Antenna Design — Complete Guide

Antenna gain combines directivity and efficiency. A half-wave dipole has about 2.15 dBi of gain — modest but omnidirectional in the azimuth plane. EIRP = Tx power + antenna gain − cable loss. Use the EIRP calculator to check regulatory compliance and compute effective radiated power in dBm or dBW.

A resonant half-wave dipole has a feed impedance of approximately 73 Ω in free space and needs a balun when fed with coaxial cable to suppress common-mode current. The dipole antenna calculator gives resonant length from frequency, accounting for velocity factor. For compact installations, a folded dipole doubles the feed impedance to about 300 Ω, ideal for twin-lead or folded matching sections.

Patch antennas are low-profile and easily integrated into PCB designs at 1 GHz and above. The resonant length is approximately λ/2 in the substrate dielectric. The patch antenna calculator computes patch dimensions, feed point location, and estimated gain from substrate permittivity and thickness. Bandwidth is typically 1–5% for a single resonant element.

Yagi antennas achieve high gain (6–20 dBd) with a simple boom-and-element structure. Adding directors increases gain; element spacing and length tuning are critical for good front-to-back ratio. The Yagi antenna calculator computes element lengths and spacing for a given boom length and number of elements, using the Leeson algorithm.

Loop antennas are compact relative to wavelength and exhibit a figure-eight pattern with a deep null off the axis. The loop antenna calculator computes radiation resistance, efficiency, and Q for single-turn and multi-turn small loops. High Q means narrow bandwidth, so tuning networks are usually required.

Parabolic reflectors achieve the highest practical antenna gains (20–50 dBi) by focusing a feed element's radiation. Gain = η·(πD/λ)². The parabolic dish antenna calculator computes gain, half-power beamwidth, and aperture efficiency from dish diameter and frequency. Check the antenna beamwidth calculator to verify the 3 dB beam fits your coverage requirement.