GC4014 datasheet(37/46 Pages) TI

37 / 46 page

GRAYCHIP, INC.

- 32 -

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

7.5

GSM APPLICATION

The chip meets the stringent GSM 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 GSM

is shown in Figure 11, along with GSM’s out of band rejection mask. In band ripple is 0.2 dB (peak to peak).

Figure 11. Overall Frequency Response for GSM

This response assumes the input sample rate is equal to 8*N*B, where N is the decimation in the CIC filter

(See Section 5.3) and B is the GSM bit rate (270.833 KHz). The data is output as two complex samples per bit

(541.667 KHz) when the PFIR is in the decimate by 2 mode (DEC_BY_4 = 0 in register 13), or is output as one

sample per bit (270.833 KHz) when the PFIR is in the decimate by 4 mode (DEC_BY_4=1).

The programmable PFIR coefficients for the GSM mode are:

1007, -1853, 79, 1807, 1633, 423, 265, 175, -527, -1331, -1454, -1087,

-721, -149, 1008, 1985, 2164, 2005, 1483, 61, -1756, -3134, -3953,

-4016, -2714, 134, 4003, 8361, 12934, 17009, 19565, 20353

GSM Adjacent Channel Requirements

GSM Blocker Requirements

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