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13.
Transmitter
13.1. FSK Modulation Formats
The data modulator can modulate FSK,
which is a two level FSK (Frequency Shift
Keying), or GFSK, which is a Gaussian
filtered FSK with BT = 0.5. The purpose of
the GFSK is to make a more bandwidth
efficient system as shown in Figure 20.
The modulation and the Gaussian filtering
are done internally in the chip. The
Figure 20. FSK vs. GFSK spectrum plot. 2.4 kBaud, NRZ, ±2.025 kHz frequency deviation
TX_SHAPING bit in the DEVIATION
register enables the GFSK. GFSK is
recommended for narrowband operation.
Figure 21 and Figure 22 show typical eye
diagrams for 434 MHz and 868 MHz
operation respectively.
SWRS046B
CC1020
Page 43 of 91
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