AD9853_15 datasheet(21/31 Pages) AD

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OBSOLETE

AD9853

–21–

REV. C

FREQUENCY SCALE – f

FREQUENCY SCALED TO SYMBOL RATE

–10

–22

–34

0.1

0.2

0.3

0.4

0.5

0.6

0.7

PASSBAND DETAIL

FREQUENCY SCALE – f

FREQUENCY SCALED TO SYMBOL RATE

–20

–40

–60

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

FIR(f)

SYSuncomp(f)

SYScomp(f)

RESPONSE OF NORMAL SRRC, NORMAL SRRC + CIC, AND COMPENSATED SRRC + CIC

FIR(f)

SYSuncomp(f)

SYScomp(f)

...EXCESS BANDWIDTH FACTOR FOR SRRC FREQUENCY RESPONSE

...PORTION OF SRRC BANDWIDTH OVER WHICH APPLY CIC CORRECTION (0<

<= 1)

...BANDWIDTH OF SRRC FILTER (RELATIVE TO SYMBOLRATE)

...NUMBER OF FIR PULSE SHAPING FILTER TAPS

...SETS MAX VALUE OF FIR PULSE SHAPING FILTER BASED ON FINITE WORD SIZE

...UPSAMPLING RATIO OF FIR PULSE SHAPING FILTER (RELATIVE TO THE SYMBOL RATE)

...PROCESSING GAIN OF CIC FILTERS (USED TO CORRELATE RESULTS WITH AD9853 EVAL. BD.)

...NUMBER OF COMB/INTEGRATOR STAGES IN CIC FILTER

...UNIT DELAYS PER STAGE OF CIC FILTER

...RETURNS 1 IF a<= x <= b, 0 OTHERWISE

...RETURNS NEAREST INTEGER TO x

...RATIO TO DECIBEL CONVERSION FUNCTION

...SRRC FREQUENCY RESPONSE FUNCTION

(f IS RELATIVE TO THE SYMBOL RATE)

...Z TRANSFORM

...CIC FILTER TIME INDEX FREQUENCY RESPONSE FUNCTION

–k

H(f,R)

R M – 1

k = 0

GLOBAL DECLARATIONS

CONSTANTS:

0.5

PROC_GAIN

0.5 (1+

)

SCALE

511

TAPS

FreqScale

FUNCTIONS:

InRange (x,a,b)

a) . (x

INT(x)

floor(x + 0.5)

dB(x)

if (| x | = 0, –200, 20 log (| x |))

SRRC(f)

passband

0.5 (1 –

)

stopband

0.5 (1 +

)

1 if InRange (f, 0, stopband)

if InRange (f, 0, passband)

cos

4 .

(2 f +

– 1) if InRange (f, passband, stopband)

0 otherwise

0.9

z(f)

e2j

Figure 35. MathCad Simulation (Continued)

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