AD8349-EVAL Analog Devices Inc, AD8349-EVAL Datasheet - Page 16

• Manufacturer Part Number: AD8349-EVAL
• Manufacturer: Analog Devices Inc

Specifications of AD8349-EVAL

• Lead Free Status / Rohs Status: Not Compliant

AD8349
LO INPUT DRIVE LEVEL
The local oscillator inputs are designed to be driven differen-
tially. The device is specified with an LO drive level of –6 dBm.
This level was chosen to provide the best noise performance.
Increasing the LO drive level degrades sideband suppression
and increases carrier feedthrough, while improving noise
performance. Reducing the LO drive level creates the opposite
effect: improved sideband suppression and reduced carrier
feedthrough.
FREQUENCY RANGE
The LO frequency range is from 700 MHz to 2700 MHz. These
limits are defined by the nature of the LO phase splitter
circuitry. The phase splitter generates LO drive signals for the
internal mixers, which are 90 degrees out of phase from each
other. Outside of the specified frequency range (700 MHz to
2700 MHz), this quadrature accuracy degrades, resulting in
poor sideband rejection performance. Figure 45 and Figure 46
show the sideband suppression of a typical device operating
outside the specified LO frequency range. The level of sideband
suppression and degradation is also influenced by manufac-
turing process variations.
Q
I
IN
IN
49.9Ω
24.8Ω
49.9Ω
24.9Ω
866Ω
10kΩ
499Ω
499Ω
499Ω
499Ω
0.1µF
0.1µF
499Ω
499Ω
499Ω
499Ω
8
2
1
8
2
1
AD8132
AD8132
+5V
–5V
+5V
–5V
3
6
3
6
5
4
5
4
Figure 44. Single-Ended IQ Drive Circuit
0.1µF
0.1µF
0.1µF
0.1µF
Rev. A | Page 16 of 28
+
+
10µF
10µF
+
+
10µF
10µF
LO INPUT IMPEDANCE MATCHING
Single-ended LO sources are transformed into a differential
signal via a 1:1 balun (ETC1-1-13). A 200 Ω shunt resistor to
GND on each LO input on the device side of the balun reduces
the return loss for the LO input port. Because the LO input pins
are internally dc-biased, ac coupling capacitors must be used on
each LO input pin.
0.1µF
IBBN
IBBP
QBBP
QBBN
100pF
COM1 COM2 COM3
VPS1
SPLITTER
AD8349
PHASE
VPS2
Σ
100pF
VOUT
LOIP
LOIN
0.1µF