HP 8753E - Page 58

48 Chapter 2
Quick Start: Learning How to Make Measurements
Learning to Make Reflection Measurements
Measuring S
11
and S
22
in a Polar Format.
S
11
is a measurement parameter used to measure the reflection coefficient of your test
device input, where S
22
is a measurement parameter used to measure the reflection
coefficient of the your test device output. In both instances, you must terminate all the
unused ports.
1. Press
Format, POLAR.
2. Press
Scale Ref, AUTO SCALE to reposition the trace, as shown in Figure 2-14.
The analyzer shows the results of an S
11
measurement with each point on the polar
trace corresponding to a particular value of both magnitude and phase. The center of
the circle represents a coefficient (Γ) of 0, (that is, a perfect match or no reflected signal).
The outermost circumference of the scale shown in Figure 2-14 represents ρ = 2.00, or
200% reflection. The phase angle is read directly from this display. The 3 o'clock
position corresponds to zero phase angle, (that is, the reflected signal is at the same
phase as the incident signal). Phase differences of 90°, 180°, and −90° correspond to the
12 o'clock, 9 o'clock, and 6 o'clock positions on the polar display, respectively.
3. Press
Marker Fctn, MKR MODE MENU, POLAR MKR MENU.
4. Turn the front panel knob to position the marker at any desired point on the trace, then
read the frequency, linear magnitude and phase in the upper right hand corner of the
display.
■ Choose
LIN MKR if you want the analyzer to show the linear magnitude and the phase
of the marker.
■ Choose
LOG MKR if you want the analyzer to show the logarithmic magnitude and the
phase of the active marker. This is useful as a fast method of obtaining a reading of
the log-magnitude value without changing to log-magnitude format.
■ Choose
Re/Im MKR if you want the analyzer to show the values of the marker as a real
and imaginary pair.
NOTE You can also enter the frequency of interest, from either the optional
attached keyboard or the numeric keypad, and read the magnitude and
phase at that point.