[time-nuts] Sine to square wave converter Phase Noise

[bruce at ko4bb.com]

Sorry, I meant the LTC6957-4 of course._SELA = l
FILTA = L
FILTB = H
ie an input stage BW of 160MHz as recommended for a 10MHz + 10dBm input.

Input for the HX4210 was +14dBm.

Comparator was that used in David Partridge's programmable divider (includes the
74AC04 buffers).

Bruce

> On July 29, 2014 at 5:37 AM Magnus Danielson <magnus at rubidium.dyndns.org>
> wrote:
>
>
> You alternate LTC7957-4 and LTC6957-4 and it is only the later that exists.
>
> The LTC6957-4 has a single-stage amplifier stage input, with somewhat
> programmable bandwidth. I assume you used the 50 MHz BW setting.
>
> Cheers,
> Magnus
>
> On 07/29/2014 10:55 AM, bruce at ko4bb.com wrote:
> > Recently I have been comparing the phase noise of the HOlzworth HX4210 and
> > the
> > LTC7957-4.
> > I have found that the performance of these devices is comparable with a
> > 10MHz
> > sinewave input with a PN noise floor below -160dBc/Hz.
> > For offsets below 100Hz the LTC6957-4 is quieter and for offsets below 50Hz
> > or
> > so is lower than that of my measurement setup.
> > I merely mounted the LTC evaluation board in a diecast metal box to reduce
> > the
> > effect of air currents on the LTC7957-4 and used an ultra low noise 3.3V
> > power
> > supply (Abracon) to minimise the power supply contribution to the measured
> > phase
> > noise.
> > Achieving a phase noise performance equal to that on the datasheet was
> > relatively easy.
> > In fact for low offsets the phase noise is lower than that shown on the
> > datasheet.
> >
> > I've also measured the phase noise of a comparator based sine to CMOS
> > converter
> > and its PN floor is about 20dB higher than that of the LTC6957.
> > On completion of measurements PN plots for the various sine to square
> > conveters
> > tested will be added to the web pages I maintain on Didiers site..
> >
> >
> > Bruce
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