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CC1200: AGC_REF and IFAMP_BW Wrong equations

Alessandro Fulignani
Intellectual 530 points
Part Number: CC1200

Good Afternoon,

We are implementing some of the equation explained in the CC1200 user's manual and Smart RF studio.

But if you select the first standard modulation (1.2kbs,2fsk,12.5Khz BW) you can see that the AGC_Reference value is 20h.

If you use the equations provided on RF studio, the results below 100Khz doesn't match with the equations!

This is the result expected by equation ---> RX filter BW AGC_REFERENCE      10 kHz 0x2F (MDMCFG1.DVGA_GAIN = 0, RSSI offset ≈ −99 dB)

This is the result given by the RF studio selecting the first setting (1.2kbs,2fsk,12.5Khz BW) --> [7:0] AGC_REFERENCE = 0x20

 

The same happend with the IFAMP_BW calculation.

This is the equation given on RF studio --- > Single Side BW > f_IF+(RX Filter BW/2)

If you load the standard setting ( 50Ksps, 2gfsk ieee 802.15.4g ) the RF studio gives IFAMP_BW  = 01 ( 600Khz ) but if you apply the above equation, should be 300Khz.

But if test the system with two TI board CC120xEM 868/930(using the above settings) and using the RF studio parameter, you get (as expected) slightly worse result then using the value given by the equation. ( Less BW means less noise..)

 

Can you please check if the equations are correct and/or if the RF studio is calculating correctly the value? 

Thank you,

Alex

 

 

 

  • 0
    TI__Mastermind 27145 points

    Hi,

    We will look into it and get back to you ASAP. Please bear with us.

    Thanks,

    PM

  • 0 in reply to PM
    TI__Mastermind 27145 points

    Hi,

    Yes, I agree with your findings.

    We recommend to use the Settings from the SmartRF Studio.

    Please download the latest version (2.15.0) of SmartRF Studio from TI Website.

    Thanks,

    PM

  • 0 in reply to PM
    Intellectual 530 points

    Sir.

    In my application i can not use the (buggy) smartRF studio. The application need to adapt several parametrs based on some given condition.

    Now, the question is if you can provide or not a meaningfull answer.

    Onestly sir, if you expect to sell yours RF devicecs in this way, why write a datasheet?

    Just print on a piece of paper " Use only with SmartRF Studio".

    Said that i need to know how to move forward.

    If this is your last answer i will just push it to TI Sales rep, then it will be a TI internal decision if follow or not this project.

    Let me know your opinion.

    Thank you,

    Alex

    .

  • 0 in reply to Alessandro Fulignani
    TI__Mastermind 27145 points

    Hi,

    We understand your concerns but the following is our explanation.

    We  mentioned the following in our User Guide about the AGC Reference. Please see the underlined portion. It shows the Equation is a Rule of thumb.

    We started with that equation and optimized the AGC Reference to achieve better performance.  There is nothing wrong in using the Formula but it may not be an optimum value.

    "AGC_REF.AGC_REFERENCE:

    Sets the reference value for the AGC. The reference value is a compromise between

    blocker tolerance/selectivity and sensitivity. The AGC reference level must be higher than

    the minimum SNR to the demodulator. The AGC reduces the analog front end gain when

    the magnitude output from the channel filter is greater than the AGC reference level. An

    optimum AGC reference level is given by several conditions, but a rule of thumb is given by

    Equation 11.

    AGC_REFERENCE = 10 log (RX FILTER BW )- 92 - RSSI_OFFSET

    "

    The above explanation applies to IFAMP_BW also.

    Thanks,

    PM

  • 0 in reply to PM
    Intellectual 530 points

    Hi PM,

    Thank you for your answer. And i understand your position.

    I wonder if it would be possible to have a review on some of our configurations...May be  3...

    Is it possible to have the source file that you use to program the cc1200 with RFstudio?

    That's because most of your examples are not in the bitrate range that we need to use.

    Thank you.

