Xicom XTS-200C, Operation And Installation Manual

Page: 163 / 168

MNC-0000-015 3 of 8 Revision C
Operation Addendum, Block Upconverter
Operation Addendum, Block Upconverter
Overview
The function of the BUC (Block Upconverter) is to convert the
baseband input from a modem at an IF (intermediate frequency) to
the system transmit frequency. The BUC accepts an intermediate
frequency, mixes it with a highly stable LO (local oscillator) and
passes it through a series of circuits that filter and amplify the signal
to produce an output in the desired transmission band. The LO
frequency is derived from the reference frequency that is provided
by the baseband system. The reference frequency is typically 10 or
50 MHz and is critical to the overall system stability and phase
noise. A typical phase noise requirement for a reference source is
shown in Figure 1. The phase noise of the modem input signal at
the IF frequency also affects the system performance and needs to
be 5 to 10 dB below IESS (Intelsat Earth Station Standards) phase
noise profile for optimum performance.
See Figure 1 for a typical block diagram.
Figure 1, Typical Block Diagram of a High Power Amplifier with Block Upconverter.
Note
If the modem being used does not have the IF
multiplexed with the reference, a dixplexer is available
from Xicom (Part Number: 545-0021-001) to combine
the two signals.
Note
Xicom offers SSPA/HPA Block Upconverter options
with an internal 10 MHz reference. For these models,
the Diplexer and 10 MHz crystal are mounted inside
the SSPA/HPA enclosure. The only required input is at
the Intermediate Frequency (IF).