GC4016 datasheet(63/83 Pages) TI

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August 27, 2001

GC4016 MULTI-STANDARD QUAD DDC CHIP

DATA SHEET REV 1.0

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

7.6

EXAMPLE PFIR FILTER SETS

The spectral requirements of the PFIR filter are shown in Figure 11 in Section 3.3.6. The filters in Table 26 provide passband

bandwidths which are between 17% and 150% of the down converter channel output sample rate (before resampling).

The filter taps can be copied from this table, or requested by e-mail from tech-support@graychip.com, or downloaded from

the web at www.graychip.com. The filter taps are available in two file formats. The first, <filter_name>.taps, is an ascii listing of

the taps. The second, <filter_name>.cmd, is a command file which could be used to write the filter taps into a GC4016 chip. The

commands are formatted as “write <address> <data_byte>”, where <address> and <data_byte> are unsigned hex integers.

The recommended default filter is PFIR_80 which is flat out to 80% of the channel output’s usable bandwidth. The narrower

filters have less ripple and better out of band rejection. The wider filters (100% and 150%) are designed for the single wideband

output per chip mode where all four channels are used as one wideband channel. These modes have more ripple and less out

of band rejection than the narrowband filters.

The PFIR can also be used to apply receive filters for digital modulation formats such as QPSK, OQPSK or QAM. The most

common receive filter is the root-raised cosine (RRC) filter. A program (written in C) designed to generate RRC pfir filters is

available from graychip by e-mail or from the web. This program asks for the input sample rate, the baud rate and the desired

roll off (alpha) factor. The output is a 63 tap PFIR filter tap file and a GC4016 command file.

Table 26: Default PFIR Filters

Name

Usable

Output

Bandwidth

Passband

Cutoff

Passband

Ripple

(pk to pk)

Stopband

Start

Stopband

Rejection

near/far

PFIR Gain Applications

Taps (first 32)

pfir_17

17%

0.085

0.01dB

0.125

97dB/

120dB

3.1262

(204881)

8x oversampled

outputs.

6 17 33 49 54 33 -28 -132 -263 -380 -424

-329 -49 408 964 1461 1690 1445 597

-826 -2589 -4252 -5228 -4908 -2819 1222

7006 13910 20982 27118 31289 32767

pfir_34

34%

0.17

0.02dB

0.3

83dB/

108dB

2.2370

(146605)

4x oversampled

outputs,

2X GSM or EDGE

outputs

14 30 41 27 -29 -118 -200 -212 -95 150

435 598 475 5 -680 -1256 -1330 -653 669

2112 2880 2269 101 -2996 -5632 -6103

-3091 3666 13042 22747 30053 32767

pfir_68

68%

0.34

0.015dB

0.5

90dB/

98dB

1.2140

(79563)

2x oversampled

outputs, 1X GSM

or EDGE outputs

2 1 -11 -23 -2 45 43 -48 -117 -8 191 155

-189 -375 26 579 358 -601 -918 248 1469

618 -1680 -1995 1104 3690 845 -5354

-5506 6574 24277 32767

pfir_80

80%

0.4

0.15dB

0.5

78dB/

93dB

1.1494

(75329)

1.5x oversampled

outputs, Default

filter for most

applications

31 136 208 107 -123 -181 69 277 46 -353

-235 358 483 -246 -750 -24 967 470 -1046

-1081 884 1817 -360 -2608 -689 3365

2594 -3992 -6527 4407 23277 32767

pfir_100

100%

0.5

0.2dB

0.6

75dB/

84dB

0.9189

(60221)

Single wideband

DDC mode (See

Section 3.4.2)

-30 -141 -180 2 151 -34 -186 87 232 -171

-273 293 292 -458 -270 668 181 -916 4

1192 -325 -1479 837 1758 -1647 -2005

3015 2201 -5914 -2326 19169 32767

pfir_150

150%

0.75

0.75dB

0.82

50dB/

65dB

0.6320

(41417)

Single wideband

DDC mode (See

Section 3.4.2)

-32 -234 98 -24 -74 165 -199 138 13 -198

329 -323 149 145 -437 577 -456 73 445

-867 955 -576 -213 1138 -1778 1706 -659

-1331 3909 -6474 8360 32767

Key:

The Usable Output Bandwidth is the passband bandwidth expressed as a percentage of the DDC channel output sample rate.

The Passband Cutoff frequency is relative to the DDC channel output sample rate.

The Stopband Start frequency is relative to the DDC channel output sample rate.

The Taps are the first 32 taps of the 63 tap filter. The final 31 taps are a mirror image of the first 31 taps. The center taps are scaled to the full

scale positive value of 32767.

The Gain is PFIR_SUM/65536, the value in parenthesis is the PFIR_SUM

GC4016 Datasheet(PDF) 63 Page - Texas Instruments

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