Instruction manual

Page 15
Page 15 of 74 UTY4422-001
The control system on the main board is run by the main host processor. This processor
interfaces with the COMPEL™ network as well as local users and then controls and monitors the
unit’s operations. To do its job, this processor accesses the control data streams recovered from
the main transport demultiplexer. One of these may be a conditional access data stream (if
used). The main processor sends this data to a separate secure microprocessor, which looks to
see if its unit serial number is authorized to receive the broadcast signal and, if so, recovers the
secret keys for decrypting the incoming encrypted transport stream. Meanwhile, the main host
processor also communicates with several peripheral devices. It manages the data passed
to/from the front-panel keypad controller (which lights status LED's, manages an LCD display,
and reads back keypresses). It manages two serial ports that allow for use of a terminal, modem,
printer, or auxiliary data device as well as the display and printing of local e-mail. Additionally,
it controls the L-band receiver daughtercard and any installed options Modules (such as the RF
switch).
For maximum flexibility, and to make value-added upgrades easily possible, the operating unit
software is stored in flash memory and may be dynamically replaced via the local serial port or
from the satellite network control channel.
2.3 SPECIFICATIONS
The receiver uses an integrated tuner and QPSK demodulator assembly.
2.3.1 L-Band Tuner
The tuner specifications are shown below.
Table 2. Tuner Specifications
Parameter Specification
Input Frequency Range 950 - 2150 MHz
Input Level Range -20 dBm total signal power down to -135 dBm/Hz
signal power spectral density
Maximum Aggregate Input Power -5 dBm
Input Impedance 75 ohms, unbalanced
Input VSWR < 2.5:1, typ. 2.0
Input Noise Figure 8 dB MAX at minimum input level
L.O. Leakage at Input -55 dBm
2.3.2 QPSK Demodulator
The QPSK demodulator’s input data rate is variable over the range shown in Table 3 (Page 16),
with a minimum transport-rate step size of 1 kbps. In Table 3, “Threshold Eb/No” is that value
of Eb/No at which the average number of uncorrected FEC frames exceeds one per minute.