# Source generator for Satellite Tuner input

I need to design a source generator for a TV factory. They want to automatize the functional tests by applying a test module to the TV's at the end of the production line. All the peripherals of the TV (USB HDMI Satellite Terrestrial etc) will be plugged into the test module and will be monitored if the TV operates fully functional.

There will be 500 TV's on the line tested simultaneously so the module has to be cost effective. So I will use Raspberry pi module for USB and HDMI tests but for satellite and terrestrial I am having trouble to find a solution.

I was thinking of using this type of solution for the satellite and terrestrial source input:

Can I use this DAC&Modulator structure to steam a video over satellite cable? For example, I want to send the video in the settings below:

If I convert a video to .ts (transport stream) format and directly feed into the DAC's input will I be able to see the video on TV? Lets say I will send the video data in 30MB/s into the DAC's input (to satisfy 30MS/s symbol rate) and set the Local Oscillator frequency to 1450-30=1420 MHz I think I will be satisfying the RF requirements. However, I still don't know how to set coding rate to 9/10 and to set constellation to 8PSK. I need help from experienced engineers in satellite commnication.

• Sounds like this is a job for a consultant that knows about this technology. You can choose to either team up with someone that can actually help you do this, do a lot of research and reading till you can do this yourself or just pass this project onto someone else. This question is way too broad for the format of this site and as such I am voting to close this for that reason. – Michael Karas Mar 17 at 10:41

## 1 Answer

So, what you're proposing is that for the satellite and terrestrial signal testing you build your own signal source – which is fine.

That's what we call Software Defined Radio (SDR) and it's been on the block for quite some time. You'll find that you really shouldn't be putting your time into developing your own analog frontend – there's existing SDR devices that do exactly that, and believe me, this whole dealing with RF requires intense analog design and testing, and for TV standards, you need significant digital bandwidth to push through your 30 MS/s. Even if you work for food, letting you design that isn't cost-effective; buy existing SDR hardware.

You're doing a few mistakes in your LO calculation (your DAC doesn't produce an IF signal at IF=30 MHz), so you also might be in a bit over your head, too. In that sense, I might add that Michael Karas' comment might be the most time- and cost effective answer: getting someone to do it for you might be cheaper than learning all the SDR stuff yourself on company time.

You can then use commercially or freely available tools to generate the baseband signal you want to modulate up to the carrier frequency. Disclaimer: I'm affiliated with the GNU Radio Free Software project, with comes with gr-dtv, a module containing DVB-T, -T2, -S and -S2 transceiver infrastructure. I'm also affiliated with Ettus, which produce the USRP line of software defined radio devices. But I'd honestly recommend you go for GNU Radio (maybe try my live SDR USB drive image) and an Ettus B200 for your signal generation needs.

You could generate the desired signal once in GNU Radio and save it to a file, and then use GNU Radio to loop that file and transmit the contents using the USRP Sink, or you could do it live, i.e. directly stream the DVB-x signal like a TV station would. Either way, you'd still need a computer to do that – and your raspberry Pi is quite a bit too slow to sustain 30 MS/s over USB3. Simply won't happen, but any modern business laptop would do, probably, at least for the pre-calculated looping case. As you're in an industrial environment, you might prefer on of the cheaper IPC intel boards instead of a laptop, but that's in the end up to you – the benefit is that you can do the development and testing on a bog-normal PC/laptop and once everything works, put the software on a physically smaller computer.

• Thank you for the answer. But I need to ask you another thing. Do you think this product can provide what I need? Because this is much cheaper: elektormagazine.com/news/… – Alper91 Apr 1 at 13:45
• possibly, yes. I've never worked with LimeSDR; I hear it's capable hardware, not as clean signal-wise as the ADI transceiver used by the USRP B2xx, but the software side (driver) is still lacking. Again, never tried it. – Marcus Müller Apr 19 at 11:43