Ajay K. Poddar received his Graduation (B. Tech-1990) from NITC India, Fellowship (EFC-1991) from IAT India , Master (M. Tech-1996) from IIT-D India, Diploma (FUCHS-1997) from Johannesburg RSA, Doctorate (Dr.-Ing. -2004) degree from TUB Germany. From 1990-2001, he worked as a Senior Scientist in DRDO (Defense Research and Development Organization) India, associated with the development of Proximity RF & MW sensors and RADAR for various applications. He was Visiting Professor (1999-2004) for post graduate students in University of Pune, India, appointed as a Guest Lecturer (2009-to date) in Technical University Munich, Germany. Dr. Poddar is currently working as a Chief Scientist at Synergy Microwave Corp., NJ, USA, responsible for design and development of state-of-the-art RF modules such as oscillator, synthesizers, antenna, mixer, amplifier, filters, and MEMS based RF components. He holds several dozen of patents and has published more than 170 technical papers in international conferences and professional journals, contributed as a coauthor of 5 technical books, reviewer of several journals, including the IEEE T-MTT, IEE TCAS, IEEE, IEEE UFFC, IET, and Electronics Letters. Dr. Poddar is a senior member of professional societies IEEE (USA), AMIE (India), and IE (India), advisory board member (Don Bosco Institute of Tech, Mumbai, India) and active member of various societies that are linked with scientific contributions for good cause and broader perspective of the humanity. Dr. Poddar has received several awards (Young scientist awards for the year 1999 and 2000, MW & RF Products awards for the year 2004, 2006, 2008 and 2010) for his contribution in the field of microwave signal sources for current and later generation communication systems.
Abstract: The oscillator circuit is, an important and critical module for modern communication system, being traded simultaneously by increase in the operational frequency, improved phase noise performance, wider bandwidth, and decrease in physical dimensions. The resulting physical design layout challenges faced by circuit designers are rapidly increasing in both discrete and MMIC versions of VCOs (voltage controlled oscillators), while the choices for solutions on how these challenges, especially low cost ultra low phase noise solution be best-addressed are kept aside. The phase noise of oscillator circuit used for timing devices is a critical figure-of-merit as it affects dynamic range, selectivity, and sensitivity of a receiver. The ability to achieve optimum phase-noise performance is paramount in most RF design and synthesizers. The continued minimization of phase noise is required for the efficient use of frequency spectrum. The phenomenon of phase noise generation in oscillator circuits has been the main focus of important research efforts, and it is still an open issue despite significant gains in practical experience and modern CAD tools for design. In frequency generating circuits, noise dynamics places stringent condition on the frequency sources owing to inherent high noise-figure and low dynamic-range caused by the uncontrolled nonlinearity at large-signal drive-level conditions. In addition, these problems become critical at high frequency when active devices (Bipolars/FETs) are technologically scaled to obtain higher cut-off frequency.
Unlike other microwave circuits, oscillators do not behave in totally predictable way. Hence “tweaking” has been an accepted mainstay of the signal-source design flow. Fortunately, high-frequency commercial design tools (like Agilent ADS, Ansys, AWR Microwave Office, Cadence Design Systems SpectreRF, Avista Design Systems SP/XL-RF, etc.) have dramatically improved the convergence problem of a nonlinear active circuit (oscillator) under large signal drive conditions. Therefore, tweaking of prototype circuit is far reduced, and designers today can make meaningful sense of the autonomous circuit using powerful CAD tools.
This talk addresses above issues and reports the latest technology and technological challenges in oscillator design for the frequency controlled circuits and timing devices. It also gives the transition from high quality factor expensive discrete resonator (like Crystal, SAW, BAW, MEMS, DR, YIG, Opto-Electronic) based tunable oscillators to low cost monolithic integrated circuit (MMIC) solutions. The solutions that are gaining more popularity such as RF MEMS and Tunable active inductor oscillator (TAIO) are described for completeness, including their CAD simulation and state-of-the-art practical examples in the field of modern electronic and communication systems.