engineering

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

2. Earth Station Testing
Mandatory tests
Additional tests measurements could also be done by:
 In addition to the mandatory tests described, transmitting and receiving antenna
patterns including both co-polarized and cross-polarized patterns may also be
measured through transmit sidelobe pattern as demonstrated in Fig. 10:
Fig.10: Test set-up for measurement of transmit sidelobe pattern

3. Earth Station Testing
Mandatory tests
Additional tests
 Initially, the antenna under test (AUT) transmits a low level test carrier usually
15dB below what is defined in the test plan at the test frequency;
 The power level is subsequently increased until the nominal power level
for the test plan is reached;
 The AUT is swept over angular displacements, typically ±15◦ corrected;
 For antennas employing elevation over azimuth mounts, the azimuth angle
needs to be corrected for the elevation angle;
 Corrected azimuth angle ( ) in terms of the azimuth angle from boresight (AZ)
as measured from encoders and the elevation angle (AEL) is given by equation 2:
(2)
𝐴𝑍′
𝐴𝑍′ = 2sin−1
sin(
𝐴𝑍
2). 𝑐𝑜𝑠(𝐴𝐸𝐿

4. Earth Station Testing
Mandatory tests
Additional tests
 In this case, the antenna under test (AUT) receives an unmodulated beacon, or
alternatively an unmodulated carrier transmitted from the payload operations
centre;
 Co-polarized and cross-polarized receive azimuth and elevation sidelobe
patterns are then measured at the AUT site;
 Prior to the commencement of the test, the azimuth and elevation tracking
velocities of the AUT are measured possibly over the full angular displacement
range of the measurement;

5. Earth Station Testing
Line-up tests
 Involves checking the performance of the newly commissioned Earth station vis-
`a-vis other Earth stations it is intended to operate with (the control and
monitoring);
 During these tests, the carrier EIRP is set to provide the desired carrier to-noise
ratio at the receiving end.

6. Earth Station Hardware
Most Earth station hardware can be categorized into one of the three
groups namely:
i. RF equipment
ii. IF equipment
iii. Baseband equipment and terrestrial interface equipment.
RF Equipment
 The RF equipment comprises of up-converters, high power amplifiers (HPA) and
the transmitting antenna in the transmitting channel, and the receiving antenna,
low noise amplifiers (LNA) and down-converters in the receive channel;
 While the output of HPA feeds the transmit antenna; the receive antenna is
connected to the input of the LNA;
 Transmit and receive antenna functions are performed by the same antenna.
 Fig. 11 is the block schematic arrangement of the RF portion of the Earth station
equipment.

7. Earth Station Hardware
RF Equipment
Fig.11: Block diagram of the RF portion of the Earth Station

8. Earth Station Hardware
RF Equipment
 Minimal losses in the waveguide/cable connecting the antenna and the HPA
output or LNA input is achieved by packaging the uplink and down link
equipment separately;
 The uplink equipment mainly comprises of the modulator and the up-converter
and the down-link equipment has down-converter and the demodulator;
 Up-converters and down-converters are frequency translators that convert the IF
used in the modems and baseband equipment to the operating RF frequency
bands (C, Ku and Ka) and vice versa.

9. Earth Station Hardware
IF and Baseband Equipment
 The nature and complexity of baseband equipment in an Earth station is mainly
governed by the range of services offered;
 The architecture of the IF and baseband section depends upon parameters like
the modulation/demodulation scheme, multiple access method and so on;
 For instance, FDMA station (See Fig.12) has one modem for each frequency
resulting in use of a large number of such units. While in TDMA Earth station
(See Fig.13) needs to have only one modem for obvious reasons. However, the
bandwidth requirement of the modem in the case of a TDMA station is much
more than FDMA station;

10. Earth Station Hardware
IF and Baseband Equipment
Fig.12: Block diagram of FDMA digital communication Earth Station

11. Earth Station Hardware
IF and Baseband Equipment
Fig.13: Block diagram of a typical TDMA interactive VSAT terminal

12. Earth Station Hardware
Terrestrial Interface
 Terrestrial interface is that part of the Earth station that connects the Earth station to
the users;
 It is important as bad interface can significantly degrade the quality of service;
 The nature and complexity of the terrestrial interface depends upon the range of
services or functions provided by the Earth station.
 The interface requirement varies from practically no interface in the case of portable
user terminals such as satellite phones to a simple interface in the case of VSAT or TVRO
terminals;
Two Major components of Terrestrial Interface
1) the terrestrial tail: link is needed to connect the main Earth station to one or more
remote user locations with line-of-sight microwave and fibre optic cable being the two
principal options.
2) the interface: Common interfaces needed in satellite links and terrestrial networks
include telephone interface (voice), data transmission interface (data) and television
interface (video).