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Open Access Publications from the University of California

Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UC Berkeley Electronic Theses and Dissertations (2011)

There is a growing interest in the use of the 7 GHz of unlicensed bandwidth around 60 GHz for high-speed wireless data transfers. Complementary metal-oxide-semiconductor (CMOS) radio frequency (RF) circuits have been demonstrated to effectively operate in this band, but the challenge remains to design a complete high data-rate, energy-efficient system. With data rates of several Gb/s and short wavelengths, the baseband signal processing that compensates for the distortion of the wireless channel presents a significant challenge. This work demonstrates the design of a power-efficient baseband at different levels of abstraction from the algorithm level down to the transistor level.

A method for optimizing the equalizer architecture under power and bit-error rate (BER) constraints has been developed. This method has been used to optimize the number of equalizer taps and the distribution of signal processing between analog and digital domains. Two chips were built to demonstrate the methodology based on the IEEE wireless personal area network (WPAN) standard.

The first, fully-digital chip implements a single-carrier demodulator that minimizes the power consumption using a parallelized distributed arithmetic architecture. A 2mm x 2mm test chip in a 65 nm CMOS process implements a 6-tap feedforward and 32-tap feedback equalizer for binary phase-shift keying (BPSK) that can be configured to cancel the response of up to 72 symbols while consuming 5.6mW at 2 Gb/s throughput.

The second 1.86mm x 1.86mm chip implements a reconfigurable 4-bit ADC and 6-tap analog equalizer in addition to the digital equalizer for quadrature phase-shift keying (QPSK) demodulation. The analog preprocessor is measured to consume 1.3mW for the driver and 300 uW/tap for the analog equalization. The ADC power consumption varies from 1.2mW to 3.8mW depending on the resolution at 1.76 Gs/s. It is shown that, given a BER requirement,

the mixed-signal reconfigurable receiver architecture can reduce the total link power consumption compared to a full-digital fixed transceiver depending on the propagation condition.

    Cover page: Power-efficient Design of Multi-Gbps Wireless Baseband
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2023)
    The engineering of atomically-precise nanopores in two-dimensional materials presents exciting opportunities for both fundamental science studies as well as applications in energy, DNA sequencing, and quantum information technologies. The exceptional chemical and thermal stability of hexagonal boron nitride (h-BN) suggest that exposed h-BN nanopores will retain their atomic structure even when subjected to extended periods of time in gas or liquid environments. Here we employ transmission electron microscopy to examine the time evolution of h-BN nanopores in vacuum and in air and find, even at room temperature, dramatic geometry changes due to atom motion and edge contamination adsorption, for timescales ranging from one hour to one week. The discovery of nanopore evolution contrasts with general expectations and has profound implications for nanopore applications of two-dimensional materials.
      Cover page: Evolution of nanopores in hexagonal boron nitride
      • Article
      • Peer Reviewed
      UC Berkeley Previously Published Works (2022)
      The colour centre platform holds promise for quantum technologies, and hexagonal boron nitride has attracted attention due to the high brightness and stability, optically addressable spin states and wide wavelength coverage discovered in its emitters. However, its application is hindered by the typically random defect distribution and complex mesoscopic environment. Here, employing cathodoluminescence, we demonstrate on-demand activation and control of colour centre emission at the twisted interface of two hexagonal boron nitride flakes. Further, we show that colour centre emission brightness can be enhanced by two orders of magnitude by tuning the twist angle. Additionally, by applying an external voltage, nearly 100% brightness modulation is achieved. Our ab initio GW and GW plus Bethe-Salpeter equation calculations suggest that the emission is correlated to nitrogen vacancies and that a twist-induced moiré potential facilitates electron-hole recombination. This mechanism is further exploited to draw nanoscale colour centre patterns using electron beams.
        Cover page: Tuning colour centres at a twisted hexagonal boron nitride interface
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