JPH06177673A - Multi-stage collector traveling wave tube amplifier - Google Patents

Abstract

PURPOSE:To realize the miniaturization and economy of equipment using an amplifier by reducing the power consumption of the traveling wave tube amplifier so as to facilitate the reduction in the operation cost and the power and heat design. CONSTITUTION:An amplifier is made up of a traveling wave tube amplifier 13 having two collector electrodes 10, 11, 12 or over and a power supply 14. A potential less than 60% of the potential of the collector 12 when minimum power consumption is obtained at the saturation is set to the collector 12 located remotest from an electron gun 15 to which a minimum potential is set among all the collectors of the traveling wave tube 13 so that the power consumption is a minimum power consumption or close thereto in the nonsaturation state or an intermittent saturation representing a tentative saturation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multistage collector traveling wave tube amplifier, and more particularly to a low power consumption multistage collector traveling wave tube amplifier.

[0002]

2. Description of the Related Art In a traveling-wave tube amplifier composed of a traveling-wave tube and a power source for the traveling-wave tube, as an effective means for increasing efficiency and reducing power consumption, the traveling-wave tube has a plurality of collector stages. , A method of applying different voltages to each collector electrode is adopted. To determine the collector voltage of such a multistage collector traveling-wave tube, the high-frequency input power of the traveling-wave tube is kept at a constant value so as to give a saturated output, and at the same time, the electrode voltage is also kept constant. Then, the DC input power is measured by changing the voltage of the collector of interest. Further, the voltage of the next collector is set by the same operation, and in order to set the voltages of a plurality of collectors, this work is repeated and converged.

By setting the voltage in this manner, the traveling wave tube can operate at near-optimal efficiency at saturated output. In the multistage collector traveling-wave tube, when there is no input power, the power consumption is smaller than that at the saturated output, but the amount of decrease is not large.

[0004]

However, in the case of using the method of use in a saturated operation in which the traveling wave tube operates in a saturated state, the actual power consumption is determined by the collector voltage setting method shown above. Can be almost the minimum.
However, in the case of a method of simultaneously amplifying a large number of carriers in the same channel, the collector voltage is set at a low input level in order to suppress the generation of unnecessary waves due to the third-order cross modulation characteristic of the traveling wave tube. In addition, time division multiple access (TDM
A) Although the output level is the saturation level in the power amplifier for the satellite communication system earth station, the ratio of the saturation output transmission time is 1% depending on the amount of signal transmitted during the time when the signal is output.
To about 100%, and in a small-scale earth station, the ratio of the saturated output transmission time is actually 10% or less in many cases.

As described above, when the signal level is low or the ratio of the saturated output transmission time is small, the power consumed ineffectively is large compared to the saturated state, and the power consumption cannot be ignored.

The present invention has been made in view of the above points,
An object of the present invention is to provide a multistage collector traveling-wave tube amplifier that can reduce the power consumption of the traveling-wave tube amplifier, reduce its operating cost, and facilitate power and thermal design to realize a compact and economical device. To do.

[0007]

FIG. 1 is a block diagram showing the principle of the present invention. In the multi-stage collector traveling-wave tube amplifier having two or more collector electrodes 10, 11, 12, the farthest from the electron gun 15 of the traveling-wave tube 13 during non-saturation operation or intermittent saturation operation that temporarily becomes saturation operation. The potential of the collector electrode 12 at the position is smaller than the potential of the collector electrode 12 that causes the minimum power consumption during the saturation operation with reference to the cathode potential of the traveling wave tube 13, and is saturated during the non-saturation operation or temporarily. It is set to a predetermined potential such that the power consumption becomes the minimum or a state close to the minimum during intermittent saturation operation. In addition, the predetermined potential of the collector electrode of the traveling wave tube 13 located farthest from the electron gun 12 during the unsaturated operation or the intermittent saturated operation that is temporarily saturated results in the minimum power consumption during the saturated operation. Is 60% or less of the potential of the collector electrode 12 at the farthest position. Further, the traveling wave tube 13 has a detecting means for detecting the high frequency input power or the high frequency output power of the traveling wave tube 13, and an average value calculating means for obtaining an average value of the outputs of the detecting means. The potential of the collector electrode 12 located farthest from the electron gun 15 is increased.

