A planar microwave dielectric sensing platform based on a microstrip ring resonator functionalized with a microstructure-engineered ZnO thin film is presented for liquid-phase ammonia detection. The resonator, operating around 5 GHz, was designed to ensure strong circumferential electric field confinement within a predefined annular sensing region. Full-wave electromagnetic simulations confirmed a stable modal behavior, geometrically controlled resonance frequency, and independently tunable quality factor through capacitive coupling optimization. Controlled ammonia exposure produced systematic and reproducible resonance shifts. A maximum frequency displacement of approximately 210 MHz was observed at 35% NH3, corresponding to a normalized shift of about 4% relative to the baseline resonance frequency. The response exhibited quasi-linear behavior over the 0-35% concentration range, yielding an average sensitivity of approximately 6.15 MHz per percent NH3 concentration. The loaded quality factor decreased moderately from about 44 under dry conditions to 32 at maximum concentration (approximate to 25-30% reduction), while preserving a well-defined resonance peak. The measured frequency shifts are consistent with first-order cavity perturbation theory, confirming that ammonia exposure increases the effective permittivity within the high-field ZnO-loaded region. Microstructural control of the ZnO film, achieved via RF sputtering power variation, directly influences effective permittivity modulation and sensing sensitivity. The results demonstrate a robust and physically validated microwave transduction mechanism based on controlled dielectric loading within a confined electromagnetic field.

This paper presents the design and simulation of a 32element microstrip patch antenna array operating at 24 GHz for millimeter-wave applications. The proposed array is designed on a Rogers RT5880 substrate. A compact Wilkinson power divider is employed to achieve uniform power distribution with excellent impedance matching and high port isolation. The simulated results demonstrate a reflection coefficient better than $\mathbf{- 3 0 ~ d B}$ for the single patch antenna, while the Wilkinson divider exhibits S11 below - 19 dB, equal power split of - 3 dB, and an isolation level of -20 dB between output ports. When integrated into the complete 32-element antenna array, the system maintains a strong impedance matching with a return loss around $-\mathbf{2 5 ~ d B}$ at $\mathbf{2 4 ~ G H z}$. The radiation characteristics confirm high directivity and improved gain, making the proposed antenna array suitable for automotive radar, millimeter-wave communications, and highfrequency wireless systems.

This paper presents the design of a highly reconfigurable interdigital bandpass filter (BPF) developed through a three-stage design approach. In the first stage, the influence of four low-loss dielectric substrates on the filter response is systematically analyzed to identify the optimal configuration. The selected substrate demonstrates excellent performance, achieving an input return loss of −38 dB, an insertion loss of −0.9 dB at 4.30 GHz, and a wide passband corresponding to a bandwidth (BW) of 2.20 GHz. In the second stage, two variable capacitors were incorporated into the baseline geometry, enabling manual tuning of the center frequency (f0) from 5.10 to 6.34 GHz, with (S11) better than −25 dB and (S12) close to −0.60 dB. In the final stage, the capacitors were replaced by SMV1413 varactor diodes, transforming the design into a fully voltage-controlled tunable filter. This configuration provides continuous frequency agility from 4.70 to 5 GHz without modifying the physical structure, while achieving (S11) levels down to −40 dB and insertion loss as low as −0.7 dB. The proposed architecture offers a compact, low-loss, and electrically reconfigurable solution, making it a promising solution for next-generation RF front-ends, adaptive wireless systems, and cognitive radio applications. Two independent Electromagnetic solvers (EM) were employed to validate the filter’s performance: an EM based on the Finite Integration Technique and the Advanced Design System 2026 (ADS) solver using the Method of Moments (MoM). The close agreement between the results produced by both platforms confirms the accuracy and robustness of the proposed reconfigurable bandpass filter structure.

This paper presents the design and performance evaluation of a circularly polarized antenna array intended for rectenna integration. A slot antenna element is first developed and optimized to achieve circular polarization with an axial ratio (AR) below 3 dB in the 5.8 GHz ISM band. To enhance the gain and improve power reception, a $2 \times 2$ antenna array configuration is then implemented. The effect of the substrate choice on antenna performance is investigated by considering three different materials: Rogers RO4003C ($\varepsilon_{r}=3.38, \tan \delta= \mathbf{0. 0 0 2 7}$, thickness $\boldsymbol{=} \mathbf{1. 5 2 ~ m m}$), RT/duroid $\mathbf{5 8 8 0}$ (RT1) with 1.02 mm thickness $\left(\varepsilon_{r}=2.2, \tan \delta=0.0009\right)$, and RT/duroid 5880 (RT2) with 1.57 mm thickness $\left(\varepsilon_{r}=2.2, \tan \delta=0.0009\right)$. Full-wave simulations are carried out to analyze key parameters, including reflection coefficient (S11), axial ratio bandwidth, and peak gain. The results demonstrate that the substrate properties strongly affect impedance matching, circular polarization bandwidth, and radiation efficiency. Comparative analysis highlights the trade-offs between low dielectric loss and physical thickness, providing useful guidelines for substrate selection in rectenna applications. The proposed design shows promising characteristics for efficient wireless power transfer and energy harvesting systems.

This paper introduces a new coplanar bandpass filter (BPF) designed for the 5.8 GHz frequency band, targeting wireless communication and Internet of Things IoT applications. The filter design, which is based on CPW technology with a Complementary Split-Ring Resonator CSRR, is mounted on a Rogers RO4003C substrate. This substrate has a thickness of 1.52 mm, a dielectric constant of 3.38, and a low loss tangent of 0.0027.The BPF operates with a center frequency of approximately 5.8 GHz, covering a bandwidth from 5.7 GHz to 5.88 GHz. Its performance is excellent, featuring a low insertion loss of 1.78 dB and a high return loss of 22 dB. The design was validated using two different electromagnetic solvers, both of which confirmed the filter’s low insertion loss within the passband and its strong rejection of out-of-band signals. With a compact size of just 16.07 × 21.20 mm2, the filter is a promising solution for miniaturized devices. The 5.8 GHz frequency is part of the widely used Industrial, Scientific, and Medical (ISM) band. The filter’s ability to isolate this specific frequency makes it essential for optimizing connection quality and performance in various applications. For instance, some IoT devices that require higher bandwidth utilize the 5.8 GHz band, and this filter is critical for ensuring reliable and stable communication.

This study presents the design and analysis of a compact circularly polarized rectenna operating at 2.45 GHz, intended for wireless power transmission (WPT) applications. The proposed structure includes a 2x2 patch array antenna and a voltage doubler rectifier circuit, both optimized to maximize RF-DC conversion efficiency. Simulations, carried out using ADS and another electromagnetic solver show excellent performance with a reflection coefficient (S₁₁) below -10 dB, an axial ratio below 3 dB in the ISM band, and a maximum gain of 11.14 dB for the antenna array. The RT5880 substrate (εᵣ = 2.2, tanδ = 0.0009) and 35 μm metal thickness were chosen to balance performance and simplicity of design. The results show an RF-DC conversion efficiency of up to 73.69% at 27 dBm, confirming the potential of this design for mobile WPT applications such as powering drones.

In recent years, transparent technology has seen a significant advancement in hardware devices, accordingly, researchers are becoming increasingly interested in transparent and conductive materials, one key strategy in transparent technology is the use of mesh metallization, which balances transparency and high-frequency performance. This study proposes a new mathematical model that aims to accurately represent how the meshed microstrip line behaves at frequencies up to 40 GHz and model the dispersive behavior of the transmission line using analytical calculations. This work focuses on determining the equivalent line parameters, such as propagation constants, attenuation constants, and propagation mode dispersion, which are crucial for characterizing line performance across various operational frequencies. This involves extracting the measured scattering parameters of the transmission line and converting them to an equivalent Chain Matrix. This transformation process is based on specific equations that relate the elements of the $S$-parameter matrix to those of the $A B C D$ matrix.

This paper proposes a compact and highly selective coplanar waveguide bandpass filter (BPF) optimized for ISM band applications around 2.4 GHz. The filter is based on coplanar waveguide (CPW) technology and is constructed on Rogers RT/duroid 5880 substrate, which has a thickness of 0.51 mm, a dielectric constant of 2.2, and a loss tangent of 0.0009. The filter demonstrates return and insertion losses of $\mathbf{2 4 ~ d B}$ and $\mathbf{1. 0 5}$ dB, respectively, with a center frequency near 2.4 GHz and an operating bandwidth ranging from 2.18 GHz to 2.64 GHz, resulting in a bandwidth of $\mathbf{4 6 0 ~ M H z}$. The design was simulated using two electromagnetic solvers based on different physical principles, both showing low insertion loss across the passband and strong signal rejection outside it. The overall size of the filter is $19.7 \times 22.05 \mathrm{~mm}^{2}$, making it a promising option for wireless communication and radio frequency signal processing applications. Notably, the 2.4 GHz ISM band is widely used, appearing in devices such as microwave ovens, Wi-Fi routers, and Bluetooth gadgets.

This paper presents a new configuration of a coplanar compact low pass filter (LPF) for terahertz applications based on coplanar-waveguide (CPW). It features a compact size with dimensions of 84.38 by 125.60µm2. The filter is mounted on a GaAs substrate having a thickness of 30 µm, a dielectric constant of 12.9 and loss tangent of 0.0001. The filter's cut-off frequency is 0.45 THz, and it exhibits a rejection outside the bandwidth below 20 dB. The design's validity is confirmed through simulations using two independent electromagnetic solvers, highlighting its potential for applications in terahertz imaging, non-destructive testing, satellite communications, medical diagnostics, and biosensing.

