No / Near field imaging using microwaves in medical applications has gained much attention recently as various researchers have shown its capability and accuracy in identifying features of interest compared to well-known screening tools. This paper documents microwave imaging experiments for breast cancer detection. A simple phantom consisting of a plastic container with a low dielectric material imitating fatty tissue and a high dielectric constant object emulating tumor is scanned with a UWB microstrip antenna between 4 to 8 GHz. The measured results indicate that the prototype is a good candidate for imaging application.

Yes / This paper presents the advantages of using a wideband spectrum adopting multi-carrier to improve targets localization within a simulated indoor environment using the Time of Arrival (TOA) technique. The study investigates the effect of using various spectrum bandwidths and a different number of carriers on localization accuracy. Also, the paper considers the influence of the transmitters’ positions in line-of-sight (LOS) and non-LOS propagation scenarios. It was found that the accuracy of the proposed method depends on the number of sub-carriers, the allocated bandwidth (BW), and the number of access points (AP). In the case of using large BW with a large number of subcarriers, the algorithm was effective to reduce localization errors compared to the conventional TOA technique. The performance degrades and becomes similar to the conventional TOA technique while using a small BW and a low number of subcarriers.

Yes / The antenna presented in this study is a compact wideband monopole with wideband circular polarization that can be used across the whole antenna bandwidth. A rectangular C-shaped patch is partially covered by a ground plane in the proposed planar monopole antenna. Inserting a rectangular stub to the ground plane, etching a slit at the antenna patch, and adding a semicircular stub at the top of the antenna feed line increase the antenna impedance bandwidth (BW) and axial ratio bandwidth (ARBW). An FR4 substrate with overall dimensions of 25 mm×25 mm×1.6 mm is used to create the antenna. The antenna's observed impedance BW is 70% (4.55 GHz in the 4.3-8.85 GHz band), while the measured broadside ARBW is improved to a value of 82.2 percent (5.3 GHz along the range 3.8-9.1 GHz). The impedance BW is perfectly covered by the ARBW; hence the antenna can be considered circularly polarized throughout its operational spectrum. Within the antenna BW, the measured gain is greater than 1.5 dB.

Indoor localization systems have a variety of applications such as tracking of assets, indoor robot navigation, and monitoring of people (e.g. patients) in hospitals or at home. Global positioning system (GPS) offers location accuracy of several meters and is mainly used for outdoor location-based applications as its accuracy degrades significantly in indoor scenarios. Wireless local area networks (WLAN) have also been used for indoor localization, but the accuracy is too low and power consumption of WLAN terminals is too high for most applications. Ultra-wideband (UWB) localization is superior in terms of accuracy and power consumption compared with GPS and WLAN localization, and is thus more suitable for most indoor location-based applications [1-4]. The accuracy and precision requirements of localization systems depend on the specific characteristics of the applications. For example, centimeter or even millimeter localization accuracy is required for dynamic part tracking, while decimeter accuracy might be sufficient for tracking patients in hospitals or at home. Note that accuracy is not the only aspect of the overall performance of the system. Factors such as cost, range, and complexity should also be considered in system design. In the first part of this dissertation, a centimeter-accurate UWB localization system is developed. The technical challenges to achieve centimeter localization accuracy are investigated. Since all the receivers are synchronized through wire connection in this system, a wireless localization system with centimeter accuracy is introduced in order to make the system easier for deployment. A two-step synchronization algorithm with picosecond accuracy is presented, and the system is tested in a laboratory environment. The second part of this dissertation focuses on reducing the complexity of UWB localization systems when the localization accuracy requirement is relaxed. An UWB three-dimensional localization scheme with a single cluster of receivers is proposed. This scheme employs the time-of-arrival (TOA) technique and requires no wireless synchronization among the receivers. A hardware and software prototype that works in the 3.1-5.1 GHz range is constructed and tested in a laboratory environment. An average position estimation error of less than 3 decimeter is achieved by the experimental system. This TOA scheme with receivers in a single unit requires synchronization between the transmitter and the receiver unit. In order to further reduce system complexity, a new time-difference-of-arrival localization scheme is proposed. This scheme requires multiple units, each operating on its own clock. It avoids synchronization between the transmitter and receivers, and thus makes the development of the transmitter extremely simple. The performance of this system is simulated and analyzed analytically, and turns out to be satisfactory for most indoor localization applications. / Graduation date: 2013

No description available.

