User's Manual Part 2

Driver Section - 89 -

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LBD-200C-N1 Transmitter

Product Manual

UHF – IF Upconverter sub-module

The UHF– IF Upconverter sub-module is responsible for amplifying, filtering, and in conjunction

with the second LO which enters the rear of the module, upconverting the UHF input signal. The

module houses a single upconverter board, which besides the upconverter function, has a

voltage variable attenuator for performing ALC, a detector for sensing UHF input presence, and

a sample for front panel monitoring.

The synthesizer module within the Sirius DVB-H assembly is responsible for producing the two

Local Oscillator (LO) outputs. In the following figure, application of the LO is shown. The first LO

is mixed with an intermediate frequency (IF) that is filtered to produce a second IF. This LO will

also determine the output spectrum orientation by utilizing high or low band conversion in this

stage. The second IF frequency is heterodyned with the second LO resulting in the final output

frequency. In single conversion applications the first LO is not required.

Inside the module, the UHF input signal enters the upconverter board where it is filtered and

then mixed with a 1GHz LO to produce an RF signal at 1672.5MHz. The LO signal used in the

upconversion is generated by the synthesizer within the Thales exciter. The LO frequency is

fixed and the actual channel is set by the incoming UHF frequency, for example, if the UHF is

672.5MHz the LO will be 1000MHz. This means no frequency inversion will occur in the second

conversion stage. The up-converted UHF signal is bandpass filtered to attenuate unwanted

mixing products. A notch filter provides additional attenuation to the LO.