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© Semiconductor Components Industries, LLC, 2016
July, 2016 - Rev. 3
1 Publication Order Number:
AND9313/D
AND9313/D
AX5043 Use as Analog FM
Transceiver
Introduction
This application note describes how to use the AX5043 as
an analog FM half−duplex transceiver. A modified
AX−RadioLAB project, ax5043_analog_FM_demo, is used
to demonstrate FM operation.
The AX5043_analog_FM_demo Project
The AX5043_analog_FM_demo_v1.1 project is a
modified AX−RadioLAB_v2.3g project. The SLAVE
firmware demonstrates analog FM receive, whereas
MASTER firmware demonstrates analog FM transmit.
AX−RadioLAB and the AXRadioV2API provide a basic
setup, allowing to check for the AX5043 IC, to set some
general parameters (e.g. carrier frequency) and to range the
PLL.
The default configuration is for 200 kHz wideband
(broadcast) FM. For narrow band FM the following changes
should be made: The RX bandwidth should be adjusted
using AX−RadioLAB. The TX deviation should be adjusted
by changing AX5043_FSKDEV0 in COMMON/fm.c
according to the formula in “Transmit side/Software
configuration” section.
The following tables list those input parameters of
AX−RadioLAB which are relevant here and the derived
AX5043 registers relevant for FM operation.
Table 1.
Parameter Panel Comment
Ref Osc Config Pin Configuration A TCXO should be used for narrow band FM (25 kHz channels). An XTAL is
sufficient for common FM radio reception.
PA Config Pin Configuration Single ended or differential
VCO Config Pin Configuration Internal or external L, depending of carrier frequency.
Carrier frequency PHY
RFDIV PHY Depending of carrier frequency
Symbol Rate PHY AX5043_RXDATARATE is computed from this parameter. In FM RX mode this de-
termines the rate at which the baseband signal is sampled. Typically 100 kS/s.
Channel Spacing PHY
Fxtal PHY
XTALCAP PHY
Transmit Power PHY
RX Bandwidth PHY
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APPLICATION NOTE