    ALex

  • 0 in reply to Alessandro Fulignani
    TI__Mastermind 27145 points

    Hi,

    Please let us know your RF Parameters then we will generate the Register settings and send it to you.

    Carrier Freq:

    Symbol Rate:

    Modulation:

    Deviation:

    No, it is not possible to provide you the Source file for the SmartRF Studio. The file in not dedicated to one chip.

    Thanks,

    PM

     

  • 0 in reply to PM
    TI__Mastermind 27145 points

    Hi,

    As we don't see any reply from the past 1 week, I am going to close this thread.

    If you want you can reopen or start a new thread.

    Thanks,

    PM

  • 0 in reply to PM
    Intellectual 530 points

    Hi,

    Sorry, i was traveling in places with no internet connections.

    Here my requirements:

    1)

    Carrier Freq: 865

    Symbol Rate: 5Ks(10Kbit)

    Modulation: 4 GFSK

    Deviation: 4 KHz

    2)

    Carrier Freq: 869

    Symbol Rate:8Ks(16Kbit)

    Modulation:4GFSK

    Deviation:6KHz

    3)

    Carrier Freq: 864

    Symbol Rate:18Ks(36Kbit)

    Modulation:4GFSK

    Deviation:13KHz

    4)

    Carrier Freq: 868

    Symbol Rate:25Ks(50Kbit)

    Modulation:4GFSK

    Deviation:18KHz

    we may need to step from 4GFSK to 2GFSK. May we leave everything as it is, just changing the deviation to keep the Mod Index around 0.75?

    Based on our test and analysis with a TEK RSA518b we have found a good compromise with a Mod Index of 0.75...

    May i considerer your suggested parameters valid for the whole range 863-870?

    Is there a way to see the base band demodulated signal?

    Thank you very much for your help.

    Alex

  • 0 in reply to Alessandro Fulignani
    TI__Mastermind 27145 points

    Hi,

    Please note that the Preamble and Sync word is sent using 2-GFSK, when we select 4-GFSK mode. Please refer to section 5.2 in User Guide for more information.

    Is this acceptable for you?

    Why are you using 4-GFSK for such a low data rate?

    Thanks,

    PM

  • 0 in reply to PM
    Intellectual 530 points

    Hi,

    Answer:

    1) Yes i'm aware of that.

    2) BW efficency. Shorter TX time.

    New question:

    Cheking the effectivness of the IF filter we see that the programmed BW on the RF studio it is a 6dB BW more then a 3dB BW.

    We did this test using a 1 ppm 40MHz TCXO for the CC1200  and a R&S SMB100A as RFgenerator.

    We did the test reading the RF Sstudio RSSI (And a bolometer connected to a directional coupler) to search for the 3dB BW.

    That would explain why we see a derating of the EVM (Error vector magnitude) when the outer symbols are about 1Khz close to the edge BW...

    Can you confirm that?

    Thank you

    Alex

  • 0 in reply to Alessandro Fulignani
    TI__Mastermind 27145 points

    Hi Alex,

    Attached are the RF Settings files.

    Please note that I haven't tested with these settings. Please test it and let us know.

