Along with the current trend of wireless technology innovation, wideband, compact size, low-profile, lightweight and multiple functional antenna and array designs are becoming more attractive in many applications. Conventional wireless systems utilise omni-directional or sectored antenna systems. The disadvantage of such antenna systems is that the electromagnetic energy, required by a particular user located in a certain direction, is radiated unnecessarily in every direction within the entire cell, hence causing interference to other users in the system. In order to limit this source of interference and direct the energy to the desired user, smart antenna systems have been investigated and developed. This thesis presents the design, simulation, fabrication and full implementation of a novel smart antenna system for future mobile applications. The design and characterisation of a novel antenna structure and four-element liner array geometry for smart antenna systems are proposed in the first stage of this study. Firstly, a miniaturised microstrip-fed planar monopole antenna with Archimedean spiral slots to cover WiFi/Bluetooth and LTE mobile applications has been demonstrated. The fundamental structure of the proposed antenna element is a circular patch, which operates in high frequency range, for the purpose of miniaturising the circuit dimension. In order to achieve a multi-band performance, Archimedean spiral slots, acting as resonance paths, have been etched on the circular patch antenna. Different shapes of Archimedean spiral slots have been investigated and compared. The miniaturised and optimised antenna achieves a bandwidth of 2.2GHz to 2.9GHz covering WiFi/Bluetooth (2.45GHz) and LTE (2.6GHz) mobile standards. Then a four-element linear antenna array geometry utilising the planar monopole elements with Archimedean spiral slots has been described. All the relevant parameters have been studied and evaluated. Different phase shifts are excited for the array elements, and the main beam scanning range has been simulated and analysed. The second stage of the study presents several feeding network structures, which control the amplitude and phase excitations of the smart antenna elements. Research begins with the basic Wilkinson power divider configuration. Then this thesis presents a compact feeding network for circular antenna array, reconfigurable feeding networks for tuning the operating frequency and polarisations, a feeding network on high resistivity silicon (HRS), and an ultrawide-band (UWB) feeding network covering from 0.5GHz to 10GHz. The UWB feeding network is used to establish the smart antenna array system. Different topologies of phase shifters are discussed in the third stage, including ferrite phase shifters and planar phase shifters using switched delay line and loaded transmission line technologies. Diodes, FETs, MMIC and MEMS are integrated into different configurations. Based on the comparison, a low loss and high accurate Hittite MMIC analogue phase shifter has been selected and fully evaluated for this implementation. For the purpose of impedance matching and field matching, compact and ultra wideband CPW-to-Microstrip transitions are utilised between the phase shifters, feeding network and antenna elements. Finally, the fully integrated smart antenna array achieves a 10dB reflection coefficient from 2.25GHz to 2.8GHz, which covers WiFi/Bluetooth (2.45GHz) and LTE (2.6GHz) mobile applications. By appropriately controlling the voltage on the phase shifters, the main beam of the antenna array is steered ±50° and ±52°, for 2.45GHz and 2.6GHz, respectively. Furthermore, the smart antenna array demonstrates a gain of 8.5dBi with 40° 3dB bandwidth in broadside direction, and has more than 10dB side lobe level suppression across the scan. The final stage of the study investigates hardware and software automatic control systems for the smart antenna array. Two microcontrollers PIC18F4550 and LPC1768 are utilised to build the control PCBs. Using the graphical user interfaces provided in this thesis, it is able to configure the beam steering of the smart antenna array, which allows the user to analyse and optimise the signal strength of the received WiFi signals around the mobile device. The design strategies proposed in this thesis contribute to the realisation of adaptable and autonomous smart phone systems.

