Spectrum Analyzer
Hello!I am Tahrimur Rahman
MyRoll: 12102907Session: 2011-123rd year 2nd semester Dept. of
Electronics and Communication EngineeringJ.K.K.N.I.U.
Spectrum Analyzer
Outline: My process is easy & simpleWhat?Why?How?Where?
What?SpectrumThe observed distribution of a phenomenon across a
range of measurement. Likely, power spectrum, frequency spectrum
etc.AnalyzerAn analyzer is a person or device that analyses given
data. It examines in detail the structure of the given data and
tries to find patterns and relationships between parts of the
data.As a communication engineer our princple interest is signal
and their measuring instrument; Thus Spectrum Analyzer is an
instrument which graphically provides the energy distribution of a
signal as a function of the frequency on its CRT.
The measurement of dominant frequencies and their responses.The
component levels and energy strengthFrequency stability Bandwidth
and Spectral purityModulation index and attenuationHarmonic and
intermodulation distortionVarious signal generation and so on
Which is not easy to measure at time domain
Why?The spectrum analyzer provides information about all these
things, by displaying the signal in the frequency domain.
Now a question may arise. Can we not use an Osciloscope for
above purposes ?
No; because ofFirstA spectrum analyzer displays received signal
strength (y-axis) against frequency (x-axis). An oscilloscope
displays received signal strength (y-axis) against time
(x-axis).SecondThe spectrum analyzer measurements are in frequency
domain, whereas the oscilloscope measurements are in time
domain.FourthSpectrum analyzer uses complex circuitry compared with
an oscilloscope. As a result of this, the cost of a spectrum
analyzer is usually quite high.FifthNormally, an oscilloscope can
not measure very low voltage levels (say,100 dBm) and are intended
for low-frequency, high-amplitude measurements. A spectrum analyzer
can easily measure very low amplitudes (as low as 120 dBm), and
high frequencies (as high as 150 GHz).ThirdA Spectrum analyzer is
useful for analyzing the amplitude response of a device against
frequency. The amplitude is normally measured in dBm in spectrum
analyzers, whereas the same is measured in volts when using
oscilloscopes.
How?The spectrum analyzer is said to operate in the frequency
domain because it allows one to measure the harmonic content of an
electric signal, that is, the power of each of its spectral
components. In this case, the vertical and horizontal scales read
powers and frequencies.
A simplified block diagram of Spectrum Analyzer
It consists of the following parts:
1. Front-end mixer2. Voltage controlled oscillator3. Saw-tooth
generator4. IF amplifier5. Detector6. Video amplifier7. Cathode Ray
Tube (CRT)
LimitationsEvery device has .. So It also.
Where?It is common to see spectrum analyzer in the fields of
following applications:Device Frequency Response Measurements:
broadband amplifier, narrowband filter etc. Monitoring: transmitted
power and received power of a microware tower. In this way, you can
verify that the frequency and signal strength of your transmitter
are according to the specified values.Other specialized
applications : RFI , EMI, EMC etc.Interference Measurements:
telecom microwave towers, TV stations, airport guidance systems
etc.Satellite: Return-loss measurement, Satellite antenna alignment
etc.
And so on.
Thanks!Any questions?You can find me
at:www.facebook.com/[email protected]
