Application Note AN030
CC1020/1021 Received Signal Strength Indicator
By S. Hellan, O. Stengel
Keywords
• RSSI
• Received Signal Strength Indicator
• RSSI attach time
• AGC settling time
Introduction
The CC1020 and CC1021 transceivers have
a built-in feature called Received Signal
Strength Indicator (RSSI) [1], [2]. The
RSSI, which is a measure of the actual RF
power input to the transceiver, is
presented digitally, and can be read from
one of the internal registers.
RSSI may be used to determine RF link
quality and is very useful in dense traffic
scenarios where interference is of major
concern. RSSI is typically employed in
channelized systems utilizing co-existence
schemes such as adaptive frequency
hopping and listen-before-talk (LBT). A
carrier sense multiple access (CSMA)
device implements one type of LBT. If a
channel is sensed busy, transmission is
postponed. If several channels are
available the transmitter can first check if
SWRA062
the channel is idle. If not, the transmitter
will try a different channel.
This application note provides RSSI
readings for different receiver channel
filter bandwidths. It will be shown how to
convert the RSSI reading to the actual RF
power at the RF input. The equation used
to convert from a digital readout to power
at the RF input requires an offset value.
This offset value varies for different
receiver channel filter bandwidths.
Plots showing RSSI attach time and RSSI
accuracy are included in this application
note. The Automatic Gain Control (AGC)
settling time will be equal to the RSSI
attach time.
Page 1 of 23
Application Note AN030
Table of Contents
1.
RSSI ................................................................................................................................... 3
2.
MEASUREMENT SETUP .................................................................................................. 3
3.
RSSI VERSUS INPUT POWER LEVEL ............................................................................ 4
4.
RSSI ACCURACY AND RSSI ATTACH TIME ................................................................ 11
5.
CONCLUSION ................................................................................................................. 20
6.
APPENDIX – THEORETICAL RSSI ATTACH TIME....................................................... 21
7.
REFERENCES................................................................................................................. 22
8.
GENERAL INFORMATION ............................................................................................. 22
9.
ADDRESS INFORMATION ............................................................................................. 23
SWRA062
Page 2 of 23
Application Note AN030
1.
RSSI
CC1020 and CC1021 have a built-in RSSI (Received Signal Strength Indicator) providing a
digital value that can be read from the RSSI register. The digital RSSI value ranges from 0 to
106 (7 bits).
The number of samples used to calculate the average signal amplitude is controlled by
VGA2.AGC_AVG[1:0]. The RSSI update rate is given by:
f RSSI =
(1)
FILTER _ CLK
2 AGC _ AVG [1:0 ]+1
where
AGC_AVG[1:0] is set in the VGA2 register
FILTER_CLK is 2 times the receiver channel filter bandwidth
The RSSI measurement can be referred to the power at the RF input pin by using the
following equation:
P = 1.5 · RSSI - 3 · VGA_SETTING - RSSI_Offset [dBm]
(2)
where
RSSI is the digital value read from the RSSI register converted to decimal.
VGA_SETTING is the maximum VGA gain and is set by VGA3.VGA_SETTING [4:0].
The VGA gain is programmable in steps of approximately 3 dB.
RSSI_Offset depends on the channel filter bandwidth used due to different VGA
settings.
2.
Measurement Setup
Figure 1 shows the measurement setup.
RF generator
RF signal
CC1020 transceiver
Microcontroller
Crystal
Figure 1. Measurement setup
SWRA062
Page 3 of 23
Application Note AN030
3.
RSSI versus Input Power Level
•
The RSSI register readings were recorded for different RF input power levels at
different receiver channel filter bandwidths.
•
The RSSI register readings
VGA2.AGC_AVG[1:0].
•
RSSI_Offset values were calculated using Equation 2 for the different receiver
channel filter bandwidths.
•
For receiver channel filter bandwidths below 153.6 kHz the RSSI_Offset is calculated
as the average RSSI_Offset with an RF input power level ranging from –105 to –70
dBm.
•
For receiver channel filter bandwidths at 153.6 kHz and above the RSSI_Offset is
calculated as the average RSSI_Offset with an RF input power level ranging from
–100 to –60 dBm.
