A digital-to-analog converter (DAC) is more prone than an analog/digital converter to signal degradation. DACs are complex devices requiring precisely matched components. For this reason, with notable exceptions, DACs are implemented as mixed-signal ICs based on MOSFET technology. Discrete component DACs are found in radar systems and high-speed test equipment including digital sampling oscilloscopes. Digital […]
FAQ
The up side of under sampling
A digital signal can be derived from the original time-varying, continuous analog signal by creating a sampled sequence of quantized values. It is intuitively evident that the fidelity and resolution of this quantized signal is based upon the number of samples taken per unit of time. Harry Nyquist published an early version, later further formalized […]
Measuring and using static electricity
Many moons ago, a future member of our editorial staff was playing with his very first multimeter. He was a farm kid. One of his first experiments was to put the negative lead of the meter on a ground rod and the positive lead on one of the metal bands used to reinforce the interlocking […]
What is “orthogonal”? (Part 4): eye diagrams
The phrase and concept “orthogonal” is widely used in engineering, but it is also often misunderstood. Just as both the time domain and frequency domain are two legitimate ways of looking at a signal from different perspectives linked by the Fourier transform, the constellation diagram has a time-domain complement called the eye diagram or eye […]
What is “orthogonal”? (Part 3): signal constellations
The phrase and concept “orthogonal” is widely used in engineering, but it is also often misunderstood. We can look at orthogonal signals in multiple ways: in the time domain, the frequency domain, as a constellation – a presentation which is widely used in the broad discipline referred to as signal processing, and as an eye […]
What is “orthogonal”? (Part 2): signal space
The phrase and concept “orthogonal” is widely used in engineering, but it is also often misunderstood. The formal definition of orthogonal signals does not necessarily mean that they are unrelated or uncorrelated, although that is how the term is often used in casual “engineering speak.” Formally, two vectors are orthogonal if their dot product is […]
Coaxial cable myths and misunderstandings
In this age of misinformation, you can add coaxial cable to the list of items for which it is easy to get steered wrong based on internet searches. Much of the bogus online commentary about coax relates to cable loss, cable impedance, and standing waves. Here are a few basics that may help sort the […]
What is “orthogonal”? (Part 1): mechanical design
The phrase and concept “orthogonal” is widely used in engineering, but it is also often misunderstood. I was chatting the other day with a non-technical friend and said something like, “Oh, that won’t happen. Those two things are orthogonal.” My friend looked at me and replied with a “huh?” and he was right to do […]
Can something consume energy without emitting a field?
The editorial offices of Testandmeasurementtips.com recently received a letter from an individual who headed up a group of investigators of paranormal phenomenon. It was a serious letter. To summarize, the group had concluded there was no legitimate method to record the activity of an alleged haunting. But the writer did have a question for us, […]
How big is the band gap? A heated discussion
There’s a trick with a soldering iron that can be used to determine whether an unidentified semiconductor is n-type or p-type. In essence, it determines whether the majority carriers are holes (p-type) or electrons (n-type). Just as heat makes a gas expand (PV=nRT), the hot tip of a soldering iron makes carriers expand away from […]