MegiQ VNA04 Series, Руководство пользователя

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VNA0440 – VNA0440e
VNA0460 – VNA0460e
user manual V3.1
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www.megiq.com
10. Graphs
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Impedance graphs
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Gain graphs
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Graph control
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Context menu
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Arranging graphs
There are many different graph types but they are all derived from the S-parameters of the
measurement. These S-parameters represent either an impedance or a Gain. There are
different graph types depending on the trace type: Impedance or Gain.
Impedance graphs
The measured impedance can be represented in different graph types, but they are all
derived from the measured S-parameter (S11 or S22).
Return Loss
The Return Loss graph is scalar, thus without phase information, and gives the ratio
between the transmitted signal and the signal that is ‘reflected’ back because of a
mismatch between the source port and the DUT impedance. This ratio is displayed in dB
and has no phase information. The lower the value the better the impedance match. A
perfect match yields a return loss of minus infinite and a perfect mismatch gives a Return
Loss of 0dB. For antennas often a limit of better than -10dB return loss is used.
Forward Loss
The forward loss (or transmission loss) is the relative amount of power that is lost because
of the mismatch between source port and DUT impedance. With a perfect match the
Forward loss will be 0dB.
SWR
The SWR is similar to Return Loss but it represents the ratio of Standing Waves
compared to the Forward Waves . A value of 1 represents a perfect match and a perfect
mismatch (open or short circuit) gives an infinite value.
Impedance
The impedance graph is a straight representation of the measured impedance magnitude
and its phase.