[0008]

According to the present invention, in a traveling wave tube having a multi-stage collector having two or more stages, the collector located farthest from the electron gun and the low-speed wave circuit at the time of non-saturation operation or intermittent saturation operation which temporarily becomes saturation operation. The collector electrode potential that is set to the lowest potential is set to a potential that is 60% or less of the potential that gives the minimum power consumption during the saturation operation with reference to the cathode potential. It also detects the input or output high frequency power of the traveling wave tube,
When this average power exceeds a predetermined level, the collector electrode potential of the lowest potential is raised to a voltage near the voltage that minimizes power consumption during saturation operation, and the input or output high frequency power of the traveling wave tube is below a predetermined level. If the potential of the collector electrode is set to a potential lower than the potential that gives the minimum power consumption during saturation operation, the power consumption when the signal level is low or the saturation output sending time ratio is low Reduce the amount.

[0009]

EXAMPLE A case of a saturated operation and a non-saturated operation will be described as an operating mode of the traveling wave amplifier of this example. First, for saturation operation, duty 1 is always in a saturated output state.
There are two states, a 00% state, and a duty of less than 100% in which a saturated output state and a non-saturated state are mixed and intermittent operation is performed. Further, the non-saturation operation indicates a no signal or small signal state.

FIG. 2 shows the first collector 10, the second collector 11, and the third collector 1 for the third collector voltage of the present invention.
It is a graph which shows the change of each 2 current. The graph shows the respective currents Ic1, Ic2, Ic3 flowing through the three collectors 10, 11, 12 at saturated output as a function of the third collector voltage Ec3. The collector electrodes are generally named as a first collector 10, a second collector 11, and a third collector 12 in order from the electrode close to the electron gun 15. Furthermore, the highest voltage is applied to the first collector 10, and the third collector 12
The lowest voltage is applied to. In the graph, when the third collector voltage Ec3 is increased, the third collector current Ic3 is increased, but the first collector current Ic1 and the second collector current Ic2 are increased.
Is shown to decrease.

FIG. 3 is a graph showing changes in the spiral current with respect to the third collector voltage Ec3 of the present invention. In the graph, the y-axis is the relative scale of the spiral current, and the x-axis is the third collector voltage Ec3. The graph 31 shows the change in the spiral current Ih at the saturated output, and the change in the spiral current Ih is small. On the other hand, graph 32 shows the spiral current Ih when there is no signal output.
Shows that there is almost no change after the third collector voltage Ec3 is 0.08 kV and once becomes low.

FIG. 4 is a graph showing the power consumption in the saturation operation and the non-signal operation with respect to the third collector voltage Ec3 of the present invention. In the graph, the y-axis shows the power consumption Pdc (W) and the x-axis shows the third collector voltage Ec3. The graph 41 shows the power consumption at the saturated output, and the power consumption becomes the minimum when the third collector voltage Ec3 is 0.6 kV. On the other hand, graph 42
Is the power consumption during non-saturated operation with no signal output,
The power consumption becomes minimum when the third collector voltage Ec3 is 0.15kV.

The change in power consumption at the saturated output is gradual and small, whereas in the non-signal output, the third collector current Ic3 decreases and the voltage is higher than that of the third collector 12. Since the collector currents Ic1 and Ic2 increase, the power consumption sharply decreases together with the third collector voltage Ec3.

FIG. 5 is a graph showing the average power consumption with respect to the usage time ratio (duty) of the present invention. Based on the relationship with FIG. 4, this graph plots the relationship between the duty cycle, that is, the ratio of the time of operation in the saturated state and the average power consumption, using the third collector voltage Ec3 as a parameter. In the figure, graph a is the second collector voltage
The average power consumption when Ec2 is 1.2 kV and the third collector voltage Ec3 is 0.6 kV is shown. The graph b shows that the second collector voltage Ec2 is 1.2kV and the third collector voltage Ec3 is 0.36k.
Indicates the average power consumption when V is set. Graph c shows the average power consumption when the second collector voltage Ec2 is 1.2 kV and the third collector voltage Ec3 is 0.15 kV. The graph d shows that the second collector voltage Ec2 is 0.8kV and the third collector voltage is
The average power consumption when Ec3 is 0.15kV is shown.

