User's Manual

USER
MANUAL
MPD-1611291-A
EXACT-V2 High End Rack Modulator / Exciter
3/10/2017
MPD-1611291-A
Page 22/94
2.6.1 Digital Adaptive Precorrection
The Digital Adaptive Precorrection (DAP) block is illustrated here below.
Figure 6: DAP integration block diagram
The DAP function is composed of Non-Linear and Linear Precorrection and a dedicated
down-converter. The down-converter receives the signal feedback after the external
amplifier (FBA_In) and after the RF filter (FBF_In). Then, a particular algorithm
processes the digital IQ samples to reduce the signal distortions at the transmitter
output.
To monitor the DAP process several statuses are available:
 MER indicative measure
 PAPR indicative measure
 Measured left and right shoulder levels
 DAP elapsed time
 DAP status: Active, Stopped by user, Stopped by timer, Failed
2.6.1.1 Non-Linear Adaptive Precorrection
EXACT-V2 performs non-linear precorrection over a 75 MHz bandwidth. The purpose of
non-linear precorrection is to correct the distortion from the power amplifier. With the
feedback from the output amplifier, an adaptive non-linear precorrection should
automatically find the best precorrection and follow the variations of the amplifier
characteristics.
Four operating modes are available:
• STATIC (EDIT) mode: The DAP is disabled. The user can load a previous DAP
configuration to be applied to the modulator.