STW81101AT datasheet(34/42 Pages) STMICROELECTRONICS

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Application information

STW81101

34/42

Application information

The STW81101 features three different alternatively selectable bands: direct output (3.3 to

4.4GHz), divided by 2 (1.65 to 2.2GHz) and divided by 4 (850 to 1100MHz). In order to

achieve a suitable power level, a good matching network is needed to adapt the output

stage to a 50

Ω load. Moreover, since most of commercial RF components have single

ended input and output terminations, a differential to single ended conversion could be

required.

Below different matching configurations for the three bands are suggested as a guideline for

the design of own application board.

The user can find in the Evaluation Kit the ADS Design for each matching configuration

suggested in this section. The name of the corresponding ADS Design is reported below

each figure.

7.1

Direct Output

If a differential to single conversion is not needed it is possible to match the output buffer of

the STW81101 in the simple way shown in Figure 24.

Figure 24.

Differential/single ended output network in the 3.3 - 4.4GHz range

(MATCH_LC_LUMP_4G_DIFF.dsn)

Since most of discrete components for microwave applications are single ended, the user

can easily use one of the two outputs and terminate the other one to 50

Ω with a 3dB power

loss.

Alternatively it is possible to combine the 2 outputs in different ways. A first topology for the

direct output (3.3GHz to 4.4GHz) is suggested in Figure 25. It basically consists of a simple

LC balun and a matching network to adapt the output to a 50

Ω load. The two LC networks

shift output signal phase of -90° and +90° thus combining the 2 outputs. This topology,

designed for a center frequency of 4GHz, 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

could be easily adjusted to be tuned at the frequency of interest.

RF OUTP

RF OUTN

V CC

2nH

50 O hm

10pF

2nH

10pF

V CC

50 O hm

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