40 Gbit/s limiting output buffer in 80 nm CMOS

A 40 Gbit/s 1V limiting output buffer for an AC-coupled 50 /spl Omega/ load with a differential output swing of 660 mV and a gain of 18 dB is presented. A power consumption of only 24 mW and a simulated risetime of 11 ps are achieved by means of a systematic buffer optimisation.     

Reading handwritten digits: a ZIP code recognition system

A neural network algorithm-based system that reads handwritten ZIP codes appearing on real US mail is described. The system uses a recognition-based segmenter, that is a hybrid of connected-components analysis (CCA), vertical cuts, and a neural network recognizer. Connected components that are single digits are handled by CCA. CCs that are combined or dissected digits are handled by the vertical-cut segmenter. The four main stages of processing are preprocessing, in which noise is removed and the digits are deslanted, CCA segmentation and recognition, vertical-cut-point estimation and segmentation, and directly lookup. The system was trained and tested on approximately 10000 images, five- and nine-digit ZIP code fields taken from real mail     

Correction of birefringence and thermal lensing in nonreciprocal resonators by use of a dynamic imaging mirror

Enhanced correction of thermally induced birefringence in the presence of strong single-pass, azimuthally dependent bipolar focusing was achieved in single-rod laser oscillators by use of an adaptive optic rear mirror with image relay and aberration correction capabilities. Together with a Faraday rotator, the imaging variable radius mirror was successfully tested in stable and unstable Nd:Cr:GSGG power oscillators under variable pump power conditions from 0 to 800 W. Birefringence correction in the absence of ray retracing was achieved.     

Thermally boosted pumping of neodymium lasers

Pumping at 885 nm from thermally excited ground-state levels directly to the Nd:YAG upper lasing level is experimentally demonstrated by use of a Ti:sapphire pump laser. This approach utilizes thermal energy contained within the laser medium to provide part of the pump energy required to achieve population inversion. Slope efficiency increased by 12% compared with traditional pump band excitation (lambda(pump) = 808 nm) and by 7% compared with ground-state direct pumping (lambda(pump) = 869 nm). The combined transition from the first and second thermally excited Stark components of the ground state ((4)I(9/2)) to the upper lasing level ((4)F(3/2)) has characteristics that make thermally boosted pumping a suitable candidate for use with diode lasers: reasonable absorption (1.8 cm(-1)) and bandwidth (2.7 nm FWHM). A model suggests that, compared with traditional 808-nm pumping, heat could be reduced by 40% by use of thermally boosted pumping.     

Integrated Active Pulsed Reflector for an Indoor Local Positioning System

This paper presents an indoor localization system based on a frequency modulated continuous wave radar in the industrial–scientific–medical band at 5.8 GHz. An integrated active pulsed reflector behaves as a backscatter by regenerating the incoming phase with phase coherent startup at a constant frequency. The base station (BS) determines the distance to this reflector with a round-trip time-of-flight measurement. The active pulsed reflector is built around a switchable and tunable oscillator. The circuit has been fully integrated in a 0.18-$mu{hbox{m}}$ CMOS technology. Outdoor measurements revealed a positioning accuracy of 15 cm, while in a harsh multipath environment with omnidirectional antennas a positioning accuracy of 32.88 cm was measured. The localization system is capable of detecting multiple reflectors at the same time, and no synchronization between BSs is needed.      

A low supply voltage SiGe LNA for ultra-wideband frontends

A low-power low-noise amplifier (LNA) for ultra-wideband (UWB) radio systems is presented. The microwave monolithic integrated circuit (MMIC) has been fabricated using a commercial 0.25-/spl mu/m silicon-germanium (SiGe) bipolar CMOS (BiCMOS) technology. The amplifier uses peaking and feedback techniques to optimize its gain, bandwidth and impedance matching. It operates from 3.4 to 6.9GHz, which corresponds with the low end of the available UWB radio spectrum. The LNA has a peak gain of 10dB and a noise figure less than 5dB over the entire bandwidth. The circuit consumes only 3.5mW using a 1-V supply voltage. A figure of merit (FoM) for LNAs considering bandwidth, gain, noise, power consumption, and technology is proposed. The realized LNA circuit is compared with other recently published low-power LNA designs and shows the highest reported FoM.     

Multiwavelength performance of an apodized acousto-optic switch

Use of the acousto-optic switch as a wavelength-routing element in WDM networks is described. The need for deep isolation between wavelength channels has resulted in the search for efficient sidelobe suppression techniques such as tapering of the acousto-optic profile by imbedding an optical waveguide in one arm of an acoustic directional coupler. The theory of sidelobe-suppression in the optical transmission function of a SAW-coupler apodized acousto-optic filter is presented. A low-sidelobe SAW-coupler-apodized AO switch was fabricated and used in a 1.5 micron multi-wavelength WDM switching demonstration employing four 4 nm-spaced optical channels. Crosstalk was below -19 dB for single wavelength selection and below -15 dB for arbitrary routing patterns, a dramatic improvement over unapodized AO switches     

Comparison of simulation and measurement of dynamic fiber-coupling effects for high-speed multimode VCSELs

Static and dynamic measurements are performed with GaAs oxide-confined vertical-cavity surface-emitting lasers (VCSELs), using multimode fibers with a core diameter of 50 and 62.5 /spl mu/m and different numerical apertures (NAs). They show that a small NA can have a severe impact on the eye opening and thus also on the bit-error rate. The measurements are analyzed with a spatiotemporal two-dimensional (2-D) multimode VCSEL model. The required parameter extraction for the model is verified with small- and large-signal measurements. The analysis shows that the change of the eye opening can be explained by the interaction between the mode- and the current-injection profile, carrier diffusion, and intermodal gain compression (IGC). IGC increases differences in the modal power distribution caused by the interaction between the mode profiles and the current-injection profile. Carrier diffusion is able to compensate these increased differences of the modal power distribution. Its impact, however, on dynamic changes caused by IGC is moderate.     

30-40-GHz drain-pumped passive-mixer MMIC fabricated on VLSI SOI CMOS technology

In this paper, a passive down mixer is proposed, which is well suited for short-channel field-effect transistor technologies. The authors believe that this is the first drain-pumped transconductance mixer that requires no dc supply power. The monolithic microwave integrated circuit (MMIC) is fabricated using digital 90-nm silicon-on-insulator CMOS technology. All impedance matching, bias, and filter elements are implemented on the chip, which has a compact size of 0.5 mm/spl times/0.47 mm. The circuit covers a radio frequency range from 30 to 40 GHz. At a RF frequency of 35 GHz, an intermediate frequency of 2.5 GHz and a local-oscillator (LO) power of 7.5 dBm, a conversion loss of 4.6 dB, a single-sideband (SSB) noise figure (NF) of 7.9 dB, an 1-dB input compression point of -6 dBm, and a third-order intercept point at the input of 2 dBm were measured. At lower LO power of 0 dBm, a conversion loss of 6.3 dBm and an SSB NF of 9.7 dB were measured, making the mixer an excellent candidate for low power-consuming wireless local-area networks. All results include the pad parasitics. To the knowledge of the authors, this is the first CMOS mixer operating at millimeter-wave frequencies. The achieved conversion loss is even lower than for passive MMIC mixers using leading edge III/V technologies, showing the excellent suitability of digital CMOS technology for analog circuits at millimeter-wave frequencies.