Wiki » History » Version 37

GOMEZ, Ramon, 12/12/2015 06:02 PM

1 1 GOMEZ, Ramon
{{toc}}
2 1 GOMEZ, Ramon
3 35 GOMEZ, Ramon
h1. 1. Introduction
4 35 GOMEZ, Ramon
5 4 GOMEZ, Ramon
Earth stations are based on an indoor/outdoor unit architecture. The outdoor unit comprises antennas and the RF frontend (amplifier and up/down converter). The indoor unit includes the receiver, modem and network/application appliances. On typical consumer systems, the outdoor and indoor units are connected by means of a 75-ohm coaxial cable. The cable conveys the intermediate frequency (typically L band) signal between the indoor/outdoor units. 
6 6 GOMEZ, Ramon
7 28 GOMEZ, Ramon
This approach, while being cost effective, is not optimal from a signal quality standpoint and might severely impair the end-to-end link budget. For example, typical attenuation values for a coaxial cable at a frequency of 1 GHz are in the order of 15 dB/100m.
8 1 GOMEZ, Ramon
9 5 GOMEZ, Ramon
The objective of this project is to test and evaluate a system that makes possible to convert the L-band RF signal from/to optical and use an optical fibre (up to 10 km) as primary interconnection media.  The signal is converted from optical back to RF in the indoor unit. As such, it is directed to DTH (Direct-To-Home) TV systems.
10 5 GOMEZ, Ramon
11 5 GOMEZ, Ramon
12 4 GOMEZ, Ramon
h1. 2. Elements and technical features  
13 4 GOMEZ, Ramon
14 28 GOMEZ, Ramon
As discussed in the introduction, an optic system will be implemented throughout this project trying to improve and replace and the classical 75-ohm coaxial cable. In order to do so the schema below represents the elements used and the configurations adopted:  
15 1 GOMEZ, Ramon
16 27 GOMEZ, Ramon
!schema.jpg!
17 27 GOMEZ, Ramon
18 28 GOMEZ, Ramon
As it has been presented before, the project consist of an indoor and outdoor parts
19 28 GOMEZ, Ramon
* Outdoor: consists of the L-band reception antenna, the coaxial cable relying the antenna and the modulator transmitter (allows to convert from L-band to optic frequencies) and the 30m of Monomode fiber optic, FO. 
20 28 GOMEZ, Ramon
* Indoor part: consists of the receiver L-band/optic demodulator and the coaxial cable to rely the demodulator with the TV. 
21 28 GOMEZ, Ramon
22 28 GOMEZ, Ramon
23 28 GOMEZ, Ramon
///////////////////////////Write here technical details of each systems/////////////////////////
24 27 GOMEZ, Ramon
25 27 GOMEZ, Ramon
_Remark: As the aim of the project is to characterise the fiber system we have substitute the TV by an spectrum analyser in order to evaluate the performances._    
26 4 GOMEZ, Ramon
27 4 GOMEZ, Ramon
h1. 3. Measures
28 4 GOMEZ, Ramon
29 6 GOMEZ, Ramon
h2. 3.1 Linearity
30 6 GOMEZ, Ramon
31 6 GOMEZ, Ramon
h2. 3.2 Intermodulation
32 6 GOMEZ, Ramon
33 6 GOMEZ, Ramon
h2. 3.3 Phase/Noise
34 4 GOMEZ, Ramon
35 6 GOMEZ, Ramon
h1. 4. Results
36 1 GOMEZ, Ramon
37 26 GOMEZ, Ramon
h1. 5. Application
38 7 GOMEZ, Ramon
39 7 GOMEZ, Ramon
This section explains how the Outdoor system has been installed and the results obtained measuring a real TV signal from a Satellite. 
40 7 GOMEZ, Ramon
41 26 GOMEZ, Ramon
h2. 5.1 Preparation
42 7 GOMEZ, Ramon
43 7 GOMEZ, Ramon
The optical transmitter has been put in an hermetic box.
44 7 GOMEZ, Ramon
45 7 GOMEZ, Ramon
Its interface consists of :
46 7 GOMEZ, Ramon
47 7 GOMEZ, Ramon
* The power supply plug to be connected to the mains ;
48 7 GOMEZ, Ramon
* The optical fiber harness (2 fibers) : only the red fiber is actually connected to optical transmitter ; the black fiber is not used, it will enable to have a b ;
49 7 GOMEZ, Ramon
* The type F coaxial cable to connect the Antenna Low Noise Block, LNB, to optical transmitter.
50 7 GOMEZ, Ramon
51 7 GOMEZ, Ramon
Optical transmitter is set to :
52 1 GOMEZ, Ramon
53 1 GOMEZ, Ramon
* To supply 18 V to LNB, which selects Horizontale polarization ;
54 7 GOMEZ, Ramon
* To provide 0 kHz tone to LNB, which set its Local Oscillator to 9.75 GHz to transpose lower Ku Band from  10.7 to 11.7 GHz into IF Band.
55 7 GOMEZ, Ramon
* This hermetic box has been mounted on Antenna mast. This Antenna is pointing to Astra 1KR/1L/1M/1N colocalized satellites on 19.2° East.
56 7 GOMEZ, Ramon
57 26 GOMEZ, Ramon
h2. 5.2 Trials
58 7 GOMEZ, Ramon
59 26 GOMEZ, Ramon
h3. 5.2.1 Inter Frequency Spectrum with Optical Link
60 1 GOMEZ, Ramon
61 14 GOMEZ, Ramon
RF output from Optical receiver has been analyzed with Rohde & Schwartz FSV spectrum analyzer :
62 14 GOMEZ, Ramon
63 1 GOMEZ, Ramon
!rsz_1combine_images.png!
64 14 GOMEZ, Ramon
_IF Band, 1 Channel (with Optical Link)_
65 1 GOMEZ, Ramon
66 14 GOMEZ, Ramon
It is possible to distinguish several channels within the Inter Frequency, IF, band. There is a zoom on left side. The 3 dB channel bandwdith is 22 MHz.
67 13 GOMEZ, Ramon
The power is about -32 dBm for the channel centered around 1141 MHz.
68 1 GOMEZ, Ramon
69 9 GOMEZ, Ramon
!rsz_tv_channel.png!
70 14 GOMEZ, Ramon
_TV channel at 1141 MHz_
71 1 GOMEZ, Ramon
72 26 GOMEZ, Ramon
h3. 5.2.2 Link Quality with Optical link
73 1 GOMEZ, Ramon
74 14 GOMEZ, Ramon
First, optical link performance enables to have a good TV quality (for example, Eins Plus on 10744H). More deeply, physical link quality has been assessed with the information provided by IPRICOT SCB router.
75 20 GOMEZ, Ramon
This data has been compared with data from website like [www.lingsat.com] :
76 15 GOMEZ, Ramon
77 1 GOMEZ, Ramon
!table_channels.jpg!
78 1 GOMEZ, Ramon
79 21 GOMEZ, Ramon
!rsz_ipr_sc.png!
80 22 GOMEZ, Ramon
Physical link parameter at 10744 MHz
81 23 GOMEZ, Ramon
82 25 GOMEZ, Ramon
!rsz_ipr_sc2.png!
83 22 GOMEZ, Ramon
Physical link parameter at 11244 MHz
84 26 GOMEZ, Ramon
85 26 GOMEZ, Ramon
h1. 6. Conclusions