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Military Standard FL5960 of the Electronic Industry of the People's Republic of China
Published on February 1, 1992
Measuring methods of travelingwave tube
China Electronics Industry Corporation
SJ20024—92
Implementation on May 1, 1992
1 Scope
1.1 Subject content
1.2 Scope of applicationbZxz.net
2 Reference documents
3 Terms, definitions and symbols...
3.1 Symbols
3.2 Terms and definitions
4 General requirements for testing
4.1 Voltage and current of the tube under test
4.2 Pulse waveform parameters Regulations
4.3 General requirements for test power supply
4.4 Control and protection system
4.5 Safety protection
5 Test methods
Test method for DC voltage and current of electrodesTest method for voltage pulse
Test method for current pulse
Test method for continuous wave power
Test method for pulse power…
Test method for excitation power and output powerTest method for power gain
Test method for gain (output power) variation with frequency
Test method for cold state and working state reflection coefficient (voltage standing wave ratio). Test method for cold loss and working loss
Test method for mismatch (short circuit) stability and power stability. Test method for phase shift
Test method for phase sensitivity
Intermodulation, amplitude modulation
Test method for phase modulation conversion coefficient and compression factor. Test method for cross modulation
Test method for noise figure
Test method for noise power spectrum density
Inter-pulse noise and intra-pulse noise (no excitation state) Test methods for modulated noise
(32)
Test methods for parasitic output ratio
Test methods for frequency modulation
Test methods for amplitude modulation
Test methods for RF pulse spectrum
Test methods for hot wire impulse current
Test methods for cathode heating time
Test methods for working ratio
Test methods for traveling wave tubes in the military standard of the People's Republic of China for the electronics industry
Measuring methods of traveling wave tube1.1 Subject content
This standard specifies the test methods for the electrical properties of traveling wave tubes. 1.2 Scope of application
This standard applies to all types of military traveling wave tubes (pulse or continuous wave, hereinafter referred to as traveling wave tubes). 2 Reference documents
GB2987--82 Parameter symbols of electron tubes
GB4597---84
GJB7-84
Terms and terms of electron tubes
Safety limit values of microwave cabinet radiation
3 Terms, definitions and symbols
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In addition to the parameter symbols and terminology specified in GB2987 and GB4597, this standard supplements the following parameter symbols, terms and definitions.
3.1 Symbols
Pulse power
RF envelope pulse width
Pulse interval time
Spurious output ratio
Harmonic output ratio
Pulse repetition period
Small signal gain
Reflection coefficient
Reflection coefficient at input end
Reflection coefficient at output end
Noise power spectrum density
Total efficiency
3.2 Terms and definitions
3.2.1 RF envelope pulse
radio pulse envelope
China Electronics Industry Corporation Issued on February 1, 1992 and implemented on May 1, 1992
The variable is the RF envelope of pulse modulation. 3.2.2 Pulse voltage pulsevoltage
The amplitude of the voltage pulse.
3.2.3 Pulse current pulsecurrent
The amplitude of the current pulse.
3.2.4 Pulse power pulsepower
The amplitude of the RF pulse power.
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3.2.5 Harmonic output poweroutputpowerofharmonicsRF output power when the frequency is an integer multiple of the fundamental frequency. 3.2.6 Harmonic output ratio (nth) ratioofharmonicstofundamental is a ratio expressed in decibels. It is the ratio of the nth harmonic output power to the fundamental output power. 3.2.7 Static power gain bandwidthbandwidthofstaticgainWhen the frequency changes slowly (such as manually changing the frequency), the power gain of the traveling wave tube is within the frequency interval within the specified range, and the operating voltage of the traveling wave tube remains unchanged.
3.2.8 Instantaneous bandwidth of power The frequency interval within the specified range of the output power of the traveling wave tube when the frequency changes fast enough without thermal drift effect. 3.2.9 Static bandwidth of power The frequency interval within the specified range of the output power of the traveling wave tube when the frequency changes slowly (such as manual frequency change). The operating voltage of the traveling wave tube is fixed.
