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CC110L: FCC - modulation change

Part Number: CC110L


we have to pass FCC certification

in the original application, we were in GFSK with deviation 20k and RX bandwidth 100k

With this configuration, product target 15.249 of the FCC which limits a lot TX power

To pass FCC, we have to set PATABLE to 0dB

After discussion with the lab and checking DN006 (SWRA123B) we tried to switch to 2FSK.

Sensiility is lowered in this mode because of RX bandwidth but we can increase power (0xC9 for PATABLE in DN006)

But after a RF range test, we observe that result is worse with this new set of parameter.

Is it normal?     

Configurations are detailled below 

GFSK: for deviation of 20k with PATABLE 0x88

2FSK: config with deviation of 177k with PATABLE 0xC9


Olivier D

#define IOCFG2 0x07 //// IOCFG2 GDO2 output pin configuration.
#define IOCFG1 0x2E
#define IOCFG0 0x00 // // IOCFG0D GDO0 output pin configuration. Refer to SmartRF® Studio User Manual for detailed pseudo register explanation.
#define SYNC_HI 0xD3 // // Synchro Word High
#define SYNC_LO 0x91 //// Synchro Word Low
#define PKTLEN 0xFF //// PKTLEN Packet length.
#define PKTCTRL1 0x08 // // PKTCTRL1 Packet automation control.
#define PKTCTRL0 0x05 //// PKTCTRL0 Packet automation control.
#define ADDR 0x00 //// ADDR Device address.
#define CHANNR 0x00 // // CHANNR Channel number.
#define FSCTRL1 0x06
#define FSCTRL0 0x00 //// FSCTRL0 Frequency synthesizer control.

#ifdef _GFSK
#define FREQ2 0x23 // FREQ2 Frequency control word, high byte.
#define FREQ1 0x14 // FREQ1 Frequency control word, middle byte.
#define FREQ0 0x35 // FREQ0 Frequency control word, low byte.
#define MDMCFG4 0xC9 // MDMCFG4 Modem configuration.
#define MDMCFG2 0x13 // MDMCFG2 Modem configuration.
#define DEVIATN 0x34 // DEVIATN Modem deviation setting (when FSK modulation is enabled).
#define TEST2 0x81 // TEST2 Various test settings.
#define TEST1 0x35 // TEST1 Various test settings.
#define FIFOTHR 0x0D // Seuil a 55 en RX
#ifdef _2FSK
#define FREQ2 0x23 // FREQ2 Frequency control word, high byte.
#define FREQ1 0x14 // FREQ1 Frequency control word, middle byte.
#define FREQ0 0x35 // FREQ0 Frequency control word, low byte.
#define MDMCFG2 0x13 // MDMCFG2 Modem configuration.
#define MDMCFG4 0x2A // MDMCFG4 Modem configuration
#define DEVIATN 0x66
#define TEST2 0x88 // TEST2 Various test settings.
#define TEST1 0x31 // TEST1 Various test settings.
#define FIFOTHR 0x07 // Seuil a 55 en RX

#define MDMCFG3 0x83 //// MDMCFG3 Modem configuration.
#define MDMCFG1 0x22 //// MDMCFG1 Modem configuration.
#define MDMCFG0 0xF8 //// MDMCFG0 Modem configuration.
#define MCSM2 0x07 ////MCSM2 Main RAdio Control State Machine configuration
#define MCSM1 0x03 // // MCSM1 Main Radio Control State Machine configuration.
#define MCSM0 0x18
#define FOCCFG 0x16
#define BSCFG 0x6C // BSCFG Bit synchronization Configuration.
#define AGCCTRL2 0x43 // AGCCTRL2 AGC control.
#define AGCCTRL1 0x40 // AGCCTRL1 AGC control.
#define AGCCTRL0 0x91 // AGCCTRL0 AGC control.
#define WOREVT1 0x87
#define WOREVT0 0x6B
#define WORCTRL 0xF8
#define FREND1 0x56 // FREND1 Front end RX configuration.
#define FREND0 0x10 // FREND0 Front end RX configuration.
#define FSCAL3 0xE9
#define FSCAL2 0x2A
#define FSCAL1 0x0
#define FSCAL0 0x1F
#define RCCTRL1 0x41
#define RCCTRL0 0x00
#define FSTEST 0x59 // FSTEST Frequency synthesizer calibration.
#define PTEST 0x7F
#define AGCTST 0x3F
#define TEST0 0x09 // TEST0 Various test settings.

  • Hi,

    Changing from GFSK to FSK will not significantly affect the range. The main parameter affecting the range is the link budget. With FCC 15.247, the link budget is improved compared to FCC 15.249 mainly due to the output power. With FCC 15.249, the output power should not exceed 0 dBm according to the regulations.

  • Hi,

    Yes having a 500kHz bandwidth allows a higher output power.
    That's why I increased power to 0xC9 like in DN006 (6.2dB at 915MHz).
    But when I compare both solutions with RF range tests (2 products communicating RX/TX)
    then I get better results when RX bandwidth is small even if TX power is lower.

    Is it possible than RX sensibility is more degraded than TX power is improved?

    In the DN006 PATABLE is limited to 0xC9, is there a reason to limit it.
    Does it mean that if we increase to 0xC0, other criteria for FCC aren't fulfilled???
    Because at higher power, I could increase RF range.

    Olivier D

  • Hi,

    Increasing the power is limited by the peak power spectral density at any 3 kHz bandwidth shall not exceed +8 dBm.

    According to Table 5 in the DN006 app note, a data rate of 2.4 kbps, output power of 7.5 dBm will give the best range / link budget of 115.5 dB. If you increase the output power, then you will need to increase the bandwidth which will give a lower range / link budget.

  • Hi, 

    so based on this DN006 those settings are valid for Texas demoboard

    we will check if tests in open field confirm this with our application.