Bug in DBPSK blocks

GNU Radio
1

Hi all,

There’s a bug in the block for the DBPSK modulator. The “differential”
param isn’t set to True in dbpsk_mod; it’s just left to default, and
differential defaults to False in the bpsk_mod block. So it really acts
like a BPSK modulator. QPSK was the same. Here’s a patch.

diff --git a/gr-digital/python/digital/bpsk.py
b/gr-digital/python/digital/bpsk.py
index 57cf253…92f3254 100644
— a/gr-digital/python/digital/bpsk.py
+++ b/gr-digital/python/digital/bpsk.py
@@ -117,7 +117,7 @@ class dbpsk_mod(bpsk_mod):

 def __init__(self, mod_code=None, *args, **kwargs):

  •    super(dbpsk_mod, self).__init__(*args, **kwargs)

  •    super(dbpsk_mod, self).__init__(differential=True, *args,

**kwargs)

/////////////////////////////////////////////////////////////////////////////

DBPSK demodulator

@@ -139,7 +139,7 @@ class dbpsk_demod(bpsk_demod):

 def __init__(self, mod_code=None, *args, **kwargs):

  •    super(dbpsk_demod, self).__init__(*args, **kwargs)

  •    super(dbpsk_demod, self).__init__(differential=True, *args,

**kwargs)

Add these to the mod/demod registry

diff --git a/gr-digital/python/digital/qpsk.py
b/gr-digital/python/digital/qpsk.py
index 859d981…1ed3357 100644
— a/gr-digital/python/digital/qpsk.py
+++ b/gr-digital/python/digital/qpsk.py
@@ -149,7 +149,7 @@ class dqpsk_mod(qpsk_mod):
doc += shared_mod_args

 def __init__(self, mod_code=_def_mod_code, *args, **kwargs):

  •    super(dqpsk_mod, self).__init__(mod_code,

  •    super(dqpsk_mod, self).__init__(mod_code, True,
                                   *args, **kwargs)

/////////////////////////////////////////////////////////////////////////////
@@ -171,7 +171,7 @@ class dqpsk_demod(qpsk_demod):
doc += shared_demod_args

 def __init__(self, mod_code=_def_mod_code, *args, **kwargs):

  •    super(dqpsk_demod, self).__init__(mod_code,

  •    super(dqpsk_demod, self).__init__(mod_code, True,
                                     *args, **kwargs)

Incidentally, I question the need for the DBPSK mod GRC block now that
we
have the generic PSK mod GRC block. Might make sense to deprecate it.

–n

2

On Tue, Dec 3, 2013 at 1:52 PM, Nick F. [email protected]
wrote:

Hi all,

There’s a bug in the block for the DBPSK modulator. The “differential” param
isn’t set to True in dbpsk_mod; it’s just left to default, and differential
defaults to False in the bpsk_mod block. So it really acts like a BPSK
modulator. QPSK was the same. Here’s a patch.

Thanks for the report and patch, Nick. I should get to it today, but
in the meantime, I opened ticket #624 in case it slips my timeline
today. In the future, best to put these things up on the Issues
tracker.

  •    super(dbpsk_mod, self).__init__(differential=True, *args, **kwargs)

**kwargs)

 def __init__(self, mod_code=_def_mod_code, *args, **kwargs):

  •    super(dqpsk_demod, self).__init__(mod_code,

  •    super(dqpsk_demod, self).__init__(mod_code, True,
                                     *args, **kwargs)

Incidentally, I question the need for the DBPSK mod GRC block now that we
have the generic PSK mod GRC block. Might make sense to deprecate it.

–n

I quite agree. I have a note to myself to clean this up with 3.8.

Tom

3

Thanks - I reported this as a bug months ago and nobody took any notice

  • so I assumed it was me.

Mike