Receiver parameters

AN4110

12/18

Doc ID 023182 Rev 1

Figure 10.

Sensitivity vs. data rate with 1% BER

3.2

Blocking

Blocking is a measurement of the capability of the receiver to receive a wanted modulated

signal without exceeding a given degradation due to the presence of an unwanted input

signal at any frequency other than those of the spurious responses or the adjacent channels

or bands.

All the blocking results are measured by positioning the input power 3 dB above the

measured sensitivity limit reported in the previous paragraph with a primary signal source

generator. A second generator with an unmodulated signal is used as the interferer and

combined with the primary signal using a power combiner. The second interferer generator

is placed at the desired frequency offset and the power is increased until the BER

degradation of 1% is obtained.

ETSI specifies the blocking limits in absolute values at two points: ±2 and ±10 MHz. The

is ± 60 dB - 10log (BWkHz/16 kHz). Figure 11 shows the blocking curve with 1.2 kbps data

rate; Figure 12 shows the blocking curve with 500 kbps data rate.

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

large margin.

The adjacent channel selectivity is also defined in the ETSI EN300 220 [2] standard, a

measurement of the capability of the receiver to operate satisfactorily in the presence of an

unwanted signal, which differs in frequency from the wanted signal by an amount equal to

the adjacent channel separation for which the equipment is intended. This parameter must

be evaluated only for the device that complies with the ETSI category 1, so the SPIRIT1

does not have to be under this regulation.