Many analyzer measurements have considerable amounts of noise present in them. Except in those cases in which the noise is to be measured, the noise can be considered undesirable. Two basic techniques are used to reduce the noise-filtering and averaging. t Filtering usually takes the form of an analog filter, but it can also be implemented in digital form, while averaging is almost always done digitally. The two concepts are closely related and are treated here in a unified manner. Both filtering and averaging can be classified as either predetection (before the detector) or postdetection (after the detector). Predetection averaging/filtering reduces the noise present in a measurement while postdetection averaging/filtering reduces the amount of fluctuation in the noise.

Chapter Contents:

• 10.1 Predetection Filtering
• 10.2 Predetection Filters
• 10.3 Postdetection Filtering
• 10.4 Postdetection Filters
• 10.5 Averaging
• 10.6 Variance Ratio
• 10.7 General Averaging
• 10.8 Linear Weighting
• 10.9 Exponential Weighting
• 10.10 Averaging in Spectrum and Network Analyzers
• 10.11 Averaging Versus Filtering
• 10.12 Smoothing
• 10.13 Averaging in FFT Analyzers
• References

Inspec keywords: filtering theory; filters

Other keywords: noise averaging; predetection averaging; postdetection filtering; postdetection averaging; noise filtering; predetection filtering; analyzer measurement; noise measurement; analog filter

Subjects: Filtering methods in signal processing; Signal processing theory