HP 8530A, Руководство по эксплуатации и программированию, Страница: 217 / 439

Response Functions
W aveguide Delay . Selecting
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WAVEGUIDE DELAY applies a non-linear phase shift which follows
the standard dispersive phase equation for rectangular waveguide . When
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WAVEGUIDE DELAY
is pressed the active function becomes the W A VEGUIDE CUTOFF frequency , which is used in
the phase equation. Choosing a Start frequency less than the Cuto Frequency results in phase
errors .
T able Delay
The
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TABLE DELAY selection allows an array of real,imaginary data pairs input by the user
via the HP-IB to be applied to the data for the selected channel. Selecting
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TABLE DELAY
disables Electrical Delay , Magnitude Slope , and Magnitude Oset. This array must be loaded
using HP-IB (see description in the Programming section of this volume), then the table may be
stored and loaded using the disc drive .
Selecting V elocity F actor
The relative velocity factor of propagation can be selected. Press:
4 CAL 5
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MORE
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VELOCITY FACTOR
The active function is now Relative V elocity F actor . After F actory Preset, this value is 1.0
which is the equivalent of the speed of light in free space (2.997925 x10
8
meters per second).
The range of the relative velocity factor is 0.001 to 500, with values less than 1 indicating that
the propagation velocity is less than the speed of light in free space .
F or example , the relative velocity is 1 divided by the square root of the dielectric constant for
the media, e
r
. F or waveguide media in standard air , the dielectric constant is about 1.00064,
giving a relative velocity factor of about 0.999680.
Changing the velocity factor changes only the supplementary distance readout.
A uto Delay
A major use of electrical delay is to:
Provide the line stretcher function in deviation from linear phase measurements .
T o balance the reference and test signal path lengths to nd the electrical length of the test
device .
The
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AUTO DELAY key automatically selects the appropriate value of electrical delay to balance
the reference and test signal path lengths and thus result in a reasonable balanced (at) phase
trace at the marker position. When you press
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AUTO DELAY , the phase values at the marker
position and the two adjacent points are sampled and electrical delay is added in order to make
the phase constant. Y ou may then make ne adjustments of Electrical Delay to achieve the
desired trace .
9-8 Response Functions