[Namaste-dev] Modulation/waveforms

Grant Hodgson grant at ghengineering.co.uk
Mon Jul 7 04:06:20 PDT 2008


As part of the Microwave SDR project (uWSDR)

uWSDR.berlios.de   

groups.yahoo.com/group/uwsdr  (membership of the Yahoo group required I believe)


I've  been working on a general-purpose signal source for the middle microwave
bands (2.3/3.4/5.6GHz) called GeMMA - Generator for Multiple Microwave
Applications.  One of the many features of GeMMA is the use of an ADL5375 I/Q
modulator which will allow for arbitrary modulation.  Therefore, if suitable
I/Q signals can be generated then GeMMA will output any desired modulation
scheme at either 3.4 OR 5.6GHz (not both).  This allows for the measurement of
real signals using real (linear or otherwise) power amplifiers at the
frequency of interest.

The first PCBs are on order and due back in a few days; as luck would have it
I'm on holiday for the next week but as soon as I get back I'll start building
and testing the first ones; I've been asked to give a talk on GeMMA at the
AMSAT_UK colloquium 25-27 July so plenty of incentive to get a move on when I
return.  I've started to write a paper about GeMMA as it does a whole load of
other things as well.  The paper won't be finished before I go tomorrow but I
can make an advance copy available if anybody wants it.

The ADL5375 I/Q modulator would be an ideal choice for the Namaste outdoor
unit - $10 each is a small price to pay for a chip that allows total
flexibility in modulation schemes.  

And FWIW I'm working on the design of a matching receiver as well.  All open
source hardware licenced under the TAPR OHL.

More details on the uWSDR Yahoo group; I'll answer whatever questions I can
later next week.

regards

Grant Hodgson  G8UBN



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