high Frequency stable sources at microwave frequency

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afz23

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highly stable sources at microwave frequency

At C-Band and Ku-Band frequencies,what are the different approaches available to generate highly stable(best possible close-in phase noise) signal at this band?

If I need tunability of around 20-30MHz ,what is the best option available?

As we know Phase locked VCOs provides wide range tunability but very poor close-in phase noise.

We hear about DROs and cavity oscillators,where should we replace Phase locked loop vcos with these?
what is the practical feasibility of these approaches?Whether electrical tuning is possible here?or
mechanical(screw tuning) is only the option available.

Kindly provide some references on this topic.
 

DRO oscillator frequency can be tuned just by changing biasing of gate / current conditions. Few MHz are easily achievable, but i did not tried tenth. There may be amplitude loss for larger changes.

In your case i would try to use DRO at lower frequency, for example f/2 or f/4. Tune it using voltage conditions, then use even frequency multiplier x2 or x4.
f/4 frequency can be easily measured, one-stage even frequency multiplier is easy to make. Sometimes second harmonic can be enough without multiplication, wich eases whole design by removing multiplier stage.
 
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using VCO can achieve very stable C-band and Ku band signal, what is your phase noise requirement ?
 

It is not true that microwave phase-locked oscillators have high phase noise. In the PLOs the phase noise is defined by the reference oscllator. If you need a tunable precision signal source, use a synthesizer. Best manufacturer of such devices is Luff Research.
So far the frequency-multiplied PLOs are the only good solution to generate stable signals. A thermostabilized Gunn oscillator is also a good solution.
 

For C-band, you could use a ceramic resonator oscillator (CRO) followed by a frequency doubler. RFMD has some of best CROs on the market. But their frequency range is limited to 4 GHz. For best phase noise try to choose the most narrow-band CRO with the lowest Kv. Here is product catalog: https://rfmd.com/pdf/Signal_Source_PSG_13.pdf

For Ku-band, as mentioned by others above, you don't have a lot of options other than DRO.
 

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jiripolivka said:
It is not true that microwave phase-locked oscillators have high phase noise.
Click to expand...
Well, who has big phase noise? With bad approach it possible shut down everything like some of my colleges has emetic reflex when they see the iron and sacred confidence that everything can buy for small money. For instance Hittite sell own DRO oscillators only for 3000,00 $. It is interesting staff
DRO like component cost nothing ( for 0.3$ from Chines ) and Infineon SiGe transistors within 1$ but result!!!! Minimum 50-100$.
And PCB drawer did not understood where is the problem. He droving big controller with hundreds pins but there is only one transistor! Idiots is it!
 
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I want to know more about DR resonator from China, anybody bought it? Main question can it be made for custom frequency, and what is minimum quantity for low price?

p.s. I like idea of using DRO with parallel feedback at f/2, because DRO with parallel feedback is high power, and gives nice second harmonic.
 

DRO and sapphire resonator oscillators will not be able to tune 30 MHz. Some might tune 15 MHz, but at the cost of poorer phase noise

I personally would get a waveguide cavity, load it with a GaAs high Q varactor diode that is lightly coupled to only tune it maybe 40 MHz, and use a high power device (like maybe 0.25 watt transistor...bipolar if you can find one). I would then phase lock it to maybe a 500 or 1000 MHz saw reference.

You do not mention the step size and the desired phase noise...and that will be important in the details of how you do it.

There are other methods, using broadband multiple PLLs
 
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biff44 said:
DRO and sapphire resonator oscillators will not be able to tune 30 MHz. Some might tune 15 MHz, but at the cost of poorer phase noise
Click to expand...
Sounds good. Transistor Ft should be as min three time higher than oscillating frequency.:-?
And flicker noise should be right.
 

biff44 said:
DRO and sapphire resonator oscillators will not be able to tune 30 MHz. Some might tune 15 MHz, but at the cost of poorer phase noise
Click to expand...

We all know DRO won't work for the range,as higher tunability will spoil its phase noise,its good only for smaller range.
Can you please tell ,upto what range of tuning ,these DROs are best options? can we phase-lock them? what should
be the reference oscillator.


biff44 is spot on, in suggesting this option for,highly stable microwave source,I have been looking for this kind of suggestion. I am not getting any reference literature on this topic of phase locked WaveGuide cavities,I request
members to share some reference material with me.

biff44 said:
You do not mention the step size and the desired phase noise...and that will be important in the details of how you do it.
Click to expand...
I would be needing a step size of about 500KHz.

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I haven't used CROs before,can you please share some reference covering CROs application.
 

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