AN4305 Datasheet, PDF (13/20 Pages) STMicroelectronics – Using the SPIRIT1 transceiver with range extender

AN4305
3
Receiver parameters
Receiver parameters
All the measurement reported here are measured with the following parameters: T_C = 25 °C,
V_DD = 3.3 V, f = 169.400 MHz.
The family of short range radio devices is divided into three receiver categories, each having
a set of relevant receiver requirements and minimum performance criteria. The set of
receiver requirements depends on the choice of receiver category by the equipment
provider. The SPIRIT1 is a transceiver that meets the requirements of receiver category 2,
which means medium reliable SRD communication media that can cause inconvenience to
persons, which cannot simply be overcome by other means.
The main parameters that have to be measured for the category 2 devices are the
sensitivity, the blocking and the receiver spurious radiation.
3.1
Receiver sensitivity
Receiver sensitivity is the minimum level of the signal at receiver input, produced by a
carrier at the nominal frequency of the receiver, modulated with the normal test signal
modulation, which produces performance of a bit error rate (BER) of 10-2 without correction.
Under normal test conditions, the value of the maximum usable sensitivity for 25 kHz
channel spacing equipment with a 16 kHz bandwidth shall not exceed -107 dBm. If the RX
bandwidth is not 16 kHz, the sensitivity limit is modified according to the following formula:
Equation 1
The measurement is performed using an RF signal source generator centered at the same
receiver frequency as the desired modulation signal. The demodulated data and clock are
taken from the SPIRIT1 receiver and sent to the same generator to do the BER
measurement. The generator signal level is reduced until a BER of 1% is obtained.
To reduce power consumption, an internal SMPS is integrated in the SPIRIT1. Figure 13
demonstrates the ETSI 1% BER sensitivity limit (red line) and the SPIRIT1 sensitivity for the
two investigated data rates with internal SMPS. This application note outlines the expected
performance when using the SPIRIT1 under EN 300 220-1 (v2.3.1, 2012-02) [2.] in the
169.400 - 169.475 MHz band, with channel spacing of 12.5 kHz.
The SPIRIT1 with range extender application is fully compliant with ETSI class 2 receiver
sensitivity requirements, with a large margin.
DocID024733 Rev 1
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