Conducted emissions from LED light fixtures at frequencies from 1 MHz to 30 MHz can interfere with amateur radio and several broadcast bands. Radiated emissions reach into the lower cellular bands. After recently moving to northern Colorado and setting up my EMC lab and amateur radio station in the basement, I wanted to update the […]
spectrum analyzer
How to calculate and apply the inverse discrete Fourier transform: part 4
In part 3 of this series, we used the inverse fast Fourier transform (IFFT) to create 100-Hz time-domain waveforms of various amplitudes and phases. We can also use the IFFT to create waveforms containing multiple frequencies. If you look closely at Figure 1 in part 1 of this series, you’ll notice that the time-domain waveform […]
How to calculate and apply the inverse discrete Fourier transform: part 3
The inverse transform can create a time-domain waveform where no waveform has been before. In part 2 of this series, we used the discrete Fourier transform to convert a waveform from the time domain to the frequency domain, operated on the frequency-domain data, and used the inverse transform to reconstruct the altered time-domain waveform. That’s […]
Free and low-cost online EE tools aid in design
Downloadable and online free and low-cost EE tools help engineers design and analyze circuits.
How to calculate and apply an inverse FFT: part 2
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 […]
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 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.
Flea market vintage test equipment, September 2024
The monthly “Flea at MIT” featured an abundance of test equipment. We even bought some.
Should I use a spectrum, signal, or vector network analyzer? part 3
In part 2 of this series, we looked at a swept-tuned spectrum analyzer and how it could sweep a frequency span of interest from 1 MHz to 1.1 MHz with a sweep time of 50 msec. As Figure 1 shows, the analyzer readily identifies a signal at 1.03 MHz but misses the intermittent signals shown […]
Should I use a spectrum, signal, or vector network analyzer? part 2
An analog spectrum analyzer’s sweep time can hide intermittent unwanted signals. In part 1 of this series, we examined a simplified block diagram of a traditional analog spectrum analyzer, which includes an RF frontend, mixer, voltage-controlled oscillator (VCO), intermediate-frequency (IF) stage, sweep generator, envelope detector, and display. We also looked at resolution bandwidth (RBW), the […]
