Analog Devices ADRV9001 User Manual page 210

UG-1828
RF baluns are typically used to interface single-ended signals to the differential receiver and transmitter ports. These baluns and
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their associated matching circuits affect overall RF performance. Every effort should be made to optimize the component selection
and placement to avoid performance degradation. The RF Port Interface Information section describes proper matching circuit
placement and routing in more detail. Please refer to that paragraph for more information.
Use microstrip or coplanar waveguides (CPWG) for transmission lines. These structures do not require via structures that cause
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additional impedance discontinuities that vary across frequency. For Rx1B and Rx2B, receiver ports, which do not have balls on the
perimeter of the BGA, a via structure such as stripline may be necessary.
Design the RF line systems between the device ball pad reference plane and the balun/filter reference plane for a differential
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impedance (ZDIFF) of 100 Ω for the receivers and 50 Ω for the transmitters. This is a compromise impedance with respect to
frequency and a good starting point for design. The ZDIFF can be optimized to fit a narrower frequency range. It is desirable to
design the lines for reasonable coupling (−10 dB to −15 dB) to promote adequate EMI suppression performance.
In most cases, the required board artwork stack-up is going to be different than the ADRV9001 evaluation board stack-up.
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Optimization of RF transmission lines specific to the desired board environment is essential to the design and layout process.
The ADRV9001 evaluation board uses microstrip lines for Rx and Tx RF traces. Some data port signal are routed using a
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combination of microstrip lines on the bottom of the PCB and stripline traces on internal layers due to board complexity. In general,
RF traces should not use vias unless a direct line route is not possible.
Figure 191. RF I/O, DEV_CLK, and Data Port Signal Routing Guidelines
Rev. PrA | Page 210 of 253
Preliminary Technical Data