# Analog & RF Filter Basics - AnswersRF Cafe Quiz #70

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.

Note: Some material based on books have quoted passages.

This Analog & RF Filter Basics Quiz targets those of you who are relative newcomers to the world of radio frequency (RF) electronics, but seasoned vets are welcome to give it a go as well. It addresses frequency response and physical construction. Images were obtained from Anatech Electronics documents entitled "Guideline for Choosing RF and Microwave Products" and "Understanding Filter Types and Their Characteristics." API Technologies' "RF & Microwave Filters," is also referenced. Please report any suspected errors to me via e-mail. Return to Quiz #70.

1.  The plot to the right is representative of amplitude and group delay responses for which type of analog filter?

Cheyshev filters exhibit amplitude ripple in the passband and monotonic roll−off in the stopband.

2. The photo to the right represents which type of filter construction?

a) Cavity
b) Ceramic
c) Crystal
d) Lumped element L/C (inductor/capacitor)
e) Tubular

a) Cavity

Cavity filters use a coil inside a cavity for interstage coupling and resonance. They typically have a very high "Q" and low insertion loss.

3.  The plot to the right is representative of amplitude and group delay responses for which type of analog filter?

a) Bessel
b) Butterworth
c) Chebyshev
d) Elliptical
e) Ideal

e) Ideal

An ideal filter exhibits perfectly flat amplitude and group delay (and phase) in the passband and infinite attenuation in the stopband. As the name implies, ideal filters cannot be realized in the real world.

4. The photo to the right represents which type of filter construction?

a) Cavity
b) Ceramic
c) Crystal
d) Lumped element L/C (inductor/capacitor)
e) Tubular

b) Ceramic

Ceramic filters exploit the electromechanical resonance of the substrate to pass or reject signals depending on the frequency.

5.  The plot to the right is representative of amplitude and group delay responses for which type of analog filter?

a) Bessel
b) Butterworth
c) Chebyshev
d) Elliptical
e) Ideal

a) Bessel

Bessel filters are referred to as maximally flat group delay filters with no deviation at the band edge, as the plot demonstrates.

6. The photo to the right represents which type of filter construction?

a) Cavity
b) Ceramic
c) Crystal
d) Lumped element L/C (inductor/capacitor)
e) Tubular

d) Lumped element L/C (inductor/capacitor)

A lumped element filter uses actual physical inductors and capacitors as resonant elements to determine whether specific frequencies are passed or blocked.

7.  The plot to the right is representative of amplitude and group delay responses for which type of analog filter?

a) Bessel
b) Butterworth
c) Chebyshev
d) Elliptical
e) Ideal

Butterworth filters are referred to as maximally flat amplitude filters because the passband does not have any insertion loss ripple.

8. The photo to the right represents which type of filter construction?

a) Cavity
b) Ceramic
c) Crystal
d) Lumped element L/C (inductor/capacitor)
e) Tubular

e) Tubular

Tubular (aka Coaxial) filters have inherently broad stopbands with very high rejection levels. They are often inserted inline with coaxial cable interconnects when unplanned interference needs to be handled.

9.  The plot to the right is representative of amplitude and group delay responses for which type of analog filter?

a) Bessel
b) Butterworth
c) Chebyshev
d) Elliptical
e) Ideal

Elliptical (aka Cauer) filters have the highest theoretical stopband attenuation roll−off for a given number of poles.

10. The photo to the right represents which type of filter construction?

a) Cavity
b) Ceramic
c) Crystal
d) Lumped element L/C (inductor/capacitor)
e) Tubular

c) Crystal

Crystal filters rely on the electromechanical resonance properties of (most often) quartz crystals that are shaped and sized for resonance at specific frequencies.

Posted August 19, 2020