CC1021-RTR1 datasheet(29/91 Pages) TI1

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filter _ clock

RSSI

AGC _ AVG[1:0] 1

Not Recommended for New Designs NRND

CC1021

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SWRS045D – JANUARY 2006 – REVISED JANUARY 2015

Table 5-6. Typical Receiver Sensitivity as a Function of Data Rate at 433 MHz, FSK Modulation,

BER = 10−3, Pseudo-Random Data (PN9 Sequence)

SENSITIVITY [dBm]

DATA RATE

DEVIATION

FILTER BW

MANCHESTER

[kBaud]

[kHz]

NRZ MODE

UART MODE

MODE

4.8

±4.95

38.4

–109

–112

–109

19.2

±9.9

51.2

–107

–108

–107

19.2

±19.8

102.4

–104

–106

–104

38.4

±19.8

102.4

–104

76.8

±36.0

153.6

–101

153.6

±72.0

307.2

–96

–97

–96

Table 5-7. Typical Receiver Sensitivity as a Function of Data Rate at 868 MHz, FSK Modulation,

BER = 10−3, Pseudo-Random Data (PN9 Sequence)

SENSITIVITY [dBm]

DATA RATE

DEVIATION

FILTER BW

MANCHESTER

[kBaud]

[kHz]

NRZ MODE

UART MODE

MODE

4.8

±4.95

38.4

–108

–111

–108

19.2

±9.9

51.2

–107

19.2

±19.8

102.4

–103

–106

–103

38.4

±19.8

102.4

–103

76.8

±36.0

153.6

–99

–100

–99

153.6

±72.0

307.2

–94

5.9.5

RSSI

CC1021 has a built-in RSSI (Received Signal Strength Indicator) giving a digital value that can be read

form the RSSI register. The RSSI reading must be offset and adjusted for VGA gain setting

(VGA_SETTING[4:0] in the VGA3 register).

The digital RSSI value is ranging from 0 to 106 (7 bits).

The RSSI reading is a logarithmic measure of the average voltage amplitude after the digital filter in the

digital part of the IF chain as shown in Equation 18.

RSSI = 4 log2 (signal amplitude)

(18)

The relative power is then given by RSSI × 1.5 dB in a logarithmic scale.

The number of samples used to calculate the average signal amplitude is controlled by AGC_AVG[1:0] in

the VGA2 register. The RSSI update rate is given by Equation 19.

(19)

Where:

AGC_AVG[1:0] is set in the VGA2 register.

ffilter_clock = 2 × ChBW.

Maximum VGA gain is programmed by the VGA_SETTING[4:0] bits. The VGA gain is programmed in

approximately 3 dB/LSB. The RSSI measurement can be referred to the power (absolute value) at the

RF_IN pin by using Equation 20.

P = 1.5 × RSSI – 3 × VGA_SETTING – RSSI_Offset [dBm]

(20)

The RSSI_Offset depends on the channel filter bandwidth used due to different VGA settings. Figure 5-11

and Figure 5-12 show typical plots of RSSI reading as a function of input power for different channel filter

bandwidths. Refer to Application Note AN030 CC1020/1021 Received Signal Strength Indicator

(SWRA062) for further details.

Detailed Description

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