AR 1000TP8G18 Series, Руководство по эксплуатации и обслуживанию

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Pulse Width
The Pulse Width specification (0.07-30 microseconds) defines the range of acceptable pulse widths that
must be presented at the TTL input to operate the TWTA. The maximum value (30 microseconds)
describes the greatest RF pulse width available from the TWTA. RF output pulse widths less than 0.2
microseconds can best be produced by providing a correspondingly short RF pulse at the RF input, with
timing as shown in Figure 2.
The Pulse Width Distortion specification further defines the maximum pulse width distortion at the 50%
points of the output pulse width compared to 50% points of the input pulse width when using the pulse
input. Lower distortion can be obtained with timing as shown in Figure 2.
Pulse Rate
The Pulse Rate (PRF) specification (100 kHz max.) defines the rate of the maximum continuous pulse
stream that may be fed to the TTL-level input. In other words, each succeeding TTL-level input pulse (of
a continuous stream of pulses) must begin no sooner than 100 microseconds (1/10,000 sec.) following the
beginning of the previous pulse. There is no minimum rate specification. Users should contact AR
RF/Microwave Instrumentation regarding any specific requirements they may have for non-continuous
pulse-stream applications with higher burst rates.
Duty Cycle
The Duty Cycle specification (4% max.) is an additional limitation on the TTL-level input that must be
observed by the user. This specification defines the maximum percentage of the time that the TTL-level
input can be allowed to remain positive (logical 1). For example, if the chosen PRF is 5 kHz, then the
maximum allowable TTL input pulse width is reduced to 8 microseconds (1/5,000 x .04 sec.).
Pulse Off Isolation
Pulse off isolation specifies the reduction of signal level, input to output, when the Pulse Input is not high
(i.e. in the pulse-off condition), causing the beam to be off.
Noise Power Density
Noise Power Density describes the noise level at the TWTA's output. TWTs typically produce
considerable broadband RF noise when they are operating (TTL high). When the TTL-level input is not
high, (i.e. in the pulse-off condition) the TWT noise is significantly reduced. A typical Noise Power
Density level is thus indicated.
Forward and Reflected Peak Power
AR RF/Microwave Instrumentation Pulse TWTAs feature a display for peak RF power output to
supplement the usual display for average RF power output. This display is developed from a measurement
of the peak RF and is especially convenient for setting the peak power level when using a varying duty
cycle. This feature operates when the pulse width is greater than 1 microseconds and the RF input is
present before the start of the TTL pulse.
Peak power measurements using laboratory power meters are typically accomplished by measuring the
average power and then calculating the peak power using the known duty cycle:
Peak Power = Average Power
÷
Duty Cycle.
For accurate indirect measurements of peak power, it may be desirable to measure the actual RF output
pulse width to determine the duty cycle.