Mechanical specifications, construction details

AN4426

8/18

DocID025704 Rev 1

Figure 9. EMC test setup

Basically the test consists of placing the microphone under an antenna radiating a

disturbance signal of 1 kHz AM modulated in the range [0.8, 3] GHz. The RF amplitude

differs depending on the frequency range according to the following criteria:



+33dBm in the range [0.8, 2.4]



+17dBm in the range [2.4, 3.0]

Figure 10. RF test disturbance signal

The carrier of the disturbance is 1 kHz since it is an audio signal. Hence, the RF immunity of

the microphone is evaluated by measuring the residual of the carrier at the output of the

Signal generator

RF Amplifier

EMC jig

IN

OUT

RF out

RF in

+33dBm @450,900° 1800MHz

RF antenna

Dig Mic

Quality Board

VDD

gnd

Data

CLK

DECIMATOR BOARD

PC

Attenuator+50

Ω

Termination

Amplified RF out

Labview

Routine

Power Meter

Coupler

bring out 3.3V level signals

and send them to Labview

routine

Signal generator

RF Amplifier

EMC jig

IN

OUT

RF out

RF in

+33dBm @450,900° 1800MHz

RF antenna

Dig Mic

Quality Board

VDD

gnd

Data

CLK

DECIMATOR BOARD

PC

Attenuator+50

Ω

Termination

Amplified RF out

Labview

Routine

Power Meter

Coupler

Only level shifters are used to

bring out 3.3V level signals

and send them to Labview

routine