Receiver parameters

AN4117

14/22

Doc ID 023222 Rev 1

3

Receiver parameters

All the measurements here reported are performed with the following parameters: Tc = 25

°C, Vdd = 3.0 V, f = 434.300 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, the

blocking, and the receiver spurious radiation. The adjacent channel selectivity is referred to

receiver category 1, 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

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 a BER of 1% is obtained.

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

Figure 15 demonstrates the ETSI 1% BER sensitivity limit (red line) and the SPIRIT1

sensitivity for different data rates with SMPS. This application note outlines the expected

performance when using the SPIRIT1 under EN 300 220-1 (v2.3.1, 2012-02) [2] at 434.3

MHz, without defining the maximum channel spacing. To show the real performance of the

SPIRIT1 transceiver, different channel spacings are shown. The test conditions are:

●

2-FSK modulation, 1.2 kHz data rate, 1 kHz frequency deviation, 12.5 kHz channel

spacing

●

GFSK modulation with BT = 0.5, 2.4 kHz data rate, 2.4 kHz frequency deviation,

12.5 kHz channel spacing

●

GFSK modulation with BT = 0.5, 4.8 kHz data rate, 2.4 kHz frequency deviation,

25 kHz channel spacing