Abstract: In this paper, a planar antenna for UWB applications
has been proposed. The antenna consists of a square patch, a partial
ground plane and a slot on the ground plane. The proposed antenna is
easy to be integrated with microwave circuitry for low manufacturing
cost. The flat type antenna has a compact structure and the total size
is 14.5×14.5mm2. The result shows that the impedance bandwidth
(VSWR≤ 2) of the proposed antenna is 12.49 GHz (2.95 to 15.44
GHz), which is equivalent to 135.8%. Details of the proposed
compact planar UWB antenna design is presented and discussed.
Abstract: Ultra-wide band (UWB) communication is one of
the most promising technologies for high data rate wireless networks
for short range applications. This paper proposes a blind channel
estimation method namely IMM (Interactive Multiple Model) Based
Kalman algorithm for UWB OFDM systems. IMM based Kalman
filter is proposed to estimate frequency selective time varying
channel. In the proposed method, two Kalman filters are concurrently
estimate the channel parameters. The first Kalman filter namely
Static Model Filter (SMF) gives accurate result when the user is static
while the second Kalman filter namely the Dynamic Model Filter
(DMF) gives accurate result when the receiver is in moving state. The
static transition matrix in SMF is assumed as an Identity matrix
where as in DMF, it is computed using Yule-Walker equations. The
resultant filter estimate is computed as a weighted sum of individual
filter estimates. The proposed method is compared with other existing
channel estimation methods.
Abstract: The world of wireless telecommunications is rapidly evolving. Technologies under research and development promise to deliver more services to more users in less time. This paper presents the emerging technologies helping wireless systems grow from where we are today into our visions of the future. This paper will cover the applications and characteristics of emerging wireless technologies: Wireless Local Area Networks (WiFi-802.11n), Wireless Personal Area Networks (ZigBee) and Wireless Metropolitan Area Networks (WiMAX). The purpose of this paper is to explain the impending 802.11n standard and how it will enable WLANs to support emerging media-rich applications. The paper will also detail how 802.11n compares with existing WLAN standards and offer strategies for users considering higher-bandwidth alternatives. The emerging IEEE 802.15.4 (ZigBee) standard aims to provide low data rate wireless communications with high-precision ranging and localization, by employing UWB technologies for a low-power and low cost solution. WiMAX (Worldwide Interoperability for Microwave Access) is a standard for wireless data transmission covering a range similar to cellular phone towers. With high performance in both distance and throughput, WiMAX technology could be a boon to current Internet providers seeking to become the leader of next generation wireless Internet access. This paper also explores how these emerging technologies differ from one another.
Abstract: A modified Saleh-Valenzuela channel model has been
adapted for Ultra Wideband (UWB) system. The suggested realistic
channel is assessed by its distribution of fading amplitude and time of
arrivals. Furthermore, the propagation characteristic has been distinct
into four channel models, namely CM 1 to 4. Each are differentiate in
terms of cluster arrival rates, rays arrival rate within each cluster and
its respective constant decay rates. This paper described the
multiband OFDM system performance simulates under these
multipath conditions. Simulation work described in this paper is
based on WiMedia ECMA-368 standard, which has been deployed
for practical implementation of low cost and low power UWB
devices.
Abstract: In diversity rich environments, such as in Ultra-
Wideband (UWB) applications, the a priori determination of the
number of strong diversity branches is difficult, because of the considerably large number of diversity paths, which are characterized
by a variety of power delay profiles (PDPs). Several
Rake implementations have been proposed in the past, in order to reduce the number of the estimated and combined paths. To this
aim, we introduce two adaptive Rake receivers, which combine
a subset of the resolvable paths considering simultaneously the
quality of both the total combining output signal-to-noise ratio (SNR) and the individual SNR of each path. These schemes achieve
better adaptation to channel conditions compared to other known receivers, without further increasing the complexity. Their performance
is evaluated in different practical UWB channels, whose models are based on extensive propagation measurements. The
proposed receivers compromise between the power consumption,
complexity and performance gain for the additional paths, resulting in important savings in power and computational resources.
Abstract: IEEE 802.15.4a impulse radio-time hopping ultra wide
band (IR-TH UWB) physical layer, due to small duty cycle and very
short pulse widths is robust against multipath propagation. However,
scattering and reflections with the large number of obstacles in indoor
channel environments, give rise to dense multipath fading. It imposes
serious problem to optimum Rake receiver architectures, for which
very large number of fingers are needed. Presence of strong noise
also affects the reception of fine pulses having extremely low power
spectral density. A robust SRake receiver for IEEE 802.15.4a IRTH
UWB in dense multipath and additive white Gaussian noise
(AWGN) is proposed to efficiently recover the weak signals with
much reduced complexity. It adaptively increases the signal to noise
(SNR) by decreasing noise through a recursive least square (RLS)
algorithm. For simulation, dense multipath environment of IEEE
802.15.4a industrial non line of sight (NLOS) is employed. The power
delay profile (PDF) and the cumulative distribution function (CDF)
for the respective channel environment are found. Moreover, the error
performance of the proposed architecture is evaluated in comparison
with conventional SRake and AWGN correlation receivers. The
simulation results indicate a substantial performance improvement
with very less number of Rake fingers.
