JPH07297731A - Radio transmission circuit - Google Patents

Abstract

PURPOSE:To make the size of the circuit small by controlling attenuation of a variable attenuator with a control signal so as to reduce number of components. CONSTITUTION:A detector 7' gives a signal S11 used to decrease a level of a signal S6 when the level of the transmission signal S6 is higher than a specified level and the level of the signal S6 when the level is smaller to an AGC circuit 3 to keep the signal S6 to have a specified level. An IF signal detector 22 detects an IF amplifier signal S3 being an output of the circuit 3 and provides an output of a control signal S12 of a prescribed level when the signal S3 is present and a signal S12 of 0V when absent to a variable attenuator VATT21. When the detector 22 detects the signal S3, the signal S12 used to decrease gradually the attenuation of the VATT21 is provided as an output and the signal S3 passes gradually and a mixer 4 provides an output of a high frequency signal S5 gradually getting higher and it is amplified by an RF amplifier 6 to increase the level of th signal S6. A control signal S11 being an output of a detector 7' is used to decrease the gain of the circuit 3 based on the level of the signal S6. The operation above is repeated depending on a lapse of time and the signal S6 is finally made stable to the specified level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless transmission circuit in a multiplex wireless device or the like. Transmitted radio waves must comply with the electric power and frequency specified by the Radio Law.

For this reason, in the radio transmission circuit, the transmission power including the output level of the modulator must be kept constant, so that an automatic gain control (AGC) is applied to the IF signal (intermediate frequency signal) output from the modulator. I am putting on.

The AGC has the ability to hold the IF signal at a constant level even if the IF signal fluctuates by about ± 3 dB. However, due to some reason, for example, a contact failure of a coaxial cable for transmitting the IF signal, a device failure, etc. When the presence / absence is repeated, the transmission power instantaneously increases.

There is a demand for a wireless transmission circuit capable of transmitting a signal of constant power even in such a case.

[0005]

2. Description of the Related Art FIG. 9 shows a circuit diagram of a conventional wireless transmission circuit, and the description thereof will be given. In this figure, 1 is an ODU (Out Door Unit) in which a wireless transmission circuit is housed. The ODU 1 is installed on the roof of a building or the like, and is connected to an IDU (In Door Uint) installed indoors (not shown) by a coaxial cable 2. The IDU converts a voice or the like into a signal, finally converts it into an IF signal S1, and outputs it through the coaxial cable 2.
It is to be transmitted to DU1. Maximum of 2 coaxial cables
It has a length of around 00m.

The wireless transmission circuit accommodated in ODU1 is A
GC circuit 3, mixer 4, oscillator 5, and RF (Radio F
requency) The amplifier 6, the detector 7, and the operational amplifier 8 are provided.

The AGC circuit 3 amplifies the IF signal S1 to a constant level with a gain according to the control signal S2 output from the operational amplifier 8 and outputs it. The mixer 4 mixes the local signal S4 output from the oscillator 5 and the IF amplified signal S3 output from the AGC circuit 3, converts the mixed signal into a signal S5 having an RF band frequency, and outputs the signal S5.

The RF amplifier 6 amplifies the RF signal S5 and outputs it as a transmission signal S6. The transmission signal S6 is sent to an antenna (not shown) and is transmitted as a radio wave. Detector 7
Detects and outputs the level V1 (hereinafter referred to as a detection voltage) of the transmission signal S6.

The operational amplifier 8 outputs a control signal S2 which is a differential voltage between the detection voltage V1 supplied to the positive phase input terminal "+" and the comparison voltage V2 supplied to the negative phase input terminal "-". The negative-phase input terminal "-" is connected to the output terminal via the resistor R1, and is also connected to the variable resistor R4 via the resistor R2.

The variable resistor R4 is connected to a power source for outputting a constant voltage + V via the resistor R3, and the resistor R4 is also connected.
It is grounded through 5. That is, by changing the resistance value of the variable resistor R4, the power supply voltage + V can be set to an arbitrary level and supplied to the negative phase input terminal "-" as the comparison voltage V2.

