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# Introduction to RF Design Using EM Simulators Answers to RF Cafe Quiz #41

All RF Cafe Quizzes make great fodder for employment interviews for technicians or engineers - particularly those who are fresh out of school or are relatively new to the work world. Come to think of it, they would make equally excellent study material for the same persons who are going to be interviewed for a job. Bonne chance, Viel Glück, がんばろう, buena suerte, удачи, in bocca al lupo, 행운을 빕니다, ádh mór, בהצלחה, lykke til, 祝你好運. Well, you know what I mean: Good luck!

Note: Some material based on books have quoted passages.

This quiz is based on the information presented in Introduction to RF Design Using EM Simulators, by James C. Rautio, published by Artech House. Note: Some of these books are available as prizes in the monthly RF Cafe Giveaway.

1.  What is an electric field?

d)  The potential gradient in space caused by voltage on a conductor

"The electric field is the potential gradient caused by the voltage of the power supply (electric potential difference) in the space around lines.  (see page 3)

2.  Where is current flow strongest on a microstrip line?

a)  Along the edge

Viewed from above, we see that current distribution is not uniform across the width of the line. It flows most strongly along both edges of the line.  (see page 11)

3.  What is a meander line?

c)  A transmission line that snakes back and forth along its length

(see page 38)

4.  Although microstrip lines are modeled as equivalent lumped element circuits, they are actually:

b)  Distributed elements

Microstrip lines are distributed circuits.  (see page 93)

5.  Why are microstrip line corners mitered in a bend?

a)  To reduce signal reflections

The mitered bend has substantially less reflection since a square corner distorts the electromagnetic field, causing a reflected wave.  (see page 51)

6.  How can crosstalk between metal lines be reduced?

d)  All the above

Electromagnetic field lines between two or more lines can couple enough to induce interference. The trick is to reduce that coupling.  (see page 86)

7.  How does current in the ground plane flow relative to the microstrip line above it?

d)  Like a mirror image

When we look at the current on the ground plane, we see that most of it flows almost like a mirror image on the MSL directly above it.  (see page 133)

8.  What is a main motivation for using a differential pair transmission line?

a)  Crosstalk reduction

The second line carries the return current rather than the ground plane, so less signal current flows in the ground plane.   (see page 161)

9.  Which waveguide mode has the magnetic field component pointing in the direction of the electromagnetic (EM) wave travel?

c)  Transverse Electric (TE) mode

The TE mode has all of the electric field perpendicular to the direction of travel of the EM wave. There is some magnetic field pointing in the direction of travel.  (see page 223)

10.  What is the main limit of a simulator's accuracy?

b)  Digitization increment size

No matter how much we refine the cells or mesh, we cannot completely eliminate error.

(see page 270)