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Wideband data acquisition units have been used as part of an instrumentation system for several decades. Historically, these units operated asynchronously from each other, and from the rest of the instrumentation system when installed on the same test vehicle. When many wideband units are required to slave their formats or sampling rate to the test vehicle’s event of interest such as external computer event clock, radar, or laser pulse train; few solutions were available. Additionally, a single test vehicle may use ten to thirty wideband units operating at up to 20 Mbps each. Such systems present a challenge to the instrumentation engineers to synchronize, transmit safety of flight information, and record. This paper will examine a distributed wideband data acquisition system in which each acquisition unit operates under its own data rate and format, yet remains fully synchronized to an external fixed or variable simultaneous sampling rate to provide total system coherency. The system aggregate rate can be as low as a few Mbps to as high as 1 Gbps. Data acquired from the acquisition units is further multiplexed per IRIG-106 chapter 10 using distributed data multiplexers for recording.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / The desire to acquire large quantities of high speed vibration and acoustic data during aircraft testing is usually satisfied through on-board high speed recording methods. However there is often a need to have some of this data instantly available at the ground station for flight safety and other purposes. A Data Processor (DP) has been developed allowing an airborne data acquisition system to acquire large amounts of wideband analog data, process the data in real-time, and develop reduced bandwidth information from high bandwidth channels. The reduced data can be inserted into a Pulse Code Modulation (PCM) stream and telemetered via a Radio Frequency (RF) link with a potential for a 2000:1 reduction in bandwidth. This on-board processing capability also lends itself to additional tasks such as the generation of a reduced bandwidth marker channel which can flag critical time periods of data activity. This flagging technique can be used to facilitate ground station analysis of specific segments of data, resulting in significant cost and time savings.

Power consumption requires critical consideration during system design for portable wireless communication devices as it has a direct influence on the battery weight and volume required for operation. Wideband Code Division Multiple Access (W-CDMA) techniques are favoured for use in future generation mobile communication systems. This thesis investigates novel low power techniques for use in system blocks within a W-CDMA adaptive linear minimum mean squared error (LMMSE) receiver architecture. Two low power techniques are presented for reducing power dissipation in the LMS adaptive filter, this being the main power consuming block within this receiver. These low power techniques are namely the decorrelating transform, this is a differential coefficient technique, and the variable length update algorithm which is a dynamic tap-length optimisation technique. The decorrelating transform is based on the principle of reducing the wordlength of filter coefficients by using the computed difference between adjacent coefficients in calculation of the filter output. The effect of reducing the wordlength of filter coefficients being presented to multipliers in the filter is a reduction in switching activity within the multiplier thus reducing power consumed. In the case of the LMS adaptive filter, with coefficients being continuously updated, the decorrelating transform is applied to these calculated coefficients with minimal hardware or computational overhead. The correlation between filter coefficients is exploited to achieve a wordlength reduction from 16 bits down to 10 bits in the FIR filter block. The variable length update algorithm is based on the principle of optimising the number of operational filter taps in the LMS adaptive filter according to operating conditions. The number of taps in operation can be increased or decreased dynamically according to the mean squared error at the output of the filter. This algorithm is used to exploit the fact that when the SNR in the channel is low the minimum mean squared error of the short equaliser is almost the same as that of the longer equaliser. Therefore, minimising the length of the equaliser will not result in poorer MSE performance and there is no disadvantage in having fewer taps in operation. If fewer taps are in operation then switching will not only be reduced in the arithmetic blocks but also in the memory blocks required by the LMS algorithm and FIR filter process. This reduces the power consumed by both these computation intensive functional blocks. Power results are obtained for equaliser lengths from 73 to 16 taps and for operation with varying input SNR. This thesis then proposes that the variable length LMS adaptive filter is applied in the adaptive LMMSE receiver to create a low power implementation. Power consumption in the receiver is reduced by the dynamic optimisation of the LMS receiver coefficient calculation. A considerable power saving is seen to be achieved when moving from a fixed length LMS implementation to the variable length design. All design architectures are coded in Verilog hardware description language at register transfer level (RTL). Once functional specification of the design is verified, synthesis is carried out using either Synopsys DesignCompiler or Cadence BuildGates to create a gate level netlist. Power consumption results are determined at the gate level and estimated using the Synopsys DesignPower tool.

