Low frequency VCO implementation in digital and analog

[fanshuo]

I want to implement an array pf VCOs . whose frequencies are ranging from -100KHz to 100KHz with a step size of 5(or10) KHz.

can anybody gives some idea on the pros and cons of implementation in digital v.s analog( or refer me relevant documents on this subject is also highly appreciated)

especially from the aspects of power consumption, complexity and accuracy.

Thanks very much.

 

[jfyan]

Re: low frequency VCO

I want to implement an array pf VCOs . whose frequencies are ranging from -100KHz to 100KHz with a step size of 5(or10) KHz.

can anybody gives some idea on the pros and cons of implementation in digital v.s analog( or refer me relevant documents on this subject is also highly appreciated)

especially from the aspects of power consumption, complexity and accuracy.

Thanks very much.

hi
i think you can use divider to increase the freq. resolution, and the freq step can be realized by adding or removing capacitors.
good luck.
jeff

 

[fanshuo]

low frequency VCO

Thanks jeff,

But I still need more general comparisons between those two techniques since I am not very familiar with the digital implementations

 

[khouly]

low frequency VCO

u said from -100 Khz
what is it ?

khouly

 

[fanshuo]

low frequency VCO

Thanks Khouly. i should say "centered at 1MHz and in the range of 900KHz to 1.1MHz"

 

[khouly]

low frequency VCO

then u want it , in IC level , or circuit level "board"

khouly

 

[replyanil]

Re: low frequency VCO

go for ring oscillator

 

[fanshuo]

low frequency VCO

to Khouly, It should be implemented in IC level.

to replyanil, LC oscillator would not be practical for integration.But would a DCO be better?

 

[khouly]

low frequency VCO

for this small , frequency , u can make it ring , and after it s nice divider , and the ring oscillator is current controller this is a good approach

LC for sure wouldn't be pratical

khouly

 

[fanshuo]

low frequency VCO

and how about using digital oscillator?
It might be better for mismatch. But I am not very clear about the power consumption.

 

[khouly]

low frequency VCO

what do u mean by digital oscillator , is it a DDS

khouly

 

[fanshuo]

low frequency VCO

is DDS short for direct digital synthesizer?
I think that is what I mean.

 

[khouly]

low frequency VCO

yeah DDS ,is direct digital Synthesizer
it can be used as well , specially the DAC can be used and the reqirment is very relaxed .

khouly

 

[fanshuo]

low frequency VCO

well, then the question is back to which one is better?
If the first priority gives to the low-power design

 

[armixic]

Re: low frequency VCO

Will you system has a XTAL as refrence clock? if you have a XTAL, PLL can help you realize the 5/10K step size. A simple RC relaxation oscillator will work.

 

[khouly]

low frequency VCO

the ring oscillator will need a PLL to control the frequqncy , which will be fine , the DDS is used in very fine and agile systems

so u can use ring oscillator in a PLL to get use reqirents

khouly

 

[fanshuo]

low frequency VCO

Thanks for your input.
They are very helpful