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AWR1243: Receiver in-band P1dB and receiver RF input to I/Q output gain

Jonathan Jones2
Intellectual 680 points
Part Number: AWR1243

Dear Support,

I was wanting to ask if you could help me with the following questions:

In the following post you explained how to calculate the voltage level at the receiver ADC input for a given RF power at the input to the receiver:

e2e.ti.com/.../2258047

So full scale at the I/Q ADC input is 1 Vpeak which is +10dBm at the input to the I/Q ADC (assuming 50ohm input impedance) which for a receive gain of 48dB would correspond to -38dBm CW (sinusoidal) at the input to the receiver.  So  I/Q ADC level (dBFs) = RX input level (dBm) + RX gain (dB) - 10dBm.

However on the datasheet in Figure 5-1 the receiver input in-band P1dB is ~-47dBm at a receiver gain of 48dB.

www.ti.com/.../specifications

Q1. Why is the receiver in-band P1dB 9dB lower than the ADC full-scale receiver input level of -38dBm.  Can you let me know what element in the receiver chain is causing this compression before the ADC has reached full-scale?

Q2.  Can you also confirm that the equation above for calculating the I/Q ADC level (in dBFs) from the RX input power is correct?

I appreciate your help with this.

Yours faithfully,

Jonathan Jones

  • 0
    TI__Guru*** 148284 points
    Hi Jonathan,

    Can you please let us know for what application you are planning to use the AWR1243?

    This will help us better understand you questions and provide better support.

    Thank you
    Cesar
  • 0 in reply to Cesar
    Intellectual 680 points

    Hi Cesar,

    Thank you for your quick reply.

    I can't really share details of the application on a public forum.

    Other that to say we are trying to model the performance of a short range radar based on the AWR1243 and so need to understand the performance of the chip in order to create the model.

    Let me know if you need any more information.

    Best regards

    Jonathan

  • 0 in reply to Jonathan Jones2
    TI__Guru 58035 points
    Hello Jonathan,
    The 1V peak is the absolute max ADC input but it saturates beyond +-0.5V peak value. This corresponds to -44dBm input level with 48db gain. Since is the saturation point , but the P1db point would come slightly earlier. So we see that typically at around -47dBm input level.

    Regards,
    Vivek