•
Figure 2 to Figure 17 present the RSSI readings in dBm for the different receiver
channel filter bandwidths.
•
All measurements were performed at 3.0 V, 27oC.
were
performed
for
all
four
settings
of
Table 1 states the typical RSSI_Offset values.
Carrier
frequency [MHz]
433
868
Receiver channel
filter bandwidth [kHz]
12.288
19.2
25.6
38.4
51.2
102.4
153.6
307.2
12.288
19.2
25.6
38.4
51.2
102.4
153.6
307.2
RSSI_Offset
98
100
94
96
95
95
97
99
91
96
92
93
91
92
95
95
VGA_SETTING
[decimal]
11
15
14
13
13
15
18
19
15
14
13
13
13
14
16
20
Figure
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
Figure 14
Figure 15
Figure 16
Figure 17
Table 1. Typical RSSI_Offset values for different receiver channel filter bandwidths
SWRA062
Page 4 of 23
Application Note AN030
RSSI versus input power level
Carrier frequency 433 MHz, filter bandwidth 12.288 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
-80
AGC_AVG = 2
AGC_AVG = 1
-90
AGC_AVG = 0
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
Input power level [dBm]
Figure 2
RSSI versus input power level
Carrier frequency 433 MHz, filter bandwidth 19.2 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
-80
AGC_AVG = 2
AGC_AVG = 1
-90
AGC_AVG = 0
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
Input power level [dBm]
Figure 3
RSSI versus input power level
Carrier frequency 433 MHz , filter bandwidth 25.6 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
-80
AGC_AVG = 2
AGC_AVG = 1
-90
AGC_AVG = 0
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
Input power level [dBm]
Figure 4
SWRA062
Page 5 of 23
Application Note AN030
RSSI versus input power level
Carrier frequency 433 MHz, filter bandwidth 38.4 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
AGC_AVG = 2
AGC_AVG = 1
AGC_AVG = 0
-80
-90
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
Input power level [dBm]
Figure 5
RSSI versus input power level
Carrier frequency 433 MHz , filter bandwidth 51.2 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
-80
AGC_AVG = 2
AGC_AVG = 1
AGC_AVG = 0
-90
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
Input power level [dBm]
Figure 6
RSSI versus input power level
Carrier frequency 433 MHz, filter bandwidth 102.4 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
-80
AGC_AVG = 3
AGC_AVG = 2
-90
AGC_AVG = 1
AGC_AVG = 0
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
Input power level [dBm]
Figure 7
SWRA062
Page 6 of 23
Application Note AN030
RSSI versus input power level
Carrier frequency 433 MHz, filter bandwidth 153.6 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
-80
AGC_AVG = 2
AGC_AVG = 1
-90
AGC_AVG = 0
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
Input power level [dBm]
Figure 8
RSSI versus input power level
Carrier frequency 433 MHz, filter bandwidth 307.2 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
-80
AGC_AVG = 2
AGC_AVG = 1
-90
AGC_AVG = 0
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
Input power level [dBm]
Figure 9
RSSI versus input power level
Carrier frequency 868 MHz, filter bandwidth 12.288 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
-80
AGC_AVG = 2
AGC_AVG = 1
-90
AGC_AVG = 0
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
Input power level [dBm]
Figure 10
SWRA062
Page 7 of 23
Application Note AN030
RSSI versus input power level
Carrier frequency 868 MHz, filter bandwidth 19.2 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
-80
AGC_AVG = 2
AGC_AVG = 1
-90
AGC_AVG = 0
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
Input power level [dBm]
Figure 11
RSSI versus input power level
Carrier frequency 868 MHz, filter bandwidth 25.6 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
-80
