Phase comparator

[rajeev.komarian@gmail.com]

Hi,
I would like to compare the phase of two 40 MHz signals and get an
output voltage proportional to their phase shift. Although I found
some phase comparator ICs like MM54C932,MM74C932 , TC5081BP and
CD4046BC,Its not clear to me that they work properly with 40Mhz Input
and 3.3 output voltage.
Regards,
Rajeev

 

[Michael Black]

On Wed, 5 Nov 2008, rajeev.komarian@gmail.com wrote:

Hi,
I would like to compare the phase of two 40 MHz signals and get an
output voltage proportional to their phase shift. Although I found
some phase comparator ICs like MM54C932,MM74C932 , TC5081BP and
CD4046BC,Its not clear to me that they work properly with 40Mhz Input
and 3.3 output voltage.
Regards,
Rajeev

They probably won't work up there.

They are also intended for use in phase locked loops, where conditions
define the design. I don't know whether that would affect use in
your application.

The good news is that you are talking about two signals of the same
frequency, rather than trying to lock one signal to another. In that
case, any mixer will do, since non of the complications of a wide
frequency difference are in effect.

So a double balanced mixer of some sort will do. If the signals
are already digital, an exclusive-or gate will do.

Sort of long before there were IC phase locked loops, all phase
comparators were analog. And they all pretty much amounted to a double
balanced mixer of some sort. Maybe not today, but it used to be
that any introduction to PLLs would start with a description of a basic
PLL and it would be using an analog phase comparator.

Michael

 

[Lostgallifreyan]

Michael Black <et472@ncf.ca> wrote in
newsine.LNX.4.64.0811051012170.731@darkstar.example.net:

So a double balanced mixer of some sort will do. If the signals
are already digital, an exclusive-or gate will do.

Agreed. I'd go with that too. And if the signals aren't clean sharp rectagle
waves, a fast Schmitt triggerIC might be enough to prepare them for the XOR.
If you need to experiment with hysteresis to clean up noise you can use a
dual video bandwith op=amp and build two Schmitt triggers with that.

 

[kilowatt]

On Nov 5, 10:56 am, Lostgallifreyan <no-...@nowhere.net> wrote:

Michael Black <et...@ncf.ca> wrote innewsine.LNX.4.64.0811051012170.731@darkstar.example.net:

So a double balanced mixer of some sort will do. If the signals
are already digital, an exclusive-or gate will do.

Agreed. I'd go with that too. And if the signals aren't clean sharp rectagle
waves, a fast Schmitt triggerIC might be enough to prepare them for the XOR.
If you need to experiment with hysteresis to clean up noise you can use a
dual video bandwith op=amp and build two Schmitt triggers with that.

Hi

Is the application only for phase detection or a complete synthesizer
module. 40MHz you say.?

How about other ics such as the NE564N @50MHz by signetics..
Then there is the compare only ecl version MC12040P that should cover
anything up to 80MHz.

KW

 

[FK]

On Nov 6, 3:13 am, kilowatt <nospa...@okanagan.net> wrote:

On Nov 5, 10:56 am, Lostgallifreyan <no-...@nowhere.net> wrote:

Michael Black <et...@ncf.ca> wrote innewsine.LNX.4.64.0811051012170.731@darkstar.example.net:

So a double balanced mixer of some sort will do.  If the signals
are already digital, an exclusive-or gate will do.

Agreed. I'd go with that too. And if the signals aren't clean sharp rectagle
waves, a fast Schmitt triggerIC might be enough to prepare them for the XOR.
If you need to experiment with hysteresis to clean up noise you can use a
dual video bandwith op=amp and build two Schmitt triggers with that.

Hi

Is the application only for phase detection or a complete synthesizer
module. 40MHz you say.?

How about other ics such as the NE564N @50MHz by signetics..
Then there is the compare only ecl version MC12040P that should cover
anything up to 80MHz.

KW

sorry for iintruding in but i have a similar problem only my sine
waves are 125 hz does the same solution apply to my problem and arent
there any Ic's available that i could use