What is the Difference Between

Network

and

Spectrum

Analyzers?

8563A SPECTRUM ANALYZER 9 kHz - 26.5 GHz

Measures known signal Frequency

Network analyzers:

 measure components, devices,    circuits, sub-assemblies contain source and receiver display ratioed amplitude and phase (frequency or power sweeps) offer advanced error correction Measures unknown signals Frequency

Spectrum analyzers:

    measure signal amplitude characteristics carrier level, sidebands, harmonics...) can demodulate (& measure) complex signals are receivers only (single channel) can be used for scalar component test (

no phase

) with tracking gen. or ext. source(s) Spectrum Analysis Basics CMB 12/96 1

Overview

Types of Tests Made

Modulation Distortion Noise

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Overview

Frequency versus Time Domain Amplitude (power) Time domain Measurements Frequency Domain Measurements Spectrum Analysis Basics CMB 12/96 5

Overview

Different Types of Analyzers

A

Swept Analyzer

Filter 'sweeps' over range of interest CRT shows full spectral display

f

1

f

2

f

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Input signal

Theory of Operation

Spectrum Analyzer Block Diagram RF input attenuator mixer IF gain IF filter Pre-Selector Or Low Pass Filter local oscillator sweep generator Crystal Reference Log Amp detector CRT display video filter Spectrum Analysis Basics CMB 12/96 9

Theory of Operation

Mixer

MIXER

input f sig RF LO IF f LO f sig f LO f sig f LO f LO + f sig Spectrum Analysis Basics CMB 12/96 10

Theory of Operation

IF Filter

IF FILTER Input Spectrum IF Bandwidth (Resolution BW) Display

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Theory of Operation

Detector "bins"

DETECTOR

amplitude Positive detection: largest value in bin displayed Negative detection: smallest value in bin displayed Sample detection: last value in bin displayed Spectrum Analysis Basics CMB 12/96 12

Theory of Operation

Video Filter Video Band Width

VIDEO FILTER

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Theory of Operation

Other Components

RF INPUT ATTENUATOR IF GAIN LO SWEEP GEN

frequency

CRT DISPLAY

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0 f s 1 input 2

Theory of Operation

How it all works together 3 (GHz) Signal Range f LO f s f s LO Range f LO f LO + f s IF filter mixer 0 1 f s 2 3 3.6

4 5 6 6.5

3.6

f IF sweep generator A f LO 3 3.6

4 LO 5 6 6.5

(GHz) detector 0 1 2 3 (GHz) CRT display f Spectrum Analysis Basics CMB 12/96 15

Specifications

Sensitivity/DANL Effective Level of Displayed Noise is a Function of RF Input Attenuation signal level 10 dB Attenuation = 10 dB Attenuation = 20 dB Signal-To-Noise Ratio Decreases as RF Input Attenuation is Increased Spectrum Analysis Basics CMB 12/96 39

Specifications

Sensitivity/DANL: IF Filter (RBW) 10 dB 10 dB Displayed Noise is a Function of IF Filter Bandwidth 100 kHz RBW 10 kHz RBW 1 kHz RBW Decreased BW = Decreased Noise Spectrum Analysis Basics CMB 12/96 40

Specifications

Sensitivity/DANL: VBW Video BW Smoothes Noise for Easier Identification of Low Level Signals Spectrum Analysis Basics CMB 12/96 41

Specifications

Sensitivity/DANL For Best Sensitivity Use: 

Narrowest Resolution BW



Minimum RF Input Attenuation



Sufficient Video Filtering (Video BW < .01 Res BW)

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