A Millimeter-Wave Mutual-Coupling-Resilient Double-Quadrature Transmitter for 5G Applications

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This article presents a wideband energy-efficient transmitter (TX) for 5G mm-wave phased-array systems. It features an advanced double-quadrature direct upconverter (DQ-DUC) to improve its in-band linearity and spectral purity. The proposed TX architecture incorporates an efficiency-enhanced balanced power amplifier (EEBPA) that mitigates VSWR fluctuations in phased-array systems while enhancing efficiency at power back-off (PBO). The EEBPA comprises two identical series-Doherty power amplifiers (PAs) combined through a quadrature hybrid coupler forming a balanced PA. The proposed DQ-DUC consists of a pair of I/Q modulators and the proposed EEBPA's quadrature combiner to further suppress the I/Q image. To verify the proposed techniques, a 40-nm CMOS prototype is implemented. It delivers 20 dBm P 1 dB with 40%/31% drain efficiency at P 1 dB/6-dB PBO. The measured TX output reflection coefficient is better than-18 dB over a 22.5-30-GHz band. Its intrinsic LO feedthrough and image-rejection ratio for a 100-MHz tone spacing over a 24-30-GHz band are better than-45 dBc/50 dB, respectively, without calibration. The average error vector magnitude (EVM) is better than-27.1 dB without digital pre-distortion for an eight-carrier '100-MHz 64-QAM OFDM' signal with an 800-MHz aggregated bandwidth while generating an average output power of 8.4 dBm with 10.8% drain efficiency. Its maximum forward-power/EVM deviations are better than 0.3/1.65 dB, respectively, for a '100-MHz 64-QAM' signal under a voltage standing wave ratio of 3.

Original languageEnglish
Article number9540036
Pages (from-to)3784-3798
Number of pages15
JournalIEEE Journal of Solid-State Circuits
Issue number12
Publication statusPublished - 2021


  • Balanced power amplifier (PA)
  • calibration free
  • direct upconverter
  • double-quadrature
  • image-rejection ratio (IRR)
  • mutual-coupling
  • series-Doherty PA
  • transmitter (TX)


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