[time-nuts] ? phase comparison or other device
Ulrich Bangert
df6jb at ulrich-bangert.de
Mon Jun 25 05:47:54 UTC 2007
Pete,
> > > 5. Mini-circuits BLP-1.9 low pass filter.
terminating the mixer if output with an lowpass/bandpass filter and NOT
with an diplexer is not so good an idea. Where does the rf go?
Best regards
Ulrich Bangert
> -----Ursprüngliche Nachricht-----
> Von: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Pete
> Gesendet: Sonntag, 24. Juni 2007 03:38
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] ? phase comparison or other device
>
>
> Here is a scheme that seems to work well for comparing stable
> frequency sources in the range of 10 to 100 second
> measurement intervals.
>
> Objective - Measure frequency to +/-2E-12 in less than 1 minute.
>
> Method - Heterodyne DUT output to 1KHz with a master
> reference source +
> mixer feeding a tuned zero crossing detector
> + counter.
>
> Equipment - 1. Master reference source at 5 or 10 MHz, e.g.
> "mature" OXCO or
> GPSDO.
> 2. Synthesizer set to DUT - 1KHz, locked
> to reference
> source. The synthesizer averaged
> output must settle
> to
> 10uHz in 10 seconds, e.g. HP 3335A or 3336C.
> PTS 040 should work fine, also.
> 3. 9 digit/s counter, locked to reference
> source with
> selectable gate time. An input LPF
> (100KHz) helps,
> e.g. HP 5335A.
> 4. Mini-circuits ZRPD-1 mixer. Other
> level 7 mixers
> should work, but haven't been tested.
> 5. Mini-circuits BLP-1.9 low pass filter.
> Other filters
> should work, but haven't been tested.
> 6. Tuned zero crossing detector, accepts
> 0 to 5dBm 1KHz
> sinewave input & outputs 1KHz
> squarewave to counter
> with less than 1nS rms jitter.
>
> Setup - DUT set to +7dBm connects to mixer LO port.
> Synthesizer set to DUT -
> 1KHz at +4dBm connects to mixer RF port. BLP-1.9
> connects to
> mixer IF port. ZCD input connects to BLP-1.9.
> Counter connects
> to ZCD
> output & set for 5 to 10 second gate time. The
> DUT frequency =
> synthesizer setting + counter frequency;
> 10uHz digit = 1E-12 for 10MHz DUT.
>
> The ZCD - Made from 2 Analog devices ADA4899-1, inverting
> configuration,
> cascaded, using +/- 2.5 volt power
> supplies. Both amps
> have their
> non-inverting pins connected (only) to a
> 100 ohm resistor
> to ground.
> Both amps have 5uF//5mH to ground on their
> inverting
> inputs. The
> input amp has Rin = 422 ohms and Rf = 6190
> ohms. The
> output amp
> has Rin = 562 ohms and Rf = open. The
> output amp output
> pin has
> 2ea 100 ohm resistors in series to ground.
> The counter is
> connected
> to the common point of the 100 ohm
> resistors. Nominal
> supply bypassing
> is required. Battery supplies at +/- 3
> volts help isolate
> noise sources.
>
> Only 2 ZCD parts aren't junk box items. The Analog Devices
> ADA4899-1 are in distributor stock as SMT parts only. The 5mH
> inductors are hand wound on MPP toroid cores. 133 turns on a
> 55438 core or 114 turns on 2 stacked 55521
> cores
> using 22 or 24 AWG wire work fine. Other MPP cores will work,
> but limit Bmax to 50mT at 1KHz & 0.5V rms. Gapped ferrites
> are too noisy. The 5uF caps are polypropylene or mylar film types.
>
> Noise floor measurements using HP5335A opt 010 as reference
> source & 1KHz counter + HP3336C synthesizer yielded Favg =
> 10,000,000.000 001 5 Hz and Fdev = 4.3 uHz for 36 samples at
> 5.7 second gate time per sample. 10 sample groups are within
> +/- 2E-12.
>
> Pete Rawson
>
>
>
>
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