JP2001024457A - Automatic gain controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evade the occurrence of any distortion or noise in an output signal when any of parallel amplifiers breaks down in an automatic gain controller into which parallel amplifiers are integrated due to the increase of the input signal levels of the other amplifiers or the amplification in a non-linear region. SOLUTION: A number of failure detecting circuit 11 detects a number X of the failure of parallel amplifiers 41 to 4N, and a reference voltage generating circuit 12 supplies preliminarily set reference voltages Vm0 to VmN to a control signal generating circuit 9 based on the detected number X. Therefore, even when the output is largely lowered due to the failure of the parallel amplifiers 41 to 4N, the control signal generating circuit 9 receives the reference voltages Vm0 to VmN whose reference level is different corresponding to this, and derives a control signal S. Thus, the sharp increase of the input signal level in the normal parallel amplifier can be reduced, the occurrence of any distortion or noise can be evaded, and the output signal whose characteristics are satisfactory can be successively transmitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an automatic gain control device suitable for use in a high-power high-frequency output amplification stage in a television transmitter or the like.

[0002]

2. Description of the Related Art In the final stage of a television transmitter or the like, it is often difficult to obtain a desired large output with an amplifier incorporating a single semiconductor element. Therefore, in such a case, the distributed input high-frequency signals are usually amplified by parallel amplifiers, and a desired output power is obtained by combining the amplified outputs. At that time, the characteristics of the semiconductor element incorporated in the parallel amplifier may change depending on the ambient temperature. Therefore, the parallel amplifier is incorporated in the automatic gain control system so that a stable output is always obtained. .

FIG. 5 is a circuit diagram showing a conventional automatic gain control device incorporating a parallel amplifier. A high-frequency signal input to an input terminal 1 is subjected to level adjustment by a variable attenuator 2 and then distributed. Is supplied to the vessel 3. Multiple (N) in distributor 3
Are amplified by parallel amplifiers 41 to 4N composed of a plurality of (N) units, and the amplified high-frequency signals are combined by a combiner 5 and output via a power divider 6. Output to terminal 7.

The output signal distributed by the power distributor 6 is input to an output detection circuit 8, where it is converted into a voltage V corresponding to the output power and supplied to a control voltage generation circuit 9. Further, a reference voltage generation circuit 10 is connected to the control voltage generation circuit 9, and a reference voltage Vm set corresponding to a predetermined output is supplied.

Accordingly, the control voltage generation circuit 9 compares the predetermined reference voltage Vm with the voltage V converted and output by the output detection circuit 8, and generates a control signal S corresponding to the difference (Vm to V). Is supplied to the variable attenuator 2 to control the variable attenuator 2, so that even if the output of the parallel amplifiers 41 to 4N changes due to a change in the ambient temperature, a constant output is always derived from the output terminal 7. Feedback control is performed as described above.

Therefore, in the circuit shown in FIG. 5, the combined output when all the N parallel amplifiers 41 to 4N operate normally and the combined output when X out of the N units fail are Z. , The signal from the control voltage generation circuit 9 is a variable attenuator 2
The output Z under the condition of not controlling the following equation (1)
It is known that

Z = Y × ((N−X) / N) ² (1) For example, in the above equation (1), five (N = 5) parallel amplifiers are operated. Assuming that the unit (parallel amplifier 41, X = 1) fails, the combined output Z at that time is Z = Y ((5-1) / 5) ² = 0.64Y, which is 64% of the normal state. .

Therefore, the control voltage generation circuit 9 controls the variable attenuator 2 to reduce the amount of attenuation so that the output supplied from the variable attenuator 2 to the distributor 3 is 1 when the output is normal during normal operation.
/0.64 times, so that the input signal levels of the remaining four parallel amplifiers 42 to 45 performing normal operation increase, and a predetermined combined output Z can be obtained.

As described above, when one of the parallel amplifiers fails and a prescribed output cannot be obtained, the conventional automatic gain control device adjusts the difference signal S to a variable attenuator in order to compensate for the reduced combined output. 2, the input and output of the remaining parallel amplifiers 41 to 4N become large, so that the attenuation of the passing high-frequency signal in the variable attenuator 2 is reduced.
It was operated to obtain a predetermined combined output power.

In the automatic gain control device having the above configuration,
A variable gain amplifier is also used in place of the variable attenuator 2. The variable gain amplifier receives a control signal from the control voltage generation circuit 9 if any one of the parallel amplifiers 41 to 4N fails and the output drops, Similarly, it functions to increase the output supplied to the parallel amplifiers 41 to 4N.

