Using Results to Calculate Antenna Gain

The solar peak power can be used to compute the gain of the antenna. This gain can be monitored over time to determine the stability of the receiver calibration.

For solar calibration, antenna gain can be written as:

G = \frac{4 π \times P_{s}}{F_{s} B_{n λ^{2}}}

G: Antenna gain (dimensionless) on beam axis.
P_s: Received sun peak power (dBm) (fTargetPowerSun)
F_s: Solar flux density (Wm^-2Hz^-1)
B_n: Noise bandwidth (Hz) (fReceiverBandwidth)
λ²: Transmit wavelength (m)

The calculated antenna gain must be corrected to determine the true gain of the system. Solar flux measurements include all polarizations so 3dB must be added to the gain as half the power is lost due to receiving in a single polarization. An additional beam filling correction must be made because the sun radio diameter (0.56 ... 0.58⁰) is considerably smaller than most antenna's 3 dB beam width. A beam filling correction for Gaussian main beams is given below:

K (d B) = 20 \log (1 + 0.18 {(\frac{U_{s}}{U_{a}})}^{2})

For example, a 1.0⁰ beam has e a filling correction of 0.49 dB. Experience has shown about #mnplus#0.5 dB fluctuation in true antenna gain due to solar flux and receiver measurement uncertainties.

Observations of solar flux density (F_s) are available publicly on the internet for several frequencies, locations, and times of day. Suggested sites are the Solar Environment Center (SEC), National Oceanic and Atmospheric Administration in Boulder, Colorado; the Dominion Radio Astrophysical Observatory at Penticton, British Columbia, and the IPS Radio and Space Services Observatory in Australia.

To read the suncal results file into the C++ memory structure, use the LoadSuncalResults() function.