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Phase noise reduction in voltage controlled oscillators

  • US 9,917,548 B2
  • Filed: 04/07/2016
  • Issued: 03/13/2018
  • Est. Priority Date: 01/10/2014
  • Status: Active Grant
First Claim
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1. A method of designing a voltage controlled oscillator (VCO) comprising an LC tank circuit for generating an oscillator output, an oscillator core to provide regenerative feedback to the tank circuit, supply and tail nodes, and a noise by-pass circuit, the method comprising:

  • designing the oscillator core to generate the oscillator output at a frequency of fo, biasing the core, and connecting the core to a voltage supply;

    designing the noise by-pass circuit at approximately twice the frequency of the oscillator output;

    introducing the noise by-pass circuit into the VCO, with the noise by-pass circuit connected to the supply node and to the tail node, in parallel with the LC tank circuit and the oscillator core, to at least partially immunize the oscillator core from external noise and to reduce noise contribution from the oscillator core; and

    tuning the noise by-pass circuit to obtain a specified performance of the VCO.

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