[0011]

As described above, the conventional automatic gain control device incorporating the parallel amplifier has a problem in that when some of the parallel amplifiers fail and the output cannot be obtained or the output is greatly reduced. Since the control circuit compensates for this and controls the variable attenuator and the like so as to obtain a predetermined combined output power, the input signal level to the other parallel amplifiers that operate normally increases.

However, in the above-mentioned conventional automatic gain control device, when one of the parallel amplifiers fails and the input signal level to the other parallel amplifiers increases, the other parallel amplifiers often become in the normal operating region. , The amplification operation is performed by expanding to the non-linear region. As a result, each of the parallel amplifiers generates distortion, noise (noise), and the like due to non-linear distortion, and significantly degrades output signal characteristics. Therefore, some improvement has been demanded.

An object of the present invention is to provide an automatic gain control device capable of avoiding deterioration of output signal characteristics even if one of the amplifiers constituting a parallel amplifier fails.

[0014]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. In an automatic gain control device, a variable attenuator or a variable gain amplifier to which a high-frequency signal is supplied and a variable attenuator or a variable gain amplifier are provided. A divider connected to an attenuator or a variable gain amplifier, a parallel amplifier for amplifying the high-frequency signal distributed by the divider, respectively, and combining and outputting each amplified high-frequency signal connected to the parallel amplifier A synthesizer, an output detection circuit that detects the output power of the high-frequency signal synthesized and output by the synthesizer, and outputs a corresponding voltage, and a failure that is connected to the parallel amplifier and detects the number of failed amplifiers. A number detection circuit, a reference voltage generation circuit connected to the failure number detection circuit, and outputting a reference voltage of a preset level corresponding to the number of failed amplifiers; A control signal generation circuit configured to derive a difference between the reference voltage from a voltage generation circuit and the voltage derived from the output detection circuit to control the variable attenuator or the variable gain amplifier. It is characterized by the following.

As described above, the present invention has the number-of-failures detection circuit and the reference voltage generation circuit, and the control voltage generation circuit has a reference voltage value corresponding to the detected number of failed amplifiers and a voltage corresponding to the output voltage. The variable attenuator and the like are controlled by comparing the values. Therefore, even if one of the parallel amplifiers fails and the combined output greatly decreases, the variable attenuator and the like can be controlled so that the input signal to the remaining normal parallel amplifier does not increase. The parallel amplifier can continuously maintain good amplification operation in the linear region, and can derive a good high-frequency combined output without nonlinear distortion.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the automatic gain control device according to the present invention will be described below in detail with reference to FIGS. The same components as those of the conventional automatic gain control device shown in FIG. 5 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a circuit diagram showing an embodiment of an automatic gain control device according to the present invention. A high-frequency signal input to an input terminal 1 is subjected to level control by attenuation in a variable attenuator 2. , To the distributor 3.

The high frequency signals distributed to a plurality (N) by the distributor 3 are respectively amplified by the parallel amplifiers 41 to 4N and supplied to the synthesizer 7, and a part of the high frequency signals is supplied to the failure detector of the failure number detection circuit 11. 11a1 to 11aN, respectively. The output power of the parallel amplifiers 41 to 4N synthesized by the synthesizer 7 is supplied to the output terminal 7 via the power distributor 6 as in the conventional case. The output signal distributed by the power distributor 6 is also input to the output detection circuit 8 as in the related art, where it is converted into a voltage V corresponding to the output power and supplied to the control voltage generation circuit 9.

On the other hand, the number-of-failures detection circuit 11 to which the outputs of the parallel amplifiers 41 to 4N are branched and supplied is connected to the parallel amplifier 4
A plurality of fault detectors 11a1 configured to calculate and supply the number of faults of 1 to 4N to the reference voltage generation circuit 12, and to be connected to the parallel amplifiers 41 to 4N, respectively.
To 11aN and a calculation circuit 11b.

That is, first, each fault detector 1 is connected correspondingly to the parallel amplifiers 41 to 4N and branches and introduces each output.
Each of 1a1 to 11aN includes a voltage conversion / comparison circuit 11a1a and a constant voltage source 11a1b including a Zener diode or the like, as shown in FIG. The voltage conversion / comparison circuit 11a1a includes a parallel amplifier 41
Only when the output from the power supply exceeds the voltage value set in advance by the constant voltage source 11a1b, a signal of level "0" is regarded as operating normally, and conversely, when a predetermined output cannot be obtained due to a failure. By outputting the signal of level “1”, the presence or absence of the predetermined output in the parallel amplifiers 41 to 4N is detected and supplied to the calculation circuit 11b.

