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


prime focus geometry

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

offset geometry



2. Useful formulas about prime focus and offset antennas


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:

offset geometry


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.

offset geometry



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:

illumination efficiency

Spillover efficiency:

spillover efficiency

Polarization efficiency:

polarization efficiency

Phase 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"