I branch and Q branch in a dual conversion radio

[robismyname]

I attached a image related to my question. The image is a block diagram of a "generic" dual conversion radio I presume. What draws my attention is the baseband section that has the I branch and Q branch and to the right of this there is text that says A-to- converter.

My question are:

1) Is this particular block diagram implying I/Q modulation/demodulation?

2) Whenever I see I branch, Q branch should I always presume that this means the radio is using I/Q modulation/demodulation?

3) In reference to the TX, the A-to-D converter's input is from the FPGA,Processor,etc but how does it know that its output will be Inphase or its output will be Quadrature? Arent both A-to-D converters the same in the TX chain?

4) Is the mixer between the baseband and IF section double balanced?

5) In referecne to the TX chain, what is coming out of the I and Q branch, sine waves 90 degrees out of phase form each other?

 

[G4BCH]

1. Yes

2. Yes

3 The TX path converter should be digital to analogue, the input coming from the DSP. ( maybe this is where the confusion is coming from ) As to how does each channel know whether it is I or Q, that is part of the data flow design. Both converters may be the same but the input data from the DSP is not.

4. Yes

5 the inputs to the TX the chain are I data, Q data and the Local Oscillator, the output is the sum of the I & Q signals each multiplied by the local oscillator; a modulated rf waveform.

 

[fanshuo]

1 Yes
2 No. e.g.:I/Q channel in receiver analog part could be only for the purpose of image rejection
3 The AD converter are the same. They do not need to know which one is in phase and which one is quadrature. Digital part take care of this.

4 It can be double balanced, single balanced.
5 No.