This work presents a compact bandpass filter BPF designed using coupled circular ring resonators implemented with microstrip technology. The key feature of the proposed design lies in the circular ring resonator, which primarily employs capacitive coupling to achieve resonance. The filter is mounted on an RO4003C substrate with a thickness of 1.52 mm, a dielectric constant of 3.38, and a loss tangent of 0.0027. It operates at a center frequency of 5.72 GHz with a bandwidth of 693 MHz, offering low insertion loss and effective suppression of unwanted signals outside the passband. The filter’s performance was verified through simulations carried out using two distinct electromagnetic solvers. Thanks to its compact structure, flexible design, and outstanding performance, this BPF marks a significant improvement in microwave filter technology and shows great promise for use in next-generation wireless communication systems, wireless power transfer, and 5.8 GHz rectenna arrays for RF energy harvesting.

This article presents a study of implantable blood pressure sensors based on a probe made up of four piezoresistors. An original method combining both measurements and calculations allows extracting the values of each piezoresistor without degrading the probe is developed. This study made it possible to create a simulation model in Cadence/Pspice electronic simulation software, considering the variation of the piezoresistor according to the temperature and the pressure. To our knowledge, no simulation model considering both the variation of the temperature and the pressure of each piezoresistor exists in the literature. So, the simulation of the sensor allows to quickly test the efficiency of the compensation circuit before its realization. Once the thermal drifts of the sensor have been quantified, a circuit based on PNP transistors is developed to compensate this thermal drift. This analog compensation technique ensures low cost, compactness and low power consumption. It proved experimentally effective in reducing thermal drift of the sensor. For example, the experimental thermal drift of the sensor is reduced from 9.97 mmHg/degrees C without compensation to 2.12 mmHg/degrees C after compensation at the pressure of 300 mmHg. This method has been validated with 3 pressure levels (0, 100, 200 and 300 mmHg).

The subject of this article falls into the category of research themes on systems for medical applications with the objective of monitoring the patient at home via tools adapted to his pathology. In this context, we describe here the design of a sole for the analysis of the gait for detect the presence of anomalies in the foot characterized by a gait disorder, which can be related to a chronic disease. The collaboration with a podiatrist is an additional point in our study, it allows to define or better zones of significant pressure of the foot to analyze the data for transform these numeric values into medically exploitable information. The sole contains several pressure sensitive piezoelectric sensors developed at the IETR laboratory. The data obtained with the deformation of these sensors will be sent directly by Bluetooth using a wireless acquisition card, the information will automatically be saved on a cloud in which the doctor will have access at all times.

The analysis of plantar pressures is an integral part of the series examinations carried out by the podiatrist, it allows him to visualize the distribution of the points of support and the movements of the foot during the different phases of walking. The system used for the analysis is a podiatry treadmill composed by piezoelectric sensors which react to the applied pressure. The recorded data will be converted into force data for a correct interpretation of the results by medical specialists. This article presents a part of the development of a podiatry sole based on piezoelectric sensors manufactured at the IETR-Nantes laboratory. The mechanical characterization of an industrial sensor (7BB-35-3L0) from Murata will be presented first to validate the repeatability and the reproducibility of the measurement method, which should allow to define the transfer function relating the output of the sensor to the applied stress. A Shimadzu EZ-X series universal electromechanical test frames are used to apply pressure to the sensor, at the same time as the machine records the force data, a national instrument acquisition card is connected to the sensor to collect his signal. Two methods are tested for the processing of the recorded data, the results obtained make it possible to validate a method which gives a constant coefficient representing the transfer function, thus leading to the final objective which is to characterize the flexible piezoelectric sensors manufactured at the IETR laboratory.

For reasons of availability and cost, patients are sent home increasingly early, with limited follow-up due to the complexity and size of medical devices. In this context, researchers from IETR and MIPS laboratories are working on a device which should monitor the progress of a patient, in order to detect early the aggravation of a disease such as Chronic Obstructive Pulmonary Disease (COPD) or diabetes with walking disorders. The device is based on flexible piezoelectric thin films (3 µm thick) that can be used as podiatric sensors and have been developed by the IETR laboratory. The originality of this work lies both in the approach to the design of the gait-monitoring device—because it was carried out directly in consultation with a doctor from the University Hospital of Nantes and a podiatrist—and in the portability of the device, which should eventually allow the follow-up of a patient at home. For this study, the flexible piezoelectric sensors have been elaborated using a Chemical Solution Deposition (CSD) process and a commercial aluminum (Al) foil as substrate. In order to increase the flexibility of sensors and to aid its insertion in a shoe, piezoelectric films have been encapsulated by lamination into polyethylene terephthalate (PET, 150 μm). In this paper, the elaboration and characterization of flexible piezoelectric sensors, analog-to-digital converter and wireless communication protocol used for data transmission are presented.

