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BPSK modulation using TI RF transmitter IC

Ali Ghamman
Prodigy 110 points
Other Parts Discussed in Thread: CC1125, CC1120, CC1175, CC1310

Hi,

I am looking for a possibilities for BPSK modulation using available RF transmitters. How can I do BPSK modulation using existing TI products?
Is their can specific product which have in-built BPSK modulator? My carrier frequency range is 400-410 MHz
Or can I use any other technique to do BPSK modulation on my carrier signal, like using in-built FSK modulator?
Please advise me.
Thanks

  • 0
    TI__Mastermind 36375 points
    Ali,

    We can perform slow BPSK transmit only (we have done 600 bps), we cannot do receive on this device.

    Regards,
    /TA
  • 0 in reply to TA12012
    Prodigy 110 points
    Hi TA,
    Can you please elaborate how can we do 400bps BPSK transmit only? What technique can we use?
    Thanks
    Ali
  • 0 in reply to Ali Ghamman
    TI__Intellectual 1235 points

    Ali,

    We have performed BPSK on the cc1120 and cc1125. You can set a timer interrupt at 400bps to trigger power ramping and phase shifting. For output power ramping, you will need to control the PA_CFG2 register (see section 7.1 of the cc112x TRM). To shift the phase, you can change the frequency through the FREQOFF1 and FREQOFF0 registers, delay a certain amount of time for a phase shift of 180 degrees, and change the frequency back to its original value (see section 9.12 of the TRM).

    The TRM can be found here: http://www.ti.com/lit/ug/swru295e/swru295e.pdf

  • 0 in reply to skyler
    Prodigy 110 points

    Hi Skyler,

    Thanks allot for your detailed explanation. It is really helpful.

    You said that for phase shifting, change frequency until phase shifts to 180 degrees. How can I calculate that change in value of frequency? And do i need to do FSK modulation settings with a certain Frequency deviation value?

    Can you please elaborate this?
    Thanks
    Ali

  • 0 in reply to Ali Ghamman
    TI__Intellectual 1235 points
    Ali,

    For phase shifting, use the equation 2*pi*delta_frequency = ( delta_phase / delta_time ). Since delta_phase is pi (180 degrees), you can set delta_time = 1/(2*delta_frequency), where delta_frequency = FREQOFF * rf_step (rf_step is listed in Table 31 of the TRM, based on your crystal and rf frequencies). To maintain this timing, I suggest delaying the MCU for a certain number of cycles - this can be dependent on the delay of the SPI port as well.

    Regarding frequency deviation, set CFM_DATA_CFG to 0x01 on the cc1120. This enables custom frequency modulation so that you can program the frequency directly.

    Skyler
  • 0 in reply to skyler
    Prodigy 110 points

    Hi Skyler,

    Thanks for your reply and detailed explanation. I only need transmitter IC, so i selected CC1175. As per its datasheet, it can only be used from 410-480 MHz. I'm looking for some transmitter in 400-410 MHz frequency range with having in built FSK modulation. Can you please suggest me any device produced by TI?
    Thanks
    Ali

  • 0 in reply to Ali Ghamman
    TI__Guru**** 317180 points
    CC1310 should be able to cover the band in question. We have tested that we are able to operate on this frequency but the band is not characterized as per the errata note.
  • 0 in reply to TER
    Prodigy 110 points

    Hi,
    Thanks.
    I am just looking for transmitter only. Can you please tell me about CC1175 for my specified band?

    Thanks

    Ali

  • 0 in reply to Ali Ghamman
    TI__Guru**** 317180 points
    As you pointed out, CC1175 doesn't cover the band you are interested in. The possible frequency bands are listed in the datasheets.