AD1891 datasheet(9/20 Pages) AD

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AD1890/AD1891

REV. 0

–9–

AMP

TIME

SUBFILTER COEFFICIENTS

ALIGNED TO THE LEFT

Tsin = 1/Fsin

FREQ

Fsin/2

PHASE

DELAY = NOMINAL

DELAY = NOMINAL – .25/Fsin

DELAY = NOMINAL – .5/Fsin

DELAY = NOMINAL – .75/Fsin

Figure 3. Four Polyphase Subfilters Realigned to Coarse Time Grid

POLYPHASE FILTER 1

POLYPHASE FILTER 2

POLYPHASE FILTER 3

POLYPHASE FILTER 4

POLYPHASE FILTER 5

POLYPHASE FILTER 6

POLYPHASE FILTER 7

INPUT

SIGNAL

POLYPHASE FILTER N-1

POLYPHASE FILTER N

SELECT

N TO 1

MUX

OUTPUT

SIGNAL

SAMPLE

CLOCK

TRACKING

CIRCUIT

PARALLEL POLYPHASE

FILTER BANK

Figure 4. Polyphase Filter Bank Model—Conceptual Block

Diagram

The full set of subfilters can be considered to form a parallel

bank of “polyphase” filters which have decrementing, linear

phase group delays. All of the polyphase filters conceptually pro-

cess the input signal simultaneously, as illustrated in Figure 4, at

the input sample rate.

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