Can anyone suggest me with an I/Q demodulator IC with high input frequency range(100KHz to 12GHz) and wide bandwidth(DC to 1GHz)

 

Check Marki with I/Q mixer.
Usually it is required to do a down conversion before I/Q demodulation, mainly for very wide frequency range as 100kHz to 12GHz.

Jean-Louis

 

Is there any I/Q demodulator IC in the range of 8GHz to 10GHz

 

You was asking for 100kHz-12GHz not for 8-12GHz. Marki I/Q mixer can provide RF/LO 8-12GHz IF :O to 1GHz.

Jean-Louis