Agilent Technologies 8590L Service Manual page 439

Analyzer Options and Block Diagrams
Option 190 DVB-C Service Menus
Downconverter Test
in the
Dncvrtr Test Service Menus
troubleshoot Option 190 RF Downconverter boards. Note that pressing
it also sets up the analyzer for 0 span and routes the signal path to
Option 190 board set instead of the spectrum analyzer. Thus, if a signal
was present on the analyzer input, the screen will show only the
analyzer noise floor after pressing
The Switch Control key leads to a menu which will allow you to select
one of the 5 possible paths:
1.
Spectrum Analyzer
analyzer. If you press this, the screen will show the signal (in 0 span)
if one is present on the analyzer input.
2.
Demod 8 Mz SAW
demod, 8 MHz SAW filter path.
3.
Demod 4 Mz SAW
demod, 4 MHz SAW filter path.
4.
Demod 2 Mz SAW
demod, 2 MHz SAW filter path.
5. will route the signal through the Option 190
Demod Bypass
demod, bypass (no SAW filter) path.
allows entries from 0 to 60 dB to set the amount of
DNCVRTR ATTEN
attenuation. Note that only even integer values are actually utilized
and the value is set to 30 dB when entering the downconverter test
menu.
leads to a menu which will allow you to select the 240 MHz
PLL Control
PLL oscillator frequency (based on the channel bandwidth):
1. will set it to 243.4 MHz.
PLL 8 Mz Channel
2. will set it to 246.85 MHz.
PLL 4 Mz Channel
3. will set it to 248.571 MHz.
PLL 2 Mz Channel
in the PLL Control menu leads to another menu which will
Custom Freq
allow you to set the 240 MHz oscillator to a custom frequency by
specifying the `N' and `R' words which are sent as 19 individual (serial,
MSB 1st) bits to the National semi LMX2325 PLL chip. The highest 11
bits of the `N' word is used to load the `B' register, the next 7 bits are
used to load the `A' register, the lowest order bit always a 0 for `N'
words. The highest 3 bits of the `R' word are not used, the next bit is a 1
to specify the 32/33 prescalar, the next 14 bits are used to load the `R'
register, the lowest order bit always a 1 for `R' words. The frequency is
given by:
Fo = 10 MHz * N/R where N = (32*B)+A
440
leads to a set of menus used to
Dncvrtr Test.
will route the signal back to the spectrum
will route the signal through the Option 190
will route the signal through the Option 190
will route the signal through the Option 190
Chapter 10