EE 198 B Senior Design Project
Dec 22, 2015
Definition of an Analyzer
Analyzes the spectral content (amplitude and frequency) of the input signal.
Analyzes the various harmonics present in the signal.
Application Used to measure signal characteristics
such as carrier level, sidebands, harmonics, and phase noise.
Used to measure the spectral purity of multiplex signals and the percentage of modulation of AM signals.
Can analyze distortion and spurious signals, and can determine the non-linearity in a system.
Specifications:
Input Frequency: 0-500 KHz Dc Voltage Maximum: +/- 5 V
amplitude Number of Bits = 8 bits Resolution: 0.04 V FS: Sampling Frequency = 20 MHz Number of Harmonics used = 3
FunctionGenerator
Power Supply
Circuit Board
OscilloscopeCOMPUTERPentium 4
256 MB RAM
NI PCI 5102 Digitizer
BLOCK DIAGRAM OF THE SYSTEM
Block Diagram of Software
Low Pass Filter
DistortionMeasurement
Input
FFT (Spectral)
ToneMeasurement
Amplitude& Level
Measurement
Write LabVIEW
Block Diagram of the Input
NI Scope Initialize
NI Scope Auto Setup
NI Scope Multi Read
NI Scope Close Error Handler
Index Array Un bundle by Name
Build Waveform
Convert to Dynamic Data
Input to the Express VI’s
Input A cluster of waveforms are
accessed. The waveforms are separated out
into indices in an array. A single waveform is extracted and
expanded to three signals wide. The single resulting waveform is
converted to dynamic data for use by the Express VI’s.
Low pass Filter
Why Butterworth? It has a smooth response at all
frequencies and it is maximally flat.
Why order 3? High order is chosen to give more
accuracy.
Fast Fourier Transform (FFT)
Main calculation block for the output.
Displays the frequency response - Vrms (dB) versus frequency.
Also displays the phase in degrees or radians.
Harmonic Distortion Measurement Block Integral multiples of the
fundamental frequency (f): 2f, 3f, 4f...and so on are called harmonics.
The higher the number and amplitude of the harmonics, the more distorted is the system.
Helps to measure the non-linearity of a system.
Distortion Parameters
THD: is the sum of the powers of all harmonic frequencies above the fundamental frequency to the power of the fundamental frequency.
Specific Harmonic: returns the value of the harmonic that is specified, in this case it is three.
Tone Measurements
Finds the single tone with the highest amplitude.
Searches a specified frequency range to find the single tone with the highest amplitude.
All outputs (Amplitude, Frequency and Phase) have numeric displays.
Amplitude/Level Measurements
Performs voltage measurements and analysis on the input signal.
Returns the DC voltage, AC Positive Peak and Negative Peak, Peak to Peak voltage, RMS (root mean square) of the input signal.
Above parameters have numeric display at the front panel.
Write LabVIEW Writes data to a LabVIEW data
measurement file. It receives input from Spectrum
Measurement Block’s FFT. The File Name and Comments Input are
entered through Dialog Box by the user. The outputs are File Name, Saving Data. This file can be accessed using Microsoft
Excel.
How is ours Better?
The input from the NI-Scope Digitizer was made compatible with the LabVIEW Express VI’s for the first time ever.
Cost Comparison HP/Agilent 860E Spectrum Analyzer (input
frequency: 30hz – 2.9Ghz) sold at $27,530
Our cost DAQ Card + Probes = $1500 Computer = $900 Software = Free…Student Version Total = $2400
Low Pass Filter Gain from the Spectrum Analyzer (up to 100 KHz)
Gain vs. Freq (Analyzer)
-16
-14
-12
-10
-8
-6
-4
-2
0
2
0 20000 40000 60000 80000 100000 120000
Freq (Hz)
Ga
in (
rms
dB
)
Series1
Gain vs. Freq
0
2
4
6
8
10
12
14
16
18
20
0 200000 400000 600000 800000 1000000 1200000
Freq (Hz)
Ga
in (
dB
)
Scope
Analyzer
Common Emitter Gain vs. Freq (Scope & Analyzer)
Testing Spectrum Analyzer
First order high pass filter using LM741 Op-Amp.
Compare results taken from the Spectrum Analyzer with results from the Oscilloscope.
Resulting graphs are plotted in Excel.
High pass filter Excel graph:up to 50 kHz
-30
-25
-20
-15
-10
-5
0
0 10000 20000 30000 40000 50000
Frequency(Hz)
Gai
n(dB
)
Illustration of Non-Idealities in an Op-amp
From 100 kHz to 4MHz
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
0 1000000 2000000 3000000 4000000 5000000
Frequency(Hz)
Gain
(dB
)
Results Found The graphs from the Oscilloscope and the
Spectrum Analyzer follows the same shape. They follow the same characteristics of a first
order high pass active filter using LM741 Op Amp.
Data from the scope are taken using the scope itself, while data from the Spectrum Analyzer are taken from the FFT graph.
As the frequency of a High Pass increases, the performance of the filter degrades as shown in the graph.