David Barras

Integrated Active Pulsed Reflector for an Indoor Local Positioning System

This paper presents an indoor localization system based on a frequency modulated continuous wave radar in the industrial-scientific-medical band at 5.8 GHz. An integrated active pulsed reflector behaves as a backscatter by regenerating the incoming phase with phase coherent startup at a constant frequency. The base station (BS) determines the distance to this reflector with a round-trip time-of-flight measurement. The active pulsed reflector is built around a switchable and tunable oscillator. The circuit has been fully integrated in a 0.18-¿m CMOS technology. Outdoor measurements revealed a positioning accuracy of 15 cm, while in a harsh multipath environment with omnidirectional antennas a positioning accuracy of 32.88 cm was measured. The localization system is capable of detecting multiple reflectors at the same time, and no synchronization between BSs is needed.

A Low-Power Baseband ASIC for an Energy-Collection IR-UWB Receiver

This paper reports on the realization and the characterization of an application-specific integrated circuit (ASIC) intended for the processing of impulse radio ultra-wideband (IR-UWB) baseband signals. The incoming baseband signals result from the direct down-conversion of IR-UWB radio-frequency pulses, which are modulated by a binary frequency-shift keying (BFSK) scheme. The realized mixed-signal integrated circuit features an analog demodulation based on the quadricorrelation method, a non-coherent pulse detector using an integrate-and-dump operation and a bit-level synchronization digital circuit. An novel acquisition algorithm intended for low duty-cycled IR-UWB signals enabling a signal-to-noise ratio (SNR) estimate is proposed. The baseband ASIC is able to demodulate, acquire and decode BFSK IR-UWB signals. It requires 13 mW of supply power during the initial acquisition and 6.5 mW during the signal tracking phase at a pulse repetition rate (PRR) of 5 MHz. The circuit is fabricated in a 0.18-mum CMOS technology.

Integrated Active Pulsed Reflector for FMCW Radar Localization

This paper presents an integrated active pulsed reflector (APR) functioning as a backscatterer in a power efficient local positioning system using a frequency modulated continuous wave (FMCW) radar in the ISM band at 5.8 GHz. The APR is designed as a switchable, tunable oscillator and is integrated in a 0.18-µm CMOS technology. The operating frequency of the APR can be tuned from 5.45 to 6.69 GHz, the output power is between 2.17 and 6.11 dBm and the matching is better than −9 dB over the complete tuning range. The active reflector including a low-frequency oscillator for modulation draws 46.2 mA from a 3.3 V power supply. The operation principle was verified and a measurement accuracy of 4.9 cm over a measurement range of 1.5 to 7.5 m was achieved neglecting multipath effects.

A wideband 0 to 60 dB CMOS variable gain amplifier for IR-UWB I/Q receivers

This paper reports on the realization of a variable gain amplifier (VGA) with an automatic gain control (AGC) loop for impulse-radio ultra-wideband (IR-UWB) signals. The circuit shows a gain range between 0 and 60 dB and a −3 dB bandwidth larger than 180 MHz over the whole gain range. The VGA also features a dual channel implementation for quadrature signal demodulation and shows very small I/Q imbalance. The circuit is fabricated in 0.18 µm technology, draws less than 5mA from a 1.8 V supply voltage and occpies an area 1 mm2.

Design and phase noise analysis of a multiphase 6 to 11 GHz PLL

This paper presents the design, the phase noise analysis and measurement results of a fourth-order phase-locked loop (PLL) circuit. The PLL is composed of a four-stage inductorless ring oscillator, a 1/16-divider, phase-frequency detector (PFD), charge pump and loop filter, which all are fully differential circuits. A tuning range of 6 to 11 GHz is achieved using delay interpolation elements in the ring oscillator. For jitter minimization, we analyze the noise contribution of each building block, identify the largest noise contributors, and evaluate the total PLL phase noise in s- and z-domain. The measured RMS jitter of 18 mUI agrees well with the predicted value of 15 mUI from our noise analysis. The PLL is fabricated in 90-nm bulk CMOS, consumes a current of 45mA at 1.1V and occupies an area of 0.1 mm2.