In such a configuration, the transmission signal S6
If the detected voltage V1 is higher than the comparison voltage V2, the control signal S2 for lowering the level of the transmission signal S6 is supplied to the AGC circuit 3, and if it is lower, the control signal S2 for increasing the level of the transmission signal S6 is supplied to the AGC circuit 3. By
The level of the transmission signal S6 is constant.

However, when the IF signal S1 input to the AGC circuit 3 is interrupted due to a contact failure of the coaxial cable 2 or the like, the detection voltage V1 is detected at the time of interruption.
Becomes 0V. In such a case, the control signal S2 is AGC.
The circuit 3 serves to amplify the IF signal S1 with the maximum gain. If the IF signal S1 is input in this state, the IF signal S1 is excessively amplified, and the power of the transmission signal S6 exceeds the power value specified by the Radio Law.

Therefore, in order to eliminate the drawback, FIG.
The circuit configuration shown in 0 is taken. The circuit of FIG. 10 will be described. In FIG. 10, parts corresponding to the parts shown in FIG. 9 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 10, 10 is a detector, 11 is an operational amplifier, 12 is a transistor, R6 is a resistor, and C1 is a capacitor. The detector 11 detects the presence or absence of the IF signal S1, and at the time of detecting the IF signal S1, the detection voltage of the same level as the power supply voltage + V4 supplied to the positive phase input terminal “+” of the operational amplifier 11. Output V3,
When not detected, the detection voltage V3 of 0V is output.

The operational amplifier 11 compares the detection voltage V3 with the power supply voltage + V4, and when the detection voltage V3 is the one when the IF signal S1 is detected, the control signal S8 of 0 V is applied to the transistor through the resistor R6. Output to the base end of 12,
When the detected voltage V3 is at the time of detecting the IF signal S1, the control signal S8 having a predetermined voltage value is output to the base end of the transistor 12 via the resistor R6.

When the control signal S8 having a predetermined voltage value is supplied to the base terminal of the transistor 12, the transistor 12 is turned on, and the current of the power supply that outputs the power supply voltage + V flows to the ground through the transistor 12, so that it is the reverse of the operational amplifier 8. The comparison voltage V2 applied to the phase input terminal "-" is set to 0V.

When the control signal S8 of 0 V is supplied to the base terminal of the transistor 12 in the on state, the transistor 12 is turned off. At this time, the electric charge accumulated in the capacitor C1 is gradually discharged, and the resistance of the resistor R3 is reduced. The comparison voltage V2 is gradually increased according to the time constant between the value R and the capacitance value C of the capacitor C1.

In such a configuration, the IF signal S1
Even if the voltage is not supplied to the AGC circuit 3, the comparison voltage V2 is set to 0V and the control signal S2 corresponding to the comparison voltage V2 is applied to the AGC circuit 3
Can stand by so as to amplify the IF signal S1 with the minimum gain, so that even if the IF signal S1 is suddenly input, the IF signal S1 is excessively amplified and the transmission signal S6
Will not exceed the power value stipulated by the Radio Law.

[0019]

By the way, the above-mentioned O
The volume of the DU1 tends to decrease year by year, but not only the radio transmission circuit but also the RF and IF of the reception system.
Since the signal processing circuit, alarm control circuit, and power supply circuit are also built-in, the printed circuit board is in a high-density mounting state.

However, in the radio transmission circuit as shown in FIG. 10, when the coaxial cable 2 for supplying the IF signal S1 reaches 200 m, the cable loss is 40 d.
B or more, and in this case, the AGC circuit 3 requires a few amplifiers and a variable attenuator to obtain a desired gain. Furthermore, in order to transfer a sufficient level to the detector 10 that detects the presence or absence of the IF signal S1, two to three amplifiers are required in the preceding stage of the detector 10.

Therefore, there is a problem that the ODU1 becomes large because the radio transmission circuit itself becomes large as the number of parts increases. Alternatively, if the miniaturization of the ODU 1 is maintained for higher-density mounting, there is a problem that it becomes difficult to arrange the components of the printed circuit board and take a ground.

The present invention has been made in view of the above points, and an object thereof is to provide a radio transmission circuit which can be miniaturized by reducing the number of parts as much as possible.

