TEKTRONIX 3 Series Mixed Domain Oscilloscope MDO32 and MDO34

Multi channel testing: After testing each channel (such as D0), set its Display to Off and activate the next channel (such as D1) to avoid interference between channels.

Question 3: How to test the display average noise level (DANL) in the spectrum analyzer function of the 3 series MDO? What are the DANL qualification standards for different frequency ranges?

Answer:

1、 DANL testing steps (no input signal, only 50 Ω terminal required)

Equipment connection: oscilloscope RF input connected to 50 Ω feedthrough terminal, no external signal input;

Oscilloscope settings:

Reset according to Default Setup;

Activate RF channel (RF button → On);

Set Trace mode: RF menu → Traces → Average=On, Normal=Off;

Detection mode: Detection Method → Manual → Average;

Reference level: Vertical Settings → Ref Level=-15dBm;

Frequency range setting and measurement:

9kHz-50kHz: Orizontal → Start=9kHz, Stop=50kHz, move the Marker (Multipurpose knob a) to the highest noise point, and record the DANL value;

50kHz-5MHz：Start=50kHz，Stop=5MHz，Center=2.525MHz， Record the highest noise level;

5MHz-2GHz (3-SA3 option): Start=5MHz, Stop=2GHz, Center=1GHz, Span=10MHz, record the highest noise value;

2GHz-3GHz (3-SA3 option): Start=2GHz, Stop=3GHz, Center=2.5GHz, Span=10MHz, record the highest noise value;

Data processing: Ignore stray signals above the noise level (refer to the "residual response" specification) and only record the noise baseline value.

2、 DANL qualification standards for different frequency ranges

Frequency range standard (without 3-SA3) 3-SA3 option typical values (better than standard)

9kHz-50kHz ≤-109dBm/Hz ≤-109dBm/Hz ≤-113dBm/Hz

50kHz-5MHz ≤-126dBm/Hz ≤-126dBm/Hz ≤-130dBm/Hz

5MHz-1GHz ≤-136dBm/Hz ≤-136dBm/Hz ≤-140dBm/Hz

1GHz-2GHz - ≤-136dBm/Hz ≤-140dBm/Hz

2GHz-3GHz - ≤-126dBm/Hz ≤-130dBm/Hz

3、 Testing precautions

Terminal matching: A 50 Ω terminal must be used, otherwise impedance mismatch may cause high noise measurement;

Stray elimination: If there is significantly higher than the base noise at a certain frequency point (such as 1.25GHz, 2.5GHz), the noise values on both sides of the noise should be recorded, rather than the noise itself;

Average time: In the low-frequency range (such as 9kHz-50kHz), wait for 60 seconds to ensure that the average trace is stable before reading.