User's Manual

RVP8 User’s Manual
October 2005
TTY Nonvolatile Setups
3–24
3.2.6 Mb — Burst Pulse and AFC
These questions are accessed by typing “Mb”. They set the parameters that influence the phase
and frequency analysis of the burst pulse, and the operation of the AFC feedback loop.
Receiver Intermediate Frequency: 30.0000 MHz
This is the center frequency of the IF receiver and burst pulse waveform.
S With the legacy RVP7 IFD, the RVP8 can operate at an intermediate frequency
within any of the alias bands 22–32MHz, 40–50MHz, and 58–68MHz.
S With the CAT-5E IFD, the RVP8 can operate at an intermediate frequency within
any of the alias bands 8–32MHz and 40–68MHz
These bands are delineated by 4MHz safety zones on either side of integer multiples
of half the IFD’s sampling frequency. The value entered here implicitly defines the
band being used.
Limits: 6 to 72 MHz.
Primary Receiver Intermediate Frequency: 30.0000 MHz
Secondary Receiver Intermediate Frequency: 24.0000 MHz
These alternate questions will replace the previous question whenever the RVP8’s
dual-receiver mode is selected. You should enter the two intermediate frequencies
for your primary and secondary (nominally horizontal and vertical polarized)
receivers. Note that you can easily swap receiver channels merely by exchanging the
two frequency values.
IF increases for an approaching target: YES
The intermediate frequency is derived at the receiver’s front end by a microwave
mixer and sideband filter. The filter passes either the lower sideband or the upper
sideband, and rejects the other. Depending on which sideband is chosen, an increase
in microwave frequency may either increase (STALO below transmitter) or decrease
(STALO above transmitter) the receiver’s intermediate frequency. This question
influences the sign of the Doppler velocities that are computed by the RVP8.
PhaseLock to the burst pulse: YES
This question controls whether the RVP8 locks the phase of its synthesized “I” and
“Q” data to the measured phase of the burst pulse. For an operational magnetron
system this should always be “YES”, since the transmitter’s random phase must be
known in order to recover Doppler data. The “NO” option is appropriate for non
phase modulated Klystron systems in which the RVP8/IFD sampling clock is locked
to the COHO. It is also useful for bench testing in general. In these “NO” cases the
phase of “I” and “Q” is determined relative to the stable internal sampling clock in
the RVP8/IFD module.
Minimum power for valid burst pulse: –15.0 dBm
This is the minimum mean power that must be present in the burst pulse for it to be
considered valid, i.e., suitable for input into the algorithms for frequency estimation
and AFC. The reporting of burst pulse power is described in Section 4.3; the value
entered here should be, perhaps, 8 dB less. This insures that burst pulses will still be
properly detected even if the transmitter power fades slightly.