1. AHMED, Wasiu Akande (Instructor), Dr.
EARTH STATION TECHNOLOGY
(SCM 704)
ARCSSTE-E’s PGD Program 2021/2022
2. Earth Station Testing
The Earth station equipment should not only meet the specified
requirements of the intended Earth station but also to ensure that the
Earth station would not cause any problem;
This is achieved by performing different levels of testing as stated
below:
1. Unit and Subsystem Level Testing (tested for their electrical, mechanical and
environmental specifications);
2. System Level Testing (acceptance tests). Further divided into:
i. Mandatory tests
ii. Additional tests
3. Earth Station Testing
Mandatory tests
Mandatory tests include measurements of:
i. Transmit Cross-polarization Isolation Measurement (linearly as well as circularly
polarized antennas);
Fig.1: Schematic arrangement of transmit
cross-polarization isolation measurement
4. Earth Station Testing
Mandatory tests
Transmit Cross-polarization Isolation Measurement is done to guarantee that the
power level of the cross-polarized component is either nil or within the
tolerance limit so as not to cause any significant interference to other users;
This test is typically performed only on-axis (x, y or azimuth, elevation)
ii. Receiver figure-of-merit;
The underlying principle for measurement of receiver figure-of-merit (G/T) is as
follows:
a) the downlink carrier to noise spectral density (C/No);
b) the corresponding satellite EIRP also measured.
Note: Though the method is simple; it is prone to in accuracies due to its
susceptibility to variations the in atmospheric loss. See Fig. 9 for detail
5. Earth Station Testing
Mandatory tests
ii. Receiver figure-of-merit;
Fig.9: Schematic arrangement of test set-up for measurement of receiver G/T
6. Earth Station Testing
Mandatory tests
The antenna under test (AUT) measures the received power level of either an
unmodulated beacon, or a test carrier;
The downlink EIRP of the unmodulated beacon or the test carrier is also
measured;
The receive system noise contribution is then measured by steering the antenna
off the spacecraft and measuring the noise floor;
The difference between the two measurements is the downlink (C+N)/N ratio
7. Earth Station Testing
Mandatory tests
iii. EIRP stability;
The quality of service provided by the system is dependent on the stability of
EIRP;
Particularly in the case of high usage transponders and high power uplinks;
Atmospheric effects also contribute to power flux density (PFD) variations at the
satellite;
The allowable EIRP stability figure should be such that the PFD variations caused
by EIRP instability and atmospheric effects together are within allowable PFD
variations at the satellite;
The EIRP stability of a station transmitting digital services should be better than
± 0.5 dB.
8. Earth Station Testing
Mandatory tests
iv. Spectral shape
The spectral shape of the modulated carrier is initially measured during
carrier line-up testing and is also measured subsequently on a regular basis;
Though there are no specific measurements to be made by the users; it is
important for the users to note that control on spectral shape and even the
bandwidth is required to avoid undesired interference to other system users.
