Jacques Verdier

Strategy for Microwave Energy Harvesting From Ambient Field or a Feeding Source

Wireless energy transfer has been demonstrated using microwave electromagnetic support. Significant efficiencies are reported in the case of large dimension systems. Lots of embedded systems require a small power supply but with a large degree of integration where standard contactless energy transfer techniques suffer from poor efficiency. In such systems, RF input energy is rectified using rectenna circuits. The latter circuits are optimized for a given input RF power and cannot accommodate the two possible ways of energy transfer: the dedicated transfer (high power) or the harvesting of ambient energy (low power). This paper presents a novel rectenna architecture tunable for 900 MHz-2.45 GHz operation, able to process RF input power in the -30 to +30 dBm (dB miliwatt) range with a peak efficiency of 80%.

Potentials of an Adaptive Rectenna Circuit

Based on simulated and experimental results, this letter discusses the interests of a novel reconfigurable rectenna structure designed for rectification of UHF wireless energy. Several circuit topologies are combined in order to obtain high RF-to-dc energy conversion efficiency over a wide input-power range. Improvements are proposed in order to overcome the need for a maximum power point tracking (MPPT) device and to ensure high efficiency over a wide load-value range.

A Simple Way for Substrate Noise Modeling in Mixed-Signal ICs

Here is a complete methodology of substrate noise modeling. The aim of this study is to predict the perturbations induced by digital commutations flowing through the substrate to reach sensitive analog blocks. Till now, the studies have only taking into account the parasitic elements of the bonding wires. This work consists of each part of a mixed-signal design that induces power-and-ground bounces: the printed circuit board, the package, the bonding wires, the input-output ring, the on-chip power-supply distribution, and the digital core of the chip. A standard approach, called integrated circuit (IC) emission model, is used to create the substrate simulation model. By adding some elements to this power-supply model, we can simulate the transient substrate voltage induced by the digital part of a mixed-signal IC. A test chip has been realized in a 0.35-mum BiCMOS process to validate this substrate coupling model. Power-supply network, chip activity and substrate propagation of this circuit are obtained by using classical computer-aided design tools. Some Spice simulations of the modeled test chip, running in many different configurations, are shown. Comparisons between measurements and simulations are done and lead to the conception of an optimized version of the same circuit that induces less parasitic substrate voltages

Coupled simulation-measurements platform for the evaluation of frequency reuse in the 2.45 ghz ISM band for multimode nodes with multiple antennas

We address the problem of efficiently evaluating performance of concurrent radio links on overlapped channels. In complex network topologies with various standards and frequency channels, simulating a realistic PHY layer communication is a key point. The presented coupled simulation-measurement platform offers a very promising way of rapidly modelling and validating effective performance of multimode, multichannel and multiantenna radio nodes. An accurate analysis of radio channel is performed and then realistic performance with or without antenna processing is shown, verifying theoretical performance. Finally, available performance of concurrent communications on overlapped channels is exposed, showing that this approach is viable to enhance network capacity.

Low power front-end architecture dedicated to the multistandard simultaneous reception

In this paper, we address the architecture of multistandard simultaneous reception receivers and we aim to reduce the complexity and the power consumption of the analog front-end. To this end we propose an architecture using the double orthogonal translation technique in order to multiplex two signals received on different frequency bands. A study case concerning the simultaneous reception of 802.11g and UMTS signals is developed in this article. Theoretical and simulation results show that this type of multiplexing does not significantly influence the evolution of the signal to noise ratio of the signals. In the same time a 30% reduction of the power consumption is expected as well as a significant reduction of the complexity.

Voltage Reversal in Unbalanced Rectenna Association

Rectifying antenna (rectenna) associations can be advantageously used to harvest electromagnetic energy from different directions. When the rectennas are associated in series, their output voltages are added, and the electrical dc energy is more easily exploitable. This letter shows that if a rectenna receives significantly less energy than the others (i.e., unbalanced association), its voltage polarity may reverse. Simulation and experimental results show that when an unbalanced association is operated at maximum power point, voltage reversal can result in a total decrease in efficiency of up to 26%. Possible solutions to reduce these detrimental consequences are also discussed.

On the Compensation of RF Impairments with Multiple Antennas in SIMO OFDM Systems

This paper provides an analysis of the impact of radio frequency (RF) front end impairments (I/Q gain and phase imbalance, phase noise, non-linear distortion and direct current offset) on the performance of a single input multiple output orthogonal frequency division multiplexing (SIMO OFDM) receiver. We developed a new estimation/compensation scheme to jointly compensate for the effect of multipath and RF non- idealities on baseband signals in the special case of Zero-IF receivers. Some first results illustrating this approach are presented for a 4 antenna 802.11 g receiver with the SMI algorithm and with or without IQ imbalance, as well as BER curves for different phase noise models.

Global System Evaluation Scheme for Multiple Antennas Adaptive Receivers

This paper describes a global system approach to easily develop, simulate and validate a multi-antennas receiver structure. Our aim is to offer a rapid evaluation for future wireless systems, including promising techniques such as SIMO or MIMO, software defined radio (SDR), OFDM and interference cancellation. A particular focus is on the impact of RF front-ends characteristics on the effective performances of a receiver in a realistic environment. A complete connected solution based on Agilent Technologies tools is presented, combining simulations and measurements with realistic conditions. This testbed allows a direct evaluation of all parts of a wireless link with multiple antennas. For instance IQ imbalance and phase noise influence on a four antennas 802.11g receiver is herein exposed

Wireless Energy Transfer Using Zero Bias Schottky Diodes Rectenna Structures

This paper presents several RF-to-DC converter topologies and compares their performances based on measurements made on fabricated prototypes. A medium range wireless low power transmission experiment is presented. A low power DC-DC boost converter designed rectenna-generated energy conditioning is also discussed.

Impact of substrate perturbation on a 5 GHz VCO spectrum

This work investigates substrate coupling effects in mixed ICs, especially the perturbations on RF block. The authors present the impact of low frequency substrate noise perturbations on voltage-controlled oscillator (VCO) spectrum. A 5 GHz VCO test-chip is presented; several substrate taps have been placed inside VCO core to measure or to inject noise perturbations. The oscillation frequency sensitivity function of tuning voltage or bias current and spurious side-bands due to injected noise are measured to find out a relation between substrate noise and spectrum purity. Finally, a significant link between such device sensitivity functions and VCO spurs magnitude is demonstrated.