Tapan K. Sarkar

A novel hybrid FEM high-frequency technique for the analysis of scattering and radiation problems

A novel hybrid Finite Element Method and High Frequency Technique for the efficient analysis of scattering and radiation problems is presented. Results of the analysis of two-dimensional scattering and radiation problems using Physical Optics as the high frequency technique are given showing some of the features of the method.

An adaptive echo canceller utilizing the conjugate gradient method in a time-variant telecommunication channel

An efficient procedure using the conjugate gradient method (CGM) is presented for adaptively computing the optimal set of coefficients for an echo canceler such that the solution can be obtained in a time-variant environment as well as in an ordinary time-invariant situation. By setting a functional which monotonically decreases at each iteration, the convergence is guaranteed for any signal matrix. The fast convergence of the CGM enables the proposed method to be applied in a nonstationary signal environment in which the optimal solution must be computed independently at each sampling period. Computer simulations indicate that the technique can be used for canceling echo signals much more efficiently than conventional methods in terms of the convergence speed and conformation of the convergence itself. >

The Antenna Development in Japan: Past and Present

This chapter contains sections titled: Introduction Maxwell, Hertz, and Their Followers in Japan Marconi and the First Japanese Wireless Communication Sea Battle of the Tsushima Straits and the Japanese Radiotelegraph Yagi-Uda Antenna Kinjiro Okabe and his Split-Anode Magnetron Radar in World War II Electrical Engineering Milestones in Japan Conclusion References

Direct Data Domain Least Squares SpaceTime Adaptive Processing

This chapter includes the following topics: Introduction Airborne Radar Signals and Information Processing Methods Direct Data Domain Space-Time Approach Description of the Data Collection System Numerical Example Space-Time Adaptive Processing Using Circular Arrays Direct Data Domain Least Squares STAP for Circular Arrays Numerical Example Using a Circular Array Hybrid STAP Methodology Knowledge-Based STAP Processing Conclusion

On the direction-of-arrival (DOA) estimation for the widely dispersed incident angles in a multipath telecommunication

The authors present an analysis of the DOA estimation problem in a practical situation of multipath communication where a number of signal components are involved at each input cluster. Secondary, a novel technique is provided for an accurate estimation of the DOA of each cluster. The new method utilizes the conjugate gradient method for iteratively finding the values for the antenna weights, which produces a set of sharp peaks in the spatial spectrum along the direction of each input cluster.<<ETX>>

An efficient adaptive algorithm for the direction-of-arrival (DOA) estimation utilizing the solution of extreme eigenvalue problem

The authors introduce an alternative method for solving the extreme eigenvalue problem for DOA estimation. The proposed technique utilizes the conjugate gradient method (CGM) for iteratively and efficiently finding one of the noise eigenvectors which corresponds to the smallest eigenvalue of the autocovariance matrix which is full complex-valued semidefinite Hermitian. When the proposed minimum eigenvalue searching (MES) method is utilized, only one noise eigenvector which corresponds to the smallest eigenvalue is computed. In addition to circumventing the need for a separate routine, the MES method can estimate the DOA of fully coherent signals without including the detection procedure under the assumption that the number of unknowns involved in the procedure is larger than the actual number of signals. The authors also provide a suggestion for removing the pseudopeaks appearing in the spatial spectrum due to the large number of antenna elements.<<ETX>>