A Low-Noise Frequency Synthesizer Using Multiphase Generation and Combining Techniques

Amr Khashaba, Ahmed Elkholy, Karim M. Megawer, Mostafa Gamal Ahmed, Pavan Kumar Hanumolu

Research output: Contribution to journalArticlepeer-review


A ring oscillator (RO)-based low-noise frequency synthesizer is presented. Phase noise degradation caused by jitter accumulation in conventional RO-based synthesizers is alleviated by increasing the update rate. To this end, multiple phases of the crystal oscillator (XO) output are generated and edge combined to produce a clock at an integer multiple of the XO frequency, which is then used as a reference clock to a conventional injection-locked clock multiplier that generates a low-noise high-frequency output clock. Unlike conventional delay-locked loop-based multiphase generators (MPGs), the proposed MPG is implemented by using a simple $RC$ network connected between the XO terminals. As a result, the proposed approach consumes little power and, more importantly, does not suffer from jitter accumulation. Inevitable phase-spacing errors caused by process, voltage, and temperature variations, and component mismatches are mitigated by using digital background calibration. Fabricated in a 65-nm CMOS process, the prototype synthesizer operates with a standard 54-MHz crystal and generates a 432-MHz clock by combining eight phases generated by the proposed MPG. Using 432-MHz clock as the reference, an injection-locked clock multiplier generates a 5-GHz output with a measured integrated output jitter of 245 fsrms. The total power consumption is 8.2 mW of which the XO frequency multiplier consumes only 2.8 mW.

Original languageEnglish (US)
Article number8903272
Pages (from-to)592-601
Number of pages10
JournalIEEE Journal of Solid-State Circuits
Issue number3
StatePublished - Mar 2020


  • Crystal oscillator (XO)
  • DCDL
  • Walsh-Hadamard (WH) codes
  • edge combing
  • injection locking
  • multiphase generation
  • phase mismatch
  • ring VCO

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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