Any unwanted signal that’s combined with the desired signal is called noise. In any circuit, noise can come from anywhere; from external systems as well as from within a circuit itself. External sources include a number of sources such as power lines, RF transmitters, nearby conductors, ignition systems, or motors that turn on and off […]
basics
Step-by-Step PCB Soldering tips for newbies
The traditional, older type of solder is a mixture of lead (Pb) and tin (Sn). This type of (60/40 – Pb/Sn) solder melts at 200°C and is typically made up of 60 percent tin and 40 percent lead. However, lead-free solder is desirable today, in terms of avoiding a toxic environment. Lead-free solder is a […]
Magnetic resonance imaging (MRI), Part 1: How it works
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. Magnetic resonance imaging (MRI) is an extraordinarily valuable and vital tool for non-invasive […]
Filters, Part 1: Analog, switched, and digital filters
Filters are essential functions in most circuits and systems; as frequencies extend into the multi-GHz range, surface acoustic wave (SAW) and bulk acoustic wave (BAW) filters are needed to meet the design objectives. An engineer I worked with (and whose name I have forgotten) once remarked to about electronic filters (and he was serious): “like […]
Signal-channel diversity and fading, Part 1: Space diversity
In the engineering context, the phrase “channel diversity” refers to various techniques for getting a signal from point A to point B. The different approaches to diversity can be used individually or in combination. Q: What are the primary types of channel diversity in use? A: There are two primary types: space (spatial), and frequency. […]
The RF power amplifier, Part 1: Functions
In the RF signal chain, the power amplifier (PA) is the active element located between the transmitter signal chain circuitry and the antenna, Figure 1. It is often a single discrete component, one with requirements and parameters which differ from those of much of the transmit chain as well as the receiver circuitry. This FAQ […]
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 […]
