Analog Devices AD9854 User Manual page 17

REFERENCE
CLOCK
PHASE
COMPARATOR
FILTER
AD9854
DAC OUT
DDS
TUNING
WORD
Figure 29. Programmable Fractional Divide-by-N Synthesizer
REF
CLOCK
AD9854
FILTER
DDS
TUNING
WORD
Figure 30. Agile High Frequency Synthesizer
AD8346 QUADRATURE
MODULATOR
36dB
TYPICAL
SSB
REJECTION
50Ω
V
OUT
Σ
DDS – LO LO DDS
+ LO
NOTES
1. FLIP DDS QUADRATURE SIGNALS TO SELECT ALTERNATE SIDEBAND. ADJUST DDS
SINE OR COSINE SIGNAL AMPLITUDE FOR GREATEST SIDEBAND SUPPRESSION.
DDS DAC OUTPUTS MUST BE LOW-PASS FILTERED PRIOR TO USE WITH THE AD8346.
Figure 31. Single Sideband Upconversion
TRANSFORMER-COUPLED
I
REFERENCE
OUT
CLOCK
DDS
AD9854
I
OUT
1:1 TRANSFORMER
(Mini-Circuits
Figure 32. Differential Output Connection for Reduction of Common-Mode Signals
Rev. E | Page 17 of 52
RF
FREQUENCY
OUT
LOOP
VCO
FILTER
REF CLK IN
PROGRAMMABLE
DIVIDE-BY-N FUNCTION
48
(WHERE N = 2 /TUNING WORD)
FREQUENCY
PHASE LOOP
VCO
COMPARATOR FILTER
DIVIDE-BY-N
COSINE (DC TO 70MHz)
LO
90
AD9854
PHASE 0.8 TO
QUADRATURE
SPLITTER 2.5GHz
DDS
0
LO
SINE (DC TO 70MHz)
DIFFERENTIAL
OUTPUT
FILTER
50Ω
50Ω
®
T1-1T)
RF
OUT
AD9854