Robert Weigel

On the synthesis of equivalent circuit models for multiports characterized by frequency-dependent parameters

The synthesis of lumped-element equivalent circuits for time-domain analysis of problems with frequency-dependent parameters is of great interest in microwave theory. This paper presents a systematic approach to generate minimal order realizations for passive microwave circuits characterized by either admittance, impedance or scattering parameter data. Also a very efficient method to ensure inherent system properties such as stability and passivity is described. Modeling examples for a two- and four-port system are given.

Wireless SAW sensors for surface and subsurface sensing applications

Surface acoustic wave (SAW) devices, used as filters or diplexers, are well established components in communications applications like in mobile handsets or television sets. The characteristics of SAW devices make them also well suitable for the application of wireless sensors or wireless identification tags. A great advantage of SAW sensors is their completely passive operation without the need for additional power supplies. SAW sensors can be designed to sense several physical or chemical quantities like temperature, pressure, stress, or gas concentration. During operation of the wireless sensor the energy delivered from an RF pulse sent by an interrogation unit is picked up by the antenna, stored in the surface acoustic wave, modified by the sensor effect and is finally transmitted back to the interrogation unit. In this paper the basic operating principles of SAW devices are reviewed and two applications, a state-of-the-art tire pressure sensor and a moisture sensor, are presented.

UTRA FDD Mode

This chapter provides a detailed description of the UTRA FDD mode. In the first section the key parameters are listed as a reference. A short section on the system architecture, the layer structure of the radio interface and its interworking with higher layers, and the bearer services provided in UMTS follows. The remainder of the chapter deals with the details of the physical layer, namely, transport and physical channels, spreading and modulation, coding and interleaving, physical layer procedures, compressed mode, and RF-characteristics. We will mostly use the terms MS or terminal instead of the 3GPP convention User Equipment (UE), and BS instead of Node B.

Analyzing the Target Recognition Capability of an Ultra-Wideband Radar System using Time-Frequency Algorithms

Ultra-wideband (UWB) pulse radar can provide high target resolution by using very short pulse durations. In the presence of heavy noise and interference of several pulses, the pulse-detection capability will degrade. Due to the transient behavior of UWB pulses, joint time-frequency algorithms can be used to achieve satisfying target resolutions. In this contribution, the de-noising and target resolution capabilities of various time-frequency representations are analyzed by simulations and measurements.

Challenges in Automotive Electromagnetic Compatibility Modeling and Simulation

Electromagnetic compatibility (EMC) issues are increasingly important to the automotive industry. Problems arise from the growing use of electronic systems on the one hand and the lack of flexibility in placement or design of electronic modules on the other hand. Consequently, an accurate system-level EMC analysis is required from early stages of the vehicle design process. This paper presents a concurrent EMC simulation process that incorporates the EMC behavior of the electronic equipment in the system-level automotive EMC simulation. The proposed process helps to identify and reject potential EMC problems introduced by new technologies. This cuts the risk of EMC failure and avoids costly and time-consuming redesigns.

Modern frequency estimation algorithms for FMCW radar systems

In frequency modulated continuous wave sensor systems for object distance measurement, use of the fast Fourier transformation for frequency estimation is widely adopted because of its comparably low execution time and available implementations. Inherent resolution restrictions make modern state-space based frequency estimators a viable alternative to this approach. Estimation of the correct model order, crucial to accurate distance measurement when used in a setup with an unknown number of targets, may be avoided by using active transponders. In this paper, application of a state-space frequency estimator is investigated with the use of measurement data in a system with an a priori known number of active targets. Evaluation results are analyzed and compared to performance of the Fourier transformation.

UTRA TDD Mode

The UTRA TDD mode is described in this chapter. We will concentrate on the differences to the FDD mode and will not repeat specifications which are the same as for the FDD mode.

Spread Spectrum Techniques

In this chapter we will present the basic idea behind spread spectrum systems together with some of the most important issues regarding their design and implementation. We will start with a definition of spread spectrum systems and consider their advantages as well as their disadvantages, after which the different types will be described. The direct sequence spread spectrum principle will be covered into more detail including a short mathematical representation and the derivation of the optimum receiver, since UMTS relies on this technique. A following section will deal with the very important topic of synchronization and we will close with a short coverage of past and present applications together with some historical notes on the origins of spread spectrum techniques. In this chapter we of course do not intend to cover the topic of spread spectrum comprehensively. We just want to lay the theoretical background of spread spectrum for a sufficient understanding of the CDMA technology and its application within UMTS. As in the foregoing chapters we have included several references to enable the reader to cover topics of interest in more detail.

UMTS Transceiver Design Issues

In this chapter we will first review the homodyne and heterodyne architectures (and other possibilities) for both transmitter and receiver in general and in particular with respect to UMTS. A survey of published analog frontends for UMTS follows. Possible future directions in the transceiver design conclude this chapter.

Introduction to UMTS

In this chapter we give an introduction into the background of 3G mobile communication systems. We will start with a general definition and the basic concept. A short section is devoted to market aspects to acquaint the reader with the economic facts and expectations behind 3G. A description of spectrum issues follows before we highlight the currently ongoing standardization process and the organizations involved.