|1. Signal Path
The new receivers will deliver 4-12 GHz IF, and
correlation with the old ones is limited to 4-8GHz. The upper
truncated by a filter to avoid image response at the 2nd conversion.
The process for ant #7 is no different from the others.
Four 2-4 GHz
bands are delivered to samplers #7 of the four Widex units. Of course there is no processing for the narrowband correlator.
2. Oscillators and phase issues
make use of the Dual LO2 ( fixed 8.1 and 9.9 GHz ) modules for
there are two spares already available in the lab. These modules are
DDS-controlled to compensate for the slightly different fringe rate of
the two bands. However, since a CAN interface is not
module #7 , it is preferred to have its phase and rate
to zero and to correct the values of the six others by
software. This technique has already been applied when antenna #5 was
to a 4-antenna IF processor .
The Dual LO2 modules are fed by 400
MHz, for which there is a generator in the IFP. Better than
it from there, the spare 400MHz generator, also locked on the 5 MHz,
will be used to drive module #7. A commercial synthesizer
could be used as well but probably at the expense of a lesser phase
3. Noise source
The analog response of the Strapontin channel needs to be calibrated. A
fraction of the central noise source is coupled and can be directed to
the Ant7 inputs, in a very similar way as the 6 other inputs.