R&S ESU Series Operating Manual page 169

R&S ESU
The peak detectors compare the current level value with the maximum or minimum
level from the previously sampled data. When the number of samples defined by the
instrument setting is reached, the samples are combined in the displayed pixels.
Each of the 625 pixels of the display thus represents 1/625 of the sweep range and
contains all single measurements (frequency samples) in this subrange in com-
pressed form. For each trace display mode an optimized detector is selected auto-
matically. Since peak detectors and sample detector are connected in parallel, a
single sweep is sufficient for collecting all detector values for 3 traces.
Peak detectors (MAX PEAK and MIN PEAK)
Peak detectors are implemented by digital comparators. They determine the largest
of all positive (max peak) or the smallest of all negative (min peak) peak values of
the levels measured at the individual frequencies which are displayed in one of the
625 pixels. This procedure is repeated for each pixel so that for wide frequency
spans and despite the limited resolution of the display a large number of measure-
ments can be taken into consideration for the display of the spectrum.
Auto peak detector
The AUTOPEAK detector combines the two peak detectors. The max peak detector
and the min peak detector simultaneously determine the maximum and the mini-
mum level within a displayed test point and display it as a single measured value.
The maximum and minimum levels within a frequency point are connected by a ver-
tical line.
Sample detector
The SAMPLE detector routes through the sampled data without any further evalua-
tion and either displays them directly or, for reasons of speed in case of short sweep
times, first writes them into a memory and processes them subsequently.
There is no data reduction, i.e. no summing up of measured values of neighboring
frequencies or time samples. If during a frequency sweep more measured values
are obtained than can be displayed, measured values will be lost. This means that
discrete signals might be lost.
The sample detector therefore can only be recommended for a span-to-resolution
bandwidth ratio of up to approx. 250 in order to ensure that no signal will be sup-
pressed (example: span 1 MHz, -> min. bandwidth 5 kHz).
RMS detector
The RMS detector forms the rms value of the measured values within a pixel.
To this effect, R&S ESU uses the linear voltage after envelope detection. The sam-
pled linear values are squared, summed and the sum is divided by the number of
samples (= root mean square). For logarithmic display the logarithm is formed from
the square sum. For linear display the root mean square value is displayed. Each
pixel thus corresponds to the power of the measured values summed up in the pixel.
The RMS detector supplies the power of the signal irrespective of the waveform
(CW carrier, modulated carrier, white noise or impulsive signal). Correction factors
as needed for other detectors for measuring the power of the different signal classes
are not required.
4.138
Instrument Functions
Analyzer Mode
Operating Manual 1302.6163.12 - 03