Design of VCOs in Deep Sub-micron Technologies

This work will present a more accurate frequency prediction model for single-ended ring oscillators (ROs), a case-study comparing different ROs, and a design method for LC voltage-controlled oscillators (LCVCOs) that uses a MATLAB script based on analytical equations to output a graphical design space showing performance characteristics as a function of design parameters. Using this method, design trade-offs become clear, and the designer can choose which performance characteristics to optimize. These methods were used to design various topologies of ring oscillators and LCVCOs in the GlobalFoundries 28 nm HPP CMOS technology, comparing the performance between different topologies based on simulation results. The results from the MATLAB design script were compared to simulation results as well to show the effectiveness of the design methods. Three varieties of 5 GHz voltage controlled ring oscillators were designed in the GlobalFoundries 28 nm HPP CMOS technology. The first is a low current low dropout regulator (LDO) tuned ring oscillator designed with thin oxide devices and a 0.85 V supply. The second is a high current LDO-tuned ring oscillator designed with medium oxide devices and a 1.5 V supply. The third is varactor-tuned ring oscillator with no LDO, and 0.85 V supply. Performance comparison of these ring oscillator systems are presented, outlining trade-offs between tuning range, phase noise, power dissipation, and area. The varactor-tuned ring oscillator exhibits 8.89 dBc/Hz (with power supply noise) and 16.27 dBc/Hz (without power supply noise) improvement in phase noise over the best-performing LDO-tuned ring oscillator. There are advantages in average power dissipation and area for a minimal tradeoff in tuning range with the varactor-tuned ring oscillator. Four multi-GHz LCVCOs were designed in the GlobalFoundries 28 nm HPP CMOS technology: 15 GHz varactor-tuned NMOS-only, 9 GHz varactor-tuned self-biased CMOS, 14.2 GHz digitally-tuned NMOS-only, and 8.2 GHz digitally-tuned self-biased CMOS. As a design method, analytical ex-pressions describing tuning range, tank amplitude constraint, and startup condition were used in MATLAB to output a graphical view of the design space for both NMOS-only and CMOS LCVCOs, with maximum varactor capacitance on the y-axis and NMOS transistor width on the x-axis. Phase noise was predicted as well. In addition to the standard varactor control voltage tuning method, digitally-tuned implementations of both NMOS and CMOS LCVCOs are presented. The performance aspects of all designed LCVCOs are compared. Both varactor-tuned and digitally-tuned NMOS LCVCOs have lower phase noise, lower power consumption, and higher tuning range than both CMOS topologies. The varactor-tuned NMOS LCVCO has the lowest phase noise of -97 dBc/Hz at 1 MHz offset from 15 GHz center frequency, FOM of -172.20 dBc/Hz, and FOMT of -167.76 dBc/Hz. The digitally-tuned CMOS LCVCO has the greatest tuning range at 10%. Phase noise is improved by 3 dBc/Hz with the digitally-tuned CMOS topology over varactor-tuned CMOS

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe