Passive Components for Ultra-Wide Band (UWB) Applications

UWB technology brings the convenience and mobility of wireless communications to very high-speed interconnects in the home and office due to the precision capabilities combined with the low power. This makes it ideal for certain radio frequency sensitive environments such as hospitals and healthcare as well as radars. UWB intrusion-detection radar is used for detecting through the wall and also used for security with fuse avoidance radar, precision locating and tracking (using distance measurements between radios), and precision time-of-arrival-based localization approaches. The FCC issued a ruling in 2002 that allowed intentional UWB emissions in the frequency range between 3.1 and 10.6 GHz, subject to certain restrictions for the emission power spectrum. Other definitions for ultra-wideband range of frequency are also used such as any device that has 500 MHz bandwidth or fractional bandwidth greater than 25% is considered an UWB enable high data rate to be transferred with a very low power that does not exceed −41.3 dBm

Design of an Ultra-Wideband Bandpass Filter for Millimeter Wave Applications

The advancement in filter designs for ultra-wide frequency spectrum are accelerated highly in this technological era. The main goal is to avoid interference of spurious signals with the authenticated signals resulting into counterfeiting of outcomes. This paper depicts the designs of Ultra-Wideband Bandpass filter (UWB BPF) with three different structures; using dual shunt ring resonator, split ring resonator and square patch resonator embedded at the centre of two parallel coupled microstrip lines. These designs are proposed with enhanced filter characteristics than conventional designs for millimeter wave range in automotive applications with improvement factors like traffic alerts and lane change assist. The frequency spectrum of 22-29GHz is used to meet FCC specifications along with 25.5GHz as the centre frequency. The complete simulations of the proposed designs are carried out using HFSS V13 software utilising RT/Duroid 6002 as a substrate with dielectric constant of 2.94. All designs are fabricated on the same substrate with equal substrate area of 5.8mm*2.8mm and thickness of 0.127mm. The return losses are 14dB, 16dB and 36dB and insertion losses are 0.4dB, 0.39dB and 0.30dB respectively of the proposed designs. The large fractional bandwidth of nearly 40%, high selectivity up to 82dB, especially in case of dual square patch resonator design, are extracted

UWB Technology

Ultra Wide Band (UWB) technology has attracted increasing interest and there is a growing demand for UWB for several applications and scenarios. The unlicensed use of the UWB spectrum has been regulated by the Federal Communications Commission (FCC) since the early 2000s. The main concern in designing UWB circuits is to consider the assigned bandwidth and the low power permitted for transmission. This makes UWB circuit design a challenging mission in today's community. Various circuit designs and system implementations are published in this book to give the reader a glimpse of the state-of-the-art examples in this field. The book starts at the circuit level design of major UWB elements such as filters, antennas, and amplifiers; and ends with the complete system implementation using such modules

Microwave and millimeter-wave rectifying circuit arrays and ultra-wideband antennas for wireless power transmission and communications

In the future, space solar power transmission and wireless power transmission will play an important role in gathering clean and infinite energy from space. The rectenna, i.e., a rectifying circuit combined with an antenna, is one of the most important components in the wireless power transmission system. To obtain high power and high output voltage, the use of a large rectenna array is necessary. Many novel rectennas and rectenna arrays for microwave and millimeter-wave wireless power transmission have been developed. Unlike the traditional rectifying circuit using a single diode, dual diodes are used to double the DC output voltage with the same circuit layout dimensions. The rectenna components are then combined to form rectenna arrays using different interconnections. The rectennas and the arrays are analyzed by using a linear circuit model. Furthermore, to precisely align the mainbeams of the transmitter and the receiver, a retrodirective array is developed to maintain high efficiency. The retrodirective array is able to track the incident wave and resend the signal to where it came from without any prior known information of the source location. The ultra-wideband radio has become one of the most important communication systems because of demand for high data-rate transmission. Hence, ultra-wideband antennas have received much attention in mobile wireless communications. Planar monopole ultra-wideband antennas for UHF, microwave, and millimeter-wave bands are developed, with many advantages such as simple structure, low cost, light weight, and ease of fabrication. Due to the planar structures, the ultra-wideband antennas can be easily integrated with other circuits. On the other hand, with an ultra-wide bandwidth, source power can be transmitted at different frequencies dependent on power availability. Furthermore, the ultra-wideband antenna can potentially handle wireless power transmission and data communications simultaneously. The technologies developed can also be applied to dual-frequency or the multi-frequency antennas. In this dissertation, many new rectenna arrays, retrodirective rectenna arrays, and ultra-wideband antennas are presented for microwave and millimeter-wave applications. The technologies are not only very useful for wireless power transmission and communication systems, but also they could have many applications in future radar, surveillance, and remote sensing systems

