Calculator Inputs
Use one of four methods. The input area becomes a three-column grid on large screens, two columns on medium screens, and one column on mobile.
Formula Used
SLL(dB) = 20 × log10(Eside / Emain)
SLL(dB) = 10 × log10(Pside / Pmain)
Find the global main beam peak, exclude a chosen angular region around it, then compute 20 × log10(Aside / Amain) using the largest remaining sample.
More negative results indicate better sidelobe suppression. A uniformly weighted linear array often has a first sidelobe near -13.26 dB, while tapered arrays usually aim for more negative values.
How to Use This Calculator
- Choose the method that matches your available data.
- Enter amplitude, power, known dB, or sampled pattern values.
- For sampled patterns, provide matching angle and magnitude lists.
- Set a main beam exclusion angle to avoid counting the beam shoulder as a sidelobe.
- Click the calculate button to display the result below the header and above the form.
- Use the export buttons to save the result as CSV or PDF for reporting.
Example Data Table
| Case | Main Reference | Side Reference | Estimated SLL | Engineering Note |
|---|---|---|---|---|
| Uniform linear array | 1.000 amplitude | 0.217 amplitude | -13.26 dB | Common first sidelobe reference for uniform weighting. |
| Mild taper | 1.000 amplitude | 0.126 amplitude | -18.00 dB | Moderate sidelobe suppression with broader beamwidth. |
| Strong taper | 1.000 amplitude | 0.056 amplitude | -25.04 dB | Lower sidelobes at the cost of wider main lobe. |
| Sampled pattern case | Peak at 0° | Peak sidelobe at 30° | -12.77 dB | Derived by excluding the main beam region first. |
FAQs
1. What does side lobe level measure?
It measures how strong the highest sidelobe is compared with the main lobe. More negative values mean less unwanted radiation away from the intended beam direction.
2. Why are side lobe levels usually negative?
Because sidelobes are normally smaller than the main lobe. Taking the logarithm of a ratio below one produces a negative dB value.
3. When should I use the amplitude method?
Use it when your data comes from field strength, voltage, normalized array factor magnitude, or any other amplitude-based radiation pattern measurement.
4. When should I use the power method?
Use it when the pattern has already been converted into power quantities, such as intensity, gain-related power values, or simulated power density ratios.
5. Why does the sampled method need an exclusion angle?
The exclusion region prevents the calculator from treating the main beam shoulder or nearby samples as a sidelobe peak. That improves practical pattern interpretation.
6. Is a lower side lobe level always better?
Usually yes for interference control, clutter reduction, and spatial filtering. However, stronger tapering often widens the main beam and can reduce directivity.
7. What is a useful reference value for comparison?
A uniformly weighted linear array often has a first sidelobe around -13.26 dB. Designs with tapering typically target lower values such as -20 dB or below.
8. Can I use simulated antenna pattern samples here?
Yes. Paste matching angle and magnitude samples from your solver or measurement workflow. Choose linear or dB units correctly before calculating.