Traveling Wave Antenna

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1. Traveling Wave Antenna Antenna Theory Prepared by Abdelaziz Said Electrical Engineering Department New Cairo Academy

2. - Traveling wave antenna is non-resonant type antenna or aperiodic antenna Definitions - The antenna in which the standing wave does not exist along the length of the antenna is called traveling wave antenna

3. Q1 What is the difference between standing wave and traveling wave ? Q2 What is the difference between resonant and non-resonant antenna ?

4. 1- Long Wire Antenna An antenna is usually classified as a long wire antenna if it is a very straight conductor with a length from one to many wavelengths Antenna Height (h)

5. Total field radiated by the wire It is found by multiplying the field radiated by the wire in free space by the array factor of a two-element array the wave travels along the wire from the source toward the load, it continuously leaks energy (attenuation coefficient) Field radiated in free space Radiated by long wire to free space

6. Current distribution along structure I f = aˆ z I z (z ΄ ) = z I By approx. : I f = aˆ z I z (z ΄ ) = z I K = =  

7. it is evident that the power distribution of a wire antenna of length l is a multi lobe pattern whose number of lobes depends upon its length. To calculate Peaks of lopes

8. For angles the peaks occur To find nulls Angles where the nulls occurs

9. Total radiated power Radiation resistance Directivity

10. Design long wires Amplitude pattern , maxima and nulls

11. Input Impedance

12. Advantages Provides strong Minor Lobes Disadvantages Easy to Construct More Cheap than V antenna More simple Larger Bandwidth Input impedance is High

13. Applications Commercial applications Mellatry applications For RF communications Microwave communications Long Closed places likes tunnels

14. 2 - V Antenna The V antenna is made up of two wire antenna which are arranged in the form of the horizontal V and it is fed at the apex by the transmission feed line. For some applications a single long-wire antenna is not very practical because (1) its directivity may be low. (2) its side lobes may be high. These and other drawbacks of single long-wire antennas can be overcome by utilizing an array of wires, One very practical array of long wires is the V

15. There are two Types: Resonant V antenna Non-Resonant V antenna

16. Most V antennas are symmetrical (θ1 =θ2 =θ0 and l1 =l2 =l). Also V antennas can be designed to have unidirectional or bidirectional radiation patterns, as shown in Figures

17. Easy to Construct Cheap Disadvantages Advantages Provides strong Minor Lobes Applications On Light Aircraft Military appliances Commercial appliances

18. 3- Rhombic Antenna Two V antennas can be connected at their open ends to form a diamond or rhombic antenna, The antenna is usually terminated at one end in a resistor, usually about 600–800 ohms, in order to reduce if not eliminate reflections

19. - Radiation Pattern Unidirectional Pattern Lobes = 2 to 8 long Directivity : 20 to 90 Power Gain : 50 to 60 β value = 17 to 24 degree

20. Assignment  - Design of Rhombic antenna

21. The tilt angle ( ) The leg length (L) The height above the ground (h) Two designs ( a) Alignment design ( b) Maximum output design - Design of Rhombic antenna

22. (a) Alignment design h is chosen that max of the main lobe coincides with the desired angle of elevation 

23. (b) Maximum field intensity design h is chosen that max filed intensity is obtained at the desired elevation angle 

24. Highly directional Simple & cheap Disadvantages Advantages Needs larger space for installation Efficiency is Low Applications HF transmission & reception

25. Thank you…