CC1150
SWRS037A Page 40 of 60
responsibility to ensure that the system complies with regulations.
24.2 Frequency Hopping and Multi-Channel Systems
The 315 MHz, 433 MHz, 868 MHz or 915 MHz
bands are shared by many systems both in
industrial, office and home environments. It is
therefore recommended to use frequency
hopping spread spectrum (FHSS) or a multi-
channel protocol because the frequency
diversity makes the system more robust with
respect to interference from other systems
operating in the same frequency band. FHSS
also combats multipath fading.
CC1150
is highly suited for FHSS or multi-
channel systems due to its agile frequency
synthesizer and effective communication
interface. Using the packet handling support
and data buffering is also beneficial in such
systems as these features will significantly
offload the host controller.
Charge pump current, VCO current and VCO
capacitance array calibration data is required
for each frequency when implementing
frequency hopping for
CC1150
. There are 3
ways of obtaining the calibration data from the
chip:
1) Frequency hopping with calibration for each
hop. The PLL calibration time is approximately
720 µs. The blanking interval between each
frequency hop is then approximately 810 µs.
2) Fast frequency hopping without calibration
for each hop can be done by calibrating each
frequency at startup and saving the resulting
FSCAL3, FSCAL2 and FSCAL1 register values
in MCU memory. The VCO capacitance
calibration FSCAL1 register value must be
found for each RF frequency to be used. The
VCO current calibration value and the charge
pump current calibration value available in
FSCAL2 and FSCAL3 respectively are not
dependent on the RF frequency, so the same
value can therefore be used for all RF
frequencies for these two registers. Between
each frequency hop, the calibration process
can then be replaced by writing the FSCAL3,
FSCAL2 and FSCAL1 register values that
corresponds to the next RF frequency. The
PLL turn on time is approximately 90 µs. The
blanking interval between each frequency hop
is then approximately 90 µs.
3) Run calibration on a single frequency at
startup. Next write 0 to FSCAL3[5:4] to
disable the charge pump calibration. After
writing to FSCAL3[5:4], strobe STX with
MCSM0.FS_AUTOCAL=1 for each new
frequency hop. That is, VCO current and VCO
capacitance calibration is done, but not charge
pump current calibration. When charge pump
current calibration is disabled the calibration
time is reduced from approximately 720 µs to
approximately 150 µs. The blanking interval
between each frequency hop is then
approximately 240 µs.
There is a trade off between blanking time and
memory space needed for storing calibration
data in non-volatile memory. Solution 2) above
gives the shortest blanking interval, but
requires more memory space to store
calibration values. This solution also requires
that the supply voltage and temperature do not
vary much in order to have a robust solution.
Solution 3) gives approximately 570 µs smaller
blanking interval than solution 1).
The recommended settings for
TEST0.VCO_SEL_CAL_EN change with
frequency. This means that one should always
use SmartRF Studio [11] to get the correct
settings for a specific frequency before doing a
calibration, regardless of which calibration
method is being used. It must be noted that
the content of the
CC1150
is not retained in
SLEEP state, and thus it is necessary to write
to the TEST0 register, along with other
registers, when returning from the SLEEP
state and initiating calibrations.
24.3 Wideband Modulation not using Spread Spectrum
Digital modulation systems under FFC part
15.247 include FSK and GFSK modulation. A
maximum peak output power of 1W (+30 dBm)
is allowed if the 6 dB bandwidth of the
modulated signal exceeds 500 kHz. In
addition, the peak power spectral density
conducted to the antenna shall not be greater
than +8 dBm in any 3 kHz band.
Operating at high data rates and frequency
deviation the
CC1150
is suited for systems
targeting compliance with digital modulation
system as defined by FFC part 15.247. An
external power amplifier is needed to increase
the output above +10 dBm. Please refer to
DN006 [5] for further details concerning
wideband modulation and
CC1150
.