Professor

Biography: 

Dr. Rakesh Sinha received the B.Tech degree in electronics and communication engineering from Kalyani Government Engineering College, Kalyani, India, in 2008, and the M.Tech and the Ph.D. degree in RF and microwave engineering from the Indian Institute of Technology, Kharagpur, India, in 2011 and 2016 respectively.

From 2008 to 2009, he was with the Department of Robotics and Automation, Central Mechanical Engineering Research Institute, Durgapur, India, as a Junior Research Fellow. He was an Assistant Professor at the Department of Electronics & Communication Engineering, JIS College of Engineering, Kalyani, India, from 2016 to 2017. During 2017-2018, he was associated with the Ulsan National Institute of Science and Technology, Ulsan, South Korea, as a Postdoctoral Researcher. He was associated with Chungnam National University, Daejeon, South Korea, from 2018 to 2019. Currently, Dr. Sinha is working as an Assistant Professor at the Department of Electrical Engineering, National Institute of Technology Rourkela, India. 

 His current research interests are in the area of multiport network synthesis, impedance matching, coupling, decoupling networks, phased array, and computational electromagnetic. Dr. Sinha has proposed the concept of the phase-shifting matching network, port-decomposition technique, and Y-matrix algorithm for impedance transforming multiport. He and his students developed educational software for microwave circuit design available at IEEE Dataport and Zenodo.  Two undergraduate students, under the supervision of Prof Rakesh Sinha, received   Undergraduate Research Scholarships from  IEEE APS and MTTS, respectively.   

Fundamental Works:

• General Asymmetric Structure-Based Rat-Race and Branch-Line Coupler: Conventionally rat-race and branch-line Coupler (RRC & BLC) consist of quarter wavelength transmission lines (TL) or their equivalent symmetric two-port network (TPN). It has been shown that RRC & BLC can be designed using asymmetric-TPN blocks and the design equations have been derived for the same. The use of asymmetric structure provides more flexibility in the design of microwave components.

• Multiport Networks Synthesis using Port Decomposition Technique and its Applications: A multiport network synthesis algorithm has been proposed based on port decomposition (by short-circuiting the port) and reduce-multiport scattering parameter technique. Design equations of four couplers using asymmetric-TPN blocks have been derived using the algorithm. The port-decomposition technique provides physical insight into the working of microwave components.

• Impedance Matching Network (Interconnect) with Desired Transmission Phase: The impedance matching network (IMN) is used to connect two ports having a different (or same) impedance. Conventionally design equations of IMN were derived using reflection property, no attention has been paid to the transmission (Phase) property. It has been shown that the transmission phase is crucial in the design of IMN. A general design equation of IMN has been derived incorporating the transmission phase. The concept of transmission phase in the design of matching networks may play an important role in the future Phased Array Antenna Technology.

• Sub-network Inequality Theory: A network can be represented as interconnections of multiple sub-networks. The schematic of the interconnections of multiple sub-networks is called topology. Two networks are said to be functionally equivalent to each other if and only if their network matrices are equal, even if they are topologically different from each other. If sub-networks (with identical orientation and position) of two networks with identical topology are equivalent, then the whole networks are also equivalent to each other. However, if two networks with identical topology are equivalent to each other, then it is not necessary that the sub-networks are also equivalent to each other. In other words, if the sub-networks of two topologically identical networks are not equivalent to each other, then it does not provide a guarantee that the whole networks are also not equivalent.

• Phase Shift and Electrical Length are not the same: It is a common belief among microwave engineers that phase shift due to transmission line (TL) is equal to the electrical length of the TL. That is true only for matched TL and TL with an electrical length of multiple of 90 deg.  However, if the termination impedance or port impedance is different from the characteristic impedance of the TL, then phase shift is different from the electrical length. This difference is due to the multiple reflections of waves at terminations.  

• Theory of Coupled Characteristic Mode: The coupled characteristic modes are linear combinations of uncoupled characteristic modes. The uncoupled characteristic modes are higher dimensional projection isolated modes. Therefore coupled characteristic modes can be represented as a linear combination of higher dimensional projection of isolated modes. Such mode coupling can be approximated as "one to one" or "two to two" or "many to many" mode coupling. An analytical method has been developed to calculate the coefficients and eigenvalues of "one to one" mode coupling. The Eigen data of "two to two" and "many to many or n to n" mode coupling can be obtained by solving lower order (i.e., 4 and 2n) eigenvalue problems.

• S-matrix Synthesis with Unequal Complex Terminations using Y-matrix and Desired Phased IMN: If we consider a multiport as interconnections of multiple two-port-network (TPN) with common ground, then the topology of the multiport network can be predicted using the non-diagonal non-zero entries of Y-matrix of the network. The port impedance of a network can be controlled using external matching networks with identical phase shifts. Utilizing these concepts two algorithms have been proposed to design multiport networks with unequal complex port impedances. 

Curriculum Vitae: