GC4014 datasheet(39/46 Pages) TI

39 / 46 page

GRAYCHIP, INC.

- 34 -

APRIL 27, 1999

GC4014 QUAD RECEIVER CHIP

DATA SHEET REV 0.6

This document contains information which may be changed at any time without notice

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.

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

DAMPS Adjacent Channel Requirements

DAMPS Blocker Requirements

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