Texas Instrumensts / CC2420 / BalUn

Hier das Datenblatt: 
http://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CC4QFjAB&url=http%3A%2F%2Fwww-mtl.mit.edu%2FCourses%2F6.111%2Flabkit%2Fdatasheets%2FCC2420.pdf&ei=i4eiUM2lFO324QSC6oHQAw&usg=AFQjCNFyP91bsy3Kd34oW0c2i6SV42satQ&cad=rja

Hier der englische Text dazu (den verstehe ich aufgrund meines 
schlechten Englisch aber kaum):

"The RF input/output is high impedance
and differential. The optimum differential
load for the RF port is 115+j180 Ω.
When using an unbalanced antenna such
as a monopole, a balun should be used in
order to optimise performance. The balun
can be implemented using low-cost
discrete inductors and capacitors only or
in combination with transmission lines.
Figure 3 shows the balun implemented in
a two-layer reference design. It consists of
a half wave transmission line, C81, L61,
L71 and L81. The circuit will present the
optimum RF termination to CC2420 with a
50 Ω load on the antenna connection. This
circuit has improved EVM performance,
sensitivity and harmonic suppression
compared to the design in Figure 4.
Please refer to the input/output matching
section on page 55 for more details.
The balun in Figure 4 consists of C61,
C62, C71, C81, L61, L62 and L81, and will
present the optimum RF termination to
CC2420 with a 50 Ω load on the antenna
connection. A low pass filter may be
added to add margin to the FCC
requirement on second harmonic level.
If a balanced antenna such as a folded
dipole is used, the balun can be omitted. If
the antenna also provides a DC path from
the TXRX_SWITCH pin to the RF pins,
inductors are not needed for DC bias.
Figure 5 shows a suggested application
circuit using a differential antenna. The
antenna type is a standard folded dipole.
The dipole has a virtual ground point;
hence bias is provided without
degradation in antenna performance."

Brauche dringend eure Hilfe! ;(