Question of the Week - Answer 180326https://learnemc.com/qotw-180326

EMC Question of the Week: March 26, 2018 Which of the following is a common reason for connecting the shield of a long cable to ground through a capacitor? to prevent unsafe currents from flowing in the cable shield to reduce radiated emissions by...

Question of the Week - Answer 260105https://learnemc.com/qotw-260105

EMC Question of the Week: January 5, 2026 A switching power supply with a fixed duty cycle creates narrow impulses that appear at a repetition rate equal to the switching frequency. For measurements in the frequency range from 30 to 1000 MHz with a 120...

Question of the Week - Answer 251208https://learnemc.com/qotw-251208

EMC Question of the Week: December 8, 2025 The datasheet for a DC-to-DC power converter (12 V to 3.3 V) switching at 1 MHz recommends the layout shown in the figure. All components are on Layer 1. Layer 2 is a solid return (GND) plane. Which of the...

Question of the Week - Answer 191223https://learnemc.com/qotw-191223

EMC Question of the Week: December 23, 2019 The decibel is a unit named in honor of, Alexander Graham Bell Kristen Bell Harry Belafonte Heinrich Decibel Answer The correct answer is "a". In the 1920s, Bell Telephone Laboratories proposed the decibel as...

Question of the Week - Answer 221121https://learnemc.com/qotw-221121

EMC Question of the Week: November 21, 2022 The purpose of the capacitors in the figure is to provide low-pass filtering high-pass filtering power bus decoupling propagation delay Answer The best answer is “b.” These are DC-blocking capacitors on...

Question of the Week - Answer 180122https://learnemc.com/qotw-180122

EMC Question of the Week: January 22, 2018 The Method of Moments is a popular numerical electromagnetic modeling technique. Another name for the same technique is, Finite Element Method Finite Difference Time Domain Method Method of Least Squares...

Question of the Week - Answer 190318https://learnemc.com/qotw-190318

EMC Question of the Week: March 18, 2019 When a circuit board with a plane layer devoted to "ground" is mounted on a metal surface or in a metal box, the board ground should always be connected to the exterior metal at only one location away from the...

Question of the Week - Answer 181022https://learnemc.com/qotw-181022

EMC Question of the Week: October 22, 2018 On a digital oscilloscope or real-time spectrum analyzer, what effect does increasing the sampling rate in the time domain have on the signal displayed in the frequency domain? better frequency resolution...

Question of the Week - Answer 210405https://learnemc.com/qotw-210405

EMC Question of the Week: April 5, 2021 Two 0603 MLCC capacitors are used to decouple a single power input of an IC. One of them has a nominal value of 0.10 μF. For the best high-frequency performance, the other one should have a value of 0.10 μF 10 μF...

Question of the Week - Answer 230522https://learnemc.com/qotw-230522

EMC Question of the Week: May 22, 2023 If a pulse-width-modulated signal has a fixed transition time, which duty cycle produces the most power at the switching frequency? 1% 10% 50% 90% Answer The best answer is “c.” The signal power at DC is...

Question of the Week - Answer 220328https://learnemc.com/qotw-220328

EMC Question of the Week: March 28, 2022 Which specification of an EMI test receiver is used to determine the noise floor? 1-dB gain compression Nominal Dynamic Range (NDR) Displayed Average Noise Level (DANL) Level Measurement Uncertainty (LMU) Answer...

Question of the Week - Answer 221205https://learnemc.com/qotw-221205

EMC Question of the Week: December 5, 2022 An LISN (or AMN) used for conducted emissions measurements always measures the voltage between a power input and a power input return circuit ground system ground the earth Answer The best answer is “c.” LISN...

Question of the Week - Answer 260216https://learnemc.com/qotw-260216

EMC Question of the Week: February 16, 2026 In a conducted emissions test setup, the DUT is 40 cm from a vertical metal plane. Changing the separation distance from 40 cm to 20 cm, we would expect the value of the parasitic capacitance to the plane...

Question of the Week - Answer 190708https://learnemc.com/qotw-190708

EMC Question of the Week: July 8, 2019 Products that connect exposed metal to the earth ground in the power cord for safety rely on the earth to act as an infinite current sink fuses or circuit breakers to remove power in the event of a short...

Question of the Week - Answer 201026https://learnemc.com/qotw-201026

EMC Question of the Week: October 26, 2020 Which of the following transient protection components is a "crowbar" device (so called, because it acts like a short circuit when the voltage across its terminals exceeds the threshold)? TVS diode varistor...

Question of the Week - Answer 240610https://learnemc.com/qotw-240610

EMC Question of the Week: June 10, 2024 For a differential trace pair, terminating each trace in the odd-mode impedance provides a matched termination for both the odd-mode and even-mode propagation provided the coupling between the traces is strong...

Question of the Week - Answer 180430https://learnemc.com/qotw-180430

EMC Question of the Week: April 30, 2018 The input impedance of a lossless 50-Ω transmission line terminated with a 50-Ω load resistance is, 50 Ω 100 Ω 50 Ω + j50 Ω dependent on the length of the transmission line Answer The correct answer is "a." The...