Implantable pressure sensors represent an important part of the research activity in laboratories. Unfortunately, their use is limited by cost, autonomy and temperature-related drifts. The cost of use depends on several parameters, particularly their low battery life and the need for miniaturization to be able to implant the animals and monitor them over a time that is long enough to be physiologically relevant. This paper studied the possibility of reducing the thermal drift of implantable sensors. To quantify and compensate for the thermal drift, we developed the equivalent model of the piezoresistive probe by using the Cadence software. Our model takes into account the temperature (34–39 °C) as well as the pressure (0–300 mmHg). We were thus able to identify the source of the drift and thanks to our model, we were able to compensate for it thanks to the compensation circuits added to the conditioning circuits of the sensor. The maximum relative drift of the sensor is (0.1 mV/°C)/3.6 mV (2.7%), a drift of the conditioning circuit is (0.98 mV/°C)/916 mV (0.1%) and the whole is (13.4 mV/°C)/420 mV (32%). The compensated sensor shows a relative maximum drift of (0.371 mV/°C)/405 mV (0.09%). The output voltage remains stable over the measurement temperature range.

This article presents a detailed study of the optical behavior of a leaky waveguide deflector in view of its utilization as key component to create a new solution for an analog to digital converter, capable to achieve very high data conversion rate (up to 40 giga sample per second). We present here the different works that we went through using software based on BPM (Beam Propagation Method) and FDTD (Finite Difference Time Domain) to determine the phase and amplitude characteristics of the leaky optical field. These pieces of information are indispensable to design of a diffractive optical lens to focus the leaky beam. As the results between theory and simulation are in good agreement, the next steps are to realize and finalize the component.

Great interest is devoted to electro-optic (EO) polymers since they allow the fabrication of very high performance microwave photonic components, such as optical modulators and analog-to-digital converters, due to a much better velocity matching between microwave and optical signal as well as a higher EO coefficient than the very popular inorganic LiNbO 3 material. This paper studies the influence of nanoparticle loading on optical properties of EO polymers. We are interested in the host-guest system. A proof of concept is investigated by using a polymer matrix in which we add Disperse Red One (DR1) chromophores. Our first investigations are realized with TiO 2 nanoparticles, which are transparent at the telecommunications wavelength of 1.55 μm. The m-lines technique allows measuring the refractive index of the films. As expected, the refractive index increases when weight-weight percentage of DR1 to PMMA increases from 3.5 wt.% to 14 wt.%. The refractive index increase tends to saturate at high DR1 percentages, which suggests that DR1 aggregation occurs. By adding TiO 2 nanoparticles, a further increase is observed that we discuss by considering both the refractive index of TiO 2 and the possibility to decrease the DR1 aggregation.

This article presents an analog method of compensation for thermal drifts of implantable piezoresistive blood pressure sensors used in wireless medical monitoring. A PNP transistor-based circuit in parallel with a variable resistor is used. This circuit is in series with the pressure probe constituted of four piezoresistors in Wheatstone bridge. This analog method is effective in reducing the thermal drift of the sensor and also has a low cost and consumption. The thermal drift of the sensor before compensation is 9.55 mmHg over the temperature range [34°C - 39°C] with the pressure of 300 mmHg and after compensation, the drift is reduced to 2.5 mmHg. This method has been validated with 3 pressure levels (0, 100, 200 and 300 mmHg).

This paper presents a soft low dielectric loss thermoplastic blend based on polyolefins as a dielectric material for microwave applications. To determine the dielectric properties, more precisely the relative permittivity εr and tan δ, characterization techniques and the elaboration of samples were customized to the 200-μm thick dielectric film. Dielectric properties were extracted from the peaks of the transmission coefficient S 12 measured from 10 MHz to 40 GHz with probe station and coplanar waveguide ring resonator. The measured dielectric constant and loss tangent of the investigated blends were found to be around ε r ≈ 2.45 and tan δ ≈ 0.01 in X-Band. A proof of concept of a patch antenna based on the developed soft dielectric film of polypropylene (PP)-based polymer blend was also made. The measured return loss of the antenna showed great agreement with simulation results with HFSS® software and reached -30 dB at an operating frequency of 9.7 GHz. An investigation of the radiation characteristics in the far field in anechoic room was made. The gain and the efficiency of the patch microstrip antenna, which were extracted and calculated from the radiation pattern attained 4.56 dB and 47% respectively. These here reported results are promising for the development of blend compositions for high frequency applications.