AD9854 Analog Devices, AD9854 Datasheet - Page 12

• Manufacturer Part Number: AD9854
• Description: CMOS 300 MHz Quadrature Complete-DDS
• Manufacturer: Analog Devices

AD9854
FUNDAMENTAL
Figure 26. Using an Aliased Image to Generate a High
Frequency
Figure 23. Comparator Toggle Voltage Requirement
AD9854
1200
1000
800
600
400
200
SPECTRUM
F
IMAGE
0
C
0
AD9854
– F
O
F
CLK
I
OUT
100
F
50
IMAGE
C
MINIMUM COMPARATOR
INPUT DRIVE
V
+ F
CM
O
= 0.5V
RF IN
FREQUENCY – MHz
BANDPASS
Rx
200
FILTER
VCA
Figure 25. Chip Rate Generator in Spread Spectrum Application
FINAL OUTPUT
50
SPECTRUM
300
AMPLIFIER
ADC CLOCK FREQUENCY
LOCKED TO Tx CHIP/
400
LOW-PASS
I/Q MIXER
SYMBOL/PN RATE
REFERENCE
FILTER
F
IMAGE
C
AND
CLOCK
+ F
O
BANDPASS
FILTER
500
Q
I
GENERATOR
8-/10-BIT
AD9852
–12–
CLOCK
DUAL
ADC
ADC ENCODE
INPUT
RF/IF
Q BASEBAND
I BASEBAND
Figure 27. Programmable “Fractional Divide-by-N”
Synthesizer
Figure 24. Director Quadrature Up/Down Conversion
Applications for the AD9854
CHIP/SYMBOL/PN
8
8
48
REFERENCE
RATE DATA
CLOCK
b. Direct Conversion Quadrature Upconverter
DEMODULATOR
DAC OUT
REFCLK
REFCLK
FILTER
DIGITAL
a. Quadrature Downconversion
AD9854
COMPARATOR
AD9854
AGC
AD9854
TUNING
PHASE
WORD
DDS
Rx BASEBAND
DIGITAL DATA
OUT
LPF
LPF
LPF
LPF
(WHERE N = 2
REF CLK IN
FILTER
"DIVIDE-BY-N" FUNCTION
LOOP
SIN
COS
PROGRAMMABLE
COS
SIN
LPF
LPF
CHANNEL
48
FILTERS
SELECT
/TUNING WORD)
VCO
FREQUENCY
OUT
RF
I BASEBAND
Q BASEBAND
RF OUTPUT
REV. 0