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receiver design query

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Member level 5
Jun 22, 2005
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HI guys i am right now studying different waveforms going into the receiver.

This is a high freq receiver and its input is a signal of 5GHZ and its out put is 11 Mhz signal(baseband signal)

Now i found out the receiver had 4 output pins going in the baseband processor,

2 are for in phase part (I signal) and 2 are fpr out of phase part (Q signal)

my query is that why a receiver has 2 pins each for both I and Q signal
one of these 2 pins is +ve voltage and the other is same wave but with -ve voltage,

So i wonder what effect will it have when i have these 2 waves but with opposite polarity go into the baseband processor, and how this schme is differernt for the case when I and Q signal have only one pin each


THe baseband I/Q output is differential. The baseband information is carried in the voltage difference between these two signals. The A/D input in the baseband needs to have a differential input to match.

If you have a single pin for I and a single pin for Q, then the information is between the signal and ground. Same information, different representation


Thanks for the answer
regarding input for A/D, what will happen if i add (or subtract) the signals and then fed this signal into the A/D rather than making sure that A/D accepts differential input.

Subtracting the two signals will give me the original signal, will this scheme work the same way as compared to having differential input for my A/D

Differential operation gives many advantages when designing integrated circuits because transistors can be matched one by one. It can result in better linearity and dynamic range. Therefore it is not a good idea to convert to single ended. Use a differential buffer (ADC driver) instead and find a suitable ADC with differential input. Most high speed converters have differential input anyhow.

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