CC1100-RTR1 datasheet(59/100 Pages) TI1

59 / 100 page

CC1100

SWRS038D

Page 59 of 92

32.5 Continuous Transmissions

In data streaming applications the

CC1100

opens up for continuous transmissions at 500

kBaud effective data rate. As the modulation is

done with 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).

32.6 Crystal Drift Compensation

The

CC1100 has a very fine frequency

resolution (see Table 9). This feature can be

used to compensate for frequency offset and

drift.

The frequency offset between an ‘external’

transmitter and the receiver is measured in the

CC1100 and can be read back from the

FREQEST

status register as described in

Section 14.1. 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.

32.7 Spectrum Efficient Modulation

CC1100 also has the possibility to use Gaussian

shaped 2-FSK (GFSK). 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.

32.8 Low Cost Systems

As the

CC1100 provides 500 kBaud multi-

channel performance without any external

filters, a very low cost system can be made.

A differential antenna will eliminate the need

for a balun, and the DC biasing can be

achieved in the antenna topology, see Figure 3

and Figure 4.

A HC-49 type SMD crystal is used in the

CC1100EM reference designs ([5] and [6]).

Note that the crystal package strongly

influences the price. In a size constrained PCB

design a smaller, but more expensive, crystal

may be used.

32.9 Battery Operated Systems

In low power applications, the SLEEP state

with the crystal oscillator core switched off

should be used when the

CC1100 is not active.

It is possible to leave the crystal oscillator core

running in the SLEEP state if start-up time is

critical.

The WOR functionality should be used in low

power applications.

32.10 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 30.

Figure 30: Block Diagram of

CC1100 Usage with External Power Amplifier

CC1100

Balun

Filter

Antenna

T/R

switch

T/R

switch

CC1100-RTR1 Datasheet(PDF) 59 Page - Texas Instruments

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