PRODUCT SPECIFICATION
nRF2402 Single Chip 2.4 GHz Radio Transmitter
Nordic Semiconductor ASA - Vestre Rosten 81, N-7075 Tiller, Norway - Phone +4772898900 - Fax +4772898989
Revision: 2.2 Page 24 of 33 May 2006
PERIPHERAL RF INFORMATION
Antenna output
The ANT1 and ANT2 output pins provide a balanced RF output to the antenna. The pins
must have a DC path to VDD_PA, either via a RF choke or via the center point in a balanced
antenna. Differential load impedance between the ANT1 and ANT2 pins, 100Ω+j175Ω, is
recommended for maximum output power. Antennas with lower load impedance (for
example 50Ω) can be matched to nRF2402 by using a simple matching network.
Antenna matching networks
The recommended 50Ω matching network is shown in Figure 14. This is a low pass network
improving higher harmonic suppression.
3.3nH
5.6nH
1.0pF
1.0pF
2.2nF 4.7pF
RF output
10nH
4.7pF
nRF2402
ANT1
ANT2
VDD_PA
Figure 14 Low pass antenna matching network
A somewhat simpler matching network is shown in Figure 15.
nRF2402
ANT1
ANT2
VDD_PA
4.7pF
3.6nH
22nH
1.0pF
1.0pF
2.2nF
Cout
1.5pF
RF output
Figure 15 High pass antenna matching network
This network utilizes one component less and uses few inductors, but performance of this
network requires very careful PCB ground plane layout. The value of capacitor C
out
is
dependent on PCB ground plane layout and parasitics in the layout, and must hence be
matched to a given application layout. The value of C
out
will typically be in the range 1.0pF –
1.8pF. C
out
must be tuned while checking that the harmonics output is below frequency
regulatory limits.
