AD9689-2000EBZ datasheet(57/134 Pages) AD

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Data Sheet

AD9689

Rev. A | Page 57 of 134

HB4 Filter Description

The first decimate by 2, half-band, low-pass, FIR filter (HB4)

uses an 11-tap, symmetrical, fixed coefficient filter impleme-

ntation that is optimized for low power consumption. The HB4

filter is only used when complex outputs (decimate by 16) or

real outputs (decimate by 8) are enabled; otherwise, it is

bypassed. Table 18 and Figure 119 show the coefficients and

response of the HB4 filter.

Table 18. HB4 Filter Coefficients

HB4 Coefficient

Number

Normalized

Coefficient

Decimal

Coefficient (15-Bit)

C1, C11

0.006042

C2, C10

C3, C9

−0.049377

−809

C4, C8

C5, C7

0.293335

4806

0.5

8192

–160

–140

–120

–100

–80

–60

–40

–20

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

NORMALIZED FREQUENCY (× Π RAD/s)

Figure 119. HB4 Filter Response

HB3 Filter Description

The second decimate by 2, half-band, low-pass, FIR filter (HB3)

uses an 11-tap, symmetrical, fixed coefficient filter implementa-

tion that is optimized for low power consumption. The HB3

filter is only used when complex outputs (decimate by 8 or 16)

or real outputs (decimate by 4 or 8) are enabled; otherwise, it is

bypassed. Table 19 and Figure 120 show the coefficients and

response of the HB3 filter.

Table 19. HB3 Filter Coefficients

HB3 Coefficient

Number

Normalized

Coefficient

Decimal Coefficient

(17-Bit)

C1, C11

0.006638

435

C2, C10

C3, C9

−0.051056

−3346

C4, C8

C5, C7

0.294418

19295

0.500000

32768

–160

–140

–120

–100

–80

–60

–40

–20

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

NORMALIZED FREQUENCY (× Π RAD/s)

Figure 120. HB3 Filter Response

HB2 Filter Description

The third decimate by 2, half-band, low-pass, FIR filter (HB2)

uses a 19-tap, symmetrical, fixed coefficient filter implementa-

tion that is optimized for low power consumption.

The HB2 filter is only used when complex or real outputs

(decimate by 4, 8, or 16) are enabled; otherwise, it is bypassed.

Table 20 and Figure 121 show the coefficients and response of

the HB2 filter.

Table 20. HB2 Filter Coefficients

HB2 Coefficient

Number

Normalized

Coefficient

Decimal Coefficient

(18-Bit)

C1, C19

0.000671

C2, C18

C3, C17

−0.005325

−698

C4, C16

C5, C15

0.022743

2981

C6, C14

C7, C13

−0.074181

−9723

C8, C12

C9, C11

0.306091

40120

C10

0.5

65536

–160

–140

–120

–100

–80

–60

–40

–20

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

NORMALIZED FREQUENCY (× Π RAD/s)

Figure 121. HB2 Filter Response

AD9689-2000EBZ Datasheet(PDF) 57 Page - Analog Devices

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