Ceyear 4051 Series, User Manual

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4. Operating Instruction
4.1 Function operation guide
82
4.1.3.1 Trace detector and trace operation
The trace refers to a set of sampling points of data, each of which (x, y) has one x value generally representing
frequency or time and y value generally representing amplitude. Each data point is also called trace point. In
any trace, the first data point is called trace 0, while the last one is called trace (sweep point -1). The trace
points are also called sweep points. For the spectrum trace, one trace point is generally corresponding to one
frequency interval, also called Bucket sometimes, and the measured value Y represents a measured data
corresponding to one Bucket. The menu corresponding to the
【
Trace
】
key on the front panel can help you
configure the measured trace and complete the trace operation.
Each trace can be considered to be one analysis implemented to the measured data. Each trace window of the
4051 Series Signal/Spectrum Analyzer can display 6 traces. The trace configurations determine how the
measured data analyzes and displays. The section mainly describes how to configure the trace and execute
trace operation.
1) Concept of trace detector
When the sweep type is sweep under the spectrum analysis mode, the Series Signal Analyzer control the LO
by digital mode to carry out step sweep in smallest frequency. During the entire sweep period, the sampling
points captured by ADC in the digital IF circuit are much larger than the sweep points that used by the Series
Signal Analyzer for display. When the sweep type is FFT, the Series Signal Analyzer tunes the LO to fixed
frequency point. During the entire measurement period, after the FFT is carried out, the sampling points
captured by ADC in the digital IF circuit may be larger than the sweep points that used by the Series Signal
Analyzer for display.
E.g., we assume that the sampling frequency of ADC is 100 msa/s, sweep points are 1000, sweep time is 100
ms and the span is 1 GHz. For each sweep, the Series Signal Analyzer captures 100*10
5
sampling points,
which are needed to be turned into 1001 trace data. Equivalently, every 100,000 sampling data is
corresponding to the trace data at one point, while each trace datum represents the signals appeared with
frequency range of 1 MHz. If the sweep points are added, the span corresponding to each trace datum is
narrower, the measured results are more stable and the frequency readout accuracy is higher.
From the above analysis, it can be seen that the trace display needs to turn the more sampling data points into
the less sweep trace points, which is what the trace detector needs to do.
There are many types for the trace detector modes. The 4051 Series Signal/Spectrum Analyzer has 7 trace
detector modes:
 Normal detection
Take the maximum value and minimum value from the sampling data assigned to each trace point and display
them at the same time.
 Positive peak detection
Take and display the maximum value from the sampling data assigned to each trace point.
 Negative peak detection
Take and display the minimum value from the sampling data assigned to each trace point.
 Sampling Value Detector
Take and display the last value from the sampling data assigned to each trace point.
 Power Average Detector
Also called root mean square (RMS) detector. Calculate the root mean square of all sampling data assigned to
each trace point; the 4051Series Signal Analyzer envelopes the detector for the RF input signal and obtains
linear voltage. After square these voltage values, take sum and divide the count of sampling data points
corresponding to each trace point. Finally, take square root. When the scale is logarithm, take 20 times of
logarithm transformation for these RMS values (with 10 as base) and obtain the trace data. When the scale
type is linear, those RMS values are trace data.