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Indirect modulation of fractional-N synthesizers is an energy-efficient architecture capable of moderate data rates, and is well-suited for use in sensor networks or WLAN. Although the architecture is used primarily at low RF frequencies, the capability for fractional-N synthesizers at Ku-band and above currently exist in available silicon technology. Recent demonstrations at 10-25GHz show promising results, although power consumption at this higher frequency remains high for small batterypowered devices. This work implements a fully-integrated fractional-N synthesizer optimized for power efficient modulation at 15.8 to 18.9GHz with an 80MHz reference. Binary and 4-ary FSK modulation of up to 8Mbps is achieved while consuming 16mW in IBM 0.18µm SiGe BiCMOS.

This paper introduces the Watermark Imaging System (WImSy) which can be used to photograph, document, and study sheets of paper. The WImSy provides surface images, raking light images, and transmitted light images of the paper, all in perfect alignment. We develop algorithms that exploit this alignment by combining several images together in a process that mimics both the “surface image removal” technique and the method of “high dynamic range” photographs. An improved optimization criterion and an automatic parameter selection procedure streamline the process and make it practical for art historians and conservators to extract the relevant information to study watermarks. The effectiveness of the method is demonstrated in several experiments on images taken with the WImSy at the Metropolitan Museum of Art in New York and at the Getty Museum in Los Angeles, and the results are compared with manually optimized images.

This work presents the design and measurement of a 2Mbps BFSK transceiver at 1.35 to 1.75GHz for use in wireless sensor node applications. The receiver is a direct conversion architecture and has a sensitivity of -74dBm at 2Mbps and consumes 8.0mW. The transmitter generates orthogonal BFSK modulation through the use of digital pre-emphasis of the synthesizer frequency control word and consumes 9.7mW including the power amplifier. The transmitter delivers >3dBm of output power for a total transmitter power efficiency of 23% and a transmitter FOM of 4.85nJ/bit at 2Mbps.