Subelement B: Transmitting Systems – 8 Key Topics – 8 Exam Questions— Topic 13: Modulation
Question 8-13B5
Element 8 (RADAR)What device(s) may act as the modulator of a RADAR system?
Explanation
In a RADAR system, the modulator's primary function is to generate high-power, short-duration pulses that turn the microwave RF source (like a magnetron or klystron) on and off. This creates the pulsed radio waves characteristic of RADAR.
**D) Thyratron or a silicon-controlled rectifier (SCR):** Both thyratrons (a type of gas-filled vacuum tube) and SCRs (a solid-state semiconductor device) are high-speed, high-power electronic switches. They are perfectly suited to rapidly switch the high voltage and current required to pulse the microwave oscillator or amplifier in a RADAR transmitter, thereby acting as the modulator.
**A) Magnetron:** A magnetron is a high-power microwave oscillator that *generates* the RF energy. It requires an external modulator to pulse its output.
**B) Klystron:** A klystron is a high-power microwave amplifier or oscillator. Like a magnetron, it also needs an external modulator to create the necessary pulses.
**C) Video amplifier:** A video amplifier processes signals at much lower frequencies, typically for display or signal processing after detection, not for switching the high-power RF transmission.
Related Questions
8-13B3 A shipboard RADAR uses a PFN driving a magnetron cathode through a step-up transformer. This results in which type of modulation?8-13B4 In a pulse modulated magnetron what device determines the shape and width of the pulse?8-13B6 The purpose of a modulator in the transmitter section of a RADAR is to:8-14B1 The pulse developed by the modulator may have an amplitude greater than the supply voltage. This is possible by:8-14B2 Pulse transformers and pulse-forming networks are commonly used to shape the microwave energy burst RADAR transmitter. The switching devices most often used in such pulse-forming circuits are: