JPH11154840A - Output variable type amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge a continuous variable width and to set the output level of an enlarged variable which, even remotely by combining the continuous variable amount of an ALC amplification part and a stepwise variable attenuator inserted to an output sdie. SOLUTION: This amplifier is provided with an ALC amplification part 1 capable of inputting high frequency signals, suppressing input level fluctuations and concurrently variably setting the output level, a variable attenuator 2 for inputting the output signals of the ALC amplification part 1 and supplying attenuation stepwise and an output control circuit 3 for inputting output control signals 101 and controlling an ALC control circuit 13 and a low reflection type variable attenuator 2, so as to turn the output level of the high frequency signals of an output terminal 2 into specified output level. The output control circuit 3 continuously varies the level variable amount to the sum of the continuous variable amount of the ALC control circuit 13 and the step variable amount of the variable attenuator 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable output amplifier, and more particularly to a variable output amplifier which receives a high frequency signal in a radio frequency band.
The present invention relates to a variable output amplifier that can set an output level arbitrarily simultaneously with an LC function.

[0002]

2. Description of the Related Art Conventionally, this type of variable output amplifier is used as a receiving amplifier for a radio frequency signal, and can variably set the output level within a certain range while suppressing the fluctuation of the input level. . For example, the configuration shown in FIG. 3 is generally known. FIG. 3 is a block diagram showing a conventional example.

In FIG. 3, the present amplifier inputs an RF signal to an input terminal 11, automatically suppresses fluctuations in the input level, and simultaneously variably sets the output level within a certain range. It comprises a fixed attenuator 5 for attenuating the output signal of the unit 1 to a required level, an isolator 4 for blocking a reflected wave from the output side, and an output terminal 10 for outputting a level-adjusted output signal.

The ALC amplifier 1 includes an amplifier 11a in the preceding stage and an A
A PIN diode 14 used as a variable resistance element in the LC section, amplifiers 11b and 11c in an intermediate stage and an output stage,
A drive current is supplied to a detector 12 for detecting an output level and a PIN diode 14 through a coil 15 so that the detector 12
And an ALC control circuit 13 that varies the drive current of the PIN diode 14 in accordance with the detection signal and controls the output level to be constant with respect to the fluctuation of the input level. In addition, AL
The C control circuit 13 has a function of making the output level constant with respect to the above-mentioned fluctuation of the input level, and also manually or an output control signal of a reference voltage of a comparison circuit (not shown) for comparing and extending the detection signal inputted from the detector 12. The ALC amplifier 1 has a function of variably setting the output level of the ALC amplifier 1 by varying the output control signal applied to the terminal 1.

[0005] The operation of this amplifier is to convert the high-frequency signal input to the input terminal 11 into each of the amplifiers 11a to 11c of the ALC amplifier 1.
, The detector 14, the ALC control circuit 1, the coil 1
5. The ALC circuit constituted by the PIN diode 14 suppresses the input level fluctuation of the high-frequency signal and keeps the output level constant. At the same time, this output level is A
The reference voltage of the LC control circuit 13 can be set to an arbitrary level manually or by a control signal from the output control terminal 13.

However, when it is desired to further lower the output level beyond this variable range, a predetermined fixed attenuator 5 is inserted and adjusted. The high-frequency signal whose level has been adjusted is output from the output terminal 12 via the isolator 4.

[0007]

As described above, in the conventional example, when adjusting the output level, if it is desired to lower the output level beyond the variable range of the output level of the ALC amplifier, a fixed attenuator is inserted on the output side. I have. This is because the lower limit of the output level variable range of the ALC amplifier is determined by the detection sensitivity and linearity of the detector, and the output level cannot be set to a low level.

That is, there is no problem if the output level is set within the variable range of the ALC amplifying section. However, if it is desired to lower the level beyond this variable range, a fixed attenuator must be inserted, which is troublesome. In addition, there is a problem that costs are high.

Further, when the output level is varied by an external output control signal, there is a problem that it is difficult to control the insertion of the fixed attenuator.

