• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 53 subscribers
  • Views 502 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Using CC430 + CC1190 with frequency hopping in 869.4-869.650 MHz band in EU

Dragos Ionescu
Intellectual 680 points

Hi, since the allowed bandwidth is only 250KHz are there any settings that allows me to do some frequency hopping with the mentioned hardware?

I can use a lower bitrate (4.8 or 9.6kbps is OK). In DN005, table 1 it is specified that at 10kbbps the frequency offset is 70KHz. If I divide 250KHz by 70 KHz I can get 3 different channels. Similar, for 4.8kbps I can get 5 channels.

Are my assumptions correct?

Thanks

  • 0
    TI__Guru**** 317180 points

    No but yes. The table show how large frequency offset a given setting can handle, the number of channels are given by the Rx bandwidth but since the minimum Rx bandwidth is 58 kHz the result is the same, you will be able to use 3 or 4 channels dependent on which channel spacing you select.

  • 0 in reply to TER
    Intellectual 680 points

    Thanks, one more thing I don't understand:

    If the Base freq is 868MHz and deviation 20KHz my understanding is that the freq at the TX side will swing between 867.98 MHz to 868.02 Mhz. Is this correct? If yes, don't we have the minimum freq in the channel (868Mhz) overlapped?

    Dragos

  • 0 in reply to Dragos Ionescu
    Intellectual 680 points

    Based on this thread (last post) I've done the following computations:

    Desired bitrate: 9.6kbps, ppm_xtal = 10, modulation index =1

    1. f_dev = data_rate / 2 = 9.6 / 2 = 4.8 

    2. Signal BW = data_rate + 2 * f_Dev = 9.6 + 2 * 4.8 = 19.2

    3. Rx BW = Signal BW + 4 * ppm_xtal * Frequency of operation = 19.2 + 4 * 10 * 1e-6 * 868 * 1e3=53.92KHz which has to be increased to the minimum value from the datasheet: 58KHz

    4. The channel spacing should be more than RxBW, since I have 250KHz available I will distribute the space evenly so:

     Channel_spacing = 250 / 4 = 62.5KHz > 58KHz

    Are these settings OK? Should the modulation format be only 2 - FSK?

    Thanks,

    Dragos