JP3051297B2 - Emergency stop circuit of feedforward amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedforward amplifier for use in communication, broadcasting, audio equipment and the like.
Particularly, when an abnormal distortion component output typified by spurious occurs due to deterioration of the linearity of the amplifier due to a circuit failure or the like, the output is cut off or the cutoff is made possible. .

[0002]

2. Description of the Related Art As an input / output nonlinear compensation method for an amplifier effective in a high frequency band such as a microwave band, there is a feedforward distortion compensation circuit shown in FIG. 4 (hereinafter, an amplifier having this compensation circuit is referred to as a feedforward amplifier). Name). The feedforward distortion compensation circuit is basically composed of two interference circuits. One is a distortion detection circuit 3, and the other is a distortion removal circuit 4. The distortion removal circuit 3 includes a main amplified signal path 5 and a linear signal path 6. The distortion removal circuit 4 includes a main signal path 7 for linearly transmitting an output signal of the main amplified signal path 5, and a distortion injection path 8. It is composed of further,
The main amplified signal path 5 is a series connection of a main amplifier 9 and a variable attenuator 10 and a variable phase shifter (generally, a variable delay line is used) 11 for adjusting the amplitude and phase transfer characteristics of the path 5, respectively. , And the linear signal path 6 is composed of a series connection of a delay line 12 and a phase inversion circuit 13. The main signal path 7 includes a delay line 14, and the distortion injection path 8 includes a series connection of a variable attenuator 15, a variable phase shifter 16, and an auxiliary amplifier 17. Auxiliary amplifier 17
May include a phase inversion circuit. Here, since there is no significant difference in characteristics, the variable attenuator 10 and the variable phase shifter 11 included in the distortion detection circuit 3 are connected to the linear signal path 6 in a form of both or only one of them. May be provided. Similarly, in the distortion removal circuit 4, the variable attenuator 15 and the variable phase shifter 16 may be provided in the main signal path 7 in a form of both or only one of them. A power divider 18 that couples the input terminal 1 to the main amplified signal path 5 and the linear signal path 6, and a power combiner / divider 19 that couples the distortion detection circuit 3 and the distortion removal circuit 4
And a power combiner 20 for coupling the main signal path 7 and the distortion injection path 8 to the output terminal 2 are simple lossless power dividers / power combiners each composed of a transformer circuit, a directional coupler, and the like. .

First, this operation will be described. The input signal input to the input terminal 1 is divided into two outputs by the power divider 18 and supplied to the paths 5 and 6, and both outputs of the paths 5 and 6 are supplied to the power combiner / divider 19 by the power combiner / divider 19. Synthesized. Here, the variable attenuator 10 and the variable phase shifter 11 included in the distortion detection circuit 3 provide two signal paths 5 and 6 for the signal components output from the power combiner / distributor 19 to the distortion injection path 8 side. The transmission characteristics are amplitude,
Adjustments are made so that the delay amounts are equal and the phases are opposite. However, the reverse phase condition can be realized by appropriately setting the amount of phase shift between the input and output terminals of the distributor 18 and the power combiner / distributor 19, or by providing the input and output phase inversion characteristics to the main amplifier 9. Or by inserting a phase inversion circuit having a short-circuit termination at one terminal of the circulator in either of the paths 5 and 6. At this time, the transmission loss of the path from the input terminal 1 to the main amplified signal path 5 through the power combiner / distributor 19 and the main signal path 7 and the output terminal 2 via the power combiner 20 is as small as possible. The parameters of the elements of each circuit are set so that the power gain and output of the amplifier 9 do not decrease.

