Charles Steinmetz posted a link to Wenzel Squaring circuits in Li Ang's thread,
and I'm particularly interested in the line receiver method. On the wenzel.com
page the line receiver was an SN55182. In Bert Zauhar's GPS Standard, he used
an LTC-1485 for the OCXO input. Is there something in particular I should look
at to decide on a good LVDS device? Specifically I'm looking at a DS90LV012A
for two places: 1) OCXO input and 2) PWM output from my PIC, which will be
differential at 0 - +2.5 on both legs. It turns out that temperature affects
the PWM output voltage, so squaring it properly makes a big difference.
We're currently using a 74AHC125 gate for both 1) and 2), but I had the idea to
feed differential PWM to a line receiver for remoting the OCXO from the GPSDO
unit. It seems like a good idea for the OCXO input, as well, but one leg would
be grounded as in the wenzel.com circuit. Any thoughts would be appreciated.
Bob - AE6RV
From: Charles Steinmetz <[email protected]>
To: Discussion of precise time and frequency measurement <[email protected]>
Sent: Thursday, December 25, 2014 2:31 PM
Subject: Re: [time-nuts] schematics of frequency counter
<snip>
I agree with Bruce. The circuit below avoids these problems. It is
generally known as a "Wenzel squarer" (after Charles Wenzel, who
popularized it -- see
<http://www.wenzel.com/library/time-frequency-articles/waveform-conversion-part-i-sine-to-square/>).
I revised and simulated a circuit I use all the time for 5v output to
produce a 3v output, but I did not build it, so some adjustment may
be required. All resistors should be metal film. The 1uF capacitors
should be X7R, and the 100nF and 10nF capacitors should be
NP0/C0G. "Design center" for this circuit is a 10MHz input at 1Vrms
(not shown is the 50 ohm input resistor that would terminate a 1Vrms,
50 ohm source).
<snip>
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