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TRF371109: Noise Figure

Viktor Vojta
Intellectual 315 points
Part Number: TRF371109

Dear colleagues,

I performed evaluation measurement of IQ-demodulator TRF371109. Frequency band of interest is 300MHz. I have measured NF for one path (I or Q), with highest gain setting and I got 17dB, which is higher than the datasheet shows. There is a number cca. NF = 9dB. Measured gain fits datasheet value. I would like ask, which measurement method has been used for NF evaluation, e.g. IQ - demodulator was connected as a DSB mixer or SSB mixer? Or anything else? 

  • 0
    TI__Guru 70264 points

    Hi Viktor,

    Noise figure is measured with the following methods:

    -Kang

  • 0 in reply to Kang Hsia
    Intellectual 315 points

    Thank you for the answer,  however I was referring to I and Q outputs (not RF or LO port). Was it measured (or calculated) assuming that both I and Q outputs are connected and demodulator works as a SSB mixer? Or was it measured as a simple mixer? Or alternatively if the NF is with or without image noise contribution. 

  • +1 in reply to Viktor Vojta
    TI__Mastermind 18095 points

    Viktor:

    That is a little strange as the gain increases (and hence NF improves) at lower frequencies.  The measurements in the datasheet bypass/compensate for the balun to facilitate a broader measurement frequency band.  The measurement is taken with respect to a single BB output.  The measurement technique used the Y-factor method using a noise diode.

    Your measurement is around 8 dB too high.  Here are some things to consider in making an accurate measurement.

    • Use the output transformers to interface to 50 ohm equipment; the BB outputs can not drive 50 ohms directly.
    • Verify LO drive level is high, 5 - 10 dBm.  Filter the LO source to verify its noise is not infecting the measurement.
    • There is actually a lot of gain; verify that the signal is not compressing the measurement instruments.
    • If using a noise diode, ENR should be 5 - 10 dB.  Anything higher will compress the device.
    • Verify the noise / attenuation of the measurement instrument is not too high and impacting the measurement
    • Verify that the voltage supply is not excessively noisy.
    • If a balun is used on the RF input, verify that the loss of the balun is compensated for.  If no balun is used, compensate for the SE vs. Differential input.

    --RJH

  • 0 in reply to RJ Hopper
    Intellectual 315 points

    OK, thank you a lot, I will doublecheck all mentioned points and remeasure it.