ADL5371ACPZ-R7 Analog Devices Inc, ADL5371ACPZ-R7 Datasheet - Page 12

• Manufacturer Part Number: ADL5371ACPZ-R7
• Description: IC,RF Modulator,LLCC,24PIN,PLASTIC
• Manufacturer: Analog Devices Inc

Specifications of ADL5371ACPZ-R7

• Design Resources: Interfacing ADL5371 to AD9779A Dual-Channel, 1 GSPS High Speed DAC (CN0017)
• Function: Modulator
• Lo Frequency: 500MHz ~ 1.5GHz
• Rf Frequency: 500MHz ~ 1.5GHz
• P1db: 14.4dBm
• Noise Floor: -158.6dBm/Hz
• Output Power: 7.6dBm
• Current - Supply: 200mA
• Voltage - Supply: 4.75 V ~ 5.25 V
• Test Frequency: 900MHz
• Package / Case: 24-VFQFN, 24-CSP Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ADL5371ACPZ-R7TR

ADL5371
OPTIMIZATION
The carrier feedthrough and sideband suppression performance
of the ADL5371 can be improved by using optimization
techniques.
Carrier Feedthrough Nulling
Carrier feedthrough results from minute dc offsets that occur
between each of the differential baseband inputs. In an ideal
modulator, the quantities (V
are equal to zero, which results in no carrier feedthrough. In a real
modulator, those two quantities are nonzero, and, when mixed
with the LO, they result in a finite amount of carrier feedthrough.
The ADL5371 is designed to provide a minimal amount of carrier
feedthrough. Should even lower carrier feedthrough levels be
required, minor adjustments can be made to the (V
and (V
while the Q-channel offset is varied until a minimum carrier
feedthrough level is obtained. The Q-channel offset required to
achieve this minimum is held constant, while the offset on the I-
channel is adjusted until a new minimum is reached. Through
two iterations of this process, the carrier feedthrough can be
reduced to as low as the output noise. The ability to null is
sometimes limited by the resolution of the offset adjustment.
Figure 24 shows the relationship of carrier feedthrough vs. dc
offset as null.
Note that throughout the nulling process, the dc bias for the
baseband inputs remains at 500 mV. When no offset is applied,
When an offset of +V
The same applies to the Q channel inputs.
V
V
V
V
V
IOPP
IOPP
IOPP
IOPN
IOPP
QOPP
Figure 24. Typical Carrier Feedthrough vs. DC Offset Voltage
–60
–64
–68
–72
–76
–80
–84
–88
–300 –240 –180 –120
= V
− V
= 500 mV + V
− V
= 500 mV − V
− V
IOPN
IOPN
IOPN
QOPN
= 500 mV, or
= V
= V
) offsets. The I-channel offset is held constant
IOS
IOS
IOS
= 0 V
is applied to the I-channel inputs,
IOS
IOS
/2, and
/2, such that
V
P
IOPP
–60
– V
N
− V
OFFSET (µV)
0
IOPN
60
) and (V
120
QOPP
180
IOPP
− V
240
− V
QOPN
300
IOPN
)
Rev. 0 | Page 12 of 20
)
It is often desirable to perform a one-time carrier null calibra-
tion. This is usually performed at a single frequency. Figure 25
shows how carrier feedthrough varies with LO frequency over a
range of ±50 MHz on either side of a null at 940 MHz.
Sideband Suppression Optimization
Sideband suppression results from relative gain and relative
phase offsets between the I/Q channels and can be suppressed
through adjustments to those two parameters. Figure 26
illustrates how sideband suppression is affected by the gain and
phase imbalances.
Figure 26 underlines the fact that adjusting only one parameter
improves the sideband suppression only to a point, unless the
other parameter is also adjusted. For example, if the amplitude
offset is 0.25 dB, improving the phase imbalance more than 1°
does not yield any improvement in the sideband suppression. For
optimum sideband suppression, an iterative adjustment
between phase and amplitude is required.
The sideband suppression nulling can be performed either through
adjusting the gain for each channel or through the modification
of the phase and gain of the digital data coming from the digital
signal processor.
Figure 26. Sideband Suppression vs. Quadrature Phase Error for Various
Figure 25. Carrier Feedthrough vs. Frequency After Nulling at 940 MHz
–40
–45
–50
–55
–60
–65
–70
–75
–80
–85
–90
–10
–20
–30
–40
–50
–60
–70
–80
–90
890
0
0.01
2.5dB
1.25dB
0.5dB
0.25dB
0.125dB
0.05dB
0.025dB
0.0125dB
0dB
900
910
Quadrature Amplitude Offsets
0.1
920
PHASE ERROR (Degrees)
LO FREQUENCY (MHz)
930
940
1
950
960
10
970
980
990
100