AGC_AVG = 3
-90
AGC_AVG = 2
AGC_AVG = 1
-100
AGC_AVG = 0
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
Input power level [dBm]
Figure 12
RSSI versus input power level
Carrier frequency 868 MHz , filter bandwidth 38.4 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
-80
AGC_AVG = 2
AGC_AVG = 1
-90
AGC_AVG = 0
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
Input power level [dBm]
Figure 13
SWRA062
Page 8 of 23
Application Note AN030
RSSI versus input power level
Carrier frequency 868 MHz, filter bandwidth 51.2 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
-80
AGC_AVG = 2
AGC_AVG = 1
-90
AGC_AVG = 0
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
Input power level [dBm]
Figure 14
RSSI versus input power level
Carrier frequency 868 MHz, filter bandwidth 102.4 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
-80
AGC_AVG = 2
AGC_AVG = 1
-90
AGC_AVG = 0
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
Input power level [dBm]
Figure 15
RSSI versus input power level
Carrier frequency 868 MHz, filter bandwidth 153.6 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
-80
AGC_AVG = 2
AGC_AVG = 1
-90
AGC_AVG = 0
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
Input power level [dBm]
Figure 16
SWRA062
Page 9 of 23
Application Note AN030
RSSI versus input power level
Carrier frequency 868 MHz, filter bandwidth 307.2 kHz
-30
-40
RSSI reading [dBm]
-50
-60
-70
AGC_AVG = 3
AGC_AVG = 2
AGC_AVG = 1
AGC_AVG = 0
-80
-90
-100
-110
-120
-130
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
Input power level [dBm]
Figure 17
SWRA062
Page 10 of 23
Application Note AN030
4.
RSSI Accuracy and RSSI Attach Time
•
The RSSI register readings were recorded for different RF input power levels at
different receiver channel filter bandwidths.
•
The RSSI register readings were performed for two settings of VGA2.AGC_AVG[1:0].
•
Figure 19 to Figure 26 present the RSSI readings in decimal value for the different
receiver channel filter bandwidths.
•
The receive chain is switched on by changing register MAIN from 11h to 01h at time
t=0 in Figure 19 to Figure 26.
•
Figure 18 shows RSSI and STATUS7.VGA_GAIN_OFFSET[4:0] readings. The latter
is a readout of the offset between VGA3.VGA_SETTING[3:0] and the actual VGA
gain set by the AGC.
•
The RSSI attach time is defined as the time required for the RSSI reading to
“stabilize”. See Figure 18.
•
When the receive chain is switched on the AGC needs a finite time to stabilize. The
RSSI reading is “stable” when the AGC has settled. Thus, Figure 19 to Figure 26 also
show the AGC settling time (see also Figure 18).
•
There will be some inaccuracies in the RSSI reading due to rounding errors in the onchip RSSI calculation and noise. The inaccuracy can be observed as “ripple” in
Figure 18 to Figure 26.
•
The RSSI accuracy can be read from Figure 19 to Figure 26.
•
All measurements were performed at 3.0 V, 27oC
30
25
ripple
RSSI attach time
20
15
10
AGC settling time
5
4908
4650
4392
4134
3876
3618
3360
3102
2844
2586
2328
2070
1812
1554
1296
1038
780
522
264
0
6
RSSI / STATUS7 register
-90 dBm, AGC_AVG=01b
time [us]
RSSI_1
RSSI_2
VGA_GAIN_OFFSET
Figure 18. Definition of RSSI attach time, AGC settling time and “ripple” in RSSI reading.
SWRA062
Page 11 of 23
Application Note AN030
-110 dBm, AGC_AVG=01b
25
RSSI register
20
15
10
5
4038
4326
4614
4902
4038
4326
4614
4902
3750
3462
3174
2886
2598
2310
2022
1734
1446
1158
870
582
294
6
0
time [us]
1
2
3
4
5
3750
3462
3174
2886
2598
2310
2022
1734
1446
1158
870
582
294
20
18
16
14
12
10
8
6
4
2
0
6
RSSI register
-110 dBm, AGC_AVG=11b
time [us]
1
2
3
4
5
Figure 19. 2.4 kBaud, 12.288 kHz receiver filter bandwidth, 433 MHz, -110 dBm input power
level.
