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A transmission line impedance calculator, such as TX-Line made by AWR, can be used to approximate the

dimensions for the 50 ohm transmission line. Figure 18 shows an example for two different 50 ohm

transmission lines.

W = 0.15 mm

h = 0.076 mm

G = 0.25 mm

GND stitching vias

RF GROUND

RF GROUND

RF GROUND

RF GROUND

h = 1 mm

W = 1.8 mm

MICROSTRIP

CPW Ground

Figure 18: Example cross section of two different 50 ohm transmission line

5.5 Design Check List



Antenna is placed at the edge of a PCB, preferably to a corner



Antenna has sufficient clearance area around it and it is not covered by metal



All the GND pins are connected to a solid GND plane



All the IOs are in a known state and there are no leakage paths from the IOs

o UART and SPI inputs must have external pull-up or pull-down

o P1_0 and P1_1 must have either external pull-up or pull-down or configured as output



TX power is set not higher than required for each application



By-

pass capacitor (47 uF… 100uF) is placed parallel with a coin cell battery to compensate the high

series resistance of a coin cell



Current test point is placed to measure the sleep current