537 questions and answers
Why Schottky diodes are suitable for microwave region?
It is a simple metal semiconductor interface exhibiting non – linear impedance and is basically an extension of the point contact diode. When the diodes are forward biased current follows because of majority carrier from semiconductor into the metal.
Determine the spacing between 2 – holes in a 2 –hole directional coupler made in rectangular waveguide version with inner dimension of 2.286 cm X 1.00 cm at 9 GHz.
Given that b=1 cm, a=2.286 cm and f=9 GHz We know that
Define microwave. What is the significance of using ‘S’ parameter in microwave engineering.
Microwaves are a form of electromagnetic radiation with wavelength ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz (0.3 GHz) and 300 GHz.
Explain how high value of VSWR can be measured by the double minimum method.
Measurement of VSWR gives the degree of mismatch between the load and the transmission line. Complex load shifts the face and hence minimum position, so load impedance can be calculated from the VSWR and the position of the minimum point on the line with respect to the load.
Describe the operation of an ideal four port ‘directional coupler’. Define ‘Coupling’ and ‘Directivity’ in the context of a directional coupler.
The directional coupler consists of two transmission lines or waveguides coupled together by fringing fields, or in case of a waveguide, by means of a small slot in such a manner that an incident wave on one line is partly transferred to the other with particular directional properties.
What is scattering Parameters? Why is it used in microwave Network?
Any two port networks are represented by a special type of parameter by which reflection co- efficient or transmission co – efficient of any network is measured. This special type of parameter is called scattering parameter of S - parameter.
What are cross field device? What role does the dc magnetic field play in their normal operation?
The cavity magnetron is a cross field device. Here the electric field between anode and cathode is radial whereas the magnetic field produced by a permanent magnet is axial. The permanent magnet is placed such that the magnetic lines are parallel to the vertical cathode and perpendicular to the electric field between cathode and anode.
Explain PIN diode and give its application.
The p-i-n diode is a stack of a very highly doped p+- layer, and nearly intrinsic layer i and a very highly doped n+ layer. The variable element is resistances are Ri, that is related to the i- layer thickness.
Explain the tunneling action in a tunnel diode.
Tunnel diode is specially made p-n junction device which exhibits negative resistance over part of the forward bias characteristics. It has extremely heaving doping on both sides of the junction and an abrupt transition from the p – side to the n- side.
What is bunching? Explain with proper diagram. Deduce the expression for the minimum length at which the first bunch will be formed.
Electrons in the electron beam produced in the cathode – anode region of the Klystron and accelerated by a d.c anode voltage passing through a pair of buncher grids, across which an R.F voltage exist are either accelerated or decelerated depending on the part of the cycle during which they cross the gap.
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