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low noise regulator for vco

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hunk

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usually most vco are powered by a analog linear regulator.
can vco be supplied by one digital linear regulator? it means the regulator is still linear regulator not switch-type, DCDC. but because it is digital, its output voltage will changed step by step, maybe the step is 10mv, 20mv,... . i dont know if this style was used in vco in any real product. will this worsen the important noise performance? anybody has such experience?
 

biff44

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people with critical applications always use a linear regulator because:
1) it cleans up the power supply noise, reducing output sidebands/spurious
2) it stabilizes the supply voltage to the vco, reducing frequency drift

If you want to power a vco from something like a DAC, you certainly can. However, as the power supply voltage changes, the vco will drift (until the voltage changes enough for the DAC to toggle a LSB, in which case there is a sudden noise burst, and then relative calm again). Most systems can not tolerate sudden bursts of noise, so that would be out.

If you are using a DAC, you will probably want to filter the heck out of the power supply running to the DAC. You will need a whole lot of capacitors, since there is no active noise cancelling that you would normally get in the 1-200 KHz range with an analog voltage regulator. You have to make that up with big capacitors.

Rich
Magufffin Microwave
www.MaguffinMicrowave.com
 

pancho_hideboo

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biff44 said:
If you want to power a vco from something like a DAC, you certainly can.
I think hunk assumes digital adjustment of feed back resistor ratio in linear regulator.

biff44 said:
However, as the power supply voltage changes, the vco will drift (until the voltage changes enough for the DAC to toggle a LSB, in which case there is a sudden noise burst, and then relative calm again).
Most systems can not tolerate sudden bursts of noise, so that would be out.
Right.

See https://www.designers-guide.org/Forum/YaBB.pl?num=1277523905/3#3
 

BigBoss

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A silence regulator is very neccesary for low noise VCO becuase regulator noise is corrolated much with VCO Phase Noise..
The linear regulators can supply low noise voltages,switched regulators are alwys more noisy whatever you take or use ..( large capacitors, inductors etc.)

For instance, VCO manufacturers measure their products with simple batteries to see Phase Noise..
 

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