[time-nuts] ? phase comparison or other device

[Ulrich Bangert]

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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