Re: [time-nuts] Fury Realhamradio listing
SAIDJACK@aol.com wrote:
In a message dated 4/29/2007 04:13:30 Pacific Daylight Time,
cfmd@bredband.net writes:
Indeed. Three-four transistors and a handfull of caps and
resistors. The
Z3801A uses the 10 MHz clock and thus require a x1000
interpolation, which is
easy enought to acheive. Look at the HP5335A service manual for
further
details. What you do is that you stretch the error-pulse (1-2
cycles) by
charging a cap with one current and discharging it with another,
the output is
then run into a comparator for the sake of gain. This stretched
pulse is then
measured with the coarse clock and voila!
Hi Magnus,
I respectfully disagree, if it was that easy to get 100ps accuracy
and resolution, then the 53132A would have it and not 150ps I would
think.
bye,
Said
Said
Try studying a little history, its been possible to achieve 25
picosecond accuracy and resolution for over 30 years.
Such resolution is routine in Nuclear instrumentation. State of the art
nuclear instrumentation strives for subpicosecond resolution and accuracy.
The reason that the 53132A doesn't have resolution and accuracy better
resolution than 150ps, is that a design choice was made to implement it
all (counters plus interpolators) in a CMOS chip using the delay of a
CMOS inverter to set the resolution. This reduces the cost and
complexity significantly and allows faster cycling of the interpolator
facilitating continuous operation with zero deadtime between
measurements. The drawback is reduced resolution and the requirement for
frequent calibration or the use of a delay lock loop to correct the for
the CMOS inverter delay tempco.
Bruce
From: Dr Bruce Griffiths bruce.griffiths@xtra.co.nz
Subject: Re: [time-nuts] Fury Realhamradio listing
Date: Mon, 30 Apr 2007 11:38:26 +1200
Message-ID: 46352C72.6050204@xtra.co.nz
SAIDJACK@aol.com wrote:
In a message dated 4/29/2007 04:13:30 Pacific Daylight Time,
cfmd@bredband.net writes:
Indeed. Three-four transistors and a handfull of caps and
resistors. The
Z3801A uses the 10 MHz clock and thus require a x1000
interpolation, which is
easy enought to acheive. Look at the HP5335A service manual for
further
details. What you do is that you stretch the error-pulse (1-2
cycles) by
charging a cap with one current and discharging it with another,
the output is
then run into a comparator for the sake of gain. This stretched
pulse is then
measured with the coarse clock and voila!
Hi Magnus,
I respectfully disagree, if it was that easy to get 100ps accuracy
and resolution, then the 53132A would have it and not 150ps I would
think.
bye,
Said
Said
Try studying a little history, its been possible to achieve 25
picosecond accuracy and resolution for over 30 years.
Such resolution is routine in Nuclear instrumentation. State of the art
nuclear instrumentation strives for subpicosecond resolution and accuracy.
The reason that the 53132A doesn't have resolution and accuracy better
resolution than 150ps, is that a design choice was made to implement it
all (counters plus interpolators) in a CMOS chip using the delay of a
CMOS inverter to set the resolution. This reduces the cost and
complexity significantly and allows faster cycling of the interpolator
facilitating continuous operation with zero deadtime between
measurements. The drawback is reduced resolution and the requirement for
frequent calibration or the use of a delay lock loop to correct the for
the CMOS inverter delay tempco.
Ironically, a variant of this analog interpolator technique in combination with
modern FPGA technology is now taking the busniess away from the 53132A.
There are many different reasons why a certain choice of technology is being
made, and not all of them is down to resolution and accuracy. Also, if that
would be the problem, a x1000 lever should not be used but rather a lower
lever like x100 but to a higher clock, and this is infact what more modern
instruments than the HP 5335A does (it uses x100 to acheive 1 ns). One
particular flaw of HP 5335A and several others like it is that the reference
pulses used to calibrate it isn't used to tune it into place but only to
compensate it. A small DA Converter (8 bit would certainly suffice) would have
allowed them to trim up the interpolator scale. Due care would have allowed
them the linearity needed, but for lower lever-rates this is not as much a
problem unless you intend to average alot. If you do want that you want a
higher resolution and then calibrate it up to create a look-up-table correction
which is infact what several more advanced solutions do. I think I have done
quite a bit of homework on these things, but I do not claim to know it all, I
am still attempting to be a humle and good student. My biggest problem is that
I don't have the time to do the experiments that I should do.
The delay-chain interpolator technique was an attempt to get away from complex
and in need of trimming analogue designs. Just look at the HP 5371A and
HP 5372A, but they need trimming too. It is certainly interesting in the form
of CMOS design. However, unless you do full-custom (with the pricetag that gets
you), it is not the best technique to use. The analog interpolator technique
in either the pulse-stretcher form or ADC form gives alot of bang for the buck
once you come of the head-end part of things.
Cheers,
Magnus