AN4305
Application note
Using the SPIRIT1 transceiver with range extender
under EN 300 220 at 169 MHz
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 license-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 with a
range extender under EN 300 220-1 (v2.3.1, 2012-02) [2.] in the 169.400 - 169.475 MHz
band, meter reading, tracking and tracing applications. The maximum allowed output power
in this sub-band is +27 dBm (500 mW), this application note relates to an application
designed to reach the maximum permitted power, while respecting ETSI requirements.
This application note also relates to CEN/TC 294 prEN 13757-4:2011.10 [4.] requirements
for the W-MBUS N-mode standard in the 169.400 - 169.475 MHz band.
For details on the regulatory limits in the 169.400 - 169.475 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.
October 2013
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Contents
AN4305
Contents
1
2
Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Transmitter parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1
2.2
Adjacent channel power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Unwanted emissions in the spurious domain . . . . . . . . . . . . . . . . . . . . . . . 8
3
Receiver parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1
3.2
3.3
Receiver sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Blocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Receiver spurious radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4
5
6
Measuring equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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Application circuit
1
Application circuit
Figure 1
shows the SPIRIT1 with range extender application board photo. The application is
made up of 2 boards: a daughterboard and a motherboard. The daughterboard holds the
SPIRIT1 with the circuits necessary for its function. For correct operation, the
daughterboard must be plugged into the motherboard (see
Figure 2)
by two header 5x2
connectors (J6 and J7).
The motherboard is equipped with an STM32L152VBT6 microcontroller to correctly
program the transceiver. The microcontroller is programmed with firmware developed for
the SPIRIT1 application. A graphical user interface (GUI) has been developed for
programming of the SPIRIT1.
The daughterboard includes a 25 MHz TCXO to provide the correct oscillator to the
SPIRIT1. The W-MBUS N-mode application, expressly tailored for the 169 MHz band,
requires a frequency tolerance that cannot be achieved with a crystal oscillator, so this
application board is designed with an external TCXO. Due to the TCXO power consumption,
its power on/off is controlled by a GPIO of the STM32L152VBT6 microcontroller to power on
only in the Ready, TX and RX SPIRIT1 states.
The SPIRIT1 has an internal SMPS that drastically reduce the power consumption making
the SPIRIT1 the best in class for the application on this bandwidth. The SMPS is fed from
the battery (1.8 V to 3.6 V) and provide to the device a programmable voltage (1.4 V
usually).
A few passive devices (inductors and capacitors) are used as matching/filtering for the
SPIRIT1 power amplifier (PA) and balun network for the receiver.
A SAW filter is recommended to attenuate the spurious and harmonics emissions above the
carrier frequency, which would otherwise violate spurious emissions limits under ETSI 300
220 [2.]. The SAW filter used is a Tai-Saw Technology CO., LTD. TA0437 169 MHz SAW
filter [6.].
An external FEM (front-end module) is used to improve the output power at the +27 dBm
requested. The FEM utilized is a Skyworks SKY66100 [5]. The device includes a power
amplifier (PA) capable of about +27 dBm of transmitted output power. The receive chain
consists of a low-loss single-pole, triple-throw switch, which provides an insertion loss of
approximately 0.5 dB.
A low power amplifier (LNA) is inserted in the RX path. This one, a CEL µPD5740T6N [8.], is
inserted to improve the application sensitivity.
A few passive devices (inductors and capacitors) are used as matching/filtering between the
SAW filter and PA, between the PA and switch and after the switch.
An SMA connector, after the FEM, is provided to connect the board to the antenna or to
instrumentation in order to verify correct functionality and confirm the ETSI standard
required.
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