FIG. 6 is a block diagram of a multistage collector traveling wave tube amplifier according to the first embodiment of the present invention. This multistage collector traveling-wave tube amplifier is composed of a traveling-wave tube 61 and a power source 62. Further, the traveling-wave tube 61 includes a cathode 63, an anode 64, a helix 65, a first collector 66, a second collector 67, and a third collector. It is composed of 68. On the other hand, the power source 62 includes an anode power source 69, a spiral power source 70, a first collector power source 71, and a second power source.
It is composed of a collector power supply 72 and a third collector power supply 73.

In this embodiment, the potential of the third collector is set to 0.15k.
It is the same as a normal traveling-wave tube amplifier except that it is set to V, and the potentials of the first collector 66 and the second collector 67 are both set to a value that minimizes the power consumption in the saturation operation.

In this embodiment, the first collector voltage Ec1 is 1.6
The kV and the second collector voltage Ec2 are set to 1.2 kV. As is apparent from FIG. 5, when the duty is 0.7 or less, the lowest average power consumption becomes the lowest for both the duty and the duty. In addition, when the duty is near 1.0, it is about 4W than the lowest average power consumption.
Only high value.

For example, in FIG. 5, the duty is 0.1.
At each time, each duty of the graph c showing the average power consumption when the third collector voltage Ec3 is 0.15 kV and the graph a showing the average power consumption when the third collector voltage Ec3 is 0.6 kV. The ratios for each are shown in the table below.

[0019]

[Table 1]

Referring to the graph of FIG. 5 and Table 1, when the duty becomes 0.1, the power consumption of the graph c becomes 12 W,
The power consumption of the graph a is 21W. Therefore, the ratio between the power consumption value of graph a and the power consumption value of graph c is 57%. In this way, especially when the duty is low, it is possible to significantly reduce the power consumption.

When the duty is 0.1, the average power consumption at the third collector voltage Ec3 0.36 kV is 16 W, and the average power consumption at the third collector voltage Ec3 0.6 kV is 2 W.
It is 1 W, and the ratio is 76%. However,
Graph b of 0.36 kV without the need of making the potential of the third collector to be 0.15 kV (graph c), which is the minimum power consumption when there is no signal.
If the power consumption is lower than about 60% of the third collector potential that minimizes the power consumption during the saturation operation, the effective power consumption can be reduced.

In this embodiment, the three-stage collector having an output of 10 W has been described, but if the high frequency output is large, the ratio of the power for cathode heating shown in the power consumption is small, and the power consumption reducing effect is further enhanced.

Furthermore, in this embodiment, only the potential of the third collector 68 having the lowest potential is lowered, but the third collector 68 is reduced.
However, by setting all collector potentials other than the highest potential collector (first collector 66) to a value different from the optimum value in the saturated state, the power consumption reduction efficiency can be further improved.

For example, in the spiral traveling wave tube 61 with the output of 10 W and the three-stage collector, the electric potential of the second collector 67 is 1.2 kV in the saturated state to minimize the power consumption.
When the third collector 68 is set to 0.15 kV, the potential of the second collector 67 that minimizes the power consumption during saturated output is about 0.8 kV. At this time, duty 1 with saturated output
The power consumption in 1 is reduced by about 1 W (graphs cd), and the power consumption in the no-signal state is also slightly reduced. Also,
The value of each duty is calculated based on the actual measurement values at the time of saturation operation and when there is no signal. FIG. 5 shows the effect of reducing the power consumption at this time.

