Hi Frank, If you are using the LT5517, you just feed one LO signal. The division of the signal into 90 Degrees is done in the chip. I an using a DDS40-like circuit. It does start as a sine wave but I amplified it up so that is is clipping to the (5.0V) power rails on a LT1250 Video amp.
I'm not using a nice sine wave. The LO needs to be about 1.5 Vpp minimum to work. Dave -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Frank Sent: Wednesday, February 22, 2006 7:47 PM To: [email protected] Subject: [soft_radio] Analog quadrature downconverters and div/2 local oscillator I took a look at the LT5517. Does anybody have a circuit with a div by 2 90deg 0deg phase splitter? I always assumed it was made up with two D flip flops, one positive edge triggered, one negative edge triggered. There would be an issue of filtering caused by the harmonics of the square wave to deal with if the circuit really has digital logic. While we are at it, I never took an IC fab course so I don't know this second one either: I read that a D flip flop takes only 6 transistors in its most simplified VLSI implementation. Does anybody have a picture of that circuit? Frank >Message: 2 > Date: Tue, 21 Feb 2006 16:28:44 -0800 (PST) > From: FRANCIS CARCIA <[EMAIL PROTECTED]> >Subject: RE: Commercial FM > >Hi David, > I have an LTI eval board with the same part. I had it connected to >the 40.455 MHz if of my RA6830 and the output looked pretty good. I >have not tried to connect it to the computer yet. Just got a good >machine in the shack so it is on my list of things to do. > I was using an HP8640B as an LO. frank > >David WardenDurkee <[EMAIL PROTECTED]> wrote: > Hi Frank, >The quadrature demodulator I am using is the LT5517. (40 Mhz to 900 >Mhz) I wasn't looking for any specific FM, I was just scanning around >hoping to find anything. Commercial radio stations are more reliable to find. > Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
