Hi again,

Follup from thread started 16 Feb 08...Thanks to everyone who
responded. I didn't get a chance to respond as I was disecting the
filters to see where the problem lay....(it took me a while, but it
eventually turned out to be the phase of the signal reading out the
data from the filter)

Managed to get a decent output from the RRC filters on the TX side
(see link).

http://i248.photobucket.com/albums/g...RC_pulses2.jpg

So now I see something,,,notice the small peak to the left of the
cursor on the second and fourth traces. Should this not be the same as
the peaks beside it?

The next two links are what I see on the I and Q branches on the demod
side. I have zoomed in on one of the pics. The RRC on both branches
are exactly the same as on the I and Q branches of the
modulator.Again, I ask the question...is this what is expected? If so,
how on earth does one try to decode this into something sensible. The
peaks are of varying amplitudes, some are inverted (see just left of
the cursor on the second trace.

http://i248.photobucket.com/albums/g...c/RX_Data1.jpg
http://i248.photobucket.com/albums/g...RC_pulses2.jpg

I had constructed a PLL for the non-RRC version of the QPSK
demodulator, and I could easily get it to recover timing by hanging it
of the I or Q branches after the LPF following the mixer, but with
this, it drifts all over the place and won't lock. Are there better
methods like early-late, Gardner that would be more suitable for
timing recovery?

I would be grateful if someone could check the filter spec. to see if
the coeffs are correct.

Regards
Bob

Here is the detail of the filter
fsym = 128
Beta = 0.25
Fsamp = 1024

No of Coefficients = 81

-0.0070229023149443
-0.0101567256377105
-0.0106995463613499
-0.0081513284932908
-0.0027454853524680
0.0045119843518652
0.0119844900085342
0.0177165731088947
0.0198637673884311
0.0171561105887407
0.0092932360980081
-0.0028279163188171
-0.0171265141152235
-0.0306220077689427
-0.0399632629130674
-0.0421207092441888
-0.0351145115424028
-0.0186283183298937
0.0056366964189598
0.0339772545072063
0.0611209771631681
0.0810472328405277
0.0880859678347950
0.0781178174747294
0.0496594184521266
0.0046158687756456
-0.0514788123965642
-0.1098366649262891
-0.1594084600837957
-0.1883864949522413
-0.1860109812352232
-0.1444040487260019
-0.0601297025887537
0.0647967923675360
0.2226524648114345
0.4005929560133712
0.5820384315208919
0.7486846121353156
0.8828574301801004
0.9698660159441028
1.0000000000000000
0.9698660159441028
0.8828574301801004
0.7486846121353156
0.5820384315208919
0.4005929560133712
0.2226524648114345
0.0647967923675360
-0.0601297025887537
-0.1444040487260019
-0.1860109812352232
-0.1883864949522413
-0.1594084600837957
-0.1098366649262891
-0.0514788123965642
0.0046158687756456
0.0496594184521266
0.0781178174747294
0.0880859678347950
0.0810472328405277
0.0611209771631681
0.0339772545072063
0.0056366964189598
-0.0186283183298937
-0.0351145115424028
-0.0421207092441888
-0.0399632629130674
-0.0306220077689427
-0.0171265141152235
-0.0028279163188171
0.0092932360980081
0.0171561105887407
0.0198637673884311
0.0177165731088947
0.0119844900085342
0.0045119843518652
-0.0027454853524680
-0.0081513284932908
-0.0106995463613499
-0.0101567256377105
-0.0070229023149443