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Design >> RF Design >> About RF receiver I/Q modulation/demodulation
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Message started by carl_chao on May 19^th, 2017, 12:45pm

Title: About RF receiver I/Q modulation/demodulation
Post by carl_chao on May 19^th, 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

Title: Re: About RF receiver I/Q modulation/demodulation
Post by deba on May 29^th, 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.

Title: Re: About RF receiver I/Q modulation/demodulation
Post by shaikh1973 on Sep 12^th, 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-receiver.html
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