Harmonic Suppressed Reconfigurable Dual-band, Multi-mode Ultra-wideband, and Compact High Selective Microstrip Bandpass Filters

As an indispensable component, microwave bandpass filters play a very important role in many modern wireless systems. They are used to carry out the selection of only the wanted frequencies from RF signals with various spurious frequencies. The reconfigurable filter with multi-band has attracted much attention for both research and industry because of the increasing importance in making RF components that have multi-function with compact size. Wide or Ultra-wideband (UWB) bandpass filters are becoming more and more in demand in many wireless applications due to the high data transmission rate. This dissertation focuses on the study of microwave filters with many applications in various wireless systems. Firstly, bandpass filters using stepped impedance stubs are presented. The resonant frequencies and transmission zeros are analyzed, and harmonic suppression by novel S-shaped coupled feed lines is presented. A resonator with a dual-band characteristic is introduced, and it is analytically shown that each passband can be independently controlled by the parameters of the resonator. PIN diodes are used to introduce an electrically controlled dual-band bandpass filter. Secondly, symmetric stepped impedance resonators with asymmetric stepped impedance stubs are also presented to develop Ultra-wide band (UWB) bandpass filters with and without a notched band. The resonant frequencies and transmission zeros of the resonator are effectively located to achieve a very wide passband and a high attenuation rate in rejection bands. The interdigital coupled feed lines with rectangular slots are designed for a better passband characteristic. A notched characteristic is introduced by using modified feed lines to avoid the interferences with other existing signals. UWB bandpass filter performances in time-domain and frequency-domain are analyzed and discussed. Thirdly, UWB bandpass filters with a different configuration are developed. Similarly, the analyzed resonant frequencies are used to achieve a passband for UWB applications. A different technique is used to introduce a very narrow notched band within the passband. Time-domain analysis is made to verify the frequency-domain performance. Lastly, a very high selective wideband bandpass filter is presented using an inverted T-shaped resonator. The characteristic of the resonator is analyzed to design a bandpass filter with specified bandwidth. The short stubs are introduced to achieve a very high attenuation rate at both sides of the passband and a wide stopband characteristic. In summary, various microwave filters to meet the requirements of specific applications are studied and designed. Analysis and design methodology of the proposed microwave filters in this dissertation can be applied in many applications in wireless systems

Miniaturised and reconfigurable planar filters for ultra-wideband applications

An increasing demand for electromagnetic spectrum has resulted from the emergence of feature-rich and faster throughputs wireless applications. This necessitates the developments of dynamic reconfigurable or multifunctional systems to better exploit the existing spectrum. Future wireless devices will be expected to communicate over several bands with various other devices in order to fine tune the services they provide to the user. Each band may require a separate RF transceiver and such modern wireless multi-band multi-mode communication systems call for high performance, highly integrated compact modules. Since the Federal Communications Commission (FCC) released the unlicensed frequency band 3.1-10.6 GHz for ultra-wideband (UWB) commercial communications, the development race for commercialising UWB technology has seen a dramatic increase around the world. The aim of this research is to develop reconfigurable planar microwave filters for ultrawideband applications. The project investigates some key design issues of reconfigurable filters, which are being observed constantly in the latest development and realisation of microwave filters. Both analytical and numerical methods are performed to construct a realistic and functional design. Two different types of frequency reconfigurability are investigated in this thesis: discrete (e.g. PIN diode, Optical switch) and continuous (e.g. varactor diode). Using the equivalent circuits and considering the direct coupled filter structure in most cases, several topologies with attractive features are developed for future communication systems. The proposed works may be broadly categorised into three sections as follows. The first section explores a square ring shape close loop resonator along with an opencircuited stub in the symmetry plane. To realise a reconfigurable frequency states within the same spectrum, an innovative approach is developed for this case. An optical or photoconductive switch, comprised of a silicon die activated using near infrared light is investigated as a substitute of PIN diode and performances are evaluated to compare the feasibilities. In addition, a in-band interference rejection technique via externally coupled Tshape resonator is shown. However, it is observed that both structures achieve significant size reductions by utilising the inner part of the resonators. To improve the filter selectivity, a convenient design approach generating a pair of transmission zeros between both passband edges and a single zero in the stop band for harmonic suppression is discussed in the second section. Moreover, the development of notched rejection bands are studied and several novel methods to create a single and multiple notched bands employing the square ring shape structure are proposed. On inspection, it is found that the notch structure can be implemented without deteriorating the filter performances. The discussions are supplemented with detailed design examples which are accompanied by theoretical, simulated and experimental results in order to illustrate the filter development process and showcase practical filter performance. The third section reveals a novel highly compact planar dual-mode resonator with sharp rejections characteristics for UWB applications. A bandwidth reconfiguring technique is demonstrated by splitting its even-mode resonance. Filter structure with the dual-mode resonator is shown to have a relatively wide tuning range, significantly low insertion loss and a constant selectivity along with frequency variations in comparison to similar published works. Finally, the earlier dual-mode structure are modified to realise a dual wideband behaviour. A detail analysis with comprehensive design procedures is outlined and a solution for controlling the frequency bandwidths independently according to the application interest is provided. In line with the previous section, experimental verification is presented to support and supplement the discussions

