Preface

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. The major aim of the book is to introduce the readers to the basic design principles and building blocks that are necessary for such technology. In addition, the latest research innovations, especially in the area of circuits and systems, are presented. Various circuit designs and system implementations are described within 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.

The first chapter of the book is titled "Frequency Reconfigurable UWB Antenna Design for Wireless Applications" written by R. K. Sarraswat and M. Kumar. The chapter introduces a reconfigurable antenna suitable for WLAN, WiMAX, WiFi, and UWB wireless applications. The antenna is capable of switching between the narrow band, dual band, and UWB modes by using five p-i-n diodes placed inside an inverted L-shaped ground slot. The proposed design provides for easy integration with cognitive radio and multi radio wireless terminal devices. Radiation characteristics of the proposed antenna are achieved with good impedance matching at these resonant frequencies. The radiation pattern, gain, and efficiency are consistent over all the operating bands, making the proposed antenna a good choice for wireless applications.

The second chapter is titled "UWB Circuits and Sub-Systems for Aerospace, Defence, and Security Applications" and is written by E. Limiti and P. E. Longhi. This chapter reviews the topology, technology, and trends of microwave circuits in UWB systems for aerospace and defence applications. This includes front-end and back-end circuits, amplifiers and mixers, ADCs, and chip integration techniques. An outline on multi-functional circuits (Single-Chip Front-Ends and Core-Chips) is also presented.

The third chapter is titled "Inner Tapered Tree Shaped Ultra Wide Band Fractal Antenna with Polarization Diversity" and is authored by S. Singhal. The chapter introduces a compact third iteration fractal antenna for UWB using an orthogonal arrangement of two antenna elements. The designed antenna has wider bandwidth and excellent polarization diversity performance, which makes it suitable for UWB polarization applications in future wireless communication systems to mitigate the multipath fading.

The fourth chapter is titled "Antennas for UWB Applications" and is authored by S. Nikolaou and A. Quddious. The chapter presents selected antenna designs in relation to the UWB applications and their dictating radiation and operation principles. The demonstrated UWB antennas include antennas for handheld devices used for

personal area network (PAN) communications, antennas used for localization and positioning, UWB antennas for RFIDs, radar antennas for through-wall imaging, for ground penetrating radar, for breast tumor detection, and more generally, UWB antennas used for sensing. For some of the aforementioned applications, UWB antennas with special characteristics are needed and these are presented in this chapter, with the relevant applications. These include reconfigurable UWB antennas, metamaterial-loaded UWB antennas, and conformal UWB antennas. The usefulness of these special characteristics in comparison with the claimed advantages is critically evaluated.

The fifth chapter is titled "The UWB Bandpass Filters", which is authored by L.-T- Wand, Y. Xiong, and M. He. The chapter reviews the development process and regulations of UWB bandpass filters. Subsequently, it focuses on the application scenarios of UWB filters in UWB communication systems and the unique merits of UWB filters. In addition, the primary performance specifications of the UWB filters, including insertion loss, return loss, the level of out-of-band attenuation, and roll-off-rate are also presented. After a brief discussion of microwave network theory, several methods for implementing UWB filters are summarized. Furthermore, the design of the UWB filter with notch band is presented in the last section of the chapter.

Finally, the last chapter titled "Passive Components for Ultra-Wide Band (UWB) Applications" is authored by D. N. Elsheakh and E. A. Abdallah. This chapter introduces many types of UWB antennas. The first type is the monopole antenna, which is used as linearly polarized antennas. It has proven to be the best choice for use in various automobiles and mobile equipment due to its simplicity in design. Multilayer antenna with multiple feed points are different types used in UWB antennas with moderate gain. Log parodic and Yagi antennas are other types of UWB with high gain. Electromagnetic band gap (EBG) structures as defected ground or split ring resonators are also used to improve the antenna bandwidth and achieve UWB.

Different UWB filters are presented and described in this chapter as well. These filters may be switchable or tunable in order to introduce notch frequencies within the passband to provide interference immunity from unwanted radio signals, such as wireless local area networks (WLAN) and worldwide interoperability for microwave access (WiMAX) that cohabit within the UWB spectrum. With the current scenario of emerging services of the wireless communication systems, the need for compact multiband filtenna (filter combined with antenna) with the ability to cover the current standards at the microwave band and the next generation standards at the millimeter wave band simultaneously is rising. Also, the operation of cognitive radio and self-adaptive systems need to dynamically monitor the frequency spectrum in search of the unused licensed channels. All these applications need different types of filtennas, which may be fixed, switchable, or tunable that can operate in the UWB range of frequency and also with narrow band modes to cover for example UWB/WiMAX applications.

> **Dr. Mohamed Kheir** Keysight Technologies, Germany

> > **1**

**Chapter 1**

**Abstract**

**1. Introduction**

between narrowband modes [3–5].

Applications

Frequency Reconfigurable UWB

A frequency band reconfigurable antenna is designed and experimentally analyzed. Proposed design achieve UWB (3.1–10.6 GHz), two dual band and two narrow band switching states by implementation of PIN diodes inside the slotted ground. Antenna covers the various wireless standards WLAN, WiMAX, WiFi and UWB with return loss S11 < −10 dB. Proposed antenna is also operating at 9.2 GHz to include the airborne radar applications. Simulated and experimental results are

Present scenario of wireless communication system required compact and multiple band antenna design. Since many systems are operating at multiple frequency range, requiring dual and triple band antenna for various applications such as WLAN, WiMAX, RFID, satellite communication, etc. Presently, many printed monopole antenna are proposed. Serve for wireless applications to cover the wireless standards for Wireless local area network (WLAN: 2.4–2.48, 5.15–5.35, and 5.75–5.825 GHz) and worldwide interoperability for microwave access (WiMAX: 3.4–3.69 GHz) are two among the available wireless standards which allow interconnections of devices for communication. To achieve multi-functionality, various parameters of antenna such as polarization characteristics, resonant frequency, patterns and impedance bandwidth etc., are reconfigured as per requirements [1]. Presently wireless communication systems are adopting the concept of cognitive radio system where using a sensing antenna performing the monitoring of the spectrum, and can be reconfigured to operate over a desired frequency band. This system is required a frequency band reconfigurable antenna as a sensing element [2]. Most of frequency band reconfigurable antennas providing the band switching

Antenna obtained the quad-band switching by implementation of microelectromechanical systems (MEMS) switch [3]. Another frequency band reconfigurable patch antenna is proposed that operate in four different modes with the help of switching elements [4]. Recently, many microstip patch antenna have been designed that indicate the switching facility in narrowband as well as wideband modes [6–11]. In [6], a Vivaldi antenna is designed that provide the wideband and

Antenna Design for Wireless

*Ritesh Kumar Saraswat and Mithilesh Kumar*

**Keywords:** cognitive radio (CR), frequency-band reconfigurable, RF switch p-i-n diode, ultra wideband (UWB) antenna, WLAN

compared and found to be in good agreement.