    Thanks,

    PM

    CC1200-5KSPS-4GFSK.c 
    // Rf settings for CC1200
RF_SETTINGS code rfSettings = {5KBPS, 4KHz Dev, 4GFSK, 25KHz Filter BW 
    0x06,  // IOCFG2              GPIO2 IO Pin Configuration
    0xA8,  // SYNC_CFG1           Sync Word Detection Configuration Reg. 1
    0xD1,  // DEVIATION_M         Frequency Deviation Configuration
    0x28,  // MODCFG_DEV_E        Modulation Format and Frequency Deviation Configur..
    0x8A,  // PREAMBLE_CFG0       Preamble Detection Configuration Reg. 0
    0xC8,  // IQIC                Digital Image Channel Compensation Configuration
    0x61,  // CHAN_BW             Channel Filter Configuration
    0x42,  // MDMCFG1             General Modem Parameter Configuration Reg. 1
    0x05,  // MDMCFG0             General Modem Parameter Configuration Reg. 0
    0x60,  // SYMBOL_RATE2        Symbol Rate Configuration Exponent and Mantissa [1..
    0x62,  // SYMBOL_RATE1        Symbol Rate Configuration Mantissa [15:8]
    0x4E,  // SYMBOL_RATE0        Symbol Rate Configuration Mantissa [7:0]
    0x21,  // AGC_REF             AGC Reference Level Configuration
    0xEE,  // AGC_CS_THR          Carrier Sense Threshold Configuration
    0x11,  // AGC_CFG1            Automatic Gain Control Configuration Reg. 1
    0x94,  // AGC_CFG0            Automatic Gain Control Configuration Reg. 0
    0x00,  // FIFO_CFG            FIFO Configuration
    0x12,  // FS_CFG              Frequency Synthesizer Configuration
    0x00,  // PKT_CFG2            Packet Configuration Reg. 2
    0x20,  // PKT_CFG0            Packet Configuration Reg. 0
    0xFF,  // PKT_LEN             Packet Length Configuration
    0x1C,  // IF_MIX_CFG          IF Mix Configuration
    0x03,  // TOC_CFG             Timing Offset Correction Configuration
    0x02,  // MDMCFG2             General Modem Parameter Configuration Reg. 2
    0x56,  // FREQ2               Frequency Configuration [23:16]
    0x80,  // FREQ1               Frequency Configuration [15:8]
    0xEE,  // IF_ADC1             Analog to Digital Converter Configuration Reg. 1
    0x10,  // IF_ADC0             Analog to Digital Converter Configuration Reg. 0
    0x04,  // FS_DIG1             Frequency Synthesizer Digital Reg. 1
    0x50,  // FS_DIG0             Frequency Synthesizer Digital Reg. 0
    0x40,  // FS_CAL1             Frequency Synthesizer Calibration Reg. 1
    0x0E,  // FS_CAL0             Frequency Synthesizer Calibration Reg. 0
    0x03,  // FS_DIVTWO           Frequency Synthesizer Divide by 2
    0x33,  // FS_DSM0             FS Digital Synthesizer Module Configuration Reg. 0
    0xF7,  // FS_DVC1             Frequency Synthesizer Divider Chain Configuration ..
    0x0F,  // FS_DVC0             Frequency Synthesizer Divider Chain Configuration ..
    0x00,  // FS_PFD              Frequency Synthesizer Phase Frequency Detector Con..
    0x6E,  // FS_PRE              Frequency Synthesizer Prescaler Configuration
    0x1C,  // FS_REG_DIV_CML      Frequency Synthesizer Divider Regulator Configurat..
    0xAC,  // FS_SPARE            Frequency Synthesizer Spare
    0xB5,  // FS_VCO0             FS Voltage Controlled Oscillator Configuration Reg..
    0x09,  // IFAMP               Intermediate Frequency Amplifier Configuration
    0x0E,  // XOSC5               Crystal Oscillator Configuration Reg. 5
    0x03,  // XOSC1               Crystal Oscillator Configuration Reg. 1
};

