Transmitter parameter

AN4126

20/28

Doc ID 023299 Rev 1

Figure 14.

Power spectral density measurement

3.2.4

Digital modulation schemes 100 kHz bandwidth of band edges

conducted emission

According to part 15.247, in any 100 kHz bandwidth outside the frequency bands in which

the spread spectrum intentional radiator is operating, the radio frequency power that is

produced by the intentional radiator must be at least 20 dB below that in the 100 kHz

bandwidth within the band that contains the highest level of the desired power. In addition,

radiated emissions which fall in the restricted bands, as defined in part 15.205, must also

comply with the radiated emission limits specified in part 15.209.

To perform these measurements, select the channels closest to the frequency band edges

at 902 MHz and 928 MHz. Set the span to be wide enough to observe the peak level of the

emission on the channel closest to the band edge as well as any modulation products that

fall outside the authorized band of operation. The RBW (resolution bandwidth) is set to 100

kHz, the RBW is set to 100 kHz or greater. The measurements are performed at 902 and

928 MHz with a data rate of 500 kbps, a frequency deviation of 250 kHz and a 2-FSK

modulation. In

Figure 15 and 16 the measured spectrums are shown. The conducted

emissions in the band edges are lower than 20 dB integrated in 100 kHz bandwidth, making

the SPIRIT1 usable for the FCC part 15.247 digital modulation scheme.

AM13158v1

-50

-40

-30

-20

-10

0

10

20

9.150E+08

9.150E+08

9.150E+08

9.151E+08

9.151E+08

9.151E+08

9.151E+08

9.151E+08

9.151E+08

9.151E+08

Frequency [Hz]

2-FSK, 500 kbps 250 kHz

Max power spectral density