June 15, 2019
June 15, 2019
October 19, 2019
Engineering Physics and Physics
Integration of Physics Fundamentals to prepare students for the Hi-Tech World through Design of filters deployable in Mobile Communication
Frequency selection devices such as filters can be used to manipulate different RF bands at widely varying frequencies in all mobile communication systems. Thin film Piezo-electric materials offer great opportunities that can be engineered with other materials to achieve RF Filtering. The foundation of developing experimental filters lies at acquiring a couple of stacked crystal filters (SCFs) and placing them vertically over each other separated by a thin film electrode. The SCF works on the principle of generating and transferring acoustic energy from one Piezo-electric film to another at a particular range of frequencies wherein the structure is resonant. In other words, electrical energy is converted into mechanical energy by the input Piezo-electric film and it is transferred to the output Piezo-film which converts mechanical energy back to electrical energy.
The electromechanical coupling determines the amount of energy that can be converted between electromagnetic and mechanical energies within a single Piezo-electric film. In addition the amount of coupling between the two Piezo-electric films determines the mechanical energy that can be transferred between them. Generally, all aspects of the electromagnetic coupling in the device play important roles in determining the filter’s resonant frequency, insertion loss and bandwidth characteristics. The approaches to improve electromechanical coupling by proper choice of electrode materials, device impedance matching and beneficial use of external components like inductors are of paramount importance. The Piezo-electric films are mounted on an acoustic mirror to prevent loss of acoustic energy into the substrate. The acoustic mirror also serves in suppressing unwanted (spurious) modes of vibration.
Innovative mobile applications demand newer techniques, novel processes and, at the same time, should be integratable with standard CMOS Technology. Bulk Acoustic Wave (BAW) filters form core elements for highly advanced RF frontend modules.
BAW filters are extremely important due to their size, low insertion loss and their integratibility with newer technologies in RF Domain. Accurate modeling of electrical performance of the RF filters depends on how precisely the values of physical parameters of materials used in their design are known and whether all of its specifications have been met. Sophisticated modeling techniques incorporating material parameters pertaining to their design, simulation and verification need to be explored to their fullest extent before fabrication of such devices.
Generally, filter parameters vary from one material manufacturer to another and the processing methods used during fabrication. Therefore a methodology is needed to determine these values based on the filters electrical characteristics. In essence, a simple, expedient and inexpensive method is needed to determine effective parameters such as acoustic velocity and density values of the materials used in the filter. The innovative design of experiments (DOE) is required comprised of generating various electrical impedance peaks in the wideband spectrum of the filter that is material sensitive and correlates to the acoustic properties of the systems.
In addition, the filters must be resistant to temperature variations to generate information for the extraction of their temperature coefficients of frequency as well. A new approach to compare the temperature increase analytically and experimentally is needed along with correlating temperature distribution and thermal value, in accordance with their transfer characteristics. The accurate scaling values for each parameter also need to be established. The optimization on such devices that yield accurate scaling rules for each parameter must be in compliance with the scattering (s) parameters.
The author feels a compelling need for integration of Physics fundamentals in all Hi-Tech courses. Such a methodology adequately prepares students for a demanding industrial world wherein technology is evolving all the time but basic fundamentals hardly change. Those who are successful in integrating these fundamentals with Hi-Tech courses never face obsolescence. The author has been involved in this art of integration for the last three decades and has witnessed several hundreds of his students achieved high success in their careers. The mantra in the classroom has been only those students who successfully integrate fundamentals in high-courses became wise, else they remain otherwise. My earnest attempt has been to integrate all of my students into the category of ‘wise’.
Prasad, K. (2019, June), Integration of Physics Fundamentals to Prepare Students for the Hi-Tech World through Design of Filters Deployable in Mobile Communication Paper presented at 2019 ASEE Annual Conference & Exposition , Tampa, Florida. 10.18260/1-2--32997
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