Part 1 of this FAQ provided context and background on the PC board, and discussed its first widespread appearance as a phenolic-based board. Part 2 looks at some board issues and the widely used FR-4 PC board substrate. Q: I see the term “solder mask” — what is that? A: Solder mask (also called 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 […]
The microstrip antenna, Part 1: Basics
The microstrip antenna is a convenient, planar, easy-to-fabricate antenna with some attractive attributes and features, as well as some distinct limitations. The passive antenna is a critical part of any wireless communications link, for both transmit and receive sides. Depending on the application, the same antenna may be used for both roles, or radically different […]
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. […]
Optical tweezers move nano-objects, Part 3: The system
Part 2 of this article continued the exploration of the basic optical tweezer. This part builds up to a complete system, DIY optical tweezer systems, and extensions to the basic optical-tweezer arrangement. The optical tweezer is obviously not a simple system, and a complete system requires lenses, dichroic mirrors, a laser, video camera, isolation against […]
Optical tweezers move nano-objects, Part 2: The optical path
A combination of optics, lasers, electronics, and combined with advanced physics principles, allows “touch-free” physical manipulation of molecules, viruses, and other nano-sized objects. Part 1 of this article presented the goals of the optical-tweezer design and some of the reasoning which leads to it. This part continues to build up to a larger, complete system. […]
Optical tweezers move nano-objects, Part 1: The Principles
A combination of optics, lasers, electronics, and combined with advanced physics principles, allows “touch-free” physical manipulation of molecules, viruses, and other nano-sized objects. How do you manipulate and move tiny objects such as pieces of DNA or living cells? Conventional mechanical or vacuum tweezers, no matter how small, couldn’t grab them and would cause damage […]
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 […]
RF/Microwave bandpass filter implementations, Part 3: Microstrip, coaxial, and helical filters
Part 2 looked at two types of RF/microwave filters, but there are many more, including ceramic coaxial filters and helical filters. They are discussed in this part. Microstrip filters Microstrip filters are built as a carefully defined pattern on a PC board. There is almost no limit to the filter designs which can be built […]