Adaptive array antennas use has been limited to non-commercial applications due to their high cost and hardware complexity. The implementation cost of adaptive array antennas can be kept to a minimum by using cost effective antennas, reducing the number of elements in the array and implementing efficient beamforming techniques. This thesis presents techniques for the design of adaptive array antennas which will enable their cost effective implementation in wireless communication systems. The techniques are investigated from three perspectives, namely, reconfigurable antenna design, wide scan array design and single-port beamforming technique. A novel single-feed polarisation reconfigurable antenna design is proposed in the first stage of this study. Different polarisation states, namely, linear polarisation (LP), left-hand circular polarisation (LHCP) and right-hand circular polarisation (RHCP), are achieved by perturbing the shape of the main radiating structure of the antenna. The proposed antenna exhibits good axial ratio (< 3 dB at 2.4 GHz) and has high radiation efficiency in both polarisation modes (91.5 % - LHCP and 86.9 % - RHCP). With a compact single feeding structure, the antenna is suitable for implementation in wireless communication devices. The second stage of the study presents the design procedure of wide scan adaptive array antennas with reduced number of elements. Adaptive array antennas with limited number of elements have limited scanning range, reduced angular scanning resolution and high sidelobe levels. To date, design synthesis of adaptive array antennas has been targeted on arrays with a large number of elements. This thesis presents a comprehensive analysis of adaptive array antennas with less than 10 elements. Different array configurations are analysed and various array design parameters such as number of elements, separation between elements and orientation of the elements are analysed in terms of their 3 dB scan range. The proposed array, the 3-faceted array, achieves a scanning range up to ±70°, which is higher than ±56° obtained from the Uniform Linear Array. The faceted arrays are then evaluated in the context of adaptive beamforming properties. It was shown that the 3-faceted array is suitable for adaptive array applications in wireless communication systems as it achieves the highest directivity compared to other faceted structures. The 3-faceted array is then synthesised for low sidelobe level. Phase correction together with amplitude tapering technique is applied to the 3-faceted array. The use of conventional and tuneable windowing techniques on the 3- faceted array is also analysed. The final stage of the study investigates beamforming techniques for the adaptive array antenna. In the first part, beamforming algorithms using different performance criteria, which include maximum signal-to noise-ratio (SINR), minimum (mean-square Error) MSE and power minimisation, are evaluated. In the second part, single-port beamforming techniques are explored. In previous single-port beamforming methods, the spatial information of the signals is not fully recovered and this limits the use of conventional adaptive beamforming algorithms. In this thesis, a novel signal estimation technique using pseudo-inverse function for single-port beamforming is proposed. The proposed polarisation reconfigurable antenna, the 3-faceted array antenna and the single-port beamforming technique achieve the required performance, which suggests the potential of adaptive array antennas to be deployed commercially, especially in wireless communication industry.

Wireless communication systems are limited in performance and capacity by the major impairments of multipath fading and co-channel interference. Smart antenna can combat the impairments, thereby enhancing the system capacity and alleviating the problem of bandwidth limitation. In general, there are two main types of smart antennas; these are switched beam systems and adaptive array systems. An antenna array, which consists of a group of several antenna elements and digital signal processing units, can form several independent beams in different angles. Smart antennas aim the main beam in the direction of the target mobile user and locate the nulls in the direction of the interfering signals from other mobile users to enhance the signal-to-interference power ratio and system capacity. One of the most important parts in adaptive array antenna systems is the adaptive algorithm to adjust the weights of an array. These algorithms include unconstrained as well as constrained LMS, normalized LMS, structured gradient, RLS, CMA, and conjugate gradient method. In this thesis, we propose a new algorithm based on weight-partition RLS method to reduce the computational complexity. The major concept of our algorithm is decreasing the dimension size of data matrix. Performance and complexity of the proposed algorithm is evaluated and compared with traditional WRLS algorithm.

Over the last few years‚ the number of subscribers of wireless services has increased at an explosive rate. This ever growing demand for wireless communications services is constantly increasing the need for better coverage‚ improved capacity and higher quality service. Smart antennas system is an effective technology for the performance improvement of wireless communications. Switching-beam smart antennas use a number of fixed beams at an antenna site. The system provides a beam that offers the best signal enhancement and interference reduction. Using the approach of dynamic switching-beam antenna system‚ an intelligent sector beam synthesis of adjustable sector width can be established. By doing so‚ traffic load balancing can be achieved, and therefore, system capacity is increased. In this thesis, a beam-pattern synthesis algorithm proposed by M.H. Er is applied to shape array patterns with an adjustable mainlobe width and average sidelobe level reduction. Using an established database of weighting for circular arrays, the proposed smart antennas can adjust suitable sectors for the high dense subscribers not uniformly distributed. Simulation results demonstrate the proposed technique can dramatically improve the performance of traditional switching-beam antennas.

The switched-beam antenna is one type of the smart antennas, which consists of the antenna array and the beamforming network. The four-beam smart antenna generates four beams to cover a 120¢X area, which can be used to improve the carrier-to-interference ratio and the frequency reuse of a cellular system. Due to the attractive features of microstrip antennas such as low profile, easy fabrication, and low cost, we use microstrip antennas as array elements. In this thesis, we propose a novel four-beam beamforming network which consists of a 4¡Ñ4 Butler Matrix and four 180¢X power dividers. This network is able to provide low side-lobe level. A modified Butler Matrix not only simplifies the circuit of the 8¡Ñ8 Butler Matrix, but also meet the requirement of the original Butler Matrix. From the result of measurement, the side-lobe level of each beam of the modified Butler Matrix is less than ¡V10 dB. We also show that this method is applicable to any Butler matrix.