Interference characterization and UWB channel measurements for wireless intensive care patient monitoring

The electromagnetic environment in a hospital is characterized by means of a measurement campaign. This serves as a basis for the evaluation of best-suited future technologies to be used for wireless patient monitoring, where highest quality of service is required for sensors recording vital data. Results show that the UWB band features equal dynamic ranges as the ISM band but allows operation at a significantly lower power level, which is crucial for Body Area Networks where low power consumption is highly required. Furthermore UWB channel measurements are done in order to specify main propagation paths for scenarios with a volunteer in a bed. Multi-path propagation with reflections at the ceiling and the bedside monitor could be identified as main propagation paths beside the Line-of-Sight link. The impact of these propagation paths on the system performance were evaluated in system simulations using a non-coherent UWB system.

Using impulse Radio UWB for medical monitoring sensor networks: a performance evaluation

A compact testbed for real-time UWB performance evaluation in terms of un-coded bit-error rate is presented. Both the transmitter and the receiver are realized in form of a small PCB. This testbed represents a very versatile tool for the evaluation of IR-UWB as physical layer for various wireless technologies. It operates in the frequency range from 3.1-5.0 GHz with a maximum data rate of 10 MBit/s. Several measurements involving the influence of the human body are performed in a laboratory room in order to get a realistic picture of the performance and reliability that can be expected using IR-UWB for body area networks. In this paper the focus is set on medical monitoring applications. A body area sensor network was emulated and showed good connectivity for all tested scenarios. At a data rate of 10 Mbit/s the measured bit-error rate was better than 10-5 for every node operating in the network.

A Spectrum-Shaping Output Stage for IR-UWB Transmitters

This paper presents a novel on-chip wideband balanced-to-unbalanced (balun) transition circuit based on a complementary current inversion method. The proposed circuit features an easily controllable wide bandpass characteristic and is intended to be used as an output stage to filter ill-defined spectra of time-domain ultra-wideband pulses to fit regulation masks. We investigated the circuit in an active topology driven by differential pairs. A mathematical analysis is presented, as well as the implementation of an integrated circuit realized with IBM BiCMOS 0.18-mum technology.

Specification of the ADC interface for an interference robust UWB impulse radio

In this paper, the Analog to Digital Converter interface of a pulse based UWB system operating in the presence of strong interferer is specified. The minimum number of quantization bits is determined for interfering signals caused either by in-band or out-of-band service signals and for different front-end realizations. While for an undisturbed UWB communication link 4 quantization bits are sufficient, up to 14 bits are necessary for an UWB short range communication distance from 3–15 meters for a ‘worst-case’ interference scenario. Results show that a non-linear Analog to Digital Converter approach can significantly reduce the number of required bits from 14 to 8 bits. Fast Fourier Transformation processing methods have also been investigated in terms of processing load and influence on receiver sensitivity. We show that, with a moderate 32-points Fast Fourier Transformation resolution that enables simple serial processing, we can implement efficient interference notch filtering with negligible Bit Error Rate degradation of less than 0.5 dB at a Bit Error Rate of 10−3.

Poster: Impulse radio UWB testbed for indoor and sensor network applications

A compact testbed for real-time Ultra-Wideband (UWB) wireless system performance evaluation in terms of un-coded bit-error rate is presented. Both the transmitter and the receiver are realized in form of a small PCB. The system operates in the frequency range from 3.1--5.0 GHz with a maximum data rate of 10 MBit/s. By means of two examples this poster illustrates possible applications of the testbed. In the first measurement presented in the poster, the performance of different UWB antennas is compared. In the second example, measurements involving the influence of the human body are performed in order to evaluate the real-world performance of Impulse radio UWB (IR-UWB) communication systems for body area and sensor network applications.