[time-nuts] Low-Cost 6+ GHz Prescaler

Samuel D. [CPC] sam at canardpc.com
Fri Mar 26 10:57:25 UTC 2010


No, I can't. The frequency limitation for this project doesn't come from the
prescaler itself.
The 53131A/53132A/53181A Channel 3 internal input is limited to ~70 MHz and
is expecting a /128 prescaler, so the maximum "displayable" frequency is
around 9 GHz. I reached 100 MHz in the preliminary tests (12.8 GHz
displayed), but it was at the cost of major additional efforts. That's why
OPT50 and OPT124 are not retrofitable like OPT30 : they require a
modification on the main board to accept a higher divider ratio. This
project is intended to be a "clean" modification for the 531xxA counter and
not a "generic" prescaler. This said, I can add layout options to use the
board as a generic prescaler. I already planned a SMA output (near the HE10
connector for the 53131A), an external +12V input voltage and a dipswitch to
select the divider ratio (/100 - /128 - /256 - /500 - /512 - /1000). Nice,
isn't it ? ;)



-----Message d'origine-----
De : time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] De la
part de Bob Camp
Envoyé : vendredi 26 mars 2010 02:53
À : Discussion of precise time and frequency measurement
Objet : Re: [time-nuts] Low-Cost 6+ GHz Prescaler

Hi

If you take a look at the ADF 5001 spec sheet you can see pretty well what a
simple match can do at the high end of the range. On the 5001 they may have
gone just a bit overboard. Any bets about the part liking to oscillate right
around 20.01 GHz?

A little box with a 5001 and a 4107 might make a nice counter accessory.
Instant 1 to 25 GHz counter. Toss in a second 4017 to another input and you
have 200 MHz to 6 GHz covered. With some luck you just might be able to make
them both to divide by some nice round number like 1,000. 

Bob


On Mar 25, 2010, at 9:18 PM, Bob Camp wrote:

> Hi
> 
>> From a quick eyeball look at the S parameter data, there may be a simple
L network that would give you a few more db in the top couple of GHz.
Certainly a lot cheaper than an amp. 
> 
> Bob
> 
> 
> On Mar 25, 2010, at 9:07 PM, Samuel DEMEULEMEESTER wrote:
> 
>> About MMIC, that's true for the Minicircuits parts. Roll off is high at
the
>> top of the range (from 13 dB to 8 dB), but the NBB-300 from RFMD seems to
>> have flat gain curve from DC to rated freq. This said, that's only paper
and
>> I don't know the real behavior of this chip.
>> 
>> About sensitivity, 0 dBm is for 8 GHz, exceeding the rated specs of the
>> components (7 GHz for the ADF4107 for exemple). So, my "real" target is 6
>> GHz, but even at those freq, sensibility without amp stage is -10 dBm in
the
>> worst case (it began to drop after 4 GHz). Doesn't looks sensitive
enough,
>> does it ?
>> 
>> 
>> -----Message d'origine-----
>> De : time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] De la
>> part de John Miles
>> Envoyé : vendredi 26 mars 2010 01:50
>> À : Discussion of precise time and frequency measurement
>> Objet : Re: [time-nuts] Low-Cost 6+ GHz Prescaler
>> 
>> 
>>> RFMD seems to produce some nice MMIC, for example the NBB-300
>>> (http://www.rfmd.com/CS/Documents/Nbb-300.pdf), but I never used a RFMD
>>> amplifier. I used Agilent/Avago MMIC since years with great results, but
>>> always with frequencies no more than 3 GHz.
>>> 
>>> Anyone have some experience with DC-8/12 GHz MMIC and which's the best ?
>> 
>> My experience is that they roll off pretty quickly right where you are
>> looking for extra gain.  You'll probably end up with more gain where you
>> don't need/want it, and not as much as you'd like at the very top end of
the
>> range.
>> 
>> The best off-the-shelf performance will probably come from Hittite's
parts.
>> Compared to the Mini-Circuits parts, they are relatively power-hungry,
>> expensive, and hard to work with.  They're available only as LFCSP
packages
>> or bare dice, and only in lots of 10 or more.
>> 
>> IMHO few users would reject your prescaler board due to a sensitivity
spec
>> of 0 dBm.  At lower signal levels people are more likely to be using a
>> spectrum analyzer than a high-precision counter.
>> 
>> -- john, KE5FX
>> 
>> 
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