UM0934 datasheet(19/113 Pages) STMICROELECTRONICS

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UM0934

Physical layer

Doc ID 17389 Rev 2

19/113

Equation 1

Table 3 shows some conversion examples:

Fine estimation

This function provides an estimation of the signal-to-noise ratio for both channels 0 and 1,

as detected by the ST7570 at the RX_IN pin. The estimation is performed on the P_sdu

payload (304 bits). The estimated ratios are automatically provided through unsolicited

indications (CMD_DataIndication, Section 5.3.11).

In order to convert from a raw number (“value” as stored in the MIB) to an RMS voltage

value expressed in dB, use Equation 2:

Equation 2

3.6.2

Demodulation method count

For each received PHY frame, the ST7570 provides a statistic of the ways used to

demodulate each single bit of the P_SDU payload (304 bits), based on the signal quality.

During each bit time, the demodulator returns the received binary symbol on the basis of

numerical processing performed on measured data for both tones. If these data are

processed independently and a binary symbol is chosen without combining them, an “ASK”

counter (“ASK0” if the demodulated bit value is equal to 0, “ASK1” otherwise) is

incremented; however, if the bit is returned after a combination of measured data, the

“SFSK” counter is incremented.

The values of the counters are automatically provided by means of unsolicited indications

(CMD_DataIndication, Section 5.3.11).

3.6.3

Receiving gain (PGA) estimation

The internal PGA block (refer to [1]) is driven by an automatic control algorithm to find the

best gain maximizing the dynamic range of the input signal. The found PGA gain is then

written into the MIB object 000Dh (S0, N0, PGA, Section 5.3.14), and automatically

provided through unsolicited indications (CMD_DataIndication, Section 5.3.11,

Table 3.

SNR estimator values conversion

Values provided by the ST7570

RMS amplitude [dB

µV]

Name

Value

002C8Fh

114.07

002359h

90.49

002B0Ch

110.20

0023F6h

92.06

[]

100

value

VRMS

[ ]

( ) 19

log

value

SNR

−

⋅

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