Ceyear 4051 Series, Руководство пользователя

Страница: 726 / 751

Appendix
Appendix A Terminology
712
Measuring Unit
Measurement units commonly used in the signal/spectrum analyzer are as shown in Schedule 1:
Schedule A.1 Measuring Units
Measured parameters Unit Name Abbr.
Frequency Hz Hz
Power Level dBm dBm
Power ratio Decibel dB
Voltage Volt (V) V
Time Second s
Impedance (resistance) Ohm (Ω)
Menu
Press hard keys or soft keys on the front panel to trigger relevant functions according to the functional
information of the signal/spectrum analyzer prompted on the right of the display area on the screen.
Reference level
The calibrated vertical scale position on the screen of the signal/spectrum analyzer is used as the reference for
amplitude measurement and the top scale line is usually selected for the reference level.
Measuring range
The power ratio (dB) of the maximum signal (usually the maximum safety input level) and the minimum
signal (display average noise level) measured at the input interface of the signal/spectrum analyzer. Such ratio
is usually far larger the dynamic range to be realized in single measurement.
Marker Delta
One marker method, in which one is the fixed reference marker and the other is the active marker that can be
placed at any position of the displayed trace. The displayed data can be the relative amplitude difference and
the frequency difference (or time difference) between the active marker and the fixed reference marker.
Impact bandwidth
If the actual area formed by voltage response curve of the filter in the signal/spectrum analyzer is made
equivalent to the voltage response curve of an ideal rectangular filter with the same area and the height of such
two curves are made equal, then the width of such rectangular filter is called equivalent impact bandwidth. It
is different from the signal bandwidth or the noise bandwidth. In signal/spectrum analyzer, the impact width is
about 1.5 times of 3 dB bandwidth.
Bandwidth selectivity
Otherwise known as rectangle coefficient, the bandwidth selectivity is an index for assessing the capacity of
the signal/spectrum analyzer to distinguish signals of unequal amplitude. It is usually defined as the ratio of
the 60 dB bandwidth and the 3 dB bandwidth of the filter and it indicates steepness of the filter edge.
Dynamic range
The maximum power ratio of two or more signals at the input interface of the signal/spectrum analyzer
measured with a given accuracy (unit: dB). It indicates the capability to measure the amplitude difference of
two or more signals. The dynamic range is divided into multi-signal dynamic range, single-signal dynamic
range, instantaneous dynamic range and safety dynamic range. It is different from the concept of display range
or measurement range. Influence factors of the dynamic range include display average noise level, internal
distortion, noise sideband, input attenuator, logarithmic amplifier, detector and AD converter.
The best dynamic range for two-order and three-order undistorted measurement can be calculated according to
the following formula.