    CC1200-8KSPS-4GFSK.c 
    // Rf settings for CC1200
RF_SETTINGS code rfSettings = {8KBPS, 6KHz Dev, 4GFSK, 30KHz FilterBW
    0x06,  // IOCFG2              GPIO2 IO Pin Configuration
    0xA8,  // SYNC_CFG1           Sync Word Detection Configuration Reg. 1
    0x3A,  // DEVIATION_M         Frequency Deviation Configuration
    0x29,  // MODCFG_DEV_E        Modulation Format and Frequency Deviation Configur..
    0x8A,  // PREAMBLE_CFG0       Preamble Detection Configuration Reg. 0
    0xC8,  // IQIC                Digital Image Channel Compensation Configuration
    0x8E,  // CHAN_BW             Channel Filter Configuration
    0x42,  // MDMCFG1             General Modem Parameter Configuration Reg. 1
    0x05,  // MDMCFG0             General Modem Parameter Configuration Reg. 0
    0x6A,  // SYMBOL_RATE2        Symbol Rate Configuration Exponent and Mantissa [1..
    0x36,  // SYMBOL_RATE1        Symbol Rate Configuration Mantissa [15:8]
    0xE3,  // SYMBOL_RATE0        Symbol Rate Configuration Mantissa [7:0]
    0x21,  // AGC_REF             AGC Reference Level Configuration
    0xEE,  // AGC_CS_THR          Carrier Sense Threshold Configuration
    0x11,  // AGC_CFG1            Automatic Gain Control Configuration Reg. 1
    0x94,  // AGC_CFG0            Automatic Gain Control Configuration Reg. 0
    0x00,  // FIFO_CFG            FIFO Configuration
    0x12,  // FS_CFG              Frequency Synthesizer Configuration
    0x00,  // PKT_CFG2            Packet Configuration Reg. 2
    0x20,  // PKT_CFG0            Packet Configuration Reg. 0
    0xFF,  // PKT_LEN             Packet Length Configuration
    0x1C,  // IF_MIX_CFG          IF Mix Configuration
    0x03,  // TOC_CFG             Timing Offset Correction Configuration
    0x02,  // MDMCFG2             General Modem Parameter Configuration Reg. 2
    0x56,  // FREQ2               Frequency Configuration [23:16]
    0xE6,  // FREQ1               Frequency Configuration [15:8]
    0x66,  // FREQ0               Frequency Configuration [7:0]
    0xEE,  // IF_ADC1             Analog to Digital Converter Configuration Reg. 1
    0x10,  // IF_ADC0             Analog to Digital Converter Configuration Reg. 0
    0x04,  // FS_DIG1             Frequency Synthesizer Digital Reg. 1
    0x50,  // FS_DIG0             Frequency Synthesizer Digital Reg. 0
    0x40,  // FS_CAL1             Frequency Synthesizer Calibration Reg. 1
    0x0E,  // FS_CAL0             Frequency Synthesizer Calibration Reg. 0
    0x03,  // FS_DIVTWO           Frequency Synthesizer Divide by 2
    0x33,  // FS_DSM0             FS Digital Synthesizer Module Configuration Reg. 0
    0xF7,  // FS_DVC1             Frequency Synthesizer Divider Chain Configuration ..
    0x0F,  // FS_DVC0             Frequency Synthesizer Divider Chain Configuration ..
    0x00,  // FS_PFD              Frequency Synthesizer Phase Frequency Detector Con..
    0x6E,  // FS_PRE              Frequency Synthesizer Prescaler Configuration
    0x1C,  // FS_REG_DIV_CML      Frequency Synthesizer Divider Regulator Configurat..
    0xAC,  // FS_SPARE            Frequency Synthesizer Spare
    0xB5,  // FS_VCO0             FS Voltage Controlled Oscillator Configuration Reg..
    0x09,  // IFAMP               Intermediate Frequency Amplifier Configuration
    0x0E,  // XOSC5               Crystal Oscillator Configuration Reg. 5
    0x03,  // XOSC1               Crystal Oscillator Configuration Reg. 1
};

