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    Injection XFMR source level

    Hello everyone,

    What is the source signal level the B-WIT 100 injection XFMR gain response was characterized with ?

    I think it is 0.27V of amplitude (i.e. ~0.2 V RMS) if source is 50 ohms, but how do we know ?

    Thank you for your time !

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    Re: Injection XFMR source level

    The datasheet says -10 dBm and 10 ohm load, which makes no sense for a 1:1 transformer with 50 ohm source.

    I think it's easier to measure yourself than to guess about an obviously confused specification. Besides possible core saturation with high input level at the lower frequency corner, why do you expect level dependent transfer function?



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    Re: Injection XFMR source level

    The datasheet says -10 dBm and 10 ohm load, which makes no sense for a 1:1 transformer with 50 ohm source.
    Why does not ? Why would you want load and source matching for no more than 10 MHz ?

    I think it's easier to measure yourself than to guess about an obviously confused specification.
    I do not want to buy a 500$ XFMR, so I wound one myself. I want to compare mine with their, so I want to characterize at the same level. Others use 0.1V amplitude, which increases the lower frequency range.

    Besides possible core saturation with high input level at the lower frequency corner, why do you expect level dependent transfer function?
    I do not. I do not want to use a smaller voltage than the one they used, which would increase my frequency range and lead to wrong comparison.



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    Re: Injection XFMR source level

    Why does not ? Why would you want load and source matching for no more than 10 MHz ?
    How do you read the datasheet specification? -10 dBm is 71 mV into 50 ohms. But the input level drops if you load the transformer with 10 ohms. I don't talk about impedance matching, but a dBm level is tied to specified source impedance.

    Just demand an unambiguous specification.

    I see that the full product manual is (almost) clarifying things. https://www.omicron-lab.com/fileadmi...NU11890504.pdf

    They are doing the measurements with a VNA, -10 dBm source level. This corresponds to 24 mV with 10 ohms load. 0 dB gain has been normalized for 10 ohm load.

    Their saturation spec doesn't seem to refer to commonly understood technical terms, may be someone has an idea.
    Saturation defined as 20 dBc at the 10 Ω injection resistor, signal source with 50 Ω source impedance
    - - - Updated - - -

    Specified 3.5e-3 Vs saturation flux corresponds to 15 mVrms at 1 Hz respectively 150 mV at 10 Hz according to my calculation.


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    Re: Injection XFMR source level

    They are doing the measurements with a VNA, -10 dBm source level. This corresponds to 24 mV with 10 ohms load. 0 dB gain has been normalized for 10 ohm load.
    Sure. 24 mVrms for 10 ohms load.
    The datasheet says -10 dBm and 10 ohm load, which makes no sense for a 1:1 transformer with 50 ohm source.
    As you say, once you know they use a 50 ohm VNA, it is easily calculable the source signal level. I do not get your "no sense statement" or "ambiguous specification". They specified the dBm source level significance making it unambigous at page 34 and 104 of their VNA's manual.
    https://www.omicron-lab.com/fileadmi...NU10060503.pdf
    Last edited by CataM; 27th May 2019 at 02:00.



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    Re: Injection XFMR source level

    The "ambiguous" statement was related to the datasheet and your post #1. The datasheet does e.g. not specify a source impedance.

    As you have found out in the meantime, the spec becomes clear when referring to other manufacturer documents. I still don't understand the "20 dBc" saturation spec. I would expect something like P1dB (1 dB compression level) or IP3. In usual RF terms, dBc is a level relative to carrier (or fundamental wave). It can be used to measure distortion, e.g. 3rd harmonic has a level of -20 dBc. But you need to name the measured component explicitly and won't expect a positive dBc number.

    Anyway, good that you could apparently answer the questions in post #1.


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    Re: Injection XFMR source level

    Thanks FvM for your help.

    Here are the results.

    XFMR designed as follows:
    Core material: VAC T60006-L2050-W516
    Windings: bifilar wound 50 turns, AWG 19


    Measurements using a sweep from 10Hz to 100 MHz with -19dBm into 50 ohms

    • Lmag=120 mH@1kHz
    • 3dB frequency range: ?? low freq up to 3.388 441 561 MHz (the VNA did not had enough range for the lower frequency corner.. did not bother to measure it with function gen since it is lower than 10 Hz)
    • +/- 5 frequency range: ?? low freq up to 327340.695 Hz
    • Insertion Loss = 0.03 dB
    • Usable frequency range: up to 7.328 245 MHz


    3dB point:
    Click image for larger version. 

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