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convert VCO model to VFC

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curious_mind

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I found a simulink mode of VCO by googling . Just wondering how this works. I wanted to convert this model to VFC. In this model when input is zero, output is still present. I want a model of VFC that generates a sine wave from 0-10KHz in response to DC input of 0-10V.

vco.png
 

betwixt

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This looks like part , and only a small part, of a PLL model. I'm not sure it can do anything as it is except produce whatever frequency the VCO wants to offer, without any control over it.

VCTRL normally tunes the VCO (Voltage Controlled Oscillator being a clue there!) and the difference between it and a reference oscillator is the PD.
It may be this design is intended to deliberately add a DC offset to the VCO signal to somehow skew the PD signal but without the remainder of the diagram we will never know.

Brian.
 

FvM

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If you set the frequency offset to zero and the VCO sensitivity respectively, it will generate the intended charcteristic. It's an abstract mathematical VCO model, be aware that the integrator output rises without constraints until it reaches the double limit. Phase accuracy and sine quality will continuously decrease over time. Better use a physical plausible model.
 

danadakk

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You want an actual working design or just be able to sim the design.

In either case what is resolution you desire in Hz ? Any concerns about latency to
a step change in input ?


Regards, Dana.
 

curious_mind

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I Just modeled VFC in scilab/xcos environment. It works fine. I tried interfacing to an updown counter and the simulation fails. Can you advise on this. (btw we have switched over from matlab to scilab due to commercial reasons)

XCOS model
 

FvM

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Protected Google drive files, please provide Edaboard attachment.
.
 

curious_mind

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oops , please check it.
 

Attachments

  • counter_vco_.rar
    101.2 KB · Views: 48

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