This paper reports preliminary measurements on a MEMS resonator aimed at developing a passive wireless sensor based on intermodulation principles. By exploiting the nonlinear response of a low-frequency MEMS device, we demonstrate two-tone heterodyne excitation at distinct carrier frequencies, extending up to the 868 MHz ISM frequency band of the antenna in which the MEMS will be integrated. This technique offers a major advantage: it enables selective detection of the MEMS response while effectively rejecting electromagnetic clutter, thereby improving both the potential reading range and sensitivity for future wireless sensing applications.

This work provides an electrically small antenna design that covers the band from 500 MHz to 3000 MHz with an unusual stable directional radiation. The antenna is frequencyagile with narrow instant bandwidths near the lowest frequency band. The antenna showed 50 instant bandwidths, with stable directional radiation pattern all over the tunable bandwidth. The theoretical foundation behind such antenna structure is explained. The proposed antenna is composed of 2 crossed radiating elements to generate a right-hand or left-hand circular polarization, but can be used with a single element if a linear polarization is needed.

This paper presents the design of a frequencyreconfigurable super-directive parasitic array. The array consists of three top-loaded dipoles, spaced by $0.144 \lambda$ at 878 MHz. To enable frequency reconfigurability of the radiated beam, the parasitic dipoles are loaded with varactors acting as tunable capacitors. Adjusting the varactors capacitances within an optimized range shifts the frequency of maximum directivity over a wide band. To match the antenna across different subbands, a reconfigurable L-matching circuit based on two varactors was integrated into the driven dipole. Varying the capacitances of the matching varactors shifts the antenna operating sub-bands, enabling operation over a wide frequency band. The designed array exhibits a tunable directivity bandwidth of 470 MHz, from 824 MHz to 1294 MHz with directivity and gain greater than 9 dBi and 8 dBi, respectively. Furthermore, the antenna achieves a −10 dB matched tunable bandwidth of 382 MHz from 834 MHz to 1216 MHz.

This work presents a study of the impact of the excitation technique on the frequency agility performance of a capacitively loaded loop (CLL) electrically small antenna (ESA). Three excitation techniques are presented and analyzed: electric-dipole based excitation, magnetic-dipole based excitation, and short-circuit based excitation. All the designs are electrically small with a maximal electrical size of ka less than 0.4. To compare the agility performances achieved by each excitation technique, the tunable bandwidth (TBW), the fractional tunable bandwidth (FTBW) and agility efficiency (AE) are used as figures of merit. The comparison reveals that the short-circuit based excitation archives the optimal performances with a TBW of 1104 MHz, a FTBW of 146.42% and an AE of 83.15 MHz/pF. Furthermore, it presents a radiation efficiency ranging from 1.5% (for a ka = 0.06) to 94% (for a ka = 0.39).

This paper presents a compact end-fire array with a high realized gain, featuring a simple planar design that offers a cost-effective solution for RFID applications and other uses. The synthesis strategy of this supergain array utilizes the Spherical Wave Expansion (SWE) theory. An array prototype consisting of four electrical dipoles spaced at 0.21 lambda, englobed in a total radiansphere of kr = 2.3, has been analyzed. By applying our optimization method, we demonstrate that tailoring the element feeding leads to significantly higher directivity and improved efficiency compared to conventional compact superdirective arrays. Additionally, the prototype is matched to a standard 50 ohm impedance using a printed T-match at the feeding point. The results demonstrate a notable realized gain exceeding 10 dBi.

This work proposes a circuit model for a small dipole antenna based on the spherical wave theory. The model represents the near-field stored and dissipated energies to reflect the antenna's quality factor, radiation efficiency, and input impedance. The evaluation of the component values for the model was made at a single frequency point, and excellent agreement between the model and the antenna simulation results was obtained.

An electrically small, cuboid shaped antenna has been designed and simulated in this paper. The design with an electrical size ka of 0.24 and a maximum size of./13 achieves an overall radiation efficiency of 38%, a directivity of 5.83 dBi, and a quality factor of 3.2 times the Chu limit. The design has been analyzed using spherical wave expansion (SWE) and has been compared with the excited modes of well-known reference antenna designs.

