NRF2402 Datasheet, PDF (23/31 Pages) List of Unclassifed Manufacturers – Single chip 2.4 GHz Transmitter

PRODUCT SPECIFICATION
nRF2402/nRF2402G Single Chip 2.4 GHz Radio Transmitter
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
recomme nded for maximum output power. Antennas with lower load impedance (for
example 50Ω) can be matched to nRF2402/nRF2402G by using a simple matching network.
Antenna matching networks
The recommended 50Ω matching network is shown in Figure 15. This is a low pass network
improving higher harmonic suppression.
VDD_PA
nRF2402
ANT2
ANT1
2.2nF 4.7pF
1.0pF
3.3nH
10nH
1.0pF ^5.6nH
4.7pF
RF output
Figure 15 Low pass antenna matching network
A somewhat simpler matching network is shown in Figure 16.
VDD_PA
nRF2402
ANT2
ANT1
2.2nF
4.7pF
22nH
1.0pF
3.6nH
1.0pF
RF output
Cout
1.5pF
Figure 16 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.
Nordic Semiconductor ASA - Vestre Rosten 81, N-7075 Tiller, Norway - Phone [phone] - Fax [phone]
Revision: 2.0
Page 23 of 31
April 2005