FIG. 7 is a block diagram of a multistage collector traveling wave tube amplifier according to the second embodiment of the present invention. In the figure, the same components as those in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted.
The multistage collector traveling-wave tube amplifier according to the second embodiment has a directional coupler 84, a detector 85 and a detector 85 for branching input high frequency power.
It is composed of an integrating circuit 86, a comparing circuit 87, an optical coupler 88, a traveling wave tube 61, and a power source 62. Of these, the power supply 73 in the first embodiment was a one-valued power supply, but in this embodiment, the third collector power supply 80 of the power supply 62 is a two-valued power supply.

Next, the operation of the second embodiment will be described. The voltage of the third collector 68 is set to 0.15 kV when there is no high-frequency input power and there is no signal. The power consumption of the third collector at this time is about 10 W, which is the minimum value in FIG. The high frequency input signal is assumed to be a pulsed signal for the TDMA system. The input signal is separated by the directional coupler 84, and one signal is input to the helix 65 of the traveling wave tube 61 and amplified.
The other signal is input to a detector 82 which is a detecting means, is converted into a voltage and is input to an integrating circuit 83 which is an average value calculating means. The integrating circuit 83 converts the high frequency signal into a DC voltage proportional to the pulse duty. The output from the integrating circuit 83 is compared with a constant DC voltage in the comparing circuit 84, and when it becomes higher than this constant voltage, the digital output state of the comparing circuit 84 changes.

The state change of the comparison circuit 84 is transmitted from the potential of the ground 86 to the third collector power source 80 at the negative high potential through the optical coupler 85. If the reference voltage of the comparison circuit 84 is set to a value corresponding to a duty of about 0.8, the power consumption can be minimized in a wide duty range. Third collector power supply 80
Then, the output voltage is switched to 0.6 kV based on the input signal. As a result, the third collector voltage Ec3 is in the highest efficiency for the saturation operation.

When the duty of the high frequency input is lowered, the output voltage of the third collector power supply 80 is switched to 0.15 kV by the opposite operation.

Since the collector voltage of traveling wave tube 61 does not affect the characteristics of the high frequency signal, it is not necessary to control the collector voltage particularly at high speed, and a stable circuit with a relatively large time constant can be obtained. it can. When the change in the voltage of the third collector 68 lags behind the change in the pulse duty of the high frequency input signal, the power consumption is increased only by deviating from the minimum power consumption state for that period.

Assuming that the voltage Ec3 of the third collector 68 is 0.15 kV and the power consumption is minimum when the duty is 10%, the voltage Ec of the third collector 68 is as follows.
At 3 = 0.15kV, the power consumption does not become the lowest, and Ec3 ≈ 0.6
At kV, power consumption is lowest. Voltage of the third collector 68
The power consumption does not become the minimum during the time from when Ec3 starts to increase from 0.15kV to when it reaches 0.6kV.

The spiral current may change when the collector voltage is changed. In this case, the collector voltage is set outside the lowest point of power consumption, but this is not against the gist of the present invention.

The present invention is not limited to the above embodiment, but various applications are possible. For example, instead of the traveling wave tube 61 having a three-stage collector, a traveling wave tube having a two-stage or four-stage collector can perform the same operation by replacing the third collector 68 of the embodiment with the second collector or the fourth collector.

Further, instead of taking out the signal from the high frequency input section of traveling wave tube 61, it is also possible to take out the signal to be applied to detector 82 from the high frequency output section of traveling wave tube 61.

In this embodiment, the third collector power source 80
Although the output voltage of is changed to two values, it is also possible to change it to three values or more or continuously. In this case, the power consumption can be lowered to the minimum or a state closer to the minimum in a wider duty range.

Further, not only a pulsed high frequency signal but also a signal having a power level smaller than the saturation level is input, the same effect of reducing the power consumption can be obtained.

[0036]

As described above, according to the present invention, since high-speed control and external control are unnecessary, the system configuration is simple, the operation stability of the device is high, and the adjustment is easy. Further, it is possible to reduce the power consumption for a signal with a small duty or a signal with a low level without affecting the high frequency characteristics at all.

Furthermore, with the drastic reduction in power consumption,
Operational costs can be reduced, thermal design and device power design can be facilitated, and traveling wave tube amplifiers can be made smaller and more economical.

[Brief description of drawings]

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

FIG. 2 is a graph showing changes in first, second and third collector currents with respect to a third collector voltage of the present invention.

