Physical layer

ST7570

20/26

Doc ID 17526 Rev 2

9

Physical layer

The ST7570 embeds a IEC-61334-5-1 PHY layer, which is based on the S-FSK (spread

FSK) modulation technique.

9.1

S-FSK principles

The S-FSK modulation technique is aimed at strengthening the classical FSK by adding

higher robustness against narrow-band interferers typical of a spread-spectrum approach.

Non-return-to-zero (NRZ) coding is used to map the binary data “0” or “1” to sinusoidal

Figure 11.

S-FSK waveform (time domain)

that a narrow-band interferer could corrupt both carriers at the same time.

Figure 12.

S-FSK waveform (frequency domain)