CC1021-RTR1 datasheet(57/91 Pages) TI1

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Not Recommended for New Designs NRND

CC1021

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SWRS045D – JANUARY 2006 – REVISED JANUARY 2015

5.20.2 Narrowband Systems

CC1021 is recommended for narrowband applications with channel spacing of 50 kHz and higher

complying with FCC CFR47 part 15 and EN 300 220.

CC1020 is recommended in narrowband applications with channel spacing of 12.5 or 25 kHz complying

with ARIB STD T-67 and EN 300 220.

CC1020 and CC1021 are fully compatible for channel spacings of 50 kHz and higher (receiver channel

filter bandwidths of 38.4 kHz and higher).

Due to on-chip complex filtering, the image frequency is removed. An on-chip calibration circuit is used to

get the best possible image rejection. A narrowband preselector filter is not necessary to achieve image

rejection.

A unique feature in CC1021 is the very fine frequency resolution. This can be used for temperature

compensation of the crystal if the temperature drift curve is known and a temperature sensor is included in

the system. Even initial adjustment can be performed using the frequency programmability. This

eliminates the need for an expensive TCXO and trimming in some applications. For more details refer to

Application Note AN027 Temperature Compensation by Indirect Method (SWRA065).

In less demanding applications, a crystal with low temperature drift and low aging could be used without

further compensation. A trimmer capacitor in the crystal oscillator circuit (in parallel with C5) could be used

to set the initial frequency accurately.

The frequency offset between a transmitter and receiver is measured in the CC1021 and can be read

back from the AFC register. The measured frequency offset can be used to calibrate the receiver

frequency using the transmitter as the reference. For more details refer to Application Note AN029

CC1020/1021 Automatic Frequency Control (AFC) (SWRA063).

CC1021 also has the possibility to use Gaussian shaped FSK (GFSK). This spectrum-shaping feature

improves adjacent channel power (ACP) and occupied bandwidth. In ‘true’ 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.

5.20.3 Low Cost Systems

As the CC1021 provide true narrowband multi-channel performance without any external filters, a very low

cost high performance system can be achieved. The oscillator crystal can then be a low cost crystal with

50 ppm frequency tolerance using the on-chip frequency tuning possibilities.

5.20.4 Battery Operated Systems

In low power applications, the power down mode should be used when CC1021 is not being active.

Depending on the start-up time requirement, the oscillator core can be powered during power down. See

Section 5.14 for information on how effective power management can be implemented.

5.20.5 High Reliability Systems

Using a SAW filter as a preselector will improve the communication reliability in harsh environments by

reducing the probability of blocking. The receiver sensitivity and the output power will be reduced due to

the filter insertion loss. By inserting the filter in the RX path only, together with an external RX/TX switch,

only the receiver sensitivity is reduced and output power is remained. The PA_EN and LNA_EN pin can

be configured to control an external LNA, RX/TX switch or power amplifier. This is controlled by the

INTERFACE register.

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CC1021-RTR1 Datasheet(PDF) 57 Page - Texas Instruments

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