Lecture Note 4 Earth Station Testing-Jan 2022.pptx

earth station

1. A HMED , Wasiu A kande ( Instructor ) , Dr. EARTH STATION TECHNOLOGY (SCM 704) ARCSSTE-E’s PGD Program 2021/2022

2. Earth Station Testing T he 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: Unit and Subsystem Level Testing ( tested for their electrical , mechanical and environmental specifications ); System Level Testing ( acceptance tests ). Further divided into: Mandatory tests Additional tests

3. Earth Station Testing Mandatory tests Mandatory tests include measurements of: Transmit C ross-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 ) Receiver figure-of-merit; The underlying principle for measurement of receiver figure-of-merit (G/T) is as follows : t he downlink carrier to noise spectral density (C/No); 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 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 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; A tmospheric 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 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