FIG. 3 is a graph showing a change of a spiral current with respect to a third collector voltage of the present invention.

FIG. 4 is a graph showing power consumption during a saturation operation and a no-signal operation according to a third collector voltage of the present invention.

FIG. 5 is a graph showing the average power consumption with respect to the usage time ratio of the present invention.

FIG. 6 is a configuration diagram of a multistage collector traveling wave tube amplifier according to the first embodiment of the present invention.

FIG. 7 is a configuration diagram of a multistage collector traveling wave tube amplifier according to a second embodiment of the present invention.

[Explanation of symbols]

 10,66 First collector 11,67 Second collector 12,68 Third collector 13,61 Traveling wave tube 14,62 Power supply 15 Electron gun 63 Cathode 64 Anode 65 Helix 71 First collector power supply 72 Second collector power supply 73 Third Collector Power Supply 81 Directional Coupler 82 Detector 83 Integrating Circuit 84 Comparison Circuit 85 Optical Coupler

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[Procedure amendment]

[Submission date] January 30, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art In a traveling-wave tube amplifier composed of a traveling-wave tube and a power source for the traveling-wave tube, as an effective means for increasing efficiency and reducing power consumption, the traveling-wave tube has a plurality of collector stages. , A method of applying different voltages to each collector electrode is adopted. To determine the collector voltage of such a multistage collector traveling-wave tube, the high-frequency input power of the traveling-wave tube is kept at a constant value so as to give a saturated output, and at the same time, the electrode voltage is also kept constant. Then, by changing the voltage at the collector of interest by measuring the input power of the DC, the co
The lector voltage is set to a voltage that minimizes the DC input power . Further, the voltage of the next collector is set by the same operation, and in order to set the voltage of a plurality of collectors, this work is repeated and converged.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

[0004]

However, in the case of using the method of use in a saturated operation in which the traveling wave tube operates in a saturated state, the actual power consumption is determined by the collector voltage setting method shown above. Can be almost the minimum.
However, in the case of a method that amplifies a large number of carriers in the same channel at the same time, it is unnecessary due to the third-order intermodulation characteristics of the traveling wave tube.
Use at low input levels to keep the wave generation low.
It In addition, in the power amplifier for the earth station for time division multiple access (TDMA) satellite communication system, the output level is the saturation level, but the saturation output transmission time is The ratio varies from 1% or less to nearly 100%, and in a small earth station, the ratio of the saturated output transmission time is actually 10% or less in many cases.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

FIG. 1 is a block diagram showing the principle of the present invention. In the multi-stage collector traveling-wave tube amplifier having two or more collector electrodes 10, 11, 12, the farthest from the electron gun 15 of the traveling-wave tube 13 during non-saturation operation or intermittent saturation operation that temporarily becomes saturation operation. The potential of the collector electrode 12 at the position is smaller than the potential of the collector electrode 12 that causes the minimum power consumption during the saturation operation with reference to the cathode potential of the traveling wave tube 13, and is saturated during the non-saturation operation or temporarily. It is set to a predetermined potential such that the power consumption becomes the minimum or a state close to the minimum during intermittent saturation operation. The predetermined potential of the non-saturation operation or during a collector electrode located farthest from the electron gun 1 5 TWT 13 intermittent saturation operation to be temporarily saturated operation and minimum power consumption at the time of saturation operation Is 60% or less of the potential of the collector electrode 12 at the farthest position. The traveling wave tube 13 has a high frequency input power or a high frequency output power detecting means, and an average value calculating means for calculating an average value of the output of the detecting means. The potential of the collector electrode 12 located farthest from the electron gun 15 is increased.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

