How to add I/Q signal after the mixer?

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pugongying

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In an I/Q modulator,we use two seperate mixers to do up-conversion of I/Q signal,then how do we add these two paths together and then drive a PA?
 

You need a simple combiner to add the two paths.
 

Most people would combine the I/Q modulated IF signal BEFORE the upconversion. If you modulate the I channel, and then upconvert; and modulate the Q channel and upconvert with a 2nd mixer, you then have to worry a lot about the Amplitude and Phase balance between the two paths.
 

pugongying said:
In an I/Q modulator,we use two seperate mixers to do up-conversion of I/Q signal,then how do we add these two paths together and then drive a PA?
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simple, you connect in your IQ modulator the I and Q outputs from these two separate mixers to the same load(=inductor or resistor). then you have I+jQ...
 

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