antenna_gain
Validate antenna gain claims against physical limits; compute aperture gain, beamwidth, and far-field distance from size and frequency. Use it to check if a quoted gain is physically possible.
Instructions
Calculate antenna aperture gain limits, beamwidth, far-field distance; validate gain claims.
For a circular aperture of diameter D (or an aperture of area A, converted to the equivalent circular diameter D = sqrt(4A/pi)) computes the planar-aperture directivity D_0 = 4piA/lambda^2 = (piD/lambda)^2 (aperture efficiency eta = 1), Harrington's bound D_max = (ka)^2 + 2ka (k = 2pi/lambda, a = D/2) for any antenna enclosed in a sphere of diameter D, the hard physical gain limit max(D_0, D_max) (numerically D_max; equal to D_0 to within 0.1 dB for D >> lambda, but several dB higher for electrically small antennas D < lambda, e.g. a 2.15 dBi dipole in a 0.1 m footprint at 900 MHz is valid although D_0 = -0.5 dBi), and the typical gain G = etaD_0 at the given efficiency (default eta = 0.55, parabolic dish). The limiting_bound field reports 'harrington' for D < lambda and 'aperture' for D >= lambda. Also returns the effective aperture A_e = etaA, a half-power beamwidth estimate (HPBW ~ 70lambda/D degrees for a tapered reflector; 58.4lambda/D for a uniformly illuminated circular aperture) and the far-field (Fraunhofer) distance 2*D^2/lambda.
If claimed_gain_dbi is given it is validated: a claim above the physical limit is rejected as a physics violation; a claim between the typical gain and the physical limit is accepted with a warning and the implied planar-aperture efficiency eta = G_claim / D_0 is reported.
Use this tool when you need to:
Check whether a quoted antenna gain is consistent with its size and frequency
Estimate the gain, beamwidth or effective aperture of a dish of known diameter
Find the minimum far-field range for antenna measurements or Friis validity
Size an antenna for a required gain at a given frequency
Returns a PhysicalViolationError dict if any input violates physics or the claimed gain exceeds the aperture limit.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| diameter_m | No | Circular aperture diameter in meters. Provide this OR aperture_area_m2. | |
| frequency_hz | Yes | Operating frequency in Hz (must be > 0) | |
| aperture_area_m2 | No | Physical aperture area in m^2. Provide this OR diameter_m. | |
| claimed_gain_dbi | No | Optional antenna gain claim to validate in dBi | |
| aperture_efficiency | No | Efficiency for the typical gain / warning threshold (default: 0.55 for a parabolic dish; the hard limit is max(eta = 1 aperture value, Harrington bound)) |
Output Schema
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||