Since the distortion detection circuit 3 is configured as described above, the output of the terminal 19d on the path 8 side of the power combiner / distributor 19 is a component linearly proportional to each input signal of the two paths 5 and 6. Are canceled each other, and a non-linear component generated by the main amplifier 9 is detected as a difference component between the two signals. For this reason, this interference circuit is called a distortion detection circuit. Next, the variable attenuator 15 and the variable phase shifter 16 provided in the distortion injection path 8 are connected from the terminal 19 a connected to the main amplified signal path 5 of the power combiner / distributor 19 to the output terminal of the power combiner 20. The transfer functions of the two paths 7 and 8 leading to 20c are adjusted so as to be equal to each other with respect to the amplitude and the amount of delay, and to be opposite in phase with respect to each other. Here, since the input signal of the distortion injection path 8 is the distortion component of the main amplifier 9 detected by the distortion detection circuit 3, the path 8 is connected to the output terminal 20 of the power combiner 20.
c, that is, at the output terminal 2 of the feedforward amplifier, the distortion component generated by the same main amplifier 9 is injected into the output signal of the main amplifier 9 with the same amplitude in opposite phase, and as a result, the distortion component in the output of the entire circuit is eventually obtained. Cancellation is achieved. The above is the operation principle of the feedforward amplifier.

Thus, the feedforward amplifier is composed of two interference circuits for signal cancellation and distortion cancellation, which can be modeled in principle as a simple feedforward interference circuit as shown in FIG. As shown in the figure, the interference circuit distributes an input signal at an input terminal 23 to two signal paths 25 and 26 by a power divider 24, and outputs the outputs of the two signal paths 25 and 26 to a power combiner 28. And supplies it to the output terminal 27. The signal path 25 includes a variable attenuator 29, a variable phase shifter 30, an amplifier 31
The signal path 26 includes a delay line 32 and a phase inversion circuit 33. Here, the amplifier 31 corresponds to the main amplifier 9 in the case of the distortion detection circuit 3, and corresponds to the auxiliary amplifier 17 in the case of the distortion removal circuit 4.

The optimum operation of this feedforward interference circuit is based on the two paths 25, 2
6 is that the transfer functions are balanced with each other under the conditions of equal amplitude and equal delay amount and opposite phase functions in the phase function. This balance state is detected, and the circuit is automatically set to the optimum balance state. As a method, Japanese Patent Application No. 63-23574 "Automatic adjustment circuit of feed forward amplifier" and Japanese Patent Application No.
There is a method using a pilot signal as described in No. 49688 “feedforward amplifier”. FIG. 6 shows a basic configuration of a circuit for realizing this method. The pilot signal from the pilot generator 36 is injected into the input path by a pilot injection circuit 37 provided in the input path. A pilot signal is extracted by a pilot extraction circuit 41 using a directional coupler or the like inserted in the path 8, and the extracted output is used as a pilot level detector 4 composed of a receiver or the like.
The level is detected at 2 and supplied to a control circuit 43 composed of a microcomputer or the like. On the other hand, a pilot signal from pilot generator 39 is injected into path 5 by pilot injection circuit 40 provided in path 5. A pilot signal is extracted by a pilot extraction circuit 45 using a directional coupler or the like inserted on the output side 35 of the power combiner 20, and the level of the extracted output is detected by a pilot level detector 46 composed of a receiver or the like. And supplied to the control circuit 43.

The operation of this circuit will be described. The pilot generator 36 generates a first pilot signal of a continuous wave at a specific frequency. The first pilot signal is extracted by a pilot extraction circuit 41, and a pilot level detector 42 using an amplitude detector or a homodyne detector having a narrow band characteristic.
Is detected by If the two signal paths 5 and 6 constituting the distortion detection circuit 3 are in the above-described optimum operation state, the level of the first pilot signal necessarily detected is also zero. Therefore, the pilot level detector 4 proportional to this level
While monitoring the output of the pilot level detector 4, the set value of the vector modulator 38 inserted into the path 5 of the distortion detection circuit 3 is changed little by little by applying, for example, the perturbation method.
If the point at which the output of the second signal is minimum is detected and the vector modulator 38 is set at the operating point, the optimum operation state of the distortion detection circuit 3 can be realized. Similarly, the pilot generator 3
9 generates a continuous wave second pilot signal at a specific frequency different from the frequency of the first pilot signal. The second pilot signal is extracted by a pilot extraction circuit 45 and detected by a pilot level detector 46 using an amplitude detector having a narrow band characteristic or a homodyne detector. If the two signal paths 7 and 8 constituting the distortion removing circuit 4 are in the above-described optimum operation state, the level of the second pilot signal necessarily detected becomes zero. Therefore, while monitoring the output of the pilot level detector 46 proportional to this level, the set value of the vector modulator 44 inserted into the path 8 of the distortion removing circuit 4 is changed little by little, for example, by applying a perturbation method. The optimum operation state of the distortion removal circuit 4 can be realized by detecting the point where the output of the pilot level detector 46 is minimum and setting the vector modulator 44 at the operation point. Such automatic control can be easily achieved using a microcomputer.

[0008]

In the feedforward amplifier as described in the preceding item, for example, the automatic gain adjustment is performed by a failure of the amplification element constituting the auxiliary amplifier 17 and a significant decrease in the amplification gain. When the balanced state of the feedforward interference circuit is not maintained, the distortion is output without being sufficiently reduced. For this reason, when this feedforward amplifier is used in a wireless transmitter or the like, when such a failure occurs, the distortion output becomes spurious emission or the like and interferes with other radio waves. Must be stopped, but this cannot be performed unless the output spectrum is measured.

An object of the present invention is to provide a feedforward amplifier that can quickly stop or stop the output of an amplifier when the balanced state of the feedforward interference circuit is no longer maintained.

[0010]

In any of the claimed inventions, the first and the second components which are output from the feedforward amplifier are described.
When at least one of the second pilot signals does not become substantially zero and becomes larger than a predetermined level, this is detected by the non-compensation detecting means, and output cutoff means for cutting off the output of the feedforward amplifier is provided. According to the first aspect of the invention, the detection output of the non-compensation detecting means is further displayed on the display means. According to the second aspect of the present invention, the non-compensation detection means sends the detection output to the outside as an alarm signal, and the output cutoff means is configured so that the cutoff operation is controlled by an external control signal. According to the third aspect of the present invention, the non-compensation detection means outputs a control signal upon detection, and the output cutoff means is configured to control the cutoff operation by the control signal.

[0011] In the output cutoff means, at least means for cutting off the operating power supply to the main amplifier, or means inserted into the input path of the power divider to cut off the input signal;
Alternatively, it is a means inserted into the output path of the power combiner to cut off the output signal.

[0012]

According to the first aspect of the present invention, when the feedforward amplifier cannot be compensated, this is displayed. Therefore, the distortion component is not output to the outside, for example, when the maintenance worker shuts off the output by the output shut-off means while watching the display. According to the second aspect of the present invention, a maintenance person at a remote location receiving the alarm signal
The control signal can be sent to the output blocking means to perform the blocking control. According to the third aspect of the invention, when the compensation is disabled, the output cut-off means is automatically cut off by the control signal.

[0013]

FIG. 1 shows an embodiment of the invention of claim 1, and FIG.
The parts corresponding to are denoted by the same reference numerals. According to the present invention, the display circuit 47 is connected to the control circuit 43, and the power supply circuit 48 for supplying operating power to the main amplifier 9 and the auxiliary amplifier 17 is stopped by a maintenance person or operator to supply the power. Have been able to. That is, although not shown, a cutoff circuit is inserted at the output side of the power supply circuit 48, and the cutoff circuit is turned off or the main switch between the power supply circuit 48 and the main power supply is turned off. Being able to be.

Further, the control circuit 43 has an incompensation detection function, and controls the vector modulators 38 and 44 on the path 5 and the path 8, respectively. When any one of the levels does not become substantially zero and becomes larger than a specific level, that is, when the compensation becomes impossible, the display circuit 47 is controlled, and the display circuit 47 confirms that the distortion has been output. The display is performed by turning on an LED or the like. When the operator or the maintenance person sees this display, he or she directly operates the power supply circuit 48 and
The power supply current supplied to 17 is cut off. Here, the case where at least one of the levels of the first pilot signal or the second pilot signal does not become substantially zero and becomes larger than a specific level means that the operation of the distortion compensation in the feedforward amplifier does not function sufficiently. This corresponds to the state, and means that distortion may be output. In such a case, the operator or the maintenance person directly operates the power supply circuit 48 to cut off the power supply current supplied to each of the amplifiers 9 and 19, thereby preventing distortion from being output to the output terminal 2. be able to.

FIG. 2 shows an embodiment of the second and third aspects of the present invention, in which parts corresponding to those in FIG. This embodiment is applied when an operator or a maintenance person is farther away from the feedforward amplifier. The control circuit 43 supplies the non-compensation detection output to the external output terminal 51, and the power supply circuit 48 has a power control terminal 49 for electrically operating the shut-off function.
0 is connected to the outside.

Although the control circuit 43 controls each of the vector modulators 38 and 44 on the paths 5 and 8, even one of the levels of the first pilot signal and the second pilot signal becomes almost zero. In contrast, when the level exceeds a specific level (when compensation is detected), the display circuit 47 is controlled to display that distortion has been output, and to output an alarm signal to the external output terminal 51. Send out. The external output terminal 51 and the power control connection terminal 50 are wired via a communication line to a monitoring room where an operator or a maintenance person monitors at a remote place. The operator or maintenance person can use the external output terminal 5
When the reception of the alarm signal 1 is recognized, a control signal is transmitted to the power control connection terminal 50 by operating a switch or the like. The power supply circuit 48 operates in response to the control signal via the power supply control terminal 49 and cuts off the power supply current supplied to each of the amplifiers 9 and 17. With the above operation, it is possible to prevent distortion from being output to the output terminal 2.

In the above description, the power supply to the amplifiers 9 and 17 is cut off to cut off the output of the feedforward amplifier. However, only the power supply to the main amplifier 9 may be cut off. The supply of power to the whole may be cut off. In order to further shut off the output, as shown in FIG. 3 by attaching the same reference numerals to parts corresponding to those in FIG. 1, the input path of the power distributor 18, in this example, between the signal input terminal 1 and the pilot injection circuit 37 The signal cutoff circuit 52 may be inserted into the circuit, and this circuit may be controlled to be disconnected by an operation of a maintenance person. Even in the case of such a signal interruption, an alarm signal may be transmitted remotely as described above, and at a monitoring station receiving the alarm signal, a maintenance person may send a control signal to remotely control the alarm signal. Then, a control signal may be output to automatically turn off the signal cutoff circuit 52.

In these cases as well, it is possible to prevent the distortion from being output to the output terminal 2 when the compensation becomes impossible. Similarly, a signal cutoff circuit may be inserted in the output path of the power combiner 20 to control the signal cutoff circuit. Further, the feedforward amplifier is not limited to the example shown in FIG. 1, and various modifications are possible as described in the section of [Prior Art]. Further, the display circuit 47 may be omitted in FIG. When the power supply circuit 48 is automatically turned off by a control signal from the control circuit 43, an alarm signal need not be output to the outside.

[0019]

As described above, according to the present invention, the level of each of the first and second pilot signals is monitored to detect an uncompensated state, which is displayed and the maintenance person cuts off the amplifier output. , So that it is possible to prevent other radio waves from being disturbed by the distortion output. When the feedforward amplifier is operated in a parallel configuration, a high quality service can be provided by shutting off the output of a failed amplifier that may output distortion.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing an embodiment of the invention according to claims 2 and 3;

FIG. 3 is a block diagram showing another embodiment of the invention of claim 1;

FIG. 4 is a block diagram showing a basic configuration of a feedforward amplifier.

FIG. 5 is a block diagram showing a basic configuration of a feedforward interference circuit.

FIG. 6 is a block diagram showing a feedforward amplifier that is automatically adjusted.

Continuing on the front page (72) Inventor Shoichi Narahashi 2-10-1 Toranomon, Minato-ku, Tokyo NTN Mobile Communication Network Co., Ltd. (72) Inventor Makoto Maeda 2-chome Toranomon, Minato-ku, Tokyo No. 1 NTT NTT Mobile Communication Network Co., Ltd. (72) Inventor Hironori Sakamoto 5-1-1 Shimorenjaku Nihon Radio Co., Ltd. (56) References JP-A-4- 213207 (JP, A) JP-A-5-243859 (JP, A) JP-A-1-198809 (JP, A) JP-A-3-68227 (JP, A) JP-A-5-129970 (JP, A) JP-A-5-175759 (JP, A) JP-A-64-77225 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 1/04 H03F 1/32

