Reflector Antenna & Feed Basics

1. General information

I made a summary about gain, efficiencies, beam factor, HPBW, beam efficiency, Tspillover, Tsky of parabolic reflector antennas.

Download of Reflector Antenna Basics

Here is a summary about feed pattern, dish illumination and resulting antenna beam pattern (from ideal to real).

Download of Feed pattern Basics




An offset reflector antenna is more complex than a prime-focus but has some advantages (higher gain, reduced spillover).

2. Useful formulas about prime focus and offset antennas

I created a spreadsheet to determine most relevant (mechanical) parameters of an offset and prime focus dish.
Download of Reflector Antenna Parameters

Legon's equation: for flat surface offset dish and position of maximum dish depth is known
"Calculation_of_the_Focal_Length_of_an_Offset_Satellite_Dish_Antenna"

Another more general equation: for flat/bended surface and known depth in dish center
version 1.1 (with addendum), October 2021, registration needed:
"a33-calculation-of-the-focal-length-of-an-offset-satellite-dish-antenna v1.1"
version 1.0, July 2020, no registration needed:
"a33-calculation-of-the-focal-length-of-an-offset-satellite-dish-antenna v1.0"

More offset antanna equations:




I made a calc tool for prime-focus and offset parabolic reflector antennas. This tool can also handle bended surface/rim offset antenna. It calculates efficiencies, gain and G/T.

3. Useful feeds for offset antennas

Design guide for dual mode horns and lambda/4 transition plate.
See "feed simulations", chapter 3.

4. Reflector antenna efficiencies

Ohmic efficiency:

Illumination efficiency:



Spillover efficiency:



Polarization efficiency:



Phase efficiency:



Surface efficiency (Ruze):

Blocking efficiency:

Axial focus efficiency:

5. References

¹ Paul Wade W1GHZ, "The W1GHZ Online Microwave Antenna Book"
² John D. Kraus, 1988, "Antennas for all applications" Second edition
³ John D. Kraus, 1986, "Radio Astronomy" Third edition
⁴ Jacob W.M. Baars, 2007, "The paraboloidal reflector antenna in radio astronomy and communication"
⁵ Samuel Silver, 1949, "Microwave antenna theory and design" First edition
⁶ Thomas A. Milligan, 2005, "Modern antenna design" Second edition
⁷ Constantine A. Balanis, 2005, "Antenna theory" Third edition
⁸ Thomas L. Wilson, Kristen Rohlfs, Susanne Hüttemeister, 2009, "Tools of radio astronomy" Fifth edition
⁹ Joachim Köppen, DF3GJ, https://portia.astrophysik.uni-kiel.de/~koeppen/jsindex.html#RADIOASTRO
¹⁰ Dimitry Fedorov, UA3ARV, DUBUS 3/2016, "Solar flux and temperature at millimeter wavelengths"
¹¹ W. Stutzman, M. Terada, "IEEE Antennas and Propagation Magazine, Vol.35, No.6, December 1993"
¹² A. Cornejo, S. Landeros-Ayala, R.M. Rodriguez-Osorio, J.M. Matias, 2018, "A method for designing an offset-parabolic-reflector antenna for a ultra-high throughput satellite"
¹³ Per-Simon Kildal, "Foundations of antenna engineering"