How to build a 802.15.4/Zigbee O-QPSK demodulator

Hello,

I have searched thoroughly all over the internet for information on how to
demodulate 802.15.4/Zigbee O-QPSK (MSK) signals. Slide 10 on
http://www.ceesar.ch/cms/upload/pdf/emw08/EMW2008_talk.pdf shows the base
band signal, and also says (slide 12) that O-QPSK may be demodulated both
with and without regenerating the carrier (coherent and non-coherent
demodulation). Is this true?

Figure 5 on  http://members.tripod.com/michaelgellis/mixerscom.html shows
a Costas loop that can be used for QPSK; my first thought was to use it as
O-QPSK demodulator, but it doesn't seem to work, I suspect due to the
absense of amplitude changes in O-QPSK.

I had a look at Tim Wescott's MSK paper, page 18 (thanks for sharing), but
still don't get it.

I intend to implement the demodulator with analog circuits.


  Thanks,

      Henning Petersen
      Senior RFIC designer
      www.silicide.dk