LearnEMC

LearnEMC helps companies build the in-house expertise they need to ensure their products will meet electromagnetic compatibility requirements.

[LearnEMC @LearnEmc]

EMC Question of the Week: A 100-MHz sine wave with a peak-to-peak amplitude of 2 volts is measured with a 50-Ω EMI test receiver. A single narrow-band spike is observed at 100 MHz. What is the quasi-peak amplitude of that spike?
Answer at https://t.co/T47iXeZV1l.

[LearnEMC @LearnEmc]

EMC Question of the Week: 1-kΩ resistors in series with the low-speed inputs of a microprocessor can help a product meet
a.) radiated emissions requirements
b.) ESD requirements
c.) both of the above
d.) none of the above
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: A 5-MHz square wave has 1-ns transition times and a peak-to-peak amplitude of 1.0 volt. What is the amplitude of the harmonic at 125 MHz as measured on a spectrum analyzer?
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: Each of the four circuits in the figure has a switch that closes at t=0. Which circuit will be the first to develop 9 volts across the capacitor?
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: What can we conclude from the near-field probe measurement depicted in the photo that shows 40 dB(μV) peaks between 30 and 50 MHz? Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: Which of the following is a visual aid that is useful for analyzing certain transmission line problems in the frequency domain?
a) Bounce Diagram
b) Triboelectric Series
c) Smith Chart
d) Bob Smith Termination
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: A shielded twisted pair connects a small sensor board to a controller board. The sensor board has a plastic enclosure. How and where should the cable shield be connected?
Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: A 1.0-volt, 100-Mbps, single-ended signal driver sends a signal to a matched load on a 1-meter cable. Which of the cable options in the figure is least likely to cause a radiated emissions problem?
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: Class II ceramic capacitors (e.g., X7R) are well-suited for

a.) DC power bus decoupling
b.) AC power bus decoupling
c.) high-pass filtering
d.) none of the above

Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: At 60 Hz, aluminum foil can effectively shield
a.) electric fields
b.) magnetic fields
c.) both of the above
d.) none of the above
Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: How fast can you draw charge from two parallel planes separated by a distance of 0.25 mm when they are initially charged to 1 volt? 
Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: Within the first 200 ps of a sudden demand for current to the BGA in the figure below, where is most of the current coming from?
a.) C1
b.) C2
c.) C1 and C2 equally
d.) the plane capacitance

Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: Assuming the product meets its EMC requirements, this PCB layer is almost certainly a layer devoted to
a.) high-speed signals
b.) power distribution
c.) RTN
d.) GND
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: The initial spike from an ESD simulator discharged into a calibration target is primarily due to the
a.) simulator's capacitor
b.) simulator's switch
c.) simulator's self-capacitance
d.) target's center plate
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: Which output in the figure corresponds to the measured voltage from a small 15-nH loop placed over a circuit board trace. The trace carries a current that looks like a 250-MHz square wave.

Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: A 1-Gbps signal is routed on a trace that is 0.25 mm above the return plane. This trace should normally have a
a.) balanced termination
b.) coplanar ground
c.) controlled impedance
d.) all of the above
Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: A plane wave is incident on long parallel wires that have different diameters. Which of the following statements is correct?
a.) ICM = I1 + I2
b.) IDM = 0
c.) VDM = 0
d.) all of the above
Full question and answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: In order to filter the common-mode power bus noise effectively, which of the components shown in the schematic must be eliminated?
a.) L2
b.) L3
c.) CX1 and CX2
d.) CX4 and CX5
Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: Small unconnected copper dots or diamonds on the outer layers of a printed circuit board are an example of
a.) ground fill
b.) via stitching
c.) guard posts
d.) thieving

Answer at https://t.co/T47iXeZnbN.

[LearnEMC @LearnEmc]

EMC Question of the Week: What determines the location of the nulls in the (sin x)/x shape in the plot below?
a.) transition time
b.) duty cycle
c.) fundamental frequency

Full question and answer at https://t.co/T47iXeZnbN.