Next Meeting: January 19, 2021 6:30 pm, Pacific Time.
Webinar: “Universal Equivalent Circuits for All Antennas”
Abstract: Series and parallel RLC resonant circuits have long been the staple equivalent circuits for dipole and loop antennas despite being narrowband approximations. This paper shows how to make universal equivalent circuits for any antenna over any bandwidth. Part 1 introduces the history of classical electric network synthesis and Smith charts and reviews antenna impedance and admittance properties. Part 2 explains the modes of vibration of continuous structures, natural frequencies, feedpoint current, and impedance resonances. The impedance function of any antenna can be accurately modeled by two of four universal equivalent circuits given computed or measured impedance data and a circuit optimizer. Examples of broadband universal equivalent circuits are shown for dipole, circular loop, and discone antennas over multi-octave and decade bandwidths. Broadband equivalent circuits are useful for interpolating between data points and performing lab tests without radiating. 1-port equivalent circuits are useful for making dummy loads for reflection experiments or match network testing. 2-port equivalent circuits are useful for transmission measurements.
Speaker: Stephen D. Stearns
Stephen D. Stearns is a consulting engineer and was a Technical Fellow of Northrop Grumman Corporation. He worked at Northrop Grumman’s Electromagnetic Systems Laboratory in San Jose, California, where he led the development of advanced communication signal processing systems, circuits, antennas, and electromagnetic devices. He is currently working on revisions to the ARRL Antenna Book for the 25th edition to be published in late 2022. Dr. Stearns is a widely respected expert on emitter location signal processing algorithms for reconnaissance systems, classical electric network synthesis and realizability, circuit topologies, non-Foster circuits and bidirectional reflectionless filters with application to impedance matching and dispersion correction. He has done fundamental research on localized waves, particularly electromagnetic vortex waves that carry orbital angular momentum (OAM). He developed a bipolarized phased array for radiating vortex waves which exhibits minimal dispersion and beam spreading. He lectures on CEM software for the analysis of antennas and radiating systems, including near field calculations for assessing fields in tissues and media of arbitrary shapes. Dr. Stearns attended California State University Fullerton, the University of Southern California, and Stanford, specializing in electromagnetics, communication engineering and signal processing. He has over 100 professional publications, presentations, and ten patents. He holds FCC Amateur Extra and commercial General Radio Operator licenses with Radar endorsement and previously held 1st Class Radiotelephone license. He has received numerous awards for professional and community volunteer activities.
Attendance is FREE. Please register using the following link to receive webinar details, via email, a few hours before the event.
