This paper reports a 2.45 GHz, low power dual circularly polarized (DCP) and dual access rectenna. It contains two dc-recombined rectifiers and a cross-slot coupled square patch antenna fed by a microstrip line. A judicious dc recombination scheme allows to minimize the RF power imbalance between accesses caused by multipath effects and consequently arbitrary polarized incident waves. The proposed rectenna is then able to harvest linearly polarized, right-hand circularly polarized (RHCP) and left-hand circularly polarized (LHCP) electromagnetic waves, with nearly stable performances. The rectenna has been optimized at-15 dBm per access and dedicated to remote and contactless supply low consumption sensors. It has been experimentally tested with very low power densities from 0.057 µW/cm 2 (E rms = 0.46 V/m) to 2.3 µW/cm 2 (E rms = 2.95 V/m). At 1.49 µW/cm 2 (-15 dBm on each rectifier), the structure exhibits an output dc voltage and a global efficiency of 189 mV and 37.7%, respectively when the azimuthal angle (Φ) of the incident field is equal to 0 •. Due to the nearly constant total gain of the DCP antenna and an appropriate dc recombination of the two rectifiers, the global efficiency slightly varies between 37.7% and 41.4% when the azimuthal angle (Φ) varies between-90 and 90 • .

This paper reports the design, simulation and experimental validation of an accurate liquid sensing technique in the nano-liter range. It is suitable for the detection and quantification of very small contents of liquid samples containing biological cells. The biosensor is based on an open-ended interdigitated capacitor (IDC) within a microfluidic channel. The microwave structure including the IDC is patterned in coplanar waveguide technology. The microfluidic channel is $100 \mu \text{m}$ thick and the IDC covers an area of $150 \mu \text{m}$ width and $90 \mu \text{m}$ length. This leads to a volume under analysis much lower than a nano-liter which allows the noninvasive and contactless microwave investigation of biological cells in their culture medium. This micro-device is used to extract the complex permittivity of liquid media from the measured scattering parameters within the frequency band ranging from 0.2 to 25 GHz. For ease of use, a SMA-connectorized version of the device with spring contacts probes to the biosensor is also proposed. Results concerning microparticle detection within the media are also presented, extending the use of the sensors to cellular environments.

In this paper, the DC-output improvement of a broadband rectenna has been demonstrated using pulse signal. The pulse waveform is optimized by varying its duty cycle as well as its modulation frequency. The rectenna operating from 1.6 to 2.8 GHz is characterized experimentally with low/medium RF power and different loads. The optimized waveform has a duty cycle that varies between 1 and 20% for a modulation frequency between 1 and 6 MHz. The results show that the DC voltage and the efficiency are improved over the frequency band of interest, particularly for frequencies below 1.8 GHz and those above 2.6 GHz. The DC-output improvement, compared to the 1-tone signal, is characterized by the calculation of voltage/efficiency gain. High gain values are experimentally obtained: close to 14 dB at 1.675 GHz and -20 dBm RF power. The voltage gain is greater than 0 dB for low (3 kΩ) and high (100 kΩ) loads. At 2.4 GHz and for a low load of 3 kΩ, 4-dB gain is measured at -30 dBm. For a load of 100 kΩ, the efficiency goes from 8.3 % for the 1-tone to about 74.7 the optimized waveform, at -15 dBm RF power level.

The main purpose of Inductive Power Transmission (IPT) is efficient power transfer. Yet the ability to localize the receiver is itself an interesting goal. In Qi standards for wireless power transfer, the localization is performed by using a coils array. The resolution of localization is equal to the diameter of the coils in the transmitter array. Decreasing the diameter of coils in transmitters increases the resolution of localization but also reduces the range of power transfer. IPT is used in inductive RFID (Radio Frequency Identification) where a trade-off between resolution of localization and range of tag detection arises. This paper proposes an original system making it possible to modify the resolution and the distance of operation independently. Calculations and simulations are implemented in MATLAB software. Experiments in low frequency validate the method and show the system capability to localize the receiver with good accuracy, with mean absolute error of 4 mm for localizing a receiver coil of 1 cm radius positioned in a box with dimensions 20*20*10 cm. Transmitter is a grid of 9 coils of 3.3 cm radius. After localization, the magnetic field is steered in the direction of the receiver to obtain a more efficient power transfer.

Recently, the need for a real time and less invasive solution to replace in-lab blood analysis by analyzing in-situ biological fluids (sweat, saliva, tear, urine, interstitial fluid) has grown alongside the development of micro fabrication techniques. pH determination is crucial for health monitoring (e.g., fetal acidosis supervision, sport activity, tumor detection and wound monitoring). Our work focuses on developing a potentiometric microsensor, targeting pH measurement on the fetal scalp during labor, employing nanoporous titanium nitride (TiN) as alternative sensing material. The pH probe contains a working electrode of 400 μm x 800 μm in size, integrated on a flexible polyimide substrate, creating an ultra-thin sensor with thickness below 20 μm. Microfabrication process and a complete characterization on performance of our flexible pH microsensor are presented, demonstrating a sensitivity of 53.2 mV/pH. Hysteresis was found at 3 mV maximum after 6 cycles, demonstrated a good reproducibility and led to a precision of 0.05 in pH. A comparison of the performance between porous and flat TiN (sensitivity of 53.7 mV/pH, hysteresis maximum of 5 mV and precision of 0.09 in pH) is presented, along with an evaluation of the dependence in the electrode size versus their performances. A preliminary in-vivo test was conducted on mice with the probe implanted under the skin. We recorded a stable open circuit voltage signal under anesthesia conditions. A compact measurement system was designed with a customized LCD screen for signal visualization, an EZO™ ORP circuit for data acquisition and an integrated SD card for data storage.