# Which parameters defines a polar plot?

I need to convert a polar plot into a short array of 3-5 values. This array should describe the polar plot as best as possible.

For example, I know that I can use the beamwidth which is also known as the half power. This is the angle between the left and right -3 dB point: I also know that I can use the the ratio between the surface of the polar plot versus the whole 360° plane.

Thus, so long I only have two values in the array:

• Beamwidth
• Ratio polar plot vs plane

But are there other values that can describe the polar plot ? And also, how can I have a value which describes second biggest lobe ?

## migrated from math.stackexchange.comNov 11 '16 at 21:18

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• I asked a DSP moderator for an opinion, all in the interest of saving time. – Jyrki Lahtonen Nov 1 '16 at 10:57

## 1 Answer

Some examples would be the null to null bandwidth(s) as well as the sidelobe levels of the first/second sidelobes.

Example vector of 5 numbers: [mainlobe gain, first null location, 1st sidelobe gain, second null, 2nd sidelobe gain]

From this you could produce an estimate for the 3 dB points of each lobe using some "reasonable" formula, i.e. halfway between the peak and the null.