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【Q&A】RF Spectrum Analyzer Question and Attentions ( Part 3 )
Release time :2017.11.16 Reading quantity:16 source:Salukirf, original

Q1: Why I need a tracking source?

A: The tracking source is one of the common options of a RF spectrum analyzer. Tracking source output port is connected to DUT input port. Meanwhile the RF spectrum analyzer input port is connected to DUT output port. Here the spectrum analyzer and the tracking source build a frequency sweep measurement system. The frequency tracking source output and spectrum tuning frequency are coupled. Spectrum analyzer with tracking source option, can be used as a simple scalar network analyzer, observed measurement of the incentive response characteristics of the device, such as: the frequency response of the device, insertion loss and so on.

Saluki S3531 / S3532 / S3331 spectrum analyzers all have optional tracking source. S3531 and S3532A even have a build-in CW source. User can set the CW source output frequency and spectrum analyzer tuning frequency separately. 

S3531 2 PORTS.pngFigure 1 S3531 Portable RF Spectrum Analyzer ( 9kHz - 3GHz)


Q2: How to select between SWEEP mode and FFT mode?

A: Modern spectrum analyzer usually have sweep mode and FFT mode. Usually FFT is faster than SWEEP with a narrower RBW setting, but SWEEP mode is faster with a wider RBW.


Figure 2 Structure of a FFT Spectrum Analyzer

Usually the sweep mode is selected by the RF spectrum analyzer automatically. For Saluki S3532 / S3531 / S3331 RF spectrum analyzers, when RBW >10Hz, the sweep mode is SWEEP and when RBW <10Hz, the sweep mode is FFT.


Q3: How to select the right detector? 

A modern spectrum analyzer usually has types of detectors. The most common detectors are: Peak, Sample, Neg-Peak, Normal, RMS

l  Peak detector: select the maximum value of each bucket as a measurement value. This detection method is suitable for continuous wave signal and signal search test.

l  Sample detector: Sample detector is usually suitable for noise and "noise-like" signal test.

l  Neg-peak detector mode: suitable for small signal test such as EMC test.

l  Normal Detector: suitable for observing signals and noise at the same time.

RMS Detector: Calculate a RMS value for each bucket as the measurement result. Equation show below. Use RMS detector, user can get a smooth trace, however weep speed will be slower.