AN4126

Transmitter parameter

Doc ID 023299 Rev 1

17/28

Figure 11.

Spurious conducted emission above 1 GHz measurement

3.2

Part 15.247 measurement for digital modulation schemes

3.2.1

Signal bandwidth

The 6 dB channel bandwidth is defined as the difference between the upper and lower

frequencies that are -6 dB relative to the peak. The measurement is performed in conducted

mode connecting the SPIRIT1 application board to a spectrum analyzer. The RBW

(resolution bandwidth) of the spectrum must be set to about 1% of the measured 6 dB

bandwidth, the VBW (video bandwidth) must be equal or greater than the RBW. The span

must be set wide enough to capture the entire modulation envelope.

In

Figure 12 the case with 2-FSK modulation, 500 kbps data rate and 250 kHz frequency

deviation is shown. The 6 dB bandwidth is more than 500 kHz, so the SPIRIT1 is usable for

the digital modulation schemes as defined in FCC part 15.247.

AM13155v1

-70

-60

-50

-40

-30

-20

-10

0

1.000E+09

2.000E+09

3.000E+09

4.000E+09

5.000E+09

6.000E+09

7.000E+09

8.000E+09

9.000E+09

1.000E+10

Frequency [Hz]

2-FSK, 250 kbps, 127 kHz