what does it actually stands and mean.i understand smaller RBW is better. how to simulate RBW in FFT in matlab. sample codes would be great help. thanks.
- posted
17 years ago
spectrum analyzer resolution bandwidth
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- posted
17 years ago
it is the IF bandwidth of the analyser, or in other words the instantaneous bandwidth of the signal that is being detected. Smaller resolution BW allows for the ability to discern between signals that are close together.
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17 years ago
no you dont. it completely depends upon the application. what is the required BW? Sweep time etc. for a given span SW is proportional to
1/(RBW)^2what are you trying to do?
look at
formatting link
and google spectrum analyzer basics
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17 years ago
Amdy comments:
The resolution bandwidth should be wide enough so that the signal characteristics which you are interested in will not be attenuated. It should be narrow enough to separate the elements of the signal(s) to see their relative position.
Sometimes both of these are not possible at the same time, Sometimes you can switch from one bandwidth to the other to ascertain both the position and the true amplitude of the various components.
Often you can adjust the sweep speed to trot the signal thru a narrow bandwidth at a slower rate, which allows the full amplitude to be realized. Hence, res bandwidth interacts with sweep speed.
In any case, the video bandwidth, which is set after the detection process should be wide enough not to interfere with the IF resolution bandwidth.
The setting obviously depend on what you are trying to learn from the signal(s) you are looking at, their modulation, and their timing. In other words, there ain't no universal answer....
Andy in Eureka, Texas
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17 years ago
When an analog spectrum analyzer displays a point at a given frequency f0, what it's really doing is displaying the total energy it "saw" (detected and measured) between f0-RBW/2 and f0+RBW/2. In other words, the RBW is the (usually -3dB) bandwidth of a bandpass filter that's centered around your frequency of interest.
Welllll... if you have an FFT that has enough points such that the bin spacing (in Hz) is considerably smaller than the RBW you want to simualte, just design a bandpass filter with the specified RBW and convolve with at each frequency point of interest to generate a new output. (If the bin spacing starts to approach the size of your RBW, since each "bin" performs a certain amount of filtering, you get significant interaction between the filters and your result won't be correct. Rick Lyon's book discusses this in detail).
---Joel Kolstad