter having a variable bandwidth in a reception front end.

FIG. 5 is a block diagram showing a configuration of a main part of a conventional wireless communication device.

FIG. 6 is a schematic diagram for explaining unnecessary radiation from an antenna when the wireless communication device is unstable.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 VCO 2, 10, 11 switch circuit 3 audio processor 4 buffer amplifier 5 transmission amplifier circuit 6 low-pass filter 7 reception front end 8 mixer 9, 9A, 91 and 92 control circuit 93 and 94 time constant circuit 30 wireless communication device

Claims (3)

[Claims] In a wireless communication device provided with a voltage-controlled oscillator that operates as a carrier oscillator during transmission and operates as a local oscillator of a first heterodyne during reception, a non-operation / operation of a mixer at a reception unit is selectively performed. First switch means for controlling, second switch means for selectively controlling non-operation / operation of a buffer amplifier for guiding the oscillation output of the voltage controlled oscillator to the antenna side, and controlling the first and second switch means When the power supply is turned on, the mixer and buffer amplifier are disabled until the voltage-controlled oscillator stabilizes oscillation.
Control means for activating the mixer and the buffer amplifier after the oscillation of the voltage controlled oscillator is stabilized. 2. The wireless communication device according to claim 1, wherein:
Wherein the switch means is a transistor inserted into the ground side of the mixer to selectively connect the mixer to the ground. 3. The wireless communication device according to claim 1, wherein
Wherein the switch means is a transistor inserted into the ground side of the buffer amplifier to selectively connect the buffer amplifier to the ground.