E7000L SitePROFILER
Handheld Cable/Antenna Analyzer
49
Chapter 6 — VSWR Measurement Testing
Introduction
This chapter provides an overview of performing
Voltage Standing Wave Ratio
(VSWR) measurements with the
E7000L SitePROFILER Cable Analyzer. Like Return Loss, VSWR is used to characterize the cable and antenna
system in order to ensure that the cell site is performing in accordance with established standards.
In telecommunications, the Standing Wave Ratio (SWR) is the ratio of a partial standing wave’s maximum
amplitude to its minimum amplitude in an electrical transmission line. The SWR is usually defined as a
Voltage ratio called the VSWR. For example, the VSWR value 1.2:1 denotes the maximum standing wave
amplitude that is 1.2 times greater than the minimum standing wave value.
VSWR displays the match of the system linearly, rather than logarithmically. VSWR measures the ratio of
voltage peaks and valleys. If the match is not perfect, the peaks and valleys of the returned signal will not
align perfectly with the transmitted signal. The greater this number, the worse the match. A perfect or ideal
match in VSWR terms would be 1:1; however, a more realistic match for a cable & antenna system would
be something like 1.43 (15 dB). Antenna manufacturers typically specify the match in VSWR. The scale of a
VSWR is usually defaulted to setup between 1 and 65.
Reflection measurements are generally performed with the antenna connected to the cable feedline, or
by replacing the antenna with a Load at the end of the RF cable.
To begin a VSWR measurement, press the
Menu
button to open the measurement mode desktop, then tap
the
Cable & Antenna
mode icon. In the
Measurement
main menu, select VSWR.
Which reflection measurement should I use?
Your specification (test procedure) will ordinarily direct you to make either a Return Loss or VSWR
measurement. Typically,
system sweeps
are performed in Return Loss mode, while
component sweeps
are
performed in VSWR mode.
For your convenience, the E7000L SitePROFILER can perform Return Loss and VSWR sweeps simultaneously
while in
Dual Display
mode.
NOTE: The larger of the values of the Return Loss measurement, the better the impedance match. Thus a
Return Loss measurement of 42dB represents a much better impedance match than one of 25dB.
Conversely, in VSWR, better impedance matches are indicated by smaller values.
