Thales NSS 100S-1 Component Maintenance Manual With Illustrated Parts List page 48

2 Phase comparator
The comparator receives, at the R input, a reference clock (10
MHz); it generates on its UP and DWN outputs pulse signals that
have a variable average amplitude, based on the phase delay or
frequency delay between V and R.
UP and DWN are applied at the input of a comparator, the output
of which powers a varicap diode connected to the local oscillator;
the H1400 signal frequency generated by the local oscillator is
thus controlled by the PLL1 circuit.
3 HT100 and HCAN clock generation
The H100 signal, from the divider by 14 is available at the output
of PLL1 in order to generate, after matching:
- The HT100 clock used by the Asic T100
- The HCAN clock used by the A/D converter.
(5) Frequency conversion
This stage is designed to transform the RF frequency radio signal
into a IF intermediate frequency signal.
radio-frequency signal: 1575.42 MHz or 1227.60 MHz, and the 1400 MHz
frequency H1400 signal (OL), generated by the local oscillator.
The IF signal value is the difference between the two frequencies:
IF = 1575.42 - 1400 = 175.42 MHz or IF = 1400 - 1227.60 = 172.40 MHz.
(6) Filtering, amplification and D/A conversion of the IF signal
The IF signal from the frequency converter is matched and filtered,
before being applied to the IF amplification stage; this stage receives
an automatic gain control signal (see next paragraph).
The amplified IF signal, is applied to the analog/digital converter which
provides digital processing of the IF signal in the Asic T100 circuit.
Conversion is performed according to the rhythm of the HCAN clock,
previously computed. The 4 bit signal (CAN 0/3) available at the
converter output and the OVFL overflow bit are transmitted to the T100
circuit.
(a)
© THALES AVIONICS
COPYRIGHT SEXTANT Avionique 1995
c
The document reference is online, please check the correspondence between the online documentation and the printed version.
COMPONENT MAINTENANCE MANUAL
C17004
It receives the filtered
34-57-96
Page 26
OCT 15/01