CC1021-RTR1 datasheet(62/92 Pages) TI

62 / 92 page

CC1021

SWRS045

Page 62 of 91

Narrowband systems

CC1021 is recommended for narrowband

applications with channel spacings of 50

kHz and higher complying with FCC

CFR47 part 15 and EN 300 220.

CC1020 is recommended in narrowband

applications with channel spacings 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

removed.

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 available from the Chipcon

web site.

In less demanding applications, a crystal

with low temperature drift and low aging

could

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

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

AFC available from the Chipcon web site.

CC1021 also has the possibility to use

Gaussian shaped FSK (GFSK). This

spectrum-shaping

feature

improves

adjacent channel power (ACP) and

occupied bandwidth. In ëtrueí FSK systems

with

abrupt

frequency

shifting,

the

spectrum is inherently broad. By making

the frequency shift ësofterí, the spectrum

can be made significantly narrower. Thus,

higher data rates can be transmitted in the

same bandwidth using GFSK.

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.

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 17 page 54 for information on how

effective power management can be

implemented.

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.

Frequency hopping spread spectrum

systems (FHSS)

Due to the very fast locking properties of

the PLL, the CC1021 is also very suitable for

frequency hopping systems. Hop rates of

1-100

hops/s

are

commonly

used

depending on the bit rate and the amount

data

sent

during

each

transmission. The two frequency registers

(FREQ_A and FREQ_B) are designed

such that the ënextí frequency can be

programmed while the ëpresentí frequency

CC1021-RTR1 Datasheet(PDF) 62 Page - Texas Instruments

CC1021-RTR1 Datasheet(HTML) 62 Page - Texas Instruments

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