Hanyang University ANTENNA THEORY ANALYSIS AND DESIGN Chapter

Hanyang University ANTENNA THEORY ANALYSIS AND DESIGN Chapter. 2 Problem Sungjoon YOON 2015. 07. 09 1/14

Hanyang University Problems 2. Fundamental Parameters Of Antennas 2. 7 Parameters 2. 34 Polarization 2. 67 Maximum Effective Area 2/14 Antennas & RF Devices Lab.

Hanyang University 2. 7. The power radiated by a lossless antenna is 10 watts. The directional characteristics of the antenna are represented by the radiation intensity of (watts/unit solid angle) (a) maximum power density (in watts/square meter) at a distance of 1, 000 m (assume far-field distance). Specify the angle where this occurs. (b) exact and approximate beam solid angle . (c) directivity, exact and approximate, of the antenna (dimensionless and in d. B). (d) Gain of the antenna (dimensionless and in d. B). 3/14

Hanyang University (a) maximum power density (in watts/square meter) at a distance of 1, 000 m (assume far-field distance). Specify the angle where this occurs. 4/14

Hanyang University (b) 1. exact beam solid angle 2. approximate beam solid angle = half-power beamwidth in one plane (rad) = half-power beamwidth in a plane at a right angle to the other (rad) 5/14

Hanyang University (c) directivity, exact and approximate, of the antenna (dimensionless and in d. B) 1. exact 2. approximate (d) gain 6/14

Hanyang University 7/14

Hanyang University 2. 34. A 300 MHz uniform plane wave, traveling along the x-axis in the negative x direction, whose electric field is given by where is a real constant, impinges upon a dipole antenna that is placed at the origin and whose electric field radiated toward the x-axis in the positive x direction is given by (a) Polarization of the incident wave (including axial ratio and sense of rotation, if any). You must justify (state why? ). (b) Polarization of the antenna (including axial ratio and sense of rotation, if any). You must justify (state why? ). (c) Polarization loss factor (dimensionless and in d. B). 8/14

Hanyang University 2. 34. elliptical polarization linear polarization 9/14

Hanyang University Polarization loss factor(PLF) • unit vector 10/14

Hanyang University 2. 67. An antenna has a maximum effective aperture of 2. 147 at its operating frequency of 100 MHz. It has no conduction or dielectric losses. The input impedance of the antenna itself is 75 ohms, and it is connected to a 50 -ohm transmission line. Find the directivity of the antenna system (“system” meaning includes any effects of connection to the transmission line). Assume no Polarization losses. the maximum effective area of an isotropic source is equal to the ratio of the maximum effective area to the maximum directivity of any other source 11/14

Hanyang University 2. 16 Maximum Directivity And Maximum Effective Area The relationship between directivity and maximum effective area directive properties Figure 2. 30 Two antennas separated by a distance R The power transferred to the load If antenna 2 is used as a transmitter, 1 as a receiver maximum effective areas (directivities) If antenna 1 is isotropic, then = 1 the maximum effective area of an isotropic source is equal to the ratio of the maximum effective area to the maximum directivity of any other source 12/14

Hanyang University If losses are included, then the maximum effective area The input impedance of the antenna itself is 75 ohms, and it is connected to a 50 -ohm transmission line 13/14

Hanyang University Thank you for your attention 14/14 Antennas & RF Devices Lab.