SWRA062
Page 12 of 23
Application Note AN030
-100 dBm, AGC_AVG=01b
30
RSSI register
25
20
15
10
5
4392
4902
4908
4134
4614
4650
3876
4326
3618
3360
3102
2844
2586
2328
2070
1812
1554
1296
1038
780
522
264
6
0
time [us]
1
2
3
4
5
-100 dBm, AGC_AVG=11b
30
RSSI register
25
20
15
10
5
4038
3750
3462
3174
2886
2598
2310
2022
1734
1446
1158
870
582
294
6
0
time [us]
1
2
3
4
5
Figure 20. 2.4 kBaud, 12.288 kHz receiver filter bandwidth, 433 MHz, -100 dBm input power
level.
SWRA062
Page 13 of 23
Application Note AN030
-110 dBm, AGC_AVG=01b
30
RSSI register
25
20
15
10
5
4038
4326
4614
4902
4038
4326
4614
4902
3750
3462
3174
2886
2598
2310
2022
1734
1446
1158
870
582
294
6
0
time [us]
1
2
3
4
5
-110 dBm, AGC_AVG=11b
25
RSSI register
20
15
10
5
3750
3462
3174
2886
2598
2310
2022
1734
1446
1158
870
582
294
6
0
time [us]
1
2
3
4
5
Figure 21. 4.8 kBaud, 19.2 kHz receiver filter bandwidth, 868 MHz, -110 dBm input power
level.
SWRA062
Page 14 of 23
Application Note AN030
-100 dBm, AGC_AVG=01b
30
RSSI register
25
20
15
10
5
4392
4902
4908
4134
4614
4650
3876
4326
3618
3360
3102
2844
2586
2328
2070
1812
1554
1296
1038
780
522
264
6
0
time [us]
1
2
3
4
5
-100 dBm, AGC_AVG=11b
30
RSSI register
25
20
15
10
5
4038
3750
3462
3174
2886
2598
2310
2022
1734
1446
1158
870
582
294
6
0
time [us]
1
2
3
4
5
Figure 22. 4.8 kBaud, 19.2 kHz receiver filter bandwidth, 868 MHz, -100 dBm input power
level.
SWRA062
Page 15 of 23
Application Note AN030
-110 dBm, AGC_AVG = 01b
30
RSSI register
25
20
15
10
5
4038
4326
4614
4902
4038
4326
4614
4902
3750
3462
3174
2886
2598
2310
2022
1734
1446
1158
870
582
294
6
0
time [us]
1
2
3
4
5
3750
3462
3174
2886
2598
2310
2022
1734
1446
1158
870
582
294
20
18
16
14
12
10
8
6
4
2
0
6
RSSI register
-110 dBm, AGC_AVG=11b
time [us]
1
2
3
4
5
Figure 23. 9.6 kBaud, 25.6 kHz receiver filter bandwidth, 433 MHz, -110 dBm input power
level.
SWRA062
Page 16 of 23
Application Note AN030
-90 dBm, AGC_AVG=01b
35
RSSI register
30
25
20
15
10
5
4392
4902
4908
4134
4614
4650
3876
4326
3618
3360
3102
2844
2586
2328
2070
1812
1554
1296
1038
780
522
264
6
0
time [us]
1
2
3
4
5
-90 dBm, AGC_AVG = 11b
35
RSSI register
30
25
20
15
10
5
4038
3750
3462
3174
2886
2598
2310
2022
1734
1446
1158
870
582
294
6
0
time [us]
1
2
3
4
5
Figure 24. 9.6 kBaud, 25.6 kHz receiver filter bandwidth, 433 MHz, -90 dBm input power
level.
SWRA062
Page 17 of 23
Application Note AN030
-105 dBm, AGC_AVG=01b
25
RSSI register
20
15
10
5
4038
4326
4614
4902
4038
4326
4614
4902
3750
3462
3174
2886
2598
2310
2022
1734
1446
1158
870
582
294
6
0
time [us]
1
2
3
4
5
-105 dBm, AGC_AVG=11b
25
RSSI register
20
15
10
5
3750
3462
3174
2886
2598
2310
2022
1734
1446
1158
870
582
294
6
0
time [us]
1
2
3
4
5
Figure 25. 19.2 kBaud, 51.2 kHz receiver filter bandwidth, 868 MHz, -105 dBm input power
level.
