AN3213 Datasheet, PDF (51/64 Pages) STMicroelectronics – ST7570 S-FSK power line networking system-on-chip

AN3213
Application ideas
Figure 48. Scheme of principle for switched three-phase architecture
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8.2
Received signal strength indication (RSSI)
In many application fields, measuring the strength of the incoming signal is useful to:
● Evaluate the SNR (signal-to-noise ratio) at the node
● Choose the best routing through the network (if repeaters are allowed).
As explained in References 1 and 2, the ST7570 embeds estimators for signal-to-noise ratio
(SNR₀, SNR₁) values. These estimators are calculated during valid packet reception on
each S-FSK spectrum frequency f₀ and f₁. The values are notified to the external host
during each data indication message (References 2). In order to evaluate the robustness of
ST7570 embedded estimators, the setup represented in Figure 33 has been adopted and all
the estimator values extracted from received packets have been compared to the values
measured by the spectrum analyzer.
Figure 49, 50, 51 and 52 show the error bars with standard deviation for SNR₀ and SNR₁
values, compared to the measured values for 1200 and 2400 baud.
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