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![Different Types of Analyzers
1] Fourier Transform Analyzer
2] Swept-Tuned Analyzer](https://image.slidesharecdn.com/spectrumanalyzer-150921234357-lva1-app6891/85/Spectrum-analyzer-8-320.jpg)
Uploaded byMohammed AbouHaggar
Spectrum analyzer
Spectrum analyzers measure the magnitude and frequency of input signals. There are two main types: Fourier transform analyzers which use digital signal processing to analyze the entire frequency range simultaneously, and swept-tuned analyzers which use analog filters to sweep through the frequency range. Key specifications for spectrum analyzers include frequency range, amplitude range and sensitivity to measure small signals, resolution bandwidth to distinguish closely spaced frequencies, and dynamic range to measure large and small signals simultaneously.
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Spectrum analyzer
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- 2. What is aSpectrum Analyzer? A spectrum analyzer measures the magnitude of an input signal versus frequency within the full frequency range of the instrument.
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- 5. Analysis Domains Time Domain(Oscilloscope) • See what changes in time. • If signal has many frequencies ,analysis become difficult. Frequency Domain (Spectrum analyzer) • Each element of a complex signal can be separated easily. • Low-level distortion signals can be detected.
- 6. Analysis Domains Modulation Domain(Modulation analyzer) • See how frequency changes. • Measures modulation accuracy
- 8. Different Types ofAnalyzers 1] Fourier Transform Analyzer 2] Swept-Tuned Analyzer
- 9. Parallel filters measured simultaneously CRTshows full spectral display A ff1 f2 Fourier Analyzer
- 10. Fourier Analyzer • TheFourier analyzer basically takes a time-domain signal, digitizes it using digital sampling, and then performs the mathematics required to convert it to the frequency domain, and display the resulting spectrum.
- 11. Fourier Analyzer • Itis as if the analyzer is looking at the entire frequency range at the same time using parallel filters measuring simultaneously. • The Fourier analyzer is able to capture periodic as well as random and transient events.
- 12. Fourier Analyzer • Howeverit does have its limitations, particularly in the areas of frequency range, sensitivity, and dynamic range. • Fourier analyzers are becoming more prevalent, as ADC converters and DSP technologies advance. • These analyzers can offer significant performance improvements over conventional spectrum analyzers, but often with a price premium.
- 13. A ff1 f2 Filter 'sweeps' overrange of interest CRT shows full spectral display Swept Analyzer
- 14. Swept Analyzer • Themost common type of spectrum analyzer is the swept-tuned receiver, displaying all the frequency components present. • The swept-tuned analyzer works just like the AM radio in your home except that on your radio, the dial controls the tuning and instead of a display, your radio has a speaker.
- 15. Spectrum Analyzer BlockDiagram
- 16. Mixer • The outputfrequencies that will be produced by the mixer are the original input signals, plus the sum and difference frequencies of these two signals. • It is the difference frequency that is of interest in the spectrum analyzer. • We call this signal the IF signal, or Intermediate Frequency signal.
- 17. IF Filter • TheIF filter is a band pass filter which is used as the "window" for detecting signals. It's bandwidth is also called the resolution bandwidth (RBW) of the analyzer and can be changed via the front panel of the analyzer.
- 18. Envelope Detector • Theanalyzer must covert the IF signal to a baseband or video signal so it can be digitized and then viewed on the analyzer display. This is accomplished with an envelope detector whose video output is then digitized with an ADC. • The digitized output of the ADC is then represented as the signal’s amplitude on the Y-axis of the display. This allows for several different detector modes of how the signal is displayed.
- 19. Video Filter • Thevideo filter is a low-pass filter that is located after the envelope detector and before the ADC. This filter determines the bandwidth of the video amplifier, and is used to average or smooth the trace seen on the screen.
- 20. Other Components • Thelocal oscillator (LO) s a Voltage Controlled Oscillator (VCO) which in effect tunes the analyzer. The sweep generator actually tunes the LO so that its frequency changes in proportion to the ramp voltage. • The RF attenuator attenuates the input signal to a suitable mixer input level. • The IF gain is used to adjust the vertical position of signals on the display without affecting the signal level at the input mixer.
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- 22. Theory of Operation •The signal to be analyzed is connected to the input of the analyzer. • This signal is then combined with the LO through the mixer to convert it to an IF. • These signals are then sent to the IF filter, whose output is detected, indicating the presence of a signal at the analyzer's tuned frequency.
- 23. Theory of Operation •The output voltage of the detector drives the vertical axis (amplitude) of the LCD display. The sweep generator provides synchronization between the horizontal axis (frequency) and tuning of the LO. • The resulting display shows amplitude versus frequency of the spectral components of each incoming signal.
- 24. Specifications 1) what's thefrequency range? 2) what's the amplitude range (maximum input and sensitivity)? 3) to what level can I measure the difference between two signals, both in amplitude (dynamic range) and frequency (resolution)? 4) how accurate are my measurements once I've made them?
- 25. Frequency Range- Resolution • Therange of frequencies that device works on. • Resolution is an important specification when you are trying to measure signals that are close together and want to be able to distinguish them from each other.
- 26. Sensitivity • One ofthe primary uses of a spectrum analyzer is to search out and measure low-level signals. • The sensitivity of any receiver is an indication of how well it can measure small signals. • A perfect receiver would add no additional noise to the natural amount of thermal noise present in all electronic systems. • In practice, all receivers, including spectrum analyzers, add some amount of internally generated noise.
- 28. Dynamic Range • DynamicRange is defined as the maximum ratio of two signal levels simultaneously present at the input which can be measured to a specified accuracy. You can imagine connecting two signals to the analyzer input - one which is the maximum allowable level for the analyzer's input range and the other which is much smaller. The smaller one is reduced in amplitude until it is no longer detectable by the analyzer. When the smaller signal is just measurable, the ratio of the two signal levels (in dB) defines the dynamic range of the analyzer.