Broadband Millimeter-Wave CMOS Transceiver for 5G Mobile Communication and Radar-Based Sensing

Abstract

To meet the ever-growing demand for higher data rates in communication networks and higher range and velocity resolutions in automotive radar sensors, fifth-generation (5G) new radio (NR) transceivers and radars used in autonomous vehicles use spectrally efficient modulation formats with large channel bandwidths available at millimeter wave (mm-wave) frequencies. However, designing energy-efficient broad-band transceivers with low manufacturing cost at mm-wave frequencies is extremely challenging because of the performance degradation of integrated circuit (IC) components, impairments due to packaging, and increased free-space path loss. This thesis presents a high-performance, compact, low-cost mm-wave transceiver solution for 5G NR and automotive radar sensors.

A 28-GHz transceiver based on the local-oscillator (LO) phase-shifting architecture enabling gain-invariant phase tuning is designed in a 65-nm CMOS technology with wirebond-based packaging, enabling low manufacturing cost. The transceiver chip consists of a transmitter, a receiver, and an LO phase-shifting and distribution network. The transmitter employs an energy-efficient architecture based on direct-digital RF modulators (DDRMs) using digital-to-RF converters (DRFCs) to support BPSK, QPSK, 16-QAM, and 64-QAM modulation formats in 4 GHz of channel bandwidth accommodating both 5G and radar waveforms. The receiver is based on the complex-baseband zero-IF architecture using an active downconversion mixer with a transimpedance amplifier (TIA) load with up to 4 GHz of IF bandwidth. The downconverted signal is dynamically amplified by broad- band variable gain amplifiers (VGAs) based on Cherry-Hooper gain stages to compensate for the quadrature gain mismatch and relax the linearity requirement for analog-to-digital converters (ADCs). The in-phase and quadrature-phase LO signals are generated on-chip using a transformer-based quadrature hybrid driven by a coarse/fine tunable LC tank based phase shifter. The transceiver utilizes low-k transformer based fourth order networks for broadband input and output matching of the low-noise amplifier (LNA) and power amplifier (PA) as well as for interstage matching. The mm-wave chip-to-board interfaces are optimized using a scalable broadband model for wirebond interconnects developed using experimental data.

A broadband dielectric characterization technique using coplanar waveguide (CPW) based test structures is developed to extract the frequency-dependent dielectric properties of the silicon substrate, typically not characterized by the foundry. This enhances the accuracy of the electromagnetic (EM) models of on-chip passive devices and interconnect parasitics, and consequently, the performance of the transceiver.