[Discuss-gnuradio] QPSK Demodulator

[Pepito31 Pepito31]

Hi all,
I'm working on a qpsk demodulator (not differential), see code below :



        # Connect & Initialize base class
        self.connect(self,self.pre_scaler, self.agc, self.costas_loop,
                         self.rrc_filter, self.clock_recovery)

        self.connect(self.clock_recovery, self.diffdec, self.slicer,
self.symbol_mapper,self.unpack, self)

I've removed the diff_phasor block in the flowgraph. By default the
constellation mapper use :
        # find closest constellation point
        rot = 1
        #rot = .707 + .707j
        rotated_const = map(lambda pt: pt * rot,
psk.constellation[arity])
        #print "rotated_const = %s" % rotated_const

        self.slicer = gr.constellation_decoder_cb(rotated_const,
range(arity))

        if self._gray_code:
            self.symbol_mapper = gr.map_bb(psk.gray_to_binary[arity])
        else:
            self.symbol_mapper = gr.map_bb(psk.ungray_to_binary[arity])

I would like to know if rot has to be set to 1 or 0.707 + 0.707j as I
have removed the diff_phasor ?
When I draw the constellation after the clock_recovery block, I see
graphicaly that the symbol are located around +45°, 135°,225°,-45°.

Best regards,

Pepito
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