A Novel Wideband Bandpass Filter using H-shaped DGS

This paper presents a novel compact wide-band bandpass filter (BPF) having good selectivity. It is designed using a dual-plane structure which consists of a parallel-coupled microstrip line on the upper surface and three H-shape defected ground structures (DGS) on the ground plane. By adding three H-shape DGS units on the ground plane, then properly adjusting their dimensions and position, the bandwidth and selectivity of the designed filter can be significantly improved. A compact prototype of wide-band microstrip bandpass filter has been designed, fabricated and measured for the wireless systems applications. The filter exhibits a center frequency at 4.8 GHz, passband from 2.8 GHz to 6.8 GHz with best insertion loss and return loss of 0.8 dB and 40 dB, respectively. The measured results agrees well with the theoretical expectations validating the proposed design

Reconfigurable Microstrip Bandpass Filters, Phase Shifters Using Piezoelectric Transducers, and Beam-scanning Leaky-wave Antennas

In modern wireless communication and radar systems, filters play an important role in getting a high-quality signal while rejecting spurious and neighboring unwanted signals. The filters with reconfigurable features, such as tunable bandwidths or switchable dual bands, also play a key part both in realizing the compact size of the system and in supporting multi-communication services. The Chapters II-IV of this dissertation show the studies of the filters for microwave communication. Bandpass filters realized in ring resonators with stepped impedance stubs are introduced. The effective locations of resonant frequencies and transmission zeros are analyzed, and harmonic suppression by interdigital-coupled feed lines is discussed. To vary mid-upper and mid-lower passband bandwidths separately, the characteristic impedances of the open-circuited stubs are changed. Simultaneous change of each width of the open-circuited stub results in variable passband bandwidths. Asymmetric stepped-impedance resonators are also used to develop independently controllable dual-band (2.4 and 5.2 GHz) bandpass filters. By extending feed lines, a transmission zero is created, which results in the suppression of the second resonance of 2.4-GHz resonators. To determine the precise transmission zeros, an external quality factor at feeders is fixed while extracting coupling coefficients between the resonators. Two kinds of feed lines, such as hook-type and spiral-type, are developed, and PIN diodes are controlled to achieve four states of switchable dual-band filters. Beam-scanning features of the antennas are very important in the radar systems. Phase shifters using piezoelectric transducers and dielectric leaky-wave antennas using metal strips are studied in the Chapters V-VII of this dissertation. Meandered microstrip lines are used to reduce the size of the phase shifters working up to 10 GHz, and reflection-type phase shifters using piezoelectric transducers are developed. A dielectric film with metal strips fed by an image line with a high dielectric constant is developed to obtain wide and symmetrical beam-steering angle. In short, many techniques are presented for realizing reconfigurable filters and large beam-scan features in this dissertation. The result of this work should have many applications in various wireless communication and radar systems

Compact and multiband metamaterial hairpin-line bandpass filters

In RF and microwave field, the bandpass filters are very important in communication systems. Bandpass filters are used as frequency selective devices in many RF and microwave applications such as transmitter and receiver. In recent years, a new type of artificial materials called as metamaterials have attracted the attention of many researchers. Metamaterials have a wide range of potential uses in communication areas such as optical and RF design. The metamaterial is a material engineered to have an electromagnetic property that is not found in nature. Thanks to the presence of these properties many researchers have using the metamaterial to produce the high performance and compact devices. The rapid development of microwave and millimeter wave in communication systems greatly stimulates the demand for high-performance bandpass filters with compact dimensions, low insertion loss, high attenuation in the stopband, low cost and multiband responses. In this project, the compact and multiband metamaterial hairpin bandpass filters have been proposed to reduce the size of the filter and to provide a multiband filter with less complex structure. The proposed bandpass filters were designed by using the complementary split ring resonator (CSRR) structure. The compact size was achieved with size reduction of 10% from the conventional hairpin filter. For the proposed multiband bandpass filter, two-band frequency responses were obtained at 3.5 and 5.5 GHz. Moreover, both of them have an insertion loss less than 1 dB and high attenuation at stopband