AD1890 Analog Devices, AD1890 Datasheet - Page 9

• Manufacturer Part Number: AD1890
• Description: SamplePort Stereo Asynchronous Sample Rate Converters
• Manufacturer: Analog Devices

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Figure 4. Polyphase Filter Bank Model—Conceptual Block
Diagram
SIGNAL
INPUT
PARALLEL POLYPHASE
POLYPHASE FILTER 1
POLYPHASE FILTER 2
POLYPHASE FILTER 3
POLYPHASE FILTER 4
POLYPHASE FILTER 5
POLYPHASE FILTER 6
POLYPHASE FILTER 7
POLYPHASE FILTER N-1
POLYPHASE FILTER N
FILTER BANK
AMP
Figure 3. Four Polyphase Subfilters Realigned to Coarse Time Grid
SUBFILTER COEFFICIENTS
ALIGNED TO THE LEFT
TRACKING
SAMPLE
SELECT
CIRCUIT
CLOCK
N TO 1
T sin = 1/F sin
MUX
OUTPUT
SIGNAL
TIME
–9–
PHASE
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.
DELAY = NOMINAL
DELAY = NOMINAL
DELAY = NOMINAL – .25/F sin
DELAY = NOMINAL – .5/F sin
DELAY = NOMINAL – .75/F sin
F sin /2
F sin /2
F sin /2
F sin /2
F sin /2
AD1890/AD1891
FREQ