Physical layer

ST7580

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DocID022644 Rev 2

9

Physical layer

The physical layer implemented in the ST7580 provides the following services:



Bit modulation and demodulation according to PSK and FSK schemes



Carrier selection up to 250 kHz



Bit, byte, and frame synchronization with training sequence and physical header



Signal to noise ratio (SNR) estimation.

9.1

PSK modulations

The ST7580 supports several PSK (phase shift keying) modulations with a symbol rate of

9600 baud. As all PSK modulations share the same physical frame, the receiver is able to

recognize the PSK modulation kind used by the transmitter without further settings.

9.1.1

PSK modes

The ST7580 supports several PSK modes:



Uncoded modes: B-PSK, Q-PSK, 8-PSK



Coded modes: B-PSK coded, Q-PSK coded



B-PSK coded with peak noise avoidance (PNA) algorithm.

PSK coded modes transmit, on the power line, two coded bits for each information bit (code

rate ½), halving the bit rate of the communication, but increasing the communication

robustness through error correction.

B-PSK coded with the peak noise avoidance algorithm allows an even more robust

communication and it is recommended to reject impulsive noise synchronous with the mains

period. PNA modulation requires the transmitter to be synchronized to the mains period: the

ZC_IN pin must be connected to a zero crossing detection circuit.

Table 10

summarizes all the available PSK modulations and their bit rate.

Table 10. PSK modes description

Modulation

Symbol rate [baud]

Information bits per symbol

Bit rate [bps]

B-PSK

9600

1

9600

Q-PSK

9600

2

19200

8-PSK

9600

3

28800

B-PSK coded

9600

½

4800

Q-PSK coded

9600

1

9600

B-PSK coded PNA

9600

¼

2400