Ultra-wideband (UWB) antennas must transmit very short pulse signals accurately and efficiently. The document discusses various types of UWB antennas including traveling-wave antennas like horn antennas, frequency-independent antennas whose radiation patterns do not change with frequency, self-complementary antennas with constant input impedance regardless of frequency or shape, multiple resonance antennas made of multiple narrowband elements, and electrically small antennas. Key antenna characterization parameters in time and frequency domains are also presented.

1. Ultra Wide-Band Antenna
Prepared By:
Krunal Siddhapathak(10BEC097)

2. Outline

3. Introduction
 Ultra-wideband (UWB) communication systems
have the promise of very high bandwidth
 reduced fading from multipath
 low power requirements.
 The main concept behind UWB radio systems is
that they transmit pulses of very short duration, as
opposed to traditional communication schemes,
which send sinusoidal waves
 The role that UWB antennas play in all of this is
that they have to be able to transmit these pulses
as accurately and efficiently as possible.

4. Introduction (Contd.)

5. UWB Frequency-Domain Signal
Link Characterization
 The transmit antenna is excited with a continuous wave signal
with the frequency f .
 The relevant parameters for the frequency-domain link
description are:
 AMPLITUDE OF TRANSMITTED SIGNALUTX(F) IN [V];
 amplitude of receive signal Urx(f) in [V];
 radiated field strength at a position r ETX.
 transfer function of the transmit antenna.
 transfer function of the received antenna.
 characteristic transmit antenna impedance.
 characteristic receive antenna impedance.
 Antenna gain.
 Distance between Tx-Rx antenna.

6.  the transmit antenna is excited with a impulse.
 The elements of the UWB time domain link
characterization are:
 AMPLITUDE OF TRANSMIT SIGNAL UTX(F) IN [V];
 amplitude of receive signal Urx(f) in [V];
 radiated field strength at a position r ETX.
 transfer function of the transmit antenna.
 transfer function of the received antenna.
 characteristic transmit antenna impedance.
 Distance between Tx-Rx antenna.
UWB Time-Domain Signal Link
Characterization

7. Antenna Characterization
Parameter
1) Peak Value of the
Envelope: The peak value
of the analytic envelope
h+(t) is a measure for the
maximal value of the
strongest peak of the
antenna’s time-domain
transient response envelope.
2) Gain in Frequency
Domain: The gain in
frequency domain is defined
like in narrow-band systems.

8. Antenna Characterization
Parameter (Contd.)
3)Envelope Width: The envelope width describes the
broadening of the radiated impulse and is defined as the width
of the magnitude of the analytic envelope at half maximum
(FWHM).
4) Ringing: The ringing Tt of a UWB antenna is undesired and
usually caused by resonances due to energy storage or multiple
reflections in the antenna. It results in oscillations of the
radiated pulse after the main peak.
5) Transient Gain: The transient gain gT is an integral quality
measure that characterizes the ability of an antenna to radiate
the power of a given waveform uTx
6) Group Delay: The group delay of an antenna characterizes
the frequency dependence of the time delay.

9. UWB ANTENNA PRINCIPLES
The ultra-wide bandwidth radiation is based
on a few principles:
1. traveling-wave structures
2. frequency-independent antennas
3. self-complementary antennas
4. multiple resonance antenna
5. electrically small antennas.

10. Traveling-Wave Antennas
 Traveling-wave antennas
offer for the guided wave
a smooth, almost not
recognizable transition
with the fields
accelerated to free-space
propagation speed co
 Typical antennas are
tapered wave guide
antenna e.g horn antenna
,Vivaldi antennas Aperture coupled Vivaldi
antenna. (Left) Top view;
(right)bottom view with feed
line.

11. Frequency-Independent Antennas
 If wavelength and size of
antenna is scaled by same
factor than radiation pattern
will remain same this type
of antenna are called
frequency independent.

12. Self-Complementary Antennas
 It is an arbitrary shaped
antenna
 Antenna constitute half of
an infinitely extended
planar-sheet conductor such
that the shape of its
complementary structure is
exactly identical with that
of the original
structure with two terminals
for the simplest case.
 The self-complementary
antenna has constant input
impedance independent of
the source frequency and
the shape of the structure.
Truncated fractal antenna to
show the principle of self-
complementary antennas.

13. Self-Complementary Antennas
(Contd.)
 Type of self complementary antenna depends on numbers of
terminal, number of reference plane and others
 They also have constant-impedance property independent of
the source frequency and the shape of the structure for
respective classes of structures with various grades of
complexity. This general principle is called “Principle of Self-
Complementarity”. (This is also called “Mushiake Principle”
on the Internet.) This principle is applicable also to the
structures other than antennas

14. Multiple Resonance antenna
 Multiple resonance antennas
are combinations of
multiple, narrow-band,
radiating elements.
 Each element for example, a
dipole covers a limited
bandwidth, e.g., 20% of the
total UWB bandwidth.
Typical candidates are the
Log-Per and fractal
antennas.
Log-Per antenna with a coaxial
connector feeding the inner triplate
line.

15. Electrically Small Antennas


16. Conclusion
 Ultra-wide-band as an emerging technology requires for the
antenna characterization a thorough knowledge of the
behaviour in time domain, in frequency domain, and, in
certain cases, in the spatial domain. It has been shown that for
ultra-wide-band, certain antenna classes can be defined
according to their radiating characteristics.