SATELLITE ANTENNA TEMPERATURE
AND
EARTH STATION G/T CALCULATION PROGRAMS
J.M.FOURQUET
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FEATURES AND CAPABILITIES OF THE ANTENNA TEMPERATURE
PROGRAMS
1 - DOMAIN OF APPLICATIONS.
The purpose of this software package is to compute as accurately as possible the antenna system
temperatures for use in the receive side of system link budgets. It also includes the derivation of G/T
for Earth Stations.
The software is for use by communications system engineers for general or particular trade off studies
before going into detailed more complex link performance calculations. It is also an efficient system
support for the definition of the hardware involved in the detailed subsequent and more complex link
performance calculations.
Three classical satellite antenna types are covered in the software package:
- directive antenna: dish, array, horn etc...used for many satellite communication functions
- toroidal pattern antenna: generally used for TM, TC, emergency or normal functions on 3axis or spinning satellites
- omnidirectional antenna.
The directive antenna type has also been used to develop a more complex model for the earth station
case. It includes all the effects due to clear weather atmospheric propagation and ground reflections at
various elevation angles.
For the four antenna types the frequency range is from 100 MHz to 100 GHz.
The sun and the moon can be positioned, when selected, anywhere in the antenna pattern. Adjustable
graphical plots help to define such positions.
All four packages are built in the same way:
- one main spread sheet with all system parameters available for trade off
- one close up graph (around the main beam)
- one extended graph (wide pattern)
- one macro function for the gain calculation
- one macro function for the temperature calculation
2 - WHY YOU SHOULD USE THE ANTENNA TEMPERATURE PROGRAMS ?
- because you want to design RF, telemetry, command, ranging or communications links with
an optimum margin aportionment, and because you objectively want to control these margins at
system level
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- because you want to evaluate the sensitivity of your system performance objectives against
the variations of the main link parameters before freezing a specification or a hardware configuration
- because the antenna temperature seen by a receiving front end (and the G/T for an Earth
Station) is one of these sensitive link parameters, and because it is not easy to properly handle double
integral calculations for temperature integration over 4 steradians. Hence, usually such system
iterations are cumbersome, approximate and prone to errors
- because you want to quickly and accurately run these calculations on your PC with all sytem
trade off capabilities at hand
- because you want to use the powerful EXCEL 4 or 5 spread sheets (or LOTUS) for quick
assessment and review within your team.
3 - TYPICAL EXAMPLES.
3-1- UP LINK BUDGETS.
- aim at minimum up link EIRP for minimum interference constraints and to reduce HPA
costs
- aim at consistent maximum affordable satellite G/T. G is determined from the link
requirements and T remains as an essential performance parameter, like for instance in the mobile
communications up links, always power limited, from the mobile to the satellite
3-2- DOWN LINK BUDGETS.
- aim at optimum satellite EIRP and Earth Station or user G/T. The receive system
temperature quickly appears as an important trade off parameter
- consider trends for smaller, cheaper and transportable/mobile Earth Stations. They require
relatively small diameters, hence larger 3 dB beam apertures. As a consequence, more noise is
captured from the neighboring environment (ground reflection effects, atmospheric attenuation effects
...) particularly at low elevation angles.
3-3- SAMPLE ANTENNA PATTERNS.
Attached are some examples of antenna patterns used in the calculations. All patterns are integrated
over 4 steradians, with limit conditions determined by the user.
4 - CONFIGURATION REQUIRED.
The software package will run on IBM PC compatible computers using 386 or 486 processors and the
Microsoft Windows Version 3-1. EXCEL versions 4 or 5 are required. LOTUS/EXCEL conversions
capabilities normaly exist within either system, LOTUS or EXCEL.
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5 - PRICE.
The package includes one disk ( 3 1/2 " , 4 programs), with a comprehensive user's brochure and
detailed examples for each program.
In particular, the calculation method is provided with useful antenna definitions and formulas.
Total price, including shipping: US $ 595.00
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