[Discuss-gnuradio] Amplitude De-Modulation

[jonshan]

Hello all,

I'm working on an Amplitude De-modulator. I have verified the received
signal is: x(t) = m(t)cos(2*pi*base_freq*t).

x(t) --- |multiplier| --- |lowpass filter| --- k*m(t)
      cos(2*pi*base_freq*t)

My difficulty is creating the lowpass_filter and complex/float conversions.

        channel_coeffs = gr.firdes.low_pass(1.0,
                                            if_rate,
                                            baseband_freq,
                                            baseband_freq/2,
                                            gr.firdes.WIN_HANN)

        center_filter = gr.fir_filter_fff(2, channel_coeffs)

Here the filter is defined as fff, if I use ccf will the output be the
same? Also what does the first input parameter to gr.fir_filter_fff mean?
In am_rcv.py, they set it to '2', but do not show how to derive it.

Jonathan Shan