Receiver parameters

AN4271

12/20

DocID024318 Rev 1

3

Receiver parameters

All the measurement reported here are measured with the following parameters: T

C

= 25 °C,

V

DD

= 3.3 V, f = 869.500 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 category 2 devices are sensitivity,

blocking and 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 typical 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 10

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

different data rate. This application note outlines the expected performance when using the

SPIRIT1 under EN 300 220-1 (v2.4.1, 2012-01) [

2] in the 869.400 - 869.650 MHz band, with

the channel lower than 25 kHz, or with a single channel of the 250 kHz band. Just to show

the real performance of the application, different channel spacings are shown. The test

conditions are: GFSK (BT = 0.5) modulation with 2.4 kHz frequency deviation and 8 kHz

channel bandwidth for the 2.4 kbps data rate, GFSK (BT = 0.5) modulation with 1.2 kHz

frequency deviation and 8 kHz channel bandwidth for the 4.8 kbps data rate, GFSK (BT = 1)

modulation with 20 kHz frequency deviation and 250 kHz channel bandwidth for the 38.4

kbps data rate. The sensitivity is also measured with a PER of 1%.

The SPIRIT1 is fully compliant with ETSI class 2 receiver sensitivity requirements, with a

large margin.

Sp[dBm]

10log

BW[kHz]

16

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



107

–

=