8-19C: Receiving Systems

Question 1

8-19C1

Which of the following statements is true?

A. The front end of the receiver does not provide any amplification to the RADAR signal.
B. The mixer provides a gain of at least 6 db.
C. The I.F. amplifier is always a high gain, narrow bandwidth amplifier.
D. None of the above.

Answer 1

ANSWER A
On microwave frequencies, a point-contact crystal diode is used instead of solid state or tube amplifiers, as these circuits would generate excessive noise. The Schottky barrier diade offers an improvement in signal-to-noise ratio over point contact diodes. There is no front end amplification of the signal.

Question 2

8-19C2

Logarithmic receivers:
A. Can’t be damaged
B. Can’t be saturated.
C. Should not be used in RADAR systems.
D. Have low sensitivity.

Answer 2

ANSWER B
The logarithmic receiver has no gain control circuits with the linear log amplifier (lin-log) worklng for high amplitude signals, wlthout saturation. Exceptionally strong echoes will not saturate the amplifier, producing a small echo that might otherwise be undetected wlth a normal receiver going into saturation.

Question 3

8-19C6

In a RADAR receiver, the RF power amplifier:

A. Is high gain.
B. Is low gain.
C. Does not exist.
D. Requires wide bandwidth.

Answer 3

ANSWER C
In RADAR receivers, RF power amplifiers really don’t exist. They are used with transmitters, not receivers.