A 2-V low-power CMOS direct-conversion quadrature modulator with integrated quadrature voltage-controlled oscillator and RF amplifier for GHz RF transmitter applications

Chung-Yu Wu*, Hong Sing Kao

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

A compact low-voltage low-power CMOS direct-conversion quadrature modulator with integrated quadrature voltage-controlled oscillator (VCO) and radio frequency (RF) amplifier for wireless transmitter applications is proposed and analyzed. By applying both baseband input signals with quadrature phases and quadrature local oscillator (LO) signals to a set of combiners, the quadrature modulation functions can be implemented. The low-power operation is enabled by the current reuse technique used among quadrature modulator, quadrature VCO, and RF amplifier. Because only two transistors and one resistor are cascoded in the critical path of the proposed quadrature modulator between power supply and ground, the supply voltage can be as low as 1.5 V. The proposed circuit structure is used to design a quadrature modulator chip for 1.9-GHz digital enhanced cordless telecommunications (DECT) transmitter applications. The experimental chip is fabricated by using 0.35-μm n-well double-poly-triple-metal (DPTM) CMOS technology. The power dissipation is only 18 mW under 2-V power supply voltage. The on-chip quadrature VCO can provide highly accurate quadrature signals without any phase tuning or trimming. The frequency tuning range of the quadrature VCO is 280 MHz from 1.89 to 2.17 GHz at 2-V supply voltage. Due to small mismatch among quadrature signal paths, the measured image ratio is below -42 dBc under 2-V supply voltage when the desired upper side-band (USB) is set at 2 GHz and -51 dBc under 3-V supply voltage when the desired USB at 1.94 GHz. At 2-V supply voltage, the measured LO leakage is -48 dBc. Moreover, the measured second-order intermodulation and third-order intermodulation are less than -46 dBc.

Original languageEnglish
Pages (from-to)123-134
Number of pages12
JournalIEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing
Volume49
Issue number2
DOIs
StatePublished - 1 Feb 2002

Keywords

  • CMOS technology
  • Current reuse
  • Direct-conversion
  • Low-power
  • Low-voltage
  • Quadrature modulator
  • Quadrature voltage-controlled oscillator (VCO)
  • RF amplifier
  • Radio frequency (RF)
  • Transmitter
  • Wireless communication

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