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CC1120EM-868-915-RD: CC1120EM-868-915-RD

PAVANAKUMAR A G
Prodigy 60 points
Part Number: CC1120EM-868-915-RD
Other Parts Discussed in Thread: CC1190, CC1120

Tool/software:

I am working on a CC1120 + CC1190 custom board with a carrier frequency of 868 MHz, using the following configuration:

  • Bit rate: 1.2 kbps
  • RX filter bandwidth: 50 kHz
  • Modulation format: 2-FSK
  • Frequency deviation: 24.96 kHz
  • Transmit power: 27 dBm

I configured the registers as per SmartRF Studio:

{IOCFG3, 0x06},
{IOCFG2, 0x06},
{IOCFG1, 0xB0},
{IOCFG0, 0x06},
{SYNC3, 0xD3},
{SYNC2, 0x91},
{SYNC1, 0xD3},
{SYNC0, 0x91},
{SYNC_CFG1, 0x0B},
{DEVIATION_M, 0x99},
{MODCFG_DEV_E, 0x05},
{DCFILT_CFG, 0x15},
{PREAMBLE_CFG1, 0x18},
{FREQ_IF_CFG, 0x3A},
{IQIC, 0x00},
{CHAN_BW, 0x04},
{MDMCFG0, 0x05},
{SYMBOL_RATE2, 0x43},
{SYMBOL_RATE1, 0xA9},
{SYMBOL_RATE0, 0x2A},
{AGC_REF, 0x3C},
{AGC_CS_THR, 0xEF},
{AGC_CFG1, 0xA9},
{AGC_CFG0, 0xC0},
{FIFO_CFG, 0x00},
{SETTLING_CFG, 0x0B},
{FS_CFG, 0x12},
{PKT_CFG2, 0x04},
{PKT_CFG1, 0x04},
{PKT_CFG0, 0x20},
{PA_CFG2, 0x77},
{PA_CFG1, 0x56},
{PA_CFG0, 0x7E},
{PKT_LEN, 0xFF},
{IF_MIX_CFG, 0x00},
{FREQOFF_CFG, 0x20},
{FREQ2, 0x6C},
{FREQ1, 0x80},
{FS_DIG1, 0x00},
{FS_DIG0, 0x5F},
{FS_CAL1, 0x40},
{FS_CAL0, 0x0E},
{FS_DIVTWO, 0x03},
{FS_DSM0, 0x33},
{FS_DVC0, 0x17},
{FS_PFD, 0x50},
{FS_PRE, 0x6E},
{FS_REG_DIV_CML, 0x14},
{FS_SPARE, 0xAC},
{FS_VCO0, 0xB4},
{XOSC5, 0x0E},
{XOSC1, 0x03},

I have enabled PA_EN for transmission and LNA_EN for reception.

Issue:

The transmitter and receiver communicate successfully only when they are placed very close to each other (within a few centimeters). However, when I increase the distance beyond 1 meter, the receiver fails to receive any data.

  • Are there any additional registers or settings that I need to adjust to improve the communication range?
  • Should I fine-tune the AGC reference level or RX filter bandwidth for better reception sensitivity?

Any guidance or recommendations would be greatly appreciated.

Thanks in advance!

  • 0
    TI__Mastermind 32600 points

    Hi,

    The failure description is strange that communication only works when they are placed closed to each other. I would expect problems when they are placed so close since the signal strength should be too strong especially when you have 27 dBm output power. At this distance you should be able to achieve a link without an antenna. 

    Can you please look at the conducted output power levels first before making any radiated tests with an antenna ?

    Please check your output power level and Tx harmonics as the first steps in evaluating your board.

    Can you post your schematic ?

    Thanks.

  • 0 in reply to RGW
    Prodigy 60 points

    Thank you for the reply. In my design, PA_EN and LNA_EN are not directly connected to the controller. How can I enable PA_EN and LNA_EN through register configuration? Also, can you confirm if my register configuration is correct?

  • 0 in reply to PAVANAKUMAR A G
    TI__Mastermind 32600 points

    This is described in the application note: https://www.ti.com/lit/swra387