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About RF receiver I/Q modulation/demodulation (Read 342 times)
carl_chao
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About RF receiver I/Q modulation/demodulation
May 19th, 2017, 12:45pm
 
Hi all,

I know that I/Q modulation is for cancelling mirror images, but is I/Q modulation needed under all circumstances? For example, for a direct-conversion RF receiver using FMCW, is I/Q modulation necessary? Why? Also, to get deeper knowledge on this topic, do you have a reference to recommend?

Thank you very much!

CC
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deba
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Re: About RF receiver I/Q modulation/demodulation
Reply #1 - May 29th, 2017, 5:32am
 
If you don't care about integrating RF front end on an IC, and ok with using SAW filters. Yes you can go without doing I/Q modulation.
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shaikh1973
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Re: About RF receiver I/Q modulation/demodulation
Reply #2 - Sep 12th, 2017, 11:37pm
 
First understand what is IQ vector, For this refer :
http://www.rfwireless-world.com/Terminology/what-is-IQ-vector-signal.html
From this u will come to know that IQ vector is formed at the output of complex modulation/multiple access schemes such as OFDM, OFDMA, QPSK, QAM etc. Refer following link for heterodyne and homodyne architectures,
http://www.rfwireless-world.com/Terminology/heterodyne-receiver-versus-homodyne-...
Hence for such transmitters, we require IQ demodulators at
the receiver. Moreover IQ signals gets impaired due to various impairments such as gain, phase, DC offset etc. For this we require IQ compensation algorithms, Refer following for the same.
http://www.rfwireless-world.com/Terminology/IQ-imbalance-compensation.html
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