Rcs measurement calibration of an anechoic chamber and rcs

International Journal of Electronics and Communication Engineering & Technology (IJECET),
INTERNATIONAL JOURNAL OF ELECTRONICS AND
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME

COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)

ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Special Issue (November, 2013), pp. 103-109
© IAEME: www.iaeme.com/ijecet.asp
Journal Impact Factor (2013): 5.8896 (Calculated by GISI)
www.jifactor.com

IJECET
©IAEME

RCS Measurement: Calibration of an Anechoic Chamber and RCS
Measures of Specific Targets
Neha Rohilla1, Ishani Khanna2, Supreet Kaur Sidhu3
Electronics & Communication Engineering, BKBIET, Pilani, Rajasthan, India
1neharohilla4@gmail.com, 2ishanikhanna@gmail.com, 3supreetkaursidhu28@gmail.com

ABSTRACT: In the following paper, we intend to take the RCS measurements of various objects
like plate, sphere, dihedral and reflect array dihedral and get the calibration coefficient of the
anechoic chamber.
Here we work on an apparatus that consists of following:


Vector network analyzer (VNA)- ROHDE & SCHWARZ, ZVB-14 (10 MHz- 14GHz)



Anechoic chamber with a turntable.



Transmitting and Receiving antennas (A duplexer that serves as a switch between the
antenna and the transmitter or the receiver for the signal when the antenna is used in
both situations.)



Lab view software.



MATLAB software.

Various objects i.e. Sphere of different diameters, plates with different dimensions, dihedral
and reflect array dihedral with different angle.

KEYWORDS: RCS-radar cross section
I.

INTRODUCTION

A. Anechoic chamber
An anechoic chamber (an-echoic or non-echoing) is a room designed to stop reflections of
either sound or electromagnetic waves. The size of the chamber depends on the size of the
objects to be tested and the frequency range of the signals used, although scale models can
sometimes be used by testing at shorter wavelengths. An anechoic chamber is a room, where
International Conference on Communication Systems (ICCS-2013)
B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India

October 18-20, 2013
Page 103


the target is placed on a rotating pillar in the center, and the walls, floors and ceiling are
covered by stacks of radar absorbing material. These absorbers prevent corruption of the
measurement due to reflections. A compact range is an anechoic chamber with a reflector to
simulate far field conditions.
B. Radar
Radar is an object detection system which uses radio waves to determine the range, altitude,
direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided
missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits
pulses of radio waves or microwaves which bounce off any object in their path.
The object returns a tiny part of the wave's energy to a dish or antenna which is usually located
at the same site as the transmitter. RADAR gained importance during World War II. The term
RADAR is basically an acronym for Radio Detection And Ranging.
A radar system has a transmitter that emits radio waves called radar signals in predetermined
directions. When these come into contact with an object they are usually reflected or scattered
in many directions. Radar signals are reflected especially well by materials of considerable
electrical conductivity—especially by most metals, by seawater, by wet land. Some of these
make the use of radar altimeters possible. The radar signals that are reflected back towards the
transmitter are the desirable ones that make radar work. If the object is moving either toward
or away from the transmitter, there is a slight equivalent change in the frequency of the radio
waves, caused by the Doppler Effect.
Radar receivers are usually, but not always, in the same location as the transmitter. Although
the reflected radar signals captured by the receiving antenna are usually very weak, they can
be strengthened by electronic amplifiers. More sophisticated methods of signal processing are
also used in order to recover useful radar signals.
The weak absorption of radio waves by the medium through which it passes is what enables
radar sets to detect objects at relatively long ranges—ranges at which other electromagnetic
wavelengths, such as visible light, infrared light, and ultraviolet light, are too strongly
attenuated. Such weather phenomena as fog, clouds, rain, falling snow, and sleet that block
visible light are usually transparent to radio waves. Certain radio frequencies that are
absorbed or scattered by water vapor, raindrops, or atmospheric gases (especially oxygen) are
avoided in designing radars, except when their detection is intended.
C. Radar cross section (RCS)
Radar cross section (RCS) is a measure of how detectable an object is with radar. A larger RCS
indicates that an object is more easily detected.
An object reflects a limited amount of radar energy. A number of different factors determine
how much electromagnetic energy returns to the source such as:


material of which the target is made;



absolute size of the target;


