In part 1 of this series, we looked at the formula for the inverse discrete Fourier transform and manually calculated the inverse transform for a four-point dataset. Then, we used Excel’s implementation of the inverse fast Fourier transform (IFFT) to verify our work. Could we try something more realistic? Sure. We can take a signal […]
FAQ
How to calculate and apply an inverse FFT: part 1
The inverse Fourier transform (inverse FFT or iFFT) reverses the operation of the Fourier transform and derives a time-domain representation from a frequency-domain dataset. In early 2024, EE World published a series on the Fourier transform, which can convert a time-domain signal to the frequency domain (Figure 1, red arrow). The process is reversible (Figure […]
How can EMI be weaponized?
Electromagnetic interference (EMI) can be an unwanted and disruptive aspect of electronic system designs. It can also be amplified and weaponized. EMI is being weaponized in purpose-built high-power microwave (HPM) tactical systems that devastate electronics without the side effects of physical destruction. The initial weapons have been deployed, and a roadmap has been outlined for […]
Controlling EMI and improving sustainability
Optimized designs require less electromagnetic interference (EMI) shielding and other materials, improving sustainability. Improved EMI performance extends system life and reduces e-waste, further enhancing sustainability. More sustainable shielding materials are being developed for use when shielding is required. This article reviews the basics of EMI, examines common shielding materials to provide a baseline for comparing […]
How to determine noise figure: part 4
Two incompatible definitions of noise factor can lead to confusion, which you can alleviate by understanding where the differences lie.
How to determine noise figure: part 3
Noise factor and noise figure as defined in an IEEE standard can be derived from a two-port device’s equivalent noise temperature. In part 1 and part 2 of this series we discussed several ways to indicate the noise performance of a device under test (DUT). We first introduced the concept of noise factor based on […]
How to determine noise figure: part 2
The relationship between noise and temperature prompted a precursor of the IEEE to promulgate an alternative definition of noise figure in 1959. In part 1 of this series, we described the work of the Danish-American radio engineer Harald Friis, who described noise factor F of a device or system as the ratio of the input-power […]
What information does an eye diagram depict?
An eye diagram is a powerful visualization tool in digital communications and high-speed electronics to assess signal quality and channel performance. This FAQ will briefly explain an eye diagram and the overall and specific metrics engineers should know to understand an eye diagram. When capturing signals from a digital bitstream such as Ethernet or USB, […]
How to determine noise figure: part 1
A noise figure consolidates the effects of various noise types to provide a single specification for the noise performance of a component or system. In electronic circuits and systems, noise is an undesirable, inevitable disturbance in currents and voltages. Noise has many underlying fundamental causes. Thermal noise, also known as Johnson–Nyquist noise, results from random […]
How to interpret a QAM display: part 3
Error vector magnitude characterizes actual QAM signals’ deviations from their ideal locations due to nonlinearity and phase noise. In part 1 of this series, we discussed quadrature amplitude modulation (QAM), which results from summing orthogonal amplitude-modulated cosine and sine waves of the same frequency. In part 2, we looked at assigning bit sequences to QAM […]