Claims (5)

(57) [Claims] An input signal is divided into a main amplified signal path and a linear signal path by a power divider, and the input signal distributed to the main amplified signal path is amplified by a main amplifier. The output of the linear signal path is combined with the power combiner / divider and distributed to the main signal path and the distortion injection path. The signal of the distributed distortion injection path is amplified by the auxiliary amplifier, and the amplified signal and A power combiner combines the output of the main signal path with the output, and a second pilot signal is injected into the main amplified signal path, and a first pilot signal input to the power divider is transmitted through the distortion injection path. And input to the control circuit.
The control circuit controls at least one of the transfer characteristics of the main amplified signal path and the linear signal path so that the first pilot signal thus pumped out becomes substantially zero. on the second pilot signal out Note
And a control circuit for controlling a transfer characteristic of at least one of the main signal path and the distortion injection path so that the extracted second pilot signal becomes substantially zero. In the emergency stop circuit, the control circuit detects that at least one of the issued first pilot signal and the issued second pilot signal does not become substantially zero but becomes larger than a predetermined level. An emergency stop circuit for a feedforward amplifier, comprising: a compensation impossible detection means ; a display means for displaying a detection state of the compensation failure detection means; and an output cutoff means for cutting off an output of the feedforward amplifier. 2. An input signal is divided into a main amplified signal path and a linear signal path by a power divider, and the input signal distributed to the main amplified signal path is amplified by a main amplifier. The output of the linear signal path is combined with the power combiner / divider and distributed to the main signal path and the distortion injection path. The signal of the distributed distortion injection path is amplified by the auxiliary amplifier, and the amplified signal and A power combiner combines the output of the main signal path with the output, and a second pilot signal is injected into the main amplified signal path, and a first pilot signal input to the power divider is transmitted through the distortion injection path. Note out and input to the control circuit from its control
The control circuit controls at least one of the transfer characteristics of the main amplified signal path and the linear signal path so that the first pilot signal thus pumped out becomes substantially zero. on the second pilot signal out Note
And a control circuit for controlling a transfer characteristic of at least one of the main signal path and the distortion injection path so that the extracted second pilot signal becomes substantially zero. In the emergency stop circuit, the control circuit detects that at least one of the ejected first pilot signal and the ejected second pilot signal does not become substantially zero but becomes larger than a predetermined level. Has an incompensation detection means for sending an alarm signal to the outside.
And operates by a control signal from the outside, the emergency stop circuit of the feedforward amplifier comprising an output blocking hand stage, to shut off the output of the feed forward amplifier. 3. The input signal is divided into a main amplified signal path and a linear signal path by a power divider, and the input signal distributed to the main amplified signal path is amplified by a main amplifier. The output of the linear signal path is combined with the power combiner / divider and distributed to the main signal path and the distortion injection path. The signal of the distributed distortion injection path is amplified by the auxiliary amplifier, and the amplified signal and A power combiner combines the output of the main signal path with the output, and a second pilot signal is injected into the main amplified signal path, and a first pilot signal input to the power divider is transmitted through the distortion injection path. And input to the control circuit.
The control circuit controls at least one of the transfer characteristics of the main amplified signal path and the linear signal path so that the first pilot signal thus pumped out becomes substantially zero. An emergency stop circuit for a feed-forward amplifier for outputting a second pilot signal and controlling at least one transfer characteristic of the main signal path and the distortion injection path so that the extracted second pilot signal becomes substantially zero. in inputs to the control circuit, the control circuit is one at least of the first pilot signal and the dispensed the second pilot signal issued the note is not substantially zero, becomes larger than a predetermined level have a compensation undetectable means for outputting a detection to a control signal that operates by the control signal, to shut off the output of the feedforward amplifier output Emergency stop circuit of the feedforward amplifier comprising Dante stage, the. 4. An emergency stop circuit for a feedforward amplifier according to claim 1, wherein said output cutoff means is a means for cutting off the supply of operating power to at least said main amplifier. . 5. The feedforward amplifier according to claim 1, wherein said output cutoff means is a signal cutoff means inserted into an input path of said power divider to cut off an input signal. Emergency stop circuit.