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Author Topic: Synchrodyne/homodyne receiver[MC1350, MC1496, MC1590, CD4046]  (Read 3800 times)
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aProgrammer
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« on: November 30, 2012, 11:43:52 11:43 »

a pdf article/projet from Electronics World, November 1998

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2N5109
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« Reply #1 on: December 15, 2012, 05:10:18 05:10 »

I downloaded and scanned the article.  Direct conversion works and receivers don't have to be as complicated as shown there.  Try this general description

http://www1.ee.ucla.edu/~brweb/papers/Journals/RTCAS97.pdf

what signals are you trying to receive and what frequency? 

regards,
2N5109
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borberk
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« Reply #2 on: December 15, 2012, 08:35:07 08:35 »

You missed the point. Article from Electronic World belongs more to nostalgy then an invitation to build such receiver.
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mrh
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« Reply #3 on: December 15, 2012, 05:58:36 17:58 »

what signals are you trying to receive and what frequency? 

How about a 1030 MHz Receiver with 10 MHz BandWidth ?
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2N5109
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« Reply #4 on: December 22, 2012, 05:03:24 05:03 »

Signals at that frequency are OOK pulsed with information in edge timing and also may have doppler frequency offset.  Pulsed signals not good candidates for this type receiver which is sensitive to phase.  LO needs to be zero beat with received carrier for homodyne to work.  You could do it with I and Q LO but then becomes as complex as superhet with AM detector. 

Guess I missed the point due to living in the past...but then again there is nothing new under the sun.   Smiley

Regards, 2N5109
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mrh
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« Reply #5 on: December 23, 2012, 06:29:03 18:29 »

Signals at that frequency are OOK pulsed with information in edge timing and also may have doppler frequency offset.  Pulsed signals not good candidates for this type receiver which is sensitive to phase.  LO needs to be zero beat with received carrier for homodyne to work.  You could do it with I and Q LO but then becomes as complex as superhet with AM detector. 

Guess I missed the point due to living in the past...but then again there is nothing new under the sun.   Smiley

Can you explain a bit more ? or a pdf or something ?
What do you mean by " You could do it with I and Q LO but then becomes as complex as superhet with AM detector " ? complex how?
And how can I do it using I and Q LO ?

What is the bset methode to get that signal I mentioned before with that frequency ? (LFM signal as you mentioned. Pulsed Sinuside Signal )
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webdog
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« Reply #6 on: December 29, 2012, 03:23:03 15:23 »

How about a 1030 MHz Receiver with 10 MHz BandWidth ?
Assume you are looking at IFF? A simple amplifier stage with suitable filters and a AM demodulator would be my first try!
Going the I/Q route if you are digitizing and do the signal processing with a computer, still you end up with pretty high data rates i.e. 10 Ms/s with I/Q. Still Hittite have some neat chips to help you out... http://www.hittite.com/products/view.html/view/EKIT01-HMC6383 This may well be the simplest way to get going with digitizing.
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2N5109
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« Reply #7 on: December 30, 2012, 05:40:53 05:40 »

Agree with webdog.  Simple design:  Single conversion with high side LO and moderately high 200MHz IF and B=20MHz LC filter will preserve pulse timing and low risk of images at those frequencies.  Use a log detector at IF (~200MHz) to get dynamic range.  Use antenna matching to provide some preselection for image rejection. 

At first was thinking about using I/Q demodulator, then rectangular to polar conversion to obtain amplitude of signal.  (this eliminates non zero beat tone if only using direct conversion with sine OR cosine).  All digital is probably overkill but as you say there may be chips out there that do it nowadays, I don't know.  Hittite part is pretty expensive.  Maybe there is an analog SSB demodulator that does the job for IFF pulse processing. 

Regards 2N5109
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mrh
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« Reply #8 on: January 04, 2013, 08:19:32 20:19 »

Agree with webdog.  Simple design:  Single conversion with high side LO and moderately high 200MHz IF and B=20MHz LC filter will preserve pulse timing and low risk of images at those frequencies.  Use a log detector at IF (~200MHz) to get dynamic range.  Use antenna matching to provide some preselection for image rejection. 

At first was thinking about using I/Q demodulator, then rectangular to polar conversion to obtain amplitude of signal.  (this eliminates non zero beat tone if only using direct conversion with sine OR cosine).  All digital is probably overkill but as you say there may be chips out there that do it nowadays, I don't know.  Hittite part is pretty expensive.  Maybe there is an analog SSB demodulator that does the job for IFF pulse processing. 

Regards 2N5109

Yeah I know. I kind of did the same thing. except of I didn't think of images. I'm not a pro. could you explain about images in such simple system and how to reduce it. plus how it is related ro preserve pulse timing and other parameters? cause I think I'm not giving a great pulse after Log Detector (Fall Time is high).
plus I think the level of noise at the output pulse is a little high. and thats gonna decrease sensitivity of system to around -85dBm (detectable by Pulse Analyzer System as a pulse) .
I'm not sure but I think the problem is in the Log Detector stage. Is there a betther log detector than AD8310 Log Detector ?
(IF is 160MHz if it's related)


Finally what do you mean by "Maybe there is an analog SSB demodulator that does the job for IFF pulse processing" ?
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marianqt
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« Reply #9 on: May 03, 2013, 08:56:57 08:56 »

For ads-b signals very cheap and simple solution could be the dvb-t receiver dongle (R820T+RTL2832) with ADS-B decoder from http://sdrsharp.com/index.php/a-simple-and-cheap-ads-b-receiver-using-rtl-sdr.
I know it's more funny to construct something but at these frequencies the input stage it's a hard task.
The simplest solution seem to be(at least for me) http://www.sprut.de/electronic/pic/projekte/adsb/adsb_en.html

Best regards!
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