The calculation circuit 11b is connected to each of the failure detectors 11a1
The detection signals for the presence / absence of the predetermined output in the parallel amplifiers 41 to 4N from １１11aN are calculated, and the number X of faulty amplifiers is calculated and derived. The specific circuit configuration will be described with reference to FIG. 3 illustrates a case where three parallel amplifiers 41 to 4N (N = 3) are illustrated for the sake of explanation. Output signals from the three failure detectors 11a1 to 11a3 are input to an input circuit 11ba and a matrix. It is supplied to a calculation circuit 11b composed of a circuit 11bb and a logic operation circuit 11bc.

As described above, in this embodiment, the parallel amplifiers 41 to 41 are connected to each input line of the input circuit 11ba.
43 is a normal operation, a signal of each level “0” is supplied. If any of the amplifiers fails, a signal of a level “1” is supplied to the corresponding input line. Each signal is supplied to the calculation circuit 11b by a combination configuration of the input signal lines as illustrated. The calculation circuit 11b is composed of a logical operation circuit composed of a logical sum and a logical product, and the parallel amplifiers 41, 42, 4
Output signals (level "1") corresponding to the number of failed units including zero (0) units of 3 are output to corresponding output terminals 11b.
The signals are supplied to the switch 12a of the reference voltage generation circuit 12 shown in FIG. 1 via 0, 11b1, 11b2, and 12b3.

That is, the output terminal 11 of the calculation circuit 11b
From b0 to 11b3, the parallel amplifiers 41 to 43 are respectively provided.
The output signal of signal level "1" of one of the zero (0) faults 11b0, one fault 11b1, two faults 11b2 and three faults 11b3 is sent from the corresponding output terminal to the switch 12a. Supplied. Of course, the zero (0) unit failure 11b0 is a case where all of the parallel amplifiers 41 to 43 are operating normally, and a signal of level “1” is supplied to the switch 12a from the output terminal 11b0.

However, in the above example, the number of failed units calculated when all three configured parallel amplifiers 41 to 43 have failed (when the output level of the output terminal 11b3 is "1")
Means that the output of the entire apparatus is stopped or a state close thereto, so that the signal can be treated as, for example, indicating a failure of the entire apparatus without the automatic gain control functioning.

In this manner, the faulty number detecting circuit 11
Introduces output signals from each of the parallel amplifiers 41 to 4N,
From the output power value, it is determined whether the corresponding output voltage value has become lower than a predetermined level value, and it is determined that the parallel amplifier that has dropped below the predetermined level value has failed, and The number X is calculated and supplied to the switch 12a of the reference voltage generation circuit 12.

The reference voltage generating circuit 12 is configured as shown in FIG. 4, and the switch 12a includes parallel amplifiers 41 to 4N
Reference voltage setter 12b that generates reference voltages Vm0 to VmN respectively set corresponding to the number of failures X (0 to N)
0 to 12 bN are connected. Further, in this embodiment, each of the reference voltages Vm0 to VmN is set to a voltage level at a rate corresponding to the number X of failures calculated by the above-described equation (1).

As shown in FIG. 4, the switch 12a connects the output signals corresponding to the number of faults of the calculation circuit 11b to the relays R0 to RN.
Is configured to close the corresponding relay contacts R0a to RNa when receiving a signal of "1" level from the number-of-failures detection circuit 11, so that based on the signal of the number of failures detected from the calculation circuit 11b, The corresponding reference voltages Vm0 to VmN are supplied to the control voltage generation circuit 9 via the relay contacts R0a to RNa.

Then, the control voltage generation circuit 9 receives the detection voltage V from the power detection circuit 8 and the reference voltages (Vm0 to VmN) selected by the switch 12a, performs a corresponding comparison, and performs a control voltage S (= V to (Vm0 to VmN)) are supplied to the variable attenuator 2 to control the amount of attenuation.

Therefore, for example, five (N = 5) parallel amplifiers 41 to 45 are operated, and one of them (X =
Assuming that 1) has failed, the composite output Z at that time is expressed as Z = Y × ((N−X) / N) ² in equation (1) as described above, and Z = Y ((5-1) ) / 5) ² = 0.64Y, which is reduced to 64% of the normal output Y. However, the number-of-failures detection circuit 11 detects one failure, and the switch 12a of the reference voltage generation circuit 12 The reference voltage Vm1 corresponding to the output drop when one unit fails, that is, Vm1 = 0.64V
The reference voltage at the level m0 is supplied from the reference voltage setting unit 12b1 to the control voltage generation circuit 9.

As described above, the reference voltage Vm1 is set to a low voltage signal corresponding to 0.64 times the reference voltage Vm0 and supplied to the control voltage generation circuit 9 in response to the decrease of the combined output. Similarly, the reference voltage in the case of X units failure corresponds to the output decrease, and the reference voltage Vm0 in the case of no failure.
Of ((N one X) / X) since the setting is reduced to ^2-fold,
The variable attenuator 2 converts the input high-frequency signal into a parallel amplifier 42 through the distributor 3 without unnecessarily reducing the attenuation.
Ｎ4N. Accordingly, the automatic gain control circuit operates so that the input / output characteristics of each normal amplifier maintain a good state, and deterioration in the characteristics of the amplifier can be avoided.

In the above description, the failure detector 11a
Although the voltage conversion / comparison circuits 11a1a of 1 to 11aN are described as outputting a signal of level "0" on the assumption that they are operating normally, they are inverted to output a signal of level "1" when operating normally. Further, when a failure occurs, a signal of level “0” may be output and the operation may be performed thereafter.

As described above, the automatic gain control device according to this embodiment detects the output power and converts the converted voltage V to the reference voltage (Vm0 to VmN) corresponding to the number of failed X of the parallel amplifiers 41 to 4N. ), The variable attenuator 2 to which the control signal S is supplied does not operate so as to unnecessarily reduce the amount of attenuation as in the related art.
The remaining parallel amplifiers (41 to 4N) that operate normally continue the amplification operation in the linear region, and can derive a good output signal with little distortion and noise while maintaining stable automatic control.

In this embodiment, it goes without saying that the same effect can be obtained by replacing the variable attenuator 2 with an automatic gain amplifier as in the conventional case. Further, this automatic gain control device can be provided not only in the final stage of the transmission output stage but also in the intermediate frequency stage and the like.

As described above, even if one of the parallel amplifiers 41 to 4N fails, the automatic control apparatus according to the present invention can continue to input the almost same level of input to the other normal parallel amplifiers. Since the signal is supplied, the operating characteristics of the amplifier can be continued in the operating region that does not include the non-linear region composed of linear characteristics, and an output signal with less distortion and noise can be obtained. As for the output level fluctuation based on the change of the operating point, the normal automatic control operation continues to function, so that a stable output can be derived, and the effect obtained in practical use is large.

[0035]

As described above, according to the present invention, in the automatic gain control device, even if a part of a plurality of amplifiers to be combined in parallel fails, other amplification characteristics are not deteriorated and distortion and noise are included. It is possible to continually derive a high-quality high-frequency signal, and it can be used in a transmission output stage or the like of a television transmitter to obtain remarkable effects.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of an automatic gain control device according to the present invention.

FIG. 2 is a circuit configuration diagram showing a failure detector of a failure number detection circuit of the apparatus shown in FIG.

FIG. 3 is a circuit configuration diagram showing a calculation circuit of a failure number detection circuit of the device shown in FIG. 1;

FIG. 4 is a circuit configuration diagram showing a reference voltage generation circuit of the device shown in FIG. 1;

FIG. 5 is a circuit diagram showing a conventional automatic gain control device.

[Explanation of symbols]

 Reference Signs List 2 variable attenuator 3 distributor 41-4N parallel amplifier 5 combiner 6 distributor 8 output detection circuit 9 control voltage generation circuit 10 reference voltage generation circuit 11 failure number detection circuit 11a1-11aN failure detector 11b calculation circuit 12 reference voltage generation Circuit 12a Switch 12b0-12bN Reference voltage setting unit S Control signal

Claims (3)

[Claims] 1. A variable attenuator or variable gain amplifier to which a high-frequency signal is supplied, a distributor connected to the variable attenuator or variable gain amplifier, and amplifying the high-frequency signal distributed by the distributor. A parallel amplifier, a combiner connected to the parallel amplifier, for combining and outputting the amplified high-frequency signals, and detecting an output power of the high-frequency signal combined and output by the combiner and outputting a corresponding voltage. An output detection circuit for detecting the number of failed amplifiers connected to the parallel amplifier, and a failure level detection circuit connected to the failure number detection circuit, the reference having a preset level corresponding to the number of failed amplifiers A reference voltage generation circuit for outputting a voltage; and deriving a difference between the reference voltage from the reference voltage generation circuit and the voltage derived from the output detection circuit. Automatic gain control apparatus characterized by comprising a control signal generating circuit configured to control an attenuator or a variable gain amplifier. 2. The circuit according to claim 2, wherein the reference voltage generation circuit receives an output signal from the failure number detection circuit,
2. The automatic gain control device according to claim 1, wherein a reference voltage having a lower level is supplied to the control voltage generation circuit as the number of faults increases. 3. The reference voltage generating circuit according to claim 1, wherein said number of said parallel amplifiers is N, said number of said faulty amplifiers among said N parallel amplifiers is X, and said N parallel amplifiers all operate normally. When the output voltage value is Y, Y ((N
3. The automatic gain control device according to claim 1, wherein a voltage satisfying -X) / N) ² is set to be output.