[0023]

FIG. 1 shows a principle diagram of a wireless transmission circuit of the present invention. In this wireless transmission circuit, the input intermediate frequency signal S1 is amplified by the automatic gain control means 3 to a predetermined level, and the amplified signal S3 and the high frequency local signal S4 output from the oscillation means 5 are mixed by the mixing means 4. By doing so, the high frequency signal S5 is generated, the generated high frequency signal S5 is amplified to a level determined by the high frequency amplifying means 6, and if the level of the amplified high frequency signal S6 is higher than a predetermined level, it is low and high. In such a configuration that the first control signal S11 for controlling the gain of the automatic gain control means 3 is outputted from the detection means 7 ', the amplified signal S3 outputted from the automatic gain control means 3 is attenuated. The attenuating means 21 for outputting to the mixing means 4 and the attenuating means 21 are controlled to have the maximum attenuation amount that interrupts the amplified signal S3 when the absence of the amplified signal S3 is detected. Attenuation upon detection of the is constructed by progressively provided a signal detection unit 22 for outputting a second control signal S12 for controlling the damping means 21 to decrease.

[0024]

According to the present invention described above, when the intermediate frequency signal S1 is not supplied, there is no amplified high frequency signal S6, so that the automatic gain control means 3 has the maximum gain. At this time, the signal detecting means 22 detects the absence of the signal S3, and controls the attenuation amount of the attenuating means 21 to be the maximum attenuation amount by the second control signal S12.

If the intermediate frequency signal S1 is supplied here, the automatic gain control means 3 amplifies the intermediate frequency signal S1 with a maximum gain, but the attenuating means 21 has the maximum attenuation amount, so that the intermediate frequency signal S1 is cut off. It That is, since the high frequency signal S5 is not output from the mixing means 4 when the intermediate frequency signal S1 is supplied, the amplified high frequency signal S6 is also not output.

When the amplified signal S3 is detected by the signal detection means 22, the attenuation amount of the attenuation means 21 is gradually decreased.
Since the control signal S12 is output and the amplified signal S3 gradually passes therethrough, the mixing means 4 outputs the gradually increasing high-frequency signal S5, and the high-frequency signal S6 is amplified by the high-frequency amplification means 6, whereby The amplified high frequency signal S6 gradually increases.

The gain of the automatic gain control means 3 is gradually reduced by the first control signal S11 output from the detection means 7'according to the level of the signal S6. By repeating such an operation as time passes, the amplified high frequency signal S6 is finally stabilized at a predetermined level.

In the above operation, even if the intermediate frequency signal S1 is amplified by the maximum gain of the automatic gain control means 3, the finally output amplified high frequency signal S6 does not exceed the predetermined level.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram of the wireless transmission circuit according to the first embodiment of the present invention. In this figure, parts corresponding to the parts of the conventional example shown in FIG. 10 are designated by the same reference numerals, and description thereof will be omitted.

Characteristic elements in the radio transmission circuit shown in FIG. 2 are an IF signal detector 22 and a VATT (variable attenuator) 21.
Is. The detector 7'detects the transmission signal S6,
The AGC circuit 3 outputs the control signal S11 according to the level, and the AGC circuit 3 amplifies the IF signal S1 to a constant level with a gain according to the control signal S11 and outputs the IF signal S1.

That is, if the level of the transmission signal S6 is larger than the predetermined level, the control signal S11 for lowering the level of the transmission signal S6 is supplied to the AGC circuit 3, and if it is smaller, the control signal S11 for raising the level of the transmission signal S6 is supplied. AGC
By being supplied to the circuit 3, the level of the transmission signal S6 is kept constant and does not exceed the electric power value defined by the Radio Law.

When the IF signal S1 input to the AGC circuit 3 is cut off, the control signal S11 serves to cause the AGC circuit 3 to amplify the IF signal S1 with the maximum gain. That is, when the IF signal S1 is cut off, the AGC circuit 3 is in a state of amplifying the IF signal S1 with the maximum gain.

