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CC2500: doppler handling capability

Part Number: CC2500
Other Parts Discussed in Thread: CC1101,

What will the range of doppler frequencies supported by the

device CC2500 and CC1101.

For one application, the receiver is moving fast and expected doppler frequency is 8 KHz at 2.4 GHZ

and 3 KHz in 900 MHz

whether the above two devices can handle this doppler frequencies in the

frequency offset compensation algorithm.

In Page 81 of CC2500 datasheet it is mentioned that "the  range of frequency offset estimate range from

the demodulator" is +/-202 KHZ.  If this is the case, whether it can support the above mentioned

doppler frequencies.

thank you

I.Mahalakshmi

  • Hello,

    haha, yes the receiver would be moving quite fast to experience that much doppler shift.

    The relevant portion of the datasheet would be section 14.1 which describes the registers involved in the frequency offset compensation. In particular the FOCCFG register:

    The maximum compensated offset is dependent on the channel bandwidth and this setting, and within the limit of the register you described above. See https://www.ti.com/lit/ml/swra181/swra181.pdf for more information on the relation between sensitivity and frequency offset.

    Thanks,

    Jake

  • Thanks for the reply,

    So i consider that the device can handle this range of doppler effect, 8 KHz.

    The datasheet says, the crystal oscillator frequency offset itself may be in 100 s of KHZ.

    Whether handling crystal oscillator offset and the doppler shift will need same capability from the receiver.

    thank you

    I.Mahalakshmi

  • All of your tolerances are additive so it is dependent on your system design. Parameters crystal manufacturing tolerances, crystal load capacitor tolerances, performance over temperature, your required sensitivity will need to be evaluated by you to determine whether or not it meets your requirements. The receiver is going to see the offset due to doppler shift the same as any other offset and it will be on top of any shift due to crystal ppm tolerance.

    Jake