Product enclosures have frequency resonances that can produce unwanted EMI. Absorption materials in the cavity can reduce EMI. Use a cookie tin to compare materials before inserting them into your product. As operating frequencies approach microwaves, enclosures can appear as resonant cavities and amplify EMI emissions. When I was working on space shuttle communications systems, […]
spectrum analyzer
Signal analyzer combines spectrum and vector network analysis in three models
UNI-T announces the release of the UTS3000A Series Signal Analyzers, a spectrum analysis solution designed for complex RF environments. The series includes three models providing frequency coverage from 9 kHz to 8.4 GHz, offering spectrum analysis capabilities for various professional applications. The UTS3000A Series provides measurement precision suitable for contemporary signal analysis requirements. The analyzers […]
Characterize EMI from dc-dc converter ringing
Switching power supplies produce radiated and conducted emissions caused by ringing. Oscilloscope and spectrum-analyzer measurements let you see them. DC-DC converters are ubiquitous in most electronic products. While more efficient than linear regulators, they can also produce considerable amounts of interference that can affect nearby circuits. The measurements in this article show how ringing occurs […]
EMI from LED light fixture often exceeds regulatory limits
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 […]
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.
