1. Basic ElectronicsPrepareed By: Patel Yash K. - 130420109537 Pawar Kumar S. - 130420109538 Rathod Kishan . -130420109539

2. Topics Transmission Lines Waveguides Antenna Fundamentals 3. Characteristics of andapplications ofTransmission lines Advantages: Less distortion, radiation (EMI), cross-talk Disadvantage More power required. Applications, transmission lines canhandle Signals traveling in long distance inPrinted-circuit-board PCB Signals in a cables, connectors (USB,PCI). 4. Advantage of usingtransmission lines:Reduce ElectromagneticInterference (EMI) inpoint-to-point wiring Wire-wrap connections create EMI. Transmission lines reduce EMIbecause, Current loop area is small, also itconstraints the return current (in groundplane) closer to the outgoing signal path,magnetic current cancel each other. 5. Differenttransmission lines1. Coaxial (unbalanced) line and2. Parallel-wire (balanced) line 6. Coaxial Cables 7. Coaxial Cable Labels 8. R=resistance; G=conductance;C=capacitance; L=inductance. All unit lengthvalues.DvR dx L dxvdx 9. Important result for agood coppertransmission line and w=constant Z0= [(R+j w L)/(G+j w C)]=characteristicimpedance If you have a good coppertransmission line R,G are small, and if the signal has a Constant frequency w therefore Z0=(L/C)1/2= a constant 10. WaveguidesIntroductionAt frequencies higher than 3 GHz, transmissionof electromagnetic energy along thetransmission lines and cables becomes difficult.This is due to the losses that occur both in thesolid dielectric needed to support the conductorand in the conductors themselves.A metallic tube can be used to transmitelectromagnetic wave at the above frequencies 11. DefinitionA Hollow metallic tubeof uniform crosssection fortransmittingelectromagneticwaves by successivereflections from theinner walls of the tubeis called waveguide. 12. Applications of circularwaveguide Rotating joints in radars to connect the hornantenna feeding a parabolic reflector (whichmust rotate for tracking) TE01 mode suitable for long distance waveguidetransmission above 10 GHz. Short and medium distance broad bandcommunication (could replace / share coaxialand microwave links) 13. Wave Guide Medium 14. Expression for cut offwavelengthFor a standard rectangular waveguide, the cutoffwavelength is given by,22 2n m + =bac lWhere a and b are measured in centimeters 15. Advantages Small size Reduced losses ascompared to atransmission line Operation at very high frequency is possible(upto 325 Ghz) They are simpler to manufacture. Large power handling capacity. 16. Disadvantages Low Frequency operation is not possible asthey become bulky at low frequency. Absolute efficiency is low. 17. Antennas Function of antennas Radiation Pattern of antenna Isotropic Radiator Efficiency Gain 18. AntennasTransmitting Antenna: Any structure designed toefficiently radiate electromagnetic radiation in apreferred direction is called a transmitting antenna.Wires passing an alternating current emit, orradiate, electromagnetic energy. The shape andsize of the current carrying structure determineshow much energy is radiated as well as thedirection of radiation.Receiving Antenna: Any structure designed toefficiently receive electromagnetic radiation is calleda transmitting antennaWe also know that an electromagnetic field will inducecurrent in a wire. The shape and size of the structuredetermines how efficiently the field is converted intocurrent, or put another way, determines how well theradiation is captured. The shape and size also determinesfrom which direction the radiation is preferentiallycaptured. 19. Antennas Radiation PatternsRadiation patterns usually indicate either electric field intensity or powerintensity. Magnetic field intensity has the same radiation pattern as theelectric field intensity, related by hoIt is customary to divide the field or power component by itsmaximum value and to plot a normalized functionNormalized radiation intensity:( ) ( , ,)maxn ,P rPPq fq f =Isotropic antenna: The antenna radiateselectromagnetic waves equally in all directions.( , ) 1 n iso P q f = 20. Antennas Radiation PatternsRadiation patterns usually indicate either electric field intensity or powerintensity. Magnetic field intensity has the same radiation pattern as theelectric field intensity, related by hoIt is customary to divide the field or power component by itsmaximum value and to plot a normalized functionNormalized radiation intensity:( ) ( , ,)maxn ,P rPPq fq f =Isotropic antenna: The antenna radiateselectromagnetic waves equally in all directions.( , ) 1 n iso P q f = 21. Antennas Radiation PatternsRadiation Pattern:A directional antenna radiates and receivespreferentially in some direction.A polar plotA rectangular plotIt is customary, then, to take slices of thepattern and generate two-dimensionalplots.The polar plot can also be in terms of decibels.( ) ( , ,)max, nE rEEq fq f =( , ) ( ) 20log[ ( , ) ] n n E q f dB = E q fIt is interesting to note that a normalizedelectric field pattern in dB will be identical to thepower pattern in dB.( , ) ( ) 10log[ ( , ) ] n n P q f dB = P q f 22. Antennas Radiation PatternsA polar plotA rectangular plotRadiation Pattern:It is clear in Figure that in some veryspecific directions there are zeros, or nulls,in the pattern indicating no radiation.The protuberances between the nulls arereferred to as lobes, and the main, ormajor, lobe is in the direction of maximumradiation.There are also side lobes and back lobes.These other lobes divert power away fromthe main beam and are desired as smallas possible.Beam Width:One measure of a beams directional nature isthe beamwidth, also called the half-powerbeamwidth or 3-dB beamwidth. 23. Antennas EfficiencyEfficiencyPower is fed to an antenna through a T-Line andthe antenna appears as a complex impedanceZant = Rant + jXant .where the antenna resistance consists ofradiation resistance and and a dissipativeresistance.ant rad dis R = R + RFor the antenna is driven by phasor current jThe power radiated by the antenna is The power dissipated by ohmic losses is2 12 rad o rad P = I R 2 12 diss o diss P = I RAn antenna efficiency e can be defined as the ratio of the radiatedpower to the total power fed to the antenna.P R= =rad radrad diss rad disseP + P R +Ro s I = I e a 24. Antennas GainGainThe power gain, G, of an antenna is very much like its directive gain, butalso takes into account efficiencyG(q ,f ) = eD(q ,f )The maximum power gainGmax = eDmaxThe maximum power gain is often expressed in dB.( ) ( ) max 10 max G dB = 10 log G 25. Types of Antennas1. Dipole antennas2. Horn antennas3. Parabolic antennas4. Yagi antennas