AX8052F151 datasheet(41/51 Pages) ONSEMI

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AX8052F151

The 802.15.4 is a universal DSSS mode, which can be used with any modulation or datarate as

long as it does not violate the maximum data rate of the modulation being used. Therefore the

maximum DSSS data rate is 16 kbps for FSK and 40 kbps for ASK and PSK.

6.7. RX AGC and RSSI

AX8052F151 features two receiver signal strength indicators (RSSI):

1. RSSI before the digital IF channel filter.

The gain of the receiver is adjusted in order to keep the analog IF filter output level inside

the working range of the ADC and demodulator. The register

AX5051_AGCCOUNTER

contains the current value of the AGC and can be used as an RSSI. The step size of this

RSSI is 0.625 dB. The value can be used as soon as the RF frequency generation sub-

system has been programmed.

2. RSSI behind the digital IF channel filter.

The demodulator also provides amplitude information in the

AX5051_TRK_AMPLITUDE

AX5051_AGCCOUNTER and the

AX5051_TRK_AMPLITUDE registers, a high resolution (better than 0.1dB) RSSI value

can be computed at the expense of a few arithmetic operations on the microcontroller.

Formulas for this computation can be found in the AX5051 Programming Manual.

6.8. Modulator

Depending on the transmitter settings the modulator generates various inputs for the PA:

Modulation

Bit = 0

Bit = 1

Main Lobe

Bandwidth

Max. Bitrate

ASK

PA off

PA on

BW=BITRATE

600kBit/s

FSK / MSK

∆

f=-fdeviation

∆

f=+fdeviation

BW=(1+h) ⋅BITRATE

350kBit/s

PSK

∆Φ

=00

∆Φ

=1800

BW=BITRATE

600kBit/s

= modulation index. It is the ratio of the deviation compared to the bit-rate;

fdeviation= 0.5⋅h⋅BITRATE, AX8052F151 can demodulate signals with h < 32.

ASK

= amplitude shift keying

FSK

= frequency shift keying

MSK

= minimum shift keying; MSK is a special case of FSK, where h = 0.5, and therefore

fdeviation = 0.25⋅BITRATE; the advantage of MSK over FSK is that it can be demodulated

more robustly.

PSK

= phase shift keying

OQPSK

= offset quadrature shift keying. The AX8052F151 supports OQPSK. However, unless

compatibility to an existing system is required, MSK should be preferred.

All modulation schemes are binary.

AX8052F151 Datasheet(PDF) 41 Page - ON Semiconductor

AX8052F151 Datasheet(HTML) 41 Page - ON Semiconductor

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