AD9753ASTZRL Analog Devices Inc, AD9753ASTZRL Datasheet - Page 19

• Manufacturer Part Number: AD9753ASTZRL
• Description: 12-Bit, 300 MSPS TxDAC+ DAC
• Manufacturer: Analog Devices Inc
• Series: TxDAC+®r

Specifications of AD9753ASTZRL

• Settling Time: 11ns
• Number Of Bits: 12
• Data Interface: Parallel
• Number Of Converters: 1
• Voltage Supply Source: Analog and Digital
• Power Dissipation (max): 165mW
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 48-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AD9753-EB - BOARD EVAL FOR AD9753
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

A figure of merit for wideband signal synthesis is the ratio of
signal power in the transmitted band to the power in an adja-
cent channel. In Figure 28, the adjacent channel power ratio
(ACPR) at the output of the AD9753 is measured to be 65 dB.
The limitation on making a measurement of this type is often
not the DAC but the noise inherent in creating the digital data
record using computer tools. To find how much this is limiting
the perceived DAC performance, the signal amplitude can be
reduced, as is shown in Figure 29. The noise contributed by the
DAC will remain constant as the signal amplitude is reduced.
When the signal amplitude is reduced to the level where the
noise floor drops below that of the spectrum analyzer, the
REV. B
Figure 28. Reconstructed 64-QAM Signal at a 25 MHz IF
COMMENT A: 25 MSYMBOL, 64 QAM, CARRIER = 25MHz
–100
–110
–120
–130
–30
–40
–50
–60
–70
–80
–90
START 100kHz
1
C11
MARKER 1 [T1]
RSET2
1.9k
PORT 1
PORT 2
INPUT
INPUT
FSADJ
DATA
DATA
9.71442886MHz
Figure 30. QAM Transmitter Architecture Using AD9753 and AD8343 Active Mixer
C11
–74.34dBm
0.1 F
CLK+ CLK– PLLLOCK
C0
REFIO ACOM1 ACOM DCOM
12.49MHz/
LATCHES
LATCHES
INPUT
INPUT
VBW
RBW
SWT
CH PWR
ACP UP
ACP LOW
1 [T1]
C0
12.5 s
50kHz
5kHz
Cu1
AD9753
+9.71442886MHz
PLL/DIVIDER
DVDD AVDD
RF ATT
UNIT
STOP 125MHz
–74.34dBm
–76.86dBm
–80.96dBm
–11.92dBm
DAC
I
I
OUTA
OUTB
Cu1
0dB
dBm
1RM
50
50
–19–
0.1 F
0.1 F
68
ACPR will fall off at the same rate that the signal level is being
reduced. Under the conditions measured in Figure 28, this
point occurs in Figure 29 at –10 dBFS. This shows that the
data record is actually degrading the measured ACPR by up to
10 dB.
A single-channel active mixer such as the Analog Devices AD8343
can then be used for the hop to the transmit frequency. Figure 30
shows an applications circuit using the AD9753 and the AD8343.
The AD8343 is capable of mixing carriers from dc to 2.5 GHz.
Figure 31 shows the result of mixing the signal in Figure 28 up
to a carrier frequency of 800 MHz. ACPR measured at the
output of the AD8343 is shown in Figure 31 to be 59 dB.
68
LOINPUT
Figure 29. ACPR vs. Amplitude for QAM Carrier
80
70
60
50
40
–20
INPM
INPP
AD8343 ACTIVE MIXER
M/A-COM ETC-1-1-13 WIDEBAND BALUN
–15
AMPLITUDE (dBFS)
0.1 F
0.1 F
LOIM
LOIP
–10
OUTP
OUTM
–5
AD9753
0