[0010]

SUMMARY OF THE INVENTION A variable output amplifier according to the present invention has an automatic level control (ALC) capable of inputting a high-frequency signal and automatically suppressing input level fluctuations and continuously changing output levels.
(troll) amplifying unit, a variable attenuator for attenuating an output signal of the ALC amplifying unit in predetermined steps,
An output level control unit for controlling the ALC amplification unit and the variable attenuator so that a level variable amount of a sum of an output level variable amount of the amplifying unit and a level variable amount of the variable attenuator can be continuously changed; Have.

[0011] The output level control section may be capable of varying the output level manually or by an external control signal.

The variable attenuator includes an input-side Wilkinson-type divider that divides an input signal into two, two PIN diodes inserted as variable resistance elements in each of the branched circuits, and each of the PIN diodes is inserted. Two strip lines respectively provided at positions shifted by λg / 4 line length of the wavelength of the high-frequency signal,
A high-frequency low-reflection variable attenuator including an output-side Wilkinson-type divider for coupling the branched circuits may be used.

Further, an output stage amplifier for compensating the attenuation of the variable attenuator and shifting the output level to a higher direction may be added to the output side of the variable attenuator.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing the output level variable amount in FIG.

In FIG. 1, a high frequency signal is supplied to an input terminal 11.
AL that automatically changes input level and simultaneously changes output level
C (Automatic Level Contro)
1) Controlling the amplifying unit 1, the low-reflection variable attenuator 2 that attenuates the high-frequency signal output from the ALC amplifying unit to a predetermined level, and outputs the ALC amplifying unit 1 and the low-reflection variable attenuator 2. An output control circuit 3 for continuously setting a variable output level of the sum of the variable output level of the ALC amplifier 1 and the variable level of the low-reflection variable attenuator 2 to arbitrarily set an output level; An isolator 4 receives an output signal of the reflection type variable attenuator 2, blocks a reflected wave from an output side load, and sends an output signal to a load side via an output terminal 11.

The ALC amplifying section 1 includes an amplifier 11a of the preceding stage and A
A PIN diode 14 as a variable resistance element for LC, amplifiers 11b and 11c at intermediate and output stages, a detector 12 for detecting an output level, and a PIN diode supplied via a coil 15 by a detection output of the detector 12 And an ALC control circuit 13 for varying the drive current and controlling the output level to be constant with respect to the change in the input level. A
The LC control circuit 13 has a function of making the output level constant with respect to the above-mentioned fluctuation of the input level, and also manually or an output control circuit 3 of a reference voltage of a comparison circuit (not shown) for comparing and extending a detection output inputted from the detector 12. And has a function of arbitrarily setting the output level of the ALC amplification unit 1 by a control signal 102 added from

The low-reflection type variable attenuator 2 includes a Wilkinson type divider 21 for branching the input signal from the ALC amplifier 1 into two parts, two PIN diodes 22 and 24 of variable resistance elements inserted in each branch circuit. , A coil 27 for blocking high-frequency components included in the drive current supplied to the PIN diodes 22 and 24, and the PIN diodes 22 and 24
, And two strip lines 25 and 26 provided at a position shifted by λg / 4 line length, and a Wilkinson-type divider 23 connecting each branch circuit.

Next, the operation will be described. Input terminal 11
The high-frequency signal input via the ALC is amplified by the ALC amplifying unit 1, but at the same time, the fluctuation of the input level is automatically suppressed and the output level becomes constant. The output level can be set to an arbitrary value manually or by the control signal 102.

That is, the input level is amplified by the amplifiers 11a to 11c. The output level is detected by a detector 12, and this DC detection output is output by an ALC control circuit 13.
Is added to Here, the detection output is compared with a predetermined reference voltage, and the difference voltage is amplified to supply a drive current to the PIN diode 14. When the output level increases and the detection output increases, the drive current of the PIN diode 14 increases,
Control is performed in a direction to lower the output level by lowering the resistance. At the same time, the above-mentioned reference voltage is manually or control signal 10
2, the drive current of the PIN diode 14 changes and the output level is set to an arbitrary value.

For example, as a general operation example, when the input level is -20 to -30 dBm and there is a fluctuation of 10 dB, the output level is 0 dBm by the ALC function and is constant with respect to the fluctuation of the input level. Level is 0
It can be varied between -10 dBm and can be set to any value during this time. As described above, the lowest output level is determined by the detection sensitivity of the detector 12, and is about -10 dBm.

