CDC Vol 1, 007 Basic Radar Principles

Question 1

• Define a radio wave.

Answer 1

A burst of energy that is transmitted by a radar sensor through the atmosphere or space.

Question 2

• What is the part of the radio wave that bounces back to the antenna?

Answer 2

An echo or return.

Question 3

• Identify the “brain” of the radar system. Why is that so?

Answer 3

The synchronizer, because it coordinates the operation of the various parts of the radar.

Question 4

• Explain the function of the modulator.

Answer 4

To provide an extremely large, very short square wave pulse of DC voltage to the transmitter.

Question 5

• What device allows a single antenna to both transmit and receive?

Answer 5

The duplexer.

Question 6

• What is the antenna’s purpose during transmission and reception?

Answer 6

Its function during transmission is to concentrate the radiated energy into a shaped beam that points in the desired direction into space. On reception, the antenna collects the energy contained in the echo signal and delivers it to the receiver.

Question 7

• What component of the radar separates wanted from unwanted signals?

Answer 7

The receiver

Question 8

• Define the terms “PRF” and “PRT” and explain why they are important.

Answer 8

The PRF is the number of times the radar transmits per second. The length of time between transmissions when the radar is not transmittingis the resting time. Transmission time, plus resting time (or the time from the beginning of one pulse to the next) we call the PRT. A lower PRF means a longer PRT. The longer the resting (listening) time of the radar, the more time there is for the transmitted pulse to go out, strike a target, and return. Thus, the lower the PRF, the greater is the range of the radar system.

Question 9

The word radar is an acronym for?

Answer 9

Radio Detection and Ranging

Question 10

What is the object that reflected the radio wave called?

Answer 10

Target

Question 11

How is azmith and range of a target determined?

Answer 11

• Azimuth is determined by the direction the antenna is facing.
• Range is determined by the amount of time it takes the echo to return.

Question 12

What is a radio wave or burst of energy also called?

Answer 12

Electromagnetic wave

Question 13

Pulse Repetition Frequency (PRF) = ____

Answer 13

The number of times the radar transmits per second.

Question 14

Pulse Repetition Time (PRT) = ____

Answer 14

Transmission time + rest time = PRT

Question 15

What are the benefits and negatives of a low PRF?

Answer 15

• Benefit: greater range

- Negative: more susceptible to interference

Question 16

What are the basic radar components?

Answer 16

1. Frequency Generator
2. Modulator
3. Transmitter
4. Duplexer
5. Antenna
6. Receiver Protector
7. Receiver
8. Display
9. Synchronizer

Question 17

Will a lower pulse repetition frequency (PRF) increase or decrease the range of a radar?

Answer 17

Increase

Question 18

What radar component coordinates the operation of the various parts of the radar and is the “brain” of a basic pulse radar?

Answer 18

Synchronizer

Question 19

What radar component provides an extremely large, very short, square-wave pulse of DC voltage to the transmitter?

Answer 19

Modulator

Question 20

What radar component delivers a series of high-energy burst RF energy and amplifiers to create the radar signal transmitted through the antenna?

Answer 20

Transmitter

Question 21

What radar component is required when the transmitter and receiver used the same antenna?

Answer 21

Duplexer

Question 22

What radar components primary purpose is to ensure a circuit failure does not cause RF energy transmitted by the radar to enter and overload the radar’s receivers?

Answer 22

Receiver Protectors

Question 23

What radar component concentrates the radiated energy into a shaped beam?

Answer 23

The Autenna

Question 24

What radar component has the purpose of the display is to visually present the information contained in the radar echo signal in a form suitable for your interpretation and action?

Answer 24

Display

Question 25

What radar component function is to detect desired echo signals in the presence of noise, interference, or clutter and must separate wanted from unwanted signals to a level where target information can be displayed?

Answer 25

Receiver

Question 26

What radar component has crystals that produce one of the several possible stable local oscillators?

Answer 26

Frequency Generator