The IF signal detector 22 detects the presence or absence of the IF amplified signal S3 output from the AGC circuit 3, outputs a control signal S12 of a predetermined level to the VATT 21 when it is present, and 0V control when it is not present. Signal S12 to VATT21
The data is output to the computer, and its internal configuration is as shown in FIG.

In FIG. 3, 31 is a detector, 32 is an amplifier, and 33 is an operational amplifier. The detector 31 is a resistor R
7, R8, R9, capacitors C2, C3, and diodes 34, 35. The connection configuration of these elements is such that the output terminal of the IF amplified signal S3 of the AGC circuit 3 has a resistor R7 and a capacitor C connected in series with each other.
The anode end of the diode 34 is connected via 2, and between the capacitor C2 and the anode end of the diode 34,
The cathode end of the diode 35 whose anode end is grounded is connected, and the cathode end of the diode 34 is connected to the input end of the amplifier 32 via the resistor R9.
The other end of the capacitor C3 whose one end is grounded is connected to the cathode end of the resistor R9, and the other end of the resistor R8 whose one end is grounded is connected.

The detector 31 performs positive detection, outputs a detection voltage V5 of 0V when the level of the IF amplified signal S3 is 0V, and outputs a predetermined voltage when the level of the IF amplified signal S3 is a predetermined value or more. The level detection voltage V5 is output.
The amplifier 32 amplifies and outputs the detected voltage V5.

The operational amplifier 33 compares the amplified voltage V6 output from the amplifier 32 with the comparison voltage V7 of a predetermined level. If the amplified voltage V6 is larger than the comparison voltage V7, the level of the control signal S12 is VATT21 which will be described later. When the amplified voltage V6 is smaller than the comparison voltage V7, the voltage V8 that minimizes the amount of attenuation is output, and the voltage V of 0V is output.
8 is output.

When the voltage V8 is at a predetermined level that minimizes the amount of attenuation of VATT21, the charge corresponding to the voltage V8 is charged in the capacitor C4, and the control signal S12 having a voltage value determined by this charge is output.

When the voltage V8 is 0V, the electric charge charged in the capacitor C4 is discharged by the time constant τ1 determined by the resistance value R of the resistor R10 and the capacitance value C of the capacitor C4, and this discharge is gradually performed. The control signal S12 having a voltage value that changes to is output.

The VATT 21 shown in FIG. 2 has the minimum attenuation when the control signal S12 of the level output when the IF signal detector 22 detects the IF amplified signal S3 of the normal level is supplied. IF signal detector 22 is I
When the 0V control signal S12 output when the absence of the F amplified signal S3 is detected is supplied, the attenuation amount becomes maximum, and the internal configuration is as shown in FIG.

The VATT 21 shown in FIG. 3 is a capacitor C.
5, C6, resistors R11 and R12, and diode 37
Is configured. The connection configuration of these elements is A
The anode end of the diode 37 is connected to the output end of the IF amplified signal S3 of the GC circuit 3 via the capacitor C5,
The other end of the resistor R11 whose control signal S12 is supplied to one end is connected between the capacitor C2 and the anode end of the diode 37, and the cathode end of the diode 37 is connected to one input end of the mixer 4 via the capacitor C6. The other end of a resistor R12 whose one end is grounded is connected between the cathode end of the diode 37 and the capacitor C6.

Further, the operation time constant of the AGC circuit 3 operated by the control signal S11 output from the detector 7'is set to τ2.
Then, the time constant τ2 is set to be larger than the time constant τ1 for operating the VATT 21 described above.

That is, the operation of the AGC circuit 3 is VATT2.
It is faster than the operation of 1. This is because when the operation of VATT21 is faster than the operation of AGC circuit 3, VATT21
This is because the amount of attenuation of 1 decreases too fast and the IF amplified signal S3 of excessive power passes to the mixer 4.

The operation of the radio transmission circuit having such a configuration will be described with reference to the time chart of FIG. At time t0 shown in FIG. 5, it is assumed that the IF signal S1 is in the OFF state (no signal). In this case, the gain of the AGC circuit 3 is maximum (MAX), and the IF amplified signal S3 output from the AGC circuit 3 is 0V.

