The 50-ohm impedance is standard in RF design, while 75 ohms is also used, so it’s important to understand the attributes of each and not confuse them. One of the issues that beginning electronic engineers must grasp is the concept of impedance and impedance matching, especially concerning transmission lines, cables, and connectors. This FAQ will […]
Which is the real problem: overengineering or underengineering?
Today’s engineering mandates an almost-impossible balance among design imperatives. I recently received two unrelated email advisories from reputable technology companies promoting online webinars on the same topic: the cost of overengineering, also known as overdesign. One of these even had a dramatic example of a customer who needed a machine to stuff foam into a […]
FAQ on the Butler matrix for beamforming: part 2
This passive beamforming topology is not well known but is widely used – a common situation in the RF world. Part 1 was an introduction to the electronic steering of an antenna beam and the Butler matrix; this part continues the investigation. Q: The Butler passive arrangement seems simpler; why not use it in all…
FAQ on the Butler matrix for beamforming: part 1
This passive beamforming topology is not well known but is widely used — a common situation in the RF world. For many years, radar applications defined much of the world of directional antennas. These antennas were designed with a fixed directivity or rotated in a steady pattern at a known rate, as seen in Figure…
FAQ on three-phase AC power part 2: implementation
We’re familiar with single-phase AC at the outlet, but multiphase AC offers advantages and is necessary for higher-power installations. The first part of this article examined the need for three-phase AC. This part looks at the implementation. Power sourcing and wiring Q: How is the three-phase AC power generated? A: It does not use three […]
FAQ on three-phase AC power: part 1
We’re familiar with single-phase AC at the outlet, but multiphase AC offers advantages and is necessary for higher-power installations. For most engineering designs, the circuit’s DC operating power comes from one of two sources: either a battery or a basic AC line, which has been stepped down via a transformer, rectified to DC, and then […]
Barrel connectors already drive me crazy…and now even crazier
The simple and ubiquitous DC-power barrel connector brings a lot of confusion and frustration. Like most of you, I have accumulated a random collection of many ac-dc and a few ac-ac power-adapter/charger units – often referred to dismissively as “wall warts” – over the years, with a collection that resembles Figure 1. After all, what […]
FAQ on Rogowski coils for current measurement
This basic non-contact transducer is often used to measure AC currents. Accurate measurement of static and dynamic current flow in a conductor is a common requirement in many circuits and systems. Designers have several transducer options for this, including sensing the voltage across a known, in-circuit sense resistor, using a non-contact Hall-effect sensor, or employing […]
FAQ on optical proximity sensing: part 2
A light source and photosensor combine for effective, reliable, non-contact proximity detection of nearby objects. Part 1 of this article looked at the principles and three basic approaches to optical proximity sensing, also called photoelectric sensing. This part looks at physical implementations of the system, input/output specifics, and other considerations. Q: Is this a relatively […]
FAQ on optical proximity sensing: part 1
A light source and photosensor combine for effective, reliable, non-contact proximity detection of nearby objects. Non-contact proximity sensors detect the presence or absence of nearby objects (including animals and people) using basic physics phenomena such as capacitive and inductive electromagnetic fields, light, or sound. Many techniques are used for this sensing, each offering different operational […]
