Hi Said,
Yes, I saw your message from 2009 where you warned about the sine
waves. That's why I was watching for it. Thanks for the warning. I
also realized that a DC Block and a 10 db attenuator makes a very nice
TTL or CMOS to Wavecrest converter for anything except 1 PPS which would
need about 15 db. I tried an old circuit that uses an MC10116 ecl line
receiver - it's actually a dead Racal Dana 1992 counter where I'm using
the processing on the external reference input to square up the signal.
It gives me a slew rate equivalent to about a 50 MHz sine wave. It
helped a lot, but not enough. I'll try a 74AC04 and a BRS2G
Differential Line Receiver (risetime < 3ns, 400Mbps throughput). Both
are in my junkbox.
Ed
On 8/20/2013 8:12 PM, Said Jackson wrote:
Guys,
The dts needs to be driven by square waves, driving them with sine waves gives
jitter values that are displayed significantly too high due to trigger noise.
Holzworth makes a small sine wave to square wave converter that can drive 50
ohms. Use a DC block and an attenuator on the cmos output to avoid damaging the
dts inputs. You can make your own converter using a single fast cmos gate,
resistor, and blocking cap. By using hand-selected gates I was able to achieve
less jitter with that circuit than what the Holzworth box was able to achieve.
Doing that conversion can bring down the measured rms jitter on a very good
10MHz sine wave source from 10ps+ to less than 2ps - basically at or below the
noise floor of the dts.. Once you run at the units' noise floor, you know your
source is quite good..
Bye,
Said
Sent From iPhone
On Aug 20, 2013, at 18:51, Ed Palmer <[email protected]> wrote:
Adrian,
I used Timelab to assess the reaction of the DTS-2077 to different sine wave
inputs. The differences in the noise floor are surprising. The attached
picture was made by taking the output of an HP 8647A Synthesized Generator
through a splitter, and then through different lengths of cables to the inputs
of the DTS-2077. The combination of splitter and cable loss meant I couldn't
get +7 dbm @ 1 GHz. If I could have, the 1 GHz line might have been lower than
it was.
Ed
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