Since the IF amplified signal S3 is 0V, the IF signal detector 22 detects the absence of a signal and outputs the control signal S12 which makes the attenuation amount of the VATT 21 maximum (MAX). In addition, there is no IF amplified signal S3 and VATT
Since 21 is in a state of not passing a signal, the RF signal S5 is not output from the mixer 4 and the transmission signal S6 output from the RF amplifier 6 does not appear.

At time t1, when the IF signal S1 is turned on (state with signal), the AGC circuit 3 is operating with the maximum gain, and the level of the IF amplified signal S3 becomes maximum at that moment. At this time, the attenuation amount of the VATT 21 is maximum, so that the IF amplified signal S3 does not pass to the mixer 4 and the transmission signal S6 does not appear.

When the level of the IF amplified signal S3 becomes maximum, the IF signal detector 22 detects the presence of the signal, and the output voltage V8 of the operational amplifier 33 shown in FIG.
Becomes

When the voltage V8 becomes 0V, the capacitor C4
The electric charge charged in the VATT 21 is gradually discharged, whereby the level of the control signal S12 is gradually lowered, and accordingly, the attenuation amount of the VATT 21 is also gradually lowered as shown between the times t1 and t3.

On the other hand, as shown between times t1 and t2, the IF
Immediately after the signal S1 is input, the IF amplified signal S3 is in a ringing state. At this time, since the attenuation amount of the VATT21 is still large, the IF amplified signal S3 is VATT21.
There is only a slight passage through. Due to this passage, the level of the transmission signal S6 also slightly rises. That is, the ringing is masked by the VATT 21.

When the level of the transmission signal S6 rises,
This is detected by the detector 7 ', and the control signal S11 corresponding to this detection gradually decreases the gain of the AGC circuit 3. After that, as shown between times t2 and t3, the gain of the AGC circuit 3, the level of the IF amplified signal S3, and the attenuation amount of the VATT 21 gradually decrease, and thereby the level of the transmission signal S6 also gradually increases.

Then, as shown after time t3, when a predetermined time elapses, the gain becomes the standard value, the level of the IF amplified signal S3 becomes the standard value, the attenuation amount of the VATT 21 becomes the minimum value, and the level of the transmission signal S6 becomes the standard value. Stabilize.

According to the first embodiment described above, even when the IF signal S1 suddenly changes from the unsupplied state to the input state, the IF signal S1 is excessively amplified and the power of the transmission signal S6 is determined by the Radio Law. It will not exceed the current power value.

Further, as compared with the conventional circuit shown in FIG. 10 which performs such control, the number of constituent parts can be reduced. Therefore, even when it is formed on a printed circuit board, the arrangement of parts and the method of grounding. Does not become difficult as in the past, and the entire circuit can be downsized.

Next, a second embodiment will be described with reference to FIG. However, in the second embodiment shown in FIG. 6, parts corresponding to the respective parts of the first embodiment shown in FIG.
The description is omitted.

The second embodiment shown in FIG. 6 corresponds to the first embodiment shown in FIG.
The difference from the embodiment is that the VATT 21 is connected between the oscillator 5 and the mixer 4. That is, the IF signal S
Even if the IF amplified signal S3 in the ringing state is supplied to the mixer 4 when 1 goes from the ON state to the OFF state, the local signal S4 of the oscillator 5 is masked by the VATT 21,
The output of the masked signal S14 to the mixer 4 prevents the mixer 4 from outputting the RF signal S5.

In this way, the level of the transmission signal S6 gradually rises and stabilizes at the standard value as described with reference to FIG. Also in the second embodiment having such a configuration, the same effect as the first embodiment can be obtained.

Next, a third embodiment will be described with reference to FIG. However, in the third embodiment shown in FIG. 7, parts corresponding to the respective parts of the second embodiment shown in FIG.
The description is omitted.

The feature of the third embodiment shown in FIG. 7 is that a power supply control circuit 40 is provided, the power supply current of the oscillator 5 is controlled, and the level of the local signal S4 output from the oscillator 5 is controlled. is there.

