Crest Factor Reduction Functions Cfr Mode; Test Functions - Promax MO-180 Manual De Usuario

USER'S MANUAL MO-180

4.9.2 Crest Factor Reduction functions CFR Mode

The Crest Factor Reduction (CFR) algorithm is enabled when this entry is set to
ON. This block precedes the Non-Linear Pre-distorter (NLPD).
CFR Value.
When the Crest Factor Reduction (CFR) algorithm is enabled ("LEVEL:CFR
Mode" set to ON), the IF crest factor (ratio between the peak and mean envelope
powers) of the COFDM signal can be varied between 8 and 11 dB in 0.1-dB steps.
A peak-windowing algorithm is used to minimise the negative effect clipping the
OFDM signal has on both the MER and the upper and lower adjacent channels, which
results in lower MER and lower Adjacent Channel Rejection (ACR), both measured in
dB.
When the CFR algorithm is disabled ("LEVEL:CFR Mode" set to OFF), the crest
factor of the unclipped COFDM signal observed in practice is approximately 13 dB.
When the non-linear predistorter is enabled, the crest factor must be set to 11
dB or less so as to avoid overflow within the predistorter when using high correction
gains. A CFR of 11 dB effectively limits the maximum amplitude of the signal attacking
the RF amplifier but has a negligible impact on the MER.

4.10 TEST functions

This menu contains a series of parameters used to correctly carry out all types
of transmission tests using the MO-180 modulator.
Mode
Selects the test to be carried out. Available options are:
NONE Normal COFDM output.
CBER Inject channel bit errors to obtain a non-zero BER before the Viterbi
decoder (Channel BER, see entry "TEST:CBER value" below).
VBER Inject bit errors to obtain a non-zero BER after the Viterbi decoder
(Viterbi BER or simply BER, see entry "TEST:VBER value" below).
Blank
carriers Blank carriers starting at index Start Carrier and ending at index Stop
Carrier (see entries "TEST:Start Carrier" and "TEST:Stop Carrier"
below).
Pilots only Generate a DVB-T signal containing pilot carriers only (continual and
TPS).
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