Jules Gauthier

Six-port digital receivers (SPDRs): A new design approach

A new SPDR design approach is proposed. The receier contains an RF discriminator, power detectors, a signal leel comparison circuit, a decoder, and data and carrier recoery circuits for BPSK and QPSK signals. The new receier operates solely on analog circuits, and the proposed design isalidated with circuit and system simulations of an RF discriminator and a Costas-type phase-locked loop, demonstration of a demodulator at 2.4 GHz, and MMIC fabrication of an RF discrimina- tor at 15 GHz. The new design approach offers interesting possibilities to achiee SPDR-on-a-chip. Q 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 25: 356)360, 2000.

Tunable microwave device: status and perspective

State-of-the-art frequency-agile technologies such as semiconductors, micro-electro-mechanical systems (MEMS) and ferrites are briefly overviewed and compared with the emerging ferroelectric techniques such as Ba/sub x/Sr/sub 1-x/TiO/sub 3/ (BST) that are becoming an attractive candidate for designing low-cost and miniaturized tunable integrated microwave devices such as filters and phase shifters. Particularities of ferroelectric materials are summarized and difficulties in connection with the use of BST thin-films in RF monolithic circuit design are addressed. On the basis of a commercially available sol-gel process, BST thin-films have successfully been deposited on alumina substrate to fabricate metal-insulator-metal (MIM) tunable capacitors. Early results of such capacitors at the room temperature indicate that a tunable ratio (C/sub max//C/sub min/) as high as 3.5 can be obtained over 1-6 GHz with 20 biasing voltage (34 V//spl mu/m) even though the ohmic loss remains high. This research also shows a 7% weak effect of hysteresis.

Breaking the Efficiency Barrier for Ambient Microwave Power Harvesting With Heterojunction Backward Tunnel Diodes

Harvesting low-density ambient microwave power as an alternative power source for small ubiquitous wireless nodes has been proposed in recent papers discussing emerging technologies like the Internet of Things and Smart Cities. However, a literature review of the state-of-the-art Schottky diode based microwave rectifiers shows that a maximum efficiency has been reached for such devices operating in the low-power regime, as is the case for ambient microwave power-harvesters. This work examines the underlying physical mechanisms responsible for this RF-to-dc power conversion efficiency limitation, and explores a high I-V curvature backward tunnel diode to overcome this efficiency limitation. Measurements of the 2.4 GHz RF-to-dc power conversion efficiency at -40 dBm input power demonstrates that the backward tunnel diode outperforms the HSMS-285B Schottky diode by a factor of 10.5 and the Skyworks SMS7630 by a factor of 5.5 in a lossless matching network scenario. A prototype built using a new GSG probe embedded with a matching circuit showed a total power conversion efficiency of 3.8% for -40 dBm input power and 18.2% for -30 dBm input power at 2.35 GHz.

Overcoming the efficiency limitation of low microwave power harvesting with backward tunnel diodes

This paper explores, for the first time, the use of high responsivity heterostructure backward tunnel diodes to enhance the conversion efficiency of ambient microwave power harvesters. Progress in advancing the performance of low power rectifiers has been slowed because the maximum possible efficiency using Schottky diodes has been reached. Measurements of RF-to-DC conversion efficiency at -40dBm/2.4GHz are reported in this paper, showing that the backward diode outperforms the HSMS-285B Schottky diode by a factor of 10.5 and the Skyworks SMS 7630 by a factor of 5.5. A narrowband rectifier circuit was designed, fabricated and tested, showing a total efficiency of 3.8% for a 100nW input RF power and 18.2% at 1μW input RF power, at 2.35GHz.

Quasi-optical cruciform substrate integrated waveguide (SIW) coupler for millimeter-wave systems

A new substrate integrated waveguide (SIW) coupler in the form of a cruciform structure is proposed and developed in this work. This coupler is composed of four arms waveguide section connected by a central junction. The central portion is partially etched to act as an impedance transformer and mirror. This coupler could be used for millimetre-wave and sub-millimetre wave applications without insuperable tolerance problem. A 3dB coupler design procedure is validated by electromagnetic -simulations (HFSS) and prototype experiments. Measured results on the basis of the realized prototypes agree well with theoretical predictions and simulated results. This coupler is demonstrated to have a 20% relative bandwidth with 20dB of isolation and return loss.

High-speed low-cost direct conversion digital receiver

In this paper, an analog carrier recovery loop is proposed and developed to provide a complete direct conversion digital six-port receiver operating at microwave ISM frequency of 2.45 GHz. Results on data rate limitation are shown for QPSK signals up to data rates of 52 Mb/s. Parametric measurements in connection with CW, adjacent channel and co-channel interferences are presented for a data rate of 40 Mb/s. Finally, phase offset between the carrier and the reference signal, along with carrier frequency deviation performance are also presented for a rate of 40 Mb/s.

Microfluidic device fabrication with serigraphy technique

This article provides the design and fabrication details of a new technique to build a microfluidic device with two parallel substrates and a silicone gasket. The fabrication process uses screen printing technology offering fast and low-cost microdevices without the need for high-cost fabrication equipment and special photoresist processes. Hermetic microfluidic channels of 300 µm width and 50 µm height having parallel facing electrodes on two substrates are made with simple serigraphy technique using silicone rubber. The fabricated devices were experimentally tested for detection and characterization of polystyrene particles and living cells by negative and positive dielectrophoresis. The reported technique enables simple manipulation, centering, detection and characterization of living cells at low and high frequencies.