Analog Devices ADRV9005 Reference Manual page 302

Reference Manual ADRV9001
PRINTED CIRCUIT BOARD LAYOUT RECOMMENDATIONS
Figure 289. 1.8V Transmitter Power-Supply Routing on the ADRV9001 Evaluation Board
Figure 290 and Figure 291 show an example of the balun feed supply designed to achieve the isolation managed in the evaluation board.
DC Balun
When using a transmitter balun able to conduct DC, use the system shown in Figure 290. Place the decoupling cap near the transmitter balun
as close as possible to the balun's DC feed pin. Its orientation is perpendicular to the ADRV9001 device so the return current avoids a ground
loop with the ground pins surrounding the receiver input. The customer card provides an option to install an RF isolation inductor, which can
provide extra isolation between the Tx1 and Tx2 balun supply feeds. A 10 µF capacitor and a 0.1 µF capacitor are helpful on the DC feed pin to
eliminate transmitter spectrum spurs and dampen the transients. Note that when using this supply approach, the series matching components
must be DC shorts. It is preferred to use 0 Ω if an inductor is not needed to match the balun impedance to the transmitter output impedance.
Figure 290. Transmitter Power Supply for a Balun with a Center Tap
Chokes
The ADRV9001 evaluation board can be configured to use a transmitter balun not capable of conducting DC current. In such a scenario, install
DC chokes as well as their decoupling capacitors, as highlighted in Figure 291. Take care to match both the chokes to avoid potential current
spikes. Difference in parameters between both the chokes can cause unwanted emission at transmitter outputs. Note that if the differential input
to the balun can create a DC short to ground (through the balun), the series matching components must be capacitors. If a short can form on
the single-ended side, the single-end series blocking element must be a capacitor.
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