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Procedure for radiation pattern measurement in Antenna
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Measurement of Reflection and Radiation
Characteristics of Antenna
Department of Electrical Engineering,
IIT Kanpur
Kushmanda Saurav and Debdeep Sarkar
What is an Antenna?
A means for radiating or receiving radio waves (IEEE Standard Definitions of Terms for Antennas)
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=30651
1. Antenna acts as a transitional
structure between free-space and a
guiding device
2. Antenna optimizes or accentuate the
radiation energy in some directions and
suppress it in others. Thus the antenna
must also serve as a directional
device in addition to a probing device.
Single Antenna Configurations
Dipole Antenna Loop Antenna
Pyramidal Horn Antenna Microstrip Patch Antenna
Antenna Array Configurations
Yagi Uda Array Array of Microstrip Patch Antenna
Slotted Waveguide Array
Main Performance Metrics of any
Antenna
Return Loss Input Reflection Coefficient (S11)
Radiation Pattern
Directivity / Gain
Radiation Efficiency
Polarization characteristics: Linear / Circular
S11 measurement using Vector Network
Analyzer
Approximate reflection characteristics of antenna in the entire operating range of VNA
Preset the VNA Connect the antenna under test to the port 1 of VNA Measure the S11
Once the desired operating frequency range is known
Perform the one port calibration of the VNA in the desired frequency range
Connect the antenna under test to the port 1 of VNA Measure the S11
Radiation Pattern of Antenna
Defined as mathematical function or a graphical representation of the radiation properties of the antenna as a function of space
coordinates.
Radiation Properties include
Power density, Radiation intensity, Field strength, Directivity.
Radiation pattern is generally determined in far-field of antenna
Challenge: Automatic Measurement of Radiation Pattern.
PC loaded with LabVIEW 2010.
Antenna under test (AUT) and reference antenna.
Vector Network Analyzer (HP 8712ET).
Position Controller (HOLMARC ver 2.0)
Turn table
Radiation pattern measurement set-up (transmitting and probe antenna, cables, connectors etc.)
Automatic Radiation Pattern measurement setup
Linearly Polarized Printed Dipole Antenna
acting as AUT
Dipole
Balun
Theoretical Radiation Pattern of the AUT
Radiation pattern measurement setup in
anechoic chamber
Position Controller
Antenna stand mounted on the turn table
Position controller
Control through GPIB Control through RS232
Radio Frequency
Vector Network Analyzer
Acknowledgement
S. Vinoth Naidu
PhD Student
EE Department, IIT Kanpur
Position controller
Position controller
Position controller
Position controller
orot
t
r GGRP
P2
4
Pt = Input power of transmitting antenna
Pr = Power delivered to the receiving antenna
R = Distance between transmitting and receiving antenna
Got = Gain of transmitting antenna
Gor = Gain of receiving antenna
= Free space loss factor
corresponds to the operating wavelength
(Far-field region of antenna)
2
4
R
22DR
Friis transmission equation
Pt Got
Pr Gor
R
t
r
P
PS 21
If we make use of VNA
for antenna radiation
characteristics
measurement
Gain measurement
Absolute method: A pair of identical test antennas are required
Identical test antennas are used as transmitters and receivers
Thus,
And
Relative method: Standard gain antenna with known value of gain in the desired
frequency range is required
orot
t
r GGRP
P2
4
orot GG
RP
PG
t
rot
4/
or
t
rot G
RP
PG
2
4/
Pt Got
Pr Gor
R
6 April, 2015 Metamaterial Antenna: Demo