NXP Semiconductors
JN-RM-2079
QN9090 module development reference manual
JN-RM-2079
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© NXP Semiconductors N.V. 2020. All rights reserved.
Reference manual
Rev. 1.0
— 17 Jan 2020
10 of 31
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.
QN9090 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 Fig 5.
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.
Fig 5. RF Matching Network
4.5 Components
All electronic components have parasitic characteristics that cause the part to act in a
non-ideal way. Typically, these effects become worse as the frequency of operation is
increased.
Controlled impedance trace
(50 ohm microstrip)
RF Match
Printed antenna
µFl connector
