signal processing - DFT phase and amplitude by using vhdl core in FPGA -

how find out phase , amplitude of analogue waveform ? receiving 1 analogue signal 1 sensor, using analogue waveform want find out dft (phase, amplitude) fundamental frequency , second harmonic. converted analogue signal through adc applied fpga. in fpga want use ip dft 4.0 core, dft core output imaginary , real values. using how can determine phase , amplitude of fundamental , harmonics?

for each complex (re, im) output can calculate magnitude , phase this:

magnitude = sqrt(re*re + im*im); phase = atan2(im, re); 

if know frequency of fundamental (and harmonics) can calculate appropriate fft output bin index using formula:

i = n * f / fs 

where n fft size, f frequency of interest , fs sample rate.