Eric L. Holzman holds a Ph.D. in Electrical Engineering from the University of California at Los Angeles.
His current work at Northrop Grumman involves the design and analysis of active arrays and other antennas operating from UHF to millimeter-wave frequencies. Previously, he was employed at Millitech designing antennas and transceiver circuits for fixed wireless applications, at Lockheed Martin where he was involved in the design of phased array radar systems, and at Hughes Missile Systems Company.
Dr. Holzman is a Senior Member of the IEEE, reviewer for the Transactions on Microwave Theory and Techniques and Antennas and Propagation, and past Chairman of the Philadelphia Chapter of the IEEE Antennas/Microwave societies. He is author of Essentials of RF and Microwave Grounding (Artech House, 2006), lead author of the text Solid-State Microwave Power Oscillator Design (Artech House, 1992), and author of over 45 publications and holder of eight patents in the microwave field.
Grounding is a fundamental aspect of much of practical electrical engineering. In particular, for practicing microwave engineers, improperly designed high frequency grounding of RF and microwave passive and active devices, subsystems and systems can cause those components to malfunction, fail or interfere with each other in unexpected and undesirable ways. In this tutorial lecture, I will describe practical techniques for RF grounding that can be used by the designers of microwave circuits, components and antennas. I highlight concepts with simple derivations and results from numerical electromagnetic simulations of real microwave components, illuminating performance problems that can occur when grounding design is inadequate.
I begin by reviewing relevant background material, including low frequency grounding with a simple lumped circuit examples, defining grounding for distributed circuits and antennas and introduce the problem of poorly designed grounding paths for microwave circuits.
The heart of my lecture focuses on RF grounding for passive circuits, first as it applies to guided waves on coax, microstrip and waveguide. We examine the flow of currents, including how their interruption can cause excessive loss and unexpected radiation. Given the proliferation of multilayer, printed circuit technology in our field, we turn next to RF grounding for multi-layer, mixed signal printed circuit boards and surface mounted microwave components. Grounding can be particularly troublesome if ignored in the design of transitions between different types of transmission lines. I use results from numerical electromagnetic simulations of transitions between microstrip, coax and waveguide to illustrate show how care in the design of the ground path is essential for optimum performance.
Next, I take a look at grounding in active microwave circuit design, including amplifiers, switches and mixers. Since the microwave field-effect transistor is a building block of many active circuits, I spend time using simple derivations and results from a microwave circuit simulator to illustrate the consequences of poor source grounding. I explain why the design of multi-stage amplifier chains having a lot of gain usually requires well-grounded shields for the suppression of feedback oscillations. I finish active circuit grounding by looking at high active devices are mounted on printed circuit boards.
Grounding and radiation are related, so I end my lecture with a look at antennas and ground planes. In one sense, an antenna is a load through which currents flow from source to ground. The antenna is designed so those currents radiate. Antennas are often designed on a computer to operate in a free space. When such antennas are installed near a ground plane that was not part of the original model, the ground plane can radiate and cause the radiation pattern and impedance match to change. I describe a number of methods for controlling this interaction.