That is, in the second embodiment shown in FIG. 6, the level of the local signal S4 output from the oscillator 5 is set to VATT.
21. However, in the third embodiment shown in FIG. 7, the local signal S is controlled by controlling the power supply current of the oscillator 5.
4 levels are controlled.

The power supply control circuit 40 includes the IF signal detector 22.
When the control signal S12 for detecting no signal is supplied, the control signal S for setting the power supply current of the oscillator 5 to 0A
16 is output and the control signal S when the presence of a signal is detected
When 12 is supplied, the control signal S16 having the power supply current of the oscillator 5 as a standard value is output.

In such a configuration, the IF signal S1
Even if the IF amplified signal S3 in the ringing state is supplied to the mixer 4 when the signal is switched from the ON state to the OFF state, the power supply current of the oscillator 5 is minimized and the local signal S
Since the level of 4 is the minimum, the mixer 4 does not output the RF signal S5 having a high level.

In this way, the level of the transmission signal S6 gradually rises and stabilizes at the standard value as described with reference to FIG. Even in such a third embodiment, the same effect as the second embodiment can be obtained.

Next, a fourth embodiment will be described with reference to FIG. However, in the fourth embodiment shown in FIG. 8, parts corresponding to the respective parts of the third embodiment shown in FIG.
The description is omitted.

The feature of the fourth embodiment shown in FIG. 8 is that the power supply control circuit 42 is provided and the power supply current of the RF amplifier 6 is controlled to control the power supply current of the RF amplifier 6, and the transmission signal S6 is controlled by this control. The point is to control the level of.

That is, in the third embodiment shown in FIG. 7, the power supply current of the oscillator 5 is controlled, but in the fourth embodiment shown in FIG. 8, transmission is performed by controlling the power supply current of the RF amplifier 6. The level of the signal S6 is controlled.

The power supply control circuit 42 uses the IF signal detector 22.
Outputs the control signal S18 for setting the power supply current of the RF amplifier 6 to 0 A when the control signal S12 when the signal is detected is supplied, and the control signal S12 when the signal is detected is supplied. In this case, the control signal S18 having the power supply current of the RF amplifier 6 as a standard value is output.

In such a configuration, the IF signal S1
If the ringing state IF amplified signal S3 is supplied to the mixer 4 and the ringing state RF signal S5 is input to the RF amplifier 6 when
Since the RF amplifier 6 is hardly amplified because the power supply current of the F amplifier 6 is extremely small, the level of the transmission signal S6 does not increase. In this way, the transmission signal S
The level of 6 gradually increases and stabilizes at the standard value as described with reference to FIG. Even in such a fourth embodiment, the same effect as the third embodiment can be obtained.

Although the AGC circuit 3 is used in the circuits of the first to fourth embodiments described above, an ALC circuit (automatic level control circuit) for controlling the level of the IF signal S1 is used instead. Even if it is a thing, it becomes possible to obtain the same effect as each Example by constructing similarly.

[0068]

As described above, according to the present invention,
Since the number of constituent parts can be reduced, it is possible to reduce the size of the entire circuit without the difficulty of arranging the parts and grounding as in the past, even when configuring them on a printed circuit board. There is.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a block configuration diagram of a wireless transmission circuit according to a first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of an IF signal detector.

FIG. 4 is a circuit diagram showing a configuration of VATT.

5 is a time chart for explaining the operation of the wireless transmission circuit shown in FIG.

FIG. 6 is a block configuration diagram of a wireless transmission circuit according to a second embodiment of the present invention.

FIG. 7 is a block configuration diagram of a wireless transmission circuit according to a third embodiment of the present invention.

FIG. 8 is a block configuration diagram of a wireless transmission circuit according to a fourth embodiment of the present invention.

FIG. 9 is a block configuration diagram of a wireless transmission circuit according to a conventional example.

FIG. 10 is a block configuration diagram of a wireless transmission circuit according to another conventional example.