The high-frequency signal output from the ALC amplifier 1 is input to a low-reflection variable attenuator 2, where it undergoes a step-like variable attenuation. That is, the drive current 103 is supplied from the output control circuit 3 to the PIN diodes 22 and 24 via the coil 27. When the drive current 103 changes, the resistance of the PIN diodes 22 and 24 changes and passes. Changes the amount of attenuation for high frequency signals. At this time, a reflected wave to the input side is generated due to impedance mismatch due to a change in resistance of the PIN diodes 22 and 24, but the reflected wave is canceled to the input side by the Wilkinson type dividers 21 and 23 and the strap lines 25 and 26. The generation of reflected waves is reduced. This reflected wave is A
This adversely affects the detection unit 12 of the LC amplification unit 1.

Since the drive current from the output control circuit 3 changes stepwise, for example, the variable attenuator 0 dB, 1
Variable in three steps of 0 dB and 20 dB. The high-frequency signal attenuated by the low-reflection variable attenuator 2 is transmitted from the output terminal 12 to the output load through the isolator 4 that suppresses reflection from the output load side.

A control signal 101 for specifying the output level of the high-frequency signal transmitted from the output terminal 12 is input to the output control signal terminal 13, and the output control circuit 3
01, the control signal 102 to the ALC control circuit 13 and the drive current 103 to the low-reflection variable attenuator 2 are determined so that the output level becomes the designated output level.

For example, as shown in FIG. 2, the level variable amount of the ALC control circuit 13 is continuously variable at 10 dB, and the level variable amount of the low reflection type variable attenuator 2 is set at 0, 10, 2 in a stepwise manner.
In the case of 0 dB, the output control circuit 3 controls the control signal 102 and the driving current 103 in combination, and sums the two, that is,
A variable level that continuously varies from 0 to 30 dB is realized.

The output level at the output terminal 12 is 0 to -30 dBm when the maximum level is 0 dB.
However, an amplifier is added to the output side of the low-reflection type variable attenuator 2 to increase the output level from +10 to -2, for example.
The level variable width may be shifted to 0 dBm. Note that the output control circuit 3 can also manually specify the output level without depending on the control signal 103.

[0026]

As described above, in the variable output amplifier of the present invention, a low reflection type variable attenuator is added to the output side of the ALC amplifier, and the output level of the variable output amplifier is controlled by controlling both level variable sections simultaneously. Since the amount is increased, the output level can be easily adjusted, the adjustment work can be reduced, and the cost can be reduced. Further, since the enlarged output level variable amount can be controlled also by an external control signal, there is an effect that a wide range of output level can be set remotely.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a variable output amplifier of the present invention.

FIG. 2 is a characteristic diagram showing a level variable amount in FIG.

FIG. 3 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ALC amplifier 2 Low reflection type variable attenuator 3 Output control circuit 4 Isolator 11a-c amplifier 12 Detector 13 ALC control circuit 14 PIN diode 15 Coil 21, 23 Wilkinson type divider 22, 24 PIN diode 25, 26 Strip line 27 coil

Claims (4)

[Claims] 1. An ALC (Automatic Level) capable of inputting a high-frequency signal and automatically suppressing input level fluctuations and continuously changing output levels at the same time.
(Control) amplifier, a variable attenuator that attenuates the output signal of the ALC amplifier in a predetermined step, and a variable level of a sum of a variable output level of the ALC amplifier and a variable level of the variable attenuator. A variable output amplifier comprising: an output level control unit that controls the ALC amplification unit and the variable attenuator so that the amount can be continuously varied. 2. The variable output amplifier according to claim 1, wherein said output level control section is capable of changing an output level manually or by an external control signal. 3. The variable attenuator includes an input-side Wilkinson divider that divides an input signal into two, and two PIs inserted as variable resistance elements in each of the branched circuits.
An N-diode, two strip lines provided at positions where the PIN diodes are inserted and shifted by λg / 4 line length of the wavelength of the high-frequency signal, and an output-side Wilkinson-type divider for coupling a branched circuit. 3. The variable output amplifier according to claim 1, wherein the variable output amplifier is a high-frequency low-reflection variable attenuator. 4. An output stage amplifying unit for compensating an amount of attenuation by the variable attenuator and shifting an output level to a higher direction on an output side of the variable attenuator.
4. The variable output amplifier according to 2 or 3.