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CC1201: CC1201 about Sensitivity

user4766611
Intellectual 380 points
Part Number: CC1201

follow the RM 

we test 2 cc1201 dk, 

840MHz

40MHz

500ksps

500kbps

833.333333KHz

2FSK

124.816895kHz

14dBm

TX: +14db;

using the RF studio 7 SW:

expert mode: Symbol rate:500ksps，4-GFSK,max throughput, ETSI Standard(868MHz)

PKT_CFG1 = 00
PKT_CFG0 = 00
PKT_LEN = 0x20

Packet TX: Add Seq. Number
choose HEX: 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e
                send 100 packets;

Packet RX: Seq.Number included in Payload

recieved OK: 100
received not OK; 0
Packet Error Rate: 0
Bit Error Rate: 0

attenuation 100db,so the RX Sensitivity is 14-100=-86db,

the figure above show the 500kbps 2-GMSK,CHF=833kHz
, sensitivity is -97.

why our test is below 11db??

  • 0
    TI__Guru**** 317180 points

    You send a 30 byte and have 0 % PER. How do you conclude that you have a sensitivity equal to -86 dBm? 

    The sensitivity in the datasheet is measured with a 3 byte fixed length payload and a 20 % PER limit. If you want o compare with the numbers in the datasheet the easiest would be to use the same packet length and PER limit. 

  • 0 in reply to TER
    Intellectual 380 points

    thanks.

    PKT_LEN = 0x20, 

    tx: send 32byte;

    TX: +14db;

    if attenuation 101db, rx "Bit Error Rate" is bigger than 0, "received not OK"  is bigger than 0.

    if if attenuation 100db, rx "Bit Error Rate" is 0, "received not OK"  is  0,.

  • 0 in reply to user4766611
    TI__Guru**** 317180 points

    Have you tried to do the test with the same packet length and PER limit as in the datasheet? 

  • 0 in reply to TER
    Intellectual 380 points

    There are some issues in the RF studio 7 , when we test cc1201 send and receive.

    [ENV]

    1. CC1201_dk_A   as   TX:

    TX: +14db;

    Using the RF studio 7 SW:

    expert mode: Symbol rate: 1.2kbps , 2-FSK,DEV=20kHzCHF=50kHz (868MHz)

    PKT_CFG1 = 0x00

    PKT_CFG0 = 0x00

    PKT_LEN =  0x03

    Packet TX: Add Seq. Number

    choose HEX: F2

    send  1000  packets;

     

    2. attenuation 132db,

     

    3. CC1201_dk_B

    Packet RX: Seq.Number included in Payload

    Average RSSI: 0.0 dBm

    recieved OK:  999

    received not OK: 417

    Packet Error Rate: 29.4%

    Bit Error Rate:  0.87%

     

    [result]

    In the fact, the rx can received corrected 999 packets.

    The PER is 1/1000=0.1%?

    Why the SmartRF Studio 7 show PER 29.4%?  I cannot understand it.


     

  • 0 in reply to user4766611
    TI__Guru**** 317180 points

    This is a bug in SMartRF Studio caused by the sequence number. If remember correctly, SmartRF Studio uses the sequence numbers to calculate the PER and when you in this case fail to receive sequence number 416, Studio assumes that you have lost a lot of packets. 

    This was seen in this thread: https://e2e.ti.com/support/wireless-connectivity/other-wireless/f/667/t/637504 

  • 0 in reply to TER
    Intellectual 380 points
    follow your opinion:
    一、1.2kbps ,
    2-FSK,DEV=20kHzCHF=50kHz，TX: +14db;
    1. attenuation 133db,PER=30%,ber=1.9%;
    2. attenuation 131db,PER=7%,BER=0.18%;
    3. attenuation 130db,PER=0,BER=0;
    二、500kbps , 2-FSK,DEV=124.8kHz CHF=833.33kHz，TX:+14dbm;
    1. attenuation 110db,PER=27%,ber=0.8%;
    2. attenuation 109db,PER=15.9%,BER=0.4%;
    3. attenuation 108db,PER=1.4%,BER=0.04%;
    maybe something is below your suggestion value.
  • 0 in reply to user4766611
    TI__Guru**** 317180 points

    Do you know that the output power is exact -14 dBm (measured conducted) and that the attenuation is exactly the number you state? 

    My experience with using attenuation is that some of the signal leaks over the air etc meaning that the sensitivity measured with this method is typically a few dB off. I assume that your RX board is inside a shield? Having a signal generator to do this type of tests is preferred. 

  • 0 in reply to TER
    Intellectual 380 points

    thanks for your reply.

    we test the output 14db, and test the attenuation.

    the cc1201 board is in the shlied box .

    another question:

    can we use the -174+NF+10lgB+10lgSNR to calculate the cc1201 receive Sensitivity?

    follow the cc1201 document, 

    1） 1Mbps,4-GFSK,DEV=400kHz,CHF=1.66MHz  ， -97dbm;

    2）1.2kbps ,2-FSK,DEV=20kHzCHF=50kHz，   -11dbm;

    1).CHF1.66mhz  divider  2).CHF50KHZ is 33.   lg33=1.5,   so the difference sensitivity of 1) and 2) is 10*lg(1.66M/50K) , about 15dbm?

  • 0 in reply to user4766611
    TI__Guru**** 317180 points

    Yes, -174+NF+10lgB+10lgSNR can be used to estimate sensitivity. Note that the SNR will not be equal for all datarates and modulation formats. 

    Not following your last line since for me it's not clear exactly what you are calculating. Are you trying to use the equation to calculate the sensitivity? In that case, which SNR do you use since the SNR required is higher for 4-GFSK/ zero IF compared to 2-FSK/IF.