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NXP Semiconductors
JN-RM-2080
K32W module development reference manual
JN-RM-2080
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© NXP Semiconductors N.V. 2020. All rights reserved.
Reference manual
Rev. 1.0
— 27 Mar 2020
10 of 30
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The layout of the RF portions of K32W061/041 based modules is critical. It is important
that the reference designs are strictly adhered to, otherwise the following may occur:
•
Reduction in RF output
•
Excessive spurious RF outputs leading to RF compliance issues
•
Unacceptable power slope across the full channel range
•
Poor range
•
Reduced Rx sensitivity
4.4 Transmission lines
Transmission lines have several shapes such as microstrip, coplanar waveguide,
and strip-line. For BLE applications built on FR4 substrates, the types of
transmission lines typically take the form of microstrip or coplanar waveguide
(CPW). These two structures are defined by the dielectric constant of the board
material, trace width, and the board thickness between the trace and the ground.
Additionally, for CPW, the transmission line is defined by the gap between the trace
and the top edge ground plane. These parameters are used to define the
characteristic impedance of the transmission line (trace) that is used to convey the
RF energy between the radio and the antenna.
K32W061/041 has a single ended RF output with a 3-component matching
network composed of a shunt capacitor, a series inductor then another shunt
capacitor. In addition, a 0-ohm resistor has been placed between the RFIO port of
the chip and the first shunt capacitor. These elements transform the device
impedance to 50 ohms. The value of these components may vary depending on
your specific board layout. The recommended RF matching network is shown in
Avoid routing traces near or parallel to RF transmission lines or crystal signals.
Maintaining a continuous ground under an RF trace is critical to maintaining the
characteristic impedance of that trace. Avoid any routing on the ground layer that
will result in disrupting the ground under the RF traces.
Keep the RF trace as short as possible.
