SLWS132 Datasheet, PDF (39/46 Pages) Texas Instruments – QUAD RECEIVER CHIP

GC4014 QUAD RECEIVER CHIP
DATA SHEET REV 0.6
7.6 DAMPS APPLICATION
The chip meets the DAMPS out of band rejection requirements by using the narrow CFIR mode. The overall
response using the narrow CFIR mode and a programmable PFIR filter coefficient set targeted towards DAMPS is
shown in Figure 12, along with the out of band rejection mask for DAMPS. The in-band response matches the
desired root-raised-cosine receive filter shape to within 0.1 dB.
DAMPS Adjacent Channel Requirements
DAMPS Blocker Requirements
Figure 12. Overall Frequency Response for DAMPS
This response assumes the input sample rate is equal to 16*N*B, where N is the decimation in the CIC filter
(See Section 5.3) and B is the DAMPS symbol (baud) rate (24.3 KHz). The data is output as four complex samples
per symbol (97.2 KHz) when the PFIR is in the decimate by 2 mode (DEC_BY_4 = 0 in register 13), or is output as
two samples per symbol (24.3 KHz) when the PFIR is in the decimate by 4 mode (DEC_BY_4=1).
The programmable PFIR coefficients for the DAMPS mode are:
264, 398, 413, 286, 34, -286, -584, -761, -729, -442, 85, 766, 1451,
1954, 2086, 1708, 768, -660, -2371, -4041, -5269, -5640, -4801, -2532,
1194, 6185, 12037, 18172, 23923, 28618, 31691, 32759
GRAYCHIP, INC.
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APRIL 27, 1999
This document contains information which may be changed at any time without notice