Abstract
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 language | English |
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Article number | 9540036 |
Pages (from-to) | 3784-3798 |
Number of pages | 15 |
Journal | IEEE Journal of Solid-State Circuits |
Volume | 56 |
Issue number | 12 |
DOIs | |
Publication status | Published - 2021 |
Bibliographical note
Accepted Author ManuscriptKeywords
- Balanced power amplifier (PA)
- calibration free
- direct upconverter
- double-quadrature
- image-rejection ratio (IRR)
- mutual-coupling
- series-Doherty PA
- transmitter (TX)