Robert Atkinson wrote:
Hi Bruce,
It's a while since I looked at the HP circuit and patent, but if I
recall correctly a lot of the performance relied on the input circuit.
This used a line receiver with feedback. When I looked there did not
seem to be an equivalent receiver chip available. I'm aware of the sine
-square conversion thread that ran a while ago, but guess this needs as
much attention as the phase comparator.
Robert.
Robert
Attached schematic is for proposed input circuit (one per source).
The ADCMP600 has low power consumption, a well behaved output stage, has
a built in 2mV hysteresis and has a maximum input frequency of 100MHz.
The input protection and coupling arrangement is equivalent to that of
the K34-5991A.
An RF transformer coupled input could be used but this would limit the
lower frequency limit to a few hundred kilohertz or so depending on the
transformer.
The HP style input circuit has a lower frequency limit of around 10kHz.
Bruce
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