earth station

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.

9. THANKS FOR YOUR TIME