JPH04200105A - Travelling wave tube power amplifier - Google Patents

Abstract

PURPOSE:To keep an output power constant over a long period by controlling an anode voltage between an upper limit and a lower limit of the anode voltage depending on 1st, 2nd and 3rd resistors so that a cathode current is constant between both limits. CONSTITUTION:An output voltage of an anode power supply 3 is controlled by an anode voltage control circuit 2 connecting to the anode power supply 3 via an isolation transformer 4. On the other hand, a current control negative feedback amplifier 11 detects a cathode current of a travelling wave tube 13 to drive a transistor(TR) 9. Then an output voltage of the anode power supply 3 is controlled so that the cathode current of the travelling wave tube 13 is constant by a negative feedback loop. The upper limit and the lower limit of the anode voltage depend on the resistance of resistors 6, 7, 8 and are set optionally. Thus, the anode voltage does not run away even in the absence of information of the cathode current and the loop is made stable between the upper limit and the lower limit of the anode voltage depending on the resistance of the resistors 6,7,8.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to traveling wave tube power amplifiers.

[Conventional technology]

In a conventional traveling wave tube power amplifier, an anode voltage is outputted by a constant voltage stabilizing power supply circuit, and by stabilizing the anode voltage, the traveling wave tube amplifier is stably operated. However, this configuration cannot compensate for the decrease in cathode current due to deterioration of the cathode of the traveling wave tube, so there is a problem that the output power of the traveling wave tube power amplifier decreases over time due to changes in cathode current over time. .

A method to solve this problem is to detect the cathode current and control the anode voltage of the power supply for the traveling wave tube power amplifier.
A configuration has been proposed in which the output power of a traveling wave tube power amplifier is kept constant by keeping the cathode current of the traveling wave tube constant.

[Problem to be solved by the invention]

However, in the above-described configuration in which the anode voltage is controlled by detecting the cathode current, the cathode current may become excessive during transitions when starting or stopping the traveling wave tube power supply or when noise is added to the negative feedback loop. In the unlikely event that the loop breaks, the anode voltage may run out of control and damage the traveling wave tube.

The purpose of the present invention is to prevent the cathode current from becoming excessive even during startup/stop transients or when noise is added to the negative feedback loop, to prevent the anode voltage from running out of control, and to maintain a constant cathode current in a steady state. An object of the present invention is to provide a traveling wave tube power amplifier that provides the following characteristics.

[Means to solve the problem]

The traveling wave tube power amplifier of the present invention includes a traveling wave tube, a first control means for controlling an anode voltage supplied to the traveling wave tube within a predetermined upper and lower limit range, and
A power source for a traveling wave tube power amplifier, comprising a second control means for controlling the anode voltage within the range of the predetermined upper and lower limits so that the cathode current of the traveling wave tube is at a predetermined value. It is equipped with

The first control means includes a transistor, a first resistor, and a second resistor connected in parallel to a series connection circuit of the first resistor and a collector-emitter impedance of the transistor.
a third resistor connected in series to a parallel circuit of the second resistor and the series-connected circuit; a signal proportional to the anode voltage is divided between the third resistor and the parallel circuit; A first negative feedback amplifier inputting the obtained signal to both ends of the circuit, and an anode voltage control circuit controlling the anode voltage according to the output signal of the negative feedback amplifier,
The second control circuit may include a second negative feedback amplifier that detects the cathode current, inputs a detection signal, and has an output terminal connected to the base of the transistor.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

Referring to FIG. 1, one embodiment of the invention is a traveling wave pipe construction 3.
and a traveling wave tube power amplifier power supply 12. The traveling wave tube power amplifier power supply 12 is mainly composed of a collector helix power supply 1 and an anode power supply 3.

The output voltage of the anode power supply 3 is controlled by an anode voltage control circuit 2 connected to the anode power supply 3 via an isolation transformer 4, and its size is determined by the dividing resistor 6,
It is determined by the voltage at circuit point a, which is the common connection point of 7. The negative feedback amplifier 5 for voltage control inputs the voltage at the circuit point a to form a negative feedback loop for controlling the anode voltage, thereby stabilizing the output voltage of the anode power supply 3.

On the other hand, the current control negative feedback amplifier 11 detects the cathode current of the traveling wave tube 13 and passes it through the resistor 10 to the transistor 9.
to drive. The transistor 9 connects to the connection point a via the resistor 8.
The anode voltage control circuit 2 is connected to a negative feedback loop for anode voltage control, and the output voltage of the anode power supply 3 is changed by controlling the anode voltage control circuit 2 according to the magnitude of the cathode current. This negative feedback loop controls the output voltage of the anode power supply 3 so that the cathode current of the traveling wave tube 13 is constant.

The upper and lower limits of the anode voltage are determined by the values of the resistors 6 and 7.8, and can be set arbitrarily. That is, the value of resistors 6 and 7 is set as RB+R7, and the parallel resistance value of resistors 7 and 8 is set as R, ignoring the saturation resistance of transistor 9.
When P (<R7), the anode voltage becomes the minimum when the transistor 9 is cut off, and the lower limit value is determined by the value 1+Re/R7. Also, when the transistor 9 becomes conductive, the anode voltage becomes maximum, and the upper limit value is 1.
+Re/Rp.

With the above configuration, even if there is no information about the cathode current, the anode voltage will not run out of control and the resistance 6,
The loop is stabilized between the upper limit value and the lower limit value set by 7.8, and the traveling wave tube power amplifier can be stably operated.

〔Effect of the invention〕

As explained above, the present invention has the following features: By controlling the anode voltage so that the cathode current is constant between the upper and lower limits of the anode voltage determined by the second and third resistors, noise is eliminated during startup and shutdown transients and in the negative feedback loop. It can prevent the cathode current from becoming excessive even when the cathode current information is lost, and it can also prevent the anode voltage from running out of control, so stable operation can be expected over a long period of time, improving reliability. This has the effect of keeping the output power constant over a long period of time.

This has the advantage that the traveling wave tube power amplifier can reduce power consumption and save energy, since there is no need to provide extra output power in advance in anticipation of a decrease in output power due to aging.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Collector helix power supply, 2... Anode voltage control circuit, 3... Anode power supply, 4... Isolation transformer, 5... Negative feedback amplifier for voltage control, 6, 7.8. ... Resistor, 9... Transistor, 1°... Resistor, 11... Negative feedback amplifier for current control, 12
...Power supply for traveling wave tube power amplifier, 13... Traveling wave tube.

Claims (1)

[Claims] 1. A traveling wave tube, a first control means for controlling an anode voltage supplied to the traveling wave tube within a predetermined upper and lower limit range, and the traveling wave tube. a power supply for a traveling wave tube power amplifier having a second control means for controlling the anode voltage within the range of the predetermined upper and lower limits so that the cathode current of the power amplifier is set to a predetermined value. A traveling wave tube power amplifier characterized by: 2. The first control means includes a transistor, a first resistor, a second resistor connected in parallel to a series connection circuit of the first resistor and the collector-emitter impedance of the transistor, and the second resistor. and a third resistor connected in series to a parallel circuit of the series-connected circuit; a signal proportional to the anode voltage is divided by the third resistor and the parallel circuit, and a signal obtained at both ends of the parallel circuit is obtained. The second control circuit includes an input first negative feedback amplifier and an anode voltage control circuit that controls the anode voltage according to an output signal of the negative feedback amplifier, and the second control circuit detects the cathode current and outputs a detection signal. 2. The traveling wave tube power amplifier according to claim 1, further comprising a second negative feedback amplifier having an input terminal and an output terminal connected to the base of the transistor.