[time-nuts] mixers for frequency measurement

Magnus Danielson magnus at rubidium.dyndns.org
Thu Jan 19 15:44:29 EST 2012


On 01/19/2012 09:31 PM, Don Latham wrote:
> Oh dear I had the wrong idea. Thought PIN's were designed for switching.
> There is a breed of "ultra-fast" diode for protection in MOSFET
> switching circuits like h-bridges. Any better?

I'll replace the PIN diodes in our optical receivers at work, obviously 
they can't handle the gigabits we pass through them.

Cheers,
Magnus

> Don
>
> Bob Camp
>> Hi
>>
>> PIN = designed to be slow (not so good an idea)
>> Avalanche = reverse breakdown (not a good conduction mode, noisy)
>>
>> Bob
>>
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>> Behalf Of Don Latham
>> Sent: Thursday, January 19, 2012 2:22 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] mixers for frequency measurement
>>
>> Soooo, PIN diodes? avalanche?
>> Don
>>
>> Bob Camp
>>> Hi
>>>
>>> Complicating the matter - the time it takes for the junction to go
>>> from
>>> full
>>> on to full off also contributes to the noise. An ideal mixer would
>>> switch
>>> instantaneously.... It's always a tradeoff between various noise
>>> sources.
>>>
>>> Bob
>>>
>>> -----Original Message-----
>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]
>>> On
>>> Behalf Of ed breya
>>> Sent: Thursday, January 19, 2012 12:36 PM
>>> To: time-nuts at febo.com
>>> Subject: [time-nuts] mixers for frequency measurement
>>>
>>> Yes, they are Schottkys, just like the ones used in most mixers - but
>>> much bigger and slower. They would have to be properly impedance
>>> matched, and could be driven to higher power levels, with higher
>>> diode conductance, so (I think) much lower noise. Of course,
>>> amplifying up to higher power will add noise, so it's not "free" in
>>> that respect.
>>>
>>> Ed
>>>
>>> Stefan wrote:
>>> 1N5817 are schottky diodes. Wouldn't they saturate much earlier than
>>> a 2N2222A? If saturation is the right word with a schottky diode...
>>>
>>> I wrote:
>>>   >  5 or 10 MHz could be made even better. I wonder how a ring of
>>> matched
>>>   >  1N5817s would work at saturated power levels - maybe +20 dBm or so.
>>>
>>>
>>>
>>>
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>>
>>
>> --
>> "Neither the voice of authority nor the weight of reason and argument
>> are as significant as experiment, for thence comes quiet to the mind."
>> R. Bacon
>> "If you don't know what it is, don't poke it."
>> Ghost in the Shell
>>
>>
>> Dr. Don Latham AJ7LL
>> Six Mile Systems LLP
>> 17850 Six Mile Road
>> POB 134
>> Huson, MT, 59846
>> VOX 406-626-4304
>> www.lightningforensics.com
>> www.sixmilesystems.com
>>
>>
>>
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>
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