3.2.10 Forward operation loss loss in forward operation The operating loss when the voltage is applied as specified, the traveling wave tube is in the cut-off state, and the test signal is fed from the input end. 3.2.11 Reverse operation loss loss in backward operation The operating loss when the voltage is applied as specified, the traveling wave tube is in the DC operating state and the test signal is fed from the output end. 3.2.12 Phase linearity phase linearity After subtracting the additional phase shift caused by the phase bridge element, the degree of deviation between the relationship curve between the phase shift and the frequency in the specified frequency band and a straight line or a specified curve. 3.2.13 Phase stability phase stability The maximum change slope or total phase shift between the input and output reference planes of the traveling wave tube over time within a specified time under specified conditions.
3.2.14 Compression gain drop
The effect of reduced gain of the traveling wave tube due to nonlinearity when the excitation power increases. 3.2.15 Cross modulation cross modulation The harmful modulation caused by a carrier being modulated by another carrier with a different frequency as a result of intermodulation. 3.2.16 AM amplitude modulation transfer amplitude modulation caused by cross modulation, a carrier caused by another AM carrier with a different frequency. 3.2.17 AM - AM transfer factor coefficient of amplitude modulation transfer is a ratio. The ratio of the harmful amplitude modulation depth of a carrier at the output end to the amplitude modulation depth of another carrier that causes the harmful amplitude modulation at the input end.
3.2.18 Stray noise
Spurious output is a kind of discrete harmful output which is different from white noise and has a certain degree of coherence. The harmonics of the fundamental wave do not belong to this category.
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3.2.19 Ratio of stray noise to fundamental is a ratio expressed in decibels, which is the ratio of the largest parasitic output signal coexisting with the fundamental wave power in the specified frequency band to the fundamental wave output power.
3.2.20 Total efficiency total efficiency
2nU.x.+.xI+...x.. +..
Where: P. ——The output power of the traveling wave tube; U. and I. are the voltage and current of the first electrode (including the grid, anode, tube body, slow-wave structure, collector, hot wire and other electrodes);
Pa——The excitation power of the traveling wave tube.
3.2.21 Frequency-modulated operation·(1)
A method of frequency modulation by applying a sawtooth voltage to the transit time microwave amplifier tube, such as applying the modulation voltage to the helix of the traveling wave tube.
4 General requirements for testing
General requirements for power supply, control and protection system, etc. during testing. 4.1 Voltage and current of the tube under test
Cathode voltage refers to the potential difference between the cathode and the ground, the voltage of the hot wire and titanium pump refers to the potential difference between the two ends of the hot wire and titanium pump, and the voltage of other electrodes refers to the potential difference between each electrode and the cathode. The cathode and other electrode currents refer to the currents flowing out of the cathode and into the other electrodes. 4.2 Provisions on pulse waveform parameters
When testing a pulse traveling wave tube, the various parameters of the pulse waveform shall comply with the provisions of this standard. 4.2.1 Pulse waveform
Pulse waveform is shown in Figure 1
Pulse wave tip
Pulse ripple
Figure 1 Pulse waveform
4.2.2 Pulse width
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a, voltage pulse width, current pulse width: both are calculated between two points at 70% of the pulse amplitude. b.RF envelope pulse width: When the detector is square law detection, it is calculated between two points at 50% of the pulse amplitude; when it is linear law detection, it is calculated between two points at 70.7%. 4.2.3 Pulse rise and fall time
The rise time is calculated between two points from 10% to 90% of the pulse amplitude, and the fall time is calculated between two points from 90% to 10%.
4.3 General requirements for test power supply
The dynamic internal resistance, ripple factor, stability and pulse waveform parameter values of the power supply should meet the requirements of detailed specifications. The electric meter on the power supply that directly affects the test accuracy should not be lower than level 1.5 unless otherwise specified. For the traveling wave tube working with constant voltage pulse, the voltage is maintained by the energy storage capacitor C during the pulse conduction time t. The voltage drop AU on the capacitor C during the time is abnormal.
, I (pulse current), C (capacitance), AU should meet the specified values, otherwise the power supply of the traveling wave tube should be well grounded and cannot be replaced by the neutral line of the power supply. The connecting line between the traveling wave tube and the power supply should not be too long, especially for the traveling wave tube working in pulse mode, a short connection line is required. The current of the pulse traveling wave tube is in the form of pulses, which is composed of a series of currents of different frequencies. A large distribution effect will cause self-excited oscillation and various distortions in the output spectrum.
When a traveling wave tube with high voltage and high current sparks inside the tube, if the tube body is poorly connected to the power supply, it will cause overvoltage on the line, which may damage the RF instrument or components.
A bypass capacitor should be connected in parallel at both ends of the ammeter connected in series in the pulse current loop. The product of the capacitance C and the internal resistance R of the ammeter should be no less than 10%p.
4.4 Control and protection system
The control and protection system is a key system to protect the tube under test from damage during testing. Conventional control and protection systems include current, voltage, temperature or flow of coolant and cooling air, temperature of the tube under test, etc. When the specified value is not met, the control and protection system should act within the specified time.
For some high-power tubes, some special control and protection systems are also required, such as RF power breakdown control and protection of the transmission system, reflected power control and protection, etc., which are proposed by the detailed specifications of the traveling wave tube. When a high-power traveling wave tube flashes in the tube, the energy discharged by the power supply in the tube should be limited to a certain extent to avoid damaging the traveling wave tube. The energy that the traveling wave tube can withstand should be specified in the detailed specifications. The flashover energy can be limited by using a fast-starting crowbar circuit, a current-limiting resistor that does not affect the operation of the traveling wave tube in series in the circuit, etc. The following method is used to determine the discharge energy:
Use a thin metal wire as shown in Figure 2 to short-circuit a charged capacitor. If the metal wire burns just at the capacitor charging voltage U, the melting energy of this metal wire is half CU\. (Just melting means that when U drops a little more, the metal wire does not melt. Each time a short-circuit discharge is performed, the metal wire will deform and the metal wire needs to be replaced). Use this metal wire with known melting energy to short-circuit the power supply instantaneously. If the metal wire does not melt and the power supply voltage has been cut off, it means that the power supply discharge energy is below this value, otherwise it is exceeded.
4.5 Safety protection
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Metal bracket
The thin metal wire is about 250mm long and
about a few tenths of a millimeter in diameter
High-voltage insulating rod
Metal bracket
Figure 2 Metal wire for measuring discharge energy
Safety protection during high-power traveling wave tube testing is mainly voltage, microwave radiation and X-rays. The latter two items are easily overlooked because they cannot be felt. Absorption shielding should be applied to each interface of the high-power microwave transmission system. This is not only a need for personal safety, but also a measure to avoid oscillation caused by mutual coupling between systems due to microwave leakage. The test site should be detected using a microwave field strength meter and an X-ray radiation meter, and should comply with GIB7 and relevant national safety protection regulations.
The microwave system (including instruments, components, etc.) should be well grounded. Poor grounding will produce unexpected interference signals, affect the test, and easily burn sensitive and fragile parts in microwave instruments and components. 5 Test method
5.1 Test method for electrode DC voltage and current 5.1.1
Measure the DC voltage and DC current of each electrode of the traveling wave tube. 5.1.2 Test principle
See Figure 3a and Figure 3b.
To the electrode of the traveling wave tube
TWT cathode
a, voltage measurement
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TWT power supply
Electrode voltage
To the electrode of the traveling wave tube
Figure 3 Test of DC voltage and current
5.1.3 Precautions
b. Current measurement
TWT power supply
The value of the connecting resistor when measuring voltage is determined by the measured voltage value and the range of the indicating instrument. The connecting resistor can be sealed to prevent the influence of external climate.
b. When measuring current, the internal resistance of the instrument should be small enough to have a negligible effect on the electrode potential. Calibrate with standard voltmeter and ammeter. c
5.2 Test method of voltage pulse
5.2.1 Purpose
Measure the pulse voltage and other parameter values of the pulse waveform. 5.2.2 Test Principle
Use a peak diode voltmeter to measure the pulse voltage. Use a voltage divider and an oscilloscope to measure the pulse voltage and other parameters of the pulse waveform. 5.2.2.1 Peak diode voltmeter method
a. Measure pulse voltages below 35kV (Figure 4) Figure 4 Peak diode voltmeter for measuring pulse voltages below 35kV VE-high voltage rectifier diode C-energy storage capacitor, R-non-inductive resistor; P-microammeter of appropriate range, T-filament transformer; RC≥10tSJ20024-92
Measure pulse voltages above 35kV (Figure 5) b.
