Re: [Discuss-gnuradio] 4702 usrp daughterboard

[cfk]

OK Eric:
    I have PADS, but I'm a bit faster with Orcad Layout. I'm mostly a
software guy, but I find the occaisional board layout is actually relaxing.
But then all software guys are crazy as we know. PDF, ASCII & Gerber it
shall be.

    50mm x 50mm, hmmm. Well, the 4702 appears to be 65.4mm long x 12.6mm
wide so its a bit big for a 50mm x 50mm board. I really wanted to have it on
a board and not loose. I was thinking of a board that was more like 100mm x
100mm (or 4 inches square). Maybe we need to go back and forth with a couple
of mechanical's.

    I printed out the usrp picture and the schematic, but I dont know which
digital interface connector is which yet. Do you have the silk in a gerber
or perhaps the assy so I can try to figure out how to put the 5 pounds of
parts into the 2 pound bag.


> I think you can get by without a demodulator.  Assume bandpass
> sampling and put the 36 MHz IF into a single channel (I). You can
> probably do this with a mini-circuits RF xformer.  Properly terminate
> the Q input and you're done.  The A/D's are running at 64 MHz so
> you'll fold down to 4 MHz which is not so great for the 8 MHz SAW, but
> OK for 7 MHz.  Matt: comments?
>

On this one, could you consider a sketch of the circuit with the transformer
you have in mind? I suspect your mind is closer to what the AD9862's feel
happy with then mine right now and I would hate to mess up the interface
twixt the 4702 adn the AD9862 with some silly impedance mistake. For some
reason, I was thinking that we wanted to feed the usrp with both I & Q and
put OPA681/OPA691's hither and dither. I need you to straighten me out a bit
on the transformer, termination of the Q input and opamps a bit.


> >     On the 24LC024/025, which do you want? The 024 or the 025? Do you
care
> > if its a DIP or do you wish the TSSOP package. I see this is also an IIC
> > device, so I presume tying their SCL/SDA to the other chips in one bus
with
> > the WP* brought to a pin of yours or Matts choice on the interface
connector
> > is the appropriate circuit for this one. I have used IIC eeproms before,
> > although I have been partial to Philips, the Microchip ones look very
> > similar. VCC=5V for the 024, I presume.
>
> 24LC024 or 24LC025, doesn't matter.  We won't be using the WP pin.
> I suggest TSSOP package.  The daughterboard bus sends up the I2C A0
> and A1 pins depending on what slot the board's plugged in.  A2 should
> be high.  No need to program it ahead of time.  The part can be
> programmed through the host software as part of check out.
> The LC parts run on 3.3V.  All digital i/o is 3.3V.

OK, lets make it the 024 part.
>
> >     You'll have to help me out on the IEC connector a bit. From the data
> > sheet it appears it is an "IEC 169-2", which looks like a european
version
> > of a cable TV inlet connector. I'll have to get my $6 to Matt and get
two of
> > these down here so I can scope that one out and make sure we are not
trying
> > to put square pegs into round holes for our US engineers.
>
> You're right.  It's the Euro cable TV connector.
>
> Send me your snail mail address and I'll get a couple of modules out
> to you.

Its Charles Krinke, 15 Bayside, Irvine, CA 92614 (949) 551-1838.

>
> >     My original thought on the LNA was that it would be in one of those
> > seperate little boxes with a male connector to mate with the tuner on
one
> > side and a female BNC on the other. Those little guys are about 1 inch X
1
> > inch X 0.5 inch thick with ground a terminal on the case and power as a
> > feedthru. I think mini-circuits, Triquint and others have that sort of
> > thing. Perhaps you might have a part/model number in mind. I'll also
look
> > over our LNA's on Monday and see what we are using in the lab. The
thought
> > went that we provide a 2 pin MTA-100 header with power/ground for the
LNA
> > box on the 4702 input since the 4702 is a big item sitting off the board
a
> > couple of inches with its input snout off the edge of the board.
>
> Nothing in mind.  Let us know what you come up with.

I am beginning it might be a good idea to bring the spare DAC pin from the
MAX518 over to a header so we can use a 3 pin MTA-100. That way we can have
ground, power and an optional RF Gain for a VGA (Variable Gain Amplifier)
instead of just a fixed gain LNA. I know VGA's are more expensive then
LNA's, but having the signal there seems reasonable.

I'm plugging away on the schematic. W1FE is out with the girls. When she
returns, I shall exit stage left.

Charles, WA6LWB