MRF24J40MB-I Datasheet, PDF (135/156 Pages) Microchip Technology – IEEE 802.15.4™ 2.4 GHz RF Transceiver

MRF24J40
4.0 APPLICATIONS
4.1 Antenna/Balun
Figure 4-1 is an example of the circuit diagram of a
balun to match to a 50Ω antenna. A balun is the imped-
ance transformer from unbalanced input of the PCB
antenna and the balanced input of the RF transceiver
(pins RFP and RFN).
Figure 4-2 shows the measured impedance of the
balun where the center of the band is very close to 50Ω.
When using low tolerance components (i.e., ±5%)
along with an appropriate ground, the impedance will
remain close to the 50Ω measurement.
FIGURE 4-1:
EXAMPLE BALUN CIRCUIT DIAGRAM
+V
C12
0.01 μF
50Ω ANT
C17
0.3 pF
L4
4.7 nH
C15
0.5 pF
C16
0.5 pF
L2
10 nH
C14
0.5 pF
L1
10 nH
L3
5.6 nH
C2
0.5 pF
RFP
RFN
FIGURE 4-2:
BALUN CIRCUIT MEASURED IMPEDANCE
© 2010 Microchip Technology Inc.
Preliminary
DS39776C-page 135