Promax MO-180 Manual De Usuario página 104

Point P (dB)
n
0 —11.94
1 —8.17
2 —4.93
3 —2.16
4 0.22
5 2.26
6 4.01
7 5.52
8 6.81
9 7.91
10 8.86
11 9.68
12 10.38
13 10.98
14 11.49
15 11.93
Table 1: Power abscissae and complex gain ordinates for the 16 points shown in Figure 5.
IMPORTANT NOTES:
1. When using the non-linear predistorter with high correction gains (greater
than +4.5 dB), to avoid arithmetic overflow within the predistorter we have to
limit the crest factor of the COFDM signal to 11 dB. This can be done using
the CFR block that precedes the NLPD block (see Section 4.9.2). This CF has
no negative impact on the MER of the COFDM signal which remains the same
as when the crest factor corrector is disabled. Overflow within the NLPD is dealt
with by hard-clipping the offending samples. Clipping in the NLPD block adds
more non-linearities to those already generated by the amplifier (which are in
fact the ones the NLPD is trying to counter) and should therefore be avoided at
all costs.
2. When the non-linear pre-distorter is enabled, the level at the IF output drops
3 dB. This is done to avoid saturation at the output of the last IF gain block in
the current hardware when one or more of the pre-correcting gains are greater
than approximately 3 to 4 dB. This has to be taken into account during the
obtention of the AM/AM and AM/PM curves of the RF amplifier using the RMS
test tone. If the NLPD is enabled, this tone will have 3 dB less power than when
the NLPD is disabled.
Page 34
θ
G — P (dB)
(º)
n n n
0.009 —0.06
0.023 —0.15
0.048 —0.32
0.091 —0.6
0.16 —1.04
0.26 —1.64
0.399 —2.43
0.582 —3.38
0.815 —4.49
1.105 —5.7
1.461 —7
1.9 —8.37
2.452 —9.79
3.19 —11.32
4.414 —13.22
5.762 —14.93
USER'S MANUAL MO-180
Power Real gain
abscissa
ordinate
149 32804
355 32853
748 32948
1417 33112
2451 33371
3923 33750
5873 34276
8302 34976
11173 35880
14415 37029
17938 38483
21639 40347
25417 42822
29181 46391
32851 53029
36365 61469
Imag gain
ordinate
65499
65499
65352
65188
64933
64569
64083
63468
62720
61838
60808
59602
58146
56245
53083
49151
04/2008