Subelement B: Transmitting Systems – 8 Key Topics – 8 Exam Questions— Topic 13: Modulation
Question 8-13B3
Element 8 (RADAR)A shipboard RADAR uses a PFN driving a magnetron cathode through a step-up transformer. This results in which type of modulation?
Explanation
A Pulse Forming Network (PFN) is designed to generate very high-voltage, short-duration electrical pulses. When these pulses are amplified by a step-up transformer and applied to the cathode of a magnetron, the magnetron rapidly turns on and off. Each electrical pulse from the PFN causes the magnetron to emit a corresponding burst, or "pulse," of microwave radio frequency (RF) energy.
This method of generating and transmitting discrete, short bursts of RF energy is precisely what defines pulse modulation. Radar systems rely on these distinct pulses to measure distance by timing the interval between transmitting a pulse and receiving its echo. Frequency modulation (FM) involves varying the carrier frequency, amplitude modulation (AM) varies the amplitude of a continuous carrier, and Continuous Wave (CW) is an unmodulated or simply keyed continuous signal, none of which describe the on-off, burst-like nature of a PFN-driven magnetron for radar.
Related Questions
8-13B1 In a solid-state RADAR modulator, the duration of the transmitted pulse is determined by:8-13B2 The modulation frequency of most RADAR systems is between:8-13B4 In a pulse modulated magnetron what device determines the shape and width of the pulse?8-13B5 What device(s) may act as the modulator of a RADAR system?8-13B6 The purpose of a modulator in the transmitter section of a RADAR is to: