This calculator determines the main design parameters of a helical antenna based on the wavelength, the number of turns and the spacing between them. It provides gain, diameter, half-power beamwidth (HPBW), width at first minimum, and effective aperture.
It is useful for RF engineers, antenna designers, and students developing circularly polarized antennas for satellite, GPS, or Wi-Fi communications.
Formulas
Diameter: D = λ / 3.14
Circumference: C = π × D
Cλ = (π × D) / λ
HPBW = 52 / ( Cλ × √(N × S) )
First minimum = 115 / ( Cλ × √(N × S) )
Gain (dB) = 10.8 + 10 × log10(N × S)
Effective aperture: Ae = ( linear G × λ²) / (4 × π)
Explanation of formulas
- λ is the wavelength corresponding to the operating frequency.
- N represents the total number of turns of the antenna.
- S is the spacing between turns, expressed in multiples of the wavelength.
- The HPBW and gain formulas make it possible to evaluate the directional performance of the antenna.
- The effective aperture Ae indicates the equivalent surface area used to capture electromagnetic energy.
Design of a 2.4 GHz helical antenna
Input : λ = 0.125 m, N = 10, S = 0.25
Exit :
- Diameter (D) ≈ 3.98 cm
- HPBW ≈ 40.4°
- Gain ≈ 14.8 dB
- Effective opening ≈ 0.021 m²
Benefits and uses
- Simplified design of circularly polarized helical antennas.
- Quick estimation of gain and directivity depending on the number of turns.
- Optimization of parameters for satellite or amateur radio links.
- Useful for research and prototyping of high performance antennas.