Abstract: This paper presents a new ultra-wideband (UWB) bandpass filter (BPF) with sharp roll-off and dual-notched bands. The filter consists of a triangle ring multi-mode resonator (MMR) with the stub-loaded resonator (SLR) for controlling the two transmission zeros at 2.8 / 11 GHz, the embedded open-circuited stub and the asymmetric tight coupled input/output (I/O) lines for introducing the dual notched bands at 5.2 / 6.8 GHz. The attenuation slope in the lower and higher passband edges of the proposed filter show 160- and 153-dB/GHz, respectively. This study mainly provides a simple method to design a UWB bandpass filter with high passband selectivity and dual-notched bands for satisfying the Federal Communications Commission (FCC-defined) indoor UWB specification
Abstract: In this paper, with the purpose of further reducing the
complexity of the system, while keeping its temporal and spatial
focusing performance, we investigate the possibility of using optimal
one bit time reversal (TR) system for impulse radio ultra wideband
multi-user wireless communications. The results show that, by optimally
selecting the number of used taps in the pre-filter the optimal
one bit TR system can outperform the full one bit TR system. In
some cases, the temporal and spatial focusing performance of the
optimal one bit TR system appears to be compatible with that of the
original TR system. This is a significant result as the overhead cost
is much lower than it is required in the original TR system.
Abstract: The bit error rate (BER) performance for ultra-wide
band (UWB) indoor communication with impact of metallic furniture
is investigated. The impulse responses of different indoor
environments for any transmitter and receiver location are computed
by shooting and bouncing ray/image and inverse Fourier transform
techniques. By using the impulse responses of these multipath
channels, the BER performance for binary pulse amplitude
modulation (BPAM) impulse radio UWB communication system are
calculated. Numerical results have shown that the multi-path effect
by the metallic cabinets is an important factor for BER performance.
Also the outage probability for the UWB multipath environment with
metallic cabinets is more serious (about 18%) than with wooden
cabinets. Finally, it is worth noting that in these cases the present
work provides not only comparative information but also quantitative
information on the performance reduction.
Abstract: In this paper, a double balanced radio frequency multiplier
is presented which is customized for transmitted reference
ultra wideband (UWB) receivers. The multiplier uses 90nm model
parameters and exploits compensating transistors to provide controllable
gain for a Gilbert core. After performing periodic and quasiperiodic
non linear analyses the RF mixer (multiplier) achieves a
voltage conversion gain of 16 dB and a DSB noise figure of 8.253
dB with very low power consumption. A high degree of LO to RF
isolation (in the range of -94dB), RF to IF isolation (in the range of
-95dB) and LO to IF isolation (in the range of -143dB) is expected
for this design with an input-referred IP3 point of -1.93 dBm and an
input referred 1 dB compression point of -10.67dBm. The amount of
noise at the output is 7.7 nV/√Hz when the LO input is driven by
a 10dBm signal. The mixer manifests better results when compared
with other reported multiplier circuits and its Zero-IF performance
ensures its applicability as TR-UWB multipliers.
Abstract: UWB is a very attractive technology for many
applications. It provides many advantages such as fine resolution and high power efficiency. Our interest in the current study is the use of
UWB radar technique in microwave medical imaging systems, especially for early breast cancer detection. The Federal Communications Commission FCC allowed frequency bandwidth of
3.1 to 10.6 GHz for this purpose. In this paper we suggest an UWB Bowtie slot antenna with enhanced bandwidth. Effects of varying the geometry of the antenna
on its performance and bandwidth are studied. The proposed antenna
is simulated in CST Microwave Studio. Details of antenna design and
simulation results such as return loss and radiation patterns are discussed in this paper. The final antenna structure exhibits good
UWB characteristics and has surpassed the bandwidth requirements.
Abstract: BER analysis of Impulse Radio Ultra Wideband (IRUWB) pulse modulations over S-V channel model is proposed in this paper. The UWB pulse is Gaussian monocycle pulse modulated using Pulse Amplitude Modulation (PAM) and Pulse Position Modulation (PPM). The channel model is generated from a modified S-V model. Bit-error rate (BER) is measured over several of bit rates. The result shows that all modulation are appropriate for both LOS and NLOS channel, but PAM gives better performance in bit rates and SNR. Moreover, as standard of speed has been given for UWB, the communication is appropriate with high bit rates in LOS channel.
Abstract: In this paper a tuning fork type structure of Ultra
Wideband (UWB) antenna is proposed. The antenna offers excellent
performance for UWB system, ranging from 3.7 GHz to 13.8 GHz.
The antenna exhibits a 10 dB return loss bandwidth over the entire
frequency band. The rectangular patch antenna is designed on FR4
substrate and fed with 50 ohms microstrip line by optimizing the
width of partial ground, the width and position of the feedline to
operate in UWB. The rectangular patch is then modified to tuning
fork structure by maintaining UWB frequency range.
Abstract: This paper presents a simple and original method for
the generation of short monocycle pulses based on the transient
response of a passive band-pass filter. The recorded sub-nanosecond
pulses show a good symmetry and a small ringing (13 % of the peak
amplitude). Their spectral density covers the range 3.1 GHz to
10.6 GHz. The possibility to adapt the pulse spectral density to the
indoor FCC frequency mask is demonstrated with a prototype
working at a reduced frequency (FCC/1000). A detection technique is
proposed.
Abstract: Performance of millimeter-wave (mm-wave) multiband
orthogonal frequency division multiplexing (MB-OFDM) ultrawideband
(UWB) signal generation using frequency quadrupling
technique and transmission over fiber is experimentally investigated.
The frequency quadrupling is achived by using only one Mach-
Zehnder modulator (MZM) that is biased at maximum transmission
(MATB) point. At the output, a frequency quadrupling signal is
obtained then sent to a second MZM. This MZM is used for MBOFDM
UWB signal modulation. In this work, we demonstrate 30-
GHz mm-wave wireless that carries three-bands OFDM UWB
signals, and error vector magnitude (EVM) is used to analyze the
transmission quality. It is found that our proposed technique leads to
an improvement of 3.5 dB in EVM at 40% of local oscillator (LO)
modulation with comparison to the technique using two cascaded
MZMs biased at minimum transmission (MITB) point.