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    Loadpull for Narrowband and Broadband

    Hi, I have been looking for a proper answer this question but I didn't find any proper answer. For narrowband applications, we perform loadpull at center frequency and matching accordingly But how can we apply the loadpull and suitable matching for a band of frequencies i.e., broadband. Should we do consider the mid band frequency and perform loadpull for this freqeuncy? or Highest frequency in the band as it has more parasitic effects? Thanks in advance.

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    Re: Loadpull for Narrowband and Broadband

    Performa load pull over intended frequency range, design appropriate wideband matching if feasible.

    Or design matching for center frequency, check with wide band load pull and matching in place. Correct if necessary.



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    Re: Loadpull for Narrowband and Broadband

    Quote Originally Posted by FvM View Post
    Performa load pull over the intended frequency range, design appropriate wideband matching if feasible.
    I should take load-pull at various frequencies in the band and design a matching network (MN) for one of those Zopts. Then, tune the matching network component parameters such that it may be close to Zopt of all frequencies but may not be a perfect match . Is this how it is done, or is there any fancy way of doing it that considers Zopt at all the frequencies while designing MN itself?



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    Re: Loadpull for Narrowband and Broadband

    A simple LC matching network, e.g. CLC pi network, achieves matching only for a single frequency, even for frequency independent impedances. Matching over a wider frequency range requires different components like transformers or a more complex LC network.

    Under circumstances, you are able to design a wide band matching network also for frequency dependent impedances. It depends on the impedance curves, frequency range, available components and your design skills.


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    Re: Loadpull for Narrowband and Broadband

    Depends on the Zopt for ( Max. Delivered Power OR max. Efficiency OR max. Gain ).Simultaneous matching is almost impossible for 3 target but IF Zopt ( for any target ) values are closer over a wide-band, midpoint Zopt can be used but general speaking, Zopt values are not close to each other so simple matching or complex matching over a wide-band is not easy.You gain in a specification while you're loosing another..There is always a compromise.



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    Re: Loadpull for Narrowband and Broadband

    Wideband impedance matching is much more complicated than narrow band. In general there exists a theoretical limit for wideband impedance matching problem, i.e. you can not obtain perfect matching over the whole band. As a compromise, you can set a target in the whole band, for example, 10 dB returnloss. Then use a tool to search for the impedance matching network which gives you returnloss within the specification over the whole band.

    Just to answer your question more directly. In general it is not enough to match at only one or few point(s), you must consider the whole band. In some cases it may be very difficult to obtain good matching over the whole band, you may have to divide the whole band into several sub-band to make the matching easier.
    Last edited by cariban; 27th August 2019 at 08:22.


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