Direct-Tie Implementation; Figure 9-11: Rf Switch, Double Pa Operation; Figure 9-12: Rf Switch, Single Pa Operation (High Power Pa Example); Figure 9-13: Single Tie Implementation: Only One Pa Used (High Power Pa Example) - Semtech LR1110 User Manual

Figure 9-11: RF Switch, Double PA Operation

9.4.3 Direct-Tie Implementation

In case of cost-sensitive application, it is possible to get rid of the RF switch, and implement a so-called direct-tie
implementation.
In such a configuration, the PA and the RX differential stages are connected as depicted in the figure hereafter. Please note
that series capacitances are required between the PA and the RX stage in order to avoid damaging the LR1110 due to
current flowing in the RX stage.
Figure 9-13: Single Tie implementation: Only one PA
Used (High Power PA Example)
Compared to the switched implementation, the direct-tie suffers a trade-off between TX efficiency and RX sensitivity. This
is unavoidable because the transmitter and receiver require different optimal impedances, which may not be
simultaneously feasible. In the case of a direct-tie, the user should expect a degradation of 2 ~ 3 dB in RX sensitivity.
LR1110
User Manual Rev.1.0
UM.LR1110.W.APP March 2020
Figure 9-12: RF Switch, Single PA Operation (High
Figure 9-14: Single Tie implementation: Both PAs
Used (High Power PA Example)
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Power PA Example)
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