AN4110

Receiver parameters

Doc ID 023182 Rev 1

11/18

3

Receiver parameters

All the measurements here reported are performed with the following parameters: Tc =

25 °C, Vdd = 3.0 V, f = 868.300 MHz.

The product 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 receiver category 2. According to EN 300

220-1 (v2.3.1, 2012-02) [2], a category 2 receiver is described as “Medium reliable SRD

communication media, e.g. causing inconvenience to persons, which cannot simply be

overcome by other means”.

The main parameters that must be measured for category 2 devices are the sensitivity and

the blocking. The adjacent channel selectivity refers to receiver category 1, and so it is not

necessary for SPIRIT1 to meet this parameter.

3.1

Receiver sensitivity

The receiver sensitivity is the minimum level of the signal at the receiver input, produced by

a carrier at the nominal frequency of the receiver, modulated with the normal test signal

modulation, which produces the performance of a bit error rate (BER) of 10-2 without

correction.

Under normal test conditions, the value of the typical usable sensitivity for 25 kHz channel

spacing equipment with a 16 kHz bandwidth should 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 with the wanted modulation signal. The demodulated data and clock are

taken from the SPIRIT1 receiver and sent to the same generator to perform the BER

measurement. The generator signal level is reduced and then a BER of 1% is obtained.

To reduce the power consumption, an internal SMPS is integrated into the SPIRIT1.

Figure 10 demonstrates the ETSI 1% BER sensitivity limit (red line) and the SPIRIT1

sensitivity for different data rate with internal and external 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 863.000 - 870.000 MHz band, without defining the maximum channel

spacing. In order to show the real performance of the SPIRIT1 transceiver, different channel

spacings are shown. The test conditions are: 2-FSK modulation with 1 kHz frequency

deviation and 6 kHz channel bandwidth for the 1.2 kbps data rate, 2-FSK modulation with 20

kHz frequency deviation and 100 kHz channel bandwidth for the 38.4 kbps data rate, GFSK

(BT = 1) modulation with 127 kHz frequency deviation and 540 kHz channel bandwidth for

the 250 kbps data rate and MSK modulation with 812 kHz channel bandwidth for the 500

kbps data rate.

The SPIRIT1 is fully compliant with the ETSI category 2 receiver sensitivity requirements

with large margin.