SWRA062
Page 18 of 23
Application Note AN030
4392
4902
4908
4134
4614
4650
3876
4326
3618
3360
3102
2844
2586
2328
2070
1812
1554
1296
1038
780
522
264
50
45
40
35
30
25
20
15
10
5
0
6
RSSI register
-70 dBm, AGC_AVG=01b
time [us]
1
2
3
4
5
4038
3750
3462
3174
2886
2598
2310
2022
1734
1446
1158
870
582
294
45
40
35
30
25
20
15
10
5
0
6
RSSI register
-70 dBm, AGC_AVG=11b
time [us]
1
2
3
4
5
Figure 26. 19.2 kBaud, 51.2 kHz receiver filter bandwidth, 868 MHz, -70 dBm input power
level.
SWRA062
Page 19 of 23
Application Note AN030
5.
Conclusion
The analog filter succeeding the mixer in CC1020 and CC1021 has a finite dynamic range and is
the reason why the RSSI reading is saturated for lower receiver channel filter bandwidths.
Higher receiver channel filter bandwidths are typically used for high frequency deviation and
data rates. The analog filter bandwidth is about 160 kHz and is bypassed for high frequency
deviation and data rates and is the reason why the RSSI reading is not saturated for 153.6
kHz and 307.2 kHz receiver channel filter bandwidths in Figure 8, Figure 9, Figure 16 and
Figure 17.
The RSSI attach time is the time required for the RSSI reading to stabilize. In Figure 19 to
Figure 26 there are first one or two large steps in the RSSI reading followed by ripple in the
RSSI reading. The large step is due to gain changes in the AGC. The ripple is due to
rounding errors in the digital part and noise (especially at low input power levels) and there
will be inaccuracies in the RSSI reading even after the AGC has settled. The number of
samples used to calculate the average signal amplitude is controlled by AGC_AVG[1:0] in the
VGA2 register. The RSSI reading (and hence the ripple) update rate is
f RSSI =
FILTER _ CLK
2 AGC _ AVG [1:0 ]+1
We see from Figure 19 to Figure 26 that setting VGA2.AGC_AVG[1:0] = 3 gives the most
accurate RSSI reading.
Increasing AGC_AVG increases the RSSI attach time and AGC settling time. Thus, there is a
trade-off between RSSI attach time and RSSI accuracy and also between AGC settling time
and RSSI accuracy.
A change of 1 in the decimal RSSI reading corresponds to a 1.5 dB change in the calculated
input power level. Thus, from Figure 19 to Figure 26 we see that the RSSI accuracy is better
than ±3 dB with VGA2.AGC_AVG[1:0] = 3.
Appendix A provides the theoretical RSSI attach time (and AGC settling time) for
VGA2.AGC_AVG[1:0] = 1 and VGA2.AGC_AVG[1:0] = 3 for different receiver channel filter
bandwidths. The theoretical values are in accordance with the measured values.
SWRA062
Page 20 of 23
Application Note AN030
6.
Appendix – Theoretical RSSI Attach Time
RSSI calculation VGA1 61h, VGA2 55h
Data rate
Channel filter BW
The raw AGC sample rate is the
FILTER_CLK frequency, which is twice the
channel filter bandwidth.
FILTER_CLK
2.4
1.229E+04
4.8
1.920E+04
9.6
2.560E+04
19.2
5.120E+04
38.4
1.024E+05
76.8
1.536E+05
153.6
kbps
3.072E+05 Hz
2.4576E+04
3.8400E+04
5.1200E+04
1.0240E+05
2.0480E+05
3.0720E+05
6.1440E+05 Hz
1.30208E-05
1.30208E-05
1.30208E-05
1.30208E-05
1.30208E-05
1.30208E-05
1.30208E-05 sec
After turning on Rx:
Step
A
AGC waits 16-128 ADC_CLK (1.2288
MHz) periods. Depends on
VGA_FREEZE. 16 periods.
B
AGC waits 16-48 FILTER_CLK periods.
Depends on VGA_WAIT. 16 periods.
6.5104E-04
4.1667E-04
3.1250E-04
1.5625E-04
7.8125E-05
5.2083E-05
2.6042E-05 sec
C
AGC calculates the RSSI value as the
average value over the next 2-16
FILTER_CLOCK periods. Depends on
AGC_AVG. 4 samples.
