Ultra-wideband Communication Systems - Assignment Example

Ultra-wideband (UWB) communication systems deliver the promise of very high bandwidth, reduced fading from multi-path and low power requirements. The American Military had been using ground breaking radar systems, wall imaging technologies until now. With the evolvement of the new Ultra-wideband (UWB) communication system, the transmission speed has increased by multiple folds bringing about low power dissipation, and low chip space. Looking at the various benefits of the Ultra-wideband (UWB) communication systems, the Federal Communications Commission (FCC) has recently allocated the 3.1-10.6 GHz spectrum for Ultra Wideband (UWB) application and this has presented a vast opportunity for a multitude of exhilarating challenges for the communications industry, including the design module of antenna. Ultra Wideband antenna requires the operating bandwidths as 100% of the center frequency and the successful broadcast of these Ultra Wideband signals that occupy the 3.1-10.6 GHz spectrum, requires the antenna to be in a linear phase, having low dispersion and its VSWR 2 all over the entire band. These properties (linear phase, low dispersion) are imperative for the transmission and reception of signals with least distortion. VSWR 2 is required for optimum impedance matching which ensures that a maximum 90% power radiation. The study further suggests that the Ultra Wideband antenna will only be compatible in case of a small integrated design circuit, which achieves the aim of a physically compact, planar Ultra Wideband antenna with sufficient impedance bandwidth, high radiation pattern and near omni directional radiation pattern. ACKNOWLEDGEMENTS First and foremost, I take the opportunity to thank my advisor, -----------------, for the opportunity he has given me to work on this project, and also for his amicable support and assurance in my work. His endurance and back-up were priceless to me all through the track of this research. He is the one to give a constant and essential push to me to be able to perform to the best of my capability. I am extremely grateful. I would also like to express gratitude to the entire UWB group for their queries, proposals, and support. In addition, I would also like to thank Professor -------------for connecting me with the Laboratory sp that I could carry out all my important measurements to bring out a clear and enhanced project report. I cannot entirely endow the success of this project only to people at this particular project work with me. I am thankful to those who have supported me throughout these years at the university through their true friendship and thoughtfulness. My family has been an incredible pillar of support including my wonderful parents. I cannot single out any one person who has been the sole support for this project report. I would like to thanks every one whom I might have missed out. Thanks. Contents ABSTRACT ACKNOWLEDGEMENTS CONTENTS 1. INTRODUCTION 1.1 Drive for Ultra Wideband Antenna Design 1.2 Thesis Contribution 2. Basics of UWB Antenna 2.1 Parameters, Requirements and Specifications 2.1.1 Impedance Bandwidth 2.1.2 Radiation Pattern 2.1.3 Half Power Beam Width 2.1.4 Directivity 2.1.5 Efficiency 2.1.6 Polarization 2.1.7 Gain 2.2.1 Requirements for an Optimal design 3. UWB system antenna design 3.1 Implementation 3.1.1 UWB SYSTEM CONSIDERATIONS 4. Conclusions REFERENCES CHAPTER 1 Introduction The wireless communication world has experienced a new revolution in the disguise of Ultra Wideband antenna technology which has shown the potential to transmit and receive data bits in the form of pulse based waveforms which can be easily compressed in time rather in frequency. The routine method of transmitting signal over a compressed bandwidth of frequency could not be easily demolished as the new Ultra-wideband (UWB) communication systems technology enables to transmit over a wide swath of frequencies such that a very low power spectral density can be effectively received. Ultra wideband (UWB) communication systems can be widely classified as a communication system which provides an instantaneous bandwidth many times greater than the minimum bandwidth that is required to broadcast any particular data or signal. The provision of excess bandwidth is the major attribute of the Ultra wideband (UWB) communication systems. The main idea behind Ultra wideband (UWB) communication systems is that they are capable of transmitting pulses of very short duration, as opposed to the conventional communication formats, which were able to send signals only in the form of sinusoidal waves. The other advantage of Ultra wideband (UWB) communication systems is that they transmit these pulses as precisely and efficiently as possible. The uniqueness of these UWB systems lies in their wide availability of instantaneous bandwidth and the possibility for uncomplicated applications. In addition, the wide bandwidth and prospects for low-cost digital design enables the Ultra wideband (UWB) communication system to work in different sized applications like a radar, or locator. Taking all these properties together, Ultra wideband (UWB) communication systems present before us a clear and technically sound advantage over other conventional approaches. Figure: Diagram explanation illustrating the equivalence of a pulse based waveform compressed in time to a signal of very wide bandwidth in the frequency domain. The above shown figure clearly illustrates the similarity of a narrowband pulse in the time domain to a signal of very wide bandwidth in the frequency domain. Also, the graph shows the equivalence of a sine wave signal which has been expanded in the time domain to a very narrow pulse in the frequency domain. Most of the narrowband systems occupy less than 10% of the center frequency bandwidth, and are transmitted at far greater power levels while the Ultra Wideband antenna communication system occupies greater 25% of the operating center frequency and need a small amount power for efficient transmission. 1.1 Drive for Ultra Wideband Antenna Design The emergence of Ultra wideband (UWB) communication systems has given a substantial push to the research work on optimal antenna design. The major challenge for the UWB antenna design is to achieve the target of a wide impedance bandwidth while still maintaining high radiation efficiency. The Ultra wideband (UWB) antennas are required to get a bandwidth greater than 100% of the centre frequency which guarantee a sufficient impedance match is attained throughout the band such that a power loss less than 10% due to reflections occurs at the antenna terminals. Apart from the requirement of achieving a wide band width, it is also required that the Ultra Wide band antenna possess a linear phase for optimal wave reception. This ensures a constant group delay which results in minimal pulse distortion during transmission. At the same time, an Ultra Wide band antenna needs a high radiation efficiency for transmission. Since the UWB antennas require very low transmit power, this power is utilized for high radiation efficiency. Since the transmit power is so low in UWB antennas, the power loss due to dielectrics and conductor losses is also minimized. 1.2 Thesis Contribution The paper intends to provide a clear background of the basics of antenna parameters that should be considered in designing a Ultra Wide band antenna. The paper further discusses the main differences and other considerate issues for the design of a UWB antenna. The operation of a UWB antenna is also discussed. While this part has been presented, more explanation will be provided to support sensitive approach into how the antennas work, and why they achieve wide bandwidth. Figure: Antenna Model CHAPTER 2 Basics of UWB Antenna 2.1 Parameters, Requirements and Specifications The most fundamental antenna parameters include impedance bandwidth, radiation pattern, directivity, efficiency and gain. The other parameters discussed in this paper are half-power beam width, polarization and range. All these parameters characterize a UWB antenna and determine its efficiency for a particular application. 2.1.1 Impedance Bandwidth Impedance bandwidth is the bandwidth for which the antenna will be matched to the input such that only 10% or less of the input signal is lost due to distortions and other signal reflections. To measure the Impedance bandwidth, the Voltage Standing Wave Ratio (VSWR) and Return Loss needs to be known. Both these values are dependent upon the reflection coefficient . is defined as ratio of the reflected wave Vo- to the incident wave Vo+ at a transmission line load as shown in the following Figure. Transmission Line Model, and can be calculated as:- = (V-) = Z line - Z load (V+) Z line + Z load VSWR measures the ratio of the amplitudes of the maximum standing wave to the minimum standing wave, and can be calculated by the equation below: VSWR = V max = 1 + V min 1 - The typical value of VSWR which provides a good impedance match is 2.0 or less. While Return Loss can be calculated as:- Return Loss = -10log|S11| 2, or -20log(||). For a good impedance match, the values should be as following: Read More