Chapter 2 Basic Radar Systems

CHAPTER 2 BASIC RADAR SYSTEMS LEARNING OBJECTIVES Upon completing this chapter, you should be able to do the following: 1. Describe the two types of energy transmission used by radar systems. 2. Describe the different seaming techiques used in radar systems. 3. Describe the major components in today’s radar transmitters. 4. List the basic design requirements of an effective radar receiver. INTRODUCTION Basic Pulse-Radar System The two basic types of radar systems, pulse radars and continuous-wave radars, use pulse and contin- uous-wave energy transmission. As a Fire Control- man, you need to know how these systems work. This chapter discusses radars, scanning methods, transmit- ters, and receivers in detail. For further information on radar systems, refer to Microwave Principles, Module 11, Navy Electricity and Electronics Training Series, NAVEDTRA 172- 11-00-87; and Radar Principles, Module 18, Navy Electricity and Electronics Training Series, NAVED- TRA 172-18-00-84. RADAR SYSTEMS This section discusses the two types of pulse radars and the two types of continuous-wave radars. PULSE-RADAR SYSTEMS The pulse-radar systems include radar and the pulse-Doppler radar. The signal of a basic pulse-radar system is gen- erated by the transmitter and is radiated into space by the antenna. Intermediate frequencies from 30 to 60 MHz are commonly used because signal handling is easier to accomplish at the lower frequencies than at the transmitter frequencies. The duplexer enables the use of a single antenna to transmit and receive the radar signal. The return echo signal is then mixed with a local oscillator (LO) signal to produce an intermediate frequency (IF) signal at a lower frequency than the transmitter. The IF filter conditions the echo signal through amplifying and filtering extraneous signals. The IF signal is then sent to the second detector where the IF is converted to a lower frequency video signal. At that time, the video signal is processed for display by a video amplifier. The display is usually a cathode-ray tube (CRT) the basic pulse that is monitored by an operator. The timer/synchro- nizer controls the repetition frequency of the trans- 2-1