Antenna & Wave Propagation – Engineer's Stuff

Microwave Transistor in Hindi

Microwave transistor ek non-liner device hai. iske opration ka principle low frequency device ke saman hai lekin iska dimension, process control, heat sinking and packaging alag hoti hai. aadharsh roop se, high geometry and packaging wala transistor use krne se interalectrod capisitor and load idectance ka effect kam padta hai. iron mobolity, bias voltage, emmitter delay time, base transient time , collector transient time and microwave ke ese parameter hai jinko control krke inki performance ko better create kiya ja shakta hai.

Silcon N-P-N transistor, microwave frequency par addictive power supply karata hai. 5dB ke gain ke saath 3Ghz frequency par yeh 5W ki power ko devlop krta hai.

eventually yeh double diffuse epithelcial device hai.

Introduction of Antenna in Hindi

Antenna transducers hote hai. Yeh same frequency pr radio frequency electric current ko electromegnetic (EM) wave mein change kr deta hai. in dono wave ki frequency same hoti hai. Antenna ko ariel bhi kehte hai. Antenna, Conducting Material ka piece hota hai jo wire, rod or radiator hota hai. yeh electromagetic wave ke liye sensors ki taraf kaam krta hai.

Basic Elements of Antenna –

(i) Alternative Current Elements (ii) Short Dipole (iii) Short Monopole (iv) Half Wave Dipole (v) Quater Wave Dipole

z – Transform

The z-transform is a very powerful tool for the analysis of discrete time signals and LTI systems. The z-transform of a discrete-time signal x(n) is defined as the power series

Z[x(n)] = X(z) = SIGMA x(n)z(power)-n …..(i)

where z is a complex variable. This expression is generally referred to as two-sided z-transform.

If x(n) is a causal sequence, x(n) = 0 for n<0, then its z-transform is

X(z) = SIGMA x(n)z(power)-n

This expression is also called a one-sided z-transform.

The equation (i) is sometimes called the direct z-transform because it transform the time-domain signal x(n) into its complex plalne representation X(z).

There are following uses of z-transform as given below —

(i) Stability of discrete time LTI system.

(ii) Causality of discrete time LTI system.

(iii) System behaviour related to the system function of a discrete time LTI system.

Electromagnetic Radiation

Maxwell’s equations predict the radiation of electromagnetic energy from current sources under time varying conditions. Althrough such phenomenon occurs at all frequencies, its relative magnitude is insignificant until the size of the source region is comparable to wavelength. Our main interest is in the radiation of this electromagnetic wave or loss of energy from the system into free space. While transmission lines or waveguides are generally made so as to minimize radiation, antennas are designed to radiate energy as effectively as possible.

The transmitting antennas are devices used in terminating a transmission line or waveguide with the intent of efficiently launching electromagnetic waves into free space and hence they can be considered as source of such waves in space. The radiation of electromagnetic waves from a transmitting antenna to a receiving antenna is of considerable interest. Thus, we are concerned with the analysis of the radiation fields achieved from typical antenna source depicted.

When RF energy is fed into a mismatched transmission line, standing waves take place, Energy is lost or radiated into the space surrounding the line. This process is considered undesired in the transfer of energy to the radiation device. If we examine this process and expand upon it, by separating the ends of the transmission line, that more surface area of the wire is exposed to the atmosphere and enhances the radiation process.

Radiation efficiency of this system is improved even more when the two wires are bent at 90* (right angles) to each other. Now, the electric and magnetic fields are fully coupled to the surrounding space instead of being confiend between the two wire, and maximum radiation results. This type of radiator is known as a dipole. If the total length of the two wires is a falf wavelength, then antenna is called a half-wave dipole.