DocID024318 Rev 1

13/20

AN4271

Receiver parameters

Figure 10. Sensitivity vs. data rate with 1% BER

3.2

Blocking

Blocking is a measure 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 un-modulated 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

limit for class 2 receiver at ±2 MHz is > 35 dB - 10log(BWkHz/16 kHz), at ±10 MHz it is > 60

dB - 10log(BWkHz/16 kHz).

Figure 11 shows the blocking curves with 2.4 kbps and 4.8 kbps

data rates;

Figure 12 shows the blocking curve with 38.4 kbps data rate.

The SPIRIT1 with range extender is fully compliant with ETSI class 2 receiver blocking

requirements, with a large margin.

-125

-120

-115

-110

-105

-100

-95

-90

-85

110

100

Data Rate [kbps]

Measured

ETSI Limits

GAMS060320131648FSR