Phase-Error Measurement and Compensation in PLL Frequency Synthesizers for FMCW Sensors—I: Context and Application

The synthesis of linear frequency sweeps or chirps is required, among others, in frequency-modulated continuous-wave radar systems for object position estimation. Low phase and frequency errors in sweeps with high bandwidth are a prerequisite for good accuracy and resolution, but, in certain applications where high measurement rates are desired, the additional demand for short sweep cycles has to be met. Transient phenomena in dynamic synthesizers as well as nonlinear system behavior usually cause unknown phase errors in the system output. For the class of phase-locked-loop (PLL)-based frequency synthesizers, a novel output phase-measurement method and dedicated circuitry are proposed that allow significant reduction of phase errors by adaptive input predistortion. The measurement procedure is implemented within the PLL control circuitry and does not require external equipment. The application of this method to PLL system identification and linearization of extremely short frequency sweeps is shown     

Impact of Preferential P-Diffusion Along the Grain Boundaries on Fine-Grained Polysilicon Solar Cells

Thin-film polysilicon solar cells are a promising low-cost alternative for bulk silicon solar cells due to their reduced material thickness. Recently, we showed that the use of an amorphous silicon/polycrystalline silicon heterojunction emitter instead of a diffused homojunction emitter led to a boost in the open-circuit voltage by 90 mV. Now, we present a full evidence that shows that this improvement is related to the absence of dopant smearing along the grain boundaries. By using scanning spreading resistance microscopy, we found an enlargement of the junction area by a factor of five in case of a homojunction. The tips of the dopant spikes represent lowly doped areas with an enhanced recombination.     

Chitosan particles agglomerated scaffolds for cartilage and osteochondral tissue engineering approaches with adipose tissue derived stem cells

In the XML file of the original article, H. Redl’s affiliation is incorrect. It is listed correctly in both the paper and PDF versions of the article, and can be found below: The online version of the original article can be found at     

An ultrasonic obstacle detector based on phase beamforming principles

A prototype of an ultrasonic obstacle detector developed as a part of a navigation system for blind and visually impaired people is presented. The detector, which employs a single ultrasound source and an array of microphones, determines the distance to the obstacle by measuring time between sending the pulse and receiving the reflected signal. Using the phase beamforming technique, borrowed from hydroacoustics, to process the output signals of microphones, it determines also the direction from which the reflected signal is received, thereby locating the obstacle. The obstacle detector was subjected to a series of tests in order to verify its design and to assess its ability to detect a broad range of obstacles. Presented test results show that most obstacles can be detected and recognized, and that the tested obstacle detector provides complete coverage of the safety zone in front of the user.     

An electrocoaters guide to selecting and maintaining rectifiers

Considering the critical contribution of your rectifier to the safe, effective, and reliable operation of your electrocoating process, the selection and maintenance of the optimum unit for your operation is time well spent.     

Cobol: perception and reality

The authors list the perceptions they have uncovered and counter them with the reality of Cobol. Some of the perceptions are: Cobol is a mainframe language-it has been available on PCs since their inception; Cobol stopped evolving in the 1970s, stopped growing in popularity in the 1980s, and stopped being used to develop client-server and Web-based applications in the 1990s; and Cobol is not an object-oriented language, when, in fact, it has objects galore