The Backward Wave Oscillator BWO A backward wave
The Backward Wave Oscillator (BWO) • A backward wave oscillator (BWO) also called carcinotron( trade name) • It is a vaccum tube that is used to generate microwaves upto the terahertz range. • Belongs to TWT family with a wide electronic tuning range. • An electron gun generates an electron beam that is interacting with a slow-wave structure. • It sustains the oscillations by propagating a travelling wave backwards against the beam. • The generated EMW power has its group velocity directed oppositely to the direction of motion of the electrons. • The output power is coupled out near the electron gun. 1
The Backward Wave Oscillator (BWO) • The electron beam (from an electron gun) passes through a wire helix and generates an electric field that induces voltage with the helix wire. The resonating electric fields (in and out) produce microwaves in the direction opposite to the electron beam. • The frequency of the radiation is varied by controlling the beam velocity and the helix potential. 2
Applications of Microwave tubes • A klystron can be used either as a generator or as an amplifier of power, at microwave frequencies. Ø Klystron as power output tubes 1. Satellite communication ground station 2. Radar transmitters Ø The reflex klystrons are used in 1. 2. Radar receivers Local oscillator in microwave receivers • BACKWARD WAVE OSCILLATOR (BWO) 1. Shorter & Thicker TWT 2. Microwave CW oscillator 3. 1 -1000 GHz 3
The Backward Wave Crossed Field Amplifier • It is called AMPLITRON. • Pair of pins and the cavity is excited in opposite phase by the strap line. • Th electron beam and EM waves interact in the resonant circuits. • It is operated in S-band frequencies • It is used in high data rate transmission systems
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