SUMMARY

2-49 SUMMARY The following paragraphs summarize the important points of this chapter. The SYNCHRONIZER is essential to any radar because it controls and times the operation of the entire system. Radar systems may be self-synchronized by triggers from the transmitter or externally synchronized from a master oscillator. Most modern systems are synchronized by a MASTER OSCILLATOR, which may be a SINEWAVE OSCILLATOR, an ASTABLE MULTIVIBRATOR, or a BLOCKING OSCILLATOR. Each of these oscillators fulfills the basic requirements of a synchronizer, which must be: · free running · stable in frequency · frequency variable (in steps) The TRANSMITTER produces the short-duration, high-power, rf pulses of energy that are radiated into space by the antenna. The MODULATOR controls the radar pulse, width and amplitude. KEYED-OSCILLATOR TRANSMITTERS produce a high-power output pulse by keying a high- power oscillator, such as a MAGNETRON. POWER-AMPLIFIER TRANSMITTERS amplify a low-level pulse to the desired power level using a series of microwave amplifiers such as TRAVELING-WAVE TUBES or KLYSTRONS. The DUPLEXER is a device that allows the same antenna to both transmit and receive. Most duplexers use the impedance characteristics of transmission lines and waveguides in conjunction with TR and ATR tubes to route the energy to the correct place. One of the most important functions of the duplexer is isolation of the receiver during transmission. The RECEIVER detects the very small target return echo and amplifies it to a usable level for display on the indicator. A typical SUPERHETERODYNE RECEIVER consists of a low-noise amplifier, a mixer, a local oscillator, an IF amplifier, a detector, and a video amplifier. Some special purpose receivers are the MOVING TARGET INDICATOR and MONOPULSE RECEIVERS. ANSWERS TO QUESTIONS Q1. THROUGH Q51. A1. Controls system operation and timing. A2. Timing and control. A3. Transmitter. A4. Free-running.