Termination of AC coupled 100MHz clok to generate low jitter 50MHz clock?
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From: John Fields on 26 Jan 2010 11:53 On Tue, 26 Jan 2010 15:42:37 -0000, "Nial Stewart" <nial*REMOVE_THIS*@nialstewartdevelopments.co.uk> wrote: >More details of the design.... > >Hmm. The 1mW into 50ohm input I'm told produces about 0.6V (not >what I calculated but a real world measurement from the client). --- E = sqrt(PR) = sqrt (0.001W * 50R) = 0.22 volts, RMS = 0.31 volts, Peak = 0.62 volts, Peak-to-Peak JF
From: Jim Thompson on 26 Jan 2010 12:07 On Tue, 26 Jan 2010 10:53:26 -0600, John Fields <jfields(a)austininstruments.com> wrote: >On Tue, 26 Jan 2010 15:42:37 -0000, "Nial Stewart" ><nial*REMOVE_THIS*@nialstewartdevelopments.co.uk> wrote: > > >>More details of the design.... >> >>Hmm. The 1mW into 50ohm input I'm told produces about 0.6V (not >>what I calculated but a real world measurement from the client). > >--- > > E = sqrt(PR) = sqrt (0.001W * 50R) > > = 0.22 volts, RMS > > = 0.31 volts, Peak > > = 0.62 volts, Peak-to-Peak > > >JF I had such frustration with clients tossing around dBm that I had my son write this little executable... http://www.analog-innovations.com/SED/NODBM.zip ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Joel Koltner on 26 Jan 2010 12:37 "Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote in message news:t68ul5p2l5gto2v0mrpm7hbvdvu6se80dn(a)4ax.com... > I had such frustration with clients tossing around dBm that I had my > son write this little executable... > http://www.analog-innovations.com/SED/NODBM.zip Nice... good way to demonstrate how reference impedances matter. My experience is that many times people are effectively measuring voltages but the displayed result on, e.g., a spectrum analyzer come out in dBm (with an assumed 50ohm reference) which causes no end of confusion. "Why does this amplifier show 25dB gain when it's spec'd at 15dB?" "Because you'r measuring voltage gain and the data sheet is showing power gain..." ---Joel
From: Joop on 27 Jan 2010 16:58 On Mon, 25 Jan 2010 15:11:17 -0800, Joerg <invalid(a)invalid.invalid> wrote: >Or use the voodoo method, build an oscillator and do injection locking. >That's almost guaranteed to produce some jaw dropping in the design >review :-) At the time I was not aware of the term or concept "injection locking", but for personal use I created a PIF12Fxx base serial output frequency logger. Besides running on its own usual setup crystal I wanted to try and see if this minimalist design could be made to work on my 10MHz reference as well. The simplest thing I could thing of was feeding it 10MHz directly to the crystal oscillator input via a few KOhm plus a cap. It was fun to see it move the required tens of Hz when the reference was connected. No switches required. It runs free when standalone and locked when the BNC is plugged in. Cool.. Joop
From: Jim Thompson on 27 Jan 2010 17:13
On Wed, 27 Jan 2010 22:58:39 +0100, Joop <jojo(a)xs4all.nl> wrote: >On Mon, 25 Jan 2010 15:11:17 -0800, Joerg <invalid(a)invalid.invalid> >wrote: > >>Or use the voodoo method, build an oscillator and do injection locking. >>That's almost guaranteed to produce some jaw dropping in the design >>review :-) > >At the time I was not aware of the term or concept "injection >locking", but for personal use I created a PIF12Fxx base serial output >frequency logger. Besides running on its own usual setup crystal I >wanted to try and see if this minimalist design could be made to work >on my 10MHz reference as well. The simplest thing I could thing of was >feeding it 10MHz directly to the crystal oscillator input via a few >KOhm plus a cap. It was fun to see it move the required tens of Hz >when the reference was connected. >No switches required. It runs free when standalone and locked when the >BNC is plugged in. Cool.. > >Joop My favorite trick is to make a low frequency "oscillator" by using a shift register (looped on itself) driven by a crystal oscillator, then "injection lock" by resetting the shift register appropriately by comparing lead-lag between signal and shift register state (digital phase detector). ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |