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  1. #1
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    I want to design a voltage-controlled ring oscillator

    hi all,

    I want to design a voltage-controlled ring oscillator, a simple, low-speed, wide-tuning oscillator, anyone can offer any help?

    thanks in advance!

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    Re: I want to design a voltage-controlled ring oscillator

    check this , the transistors with the DC input are the transsitors used in control

    this work , as u change the DC voltage uchange the current the upper inverter so the delay of the inverter change , so the frequency of oscillation will change as well

    khouly


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    Re: I want to design a voltage-controlled ring oscillator

    Dear khouly
    thank you very much
    your circuit is good, and i will try it
    i have already design a ring oscillator circuit, it work well in simulation
    i'm glad to get your suggestion or advice




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    Re: I want to design a voltage-controlled ring oscillator

    Dear gingerjiang
    i have check ur circuit , it is good , and the nice thing about it , that u change the delay of the inverter by changing the load capacitance by the varactors used

    mine is by changeing the current ,
    i donot know which one will give u wide tuning range , u have to check it by simulatin , also u have to check the phase noise performance of each

    and then decide which one will be more suitble ,

    also u have to check how to add a voltage to current converter , to the current controlled ring oscillator

    khouly


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    Re: I want to design a voltage-controlled ring oscillator

    Quote Originally Posted by khouly
    Dear gingerjiang
    i have check ur circuit , it is good , and the nice thing about it , that u change the delay of the inverter by changing the load capacitance by the varactors used

    mine is by changeing the current ,
    i donot know which one will give u wide tuning range , u have to check it by simulatin , also u have to check the phase noise performance of each

    and then decide which one will be more suitble ,

    also u have to check how to add a voltage to current converter , to the current controlled ring oscillator

    khouly
    dear khouly
    i have simulated these two circuits, and now i use your circuit.
    i find that your circuit's tuning range is larger, while mine's control voltage is disturbed by clock feedthrough, meanwhile isn't robust by process variation.
    thank you very much
    you said that i should check the phase noise performance, i'm beginner. would you like to introduce me how to simulate it?



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    Re: I want to design a voltage-controlled ring oscillator

    it depends on which tool u will use
    ADS which is based on HB "Harmonic Balance" or Cadence which use PSS "Periodic Steady State"

    if ADS i can help you , if cadence check this appnote by cadence it is very good
    http://www.cadence.com/community/vir...F_VCO533AN.pdf

    khouly


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    Re: I want to design a voltage-controlled ring oscillator

    i have some question, when you simulate the ring oscillator, what is its phase noise and the offset frequency??, what is the Phase noise typically in a ring oscillator???

    thanks



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    Re: I want to design a voltage-controlled ring oscillator

    about the phase noise and frequency offset , u should specify it , coz u measure it according to a standard ,
    about the typical valuse i don't have an accurate number but generally it will be for sure worth than LC oscillator

    khouly



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    Re: I want to design a voltage-controlled ring oscillator

    Quote Originally Posted by khouly
    about the phase noise and frequency offset , u should specify it , coz u measure it according to a standard ,
    about the typical valuse i don't have an accurate number but generally it will be for sure worth than LC oscillator

    khouly
    i just want to know worth to what extent , i know it may be much worth but for example at 3 MHz offset , phase noise typically ?

    thanks



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    Re: I want to design a voltage-controlled ring oscillator

    dear khouly
    i use cadence, and i have download the document you provide, and i will try it
    thanks again



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    Re: I want to design a voltage-controlled ring oscillator

    ok , simulate it and we will see
    and what about ur PLL , did u tried to minimize the jetter

    khouly



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    Re: I want to design a voltage-controlled ring oscillator

    Quote Originally Posted by khouly
    ok , simulate it and we will see
    and what about ur PLL , did u tried to minimize the jetter

    khouly
    i use cadence to simulate the ring oscillator, but failed
    i don't know the cause, maybe need the special rf model for MOS transistors?

    so i want to use ADS, would you like help me?



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    Re: I want to design a voltage-controlled ring oscillator

    sure
    mainly to do oscillator analysis in ads use transient or HB analysis

    which version of ads do u use ?
    check the manual of ADS about HB smulation , u will find there a good example

    khouly



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    Re: I want to design a voltage-controlled ring oscillator

    Quote Originally Posted by khouly
    sure
    mainly to do oscillator analysis in ads use transient or HB analysis

    which version of ads do u use ?
    check the manual of ADS about HB smulation , u will find there a good example

    khouly
    hi khouly
    i use cadence to simulate the ring oscillator, and it is successful
    thank you anyway
    i found the noise of ring oscillator is large, how can i reduce it? which methods are there generally?



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    Re: I want to design a voltage-controlled ring oscillator

    typically in Ring oscillator the phase noise is larger than LC oscillators

    but i donot know how to minimize the phase noise of ring oscillator

    may be one of the experts help us to do so

    khouly



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