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Re: [Discuss-gnuradio] Modulation question
From: |
Andrew Rich |
Subject: |
Re: [Discuss-gnuradio] Modulation question |
Date: |
Thu, 30 Jan 2014 20:11:29 +1000 |
When you demodulate ads-b it becomes just square waves
Sent from my iPhone
> On 30 Jan 2014, at 8:01 pm, Marcus Müller <address@hidden> wrote:
>
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> 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"
>> <address@hidden> To: "Andrew Rich" <address@hidden>
>> Cc: <address@hidden> 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
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