What is the difference between spectrum analyzer and oscilloscope?

Several situations would require you to get full information of time and frequency signals from an analysis, most times it would be an essential part of setting up radio signals, microphone, speakers, cell phones and several other electronic devices that would involve signals.

The basic function of both the spectrum analyzer and the oscilloscope is to give a better view with analyzing electrical signals, although the most obvious difference between them is that the display of the oscilloscope reveals signal concerning frequency and oscilloscope shows messages concerning time.

Even though they are different devices, some models functions as both a spectrum analyzer and an oscilloscope. The difference between both devices wouldn’t reduce their importance and efficiency in any analyzing electronic signals.

Let’s break them down

We would have a brief breakdown of the spectrum analyzer and the oscilloscope, by explaining them and we would mention some features that would point out their differences

The Spectrum Analyzer

As the name implies, this device analyses radiofrequency spectrums like the harmonics of a signal. It is an electronic instrument used to observe known and unknown signals with respect to their frequencies. The spectrum analyzer measures the magnitude of a signal set it against the frequency range of the equipment, meaning it measures how the signal changes in respect to the different frequencies.

This device looks so much like the oscilloscope with the display also in a graphical form, but the amplitude is on the y-axis and frequency on the x-axis

The spectrum analyzer is useful for different types of measurements in a test laboratory or field services and when you are designing a radiofrequency generating equipment. They reveal details on the amplitude or strength of radio frequencies and audio signals determining the efficiency and performance of a circuit or a device producing signals.


The oscilloscope

The oscilloscope, on the other hand, is used to get detailed information about the timing of several detected signals. As the spectrum analyzer reveals frequency, the primary job of the oscilloscope is to find the relative delay of timings between two separate signals.

Although this electronic instrument allows you to observe various voltage signals represented on a two-dimensional view with a plot of amplitude as a function of time, some signals like sound and vibrations can also be measured on an oscilloscope as voltages.

Properties like amplitude, distortions, frequencies, time intervals, and several others can be analyzed by the waveforms displayed on the oscilloscope, while some modern oscilloscope brands can calculate and display these properties directly to you.

A storage oscilloscope can capture a single event and display it for a long time for precise observation. The device also features an adjustment that allows you to view the continuously repeated signals on the screen.


Comparison between the spectrum analyzer and oscilloscope

Now we would pick out some factors that can separate them like the real-time bandwidth, dynamic range, sensitivity, and power measurement accuracy. We would also mention their pros and cons.

Real-time Bandwidth

The real-time bandwidth determines how the device would perform with ultra-wide signal analysis, and here we would discuss how both devices analyze signals in real time.

Spectrum AnalyzerThe spectrum analyzer refers to immediate and resolution bandwidths, where final analog immediate frequency can be used as the real-time bandwidth for that analysis. Some brands of spectrum analyzers have only a few megahertz, even wide bandwidth are just tens of megahertz, and the widest can reach 500 megahertz.

Oscilloscope, on the other hand, are better than spectrum analyzers when it comes to real-time bandwidth, it measures the bandwidth from its frequency range, and is more useful for real-time sampling with hundreds of megahertz ranging to several gigahertz. Real-time oscilloscopes have vertical scale settings different from one another and the ones set with the most sensitivity decreases the real-time bandwidth.

Dynamic Range

The dynamic range would reveal the differences between the maximum and the minimum signal measured by the devices and in this case, the measurement setting affects their level difference.

From the near-end noise and spurious conditions of the average noise level, second-order and third-order distortion, the spectrum analyzer’s dynamic range is limited and can be calculated based on the specifications. The limiting factors of the oscilloscope are the limited number of analog to digital sampling bit and the noise floor.

The ideal dynamic range for the spectrum analyzer is about 90 decibels, and the oscilloscope has a dynamic range of about 50 decibels which makes the spectrum superior when it comes to dynamic range.

Sensitivity

We would refer to sensitivity as the level of minimum signal the spectrum analyzer and the oscilloscope can handle. In this case, the oscilloscope is better in that it can test minimum signals at 1mV/div.

Power Measurement Accuracy

The power measurement accuracy might be the most critical factor of all because, for both instruments, the influence is enormous. The power measurement of both devices is at about 1GHz frequency signal, and the difference is only slight.

The impact of power measurement accuracy on the spectrum analyzer is reference level error, attenuator error, bandwidth conversion error, calibration signal error, frequency response and a port mismatch caused by reflection.

On the other hand, the impact of power measurement on the oscilloscope is a vertical system error, AD quantization error, calibration signal error, frequency response and a port mismatch caused by reflection.

The spectrum analyzer and the oscilloscope cannot be compared by these properties one after the other, and even though the frequency range of the oscilloscope is better, but the spectrum analyzer measuring at 1GHz makes it an excellent measurement accuracy indicator.


Pros and Cons

Pros

Cons

Spectrum analyzer

 

 

 

 

  • Useful for analyzing amplitude of device against frequency
  • Measures amplitude in dBm
  • Concerned with higher sensitivity
  • Measures long-term and short-term frequency stability
  • Detects only CW signals without phase information
  • Cannot low voltage and frequency as the oscilloscope.
  • Limitations of bandwidth support

Oscilloscope

 

 

 

 

  • Useful for analyzing amplitude of device against timing
  • Measures amplitude in volts
  • Measure low voltage and frequency
  • Better with real-time bandwidth measurement

 

  • Oversensitive to signal noise
  • ·More expensive than spectrum analyzers
  • No storage memory available
  • Cannot analyze high frequency.

 


Wrap-up

Spectrum analyzers are superior to oscilloscope terms of sensitivity, and the oscilloscope is better when you need a device for a better real-time bandwidth.

Also, the spectrum analyzer may not be able to measure some transient signals as much as the oscilloscope, so in some situations, the oscilloscope is better in performance than the spectrum analyzer.

So you see that both devices are necessary, even though their various applications for different fields all you have to do is understand their functions.

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