Design a Repeater for Digital Rf Signal

Topics: Transistor, Radio spectrum, Digital television Pages: 32 (9527 words) Published: November 29, 2012
Repeaters for digital TV broadcasting can use either analogue or digital techniques. The purpose of using repeater is to boost signals into areas of weak coverage in any radio communication system. However wave interference means the repeater usually requires a frequency shift for analogue modulated signal. For digitally modulated signal it may be possible to use same frequency. This paper investigated and designed a RF repeater which will improve the inter symbol interference by incorporating delay between received and transmit signal. This project also reviewed the basics of current Digital Video Broadcasting-Terrestrial (DVB-T) techniques and selected it as a suitable choice for lab experiment. The practical side of this project is to design and build a repeater incorporating suitable electrical delay.

1.0 Introduction4
1.1 Background:4
1.2Aim of this project6
1.3Project objectives6
1.3 Project deliverable7
2.0 Problem analysis8
2.1 Repeater8
2.1.1 Analogue repeaters9
2.1.2 Digital repeaters10
2.2 Inter symbol interference13
2.3 Multipath propagation15
2.3.1 Multipath fading15
2.4 The TV channels16
2.5 Transmission cable18
2.6 Signal Amplifiers20
2.7 Transmission delay (Coaxial cable)21
3.0 Possible solution24
3.1 RF amplifier25
3.1.1 The Transistor Amplifier26
3.1.2 Ultra High Frequency Transistor Array (HFA)29
3.1.3 Surface mounts technology:32
3.1.4 Surface Mount Monolithic Amplifier:32
3.1.5 Loft box: 8 way home distribution unit34
3.2.6 Maxview signal booster35
3.2.7 Antenna:36
4.0 Design37
4.1 Circuit design37
4.2 PCB design38
5.0 Implementation40
5.1 Implementation with HFA312740
5.2 Implementation with MAV-11SM amplifier41
6.0 Test result42
6.1 Laboratory test result42
6.2 Field test result44
7.0 Result Discussion46
8.0 Conclusion48
Future work:49
Works Cited50

Figure List
Figure 1System block diagram6
Figure 2 Passive and Active repeater block diagram7
Figure 3 Analog repeater8
Figure 4 Digital repeater9
Figure 5 Channel management for digital repeater10
Figure 6 Channel management for analogue repeater10
Figure 7 Broadcast in valley with digital repeaters11
Figure 8 101101 transmitted data12
Figure 9 Received data12
Figure 10 Transmitted data vs. Received data13
Figure 11 Multipath propagation14
Figure 12 Cable loss in dB  (Antenna basics, 2008)18
Figure 13 Linear change phase vs frequency22
Figure 14 The basic transistor amplifier26
Figure 15 HFA3127 transistor array30
Figure 16 MAV-11SM amplifier31
Figure 17 Suggested PCB layout with MAV-11SM33
Figure 18 Loft box home distributor33
Figure 19 Maxview signal booster35
Figure 20 Antenna used for this project35
Figure 21 Interference between relay signal and main transmitted signal36
Figure 22 ISIS schematic of circuit design37
Figure 23 PCB design according to the datasheet in ARES37
Figure 24 3D view for PCB38
Figure 25 Circuit with HFA3127 amplifier39
Figure 26 MAV-11SM amplifier circuit board40
Figure 27 HFA3127 gain with soldering error41
Figure 28 HFA3127 amplifier gain41
Figure 29 One MAV-11SM amplifier gain42
Figure 30 Two MAV-11SM amplifier circuits give more gain42
Figure 31 Three amplifiers together was the maximum gain43
Figure 32 Low quality picture with normal antenna43
Figure 33 Picture with repeater connected antenna44
Figure 34 Rebroadcasting connection44

1.0 Introduction

1.1 Background:

Digital Video Broadcasting (DVB) is being adopted as the standard for digital television in many countries. The DVB standard offers many advantages over the previous analogue standards and has enabled television to make a major step forwards in terms of its technology. Digital Video Broadcasting, DVB is now one of the success stories of modern broadcasting. The take up has been enormous and it...
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