According to the present invention, in a traveling wave tube having a multistage collector having two or more stages, all collectors located farthest from the electron gun and the low-speed wave circuit during non-saturation operation or intermittent saturation operation which temporarily becomes saturation operation. The collector electrode potential, which is set to the lowest potential, is set to a potential that is 60% or less of the potential that gives the minimum power consumption during the saturation operation with the cathode potential as a reference. Also, if the input or output high frequency power of the traveling wave tube is detected and this average power exceeds a predetermined level,
The collector electrode potential of the lowest potential is raised to a voltage near the minimum power consumption during saturation operation, and when the input or output high frequency power of the traveling wave tube falls below a predetermined level , the same collector electrode potential is set. By setting a potential lower than the potential that gives the minimum power consumption during the saturation operation, it is possible to reduce the power consumption when the signal level is low or the saturation output sending time ratio is low.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

Further, the change in power consumption at the saturated output is gradual and small . In case of no signal output , the third collector voltage
When the voltage becomes 0.15 kV or less, the third collector current Ic3 decreases, the voltage is higher than the third collector 12, and the first and second collector currents Ic1 and Ic2 increase, so that the power consumption increases with the third collector voltage Ec3. Increases rapidly.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

In this embodiment, the first collector voltage Ec1 is set to 1.6 kV and the second collector voltage Ec2 is set to 1.2 kV. As is clear from FIG. 5, the lowest average power consumption is almost the lowest when the duty is 0.7 or less. Further, when the duty is near 1.0, the value is only about 3 W higher than the lowest average power consumption.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

For example, in the spiral traveling wave tube 61 with the output of 10 W and the three-stage collector, the potential of the second collector 67 is 1.2 kV in the saturated state to minimize the power consumption, but the third collector 68 has a potential of 0. When set to 15 kV, the potential of the second collector 67 that minimizes the power consumption during saturated output is about 0.8 kV. At this time, the power consumption in the duty 1 at the saturated output decreases by about 1 W (graph cd), and the power consumption in the non-signal state also slightly decreases.
The value of the power consumption in each duty is calculated based on the measured values during the saturation operation and when there is no signal. FIG. 5 shows the effect of reducing the power consumption at this time.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

This is the third when the duty is 10%.
Or state in which a voltage Ec3 of the collector 68 is in the 0.15kV
The input signal duty suddenly changes to 100%
Assuming the voltage of the third collector 68 Ec3 = 0.15kV
Then, the power consumption does not become the lowest, and Ec3 ≈ 0.6kV, and the power consumption becomes the lowest. The voltage Ec3 of the third collector 68 is 0.15k
The power consumption does not reach the minimum during the time from when it starts to increase from V until it reaches 0.6kV.

[Procedure Amendment 9]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 10]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

[Procedure amendment]

[Submission date] February 15, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

Further, the change in power consumption at the saturated output is gradual and small . In the case of no signal output, when the third collector voltage becomes 0.15 kV or less, the third collector current Ic3 decreases, the voltage is higher than the third collector 12, and the first collector current Ic1 and the second collector current Ic2 increase. In addition, the power consumption sharply increases with the decrease of the third collector voltage Ec3.

Claims (3)

[Claims] 1. A multistage collector traveling-wave tube amplifier having two or more collector electrodes, wherein the traveling-wave tube is located furthest from the electron gun during non-saturation operation or intermittent saturation operation in which saturation operation is temporarily performed. The potential of the collector electrode at is smaller than the potential of the collector electrode, which is the minimum power consumption during the saturation operation, with reference to the cathode potential of the traveling wave tube, and during the non-saturation operation or the saturation operation temporarily. A multistage collector traveling-wave tube amplifier, which is set to a predetermined potential such that the power consumption becomes a minimum value or a value close to the minimum value during the intermittent saturation operation. 2. The predetermined potential of the collector electrode at the farthest position from the electron gun of the traveling wave tube during the unsaturated operation or the intermittent saturated operation in which the operation is temporarily saturated becomes the minimum during the saturated operation. 2. The multistage collector traveling-wave tube amplifier according to claim 1, wherein the potential of the collector electrode at the farthest position when power consumption is 60% or less. 3. A high-frequency input power or high-frequency output power detecting means for the traveling wave tube, and an average value calculating means for calculating an average value of the output of the detecting means. 2. The multistage collector traveling-wave tube amplifier according to claim 1, wherein the potential of the collector electrode at the farthest position from the electron gun of the traveling-wave tube is raised.