CC1021-RTR1 datasheet(32/91 Pages) TI1

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Not Recommended for New Designs NRND

CC1021

SWRS045D – JANUARY 2006 – REVISED JANUARY 2015

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24. Write XG – DX to GAIN_COMP register.

25. Wait at least 3 ms. Measure signal strength Y1 as filtered average of 8 reads from RSSI register with

0.5 ms of delay between each RSSI read.

26. Write XG – 2 × DX to GAIN_COMP register.

27. Wait at least 3 ms. Measure signal strength Y0 as filtered average of 8 reads from RSSI register with

0.5 ms of delay between each RSSI read.

28. Set AG = 2 × (Y0 – Y2 + Y4) – (Y1 + Y3).

29.

If AG > 0 then

set DG = ROUND (7 × DX × (2 × (Y0 – Y4) + Y1 – Y3) / (10 × AG)

else

if Y0 + Y1 > Y3 + Y4 then

set DG = DX

else

set DG = –DX.

30.

If DG > DX then

set DG = DX

else

if DG < –DX then set DG = –DX

31. Set XG = XG + DG.

32. If DX > 1 then go to step 2.

33. Write XP to PHASE_COMP register and XG to GAIN_COMP register.

If repeated calibration gives varying results, try to change the input level or increase the number of RSSI

reads N. A good starting point is N=8. As accuracy is more important in the last fine-calibration steps, it

can be worthwhile to increase N for each loop iteration.

For high frequency deviation and high data rates (typically

≥ 76.8 kBaud) the analog filter succeeding the

mixer must be bypassed by setting FILTER_BYPASS = 1 in the FILTER register. In this case the image

rejection is degraded.

The image rejection is reduced for low supply voltages (typically < 2.5 V) when operating in the 402 to 470

MHz frequency range.

5.9.7

Blocking and Selectivity

Figure 5-13 shows the blocking/selectivity for 102.4 kHz channel filter bandwidth at 433 MHz and 19.2

kBaud data rate. Figure 5-14 shows the blocking/selectivity for 102.4 kHz channel filter bandwidth at 433

MHz and 38.4 kBaud data rate. Figure 5-15 shows the blocking/selectivity for 102.4 kHz channel filter

bandwidth at 868 MHz and 19.2 kBaud data rate. Figure 5-16 shows the blocking/selectivity for 102.4 kHz

channel filter bandwidth at 868 MHz and 38.4 kBaud data rate. The blocking rejection is the ratio between

a blocker (interferer) and a wanted signal 3 dB above the sensitivity limit.

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