HIGH DATA RATE RECEIVER
HDR-4G+ USER’S MANUAL
Ref. DTU 100782
Is.Rev 3.5
Date: June 1, 2021
© Safran Data Systems – IMP000074 e14r1
This document is the property of Safran Data Systems.
It cannot be duplicated or distributed without expressed written consent.
Customized FIR Filters 3.3.2.2
General 3.3.2.2.1
The filtering is based on one FIR for I channel and one FIR for Q channel.
The FIR sampling rate is either:
twice the symbol rate (symbol rate < 480 Msps)
or four time the symbol rate (only if symbol rate < 240 Msps)
Example: for a QPSK / 100 Mbps (50 Msps) data stream, the FIR filter sampling rate can be set to 100
MHz or 200 MHz.
Two types of filters are available:
symmetrical filter: 32 taps (even symmetrical FIR) or 31 taps (odd symmetrical FIR)
asymmetrical filter: 16 taps on direct path I and Q plus 16 complex taps (Q to I and I to Q)
The I & D filter design is usually the best answer to matched filtering needs. However, custom filters
may improve the performances in some circumstances, like:
reduction of adjacent channel interferences
phase/amplitude equalization
Custom Filters Programming 3.3.2.2.2
Filter coefficients can be programmed from files on the hard disk. Up to 1000 files can be loaded to the
disk. Files are ASCII-coded and can be edited using Notepad or any other text editor.
Each file contains 16-bit data (in hexadecimal format):
Line 1: FIR type selection:
0000 for asymmetrical filter
0001 for even symmetrical filter
0002 for odd symmetrical filter
Bit 2 set to 1 enables the complex filter
Bit 3 set to 1 enables the complex filter
Line 2: Sampling rate selection:
0000 for 2 time the symbol rate
0001 for 4 time the symbol rate
Line 3: Direct FIR length
Line 4: Cross FIR length
Line 5: Cross FIR delay
Line 6: Reserved line
Line 7 to line 32: Direct coefficients (16 bit) on I
Line 33: Reserved line
Line 34 to line 41: Crossed coefficients Q to I for complex filter
Line 42: Reserved line
Line 43 to line 68: Direct coefficients (16 bit) on Q
Line 69: Reserved line
Line 70 to line 77: Crossed coefficients I to Q for complex filter
Access path to the filter files is: C:\Program Files\In-snec\crtxnt\FIR. Files are named fir_cust1 to
fir_cust1000.
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