ax5042-1 AXSEM, ax5042-1 Datasheet - Page 27

• Manufacturer Part Number: ax5042-1
• Description: Rf Transceiver
• Manufacturer: AXSEM

802.15.4 (ZigBee)
802.15.4 uses binary phase shift keying (PSK) with 300 kbit/s (868 MHz band) or 600 kbit/s (915
MHz band) on the radio. The usable bit rate is only a 15
spreading function in the transmitter expands the user bit rate by a factor of 15, to make the
transmission more robust. The despreader function of the receiver undoes that.
In 802.15.4 mode, the
according to the 802.15.4 specification. In receive mode, the framing unit will also
automatically search for the 802.15.4 preamble, meaning that no interrupts will have to be
serviced by the micro-controller until a packet start is detected.
5.12. RX AGC and RSSI
AX5042
Version 2.2
1. RSSI before the digital IF channel filter.
2. RSSI behind 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
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.
The demodulator also provides amplitude information in the
combining both the
(better than 0.1 dB) RSSI value can be computed at the expense of a few arithmetic
operations on the micro-controller. Formulas for this computation can be found in the
AX5042
features two receiver signal strength indicators (RSSI):
Programming Manual.
AX5042
AGCCOUNTER
framing unit performs the spreading and despreading function
and the
TRKAMPL
th
of the radio bit rate, however. A
registers, a high resolution
TRKAMPL
Circuit Description
AGCCOUNTER
Datasheet AX5042
register. By
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