October 18-20, 2013
Page 104




relative size of the target (in relation to the wavelength of the illuminating radar);



the incident angle (angle at which the radar beam hits a particular portion of target which
depends upon shape of target and its orientation to the radar source);



reflected angle (angle at which the reflected beam leaves the part of the target hit, it
depends upon incident angle);



the polarization of transmitted and the received radiation in respect to the orientation of
the target

While important in detecting targets, strength of emitter and distance are not factors that affect
the calculation of a RCS because the RCS is a property of the target reflectivity.

II.

OBSERVATIONS

A. Plate (0.0999*0.1845)

Fig. 1: Frequency vs RCS using VNA

Fig. 2: Frequency vs RCS using lab view software

Fig. 3: Theta vs RCS using lab view software

October 18-20, 2013
Page 105


Blue line – measurement
Green line – theoretical graph
Calibration coefficient at 9GHz = -30.906
Theta Range = -30 to 30
Delta Theta = 0.5
B. Plate (0.115*0.106) m




October 18-20, 2013
Page 106


C. Reflect array dihedral –a


D. Sphere Diameter = 88.3 mm



October 18-20, 2013
Page 107


III.

COMPARISON BETWEEN H-H(HORIZONTAL) AND V-V(VERTICAL) POLARIZATION
Blue- VV polarization

Green-HH polarization

Fig. 11: PLATE (0.1845*0.0999) m

Fig. 12: Dihedral

IV.

RESULT

1. Here we observe that the calibration coefficient calculated by VNA and Lab view software is
different.
2. The graphs obtained for H-H and V-V polarization is almost the same besides the depth of
lobes.
3. Calibration coefficient obtained through Lab view software for sphere and plates of different
dimensions are different.

V.

CONCLUSION

1. Here we observe that the calibration coefficient calculated by VNA and Lab view software is
different.
2. The graphs obtained for H-H and V-V polarization is almost the same besides the depth of
lobes.
3. Calibration coefficient obtained through Lab view software for sphere and plates of different
dimensions are different.

REFERENCES
[1] Inverse synthetic aperture Radar imaging with MATLAB algorithms, First edition
[2] Chapter 1: Basics of Fourier analysis
[3] Chapter 2: Radar fundamentals

October 18-20, 2013
Page 108


BIOGRAPHY
ISHANI KHANNA was born in Delhi, India in 1992. She is pursuing B.tech in
electronics and communication from B K Birla institute of engineering and
technology, Pilani, Rajasthan. Did internship from IETR Lab, INSA, RENNES,
FRANCE.

SUPREET KAUR SIDHU was born in Bathinda, Punjab, India in 1992. She is
pursuing B.tech in electronics and communication from B K Birla institute of
engineering and technology, Pilani, Rajasthan. Did internship from IETR lab,
INSA, RENNES, FRANCE.

NEHA ROHILLA was born in Ratangarh, Rajasthan, India in 1992. She is
pursuing B.tech in electronics and communication from B K Birla institute of
engineering and technology, Pilani, Rajasthan. Did internship from IETR lab,
INSA, RENNES, FRANCE.


October 18-20, 2013
Page 109

Rcs measurement calibration of an anechoic chamber and rcs

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (8)

En vedette

En vedette (13)

Similaire à Rcs measurement calibration of an anechoic chamber and rcs

Similaire à Rcs measurement calibration of an anechoic chamber and rcs (20)

Plus de IAEME Publication

Plus de IAEME Publication (20)

Dernier

Dernier (20)

Rcs measurement calibration of an anechoic chamber and rcs