A new CMOS active transformer QPSK modulator with optimal bandwidth control

Adrian Tang, Fei Yuan, Eddie Law

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


This brief presents a new quadrature phase-shift keying (QPSK) modulator for Bluetooth applications with an optimal transaction bandwidth control. The modulator reduces the bandwidth of the modulated carrier by minimizing their transition sharpness. CMOS active transformers are developed and utilized in quadrature oscillator and multiplexer of the modulator to provide comparable phase noise performance without using spiral inductors and transformers. The performance of the modulator is assessed using a 1.6-GHz QPSK base-band modulator implemented in TSMC 0.18-μm 1.8-V CMOS technology and analyzed using SpectreRF from Cadence Design Systems with BSIM3v3 device models. The total transistor area and power consumption of the modulator are 2840 μm2 and 30 mW, respectively. The phase noise of the quadrature oscillator is - 110 dBc/Hz at 500-kHz frequency offset.

Original languageEnglish
Pages (from-to)11-15
Number of pages5
JournalIEEE Transactions on Circuits and Systems II: Express Briefs
Issue number1
Publication statusPublished - 2008
Externally publishedYes


  • Bandwidth
  • CMOS integrated circuits
  • Modulation
  • Oscillators
  • Phase noise
  • Phase shift keying
  • Windings


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