Kaushik Dasgupta

Integrated Self-Healing for mm-Wave Power Amplifiers

Self-healing as a technique for improving performance and yield of millimeter-wave power amplifiers (PAs) against process variation and transistor mismatch, load impedance mismatch, and partial and total transistor failure is described and investigated. A 28-GHz PA is presented with three types of sensors, two types of actuators, data converters, and a digital algorithm block that are all integrated on a single chip to show the validity of the technique. Two algorithms are implemented to either maximize output power or to minimize dc power for a desired output power. Measurements from 20 chips show increased RF output power up to 3 dB or reduced dc power by 50% in backoff with a 50-Ω load. Self-healing with up to 4-1 voltage standing-wave ratio load impedance mismatch is verified and linear operation under nonconstant envelope modulation is shown to improve with healing. Self-healing after laser cutter induced transistor failure is verified and increases RF output power by up to 5.4 dB. The aggregate yield of the PA across several representative specifications is increased from 0% to 80% with self-healing.

A fully-integrated self-healing power amplifier

A fully-integrated self-healing mm-wave power amplifier heals process variation, load mismatch, and transistor failure with on-chip sensors, actuators and an integrated digital algorithm ASIC without external calibration. Measurements of 20 chips showed increased RF power up to 3dB, or reduced DC power by 50% in backoff at 28 GHz. Healing 4-1 VSWR load mismatch for RF and DC power improvement was verified, and healing after laser induced transistor failure increased RF power up to 4.8dB.

On-chip sensing and actuation methods for integrated self-healing mm-wave CMOS power amplifier

This paper presents various low power, compact, low insertion-loss sensors with digitized ADC output and digitally controlled actuation methods for on-chip characterization and healing of a mm-Wave power amplifier. We demonstrate low insertion loss (0.4dB) RF sensors which measure true input and output power in presence of load variations and very low-headroom (10–30mV) DC sensors with built-in regulators and thermal sensors as methods for measuring PA efficiency. All sensor outputs are digitized by a SAR-based ADC for communication with a central digital core. The paper also presents digitally controlled combiner tuning and PA bias actuation. The circuits are implemented in 45 nm SOI CMOS and enable full on-chip digitally controlled characterization and actuation of the PA with a power overhead of less than 6%.

Dynamic Polarization Control of Two-Dimensional Integrated Phased Arrays

Simultaneous two-dimensional (2-D) beam steering and dynamic polarization control (DPC) of the radiated electric field in 2-D phased arrays ensure polarization matching between the transmitter and receiver antennas in both fixed and mobile wireless systems. Polarization matching is maintained regardless of the polarization, orientation, and location of the receiver antenna in space within the 2-D steering range of the transmitter. This work implements a fully integrated 2 × 2 DPC phased-array transmitter in a 32-nm CMOS silicon-on-insulator process, radiating at 122.9 GHz. It achieves a maximum effective isotropic radiated power of +12.3 dBm in the broadside direction and enables polarization angle control of the radiated linear and elliptical polarizations across the full range of 0 ° to 180 ° with tunable axial ratio down to 1.2 dB to achieve circular polarization and the ability to steer the radiated beam up to 15 ° in both dimensions.

A broadband self-healing phase synthesis scheme

This paper presents a full-range broadband phase synthesis scheme with autonomous phase correction functionality. The on-chip phase measurement is achieved by a set of on-chip LO self-/inter-mixing testing sequences, which eliminates the need for auxiliary test tones. As a design example, a 2-to-6GHz quadrature phase synthesis system in a 65nm CMOS is demonstrated. The phase self-healing scheme achieves an RMS phase error of less than 0.6° and a full 360° interpolation within the entire band.

Closed-loop spurious tone reduction for self-healing frequency synthesizers

On-chip spurious tone detection and correction in an 8–12 GHz CMOS synthesizer is used to automatically reduce spurious output tones at different offset frequencies by up to 20dB. Using synchronous detection, sensitivity is limited by detection time only. The presented methods are generally applicable to frequency synthesizers and phased-locked loops in various applications.

A mm-Wave Segmented Power Mixer

The segmented power-mixer array based mm-wave power generation architecture is demonstrated to be an energy-efficient technique for generating high-speed nonconstant envelope modulations. High output power levels are achieved by efficiently combining power from several power mixers using an area efficient dual-primary distributed active transformer. The segmented scheme leads to back-off efficiency improvements while simultaneously providing direct envelope modulation eliminating the need for high-speed high-efficiency supply modulators. The power mixer is implemented in a 32-nm silicon-on-insulator CMOS process and provides a peak output power of 19.1 dBm at 51 GHz with a drain efficiency of 14.2% and a peak power-added efficiency of 10.1%. High-speed constant (binary phase-shift keying, quadrature phase-shift keying), as well as nonconstant envelope modulations ( m-amplitude shift keying, quadrature amplitude modulation) show the versatility of the architecture towards spectrally efficient modulation schemes. Reliability against segment breakdown over long periods of time at 30% higher supply voltages has also been demonstrated.

A 25 Gb/s 60 GHz digital power amplifier in 28nm CMOS

This paper presents a 60 GHz class-E digital power amplifier (DPA) that generates energy-efficient, non-constant envelope modulations up to 25 Gb/s. The DPA achieves a peak drain efficiency of 17.7% at a Vsat of 7.4 dBm. By means of direct digital amplitude modulation of the 6-bit output stage, the DPA produces error-free, high-order constellations (16-QAM, 32-QAM, 64-QAM) up to 5 GSym/s with error vector magnitudes (EVMs) <-26 dB. Compared to prior 60 GHz DPAs, >3.5X higher data rates at comparable average efficiencies is achieved.

A 2×2 Dynamic Polarization-Controlling integrated phased array

Radiator arrays with Dynamic Polarization Control (DPC) and 2D beam steering enable polarization matching to the receiver antenna regardless of its polarization, orientation, and location. A fully integrated 122.9 GHz 2×2 DPC multi-port driven phased array radiates all linear polarizations (0°-180° polarization angles) with axial ratios above 14 dB, and controls the axial ratio from 1.2 dB (circular) to 17.8 dB (linear) with a maximum EIRP of +12.3 dBm and 2D beam steering of up to 15°.

Holistic Approaches for Power Generation, Linearization, and Radiation in CMOS

The field of wireless communications has experienced an exponential growth over the past four decades, going from the realm of science fiction to becoming so ubiquitous and natural that the younger generations have a difficult time imagining a world without it. This has been made possible through many breakthroughs in our understanding of the nature of wireless communications and, more importantly, numerous innovative enabling technologies that have made personal wireless communication an everyday reality.