The vacuum-tube cavity magnetron is nearly obsolete (except for the millions in consumer microwave ovens). Its development was key to highly effective WWII radar, and it also led to other RF/microwave vacuum-tube devices. Vacuum tubes are so “yesterday,” aren’t they? They have been rendered obsolete and supplanted by solid-state devices for many reasons, except in […]
FAQ
Passive microwave components, Part 2: couplers and splitters
Part 1 looked at isolators and circulators, basic RF/microwave passive devices. This part looks at couplers and splitters, two other basic passive devices. (Attenuators are another important class of passive RF/microwave devices. They are not covered here.) A: How are coupling and splitting done in the non-RF/microwave world? A: In the non-RF world, it is […]
Passive microwave components, Part 1: isolators and circulators
Basic passive microwave components have a vital role in RF/microwave system design. Despite the apparent simplicity of their functions, their performance is based on electromagnetic theory and Maxwell’s equations for insight into their operating principles and performance. Design for the demands of microwave signals is a very different situation than working at lower frequencies. Although […]
RF switches, Part 2: Analog and MEMS switches
Part 1 of this FAQ looked at the venerable electromechanical RF switch – still widely used in some applications, where it is the only viable option—and the use of PIN diodes as RF switches. This part looks at analog and MEMS-based switches. Q: What is an analog switch? A: It’s conceptually straightforward: in basic form, […]
Filters, Part 2: SAW and BAW devices for RF
Part 1 of this FAQ looked at the basic available electronic filters – analog, switched capacitor, and digital – and briefly reviewed the attributes of each. As the frequencies to be filtered reach to 1 GHz and well beyond, while the selectively needed also became narrower, these filter approaches can no longer support many of […]
MRI, Part 2: historical development (and lawsuits)
The modern MRI system is an amazing blend of diverse technologies, based on the realization that a small but critical aspect of the spin of hydrogen nuclei could be leveraged to provide a safe, non-invasive way to see inside a human body. Part 2 of this FAQ looks at the physics and other advances that […]
Optical amplifiers, Part 2: Basic implementations
Part 1 of this FAQ began an overview into the arcane world of all-optical amplifiers including where and why they are needed. Part 2 will briefly describe the four types and identify the two most commonly used for optical-fiber link signal boosting. Q: How “accurate” will this presentation be? A: Frankly, it will have large-scale […]
Optical amplifiers, Part 1: Applications and considerations
We can now amplify electronic signals from low frequencies to the multi-GHz range without too much difficulty, but amplifying a stream of photons such as in an optical fiber has a very different meaning and is a challenge with no single or easy solution – but it is being done. Electronic and optics technologies are […]
A comparison of MEMS and electret condenser microphones
By Bruce Rose, Principal Applications Engineer, CUI Inc Many of today’s smart devices such as home digital assistants and IoT sensors are required to “hear” their environment. There is a growing demand for microphones that are not only highly miniaturized, but also robust, easy to design-in, and resistant to nearby acoustic or electrical noise. Fortunately, […]
Analog computation, Part 2: When and how
Analog circuits based on op amps can be used to implement mathematical functions and are still useful in many applications due to their unique attributes. Part 1 of this FAQ looked at the basic need for and virtues of analog-based computational circuits. Part 2 looks at some implementation specifics and considerations. Q: What are the […]