This presentation discusses distortion analysis using a distortion analyzer. It defines distortion as any alteration in a signal's waveform. A distortion analyzer is used to analyze distortion, which is needed to ensure proper output from a signal. The presentation describes the basic block diagram of a distortion analyzer and its operation principle. It then explains different types of distortion analysis that can be performed using a distortion analyzer, including frequency/amplitude distortion analysis, harmonic distortion analysis, intermodulation distortion analysis, and phase distortion analysis. Finally, it shows an image of a laboratory-quality distortion analyzer that can precisely measure low levels of distortion.

1. WELLCOME TO MY PRESENTATION

2. Presented By
Mishuk
Department of Electronics & Communication Engineering
Jatiya Kabi Kazi Nazrul Islam University
Trishal, Myensingh

3. Distortion analyser
 Any alteration in the waveform of a signal is distortion.
Distortion is occurred due to undesired change in an
electric signal waveform as it passes from the input to
the output of some system or device When an amplifier
is not operating in a linear fashion, the output signal
will be distorted.
 Distortion is analyzed by distortion analyzer. Distortion
analysis is needed to gate the proper output of a signal.
 A basic distortion analyser diagram is shown below

4. Block Diagram
 A block diagram for a fundamental distortion analyzer is shown in
Figure. When the instrument is used. switch S, is set to the "set level"
position, the band pass filter is adjusted to the fundamental
frequency and the attenuator network is adjusted to obtain a full-
scale voltmeter reading.
 Switch S, is then set to the "distortion" position, the rejection f:1ter is
turned to the fundamental frequency, and the attenuator is adjusted
for a maximum reading on the voltmeter.
Figure: Block diagram of a distortion analyzer.

5. Operation principle
 In operation, the filter switch is set for the desired frequency and the
signal source tuned until a null occurs. A balance control is provided on
the set to assist in obtaining the null. After the null has been obtained
and a reading taken on the detector, the switch is set so that the
attenuators replace the filter in the circuit. The attenuators are then
adjusted so that the same reading is obtained on the detector as when
the null was obtained.
The reading of the attenuators then gives the value of the distortion
level in decibels below the signal level. The filters in the set have a
rejection characteristic of at least 60 db, while the attenuators have a
combined range of 70 db so that distortions as low as 0.1% can be read.

6.  Some distortion analysis through distortion analyser are as follows:
 Frequency or amplitude distortion analysis.
 Harmonic distortion analysis.
 Inter-modulation distortion analysis.
 Phase distortion analysis.

7. Frequency or amplitude distortion
analysis
 The test equipment used consists of a variable frequency oscillator, a
calibrated variable attenuator and a level meter. Measurements are taken at
sufficient spot frequencies to construct a response curve. At each spot
frequency, the attenuator is adjusted until the meter reads the same for
both positions of the switch shown. The Gains of the amplifier is then equal
to the calibration value on the attenuator. In this arrangement, the output
resistance of the oscillator must match the input resistance of the
attenuator and the output resistance of the attenuator must match the
input resistance of the amplifier.
Figure: Frequency analysis

8. Harmonic distortion analysis
 Harmonic distortion in any signal transmission device results from
non-linearity in the device transfer characteristic. Additional
frequency components, harmonically related to frequencies fed into
the input, appear at the output in addition to the reproduction of the
original input components.
Measurement of harmonic distortion can be carried out by feeding a
sine wave into the input of the device and separating the sine wave
from its harmonics at the output. Distortion is measured as the ratio
of harmonic level to the level of the fundamental frequency. This is
usually expressed as a percentage but sometimes also expressed as a
decibel. Expressed as
where
THD = the total harmonic distortion
lfundamenta
harmonics
THD
2
)(


9. Inter-modulation distortion analysis
 If any form of non-linearity exists in a signal processing device,
intermodulation products are generated when two or more individual
frequency components are fed through the device. Two individual
frequencies generate two additional components equal to their sum
and difference frequencies plus, to a lesser extent, more complex
products involving harmonics of the two frequencies.
Intermodulation distortion is measured by feeding two different
frequency sine waves to the device input and separating out the
intermodulation components from the primary frequencies at the
output. The relative level of intermodulation components to primary
frequencies is a measure of the degree of intermodulation.

10. Phase distortion analysis
 Transmission circuits and networks with reactive elements almost always
introduce different phase delays for different frequencies. There is no
problem if there is a linear phase characteristic, ie phase shift is directly
proportional to frequency. The ratio of change in phase to change in
frequency is given the name of Group Delay (Tg) which is expressed as
follows:
Tg = A0/360Af
where A0 = phase change in degrees
and Af = frequency change in Hertz

11. Laboratory-quality distortion
analyzer
A typical laboratory-quality distortion analyzer is shown in Figure. The
instrument shown, a Hewlett-Packard Model 334A. It is capable of
measuring total distortion as small as 0.1% of full scale at any
frequency between 5 Hz and 600 kHz. Harmonics up to 3 MHz can be
measured.
Figure: Laboratory-quality distortion analyzer.(HP 334A)

12. THANKS EVERYBODY FOR
YOUR PATIENCE