Question of the Week - Answer 181105https://learnemc.com/qotw-181105

EMC Question of the Week: November 5, 2018 If the amplitude of a periodic time-domain signal is doubled, the amplitude of its harmonics in the frequency domain remains the same increases by 40% doubles quadruples Answer The correct answer is "c". The...

Question of the Week - Answer 190107https://learnemc.com/qotw-190107

EMC Question of the Week: January 7, 2019 In an electric vehicle, the three phase wires connecting the motor drive to the traction motor should be unshielded be individually shielded have a shield around all three wires both b. and c. Answer The best...

Question of the Week - Answer 171127https://learnemc.com/qotw-171127

EMC Question of the Week: November 27, 2017 At the surface of a perfect conductor, the normal component of the electric field is zero the tangential component of the electric field is zero the tangential component of the magnetic field is zero all of...

Question of the Week - Answer 260504https://learnemc.com/qotw-260504

EMC Question of the Week: May 4, 2026 If a microstrip trace carrying a digital signal extends a distance that exceeds its "critical length," it's generally necessary to slow the signal transition time provide a matched termination either (a.) or (b.)...

Question of the Week - Answer 210705https://learnemc.com/qotw-210705

EMC Question of the Week: July 5, 2021 The crosstalk between two matched 50-Ω stripline traces plotted as a function of frequency has a maximum value of -30 dB. If the distance between the traces is increased, reducing the mutual capacitance between...

Question of the Week - Answer 170529https://learnemc.com/qotw-170529

EMC Question of the Week: May 29, 2017 In a radiated emissions test, if the even harmonics of a digital clock frequency are higher than the odd harmonics, the primary noise source is likely to be, clock nets data nets cables power bus noise Answer The...

Question of the Week - Answer 210816https://learnemc.com/qotw-210816

EMC Question of the Week: August 16, 2021 Testing an EUT on a 30-meter open-field site, an EMI test receiver measures a 29 dB(μV/m) peak at 100 MHz. With the DUT powered off, the measured signal amplitude is 26 dB(μV/m). What is the likely amplitude of...

Question of the Week - Answer 230116https://learnemc.com/qotw-230116

EMC Question of the Week: January 16, 2023 If a circuit board has single-ended analog circuits operating at 100 MHz and single-ended digital circuits operating at 100 Mbps, the return currents should almost always be routed on the same plane(s) the...

Question of the Week - Answer 250526https://learnemc.com/qotw-250526

EMC Question of the Week: May 26, 2025 A 1-Mbps digital signal is transmitted across a circuit board, through a connector, and on to a shielded wiring harness. An RC low pass filter is used to limit the bandwidth of the transmitted signal. Which filter...

Question of the Week - Answer 210201https://learnemc.com/qotw-210201

EMC Question of the Week: February 1, 2021 When deciding whether it is necessary to use a matched termination on a digital signal trace, it's important to compare the propagation delay to the signal's bit rate transition time clock period jitter Answer...

Question of the Week - Answer 221107https://learnemc.com/qotw-221107

EMC Question of the Week: November 7, 2022 The EMC test set-up in the photo is designed for measuring CISPR 32 radiated emissions CISPR 12 radiated emissions electrostatic discharge immunity radiated immunity Answer The best answer is “d.” The first...

Question of the Week - Answer 170522https://learnemc.com/qotw-170522

EMC Question of the Week: May 22, 2017 Some of the power in differential-mode signals propagating down a transmission line is converted to common-mode power when there is a change in the transmission line's, characteristic impedance propagation...

Question of the Week - Answer 220530https://learnemc.com/qotw-220530

EMC Question of the Week: May 30, 2022 For a rectangular metal enclosure whose length is greater than its width, and whose width is greater than its height, the lowest resonant frequency is a function of its length only length and width only length,...

Question of the Week - Answer 230717https://learnemc.com/qotw-230717

EMC Question of the Week: July 17, 2023 A clock driver sends a 10-Mbps clock signal to 4 devices spread out on a 10-cm x 10-cm printed circuit board. Each device has a 5-pF input capacitance, and the signals are routed on microstrip traces. What...

Question of the Week - Answer 250127https://learnemc.com/qotw-250127

EMC Question of the Week: January 27, 2025 A 5-Ω digital signal source drives a 10-nF load through a lossless, 1-m cable with a propagation delay of 5.6 ns. The characteristic impedance of the cable is 50 Ω. What is the transition time of the received...

Question of the Week - Answer 220221https://learnemc.com/qotw-220221

EMC Question of the Week: February 21, 2022 The "rabbit ears" antenna shown in this figure is a dipole antenna two monopole antennas a horn antenna a phased array Answer The correct answer is “a.” The two extendable "rabbit ears" are the two elements...

Question of the Week - Answer 230227https://learnemc.com/qotw-230227

EMC Question of the Week: February 27, 2023 To reduce circuit board conducted and radiated emissions due to switching noise, choose DC-to-DC converters that have the smallest possible switching frequency footprint quiescent current output current...

