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CC2642R: Image Frequency, All BLE PHY MOdes

Stuart Baker
Genius 10620 points
Part Number: CC2642R

I'm trying to help a customer find out the Image Frequency for all of the available PHY modes. I found the following E2E posting, but it does not mention if if applies to all PHY modes.

https://e2e.ti.com/support/wireless-connectivity/bluetooth/f/538/t/877175

The Datasheet mentions Image frequency in the datasheet RX characteristic tables, but doesn't really say what the value is. After directing the customer to the datasheet table, here is the followup I received from the customer:

I saw that, but now that I reread it, it is close. 

Note that Image frequency + 1 MHz is the Co- channel –1 MHz.

This note seems to imply that the image frequency is 2 MHz below the center frequency at 1MS/s.

Note that Image frequency + 2 MHz is the Co-channel

This Note seems to imply the same 2MHz below the center at 2MS/s.

Do you agree with this? 

The reason I ask is RF-PHY testing requires you to know the image frequency for the Receiver Selectivity tests as the rejection performance is tested at the receivers image frequency.  RF-PHY/RCV/BV-03-C is one example test.  If there is any way you could verify, that would be great.

Could someone point us in the right direction?

Thanks,

Stuart

  • 0 in reply to TER
    Prodigy 30 points

    Thank you, this helps. 

    The image frequency for the 2MS/s test is -1.7MHz, however the RF-PHY test is performed by sweeping the interferer signal from 2400 MHz to 2482 MHz in increments of 2 MHz, so the interferer frequency will never actually hit the image frequency.  How do I handle this when performing physical layer tests?  The chart has specific levels to adjust the interferer when the interferer is equal to or adjacent to the image frequency, but that will never technically happen in this case. 

    Do I round to -2MHz for the image frequency and when the interferer reaches that frequency adjust for the appropriate level according to the RF-PHY test or do I never adjust for a level associated with an image frequency since we never are equal to or adjacent to the image frequency? 

    Thanks.

     

  • 0 in reply to Bert Downing1
    TI__Guru**** 317180 points

    As I have understand it we have rounded down to - 2 MHz for our testing.