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2-1 CHAPTER 2 RADAR SUBSYSTEMS LEARNING OBJECTIVES Upon completion of this chapter, the student will be able to: 1. Describe, in general terms, the function of a radar synchronizer. 2. State the basic requirements and types of master synchronizers. 3. Describe the purpose, requirements, and operation of a radar modulator. 4. Describe the basic operating sequence of a keyed-oscillator transmitter. 5. Describe the basic operating sequence of a power-amplifier transmitter. 6. State the purpose of a duplexer. 7. State the operational principles of tr and atr tubes. 8. Describe the basic operating sequence of series and parallel connected duplexers. 9. List the basic design requirements of an effective radar receiver. 10. List the major sections of a typical radar receiver. 11. Using a block diagram, describe the operational characteristics of a typical radar receiver. INTRODUCTION TO RADAR SUBSYSTEMS Any radar system has several major subsystems that perform standard functions. A typical radar system consists of a SYNCHRONIZER (also called the TIMER or TRIGGER GENERATOR), a TRANSMITTER, a DUPLEXER, a RECEIVER, and an INDICATOR. These major subsystems were briefly described in chapter 1. This chapter will describe the operation of the synchronizer, transmitter, duplexer, and receiver of a typical pulse radar system and briefly analyze the circuits used. Chapter 3 will describe typical indicator and antenna subsystems. Because radar systems vary widely in specific design, only a general description of representative circuits is presented in this chapter. SYNCHRONIZERS The synchronizer is often referred to as the "heart" of the radar system because it controls and provides timing for the operation of the entire system. Other names for the synchronizer are the TIMER and the KEYER. We will use the term synchronizer in our discussion. In some complex systems the synchronizer is part of a system computer that performs many functions other than system timing.