Add a set of dividers to the circuit in Figure 4 so that the peak diode voltmeter can measure at an appropriate range. SH
Figure 5 Peak diode voltmeter using voltage divider R..R.-non-inductive resistor voltage divider; C..C-additional capacitor, RC, RC
Measurement of pulse voltage to eliminate the influence of pulse wave tip (Figure 6) Add an adjustable resistor R. to the circuit of Figure 4 to eliminate the influence of pulse wave tip. Adjust the value of R. during the test to make it in the appropriate range. See Figure 7.
Figure 6 Peak diode voltmeter to eliminate the influence of pulse wave tip Micrometer
Teaching
5.2.2.2 Oscilloscope display method (Figure 8)
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Correct range of R
Figure 7 Correct resistance range of R.
Use a balanced voltage divider to make the oscilloscope measure in the appropriate voltage range. R. Resistance value
Figure 8 Oscilloscope display method with balanced voltage divider R., R, Ra, R-non-inductive resistor.
This circuit is particularly suitable for accurate reproduction of pulse waveforms. It can not only be used to measure the amplitude of the pulse, but also other parameters of the pulse waveform.
R, C, is the high-voltage section of the voltage divider, R, C, and the matching components connected to the oscilloscope are the low-voltage section. The time constants of the two sections including parasitic effects must be equal.
Usually, the resistance value of R, is equal to the impedance of the coaxial cable between the voltage divider and the oscilloscope. At this time, R, = 0, R = R, Z. . The voltage divider ratio 2R/RzC2/C
The time constants of the two sections of the circuit are R, Ci and - (2)
If the voltage divider ratio is greater than (2), a smaller value of Rz can be used. At this time, R, cannot be equal to zero, R, = Z. - RzR = Z. . 8
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Voltage divider ratio=R(R+R,+R）+R(R,+R）
Time constants are R,C, and R'C2
R=R(R,+R)/(R,+R,+R,)
If R is required,>Z. Then this circuit is not applicable. 5.2.3 Notes
·（3）
a. Synthetic film (ultra-high frequency) resistors should be used for non-inductive resistors. Wirewound non-inductive resistors are not applicable. In order to minimize the voltage coefficient effect of resistors, the resistors of the voltage divider should be of the same model. b.The capacitance of the high-voltage rectifier diode is connected in parallel to the capacitive load of the pulse power supply to be measured. Choose a suitable diode to have a smaller capacitive load.
c. The dielectric of the capacitor of the voltage divider can be porcelain, resin, oil or vacuum. For the energy storage capacitor of the peak diode voltmeter, a small-value RF capacitor can be connected in parallel with it to reduce its inductive effect. d. The load resistance R of the peak diode voltmeter should be large enough to reduce the burden on the pulse source. The product of the dynamic impedance of the diode and the energy storage capacitor C is less than one-fourth of the measured pulse width. e. The input impedance of the oscilloscope should be high enough not to affect the voltage divider ratio. T. Due to the electrical resistance and capacitor at high voltage, the calibration at low level is inaccurate at high level. The component can be immersed in oil or sealed in vacuum to reduce the error. The peak diode voltmeter can be calibrated with a DC voltmeter. Use a peak diode voltmeter or a precision resistor and capacitor bridge g.
to calibrate the voltage divider.
h. A square wave generator with t, t similar to the pulse being tested can be used to check whether the line has parasitic effects that cause pulse distortion. It can also be replaced by a signal generator with a frequency ranging from DC to twice the inverse of the pulse width. 5.3 Test method for current pulses
5.3.1 Purpose
Measure the pulse current and other parameter values of the pulse waveform. 5.3.2 Test principle
Use an oscilloscope to display the waveform of the current pulse and then measure its amplitude and other parameters. 5.3.2.1 Sampling resistor method (Figure 9)
Pulse current
Figure 9 Sampling resistor method to observe the current pulse waveform R-sampling resistor, R—cable matching non-inductive resistor, R+Rm-Z9
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