AX5043 0 dBm / 8 mA TX and 9.5 mA RX Configuration for the 868 MHz Band

APPLICATION NOTE AND9312/D
AX5043
0 dBm / 8 mA TX and
9.5 mA RX Configuration for
the 868 MHz Band
Revision 2
2
Table of Contents
1. Introduction................................................................................................ 3
2. Hardware Configuration .............................................................................. 4
2.1. Summary of Changes vs. standard DVK-2 add-on Modules ................................. 4
2.2. RF Reference Clock ........................................................................................ 4
2.3. Antenna Interface .......................................................................................... 5
3. Software Configuration ............................................................................... 6
4. Performance ............................................................................................... 7
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Introduction
1.
Introduction
This application note describes how to use AX5043 to design a 0 dBm / 8 mA transmit
and 9.5 mA receive configuration for the 868 MHz band. Both hardware and software
configurations are discussed.
The configuration targets wide band and category 2 or 3 receiver usage as regulated by
ETSI EN 300 220-1 V2.4.1 (2012-05). Performance is given for 50 kbps FSK operation in
the 868.0 – 868.6 MHz band.
AX5043 has a differential and a single ended power amplifier (PA). To get the highest
possible output power the differential PA must be used. 0 dBm output power which is far
below the maximum possible output power can be achieved with both PAs. However,
using the single ended power amplifier allows 0 dBm output power to be achieved with
less power consumption.
The differential PA is internally multiplexed with the receive path. The single ended PA is
output on a dedicated pin and must be externally connected to the receiver if a single
antenna configuration is to be used. A low component count, purely passive configuration
to achieve this goal is presented in this application note.
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Hardware Configuration
2.
Hardware Configuration
2.1. Summary of Changes vs. standard DVK -2 add-on Modules
Module
AX5043 DVK-2b V1.4
Antenna Interface
Use configuration shown in Figure 2
RF Reference Clock
16 MHz XTAL instead of 48 MHz TCXO
Direct connection of the XTAL to the device
pins CLK16P and CLK16N without TCXO
network as shown in Figure 1
Disconnect VAUX (TCXO supply) from J2 to
avoid shorting it to GND across the XTAL
Table 1 Module changes
2.2. RF Reference Clock
16 MHz XTAL
Pin
CLK16P
Pin
CLK16N
Figure 1 XTAL configuration
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Hardware Configuration
2.3. Antenna Interface
C1
L1
50
single-ended
equipment or
antenna
L3
ANTP
C3
RX
ANTN
C2
L2
TX
L5
ANTP1
C4
L4
Figure 2 Structure of the antenna interface for a single-ended antenna and single ended internal
PA, without RX/TX switch
Frequency
Band
L1
[nH]
L2
[nH]
L3
[nH]
L4
[nH]
L5
[nH]
C1
[pF]
C2
[pF]
C3
[pF]
C4
[pF]
868 MHz
18
7.2
12
12
27
2.7
2.7
10
2.7
Table 2 Component values
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Software Configuration
3.
Software Configuration
For software setup AX-RadioLab for AX5043 V2.2 is used. Table 3 gives the register
values that were changed vs. the RadioLab generated configuration.
It is recommended to use FSK as modulation, not GFSK, as the shaping logic for the
GFSK output consumes additional current and ETSI EN 300 220-1 V2.4.1 (2012-05) wide
band regulatory requirements can easily be met with FSK.
Register
Register
Address
AX5043_TXPWRCOEFFB1
0x16A
0x16B
Output
Power
0x02
AX5043_TXPWRCOEFFB0
AX5043_F11
0xF11
XTAL config.
0x84
AX5043_POWCTRL1
0xF08
VDD_ANA
AX5043_POWCTRL0
0xF09
VDD_MODEM
Parameter
Value Value
TX
RX
0x80
0x02
0x03
0x01
Table 3 Register Settings
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Performance
4.
Performance
Measurement equipment TX
0.5 m RG-58 cable from SMA to R&S FSEB
spectrum analyzer (note 1)
Measurement equipment RX
Pair of AX5043 modules with variable
attenuation chain and shielding box
Mainboard and debug adapter
DVK-2b
Carrier Frequency
868.3 MHz
Bit rate
50 kbps
Modulation
FSK
FSK deviation (fmark-fspace)/2
h=0.667, 16.667 kHz
IDD for TX Pout = 0 dBm random data
7.8 mA (note 2)
IDD for RX
9.5 mA
VDD_IO range with Pout = 0 dBm
1.6 V – 3.6 V
-105 dBm (note 3)
RX sensitivity
Input sensitivity at PER = 1% for 868 MHz
operation, 144 bit packet data, without FEC
ETSI EN 300 220-1 V2.4.1 (2012-05)
TX : wide band operation 868.0 – 868.6
pass
RX : class 2 or 3
Table 4 Performance
Notes :
1. 0 dBm is the spectrum analyzer reading. Cable losses are not compensated
2. Without RX/TX combination Pout = 0 dBm is achieved with 300 μA less current
with the same TX network
3. Without RX/TX combination the sensitivity is 3 dB better
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