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Re: [Discuss-gnuradio] ask : USRP Mode-S/ADS-B project

From: Eric A. Cottrell
Subject: Re: [Discuss-gnuradio] ask : USRP Mode-S/ADS-B project
Date: Sat, 03 May 2008 12:23:05 -0400
User-agent: Thunderbird (X11/20080226)

Bino Oetomo wrote:
Eric A. Cottrell wrote:

The code is still a work-in-progress. The hardware used, the USRP and DBSRX board, costs as much or slightly more than the RadarBox or SBS-1. It might be possible to do a simplified hardware board but I am not a hardware engineer. Mode-S/ADS-B has a 1 Megabit symbol rate which is way above what a sound card can do.

Nice to hear that it's still in active stage.

Obout the Receiver cost : I understand that, still ...
++ with this we can do some OpenSource and flexible solution
++ Hope ettus will consider to produce 1 port board. I reallize that the price cut will not that big ... since the core component (i.e : FPGA) still the same ..... but there is a "cut" anyway :)
It would be likely be in the 500 dollar range as it would be similar to a RF Space SDR-IQ. It may be possible to optimize the design further so it will only decode Mode-S but that would preclude decoding the future UAT transmissions. The FAA plans to do TIS-B over UAT. TIS-B would provide information on Mode S and Mode A/C aircraft.

There are some interesting hardware available or soon to be available that could reduce the coast. One interesting chip is the TI OMAP series that combines an processor and DSP on one chip. It may be possible to use one of the on-board devices to digitize the waveform but a RF front end is still needed.

About Symbol rate : hmmm what about DVB rx card .... i'm not sure if we can customize their demodulation to handling mode-s/ads-b ... but they capable in handling up to 45 megabit/sec symbolrate , and capable of handling freq around 1 Ghz cmiiw.
Arrrggh ... looks like we need to do firmware work (too many work).

Thanks for your enlightment

DVB receivers cover the same frequency range but are designed for larger signal levels from the LNB. DVB uses QPSK. Newer receivers have front end chips that take the RF and output the digital mpeg transport stream. The DVB Rx board for the USRP uses a DVB tuner chip but it is preceded by an amplifier. Some Video Cards do have an extra ADC that may be useful but you need more components for a complete system.

Another avenue is alternate firmware for the SBS-1 or Radarbox much like the Rockbox project for MP3 players. I suspect that both units use soft microprocessors in the FPGAs.

I try to keep track of hardware as does several others so if there is a lower cost solution it will be found.

73 Eric

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