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The integration of compact printed multielement antenna (MEA) systems on small diversity and multiple input multiple output (MIMO) terminal devices operating in the 5.2 GHz Industrial, Scientific and Medical (ISM) band is presented. The investigated MEA systems comprise up to six printed elements (inverted F and Minkowski monopole antennas) and their performance is evaluated by means of the effective diversity gain (EDG) and the 1% outage MIMO capacity. The role of the propagation environment (both outdoor and indoor) on EDG is examined, proving that the uniform scenario is a good approximation to many real environments. The tradeoff study between system's performance and number of integrated antenna elements indicates that both diversity and MIMO performance saturate when placing more than five closely spaced elements. Even the least efficient 6-element system however, can be advantageously used as a reconfigurable 2-element array under the concept of receive antenna selection, since it provides significantly improved MIMO performance over a conventional 2-element fixed one. The paper concludes with a summary of useful guidelines for the MEA design optimization procedure that emanated from this study. Index Terms--Antenna diversity, antenna selection, diversity gain, multiple input multiple output (MIMO) capacity, monopole antennas, printed circuit antennas.

Digital (i.e., droplet-based) microfluidics, by the electrowetting-on-dielectric (EWOD) mechanism, has shown great potential for a wide range of applications, such as lab-on-a-chip. While most reported EWOD chips use a series of electrode pads essentially in 1-D line pattern designed for specific tasks, the desired universal chips allowing user-reconfigurable paths would require the electrode pads in 2-D pattern. However, to electrically access the electrode pads independently, conductive lines need to be fabricated underneath the pads in multiple layers, raising a cost issue particularly for disposable chip applications. In this paper, we report the building of digital microfluidic plates based on a printed circuit board (PCB), in which multilayer electrical access lines were created inexpensively using the mature PCB technology. However, due to its surface topography and roughness and resulting high resistance against droplet movement, the as-fabricated PCB surfaces require high (~500 V) voltages unless coated with or immersed in oil. Our goal is the EWOD operations of droplets not only on oil-covered surfaces but also on dry ones. To meet the varying levels of performances, three types of gradually complex post-PCB microfabrication process are developed and evaluated. By introducing land-grid-array sockets in the packaging, a scalable digital microfluidic system with a reconfigurable and low-cost chip is also demonstrated. [2007-0049] Index Terms--Electrowetting, electrowetting on dielectric (EWOD), lab-on-a-chip, microfluidics, micro total analysis system, printed circuit board (PCB).

A study is described of a modified planar inverted-F antenna (PIFA) operating in 2.5 GHz band on a printed circuit board (PCB) of a mobile phone handset. The antenna dimension is reduced substantially with a miniature ground plane and capacitive loading. While inheriting the attractive features of PIFAs, such as low profile, easy fabrication and low cost, the proposed antenna exhibits low coupling to the PCB. A dual-element PIFA array is implemented on a mobile handset PCB and the diversity performance of the dual-element PIFA array is evaluated in both simulation and measurement. Index Terms--Diversity gain, multiple input multiple output (MIMO), mutual coupling, planar inverted-F antenna (PIFA).

A fabrication process for vertical thermopiles embedded in a 75-[micro]m-thick polyimide foil has been developed for flexible printed circuit boards (flex PCBs). The vertical connections consist of electrodeposited antimony- and nickel-plated through-hole vias. The plated through-hole vias consist of multiple wires, with a total metal content that is 1% of the total via volume. The via fabrication technique is similar to standard flex PCB wet etch and metallization processes. The main difference is that the foils are pretreated with ion irradiation to induce highly selective vertical etch rates. The thermopiles were characterized by measuring their voltage response to an applied temperature difference across the foil thickness. [2007-0133] Index Terms--Flexible printed circuit boards (flex PCBs), plated through-hole vias, polyimide foils, thermoelectricity.

In this paper, the authors present a system to inspect metal stencil that is used to print solder paste on pads of surface-mounted device on printed circuit board. The developed inspection system is composed of a moderately precise X--Y robot and a vision system. To correct a position error caused by the X--Y robot, the authors define position error vector and apply modified Hough transform to determine the dominant position error vector. Using this extracted dominant position error vector, the reference image is modified. This transformed reference image is compared with the camera image. Fuzzy logic is utilized to judge the correctness of the holes on the stencil. The input variables are the ratio of the overlapped area of two holes and the distance between the centroid of them. The output variable is the grade of the identity of the hole. These methods are verified by a simulation and applied to the inspection system. Index Terms--Automatic inspection system, fuzzy logic, modified Hough transformation (MHT), stencil (metal mask).