Engineering results
Results update after calculation and remain visible above the form.
Engineering charts and visualizations
Distance sweep table
No sweep calculated.| Distance | Region | Electric field | Magnetic field | Power density | Wave impedance | Dominant term |
|---|---|---|---|---|---|---|
| Calculate the analysis to populate this table. | ||||||
Formula used
The calculator combines boundary equations with practical field estimates. Reactive corrections represent stored and induction terms near antennas. Exact geometry may require a full-wave electromagnetic solver.
Lossy-medium wave impedance uses an engineering magnitude approximation. Array results include scan and spacing checks. Exposure comparisons use limits entered by the user.
Phase error and Fresnel values use the largest aperture dimension. This convention supports fast engineering screening. Always document the selected boundary method.
How to use this calculator
- Select a preset or keep the custom setup.
- Choose the analysis mode and field model.
- Enter frequency, antenna size, and observation distance.
- Define the material and transmitter operating conditions.
- Add aperture or phased-array parameters when needed.
- Set sweep, uncertainty, and screening-limit options.
- Select Calculate analysis and review all warnings.
- Export the table, report, or shareable calculation link.
Worked engineering example
A 2.437 GHz patch antenna has a 0.12 meter maximum dimension. The transmitter supplies 0.1 watt before losses. The observation point is one meter away.
The calculator determines wavelength and both field boundaries. It then compares one meter against those boundaries. Power density and field strength use delivered power and gain.
The sweep graph shows transitions across distance. Warnings identify questionable approximations. Exported results preserve the selected engineering assumptions.
Example data
| Application | Frequency | Maximum dimension | Typical analysis focus |
|---|---|---|---|
| NFC loop | 13.56 MHz | 0.08 m | Reactive magnetic field |
| Wi-Fi patch | 2.437 GHz | 0.12 m | Boundary and exposure screening |
| Microwave horn | 10 GHz | 0.30 m | Fresnel and phase error |
| Satellite dish | 12 GHz | 1.20 m | Far-field test distance |
| Planar array | 60 GHz | 0.06 m | Scan-dependent boundary |
Assumptions and limitations
- Boundary equations are engineering criteria, not universal physical discontinuities.
- Near-field values are approximate unless a specific validated antenna model applies.
- Nearby conductors, enclosures, ground planes, and people can change fields significantly.
- Strongly lossy media may require complex propagation constants and measured material data.
- Array factors do not replace element-pattern and mutual-coupling analysis.
- Exposure results are screening estimates and require professional verification when safety matters.
Model comparison
| Model | Best use | Near-field behavior | Main limitation |
|---|---|---|---|
| General engineering estimate | Fast screening | Blended 1/r³, 1/r², and 1/r terms | Not geometry exact |
| Short-dipole estimate | Small electric dipoles | Strong electric reactive component | Requires electrically short element |
| Small-loop estimate | Inductive loops and NFC | Strong magnetic reactive component | Requires electrically small loop |
| Far-field approximation | Radiation-zone checks | Only 1/r radiation term | Invalid near antenna |
| Custom scaling | Calibrated measurements | User-adjusted magnitude | Depends on calibration quality |
Frequently asked questions
What is the reactive near field?
It is the region nearest an antenna. Stored electric or magnetic energy can dominate there. Field ratios may differ greatly from free-space impedance.
What is the radiating near field?
It is often called the Fresnel region. Radiation exists, but angular field distribution still changes with distance. Aperture phase variation remains important.
Where does the far field begin?
A common criterion is two times antenna dimension squared divided by wavelength. Other standards use different margins. Select the method matching your engineering procedure.
Why can two boundary methods disagree?
Near-field boundaries are practical criteria. They may target phase error, amplitude uniformity, or measurement accuracy. Different goals produce different distances.
Can far-field power density be used nearby?
It can provide a rough comparison only. Reactive fields and geometry effects may dominate nearby. The calculator warns when this approximation is questionable.
How does material permittivity affect wavelength?
Higher relative permittivity reduces phase velocity and wavelength. Boundary distances then change accordingly. Conductivity can also attenuate and shift fields.
What does the Fresnel number show?
It compares aperture size with wavelength and distance. Larger values indicate stronger near-field diffraction behavior. Smaller values approach far-field conditions.
What creates grating lobes in arrays?
Large element spacing can create additional radiation maxima. Electronic scanning makes the spacing requirement stricter. The calculator provides a simplified warning.
Are exposure results legally compliant?
No. They are engineering screening estimates using user-entered limits. Certified compliance requires applicable standards, calibrated measurements, and qualified review.
Why run uncertainty analysis?
Frequency, distance, gain, and power are never exact. Uncertainty analysis shows plausible variation. It also highlights sensitive inputs requiring better measurement.
When is full-wave simulation necessary?
Use it for complex geometry, nearby objects, strong coupling, lossy media, or precise compliance work. Analytical formulas remain valuable for rapid checks.