-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Ah yes you're right; I've just taken a look myself, and gr-air-modes uses a moving average as a matched filter, which implies a rectangular shape. So your pulse bandwidth is the same as system bandwidth.
On 30.01.2014 11:11, Andrew Rich wrote: > When you demodulate ads-b it becomes just square waves > > Sent from my iPhone > >> On 30 Jan 2014, at 8:01 pm, Marcus Müller <mar...@hostalia.de> >> wrote: >> > Basically, yes, but that's communication theory. I'd refer you to > Kammeyer -- Nachrichtenübertragung, but that's a German book. I > guess Proakis would be a fine source, too, but I don't have his > book at hand right now. > > Anyway, ADB-S should *define* the pulse shape. Best look into > Nick's gr-airmodes code for matched filtering; the matched filter > directly gives you the transmission filter. (But that's even more > signal theory) > > Greetings, Marcus > >>>> On 30.01.2014 10:44, Andrew Rich wrote: Thanks Marcus >>>> >>>> Pulse shape and repetition frequency determine bandwidth then >>>> ? >>>> >>>> Square is the worst - gausian is better ? >>>> >>>> - Andrew - >>>> >>>> >>>> ----- Original Message ----- From: "Marcus Müller" >>>> <mar...@hostalia.de> To: "Andrew Rich" >>>> <vk4...@tech-software.net> Cc: <discuss-gnuradio@gnu.org> >>>> Sent: Thursday, January 30, 2014 5:27 PM Subject: Re: >>>> Modulation question >>>> >>>> >>>> Hi Andrew, >>>> >>>> just a quick heads-up: I nearly missed your message because >>>> it was hidden in another thread, since you seem to have hit >>>> reply and changed subject and text; however, my mail client >>>> recognized the In-Reply-To header, and sorted you in - please >>>> directly write mails unless you actually mean to reply. >>>> >>>> So now for your question >>>>>>> Ads-b uses a 1 MHz pulse position modulation scheme >>>> On 30.01.2014 01:22, Andrew Rich wrote: >>>>>>> Ads-b uses a 1 MHz pulse position modulation scheme >>>>>>> >>>>>>> Is this possible to create on gnu ? >>>> GNU Radio is only a software radio framework. Basically you >>>> can do anything with it that can be done in baseband signal >>>> of a sample rate that your ADC/DAC and mixers (and analog >>>> filters, amps and so on) support. With gr-air-modes there is >>>> a comfortable receiver implemented in GNU Radio, and as a >>>> not-to-rough simplification you can transmit everything with >>>> a software radio that you can receive with one. >>>> >>>>>>> >>>>>>> Is it the data rate that makes the spectrum wide ? 7 >>>>>>> MHz ? >>>> Ok, I don't really understand your question, could you >>>> please elaborate? Reception of ADB-S works quite well with a >>>> 4MHz sampling bandwidth, but I'm not quite sure on the >>>> technical requirements of ADB-S transmission. >>>> >>>> The actual bandwidth of PPM systems of course depends on >>>> pulse shape and pulse frequency. >>>> >>>> Hope I was able to help a little, Marcus -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJS6icXAAoJEAFxB7BbsDrLA08H/RvBszQ5v23OfQYZWB03lnOe FiU0pTbRvVTSwwbYOrjuVEw80CwwwtLGJMBe6Q7IMzvnRkigvitfNI7zM1R17MmL XJ/xGnjxhgCZppOPEl0NW3A8SD4lUvhMqn592FbvovrP789wTrvkfxp+cJU0ZtzP j+wOf8rs+4bvxLYiZfNdjYJRmmNFFG2UgQ/P5n4jEJ610ySDVXXVIi/ZCuQdymSa azQk9BAz/jGa2NychqaJuyOVfuJ3TPiC5qZpOkpv12Zy+HDUR3JbEZCT4+WtSotK bGyvosBlA//lpM4g2CysEu7aXPda727cCGC09voh2Uyd1WFdeXgCW670LEHvFpQ= =vy5B -----END PGP SIGNATURE----- _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio