[time-nuts] f-multipliers from VHF to 10 GHz

[Bill Byrom]

Wenzel Associates (www.wenzel.com) In Austin TX can build custom rack mounted multiplied very low phase noise crystal sources. I have used their custom microwave multiplied crystal sources at my pre-retirement job (Tektronix RF Application Engineer) with a 12.5 GHz output. A few of my customers also evaluated and purchased these sources for driving the 12.5 GHz external clock input of the Tektronix AWG70000A/B series AWG's and 70KSX series oscilloscopes. My experience with this multiplied source was about 2 to 4 years ago, but they probably can still build these. I think the price was roughly US $15,000 for a rack mounted semi-custom system source.

One customer purchased the Wenzel golden multiplied 12.5 GHz source to get very low phase noise output of a Tektronix AWG70K AWG to generate microwave chirps for use in electron spin spectroscopy. The AWG70K has an internal moderate performance PLL synthesizer but that wasn't good enough for the spectroscopy experiments. When you use the Wenzel 12.5 GHz external clock, the phase noise of the AWG is dominated by the external clock. There is some small additional phase noise due to the AWG clock edge detection and SiGe DAC wideband noise. Another customer needed to generat very low phase noise RADAR signals.

As I remember the Wenzel product block diagram, they used a 10 MHz internal crystal reference oscillator as the master frequency reference with optional EFC electrical frequency control input. A higher frequency very low phase noise VHF crystal oscillator (between 100-200 MHz, I believe) was locked to the 10 MHz internal or external reference, and that VHF oscillator was multiplied and filtered in several stages to get to the microwave range (such as 10 to 12.5 GHz). They could customize their system to provide auxiliary lower frequency outputs from any of the multiplier stages.

The Tek AWG70K series arbitrary waveform generators have an external clock input with a range of 6.25-12.5 GHz. The external clock is double clocked on both rising and falling edges. So with a 12.5 GHz sine input, the internal 10-bit SiGe DAC is clocked at 25 GS/s. The AWG70001A and AWG70001B offset two of the 25 GS/s DACs by 180 degrees to get 50 GS/s AWG performance with a sin(x)/x usable bandwidth of nearly 20 GHz.
--
Bill Byrom N5BB
Retired in Nov 2019 from Tektronix after 32 years as an AE


On Thu, May 14, 2020, at 7:58 PM, Gerhard Hoffmann wrote:
> I have a potential project in the electron spin spectroscopy sector and 
> I need
> one or two clean signal sources in the 10 GHz range. Phase noise at, 
> say, 50 Hz offset
> is important, but anything below 110 dBc  does not care.
> That probably calls for a multiplied crystal. These Hittite PLLs from AD 
> seem to be
> just not good enough, maybe they'd work if pushed, but no reserve left.
> Are there any known proven multipliers chains from VHF to 10 GHz?
> 
> Cheers, Gerhard
> 
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