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  1. #1
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    The relation among power, bandwidth and harmonics

    Hi, supposed PA amplifies one CW, in these two conditions, may I ask which one has the highest 2nd harmonics?

    A. center frequency =2.4GHz, Bandwidth=100MHz, Power spectrum density(PSD)=2W/MHz
    B. center frequency =2.4GHz, Bandwidth=200MHz, Power spectrum density(PSD)=1W/MHz

    I think A should the highest 2nd harmonics. My explaining is although BW of B is wider, it cannot affect 2nd harmonics since f2nd=4.8GHz which is too far away.
    2W/MHz>1W/MHz, so the output swing of A is bigger that generates more harmonics?
    Is that correct?

    Based on the above, supposed I have two CW with the same PSD 2W/MHz, one is 100MHz BW, the other is 200MHz BW (supposed all other parameters are the same). Can I say they have the same harmonics level?

    Thanks
    Last edited by diego.fan; 4th July 2019 at 07:27.

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  2. #2
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    Re: The relation among power, bandwidth and harmonics

    Kindly clarify what you mean by 'CW' ? Also what modulation is this which is 100-200Mhz wide?

    Lastly, why do you specifically expect 2nd harmonics?



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  3. #3
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    Re: The relation among power, bandwidth and harmonics

    There is no relationship between Bandwidth and Harmonics.
    Harmonics are produced by Non-linear Transfer Function of the Active Devices and they are mathematically related to this function.



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  4. #4
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    Re: The relation among power, bandwidth and harmonics

    No you cannot say that more BW automatically results in more or less 2nd harmonics.
    As BigBoss already pointed out, your 2nd harmonic content depends on your transistors.
    But, you also need to check the behavior of your matching network near the 2nd harmonic. Although your matching circuits are linear elements, but their behavior in frequency domain is anything but linear.



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