1.6276E-04
1.0417E-04
7.8125E-05
3.9063E-05
1.9531E-05
1.3021E-05
6.5104E-06 sec
D
If the RSSI value is higher than CS_LEVEL+8, then the carrier sense indicator is set (if CS_SET=0). If the RSSI value is too high according to the
CS_LEVEL, VGA_UP and VGA_DOWN settings, and the VGA gain is not already at minimum, then the VGA gain is reduced and the AGC continues from
B).
E
If the RSSI value was too low according to the CS_LEVEL and VGA_UP settings, and the VGA gain is not already at maximum (given by the
VGA_SETTING), then the VGA gain is increased and the AGC continues from B).
F
F
F
1 VGA gain change
2 VGA gain changes
3 VGA gain changes
RSSI update rate
8.2682E-04
1.6406E-03
2.4544E-03
163
5.3385E-04
1.0547E-03
1.5755E-03
104
4.0365E-04
7.9427E-04
1.1849E-03
78
2.0833E-04
4.0365E-04
5.9896E-04
39
1.1068E-04
2.0833E-04
3.0599E-04
20
7.8125E-05
1.4323E-04
2.0833E-04
4.5573E-05 sec
7.8125E-05 sec
1.1068E-04 sec
13
7
us
RSSI calculation VGA1 61h, VGA2 57h
Data rate
Channel filter BW
The raw AGC sample rate is the
FILTER_CLK frequency, which is twice
the channel filter bandwidth.
FILTER_CLK
2.4
1.229E+04
4.8
1.920E+04
9.6
2.560E+04
19.2
5.120E+04
38.4
1.024E+05
76.8
1.536E+05
153.6
kbps
3.072E+05 Hz
2.4576E+04
3.8400E+04
5.1200E+04
1.0240E+05
2.0480E+05
3.0720E+05
6.1440E+05 Hz
1.30208E-05
1.30208E-05
1.30208E-05
1.30208E-05
1.30208E-05
1.30208E-05
1.30208E-05 sec
After turning on Rx:
Step
A
AGC waits 16-128 ADC_CLK (1.2288
MHz) periods. Depends on
VGA_FREEZE. 16 periods.
B
AGC waits 16-48 FILTER_CLK periods.
Depends on VGA_WAIT. 16 periods.
6.5104E-04
4.1667E-04
3.1250E-04
1.5625E-04
7.8125E-05
5.2083E-05
2.6042E-05 sec
C
AGC calculates the RSSI value as the
average value over the next 2-16
FILTER_CLOCK periods. Depends on
AGC_AVG. 16 samples.
6.5104E-04
4.1667E-04
3.1250E-04
1.5625E-04
7.8125E-05
5.2083E-05
2.6042E-05 sec
D
If the RSSI value is higher than CS_LEVEL+8, then the carrier sense indicator is set (if CS_SET=0). If the RSSI value is too high according to the
CS_LEVEL, VGA_UP and VGA_DOWN settings, and the VGA gain is not already at minimum, then the VGA gain is red
E
If the RSSI value was too low according to the CS_LEVEL and VGA_UP settings, and the VGA gain is not already at maximum (given by the
VGA_SETTING), then the VGA gain is increased and the AGC continues from B).
F
F
F
1 VGA gain change
2 VGA gain changes
3 VGA gain changes
RSSI update rate
1.3151E-03
2.6172E-03
3.9193E-03
651
8.4635E-04
1.6797E-03
2.5130E-03
417
SWRA062
6.3802E-04
1.2630E-03
1.8880E-03
313
3.2552E-04
6.3802E-04
9.5052E-04
156
1.6927E-04
3.2552E-04
4.8177E-04
78
1.1719E-04
2.2135E-04
3.2552E-04
52
6.5104E-05 sec
1.1719E-04 sec
1.6927E-04 sec
26
Page 21 of 23
us
Application Note AN030
7.
References
[1]
[2]
Chipcon, CC1020 data sheet. Downloadable from http://www.chipcon.com
Chipcon, CC1021 data sheet. Downloadable from http://www.chipcon.com
8.
