STW81103 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'STW81103' PDF : 53 Pages View PDF
Application information
STW81103
Alternatively, you can combine the two outputs in other ways. A first topology for the direct
output (2.5 to 5.0 GHz) is suggested in Figure 29. It basically consists of a simple LC balun
and a matching network to adapt the output to a 50Ω load. The two LC networks shift output
signal phase of -90° and +90°, thus combining the two outputs. This topology, designed for a
center frequency of 4 GHz, is intrinsically narrow-band since the LC balun is tuned at a
single frequency. If the application requires a different sub-band, the LC combiner can be
easily tuned to the frequency of interest.
Figure 29. LC lumped balun and matching network (MATCH_LC_LUMP_4G.dsn)
Vcc
50 ohm
RFOUTP
1.9nH
0.8pF
1.9nH
0.8pF 2.5pF
RFOUTN
50 ohm
1.9nH
1.9nH
0.8pF
0.8pF
50 ohm
Vcc
The 1.9 nH shunt inductor works as a DC feed for one of the open collector terminals as well
as a matching element along with the other components. The 1.9 nH series inductors are
used to resonate the parasitic capacitance of the chip.
For optimum output matching, it is recommended to use 0402 Murata or AVX capacitors and
0403 or 0604 HQ Coilcraft inductors. It is also advisable to use short interconnection paths
to minimize losses and undesired impedance shift.
An alternative topology that permits a more broadband matching as well as balanced to
unbalanced conversion, is shown in Figure 30.
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