Digital Down Converter (DDC) or Zero-IF receiver

[kurtulmehtap]

Hi All,
I have a 70 Mhz IF, 2Mhz BW, QPSK modulated signal to demodulate.
Should I use a Digital Down Converter (DDC) to get the I-Q pair or should I use a downconverter to get Zero-IF as an input to ADC.

Which one is better?

Also for a 720 Mhz IF, 100Mhz BW, QPSK modulated signal which approach give better results?

Thank you.

 

[axcdd]

720 MHz no way u will build so fast digital mixer on FPGA or DSP processor so that signal should be downconverted before going to your dsp block.

I have a 70 Mhz IF, 2Mhz BW, QPSK modulated signal to demodulate.
Should I use a Digital Down Converter (DDC) to get the I-Q pair or should I use a downconverter to get Zero-IF as an input to ADC.

Remember that ADC itself can be used as downconverter, especially useful when u have narrow-band signal.