MDO3000 Programmer Manual.pdf - 第80页

Command Groups Spectrogram sl ices are generated by taking each spectrum and ﬂipping it on its edge, so that it is one pixel row tall. Each new acquisition adds another sli ce at the bottom of the spectrogram, and the pr…

Command Groups

attenuation, ﬁ

ltering and down-conversion, depending on the parameters set by

the user (frequency, span, reference level, and so forth.)

For the MDO400

0/B/C series models, the acquisition system uses one of three

frequency bands to acquire RF data depending on where the center frequency and

span are set. The bands are: 50 kHz to 3.75 GHz, 2.75 GHz to 4.5 GHz, and

3.5 GHz to 6.0 GHz.

For the MDO3000 series models, there is one frequency band (up to 3 GHz

depending on the model and installed options).

Specifying the Reference

Level and Resolution

Bandwidt

h (RBW) Settings

For the MDO4000/B/C series models, the reference level is adjustable from

–140 dBm to +30 dBm. For the MDO3000 series models, the reference level

is adjustable from –140 dBm to +20 dBm. For all series, attenuation is set

automatically with the reference level. The RBW setting is adjustable downto

20 Hz. By

default, the RBW tracks span in automatic mode in a 1000:1 ratio;

this ratio is adjustable.

Detection Types

All MDO instruments calculate Fast Fourier Transform calculations (FFTs) with a

1,000 t

o ~2,000,000 point output, depending on the acquisition settings. It then

reduces that FFT output into a 1,000 pixel-wide display (for the MDO4000/B/C)

or 750 pixel-wide display (for the MDO3000). This means that approximately

1 to 2,000 FFT points get compressed into each pixel column. There are four

choices as to how this compression is done: +peak, sample, average, and -peak.

TriggeringUsingRFPower

Level as a Source

You can use the RF power level as a source for triggering with the MDO4000/B/C

models (but not the MDO3000 models). The MDO4000/B/C triggered acquisition

system is fully integrated with both the frequency and time domains. This means

that a single event can trigger all of the analog, digital and RF acquisitions,

gardless of whether that event came from an analog, digital or RF input. The

RF power level has been distilled through special processing and may be used

as a trigger. RF Power may be used as a source for Edge triggering. With an

MDO4TRIG application module installed, the RF Power level can also be used as

a source for pulse width, timeout, runt, logic and sequence triggering. (For more

information, see Triggering on the RF input. (See page 2-76, Trigger Command

Group.)

Spectrogram Display

(MDO4000/B, MDO4000C with option SA3 or SA6, and MDO3000). The

spectrogram is a graph of frequency domain traces over time. It provides an

intuitive display that is useful for monitoring slowly changing RF events,and

for identifying low amplitude signals too subtle for the eye to catch in a regular

spectrum display. The x-axis shows frequency, and the y-axis shows time.

Amplitude is represented by the color of the trace. Cold colors (blue, green)

indicate low amplitude, and hot colors (red, yellow) indicate high amplitude.

MDO4000/B/C, MSO/DPO4000B and MDO3000 Series Oscilloscopes Programmer Manual 2-49

Command Groups

Spectrogram sl

ices are generated by taking each spectrum and ﬂipping it on its

edge, so that it is one pixel row tall. Each new acquisition adds another slice at the

bottom of the spectrogram, and the previous acquisitions (slices) move up one

row; you can then navigate backwards through the history of the spectrogramby

selecting slice numbers to view. (The spectrogram slice trace is displayedas

the RF Normal trace.)

Spectrum Mo

de: Triggered

and Free Run

When only the frequency domain waveforms are displayed (no time domain

waveforms), you can choose whether the MDO4000/B/C should use Triggered

mode or Free Run mode. (MDO3000 only uses Free Run mode.) When Triggered

mode is se

lected, you can control all trigger settings, including Normal and

Auto triggering. When Free Run mode is selected, the oscilloscope generates

RF acquisitions as fast as possible. (To display only the frequency domain

waveforms, turn off all time domain waveforms, including channels 1- 4, digital

channels 0 - 15, buses, time domain math waveforms, time domain reference

waveforms, and any RF vs. Time traces.)

