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A multilayer gap-coupled dual band hexagonal microstrip patch antenna is presented for GPS Aided GEO Augmented Navigation (GAGAN) receivers. GAGAN is developed by AAI (Airport Authority of India) and ISRO (Indian Space Research Organization) exclusively for aviation purposes with the GPS frequencies L5 (1176.45 MHz) and L1 (1575.42 MHz). The proposed GAGAN antenna has three trapezoidal and four equilateral triangular patch resonators configured to form a gap-coupled hexagonal patch on the top layer and seven equilateral triangular patches with slots in between to form the middle layer. Both the layers are fed by a single coax feed to achieve a dual band compact microstrip antenna of size 55 mm x 55 mm x 3.2 mm. Instead of designing the hexagonal antenna conventionally from a circular patch antenna, the sides of the equilateral triangular patch are truncated to obtain the proposed compact hexagonal antenna as the triangular antenna occupies less area when compared to circular or square patches for a fixed frequency. To bring in novelty with improved performance, the combinatorial structured configuration has been explored through step-by-step optimization. The aspects of GAGAN requirements like circular polarization with a single input, dual band operation and high gain with gain flatness are achieved with this compact structured antenna when compared to square and circular patch antennas. The combinatorial structures such as perturbation and truncation introduced in the patches are responsible for exciting two near-degenerate orthogonal modes producing circular polarization (CP). A cross slot etched in the center patch results in gain enhancement with a gain above 3.2 dBi over a bandwidth of 20 MHz in both the bands. Five shorting pins are added to achieve high impedance matching and good CP with an axial ratio (AR) below 2 dB. The simulated and measured results are found to be in good agreement with greater than 20 MHz operational bandwidth exhibiting CP with an omni-directional radiation pattern having high cross polar levels of -22 dB. The size reduction achieved in the proposed design is 56.79% when compared to the conventional hexagonal patch antenna. The measured 10 dB impedance bandwidth is 2.7% and 2.1% for L5 and L1 bands respectively with a 3 dB AR bandwidth of 2.3% for L5 and 2.0% for L1, satisfying GAGAN requirements.INDEX TERMS Circular polarization, dual band, global positioning system (GPS), GPS aided GEO augmented navigation receivers (GAGAN), hexagonal antenna, multilayer, triangular antenna.

Today's electronic systems, with ever-growing demand for mobile computing devices, are more complex, fast and energy efficient. Cost and quality are the major issues in testing these circuits. The test data storage requirements, along with the operating frequency and channel capacity, have a significant impact on the test cost. This paper presents a new compression scheme based on Alternating Variable Run-length (AVR) codes for reducing the test data. Weighted transition based reordering scheme is adopted prior to the compression scheme to improve the compression ratio (CR). By applying an appropriate mapping scheme, sufficient reduction in power has been achieved. The scheme is also found to have a maximum of 10% increase in compression ratio when compared to the conventional frequency directed run-length codes (FDR) codes and extended FDR (EFDR) codes without any significant on-chip area overhead. The experiments are performed on ISCAS'89 benchmark circuits.

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Particle Swarm Optimization (PSO) algorithm has been applied in electromagnetics to design microwave absorbers. Generally, microwave absorbers are used for absorbing the electromagnetic radiation caused due to numerous electronic equipments and is being extensively used in stealth technology. The main aim of this paper is to find and analyze the minimized maximum reflection coefficient over a range of frequency and angle of incidence for a fixed number of layers and polarization. An improvised PSO algorithm has been suggested by utilizing a velocity restriction factor that intelligently searches for the optimum solution. The pareto principle with an improvisation in social and cognitive parameters has also been applied. The algorithm succeeded in finding better values of reflection coefficient for the microwave absorber structures comparatively. Based on the pareto principle a form of mutation technique is also used for better convergence. The results have been compared and tabulated for various combinations of the microwave absorber structure and the thickness of each layer is also optimized for a predefined database.

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