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## Abstract

Improving the energy efficiency of wireless communication transmitters is an increasingly important target now that millimeter-wave (mm-wave) frequencies are being used. To improve the efficiency compared with classical transmit architectures that use a class A/AB power amplifier (PA), we propose here a polar transmitter that operates around 60 GHz. This transmitter is based on a radio frequency digital-to-analog converter (RF-DAC). This RF-DAC uses a switching scheme that greatly reduces signal leakage via disabled unit cells which greatly improves the output signal quality. In this way, this polar transmitter can process higher order modulation schemes at mm-wave frequencies, such as a 64-QAM, where an excellent error vector magnitude (EVM) specification is required. This mm-wave polar transmitter, prototyped in a 28-nm CMOS technology, consists of a digital PA (DPA) using 7-bit RF-DACs for amplitude modulation (AM),and an active phase shifter (PS) using two 7-bit variable gain amplifiers (VGAs) with an in-phase quadrature (IQ)-hybrid for phase modulation (PM). All the amplitude and phase samples for the RF core are accessed from an on-chip memory. Static measurements show a power gain of 21.5 dB, a saturated output power (<inline-formula> <tex-math notation="LaTeX">$P_{\text{sat}}$</tex-math> </inline-formula>) of 12.6 dBm, and a peak drain efficiency of 25.9<inline-formula> <tex-math notation="LaTeX">$\%$</tex-math> </inline-formula> at 64 GHz. A 10.56-Gb/s 64-QAM signal at <inline-formula> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula>27.8-dB EVM is demonstrated with measured core and system efficiencies of 8.5<inline-formula> <tex-math notation="LaTeX">$\%$</tex-math> </inline-formula> and 3.9<inline-formula> <tex-math notation="LaTeX">$\%$</tex-math> </inline-formula>, respectively. The transmitter consumes 159-mA current from a 0.9-V supply.

Original language | English |
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Pages (from-to) | 1-13 |

Number of pages | 13 |

Journal | IEEE Journal of Solid-State Circuits |

Early online date | 23 Feb 2023 |

DOIs | |

Publication status | E-pub ahead of print - 23 Feb 2023 |

### Bibliographical note

Publisher Copyright:IEEE

Copyright:

Copyright 2023 Elsevier B.V., All rights reserved.

## Keywords

- Amplitude modulation (AM)
- digital polar
- driver
- leakage
- on-chip memory
- phase modulation (PM)
- radio frequency digital-to-analog converter (RF-DAC)
- switch
- transmitter

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