CC1020-RTR1 datasheet(42/95 Pages) TI1

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CC1021

RF_OUT

RF_IN

C60

R10

C71

C72

L70

L71

T/R

SWITCH

AVDD = 3 V

ANTENNA

CC1020

SWRS046H – NOVEMBER 2006 – REVISED MARCH 2015

www.ti.com

5.10.4 Reducing Spurious Emission and Modulation Bandwidth

Modulation bandwidth and spurious emission are normally measured with the PA continuously on and a

repeated test sequence.

In cases where the modulation bandwidth and spurious emission are measured with the CC1020

switching from power down mode to TX mode, a PA ramping sequence could be used to minimize

modulation bandwidth and spurious emission.

PA ramping should then be used both when switching the PA on and off. A linear PA ramping sequence

can be used where register PA_POWER is changed from 00h to 0Fh and then from 50h to the register

setting that gives the desired output power (for example, F0h for +10 dBm output power at 433 MHz

operation). The longer the time per PA ramping step the better, but setting the total PA ramping time equal

to 2 bit periods is a good compromise between performance and PA ramping time.

5.11 Input and Output Matching and Filtering

When designing the impedance matching network for the CC1020 the circuit must be matched correctly at

the harmonic frequencies as well as at the fundamental tone. A recommended matching network is shown

in Figure 5-22. Component values for various frequencies are given in Table 5-8. Component values for

other frequencies can be found using the SmartRF Studio software.

As can be seen from Figure 5-22 and Table 5-8, the 433 MHz network utilizes a T-type filter, while the

868/915 MHz network has a

π-type filter topology.

It is important to remember that the physical layout and the components used contribute significantly to

the reflection coefficient, especially at the higher harmonics. For this reason, the frequency response of

the matching network should be measured and compared to the response of the TI reference design.

Refer to Figure 5-24 and Table 5-9 as well as Figure 5-25 and Table 5-10.

The use of an external T/R switch reduces current consumption in TX for high output power levels and

improves the sensitivity in RX. A recommended application circuit is available from the TI web site

(CC1020EMX). The external T/R switch can be omitted in certain applications, but performance will then

be degraded.

The match can also be tuned by a shunt capacitor array at the PA output (RF_OUT). The capacitance can

be set in 0.4-pF steps and used either in RX mode or TX mode. The RX_MATCH[3:0] and

TX_MATCH[3:0] bits in the MATCH register control the capacitor array.

Figure 5-22. Input and Output Matching Network

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CC1020-RTR1 Datenblatt(PDF) 42 Page - Texas Instruments

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