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / This paper addresses the system requirements of the C-Band TM antenna that will take the place of the S-Band TM antenna used in applications on munitions and targets that require a quasi-omni directional antenna pattern. For these applications, the C-Band TM effective radiated power (ERP) must be approximately 3 dB higher than the S-Band TM ERP to achieve the same system performance due mainly to weather and environmental differences. From a systems stand-point, this will be a problem for the following reasons: power amplification at higher frequencies is usually less efficient, there is a limit on prime power due to battery capabilities, and a more complex corporate feed at C-Band as compared to S-Band will produce more loss. This means that a more fruitful approach would be to use smart antenna ideas to achieve the required higher ERP as compared to current approaches of using higher power transistors and more battery power. Several smart antenna ideas are introduced in this paper, switchable driven element antenna is described including active amplification at each element.

Smart antenna systems are employed to overcome multipath fading, extend range, and increase capacity by using diversity or beamforming techniques in wireless communication systems. Understanding of the smart base antenna performance mechanisms for various environments is important to design cost effective systems and network. This dissertation focuses on the experimental characterization and modeling of the smart base station antenna performance for various propagation environment scenarios. An eight-channel Virginia Tech smart base station antenna testbed was developed to investigate performances of three reverse link diversity methods. The experiment campaign resulted in 245 sets of collected data over 83 measurement sites, which were used to compare the performance of space, polarization, and angle diversity under identical conditions. Measured propagation path loss, envelope correlation coefficients, power imbalances, and mean effective gain (MEG) are characterized as a function of distance between the base station and the mobile terminal to illustrate the diversity performance mechanisms over different propagation environments. The performance of the three base station diversity methods with selection combining (SC), maximal ratio combining (MRC), and equal gain combining (EGC) techniques for both urban and suburban non-line-of-sight (NLOS) environments are presented and summarized using the measured data. Forward-link performance of a twelve-fixed narrow-beam base station antenna system for urban NLOS environments is investigated using the same measured data. A new procedure is introduced to experimentally model the forward-link performance of muitlple-fixed narrow-beam (MFNB) antennas using the measured reverse-link vector channel response. The experimentally calculated lower bound performance result shows that it achieves 2.5 to 2.8 times higher average RF SIR compared to the conventional three-sector base station system for typical urban NLOS multipath fading environment conditions. Also, a new mobile user angle estimation algorithm using the muitlple-fixed narrow-beam antennas for NLOS multipath fading environment conditions is developed and the experiment results are presented. / Ph. D.

Typically, MAC protocols for mobile ad hoc networks assume omnidirectional antennas, and use of directional antennas offers many advantages, such as range extension, reduced co-channel interference, increased the degree of spatial reuse, improved the throughput of networks, and reduced the transmission power. There are many wireless ad hoc MAC protocol have been proposed. However, these protocols do not provide significant improvement of network performance because they can¡¦t let nodes to support multiple simultaneous transmissions or receptions ability. In this paper, we proposed a newly designed MAC protocols, we used adaptive beam-forming system to reduce the co-channel interference problem, and our proposed MAC protocol will enable nodes with multiple simultaneous transmissions and receptions ability. The handshake mechanism of proposed MAC protocol is that used receiver initialize handshake mechanism such as MACA/BI. We changed the Ready-to-Receive (RTR) control packet, which was used to poll neighbor nodes to be a dual-used control packet, Ready-to-Receive-Transmission (RTRT). Our simulation results will show that our proposed MAC protocol do exploit the advantage of space division multiple access that significantly reduced the problem of poor networks throughput which caused by bottleneck nodes in wireless ad hoc networks.

Smart antenna, which weights are obtained by Wiener solution, would suppress some undesired interference signals in spatial domain. The other interference signals that cannot be suppressed by smart antenna or caused by near-far effect will be post-processed by multiuser detectors. In the proposed algorithm, the cross-correlation matrix of desired signal and received signal from smart antenna algorithm would be applied to multiuser detector to reduce the complexity. From computer simulation results, the proposed algorithm has lower complexity and better BER performance than separate smart antenna or multiuser detection algorithms. Detail derivations of complexity and BER performance are also provided in this thesis.

yes / This paper presents a compact-size, low-cost smart antenna with electronically switchable radiation patterns, and reconfigurable polarizations. This antenna can be dynamically switched to realize three different polarizations including two orthogonal linear polarizations and one diagonally linear polarization. By closely placing several electronically reconfigurable parasitic elements around the driven antenna, the beam switching can be achieved in any of the three polarization states. In this design, a polarization reconfigurable square patch antenna with a simple feeding network is used as the driven element. The parasitic element is composed of a printed dipole with a PIN diode. Using different combinations of PIN diode ON/OFF states, the radiation pattern can be switched toward different directions to cover an angle range of 0◦ to 360◦ in the azimuth plane. The concept is confirmed by a series of measurements. This smart antenna has the advantages of compact size, low cost, low power consumption, reconfigurable polarizations, and beams.