engineering
KATHMANDU UNIVERSITY
SCHOOL OF ENGINEERING
Department of Electrical & Electronics Engineering
LAB REPORT- III
Reciprocity Theorem of Antenna (Tx and Rx pattern is same)
By:
Sudip Shrestha (41020)
To:
Manya Gautam
Nov 21, 2010
Theory:
1. Reciprocity theorem:
Many antenna properties are the same for both transmitting and receiving. It is often easier to calculate the gain of a transmitting antenna than the collecting area of a receiving antenna, and it is often easier to measure the receiving power pattern than to measure the transmitting power pattern of a large radio telescope. Thus this receiving/transmitting "reciprocity" greatly simplifies antenna calculations and measurements. Reciprocity can be understood via Maxwell's equations or by thermodynamic arguments. The Rayleigh-Helmholtz reciprocity theorem has been generalized by Carson to include continuous media. This theorem as applied to antennas may be stated as follows:
“If an emf applied to the terminal of the antenna A and the current measured at the terminal of antenna B, then an equal current (in both amplitude and phase) will be obtained at the terminals of antenna A if the same emf is applied to the terminals of antenna B.” Figure1: reciprocity theorem of antenna
The strong reciprocity theorem implies that the transmitter voltages VA and VB are related to the receiver currents IA and IB by V_A/I_B =V_B/I_A for any pair of antennas A and B.
It is assumed that the emfs are of the same frequency and that the media are linear, passive and also isotropic. An important consequence of this theorem is the fact that under these conditions the transmitting and receiving patterns of an antenna are the same. Also, for matched impedances, the power flow is the same either way.
For most radio astronomical applications, we are not concerned with the detailed phase relationships of voltages and currents, and we can use a weak reciprocity
SCHOOL OF ENGINEERING
Department of Electrical & Electronics Engineering
LAB REPORT- III
Reciprocity Theorem of Antenna (Tx and Rx pattern is same)
By:
Sudip Shrestha (41020)
To:
Manya Gautam
Nov 21, 2010
Theory:
1. Reciprocity theorem:
Many antenna properties are the same for both transmitting and receiving. It is often easier to calculate the gain of a transmitting antenna than the collecting area of a receiving antenna, and it is often easier to measure the receiving power pattern than to measure the transmitting power pattern of a large radio telescope. Thus this receiving/transmitting "reciprocity" greatly simplifies antenna calculations and measurements. Reciprocity can be understood via Maxwell's equations or by thermodynamic arguments. The Rayleigh-Helmholtz reciprocity theorem has been generalized by Carson to include continuous media. This theorem as applied to antennas may be stated as follows:
“If an emf applied to the terminal of the antenna A and the current measured at the terminal of antenna B, then an equal current (in both amplitude and phase) will be obtained at the terminals of antenna A if the same emf is applied to the terminals of antenna B.” Figure1: reciprocity theorem of antenna
The strong reciprocity theorem implies that the transmitter voltages VA and VB are related to the receiver currents IA and IB by V_A/I_B =V_B/I_A for any pair of antennas A and B.
It is assumed that the emfs are of the same frequency and that the media are linear, passive and also isotropic. An important consequence of this theorem is the fact that under these conditions the transmitting and receiving patterns of an antenna are the same. Also, for matched impedances, the power flow is the same either way.
For most radio astronomical applications, we are not concerned with the detailed phase relationships of voltages and currents, and we can use a weak reciprocity