Part 1 of this FAQ looked at the basics of the 20-mA current loop, why it is still used extensively, and its primary attributes. In this part, we’ll look at how the analog current loop is used for digitized signals and at self-powered loops – two developments which have extended its life and viability. Q: […]
20-mA current loops, Part 1: Basic functions
You’ve been given an “easy” assignment: get the low-rate data from a temperature sensor to a control computer located 100 feet (30 m) away, in an industrial setting. After much investigation and assessment, you choose a widely used standard called the 20-mA loop, which has been in use for over 50 years, rather than Wi-Fi, […]
Electrical noise, Part 2: Additional perspectives
In Part 1, we looked at some facets of noise: sources, external versus internal (intrinsic) noise, and equations. Part 2 goes further into noise specifics. Q: What are some of the types of noise? A: It’s a long list. The same noise may have different names depending on the perspective of the person describing it, […]
Electrical noise, Part 1: Introductory concepts
Electrical noise is a consideration that engineers think, talk, worry, sometimes obsess about, and deal with nearly all the time, with few exceptions. In many applications, it is the limiting factor on ultimate achievable system performance. If it were not for the existence of noise, many design situations would be far, far easier. Noise is […]
Active noise cancellation, Part 2: Implementation
Part 1 of this FAQ looked at the basic concept of active noise cancellation, how it might be implemented in principle using analog circuitry, and the harsh reality of actually providing the ANC function. Part 2 looks at modern ANC systems and how they function, as well as their practical issues. Q: Is ANC using […]
RF/Microwave noise, Part 2: Noise temperature and applications
Part 1 of this FAQ looked at the basic specifications of noise factor and noise figure, widely used in RF/microwave system and circuit analysis to predict and assess both requirements and performance. This part looks at the additional parameter of noise temperature, as well as the impact this parameter has on system performance. It also […]
RF/microwave noise, Part 1: Noise figure basics
The lower-frequency world of electronic circuits and systems for communications links routinely uses parameters such as voltage and current, bit rates, and signal/noise ratio, to cite just a few of many, many possibilities. While these are also important in the world of RF and microwave links and system functions, engineers doing work in this arena […]
Load pull for RF devices, Part 2: How and where
Part 1 of this FAQ explained the what and why of load-pull tests of RF devices and impedance matching. Part 2 looks at various ways the test can be set up and run. Q: What’s the basic test setup for a modern load pull? A: As shown in the figure of Part 1 (and repeated […]
Load pull for RF devices, Part 1: What and why
Impedance matching between RF stages has always been a priority to ensure maximum transfer of RF power along with minimal RF-power reflections. Although most RF systems are designed for nominal 50-ohm input and output impedance (and 75-ohm for cable TV), the reality is that many components do not present that preferred 50-ohm impedance due to […]
Gyroscopes, Part 2: Optical and MEMS implementations
Part 1 of this FAQ examined the basics of IMUs based on spinning-rotor gyroscopes to establish and maintain a fixed attitude via a gimbaled platform, along with orthogonal accelerometers to sense motion along each axis. Part 2 looks at optical and MEMS-based gyros which have largely replaced the spinning-rotor core function except in the most-demanding […]
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