Specifications

Ideal Z
0
terminations must consist of two parts, a
perfect connector and an infinite-length perfect
transmission line that absorbs all of the RF energy
that enters it (no reflections).
Infinite length transmission lines are unwieldy at
best, so you must use less-than-ideal terminations.
For calibration purposes there are two common
types: broadband loads and sliding terminations.
Broadband loads are widely used. An example is the
Anritsu 28 Series Termination. These terminations
are easy to use as calibration tools, and they are
adequate for most applications.
Sliding Loads are the traditional Vector Network
Measurement System Z
0
calibration reference. They
provide the best performance when the application
requires high-precision return loss measurements.
Sliding loads consist of a connector, a long section of
precision transmission line, and a microwave load
that is movable within the transmission line. One
thing to remember with sliding loads is that they
have a low-frequency limit and must be used with a
fixed load below this cutoff frequency for full
frequency coverage. Anritsu sliding loads cut off at
2 GHz. (V-connector sliding loads cut off at 4 GHz).
Pin depth—the relationship between the interface
positions of the outer and center conductors—is the
most critical parameter under your control in a slid
-
ing load. An example of its criticality is that an in
-
correct pin depth of 0.001 inch can cause a reflection
return loss of 44 dB. And, since we are trying to cali
-
brate to accurately measure a 40 dB return loss, cor
-
rect pin depth makes a big difference!
Cables in the measurement system are another
cause for concern. The main criteria for a cable are
stability and repeatability. Anritsu offers two types
of cables that meet these criteria: semi-rigid and
flexible. Our semi-rigid cables provide maximum
stability with limited flexibility of movement. Our
flexible cables allow more freedom of movement and
provide good phase stability.
MEASUREMENT CALIBRATION MEASUREMENT
DISCUSSION CALIBRATION
7-10 MS462XX OM
IDEAL TERMINATIONS
l
Reflectionless
l
Perfect Connector
l
Infinite-Length, Dimensionally Ex
-
act, Reflectionless Transmission
Line
PRACTICAL Z
o
TERMINATIONS
l
Broadband Load
l
Sliding Termination
BROADBAND LOAD
l Easy to Use
l Inexpensive
l Adequate for Most Applications
SLIDING LOAD
l
Connector
l
Long Transmission Line
l
Movable Microwave Load