Ceyear 4051 Series, User Manual

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Appendix
Appendix A Terminology
714
sweep time. Most signal/spectrum analyzers use LC filter, crystal filter, active power filter and digital filter to
enable different resolution bandwidths.
Amplitude accuracy:
A parameter, associated with the result of a measurement, that characterizes the dispersion of the values that
could reasonably be attributed to the measurement. Influence factors of amplitude measurement accuracy
include frequency response, display fidelity, input attenuator switching error, IF gain, scale factor and
resolution bandwidth.
Negative peak value detection
It is a display detection method for signal energy. Each displayed point corresponds to multiple detection
sampling data points of video signals in any part of the frequency span or the time interval indicated by such
point. The method to extract the minimum value among such data points is the negative peak value detection.
Track
Traces comprise of a succession of data points containing frequency (time) and amplitude information. Such
succession of data points is usually considered as an a set. Trace 1, 2 and 3 are commonly used in the
signal/spectrum analyzer.
Intermodulation
When two or more signals are loaded at the input interfaces of active devices (such as mixer or amplifier) at
the same time, multiple sum frequency or difference frequency of signal themselves will produce
intermodulation products in addition to signal harmonics due to nonlinearity of such active devices. For the
signal/spectrum analyzer, such intermodulation products are interference signal and their level should be as
low as possible. The relation between the intermodulation product level and the input signal level: if the
amplitude of two sine input signals changes by ∆dB, relevant intermodulation product level will change by
n∙∆dB, in which n refers to the order of the intermodulation product, which means the sum of the term of each
frequency. For example, if the frequency is 2∙f
1
+1∙f
2
, the order will be 2 + 1 = 3. The point of intersection
where the signal amplitude is equal to the intermodualtion product amplitude is usually called the intercept
point. Actually such point does not exist because when the input signal increases to a certain degree, there will
be compression imposed on the output of active devices. The intercept point can be defined with the input or
output level. Therefore, the nominal intercept point is divided into input and output intercept point and the
default intercept point is the input intercept point. The intercept point is usually expressed with dBm. The
greater the value of the intercept point, the better the linearity of the signal/spectrum analyzer, which is the
precondition of obtaining larger dynamic range. In most cases, two-order and three-order products among
such intermodulation products have great impact on measurements. The two-order intercept point is often
defined as IP2 or SOI (second order intercept) and the three-order intercept point defined as IP3 or TOI (third
order intercept). The value of the front input attenuator of the signal/spectrum analyzer (usually 0 dB) should
be designated when calibrating the intercept point since the intercept point value will increase along with the
increase in the decrement of the attenuator.
Linearity of the active devices changes with the increase in the current and the power. The larger the current
provided by the amplifier, or the larger the LO power of the mixer, the better the linearity. Therefore, low
power consumption of the signal/spectrum analyzer often indicates poor linearity. However, what should be
noted is that this is contradictory to the noise requirement. The input attenuator of the signal/spectrum
analyzer can control intermodulation products and has high IP
3
under high noise factor. Therefore, IP
3
and
the noise factor should be analyzed and compared in the equivalent operation mode. IP3 is an index for
measuring the linearity of the signal/spectrum analyzer and reflects the size of intermodulation distortion
when the signal/spectrum analyzer is affected by strong signal interference.
Activity function area
It is the area on the screen for the signal/spectrum analyzer to display active functions and their status. Active
functions are those triggered by the last-pressed key or the last remote control command by the
signal/spectrum analyzer.