The quartz crystal (XTAL) oscillator is one of the last components in electronic systems that has yet to be integrated. Consequently, integrating crystal oscillators (XOs) has become a research target for the developers of MEMS microresonators. Recent and representative examples of MEMS oscillators include [1] and [2]. Unfortunately, MEMS microresonators introduce certain challenges including limited power-handling capability [2]. The limitations of MEMS have resulted in recent work, e.g., [3] and [4], exploring the limits of compensated CMOS oscillators as an alternative solution. The advent of RF CMOS circuits and associated advances in CMOS process technology have enabled the development of low-noise integrated LC oscillators (LCOs) [5], which are suitable for replacing XOs in USB applications [3]. This work demonstrates a self-referenced CMOS LCO, or CMOS harmonic oscillator (CHO), that exhibits 90ppm total frequency error over process, bias and temperature, thus making it suitable for replacing XOs in many applications. Additionally, the clock generator can be configured to produce a number of different output frequencies, has 1/4 of the frequency error of the oscillator in [3] and includes a direct modulation technique enabling SSCG. Figure 19.6.1 illustrates the CHO, which exhibits a self-oscillation frequency of 960MHz. A 13b binary-weighted array of MiM capacitors and ring-transistor switches enables the oscillation frequency to be trimmed ±6% with 15ppm resolution. The trimming coefficient is determined during test via an on-chip frequency-locked loop (FLL), in which deep counters for the CHO and a precision reference clock discriminate the frequency error and update the CHO trimming coefficient, as described in [3]. The FLL is controlled by on-chip logic that converges to the optimal trimming coefficient within 100ms by using a binary search algorithm. Additionally, the thin-film capacitor array enables direct modulation of the CHO frequency via a frequency-divided image of itself, thus permitting SSCG without a modulating PLL. The spread rate and depth are controlled digitally by the divide ratio utilized to generate the modulating clock and the capacitor array step size, respectively. The TC of the CHO, which is nearly linear and negative due to the coil loss [3], is compensated via a programmable 6b accumulation-mode MOS (A-MOS) varactor array. When compensation is enabled, the appropriate varactors are connected to a positive linear temperature-dependent voltage, v ctrl (T), and the remaining varactors are connected to the 2.5V power supply. Amplitude control (AC) and common-mode control (CMC) loops minimize frequency drift due to bias variation and device degradation. Long-term frequency drift, or aging, can originate from oxide breakdown and hot carrier mechanisms. Addressing these mechanisms, the AC loop limits the maximum voltage excursion across the passive and active devices, and the CMC loop prevents frequency drift due to device threshold voltage shift induced by hot carriers trapped in th...

No abstract

We report a case of tumor implantation along the needle tract after percutaneous biopsy of Wilms tumor. This is a rare but important complication in the management of Wilms tumor.

Vietnamese women living in the United States have a cervical cancer incidence rate that is five times that of White women. The low rate of cervical cancer screening among this high-risk population contributes to this disparity. In 2004, the National Cancer Institute collaborated with the Vietnamese American Medical Association to conduct a short needs assessment questionnaire (Pap Test Barriers Questionnaire for Health Care Providers) among its members to assess provider views about cervical cancer, barriers to Pap testing among Vietnamese women living in the United States, and types of patient education materials needed to help motivate Vietnamese women to receive a Pap test. Information from the questionnaire was used to inform development of a brochure and identify additional strategies to enhance outreach to Vietnamese women and providers. Almost all of the respondents (95%) thought that Pap tests were “very important” in the early detection of cervical cancer in Vietnamese women. In addition, knowledge about the importance of Pap tests was identified as the most influential factor for Vietnamese women not seeking a Pap test. Print materials that included both English and Vietnamese translations in the same publication were cited as a preferred communication tool. Further, health education through Vietnamese media was recommended as a primary strategy for reaching women with educational messages. Findings from this needs assessment contributes to a larger formative research effort to build NCI’s cervical cancer education program within its Office of Education and Special Initiatives.