37 questions and answers
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.
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.
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