Analog Devices ADRV9005 Reference Manual page 293

Reference Manual
PRINTED CIRCUIT BOARD LAYOUT RECOMMENDATIONS
RF baluns are typically used to interface single-ended signals to the differential receiver and transmitter ports. These baluns and their
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associated matching circuits affect the overall RF performance. Make every effort to optimize the component selection and placement to
avoid performance degradation. The section describes the proper matching circuit placement and routing in more detail. Please see the
respective paragraph for more information.
Use microstrip or coplanar waveguides (CPWG) for transmission lines. These structures do not require via structures that cause additional
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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 is necessary.
Design the RF line systems between the device ball pad reference plane and the balun/filter reference plane for a differential impedance
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(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. Optimize the ZDIFF to fit a narrower frequency range. It is desirable to design the lines for reasonable coupling (−10
dB to −15 dB) to promote adequate electromagnetic interference (EMI) suppression performance.
In most cases, the required board artwork stackup is going to be different than the ADRV9001 evaluation board stackup. Optimization of RF
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transmission lines specific to the desired board environment is essential to the design and layout process.
The ADRV9001 evaluation board uses microstrip lines for receiver and transmitter RF traces. Some data port signal are routed using a
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combination of microstrip lines at the bottom of the PCB and stripline traces on the internal layers due to board complexity. In general, RF
traces should avoid using vias if a direct line route is possible.
Differential lines from the balun to the RX and TX pins must be as short as possible. The length of the single-ended transmission line should
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also be short to minimize the effects of parasitic coupling.
The system designer can optimize the RF performance with the proper selection of balun, matching components, and AC-coupling
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capacitors. The external LO traces and the DEV_CLK_IN traces can require matching components as well to ensure optimal performance.
The matching network design is explained in greater detail in the respective section of this document.
RF signal path isolation is critical to achieving the level of isolation specified in the ADRV9001 data sheet. The
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the ADRV9001 Evaluation Card
analog.com
Figure 278. RF I/O, DEV_CLK, and Data Port Signal Routing Guidelines
section provides more details on proper isolation.
ADRV9001
Isolation Techniques Used on
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