AN4110
Application note
Using the SPIRIT1 transceiver under EN 300 220 at 868 MHz
By Placido De Vita
Introduction
The SPIRIT1 is a very low power RF transceiver, intended for RF wireless applications in the
sub-1 GHz band. It is designed to operate both in the licence-free ISM and SRD frequency
bands at 169, 315, 433, 868 and 915 MHz.
This application note outlines the expected performance when using the SPIRIT1 under EN
300 220-1 (v2.3.1, 2012-02) [2] in the 863 to 870 MHz band. This band is divided into sub-
bands where the application, the maximum radiated power, the channel spacing and/or the
mitigation requirement (duty cycle etc.) are different. The maximum allowed output power is
+27 dBm (500 mW) in 869.4 to 869.65 MHz, and it is variable in the other sub-bands (see
Table 5 in ETSI EN 300 220-1 v2.3.1 [2]). This application note relates to +10 dBm (10 mW)
applications.
For details on the regulatory limits in the 863.000 - 870.000 MHz SRD frequency bands,
please refer to the ETSI EN 300 220-1 v2.3.1 [2] and ERC recommendation 70-03 [3].
These can be downloaded from www.etsi.org and www.ero.dk respectively.
July 2012
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Contents
AN4110
Contents
1
2
Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Transmitter parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1
2.2
2.3
Adjacent channel power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Modulation bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Unwanted emissions in the spurious domain . . . . . . . . . . . . . . . . . . . . . . . 9
3
Receiver parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.1
3.2
3.3
Receiver sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Blocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Receiver spurious radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4
5
6
Measurement equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
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AN4110
Application circuit
1
Application circuit
Figure 1
shows an image of the SPIRIT1 application daughterboard. The application is
made up of 2 boards: a daughterboard and a motherboard. The daughterboard includes the
SPIRIT1 with all the required external components. For correct functioning, the
daughterboard must be plugged into a motherboard (see
Figure 2)
through two header 5x2
connectors (J6 and J7).
The motherboard is provided with an STM32L152VBT6 micro to correctly program the
transceiver. The micro is programmed with firmware developed for the SPIRIT1 application.
A graphical user interface (GUI) has been developed to correctly program the SPIRIT1.
The daughterboard is provided with a 50 MHz Xtal to provide the correct oscillator to the
SPIRIT. The W-MBUS S-mode, T-mode and R-mode applications, expressly used for the
868 MHz band, can be supported by the SPIRIT. A dedicated W-MBUS application
(firmware) at 868 MHz has been developed. This document is for general purpose
applications that work in the 863.000 - 870.000 MHz bandwidth.
The SPIRIT has an internal SMPS that drastically reduces power consumption, making the
SPIRIT1 the best in class for applications on this bandwidth. The SMPS is fed from the
battery (1.8 V to 3.6 V) and provides a programmable voltage (1.4 V typically) to the device.
An SMA connector is present to connect the board at the antenna or at the instrumentation
to verify the correct functionality and verify the ETSI standard request.
A few passive parts (inductors and capacitors) are used as matching/filtering for the power
amplifier (PA) and balun network for the receiver.
To reduce application costs, the SPIRIT is designed to work without an external antenna
switch. This daughterboard is designed to show the SPIRIT functions in this condition. An
application with an antenna switch can certainly be realized, but is not described in this
document.
Figure 1.
SPIRIT1 application daughterboard
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Application circuit
Figure 2.
AN4110
SPIRIT1 application daughterboard plugged into the motherboard
Figure 3
shows the daughterboard schematic.
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AN4110
Figure 3.
Daughterboard schematic
Application circuit
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