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Type: Posts; User: cariban

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    Closed: Re: GPS matching network confusion

    The 9.2nH in series before LNA is to obtain less reflection (with respect to either 50 or 75 OHM, but 50 OHM is more common for LNA). Then it is easier for the user to design the transmission line to...
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    Closed: Re: Understanding of noise figure

    Noise figure stands the ratio between the total noise above thermal noise. After LNA, both the signal and the noise level at the output has been significantly boosted, so the extra noise introduced...
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    Closed: Re: Question about PC3.5mm and SMA connectors

    3.5mm and SMA are mechanically compatible. The difference lies that 3.5mm uses air as dielectric material (or no dielectric material), so the operating frequency is higher than SMA. SMA has PVC like...
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    Closed: Re: microwave power combiner/divider

    The definition of s-parameter is based on excitation at each port. Of course you can excite two ports and the s-parameter based on linear model is still correct, but you have to consider how they are...
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    Closed: Re: microwave power combiner/divider

    Agree with this. The unused port should be terminated.
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    Closed: Re: microwave power combiner/divider

    Depends on the correlation coefficient of your two inputs, you may get S31/S32 higher than 0dB. For example, if the combiner is ideal and you have exactly the same signal x(t) at port 1 and port 2,...
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    Closed: Re: Cable simulator with lumped components

    Thanks a lot to both FvM and volker@muehlhaus. You two are right, it is difficult to make a simulator matching to real cable with amplitude, phase and returnloss in the same time.
    I have manage to...
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    Closed: Re: Cable simulator with lumped components

    Thanks for the help. I need to simulate Belden 1694A up to 600 meters. The error should be within +/-1 dB up to 6GHz. Do you have any recommended document about this topic?
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    Closed: Cable simulator with lumped components

    I need to design a lumped component based cable simulator. This is to save cost for buying long cable. Does anybody have idea how to realize it?
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    Closed: 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...
  11. Closed: Re: Why an input inductor required in all GPS LNA?

    It is definitely possible to put the small inductor inside the LNA. There are two reasons why they don't do it:
    1. Internal inductor will increase the chip area, complexity and then the cost;

    2....
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    Closed: Re: Broken RF ground plane

    I would think your idea is correct. A small gap in the bottom plane should not change the impedance significantly since there is still a solid plane in the top layer. 1mm gap should be wide enough to...
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    Closed: Re: Different Input/Output matching

    As FvM said, use circulator to absorb the reflection from antenna is common way to separate TX/RX channel. It has been used in radar system for many many years.
    if you just worry about the output...
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    Closed: Re: Different Input/Output matching

    In theory the black box does exist. But what is the point to design such a mis-matching network?

    153516

    If you would like the network to be lossless and composed by LC, it is not possible....
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    Closed: Re: Different Input/Output matching

    To be honest, I don't understand your problem and what is your purpose. Maybe you could make a simple diagram to show what you want to do and what is the problem.
  16. Closed: Re: Suggestions on Broadband Matching in Power amplifier

    It is true that the filter bank will increase the complexity significantly. Try your luck to design a wideband impedance matching network first.
  17. Closed: Re: Suggestions on Broadband Matching in Power amplifier

    Broadband impedance matching is quite different from narrow-band matching. There is a theoretic bound for returnloss if the matching network must be lossless. You can not obtain better result than...
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    Closed: Re: Unitary property of scattering matrix

    This could be explained by law of conservation of energy. The injected power must be equal to the reflected power + the transmitted power for a lossless network.
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    Closed: Re: RF Amplifier Performance Characteristic

    How high is the harmonics? It is hard to believe that a little harmonics in the input signal would impact the gain by 5 dB. Maybe you forgot to consider the extra loss introduced by the LP filter?
  20. Closed: Re: Why do company sites have inductors and capacitors in an s2p file format?

    Inductors and capacitors are two-port components, so it is not strange manufacturers supply s2p files. If you need only one port, you can derive the s1p file by given terminate conditions of another...
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    Closed: Re: power amplifier design input impedance

    BigBoss is right! I also got confused. Actually you just need to do reverse impedance matching, let the source/load be the same as the datasheet requirement. If the K is not good enough, just add a...
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    Closed: Re: power amplifier design input impedance

    Yes, since your load is 50 Ohm ideal, maximum output power = minimum returnloss.

    It sees that S22 is still too high.
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    Closed: Re: power amplifier design input impedance

    Just remind another thing. The S-parameter is obtained by assuming ideal load/source terminations. For your case, you need to optimize both input and output impedance. When you put an impedance...
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    Closed: Re: power amplifier design input impedance

    Could you plot the S12 as well? The isolation is also critical for stability. I also notice that your S11 and S22 are still too high. Try to make perfect match at the central frequency. If the K is...
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    Closed: Re: power amplifier design input impedance

    The problem may come from the s-parameter of your amplifier. Have you double checked that the amplifier s-parameter matches with the datasheet? As you can see, different IQD affect the input/output...
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