Amplitude Taper
Understanding Amplitude Taper
Amplitude taper is the primary mechanism for controlling antenna sidelobe levels. Every real antenna faces a trade-off between narrow beamwidth (high gain) and low sidelobes. Taper functions provide different points on this trade-off curve.
Common Taper Functions
| Taper | SLL (dB) | Beamwidth Factor |
|---|---|---|
| Uniform | -13.2 | 1.00 |
| Cosine | -23 | 1.30 |
| Hamming | -43 | 1.36 |
| Taylor (-25 dB) | -25 | 1.10 |
| Taylor (-35 dB) | -35 | 1.25 |
| -30 dB Chebyshev | -30 | 1.20 |
The beamwidth factor indicates how much wider the main beam becomes relative to uniform illumination. Lower sidelobes always require wider beamwidth.
Frequently Asked Questions
What is amplitude taper?
Amplitude taper applies non-uniform amplitude across an antenna aperture to control sidelobes. Uniform illumination gives -13.2 dB SLL. Cosine gives -23 dB. Taylor gives configurable SLL. Lower sidelobes require wider beamwidth (reduced gain).
Why reduce sidelobes?
Sidelobes pick up interference and clutter from directions other than the main beam. In radar, high sidelobes create false targets. In communications, sidelobes cause interference with other users. Military systems need low sidelobes to resist jamming.
What is a Taylor taper?
Taylor distribution provides configurable near-in sidelobe level with far-out sidelobes that fall off as 1/u. It is the most practical taper for most antenna applications because it allows the designer to specify the desired SLL and how many near-in sidelobes to control.