Frequency-Agile Antennas for Wireless Communications

Answers to RF Cafe Quiz #57

Return to RF Cafe Quiz #57

This quiz is based on the information presented in Frequency-Agile Antennas for Wireless Communications, by Aldo Petosa.

Note: Some of these books are available as prizes in the monthly RF Cafe Giveaway.

1.  To which class of antennas do frequency agile antennas (FAAs) belong?

c)  Active integrated antennas (AIAs)

In the context of this book, FAAs can be considered to belong to the larger class of antennas known as AIAs.

  (see page 3)

2.  How does antenna gain differ from antenna directivity?

d)  Gain accounts for losses as well as directivity

Directivity is a ratio of power relative to specific directions where losses up to the feed point are already accounted for. An ideal antenna can be perfectly directional but still exhibit a loss.

  (see page 9)

3.  What are the two types of tuning used in FAAs?

a)  Discrete and continuous

Discrete tuning alters the frequency to a fixed number of distinct values while continuous tuning can take on any tuning value.

  (see page 15)

4.  When did microstrip antennas start coming into common use?

c)  In the 1970s

Microstrip circuit technology was introduced in the 1960s, and microstrip antennas followed in the mid 1970s.

  (see page 35)

5.  For which microstrip patch antenna formats does Frequency-Agile Antennas for Wireless Communications provide field equations?

a)  Rectangular, dipole, circular, and annular (ring)

The basic design equations are given for a few of the most popular microstrip patch antennas.

  (see sub-chapter 3.4)

6.  What type of tuning is typically available for antennas?

d)  All the above

  (see page 87)

7.  How can the permittivity of ferroelectric substrates be altered?

b)  By applying an electric field

Ferroelectric substrates offer a behavior analogous to ferrites, where the permittivity of the ferroelectric can be altered by the application of a static electric field.

  (see Table 4.3 on page 103)

8.  What methods of mechanical tuning are practical for frequency agile antennas (FAAs)?

d)  All the above

The types of actuators used include electrostatic, piezoelectric, magnetostatic, hydraulic, and pneumatic. Information for each example includes tuning range, total spectrum, bias requirements, and antenna performance.

  (see page 149)

9.  What is a major advantage of liquid crystals over ferroelectric substrates?

a)  Lower bias voltage

The advantages of liquid crystals over ferroelectrics include the much lower bias voltages required and the inherently low values of the dielectric constant.

  (see page 194)

10.  What is the most widely used component type for continuous tuning FFAs?

d)  Varactor diodes

The majority of continuous tuning schemes use varactor diodes.

  (see Table 7.1 on page 279)