Ultrawideband (UWB) wireless systems employ signals with bandwidths in excess of 500 MHz or with relative bandwidth more than 20%. The radiated signals have low power spectral density. A decade ago, UWB wireless systems were deemed to be the technology that will deliver 'Gigabit-wireless' for short range communications. However, the performance of current systems is significantly below the initial expectations. This thesis explores the UWB wireless channel and shows how its properties limit the performance of current UWB systems. Furthermore, it is shown that if the knowledge of the channel is fully exploited a significant performance improvement of UWB systems can be achieved. The thesis begins with exploration of the channel properties. Unlike previous work, that has investigated either the 'classical narrowband' channel with bandwidth <100 MHz or the UWB channel with bandwidth >1 GHz, this work studies the transition between the narrowband channels with bandwidth of 1 MHz to the extremely wide band channels with bandwidths of up to 10 GHz. The thesis concludes that for signals with bandwidth <1 GHz UWB antennas and antenna arrays can be described by the classical means of gain and array factor, i.e. they treat such signals as 'narrowband'. In contrast, wireless propagation for signals with bandwidth > 100 MHz has properties 'like UWB channels' with bandwidths in the GHz range. Additionally, the thesis suggests a correction to the IEEE802.15.4a model for channel impulse response because as will be shown in the thesis many multi paths in the model are manifes- tations of the antenna impulse response. Hence multiple multipaths in the IEEE802.15.4a model actually represent a single multipath component. This reduces the number of multipath components in the model by approximately factor of five. The understanding of the transition between narrowband and ultrawideband channel is used to improve the spectral efficiency of impulse radio systems which traditionally use signals with bandwidth> 1 GHz. It is shown that the optimum signal bandwidth for impulse radio systems is in the range 150-450 MHz. Such systems balance the robustness against frequency selective fading with the reduction of duty cycle. Hence, the data-rate of impulse radio systems can be significantly improved. The frequency selective fading is shown to be the main limiting factor for the performance of the commercial UWB WiMedia systems with OFDM. It is shown that adaptive loading of OFDM sub carriers , which is compatible with the frequency selectivity of the channel, is more suitable for UWB OFDM systems than the use of strong Forward-Error-Correction measures. The introduction of the adaptive OFDM is not a significant change to the design of the scheme because the commercial WiMedia standard already foresees pilot OFDM symbols for channel estimation. The adaptive OFDM for UWB has already been considered by some authors. Unlike previous works, this thesis explores the performance of such a system in a large number of measured wireless channels. Finally, the thesis studies the MIMO techniques for UWB systems. Suitable schemes for fixed and adaptive OFDM are discussed. A realistic simulation using measured wireless channel shows that a 4x 1 system with a low complexity beam-steering and adaptive OFDM can deliver a data-rate of 400 Mbps over a range of 9 m. This performance is for a system with bandwidth 528 MHz (like in the WiMedia standard). A further increase can be achieved with the increase of the system's bandwidth.

In this report the feasibility of using a dual-tag setup in an indoor positioning system was investigated. The reason for the dual-tag setup was to be able to estimate both position and orientation. The system was designed using UWB-technology, with an time of flight trilateration algorithm to calculate the position. The orientation was then estimated from the relative position between the two tags. The system was tested both with stationary tags, but also with the tags moving along two paths. These tests were conducted for different separation distance between the tags, namely 20 cm, 30 cm and 40 cm. The result was that the mean position error for stationary tags was less than 8 cm for all separations and the mean orientation error was less than 3$^\circ$ for all separations. For the moving tag tests a decrease of the error in orientation of about 30 \% could be observed for a separation of 30 and 40 cm compared to 20 cm. However this difference is small in absolute values so more tests are needed to draw any conclusion about whether 30 and 40 cm tag separation performs better than 20 cm tag separation. The performance of the system could also be increased further by optimizing the anchor placement as well as the calibration of the antenna delays of the UWB-modules.