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General Properties For Determining Power Loss And Efficiency Of Passive Multi-Port Microwave Networks, Ramakrishna Janaswamy Jan 2015

General Properties For Determining Power Loss And Efficiency Of Passive Multi-Port Microwave Networks, Ramakrishna Janaswamy

Ramakrishna Janaswamy

Starting from the scattering matrix formulation, three useful properties are derived that characterize the dissipative loss and the corresponding efficiency of a multiport, passive microwave network. Elementary examples are considered that involve both reciprocal and non-reciprocal networks to demonstrate the utility of the expressions provided. When applied to the equal-split, matched, 3-port resistive divider, they recover the known fact that the device is 50% efficient. The relations yield the new result that the efficiency of a 3-port Wilkinson power divider is 2/3 on the average. Using the results presented it is further shown that the Wilkinson power divider belongs to …


On Random Time And On The Relation Between Wave And Telegraph Equations, Ramakrishna Janaswamy May 2013

On Random Time And On The Relation Between Wave And Telegraph Equations, Ramakrishna Janaswamy

Ramakrishna Janaswamy

Kac’s conjecture relating the solution of wave and telegraph equations in higher dimensions through a Poisson process-driven random time is established through the concepts of stochastic calculus. New expression is derived for the probability density function of the random time. We demonstrate how the relationship between the solution of a lossy wave- and that of a lossless wave equation can be exploited to derive some statistical identities. Relevance of the results presented to the study of pulse propagation in a dispersive medium characterized by a Lorentz or Drude model is discussed and new evolution equations for 2D Maxwell’s equations are …


Direct Solution Of Current Density Induced On A Rough Surface By Forward Propagating Waves, Ramakrishna Janaswamy Jan 2013

Direct Solution Of Current Density Induced On A Rough Surface By Forward Propagating Waves, Ramakrishna Janaswamy

Ramakrishna Janaswamy

A new Volterra integral equation of the second kind with square integrable kernel is derived for paraxial propagation of radiowaves over a gently varying, perfectly conducting rough surface. The integral equation is solved exactly in terms of a infinite series and the necessary and sufficient conditions for the solution to exist and converge are established. Super exponential convergence of the Neumann series for arbitrary surface slope is established through asymptotic analysis. Expressions are derived for the determination of the number of terms needed to achieve a given accuracy, the latter depending on the parameters of the rough surface, the frequency …


Transitional Probabilities For The Four-State Random Walk On A Lattice In The Presence Of Partially Reflecting Boundaries, Ramakrishna Janaswamy Mar 2009

Transitional Probabilities For The Four-State Random Walk On A Lattice In The Presence Of Partially Reflecting Boundaries, Ramakrishna Janaswamy

Ramakrishna Janaswamy

The four-state random walk (4RW) model, wherein the particle is endowed with two states of spin and two states of directional motion in each space coordinate, permits a stochastic solution of the Schrödinger equation (or the equivalent parabolic equation) without resorting to the usual analytical continuation in complex space of the particle trajectories. Analytical expressions are derived here for the various transitional probabilities in a 4RW by employing generating functions and eigenfunction expansions when the particle moves on a 1+1 space-time lattice with two-point boundary conditions. The most general case of dissimilar boundaries with partially reflecting boundary conditions is treated …