DEVIATION _ E
xosc
dev
17
f
f
(8 DEVIATION _ M) 2
2
=
´
+
´
SWRS037B – JANUARY 2006 – REVISED MARCH 2015
–
It is recommended to employ an interrupt driven solution due to that when using SPI polling, there
is a small, but finite, probability that a single read from registers PKTSTATUS and TXBYTES is
being corrupt. The same is the case when reading the chip status byte. This is explained in the
CC1150 Errata Notes
Refer to the TI website for SW examples
5.9
Modulation Formats
CC1150 supports amplitude, frequency and phase shift modulation formats. The desired modulation
format is set in the MDMCFG2.MOD_FORMAT register.
Optionally, the data stream can be Manchester coded by the modulator. This option is enabled by setting
MDMCFG2.MANCHESTER_EN=1. Manchester encoding cuts the effective data rate in half, and thus
Manchester is not supported for 500 kBaud. Further note that Manchester encoding is not supported at
the same time as using the FEC/Interleaver option or when using MSK modulation.
5.9.1
Frequency Shift Keying
CC1150 has the possibility to use Gaussian shaped 2_FSK (GFSK). The 2-FSK signal is then shaped by
a Gaussian filter with BT=1, producing a GFSK modulated signal. This spectrum-shaping feature improves
adjacent channel power (ACP) and occupied bandwidth.
In “true” 2-FSK systems with abrupt frequency shifting, the spectrum is inherently broad. By making the
frequency shift “softer”, the spectrum can be made significantly narrower. Thus, higher data rates can be
transmitted in the same bandwidth using GFSK.
The frequency deviation is programmed with the DEVIATION_M and DEVIATION_E values in the
DEVIATN register. The value has an exponent/mantissa form, and the resultant deviation is given by
.
(3)
The symbol encoding is shown in
Table 5-5. Symbol Encoding for 2-FSK/GFSK
Modulation
FORMAT
SYMBOL
CODING
0
– Deviation
2-FSK/GFSK
1
+ Deviation
5.9.2
Minimum Shift Keying
When using MSK [(Identical to offset QPSK with half-sine shaping (data coding may differ)], the complete
transmission (preamble, sync word, and payload) will be MSK modulated.
Phase shifts are performed with a constant transition time. The fraction of a symbol period used to change
the phase can be modified with the DEVIATN.DEVIATION_M setting. This is equivalent to changing the
shaping of the symbol.
NOTE
When
using
MSK,
Manchester
encoding
must
be
disabled
by
setting
MDMCFG2.MANCHESTER_EN=0.
The MSK modulation format implemented in CC1150 inverts the data compared to,
for example, signal generators.
Copyright © 2006–2015, Texas Instruments Incorporated
Detailed Description
23
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