Digital Set-top Box Solutions
CX24123 Demodulator and FEC Decoder
Low-power QPSK demodulator for worldwide satellite
set-top box applications
Conexant’s broadband communications portfolio includes a comprehensive
suite of semiconductor solutions that enable the digital home and information
network. The CX24123 is a DVB, DSS, and DCII compliant demodulator and
Forward Error Correction (FEC) decoder. When combined with a satellite tuner,
such as the CX24109 tuner, the CX24123 provides a complete broadband
satellite front-end solution capable of operating from 1 to 45 Msps.
The CX24123 is the ideal solution for a wide variety of applications in digital
satellite set-top box, personal computer receivers and residential gateways.
This DiSEqC™ 2.x compliant demodulator enables two-way communication
between the set-top box and peripheral satellite equipment such as Low-
Noise Block Converters (LNB) and switches.
Providing digital derotation, digital filtering, equalization, and Viterbi/Reed-
Solomon FEC, the CX24123 provides many advanced features that enhance
overall system performance. The CX24123 automatically corrects for external
quadrature gain/phase imbalances and for DC offsets. Input signal level
variations (e.g., due to rain fade) are compensated by automatic gain control
w (AGC). Frequency offsets due to inexpensive consumer LNBs are corrected
wby a robust Carrier-Tracking Loop.
wA unique feature of the CX24123 is an automatic acquisition algorithm that
.searches and acquires the carrier within a ± 10 MHz range during initial
Dacquisition and performs a smart search to reacquire the carrier during fade
aconditions. The CX24123 has integrated signal-to-noise Ratio (SNR) and Bit
taError Rate (BER) monitors for basic channel performance measurements,
Sheet4U.comwhich saves time and test equipment during production.
CX24123 Distinguishing Features
• DVB/DSS/DCII - compliant
• Symbol rates: 1 to 45 Msps
• Automatic acquisition
• Low-power design
• Internal SNR and BER monitors
• DiSEqC™ Level 2.x compatible
• Low-Noise Block Converter
• Available in both 80 and 64 pin TQFP
Part Number CX24123
Description Demodulator and FEC Decoder