by

• Charles Brain G4GUO G4GUO@ARRL.NET

2012 BATC CONVENTION

DATV-Express

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DATV-Express

The main DATV-Express team members

• Ken Konechy - W6HHC PGM Manager• Art Towslee - WA8RMC Hardware• Tom Gould - WB6P PCB Layout• Charles Brain - G4GUO Software

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DATV-Express

Goals of the Project

• Significantly reduce the price of Digital-ATV transmitters• Provide an open platform for future DATV development• Help educate the community and ourselves about new technologies.• Get more DATV stations on-air • Encourage more people to get licensed• By product will be a Software Defined Transmitter for the 23 cms band with a B/W of up to 8 MHz.

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DATV-Express

It all started when I bought a USRP2

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DATV-Express

Overview of DATV-Express System

System Block Diagram for DATV-Express DATV Transmitter

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DATV-ExpressOverview of Hardware Board USB2 Interface Cypress CY7C68013A• FPGA Altera EP2C8T144CN• DAC Analogue Devices AD9767ASTZ• Clocks• PLL/modulator for 1.3 GHz ADRF6750A• Buffer amplifier GVA-84+ ~20 mW• Optional symbol rate generator Si570• DC-DC power supplies allows single 12V input

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DATV-ExpressOverview of Hardware Board – cont’d

Block Diagram for DATV-Express Hardware Board

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DATV-Express

First prototype

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DATV-Express

Overview of PC Software

• Operating System - Linux 32/64-bit then Win32• Loads FX2 firmware (Control Transfer)• Loads FPGA firmware (EP1)• Controls 1.3 GHz PLL (EP1)• Controls symbol rate generator (EP1)• I/Q offset calibration (EP1)• Provides GUI

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DATV-ExpressOverview of PC Software – cont’d

• Take program/transport stream from capture device• Converts to a transport stream with correct PIDS• Adds SI Table information• Adds FEC • Does interleaving• Keeps symbol rate constant, no overruns or under runs by adding Null transport packets• Generates either IQ symbols or a bitstream• Talks to exciter board via USB interface (EP2)

DATV-ExpressGUI Screen-shot (current)

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DATV-ExpressOverview of Hardware Board SoftwareFX2 code (USB chip has 8051) C/ASM• Programs FPGA• Manages USB FIFO interface with FPGA• I2C interface with 1.3 GHz PLL• I2C interface with symbol rate generator• I2C interface to FPGA • General Housekeeping

FPGA code, Verilog, Altera Quartus II• Interpolates symbols to final sample rate• Channel filter• Writes to DAC

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DATV-ExpressDATV-Express Minimum System Specs• DVB-S protocol• QPSK modulation (will allow other modulations)• Frequency Range: 950–1575 MHz (allowed by ADRF6750 chip)

– 1240–1300 MHz (allowed in USA)– 1240–1325 MHz (allowed in Europe)

• Symbol-Rate:– Adjustable: 1 MSymb/sec -to- 5 MSymb/sec

• Forward Error Correction is selectable• RF output ~ 20 mW buffered (SMA connector)• Video Capture card allows for NTSC or PAL• Initially designed for one video stream• Operating system – first Linux-32/64 then Win32

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DATV-ExpressCurrent Project Status

• First prototype PCB built• Linux GUI, DVB-S and DVB-T code working

• Basic FPGA code working

• Version 2 PCB being laid out

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DATV-ExpressProof-of-Progress – 1st DVB-S Transmission

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DATV-ExpressDVB-S 1.2 GHz spectrum

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DATV-ExpressQPSK constellations (with noise)

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DATV-ExpressDVB-S2 32APSK Constellation

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DATV-Express6 MHz DVB-T spectrum with I/Q balance problem & filter passband ripple

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DATV-Express1.3 GHz 7 MHz DVB-T on a PC with a Realtek USB Dongle and DVBDream

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DATV-ExpressWhat about DVB-T, DVB-S2, 8VSB etc?

• “Yes, they are possible....”• “But, the team is only committed to DVB-S”• We already have experimental support for

Firewire/DV video input, text overlays, testcards, FFMPEG transcoding, 1080i HD and DVB-T.

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DATV-ExpressWhat about RaspberryPi ?“Yes, it should be possible....”• Pi has hardware H.264 encoding / decoding and will have a

5 Megapixel camera soon. Has USB2 interface. No on board sound in.

• Code needed on Pi to convert raw H.264 data into a valid DVB transport stream and to load FPGA code on Express board. Can probably re-use some code already written.

• Need to wait for Pi foundation to write all the required hardware libraries to support camera.

• Express, will have to move FEC coding to FPGA so board supports transport stream. Only space for DVB-S

DATV-Express

Hope to have final production PCB ready around Christmas time

Intend to provide incremental software releases during the life of the board.

Add DVB-S2 and maybe DVB-T2 Depends on demand but maybe a matching receiver

optimized for < 2 Msymbols/s?

Conclusion and Plans

DATV-Express

Useful Links:

My blog http://www.g4guo.blogspot.co.uk/ Follow me on Twitter @G4GUO

DATV-Express

Thank-you all!