Analyze antenna gain and efficiency with trusted formulas. Review dBi conversions, mismatch loss, aperture estimates. Make cleaner RF decisions from one focused calculator today.
| Case | Gain (dBi) | Directivity (dBi) | Efficiency (%) | VSWR | Realized Gain (dBi) |
|---|---|---|---|---|---|
| Patch antenna | 8.00 | 10.00 | 63.10 | 1.40 | 7.63 |
| Yagi array | 12.50 | 14.00 | 70.79 | 1.30 | 12.25 |
| Dish feed system | 19.20 | 21.00 | 66.07 | 1.70 | 18.24 |
1) Gain and directivity relation: G = η × D
2) Efficiency from gain and directivity: η = G / D
3) Convert dBi to linear: Linear = 10^(dBi/10)
4) Convert linear to dBi: dBi = 10 × log10(Linear)
5) Reflection coefficient from VSWR: |Γ| = (VSWR - 1) / (VSWR + 1)
6) Mismatch efficiency: ηm = 1 - |Γ|²
7) Feeder efficiency: ηf = 10^(-Loss/10)
8) Realized gain: Gr = G × ηm × ηf
9) Effective aperture: Ae = (G × λ²) / (4π)
Antenna gain and antenna efficiency are tightly connected. Engineers often know one value and need the other. This calculator solves that problem fast. It also adds mismatch loss, feeder loss, and effective aperture. Those extra outputs make the result more useful for design review and field checks.
Directivity shows how strongly an antenna concentrates energy in one direction. Gain goes one step further. It includes radiation efficiency. A high directivity antenna can still show lower gain if conductor loss, dielectric loss, or surface wave loss reduces useful radiation. That is why the equation G = η × D matters.
RF work often switches between linear values and decibels. Linear form is best for multiplying efficiency, directivity, mismatch, and feeder effects. dBi is easier for specifications and reports. This calculator handles both forms. It converts values automatically and keeps the final numbers consistent.
Many datasheets list gain, but a real system sees more loss. Poor impedance match reflects part of the power. Feed line loss reduces delivered energy before radiation even starts. Realized gain includes both effects. That makes it a stronger metric when comparing installed antenna performance.
Effective aperture links gain to receive capability. At the same frequency, more gain means larger effective aperture. That matters in link budgets, radar studies, and satellite ground systems. It also helps explain why compact antennas usually trade size, bandwidth, and efficiency against one another.
Use this page during concept design, test validation, or troubleshooting. Enter known values, compare the graph, and review the realized result. If the efficiency exceeds one hundred percent, the inputs likely conflict. That warning can catch specification errors before they reach procurement or production.
Directivity measures pattern concentration only. Gain includes that concentration plus radiation efficiency. If efficiency drops, gain drops even when directivity stays the same.
No. Values above 100 percent usually mean the input gain or directivity data are inconsistent, rounded too aggressively, or referenced under different measurement conditions.
VSWR estimates mismatch loss. A poor match reflects some source power back toward the transmitter. That reduces realized gain and overall system efficiency.
Realized gain is gain after mismatch and feeder effects are included. It is often more practical for installed systems than ideal gain alone.
Effective aperture depends on wavelength. Longer wavelengths change the capture area linked to a given gain. That is why frequency is needed for aperture output.
Use dBi for reading datasheets and reporting results. Use linear values for multiplication inside formulas. This calculator converts both automatically.
Feeder loss does not change the physical antenna properties. It reduces delivered power in the system path, so realized gain at the end of the line becomes lower.
Use it for RF design checks, test report verification, link budget preparation, and troubleshooting when gain, directivity, efficiency, or mismatch values must be compared quickly.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.