[time-nuts] Nifty "MINI TIC" for DMTD work detail Info please read
Bob Camp
lists at rtty.us
Wed Nov 21 05:10:37 UTC 2012
Hi
A few more parts and likely not quite as much isolation. None of that means it won't do a good job though.
Bob
On Nov 20, 2012, at 11:20 PM, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> The attached circuit is somewhat more efficient and a little quieter.
> With a little elaboration lower distortion is possible.
>
> Bruce
>
> Bob Camp wrote:
>> Hi
>>
>> Given that common practice is to mis-match the IF port on the mixers, it's probably not realistic to depend on exact match for isolation. Simple / cheap common base buffers likely are a better approach. Lots of isolation and not much flicker noise.
>>
>> Bob
>>
>> On Nov 20, 2012, at 9:01 PM, Bruce Griffiths<bruce.griffiths at xtra.co.nz> wrote:
>>
>>
>>> The details about matching (if any) used in the Czech DMTD would be informative.
>>>
>>> To avoid degrading the performance of the DMTD system below that imposed by the mixers any isolation amps used will need a flicker phase noise floor below that of the mixers.
>>> Even an opamp based isolation amplifier can be at least 10dB quieter (for offsets of 10Hz and below) than a typical minicircuits RF amp.
>>> This is still about 10dB or so worse than a good mixer.
>>> A well designed low gain isolation amp built with discrete transistors can have significantly lower additive phase noise than an opamp.
>>>
>>> To reduce the DMTD system noise one can either:
>>>
>>> 1) Carefully match all ports using series resistors, pads etc as necessary to achieve the required isolation together with a high output low flicker phase noise amplifier to drive the splitter
>>>
>>> 2) Use isolation amplifiers with very low flicker phase noise.
>>>
>>> Some isolation between the 2 RF inputs of a DMTD is usually necessary to avoid injection locking of the 2 sources being compared.
>>>
>>>
>>> Bruce
>>>
>>> Bob Camp wrote:
>>>
>>>> Hi
>>>>
>>>> Those isolation numbers are *highly* dependent on very good matching at all ports. That's rarely the case unless you have a bunch of pads running around the system.
>>>>
>>>> Bob
>>>>
>>>> On Nov 20, 2012, at 5:49 PM, Bruce Griffiths<bruce.griffiths at xtra.co.nz> wrote:
>>>>
>>>>
>>>>
>>>>> Typical Minicircuits SMT RF amps have a phase noise at best 20dB worse (@10Hz offset) than the mixer/phase detector.
>>>>> Their reverse isolation is quite low (<<40dB)
>>>>>
>>>>> The principle reason that the Czech DMTD has such low internal noise is due to the absence of any isolation amplifiers.
>>>>> They use the outputs of a 2 way splitter to drive the LO inputs of the mixers.
>>>>>
>>>>> A output to output isolation of 40dB or more at 10MHz is possible with some minicicuits splitters (e.g. SYPS-2-1).
>>>>> The ZRPD1 has an RF1 - RF2 isolation of around 70dB at 10MHz.
>>>>>
>>>>> With a channel to channel isolation of around 110dB for a 2x ZRPD1 + Splitter combination isolation amplifiers may not be necessary.
>>>>>
>>>>> Bruce
>>>>>
>>>>> Bruce Griffiths wrote:
>>>>>
>>>>>
>>>>>> Since mixer noise is one of the limiting factors using a mixer with low flicker noise will help.
>>>>>> NIST found that a custom mixer using diode connected (collector base short) 2N222As had a significantly lower flicker phase noise than either the ZRPD1 or the 10534A.
>>>>>> They used off the shelf 1:5 impedance ratio transformers (probably from Minicircuits).
>>>>>> Another issue is the flicker phase noise of any isolation amplifiers used.
>>>>>> This is particularly critical if each mixer uses its own isolation amplifiers.
>>>>>>
>>>>>> My current amplifier phase noise measurement setup (for measuring the additive PN of a pair of well matched amplifiers) has a self noise of around -170dBc/Hz @ 1Hz offset for a 10MHz input.
>>>>>> Ideally the additive phase noise of any isolation amplifiers should be well below that of the mixers.
>>>>>>
>>>>>> Bruce
>>>>>>
>>>>>> EWKehren at aol.com wrote:
>>>>>>
>>>>>>
>>>>>>> Yes Bruce I have the paper. I am not suggesting to copy it verbatim but if
>>>>>>> there is a way to reach reasonable priced 1 E-14 members of the list should
>>>>>>> pipe in. I am willing to do an other board. the rest of the systems well
>>>>>>> on its way. Einally after three years.
>>>>>>> Bert Kehren
>>>>>>>
>>>>>>>
>>>>>>> In a message dated 11/20/2012 3:28:57 P.M. Eastern Standard Time,
>>>>>>> bruce.griffiths at xtra.co.nz writes:
>>>>>>>
>>>>>>> EWKehren at aol.com wrote:
>>>>>>>
>>>>>>>
>>>>>>>> The D/M is being revisited because of the counter performance. 1 E-13 is
>>>>>>>> easily attainable but the Czech IREE published a paper and claim 2 E-15.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>> Do you mean the paper ""optimization of dual-mixer time-difference
>>>>>>> multiplier" ?
>>>>>>> The ZCD developed in this is a bit of a kludge and is far from optimum.
>>>>>>> Reverse engineering the circuit from the description given in the paper
>>>>>>> isn't too difficult.
>>>>>>> They claim an instrument limited ADEV of ~7E-15 @ 1s.
>>>>>>> Do you have a copy of this paper?
>>>>>>>
>>>>>>>
>>>>>>>> Bert Kehren Miami
>>>>>>>> _______________________________________________
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>> Bruce
>>>>>>>
>>>>>>>
>>>>>>>
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts at febo.com
>>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>>> and follow the instructions there.
>>>>>
>>>>>
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts at febo.com
>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>> and follow the instructions there.
>>>>
>>>>
>>>>
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
>
> <DualCEBuffer3.gif>_______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
More information about the Time-nuts_lists.febo.com
mailing list