When the oscilloscope displays both time and frequency domain waveforms,

then the instrument’s trigger system is in control of the Triggered mode andthe

RF acq

uisitions.

Using Markers in the

Frequency Domain for

Measurement and Analysis

For frequency domain measurements, up to 11 automatic markers are available

to assist with quickly identifying the frequency and amplitude of peaks in the

spe

ctrum based upon user threshold and excursion settings. If more peaks meet

the criteria than the desired number of markers, then the highest amplitudepeaks

are shown. Two manual markers are also available for measuring non-peak areas

of interest, and to measure Noise Density and Phase Noise. If manual markersare

off, the reference marker is automatically placed on the highest amplitudepeak.

With manual markers on, the reference marker becomes the “A” manual marker.

utomatic peak markers are on by default.

Each automatic marker has a readout associated with it. These can be absolute

r delta readouts. An absolute marker readout shows the actual frequency and

amplitude of the associated marker. A delta marker readout shows the frequency

and amplitude of the automatic markers relative to the Reference Marker.

The Reference Marker’s readout indicates absolute frequency and amplitude,

regardless of the readout type. (It is marked on the display with a red R in a

triangle.) The marker measurement readouts are absolute in dBm or relativetothe

reference marker in dBc (dB below carrier amplitude).

The threshold and excursion settings deﬁne which peaks are marked automatically.

The threshold is a minimum amplitude that a signal must cross to be a valid peak.

If the threshold is lower, more peaks will tend to qualify for markers. If the

threshold is higher, fewer peaks tend to qualify for markers. The excursion is how

far a signal needs to fall in amplitude between marked peaks to be another valid

peak. If the excursion is low, more peaks will tend to qualify for markers. Ifthe

excursion is high, fewer peaks will tend to qualify for markers.

2-50 MDO4000/B/C, MSO/DPO4000B and MDO3000 Series Oscilloscopes Programmer Manual

Command Groups

When the two man

ual markers are turned on, the Reference Marker is no longer

automatically attached to the highest amplitude peak. It can now be moved toany

desired location. This enables easy measurement of any part of the spectrum,

as well as delta measurements to any part of the spectrum. This also lets you

measure non-peak spectral content of interest. The readouts for manual markers

indicate frequency, amplitude and noise (just like automatic marker readouts).

Taking Auto

matic

Measurements in the

Frequency Domain

You can take three automatic measurements in the frequency domain:

1. Channel Power (CP) — The total power within the bandwidth, deﬁned by

the Channel Width.

2. Adjacent Channel Power Ratio (ACPR) — The power in the main channel

and the ratio of channel power to main power, for the upper and lower halves of

each adjacent channel.

3. Occupied Bandwidth (OBW) — The bandwidth that contains the speciﬁed

percentage of power within the analysis bandwidth.

Triggering using RF

Power L evel as a Source;

Searching

The ability to use the RF power level as the source for edge triggering and

searching is provided standard with the MDO4000/B and MDO4000C with

option SA3 or SA6 series models. With the MDO4TRIG (Advanced Trigger)

application module installed, the RF power level can also be used as the source

for p

ulse width, time-out, runt, logic, and sequence triggering. (See page 2-76,

Trigger Command Group.) A number of search commands are also available.

(See page 2-61, Search Command Group.)

Transfe rring and Saving

RF Trace Information

u can perform waveform transfer commands and queries using RF traces. (See

page 2-95, Waveform Transfer Command Group.)

traces can be saved to an .ISF or .CSV ﬁle for subsequent recall to any of the

4 internal reference memory locations. The oscilloscope can also save, butnot

recall, RF acquisitions as .TIQ ﬁles. You can import .TIQ ﬁles into Tektronix

SignalVu-PC software (PC based), SignalVu software (oscilloscope based),

RSAVu software (PC based) or into a Tektronix real-time spectrum analyzer for

pulse analysis and demodulation analysis. (See page 2-58, Save and Recall

Command Group.)

NOTE. The RF input replaces the Aux Input connector on the front panel,

therefore aux-in commands and arguments are not supported on the MDO4000/B,

MDO4000C with option SA3 or SA6, and MDO3000 models with 4-channels.

MDO4000/B/C, MSO/DPO4000B and MDO3000 Series Oscilloscopes Programmer Manual 2-51