5 Results 26
5.1 Extraction of antenna properties              . 26
5.2 Angle of arrival estimation of NLOS path component        . 26
5.3 Channel information reconstruction             26
5.4 Impulse response reconstruction for Vivaldi vs. Biconical antenna Comparison 27
6 Conclusion 30
7 Acknowledgment 31
1 Introduction
State of the art channel models have been presented in [1]. However, these models repre-
sent channels for omnidirectional antennas and single input single output (SISO) channels
and seldom paper has been proposed to consider highly directional antenna patterns and
multiple input multiple output (MIMO) channels [2].
1.1 UWB history
Attention on Ultra Wide-Band wireless has increased greatly with the publication in Feb
2002 by the FCC of their first authorization for UWB [3], [4]. A number of synonymous terms
such as: impulse, carrier-free, baseband, time domain, nonsinusoidal, orthogonal function
and large-relative-bandwidth radio/radar signals have become more and more significant
due to the popular of the UWB currently. UWB is usually considered to be wireless commu-
nication or remote sensing using non-sinusoidal carriers, or sinusoidal carriers of only a few
cycles duration. Definition of an UWB device by FCC is a device whose emissions have a
fractional bandwidth more than 0.2 or occupy > 1.5GHz of spectrum [4].
The different between Ultra wideband and other communication techniques, mainly due
to Ultra wideband employs extremely narrow RF pulses to communicate between transmit-
ters and receivers. Utilizing short-duration pulses as the building blocks for communications
directly generates a very wide bandwidth and offers several advantages, such as large through-
put, covertness, robustness to jamming, and coexistence with current radio services.
Ultra-Wide-Band (UWB) actually has a long history. In the late 1800s, the pulse-based
Spark Gap radio which developed by Guglielmo Marconi was the first UWB radio by defi-
nition. This radio system was used for several decades to transmit Morse code through the
airwaves. By the early 1970s, the basic designs for UWB signal systems were available and
there remained no major impediment to progress in perfecting such systems. During 1977-
1989, the USAF had a program in UWB system development headed by Col. J.D. Taylor. By
1988 the Barrett organized a UWB workshop for the US Department of Defense’s DDR&E
which had over 100 participants. By 1994, Micro power Impulse Radar (MIR) has been in-
vented by T.E. McEwan at LLNL. This new MIR provided a UWB operating at ultralow power
for the first, as well as being extremely compact and inexpensive. This was the first UWB
radar to operate on only microwatts of battery drain. The FCC approved the First Report and
Order (R&O) for commercial use of UWB technology under strict power emission limits for
various devices in February 2002, due to the pressure caused by the increased interests in the
commercialization of UWB over past several years.
1.2 UWB antenna
UWB has many advantages to be utilized in Radio channel, especially in multipath prop-
agation environment. Due to the greater widewidth, UWB channel has a smaller the root
mean square (RMS) delay (about 40 ns) in time domain makes UWB channel models suitable
to tracing multiple components.
This thesis presents a highly directive UWB antenna exhibiting a bandwidth from3-20GHz,
dispersive properties less than 1 ns, antenna gain beyond 8 dBi, and a very small size. The
dispersive properties of the UWB antenna make it possible to separate single multipath com- 基于超宽带测量设备设计与实现的多路径AOA识别(2):http://www.751com.cn/tongxin/lunwen_5472.html