USER’S MANUAL__________________________________________________________________
130 _________________________________________________________________ M211322EN-D
being the best overall choice. The Blackman window is useful if you are
trying to see plotted spectral components that are more than 40 dB below
the strongest signal present. It is especially useful in the Pr plot when a
long span of data are available. FIR filters designed with the Blackman
window will have greater stopband attenuation than those designed with
the Hamming window, but the wider main lobe may be undesirable. The
rectangular window is included mostly as a teaching tool, and should never
be used in an operational setting.
Settling time (to 1%) of burst frequency estimator: 5.0 sec
The burst frequency estimator uses a fourth order correlation model to
estimate the center frequency of the transmitted pulses. Each burst pulse
will typically occupy approximately one microsecond; yet the frequency
estimate feeding the AFC loop needs to be accurate to, perhaps, 10 KHz.
Obviously this accuracy can not be achieved using just one pulse.
However, several hundred of the (unbiased) individual estimates can be
averaged to produce an accurate mean. This averaging is done with an
exponential filter whose time constant is chosen here.
Limits: 0.1 s to 120 s
Enable AFC and MFC functions: YES
AFC is required in a magnetron system to maintain the fixed intermediate
frequency difference between the transmitter and the STALO. AFC is not
required in a klystron system since the transmitted pulse is inherently at the
correct frequency.
The following long list of questions appears only if AFC and MFC
functions have been enabled:
AFC Servo– 0:DC Coupled, 1:Motor/Integrator : 0
The AFC servo loop can be configured to operate with an external
Motor/Integrator frequency controller, rather than the usual direct–coupled
FM control. This type of servo loop is required for tuned magnetron
systems in which the tuning actuator is moved back and forth by a motor,
but remains fixed in place when motor drive is removed. These systems
require that the AFC output voltage (motor drive) be zero when the loop is
locked; and that the voltage be proportional to frequency error while
tracking. For details, see Section 4.2.6.1 AFC Motor/Integrator Option on
page 134.
Wait time before applying AFC: 10.0 sec
After a magnetron transmitter is first turned on, it may be several seconds
or even minutes until its output frequency becomes stable. It would not
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