Question of the Week - Answer 231002https://learnemc.com/qotw-231002

EMC Question of the Week: October 2, 2023 A GNSS signal (1.6 GHz) is conveyed from an antenna to a circuit board on a coaxial cable. On the circuit board, the center conductor of the cable is connected to the receiver via a 5-cm trace. The coaxial...

Question of the Week - Answer 181015https://learnemc.com/qotw-181015

EMC Question of the Week: October 15, 2018 To send a 10 Mbps CMOS digital signal a distance of 20 cm on a microstrip circuit board trace, you must use a controlled-impedance trace and matched termination use a controlled-impedance trace and matched...

Question of the Week - Answer 220725https://learnemc.com/qotw-220725

EMC Question of the Week: July 25, 2022 A high-speed digital signal source on a circuit board produces the pseudo-differential outputs SIG+ and SIG-. When SIG+ is 3.3 V (relative to the ground plane), SIG- is 0V. When SIG+ is 0 V, SIG- is 3.3V. If SIG+...

Question of the Week - Answer 230508https://learnemc.com/qotw-230508

EMC Question of the Week: May 8, 2023 A common-mode current probe measures 10 μA of current at 50 MHz on a shielded twisted pair cable. The twisted wire pair itself carries 30 μA of common-mode current at 50 MHz. How much 50-MHz current flows on the...

Question of the Week - Answer 251110https://learnemc.com/qotw-251110

EMC Question of the Week: November 10, 2025 A digital clock source (5 Mbps, 2 Ω) provides a signal to three devices on the same printed circuit board. Each of the three device inputs is a 5-pF capacitance and is connected to the source with a 10-cm...

Question of the Week - Answer 230710https://learnemc.com/qotw-230710

EMC Question of the Week: July 10, 2023 Which type of induced transient in an EMC compliance test generally has the greatest time-rate-of-change in voltage (i.e., the highest dV/dt)? ESD EFT damped sinusoid lightning Answer The best answer is “a.” An...

Question of the Week - Answer 200413https://learnemc.com/qotw-200413

EMC Question of the Week: April 13, 2020 An unmatched CMOS digital input can usually be modeled, to a first order, as a resistance of 50 to 100 Ω a resistance of 5 to 10 kΩ an inductance of 5 to 10 nH a capacitance of 5 to 10 pF Answer The correct...

Question of the Week - Answer 170424https://learnemc.com/qotw-170424

EMC Question of the Week: April 24, 2017 The DC resistance of a half-ounce copper plane in a circuit board is approximately, 1 mΩ per square 100 mΩ per square 1 Ω per square 100 Ω per square Answer The correct answer is "a". This can be confirmed by...

Question of the Week - Answer 200713https://learnemc.com/qotw-200713

EMC Question of the Week: July 13, 2020 The best layer stack-up for a 6-layer printed circuit board is, S-S-P-G-S-S S-G-S-S-P-S SP-G-S-S-G-S none of the above Answer The best answer is "d". The truth is there is no guideline for the optimum layer...

Question of the Week - Answer 170917https://learnemc.com/qotw-170917

EMC Question of the Week: September 17, 2017 The ratio of the electric field strength to the magnetic field strength for a wave propagating in RG58 coaxial cable (Z0 = 50 Ω, εr =2.3) is, 50 Ω 250 Ω 377 Ω > 10 MΩ Answer The correct answer is "b". The...

Question of the Week - Answer 200518https://learnemc.com/qotw-200518

EMC Question of the Week: May 18, 2020 To send a 1 Mbps CMOS digital signal a distance of 20 cm on a ribbon cable, it's important to use a matched termination use Manchester encoding control the transition time use a ferrite on the cable Answer The...

Question of the Week - Answer 201207https://learnemc.com/qotw-201207

EMC Question of the Week: December 7, 2020 Generally, the best way to send a high-speed differential signal, V+ and V-, on an unshielded three-wire ribbon cable is to use the two outer wires one inner and one outer wire V+ on inner and V- on both outer...

Question of the Week - Answer 210927https://learnemc.com/qotw-210927

EMC Question of the Week: September 27, 2021 The common-mode rejection ratio of an ideal differential receiver is 0 0 dB 6 dB infinite Answer The correct answer is “d.” The gain a differential amplifier is the ratio of its output voltage to its...

Question of the Week - Answer 200420https://learnemc.com/qotw-200420

EMC Question of the Week: April 20, 2020 At what frequencies do currents on a circuit board take the path(s) of least resistance? DC only kHz frequencies and lower MHz frequencies and higher all frequencies Answer The best answer is "b". Currents tend...

Question of the Week - Answer 231211https://learnemc.com/qotw-231211

EMC Question of the Week: December 11, 2023 The input to a 1-MHz inverting buck-boost converter is +5 V and the output is -3.3 V. Which of the board layouts shown here is least likely to exhibit unacceptable conducted or radiated emissions if layer 2...

Question of the Week - Answer 260302https://learnemc.com/qotw-260302

EMC Question of the Week: March 2, 2026 For a differential signal propagating on a balanced pair of microstrip traces, what is the difference between differential-mode propagation and odd-mode propagation? differential-mode is undefined odd-mode is...