    CC1200-18KSPS-4GFSK.c 
    // Rf settings for CC1200
RF_SETTINGS code rfSettings = {18KSPS, 13KHz Dev, 4GFSK, 60KHz Filter BW
    0x06,  // IOCFG2              GPIO2 IO Pin Configuration
    0xA8,  // SYNC_CFG1           Sync Word Detection Configuration Reg. 1
    0x55,  // DEVIATION_M         Frequency Deviation Configuration
    0x2A,  // MODCFG_DEV_E        Modulation Format and Frequency Deviation Configur..
    0x8A,  // PREAMBLE_CFG0       Preamble Detection Configuration Reg. 0
    0xC8,  // IQIC                Digital Image Channel Compensation Configuration
    0x87,  // CHAN_BW             Channel Filter Configuration
    0x42,  // MDMCFG1             General Modem Parameter Configuration Reg. 1
    0x05,  // MDMCFG0             General Modem Parameter Configuration Reg. 0
    0x7D,  // SYMBOL_RATE2        Symbol Rate Configuration Exponent and Mantissa [1..
    0x7D,  // SYMBOL_RATE1        Symbol Rate Configuration Mantissa [15:8]
    0xBF,  // SYMBOL_RATE0        Symbol Rate Configuration Mantissa [7:0]
    0x24,  // AGC_REF             AGC Reference Level Configuration
    0xEE,  // AGC_CS_THR          Carrier Sense Threshold Configuration
    0x11,  // AGC_CFG1            Automatic Gain Control Configuration Reg. 1
    0x94,  // AGC_CFG0            Automatic Gain Control Configuration Reg. 0
    0x00,  // FIFO_CFG            FIFO Configuration
    0x12,  // FS_CFG              Frequency Synthesizer Configuration
    0x00,  // PKT_CFG2            Packet Configuration Reg. 2
    0x20,  // PKT_CFG0            Packet Configuration Reg. 0
    0x55,  // PA_CFG0             Power Amplifier Configuration Reg. 0
    0xFF,  // PKT_LEN             Packet Length Configuration
    0x1C,  // IF_MIX_CFG          IF Mix Configuration
    0x03,  // TOC_CFG             Timing Offset Correction Configuration
    0x02,  // MDMCFG2             General Modem Parameter Configuration Reg. 2
    0x56,  // FREQ2               Frequency Configuration [23:16]
    0x66,  // FREQ1               Frequency Configuration [15:8]
    0x66,  // FREQ0               Frequency Configuration [7:0]
    0xEE,  // IF_ADC1             Analog to Digital Converter Configuration Reg. 1
    0x10,  // IF_ADC0             Analog to Digital Converter Configuration Reg. 0
    0x04,  // FS_DIG1             Frequency Synthesizer Digital Reg. 1
    0x50,  // FS_DIG0             Frequency Synthesizer Digital Reg. 0
    0x40,  // FS_CAL1             Frequency Synthesizer Calibration Reg. 1
    0x0E,  // FS_CAL0             Frequency Synthesizer Calibration Reg. 0
    0x03,  // FS_DIVTWO           Frequency Synthesizer Divide by 2
    0x33,  // FS_DSM0             FS Digital Synthesizer Module Configuration Reg. 0
    0xF7,  // FS_DVC1             Frequency Synthesizer Divider Chain Configuration ..
    0x0F,  // FS_DVC0             Frequency Synthesizer Divider Chain Configuration ..
    0x00,  // FS_PFD              Frequency Synthesizer Phase Frequency Detector Con..
    0x6E,  // FS_PRE              Frequency Synthesizer Prescaler Configuration
    0x1C,  // FS_REG_DIV_CML      Frequency Synthesizer Divider Regulator Configurat..
    0xAC,  // FS_SPARE            Frequency Synthesizer Spare
    0xB5,  // FS_VCO0             FS Voltage Controlled Oscillator Configuration Reg..
    0x09,  // IFAMP               Intermediate Frequency Amplifier Configuration
    0x0E,  // XOSC5               Crystal Oscillator Configuration Reg. 5
    0x03,  // XOSC1               Crystal Oscillator Configuration Reg. 1
};

