CC1110Fx / CC1111Fx
transmissions. A low average data rate link
(e.g. 10 kBaud), can be realized using a higher
over-the-air data rate. Buffering the data and
transmitting in bursts at high data rate (e.g.
500 kBaud) will reduce the time in active
mode, and hence also reduce the average
current consumption significantly. Reducing
the time in active mode will reduce the
likelihood of collisions with other systems in
the same frequency range. Note that sensitivity
and thus transmission range is reduced in high
data rate bursts compared to lower data rates.
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.
14.18.7 Low Cost Systems
A HC-49 type SMD crystal is used in the
CC1110EM reference design [1]. Note that the
crystal package strongly influences the price.
In a size constrained PCB design a smaller,
but more expensive, crystal may be used.
14.18.5 Crystal Drift Compensation
The CC1110Fx/CC1111Fx has a very fine frequency
resolution (see Table 16).This feature can be
used to compensate for frequency offset and
drift.
14.18.8 Battery Operated Systems
In low power applications, PM2 or PM3 should
be used when the CC1110Fx/CC1111Fx is not
active. The Sleep Timer can be used in PM2.
The frequency offset between an ‘external’
transmitter and the receiver is measured in the
CC1110Fx/CC1111Fx and can be read back from
the FREQEST status register as described in
Section 14.7.1. The measured frequency offset
can be used to calibrate the frequency using
the ‘external’ transmitter as the reference. That
is, the received signal of the device will match
the receiver’s channel filter better. In the same
way the centre frequency of the transmitted
signal will match the ‘external’ transmitter’s
signal.
14.18.9 Increasing Output Power
In some applications it may be necessary to
extend the link range. Adding an external
power amplifier is the most effective way of
doing this.
The power amplifier should be inserted
between the antenna and the balun, and two
T/R switches are needed to disconnect the PA
in RX mode. See Figure 60.
14.18.6 Spectrum Efficient Modulation
CC1110Fx/CC1111Fx also has the possibility to use
Gaussian shaped 2-FSK (GFSK). This
Antenna
Filter
P
A
CC1110Fx /
Balun
CC1111Fx
T/R
switch
T/R
switch
Figure 60: Block Diagram of CC1110Fx/CC1111Fx Usage with External Power Amplifier
SWRS033E
Page 208 of 239
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