CLC5902 datasheet(16/28 Pages) NSC

16 / 28 page

Rev. 3.05 May 27, 1999

An example filter (STD F2 coefficients, see Figure 22)

with 80dB out-of-band rejection, gain of 1.00, and 0.03 dB

peak to peak passband ripple is created by this set of 32

unique coefficients:

-14, -20, 19, 73, 43, -70, -82, 84, 171, -49, -269, -

34, 374, 192, -449,

-430, 460,751, -357, -1144, 81, 1581, 443, -2026,

-1337, 2437, 2886,

-2770, -6127, 2987, 20544, 29647

A second set of F2 coefficients (GSM set, see Figure 23)

suitable for meeting the stringent wideband GSM require-

ments with a gain of 0.999 are:

-536, -986, 42, 962, 869, 225, 141, 93, -280, -708,

-774, -579, -384,

-79, 536, 1056, 1152, 1067, 789, 32, -935, -1668,

-2104, -2137, -1444,

71, 2130, 4450, 6884, 9053, 10413, 10832

The filter coefficients of both filters can be used to tailor

the spectral response to the user’s needs. For example, the

first can be loaded with the standard set to provide a flat

response through to the second filter. The latter can then

be programmed as a Nyquist (typically a root-raised-

cosine) filter for matched filtering of digital data.

The complete channel filter response for standard coeffi-

cients is shown in Figure 24. Passband flatness is shown in

Figure 25.

The complete filter response for GSM coefficients is

shown in Figure 26.

GSM Passband flatness is shown in Figure 27.

The mask shown in Figure 26 is derived from the ETSI

GSM 5.05 specifications for a normal Basestation Trans-

ceiver (BTS). For interferers, 9dB was added to the carrier

to interference (C/I) ratios. For blockers, 9dB was added to

the difference between the blocker level and 3dB above

the reference sensitivity level.

Figure 21

F1 GSM frequency response

0.1

0.2

0.3

0.4

0.5

−120

−100

−80

−60

−40

−20

Frequency Response of F1 Using GSM Set

Frequency Normalized To Filter Input Sample Rate

Figure 22

F2 STD frequency response

0.1

0.2

0.3

0.4

0.5

−100

−90

−80

−70

−60

−50

−40

−30

−20

−10

Frequency Response of F2 Using STD Set

Frequency Normalized To Filter Input Sample Rate

Figure 23

F2 GSM frequency response

0.1

0.2

0.3

0.4

0.5

−50

−45

−40

−35

−30

−25

−20

−15

−10

−5

Frequency Response of F2 Using GSM Set

Frequency Normalized To Filter Input Sample Rate

Figure 24

CIC, F1, & F2 STD frequency response

500

1000

1500

2000

2500

3000

−150

−100

−50

Combined Frequency Response of CIC/F1/F2 Using STD Set

Frequency (KHz)

FCK = 52MHz

Decimation = 192

OFS = 270.83kHz

CLC5902 Datasheet(PDF) 16 Page - National Semiconductor (TI)

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