fresneldist

R2026b

Fresnel distance

Since R2026b

Syntax

distance = fresneldist(aper,lambda)

Description

distance = fresneldist(aper,lambda) returns the distance to the Fresnel zone of a radiator at wavelength lambda. This distance marks the transition from the near-field reactive region to the near-field radiative Fresnel zone. The input argument aper is the maximum width of the radiator aperture along any diameter.

Examples

Fresnel Distance of Radiator

Compute the Fresnel distance for a rectangular-shaped radiator having a one-by-two meter aperture. The radiated signal frequency is 30 kHz.

f = 30.0e3;
aper = [1 2];
lambda = physconst("LightSpeed")/f;
fd = fresneldist(max(aper),lambda)

fd = 
0.0175

Input Arguments

aper — Radiator aperture size

positive scalar

Radiator aperture size, specified as a positive scalar. The aperture size is the maximum width of the radiator aperture along any diameter. Units are in meters.

Example: 2.0

Data Types: double

lambda — Wavelength

positive scalar

Wavelength, specified as a positive scalar. Units are in meters.

Example: 1e4

Data Types: double

Output Arguments

distance — Fresnel distance of radiator

positive scalar

Fresnel distance (d_fres) of the radiator, returned as a positive scalar. Units are in meters.

Data Types: double

Algorithms

The Fresnel distance d_fres is defined as

$$d_{\text{fres}}=0.62\sqrt{{\frac{D}{\lambda }}^3},$$

where D is the maximum width of the radiator aperture along any diameter. λ is the wavelength. Units are in meters.

References

[1] IEEE Standards Antennas and Propagation Society, IEEE Recommended Practice for Antenna Measurements, 2001.

[2] Selvan, Krishnasamy T., and Ramakrishna Janaswamy, "Fraunhofer and Fresnel Distances: Unified Derivation for Aperture Antennas." IEEE Antennas and Propagation Magazine 59, no. 4 (June 2017): 12–15.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2026b