537 questions and answers
Write short notes on
At microwave frequency, the value of L and C will be so small that they cannot be practically realizable. At microwave the cavity resonator the cavity resonator can generate oscillation like L.C tuned circuit. When a short is placed across the waveguide, the wave reflected by the short, forms a standing wave along with the incident wave.
Write short note on Magnetron Oscillator.
The magnetron cross section view and field distribution inside the magnetron are presented in Fig. 38(a) and 2 respectiv. The reason behind the development of magnetron tube was the requirement of high power during the time of 2nd world war though it was invented by Hull in 1921. The basic structure of a magnetron is a number of identical resonators arranged in a cylindrical pattern around a cylindrical cathode.
What is a slow wave structure? Why does the TWT need such a structure? Explain the beam and RF interaction in such wave tube.
The slow wave structures are a special type of circuits, used in microwave tubes to reduce the wave velocity in a certain direction so that a prolonged interaction between the electron beam and the signal wave may take place.
Compare and contrast the bunching operation in a two cavity klystron and reflex klystron.
The Klystron tube operates on the principle of velocity modulation inst of current density modulation employed in conventional tubes. The idea of Klystron Amplifier was introduced by Varian brothers in 1939. The typical diagram of two cavity Klystron amplifier is depicted in Fig. 31. It consists of electron gun, buncher cavity, catcher cavity and collector. Electrons emitted by the cathode are focused by one or more focusing electrodes kept in front of the cathode.
With the neat sketch, explain working principle of a two – hole directional coupler. Derive the scattering matrix of magic Tee. A multi hole directional coupler is fed withgle power of 2.8 mW at 10 GHz. The coupling factor is 3 dB and the directivity is better than 40 dB over X-band range. Find the distribution of power at all other ports.
The ideal two holes coupler is depicted in Fig. 5. It consists of two guides the main and the auxiliary with two tiny holes between them as shown in Fig. 5. The two holes are separated from each other by the distance
What is IMPATT diode? How does the negative resistance arise in this diode?
It is possible to make a microwave diode exhibit negative resistance by having a delaytween voltage and current in an avalanche together with transit time through the material. The IMPATT diode is stand for Impact Ionization Avalanche Transit Time Device.
What is Gunn diode oscillator? What are different modes of operation of Gunn diode? Mention its applications.
A Gunn diode oscillator circuit consists of a resonant cavity. An arrangement for coupling diode to the cavity, a circuit for biasing the diode and a mechanism to couple the R.F power the diode and a mechanism to couple the R.F power from the cavity to the external circuit or load.
What is E-plane Tee? Derive its S-matrix.
E-plane tee is a three port network. Here the auxiliary or side arm axis is parallel t the plane of the electric field of the main guide and hence this tee is known as E –plane Tee.
What are the difference between TED’s and junction device?
The difference between TEDs and Transistor as a junction device are as follows: Transistors operates with either junctions or gates while TEDs are bulk devices having no junction or gates
Explain Read diode. Give the electric field distribution, doping profile, voltage and current characteristics of read diode.
Read diode is nothing but the INPATT diode. The IMPATT diode is a convenient structure for a theoretical analysis and physical understanding but due to complicated nature IMPATT structure the prediction could not be immediately verified experimentally.
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