Xdeaf For Reception Of Dual Polarization Data Transmission - Safran CORTEX Series User Manual

3.3.2.4

XDEAF for reception of dual polarization data transmission

In order to increase the data transmission rate in a given bandwidth, some satellites use the
polarization diversity. Two radio waves are then transmitted using orthogonal polarizations in the same
frequency channel (typically RHCP and LHCP).
If we consider one channel (one polarization), we can see that this channel has a high probability to be
perturbed by the other channel. And we can define a cross polarization discrimination coefficient as:
XPD = 10 log (Co-polar component / Cross-polar component)
In the transmission channel, several different sources of cross-polarization can occur:
on-board antenna cross-polarization
-
on-board antenna depointing
-
- propagation effect (rain, bad weather)
ground antenna low elevation
-
- ground antenna depointing
ground antenna cross-polarization
-
Typically and in case of bad conditions of transmission, XPD can be down to < 14 dB for X-band
systems and < 8 dB for K-band systems.
In order to compensate for the impact of the cross polarization effects on the data reception, the Cortex
HDR provides the XDEAF function.
The XDEAF function is a real time and automatic digital filtering which takes into account the reception
of both polarizations.
The XDEAF function can compensate for XPD down to 5 dB.
The following BER curves have been measured for a QPSK transmission at 200 Mbps using dual
polarization. The XPD coefficient is 12 dB. The gain for a BER = 10
(XDEAF disabled) and the red one (XDEAF enabled).
The following figure gives the effect of the XDEAF on the received constellation in the same previous
conditions.
© Safran Data Systems – IMP000074 e14r1
HIGH DATA RATE RECEIVER
HDR-4G+ USER'S MANUAL
This document is the property of
It cannot be duplicated or distributed without expressed written consent.
Ref. DTU 100782
Is.Rev 3.5
Date: June 1, 2021
-6
is 4 dB between the green curve
Safran Data Systems
.
Page 83