    CC1200-25KSPS-4GFSK.c 
    // Rf settings for CC1200
RF_SETTINGS code rfSettings = {25KSPS, 18KHz Dev, 4gfsk, 100KHz Filter BW
    0x06,  // IOCFG2              GPIO2 IO Pin Configuration
    0xA8,  // SYNC_CFG1           Sync Word Detection Configuration Reg. 1
    0xD8,  // DEVIATION_M         Frequency Deviation Configuration
    0x2A,  // MODCFG_DEV_E        Modulation Format and Frequency Deviation Configur..
    0x8A,  // PREAMBLE_CFG0       Preamble Detection Configuration Reg. 0
    0xC8,  // IQIC                Digital Image Channel Compensation Configuration
    0x11,  // CHAN_BW             Channel Filter Configuration
    0x42,  // MDMCFG1             General Modem Parameter Configuration Reg. 1
    0x05,  // MDMCFG0             General Modem Parameter Configuration Reg. 0
    0x84,  // SYMBOL_RATE2        Symbol Rate Configuration Exponent and Mantissa [1..
    0x7A,  // SYMBOL_RATE1        Symbol Rate Configuration Mantissa [15:8]
    0xE1,  // SYMBOL_RATE0        Symbol Rate Configuration Mantissa [7:0]
    0x26,  // AGC_REF             AGC Reference Level Configuration
    0xEE,  // AGC_CS_THR          Carrier Sense Threshold Configuration
    0x11,  // AGC_CFG1            Automatic Gain Control Configuration Reg. 1
    0x94,  // AGC_CFG0            Automatic Gain Control Configuration Reg. 0
    0x00,  // FIFO_CFG            FIFO Configuration
    0x12,  // FS_CFG              Frequency Synthesizer Configuration
    0x00,  // PKT_CFG2            Packet Configuration Reg. 2
    0x20,  // PKT_CFG0            Packet Configuration Reg. 0
    0x54,  // PA_CFG0             Power Amplifier Configuration Reg. 0
    0xFF,  // PKT_LEN             Packet Length Configuration
    0x1C,  // IF_MIX_CFG          IF Mix Configuration
    0x03,  // TOC_CFG             Timing Offset Correction Configuration
    0x02,  // MDMCFG2             General Modem Parameter Configuration Reg. 2
    0x56,  // FREQ2               Frequency Configuration [23:16]
    0xCC,  // FREQ1               Frequency Configuration [15:8]
    0xCC,  // FREQ0               Frequency Configuration [7:0]
    0xEE,  // IF_ADC1             Analog to Digital Converter Configuration Reg. 1
    0x10,  // IF_ADC0             Analog to Digital Converter Configuration Reg. 0
    0x04,  // FS_DIG1             Frequency Synthesizer Digital Reg. 1
    0x50,  // FS_DIG0             Frequency Synthesizer Digital Reg. 0
    0x40,  // FS_CAL1             Frequency Synthesizer Calibration Reg. 1
    0x0E,  // FS_CAL0             Frequency Synthesizer Calibration Reg. 0
    0x03,  // FS_DIVTWO           Frequency Synthesizer Divide by 2
    0x33,  // FS_DSM0             FS Digital Synthesizer Module Configuration Reg. 0
    0xF7,  // FS_DVC1             Frequency Synthesizer Divider Chain Configuration ..
    0x0F,  // FS_DVC0             Frequency Synthesizer Divider Chain Configuration ..
    0x00,  // FS_PFD              Frequency Synthesizer Phase Frequency Detector Con..
    0x6E,  // FS_PRE              Frequency Synthesizer Prescaler Configuration
    0x1C,  // FS_REG_DIV_CML      Frequency Synthesizer Divider Regulator Configurat..
    0xAC,  // FS_SPARE            Frequency Synthesizer Spare
    0xB5,  // FS_VCO0             FS Voltage Controlled Oscillator Configuration Reg..
    0x09,  // IFAMP               Intermediate Frequency Amplifier Configuration
    0x0E,  // XOSC5               Crystal Oscillator Configuration Reg. 5
    0x03,  // XOSC1               Crystal Oscillator Configuration Reg. 1
};

  • 0 in reply to PM
    Intellectual 530 points

    Hi,

    Thank you. I will test them soon.

    Alex