User Manual

1.4.4 NON-LINEAR PRECORRECTION

Any solid-state or tube power amplifier will produce intermodulation distortion when fed by the ATSC 8-

VSB signal. Non-linear precorrection is used to compensate the effects of these distortions in order to radiate

a signal with the maximum possible MER value.

The ATSC TRANSMITTER is able to perform non-linear precorrection over a 20MHz bandwidth. For this

purpose, two tables (AM-AM and AM-PM) of maximum 16 taps are used by the modulator.

The AM-AM precorrection table defines the AM-AM curve that will be applied to the output spectrum. For

each tap, the abscissa can be defined from -12dB to +12dB by 0.1dB step and the ordinate can be defined

from -6dB to +6dB by 0.05dB step.

The AM-PM precorrection table defines the AM-PM curve that will be applied to the output spectrum. For

each tap, the abscissa can be defined from -12dB to +12dB by 0.1dB step and the ordinate can be defined

from -25 degrees to +25 degrees by 0.2 degrees step.

Up to 10 non-linear precorrection curves (10 AM-AM and 10 AM-PM tables) can be downloaded and

saved into the equipment memory. For each curve a 10-characters name is associated. By using the local or

remote control it is possible to disable the non-linear precorrection at all or activate one of the saved curves.

Besides the 10 customizable curves, a non-customizable "Null" curve is always available: the AM-AM and

AM-PM tables of this curve are filled by zeros.

1.4.5 LINEAR PRE-CORRECTION

Any output cavity filter will produce amplitude and group delay distortion over the DTMB signal generated by

the transmitter. Linear precorrection is used in order to exactly compensate these distortions in order to

generate a signal which is maximally flat both in amplitude and group delay.

The DTMB TRANSMITTER is able to perform amplitude and group delay correction over the full spectrum

of the output signal.

Up to 2 linear precorrection curves can be downloaded and saved into the equipment memory. For each

curve a 10-characters name is associated. By using the local or remote control it is possible to disable the

linear precorrection at all or activate one of the saved curve. Besides the 2 customizable curves, a non-

customizable “Null” curve is always available: the table of this curve is filled by zeroes.

1.4.6 CONTROL OF THE EQUIPMENT

The ATSC TRANSMITTER can be controlled by means of a user-friendly LCD graphical interface with a

single rotating knob for the menu navigation and for the selections or remotely through a RS232, RS485 or

TELEMEASURES port. The functions of the local and remote control are:

- Setting the operating mode of the ATSC TRANSMITTER and the associated parameters. All these parameters

are stored in a local memory, so the previous operating mode is automatically restored each time after a