RFM67W Datasheet, PDF (33/37 Pages) List of Unclassifed Manufacturers – ISM TRANSMITTER MODULE

RFM 67W
8.4. RFM67W Baseband Filtering
The following figure illustrates the effect of applying the baseband gaussian filtering to the modulating bitstream of the
RFM67W. This measurement was performed in the 868 MHz ISM band with the following settings: P_PGM = 17 dBm, f_RF
=
868 MHz, Df = 50 kHz and R_b = 50 kbps (implies b=2). Here we see the occupied bandwidth reduced from 500 kHz for the
unfiltered bit stream to 330 kHz with a filtering coefficient (BT) of 1. By increasing the filtering strength further to BT=0.3,
the channel bandwidth for operation in the 868 MHz ISM band is reduced to below 200 kHz.
10
0
No Filtering
'BT = 1
'BT = 0.3
-10
ETSI Limit
-20
-30
-40
-50
-60
-70
-500
-400
-300
-200
-100
0
100
200
300
400
500
Offset from Centre Frequency (kHz)
Figure 31. The Influence of Gaussian Filtering on the Modulation Bandwidth (Wideband)
8.5. Adjacent Channel Power
Modulation spectrum of the RFM67W measured in 100 Hz bandwidth is shown in the following three figures together
with the integrated adjacent channel power for the modulation settings shown in the figure caption. Please note that all
measurements were performed at 868 MHz, with an output power of 13 dBm. Please also note that the clock output was
disabled.
Page33
Tel: [phone] Fax: [phone] E-mail: [e-mail] http:/ / www.hoperf.com