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At 09:41 AM 7/09/2006, Murray Lang wrote:<br>
<blockquote type=cite class=cite cite>***** High Performance Software
Defined Radio Discussion List *****<br><br>
What about the situation where QSE is the only "mixing" stage
and I/Q is from a sound card? Where does frequency response come into it?
You've only talked about word size. You seem to be saying that phase is a
DC component of I/Q.<br>
</blockquote><br>
Sorry Bob, I realise that I haven't done justice to what you've posted. I
can see that the commutative nature of mixing helps but I'm having
trouble relating that to the situation I've identified above. The only
oscillator is the 4xoutput carrier and it's being modulated by a sound
card.<br><br>
Murray<br>
VK6HL<br><br>
<br>
<blockquote type=cite class=cite cite>Murray<br>
VK6HL<br><br>
At 01:08 PM 6/09/2006, Robert McGwier wrote:<br><br>
<br>
<blockquote type=cite class=cite cite>Murray:<br><br>
You are getting there. Keep asking questions since you are not the
only person here who needs these questions answered.<br><br>
You might as well have continuous phase since the difference between you
and continuous phase is so small as to not be worth mentioning.
<br><br>
Let P1, P2, ..., Pn be the phase offset of the LO's or clocks
in the N stages of a receive system<br><br>
The phases are COMPLETELY commutative.<br><br>
(P1+ phi) + P2 + P3 + ... + Pn = <br>
P1 + P2 + P3 + ...+ (Pn + phi) <br><br>
Where P1 is the first LO and Pn is the last "LO" in the
system. Since Pn will be the software oscillator in your SDR
system, the precision for phi is determined by the precision of a
floating point number. Since this is 2^23 bits we have
138 dB of range in an IEEE float. Since ALL of
the oscillators in your coherent phasing system are derived from the SAME
source for each of the antennas, the RELATIVE phase
offset, which will be determined by the software LO has this 138
dynamic range. Your phased array can't possibly have enough
elements in it to use all of that precision since they half power beam
width of any real antenna system is going to be about 12 orders of
magnitude worse than you could possibly use.<br><br>
Bob<br><br>
<br><br>
<br>
Murray Lang wrote: <br>
<blockquote type=cite class=cite cite><br><br>
<pre>***** High Performance Software Defined Radio Discussion List
*****
Thanks Robert,
I need to go away and try to get my head around it some more. I need to
understand the relationship between the sampling resolution of I/Q and
the
resolution (ie step size) of phase adjustments that it can apply to RF.
It's not going to be continuous. I'm starting to work on the math, but I
have a way to go.
Cheers
Murray
VK6HL
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<br><br>
<pre>--
AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,
NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman
"You see, wire telegraph is a kind of a very, very long cat.
You pull his tail in New York and his head is meowing in Los
Angeles. Do you understand this? And radio operates exactly
the same way: you send signals here, they receive them there.
The only difference is that there is no cat." - Einstein
</pre><font face="Courier New, Courier"></font></blockquote><br>
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