[Explanation of symbols]

 3 Automatic Gain Control Means 4 Mixing Means 5 Oscillating Means 6 High Frequency Amplifying Means 7'Detecting Means 21 Attenuating Means 22 Signal Detecting Means S1 Intermediate Frequency Signals S3 Amplifying Signals S4 Local Signals S5 High Frequency Signals S6 Amplifying High Frequency Signals S11 First Control Signal S12 No. 1 2 control signals

Claims (5)

[Claims] 1. The input intermediate frequency signal (S1) is amplified to a predetermined level by an automatic gain control means (3), and the amplified signal is obtained.
The high frequency signal (S5) is generated by mixing (S3) and the high frequency local signal (S4) output from the oscillating means (5) by the mixing means (4), and the generated high frequency signal (S5) Is amplified to a level determined by the high frequency amplification means (6), and if the level of the amplified high frequency signal (S6) is higher than a predetermined level, it is low, and if it is low, the gain of the automatic gain control means (3) is increased. Detecting means (7 ') for detecting the first control signal (S11) for controlling
In the wireless transmission circuit for outputting from, the mixing means is connected between the automatic gain control means (3) and the mixing means (4) to attenuate the amplified signal (S3).
An attenuator (21) for outputting to (4), and controlling the attenuator (21) to a maximum attenuation amount that blocks the amplified signal (S3) when the absence of the amplified signal (S3) is detected, And a signal detecting means (22) for outputting a second control signal (S12) for controlling the attenuating means (21) so that the attenuating amount gradually decreases when the presence is detected. Radio transmitter circuit. 2. The mixing means instead of the attenuation means (21) between the automatic gain control means (3) and the mixing means (4).
It is connected between (4) and the oscillating means (5), and when the signal detecting means (22) detects the absence of the amplified signal (S3), the local control is performed by the second control signal (S12). The attenuation means (21) is controlled to the maximum attenuation amount that blocks the signal (S4), and when the presence of the amplified signal (S3) is detected, the attenuation means is gradually decreased. 21) The wireless transmission circuit according to claim 1, wherein the wireless transmission circuit is controlled. 3. The radio transmission circuit according to claim 1, wherein the operation time constant of the attenuating means (21) is made larger than the operation time constant of the automatic gain control means (3). 4. The input intermediate frequency signal (S1) is amplified to a predetermined level by an automatic gain control means (3), and this amplified signal is obtained.
The high frequency signal (S5) is generated by mixing (S3) and the high frequency local signal (S4) output from the oscillating means (5) by the mixing means (4), and the generated high frequency signal (S5) Is amplified to a level determined by the high frequency amplification means (6), and if the level of the amplified high frequency signal (S6) is higher than a predetermined level, it is low, and if it is low, the gain of the automatic gain control means (3) is increased. Detecting means (7 ') for detecting the first control signal (S11) for controlling
In the wireless transmission circuit which outputs from the power supply control means (40) for controlling the power supply current of the oscillating means (5) by the third control signal (S16) and the absence of the amplified signal (S3), Third control signal
(S16) sets the power supply control means so that the power supply current becomes 0A.
Signal detection for controlling the (40) and outputting a fourth control signal (S12) for controlling the power supply control means (40) so that the power supply current gradually increases to a predetermined value when the existence is detected. A wireless transmission circuit comprising: means (22). 5. The input intermediate frequency signal (S1) is amplified to a predetermined level by an automatic gain control means (3), and the amplified signal is obtained.
The high frequency signal (S5) is generated by mixing (S3) and the high frequency local signal (S4) output from the oscillating means (5) by the mixing means (4), and the generated high frequency signal (S5) Is amplified to a level determined by the high frequency amplification means (6), and if the level of the amplified high frequency signal (S6) is higher than a predetermined level, it is low, and if it is low, the gain of the automatic gain control means (3) is increased. Detecting means (7 ') for detecting the first control signal (S11) for controlling
In the wireless transmission circuit for outputting from the high frequency amplifying means (6), the power supply current is supplied to the fifth control signal (S1
8) a power supply control means (42) for controlling by the fourth control signal when the absence of the amplified signal (S3) is detected.
(S18) controls the power supply so that the power supply current becomes 0A.
Signal detection for controlling the (42) and outputting a sixth control signal (S12) for controlling the power supply control means (42) so that the power supply current gradually increases to a predetermined value when the presence is detected. A wireless transmission circuit comprising: means (22).