Specifications

8-VSB Agile Modulator Issue 1.02 December 9, 2008 Page 18 of 29
www.technalogix.ca
Non Linear pre-correction
The modulator can perform non linear pre-correction over a 20 MHz bandwidth.
The modulator can also perform amplitude and phase correction over the full
spectrum of the signal. For these purpose two tables (AM-AM and AM-PM) of a
maximum of 16 points (abscissa and ordinate values for each point) are
downloaded in the modulator (“1S mode”). In “2S mode”, the user sets and
downloads two groups of 16 points for each table. The first group corrects the
“left” side of the spectrum and the second group corrects the “right” side of the
spectrum. The “2S” mode provides more pre-correction adjustment accuracy and
allows the opportunity to perform different pre-corrections that will have a
corresponding impact on the left and right sides of the spectrum. This has been
developed particularly to correct asymmetric shoulder levels. Each table defines
the amplitude and the phase pre-correction that will be applied on the spectrum.
The AM-AM pre-correction table defines the AM/AM curve that will be applied
across the channel spectrum. For each point, the abscissa can be defined from -
12 dB to +12 dB in 0.05 dB steps and the ordinate can be defined from -6 dB to
+6 dB in 0.05 dB steps.
The AM-PM pre-correction table defines the AM/PM curve that will be applied to
the spectrum. For each point, the abscissa can be defined from -12 dB to +12 dB
in 0.05 dB steps and the ordinate can be defined from -25° to +25° in 0.2° steps.
All 16 points are equally spaced over the useful spectrum in 1S mode and over
each left/right segment of the spectrum in 2S mode. These tables can easily be
defined by using the control software.
RF Output Signal
The main signal is available on the “RF Out”.
The centre frequency of the signal can be set from:
- 170 MHz to 240 MHz with a step of 1 Hz.
- 470 MHz to 860 MHz with a step of 1 Hz.
The user will be able to setup attenuation between 0 to 10 dB in 0.1 dB steps. An offset
gain is also available from -2 to +2 dB in 0.1 dB increments if finer adjustment is desired.
The output can be muted either by the user or by pre-determined conditions. The mute
can be direct (abrupt muting) or progressive.
A sample of the signal is available at the test point at an attenuated level of -20 dBc.