General Information
Document History
Revision
1.0
1.1
Date
August 2004
January 2005
Description/Changes
Initial release.
Added information about RSSI attach time.
Added information about RSSI accuracy.
Disclaimer
Chipcon AS believes the information contained herein is correct and accurate at the time of this printing. However,
Chipcon AS reserves the right to make changes to this product without notice. Chipcon AS does not assume any
responsibility for the use of the described product; neither does it convey any license under its patent rights, or the
rights of others. The latest updates are available at the Chipcon website or by contacting Chipcon directly.
To the extent possible, major changes of product specifications and functionality will be stated in product specific
Errata Notes published at the Chipcon website. Customers are encouraged to sign up for the Developer’s Newsletter
for the most recent updates on products and support tools.
When a product is discontinued this will be done according to Chipcon’s procedure for obsolete products as
described in Chipcon’s Quality Manual. This includes informing about last-time-buy options. The Quality Manual can
be downloaded from Chipcon’s website.
Compliance with regulations is dependent on complete system performance. It is the customer’s responsibility to
ensure that the system complies with regulations.
Trademarks
SmartRF® is a registered trademark of Chipcon AS. SmartRF® is Chipcon's RF technology platform with RF library
cells, modules and design expertise. Based on SmartRF® technology Chipcon develops standard component RF
circuits as well as full custom ASICs based on customer requirements and this technology.
All other trademarks, registered trademarks and product names are the sole property of their respective owners.
Life Support Policy
Chipcon’s products are not designed for use in life support appliances, devices, or other systems where malfunction
can reasonably be expected to result in significant personal injury to the user, or as a critical component in any life
support device or system whose failure to perform can be reasonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness. Chipcon AS customers using or selling these products for
use in such applications do so at their own risk and agree to fully indemnify Chipcon AS for any damages resulting
from any improper use or sale.
© 2005, Chipcon AS. All rights reserved.
SWRA062
Page 22 of 23
Application Note AN030
9.
Address Information
Web site:
E-mail:
Technical Support Email:
Technical Support Hotline:
http://www.chipcon.com
wireless@chipcon.com
support@chipcon.com
+47 22 95 85 45
Headquarters:
Chipcon AS
Gaustadalléen 21
NO-0349 Oslo
NORWAY
Tel: +47 22 95 85 44
Fax: +47 22 95 85 46
E-mail: wireless@chipcon.com
US Offices:
Chipcon Inc., Western US Sales Office
19925 Stevens Creek Blvd.
Cupertino, CA 95014-2358
USA
Tel: +1 408 973 7845
Fax: +1 408 973 7257
Email: USsales@chipcon.com
Chipcon Inc., Eastern US Sales Office
35 Pinehurst Avenue
Nashua, New Hampshire, 03062
USA
Tel: +1 603 888 1326
Fax: +1 603 888 4239
Email: eastUSsales@chipcon.com
Sales Office Germany:
Chipcon AS
Riedberghof 3
D-74379 Ingersheim
GERMANY
Tel: +49 7142 9156815
Fax: +49 7142 9156818
Email: Germanysales@chipcon.com
Sales Office Asia:
Sales Office Korea & South-East Asia:
Chipcon AS
Unit 503, 5/F
Silvercord Tower 2, 30 Canton Road
Tsimshatsui, Hong Kong
Tel: +852 3519 6226
Fax: +852 3519 6520
Email: Asiasales@chipcon.com
Chipcon AS
37F, Asem Tower
159-1 Samsung-dong, Kangnam-ku
Seoul 135-798 Korea
Tel: +82 2 6001 3888
Fax: +82 2 6001 3711
Email:KAsiasales@Chipcon.com
Sales Office Japan:
Chipcon AS
#403, Bureau Shinagawa
4-1-6, Konan, Minato-Ku,
Tokyo, Zip 108-0075
Japan
Tel: +81 3 5783 1082
Fax: +81 3 5783 1083
Email: Japansales@chipcon.com
Chipcon AS is an ISO 9001:2000 certified company
SWRA062
Page 23 of 23