Wireless indoor positioning systems have become very popular in recent years. These systems have been successfully used in many applications such as asset tracking and inventory management. This paper provides an overview of the existing wireless indoor positioning solutions and attempts to classify different techniques and systems. Three typical location estimation schemes of triangulation, scene analysis, and proximity are analyzed. We also discuss location fingerprinting in detail since it is used in most current system or solutions. We then examine a set of properties by which location systems are evaluated, and apply this evaluation method to survey a number of existing systems. Comprehensive performance comparisons including accuracy, precision, complexity, scalability, robustness, and cost are presented.

Survey of Wireless Indoor Positioning Techniques and Systems

Kelvin probe force microscopy and its application

Organic semiconductor lasers.

The increasing capability for manufacturing a wide variety of optoelectronic devices from polymer and polymer–silicon hybrids, including transmission fibre, modulators, detectors and light sources, suggests that organic photonics has a promising future in communications and other applications.

Organic photonics for communications

The concept of concurrent multiband low-noise-amplifiers (LNAs) is introduced. A systematic way to design concurrent multiband integrated LNAs in general is developed. Applications of concurrent multiband LNAs in concurrent multiband receivers together with receiver architecture are discussed. Experimental results of a dual-band LNA implemented in a 0.35-/spl mu/m CMOS technology as a demonstration of the concept and theory is presented.

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Concurrent multiband low-noise amplifiers-theory, design, and applications

The design of varactor-loaded transmission-line phase shifters using lumped elements is discussed in this paper. A monolithic-microwave integrated-circuit (MMIC) phase shifter is fabricated to verify the proposed topology. Only one control voltage is required for phase control. Within a continuously adjustable phase-control range of 360/spl deg/ and a frequency range from 5 to 6 GHz, a low transmission loss of 4 dB/spl plusmn/1.7 dB is measured. The phase shifter is realized with a commercial 0.6-/spl mu/m GaAs MESFET process and requires a chip area of only 0.8 mm/sup 2/. To the knowledge of the authors, the best results reported to date are reached for a continuously adjustable passive phase shifter with comparable circuit size. The presented circuit is well suited to wireless adaptive antenna transceivers, operating in accordance with the 802.11a, high-performance radio local-area-network and high-speed wireless-access-network type-a standard.

Varactor-loaded transmission-line phase shifter at C-band using lumped elements

A variable gain LNA was designed for HIPERLAN I. A noise figure of only 1.7 dB is measured at a gain of 14.5 dB and a power consumption of 9 mW (V/sub DC/=3 V, I/sub DC/=3 mA). Over an amplitude control range of 20 dB, the third order intercept point at the input is higher than -10 dBm, the spurious free dynamic range is higher than 55 dB and noise performance does not effectively degrade. Noise and intermodulation performance of different amplitude control methods as well as the required resolutions for D/A converters are investigated.

A 5.2 GHz variable gain LNA MMIC for adaptive antenna combining

A design-oriented analysis of microwave transmission-line class-E and class-F amplifiers is presented in this paper. Multiharmonic transmission-line load networks are analyzed and compared in terms of harmonic suppression and their effects on output power and efficiency. Based on this study, a design of highly efficient monolithic-microwave integrated-circuit amplifiers has been carried out. To allow circuit optimization and to simplify the design process, analytic expressions were derived for the most practical multiharmonic transmission-line networks. Fabricated amplifiers achieve state-of-the-art efficiency of 56.2% and 59.0% for class-E and class-F operation at K-band for power levels of 19.1 and 20.0 dBm, respectively. Moreover, without the need for supplementary filtering sections, harmonic suppression for operation well into compression is better than -25 and -30 dBc for the transmission-line class-F and class-E amplifiers, respectively.

Study and Design Optimization of Multiharmonic Transmission-Line Load Networks for Class-E and Class-F $K$ -Band MMIC Power Amplifiers

This paper presents a calibratable adaptive antenna combiner with three branches for high-performance radio local area network at 5.2 GHz. The system was mounted on a reinforced duroid substrate and enables the integration in a laptop interface card. Each branch consists of a bent stacked slot antenna, a low-noise-amplifier monolithic microwave integrated circuit (MMIC) with antenna/calibration switching and a vector modulator MMIC with an amplitude control range of 15 dB and 3600 phase control range. The signals of the three branches are combined by an active adder MMIC. A calibration is proposed to significantly improve the phase and amplitude control resolution and the yield of the designed MMIC circuits, which were fabricated using a commercial GaAs process. Each branch has a maximum power gain of 16 dB, a noise figure of 3.3 dB, and a 1-dB output compression point of -4 dBm. The whole system draws less than 28 mA from a 2.7-V voltage supply. The total required MMIC chip size is 10.8 mm/sup 2/.

Calibratable adaptive antenna combiner at 5.2 GHz with high yield for laptop interface card

We have investigated the cross-sectional electric field and potential distribution of a cleaved n+-InP/InGaAsP/p+-InP p–i–n laser diode using Kelvin probe force microscopy (KFM) with a lateral resolution reaching 50 nm. The powerful characterization capabilities of KFM were compared with two-dimensional (2D) physics-based simulations. The agreement between simulations and KFM measurements regarding the main features of the electric field and potential is very good. However, the KFM yields a voltage drop between n- and p-doped InP regions which is 0.4 times the one simulated. This discrepancy is explained in terms of surface traps due to the exposure of the sample to the air and in terms of incomplete ionization. This hypothesis is confirmed by the 2D simulations.

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Werner Bächtold

Papers

Varactor-loaded transmission-line phase shifter at C-band using lumped elements

A 5.2 GHz variable gain LNA MMIC for adaptive antenna combining

Study and Design Optimization of Multiharmonic Transmission-Line Load Networks for Class-E and Class-F $K$ -Band MMIC Power Amplifiers

Calibratable adaptive antenna combiner at 5.2 GHz with high yield for laptop interface card

Investigation of the cleaved surface of a p–i–n laser using Kelvin probe force microscopy and two-dimensional physical simulations