Publication Details
Overview
 
 
Johan Nguyen
 

Thesis

Abstract 

The fifth-generation (5G) wireless communication technology was deployed in 2019 to meet the increasing global demands for high-speed connectivity. The radio frequency spectrum is progressively expanding to millimeter-wave ranges to meet the growing demand for mobile broadband applications. The transmitter typically consumes most of the power in the electronics used in a wireless communication link. The reason is that for a high-datarate link, the transmitter needs to operate without generating much nonlinear distortion, which typically comes with low efficiency. This Ph.D. work focuses on designing and calibrating digital polar transmit architectures, which could bring a high data rate for power consumption lower than with a classical architecture that uses (quasi-)linear power amplifiers. The modulated signal is first split into an amplitude and phase path in a digital polar transmitter. In this thesis, a 60-GHz polar transmitter is demonstrated in 28-nm CMOS. The phase modulation is applied via phase modulators that act on a 60-GHz carrier. This phase-modulated carrier is then fed to a radio-frequency digital-to-analog converter (RF-DAC) whose digital input is proportional to the wanted amplitude. Compared to earlier designs, the RF-DAC in this work does not suffer from leakage at lower codes, enabling higher-order modulations and yielding higher data rates. The polar transmitter chip achieves a raw data rate of 10.52 Gbit/s using 64-QAM modulation. The impedance matching networks needed for efficient power transfer at the input and output of each active (sub)circuit are realized with transformers. In this work, a design flow based on ABCD matrices has been developed to speed up the design of these. The same framework is later used to design a transmit/receive switch. Synchronization between the amplitude and phase paths of a polar transmitter is vital. A non-iterative method is proposed in this work to perform this synchro- nization. This method is then extended to retrieve AM-AM and AM-PM distortion caused by the variable-gain amplifiers used in the polar transmitter. The method can also be used to estimate the IQ imbalance of the passive hybrid part of the polar transmitter. By calculating with this method an equalization filter for the phase samples, higher modulation bandwidths can be achieved. Theoretically, it could enable data rates in the order of 40 Gbit/s.

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