Helical Antenna

Calculate the gain, impedance, dimensions, and beam characteristics of a helical antenna.

Helical antennas are one of the easiest antenna types to design. The conductor width isn't of great importance in the design — the greater the number of turns, the greater the directivity or antenna gain. Make sure to keep the winding on both receiving and transmitting antennas in the same direction, since the wave is polarized.

Understanding Helical Antenna Design

A helical antenna, characterized by its conducting wire wound in a spiral shape, finds extensive application in high-frequency operations. The polarization characteristics of this antenna are contingent upon factors including diameter, turns count, excitation, spacing between loops, pitch, and wavelength.

Design Considerations

Parameter	Effect
Diameter	A greater diameter leads to reduced impedance and a broader radiation pattern
Number of Turns	Increasing the number of turns broadens the frequency spectrum while narrowing the radiation pattern
Excitation	Impacts both the radiation pattern and polarization — can occur in either axial or normal mode
Space Between Loops	Reducing the space leads to a more focused radiation pattern and increased impedance
Pitch	A greater pitch widens the frequency range while narrowing the radiation pattern
Wavelength	A greater wavelength leads to a broader radiation pattern and reduced impedance

Types of Helical Antennas

Type	Description
Normal Mode Helical Antenna	Excited conventionally; used for emitting circularly polarized radiation
Axial Mode Helical Antenna	Excited axially; used for emitting linearly polarized waves

Advantages

Wide Bandwidth: Helical antennas possess a broad frequency range, rendering them applicable across diverse usage scenarios
High Gain: Significant gain makes them appropriate for applications necessitating a robust signal-to-noise ratio
Circular Polarization: Capable of generating circularly polarized radiation, making them apt for applications requiring circular polarization

Applications

Satellite Communications: Used for both signal reception and transmission
Radar Systems: Used to detect and monitor targets
Wireless Communication Systems: Used for both signal transmission and reception

Conclusion

The design process of helical antennas encompasses several elements including diameter, turn count, excitation, spacing between loops, pitch, and wavelength. These parameters significantly influence the antenna's radiation pattern, impedance, and polarization. Helical antennas offer broad bandwidth, high gain, and versatility in producing circularly polarized radiation, rendering them applicable across diverse fields.

About This Calculator

This online calculator helps you calculate the following parameters for a helical antenna:

Antenna Gain (G)
Characteristic Impedance (Z)
Diameter (D)
Space Between Coils (S)
Length of Wire (L)
Half Power Beam Width (HPBW)
Beam Width First Nulls (BWFN)
Effective Aperture (Ae)

Formulas

$G = 10.8 + 10 \times \log_{10}\left(\left(\frac{C}{\lambda}\right)^2 \times N \times \frac{S}{\lambda}\right)$

$Z = \frac{150}{\sqrt{\dfrac{C}{\lambda}}}$

$D = \frac{\lambda}{\pi}$

$S = \frac{C}{4}$

$L = N \times \sqrt{\lambda^2 + S^2}$

$HPBW = \frac{52}{\dfrac{C}{\lambda} \times \sqrt{N \times \dfrac{S}{\lambda}}}$

$BWFN = \frac{115}{\dfrac{C}{\lambda} \times \sqrt{N \times \dfrac{S}{\lambda}}}$

$A_e = \frac{G \times \lambda^2}{4\pi}$

where:

$G$ = Antenna Gain (dBi)
$Z$ = Characteristic Impedance (Ω)
$D$ = Diameter (m)
$S$ = Spacing Between Coils (m)
$L$ = Length of Wire (m)
$HPBW$ = Half Power Beam Width (degrees)
$BWFN$ = Beam Width First Nulls (degrees)
$A_e$ = Effective Aperture (m²)
$C$ = Circumference of a turn on the helix antenna (m)
$\lambda$ = Wavelength (m)
$N$ = Number of Turns

Inputs

Wavelength(m)

Operating wavelength in metres. If provided, frequency is derived automatically

Frequency(MHz)

Operating frequency in MHz. If provided, wavelength is derived automatically. One of wavelength or frequency must be greater than zero

Number of Turns

Number of turns in the helix

Space Between Coils(wavelength)

Axial spacing between turns as a fraction of wavelength (typically 0.2–0.35 for axial mode)

Results

⚠Enter either wavelength or frequency — one must be greater than zero

Antenna Gain—dBiAntenna gain in dBi

Impedance—ΩInput impedance of the helical antenna in ohms

Diameter—cmHelix diameter in centimetres

Space Between Coils—cmPhysical spacing between turns in centimetres

Length of Wire—cmTotal wire length of the helix in centimetres

Half Power Beam Width—°Half power beam width in degrees

Beam Width First Nulls—°Beam width between first nulls in degrees

Aperture—m²Effective aperture of the antenna in square metres