Topic name – resonant and non resonant antennas.pptx

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1. What is Resonant antenna- A resonant antenna is one that is designed to operate efficiently at a specific frequency or a set of closely spaced frequencies. The length of a resonant antenna is in exact multiples of λ /2. These antennas are open at both ends. They are used at a fixed frequency.

2. Radian pattern at Different length Maximum Radiation Half Wave λ/2 (b)Full Wave λ (c)Three Half Wave 3 λ /2 (d)Four Half Wave

3. Efficiency- - Resonant antennas are often highly efficient because they are designed to match the impedance of the transmission line(usually 50ohms)to the impedance of the antenna at the resonant frequency. Examples- Half –wave dipole Yagi- Uda antenna Quarter –wave monopole

4. What is non resonant antenna - Non Resonant antennas,also known as wideband or frequency- independed antennas do not rely on a specific resonance point for efficient operation.Instead they are designed to perform consistently over a broad range of frequencies. The length of a resonant antenna is in other than multiples of λ /2. In these antennas one end is excited and the other end is terminated. Non resonant antennas are known as periodic antennas .

5. Efficiency- -Non resonant antennas may be not be as efficient as resonant antennas at any specific frequency within their bandwidth. Example- log-periodic antennas Discone antennas, Broadband dipole antennas

6. Comparison - Resonant Antenna Length is multiple of λ /2 Both end are open Standing wave is present Directivity is Bi-directional Efficiency is high Non Resonant Antenna Not multiple of λ /2 One end is excited Not present Uni -directional Efficiency is low

7. Thank you