CC2400 Datasheet, PDF (53/84 Pages) Texas Instruments – 2.4 GHz Low-Power RF Transceiver

CC2400
46 System Considerations and Guidelines
46.1 SRD regulations
International regulations and national laws
regulate the use of radio receivers and
transmitters. SRDs (Short Range Devices)
for license free operation are allowed to
operate in the 2.45 GHz bands worldwide.
The most important regulations are EN
300 440 and EN 300 328 (Europe), FCC
CFR47 part 15.247 and 15.249 (USA),
and ARIB STD-T66 (Japan).
The CC2400EM reference design
complies with EN 300 440. If frequency
hopping is to be used at 1 Mbps data rate,
GFSK should be selected to keep the
bandwidth below 1 MHz. The CC2400
complies with EN 300 440 class 2 if the
band spacing is 2 MHz or more. It
complies with EN 300 440 class 1 if the
channel and band spacing is 10 MHz or
more.
Please note that compliance with
regulations is dependent on complete
system performance. It is the customer’s
responsibility to ensure that the system
complies with regulations.
46.2 Frequency hopping and multi-
channel systems
The 2.400 – 2.4835 GHz band is shared
by many systems both in industrial, office
and home environment. 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.
CC2400 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.
Due to the low-IF I/Q receiver and the on-
chip complex filtering, the image channel
will be significantly rejected. This is
important for all 2.4GHz systems.
46.3 Data burst transmissions
The high maximum data rate of CC2400
opens up for burst transmissions. A low
average data rate link (say 10 kbps), can
be realized using a higher over-the-air
data rate. Buffering the data and
transmitting in bursts at high data rate (say
1 Mbps) will reduce the time in active
mode, and hence also reduce the average
current consumption significantly.
46.4 Continuous transmissions
In data streaming applications the CC2400
opens up for continuous transmissions at
1 Mbps effective data rate. A typical
application is digital audio systems. As the
modulation is done with an I/Q up-
converter with LO I/Q-signals coming from
a closed loop PLL, there is no limitation in
the length of a transmission. (Open loop
modulation used in some transceivers
often prevents this kind of continuous data
streaming and reduces the effective data
rate.)
46.5 Crystal drift compensation
A unique feature in CC2400 is the very fine
frequency resolution using the
MDMCTRL.MOD_OFFSET[5:0].
This
feature can be used to compensate for
frequency offset and drift. The
compensation affects both the receiver
and the transmitter of the device being
compensated. I.e. the received signal of
the device will match the receiver’s
channel filter better. In the same way the
center frequency of the transmitted signal
will match the ‘external’ transmitter’s
signal.
Initial adjustment can be done using this
frequency
programmability.
This
eliminates the need for an expensive
TCXO and trimming in some applications.
The frequency offset between an ‘external’
transmitter and the receiver is measured
in the CC2400 and can be read back from
an
internal
register
(FREQEST.RX_FREQ_OFFSET[7:0]).
SWRS042A
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