Milliliter-wave radar-based human body sensing requires for precise modeling of the backscattered field. This article presents an Iterative Physical Optics model designed for evaluating the near field backscattering of lossy dielectric target. The model is first validated by millimeter wave measurement in anechoic chamber and applied to simplified human body, in order to examine the impact that proximity to the target can have on the electromagnetic response.

This paper introduces a compact UHF RFID sensor that achieves an extended reading range through a novel super gain antenna design. The sensor employs a parasitic array of elementary dipoles, where three parasitic elements are loaded with reactive components to maximize the directivity in the endfire direction, thereby delivering super-directivity. In addition to its compact size, the design yields significant gain improvements, while the antenna input impedance is conjugate matched to the battery-assisted RFID chip for optimal power transfer. This innovative configuration paves the way for enhanced performance in RFID applications, underscoring its potential for diverse wireless sensor networks and IoT deployments where long-distance reading is of major interest.

A measurement setup is presented for antenna radiation pattern characterization in Ka- and sub-THz bands in a 20 m long anechoic chamber. A bespoke radio-frequency (RF) measurement system was developed for the Ka-band, while a custom setup, adapted from existing instrumentation, was implemented for the sub-THz band. Both systems were employed to characterize the radiation performance of two high-directivity antenna prototypes developed in the laboratory. Good agreements have been observed between measurements and simulations in the 27-32 GHz and 280-290 GHz bands.

This paper introduces a novel antenna architecture based on Low-Temperature Co-Fired Ceramic (LTCC) technology, achieving a realized gain of 9.69 dBi at 5.7 GHz. The high gain, achieved within a compact footprint, results from the effective combination of two radiating modes, i.e. a slotted patch antenna printed on a truncated substrate and a dielectric resonator antenna (DRA). Experimental measurements closely match simulation results, confirming both the performance and the manufacturability of the proposed design.

This article investigates the details of Long-Term Evolution ambient backscattering communication from the backscattering device (BD) antenna perspective. In our scenario, the tag exhibits two different modes of operation for the uplink frequency band (idle) and downlink frequency band (backscattering). We show that in backscattering mode the BD does not need to be matched to the antenna impedance alleviating the efforts in antenna design compared to other frequency-agile antenna systems. A miniature antenna is designed seeking to optimize its radiation efficiency.

In this paper, the design and optimization of a circularly polarized antenna based on two crossed dipoles in phase quadrature for Global Navigation Satellite System (GNSS) wide band application has been investigated. The proposed design is single fed and relies on parasitic structures to achieve wide band coverage on the GPS standard bands L1 (1559-1610 MHz) and L5 (1164-1189 MHz). Full-wave simulations have been used to compute the radiation properties and the impedance of the antenna. A prototype was manufactured, and good agreement has been observed between the simulated results and measurement for both radiation pattern and reflection coefficient.The antenna achieves a -10 dB impedance bandwidth of $56.97\%$ covering the band 1164-1610 MHz, and an axial ratio that covers the L5 band ranging between 7 dB and 2.8 dB from 1.164 GHz to 1.3 GHz while maintaining a value below 2.7 dB across the entire L1 band. The antenna occupies a volume of $\,99\, \,\times\,99\, \times 50$ mm3. It has been tested in real conditions during the 23rd French National Microwave Days (JNM) student competition. A GNSS signal receiver has been connected to the antenna. The antenna has been evaluated based on the number of connections it could achieve over a duration of 30 s.

This article presents a strategy of miniaturization for electrically small Inverted-F Antenna (IFA) using Magneto Dielectric Material (MDM). The loading strategy is studied in order to strengthen the interaction of antenna's magnetic and electric near fields with the properties of the material. Following this strategy, a tradeoff is established with electrical size of the antenna and its radiation properties.

This article proposes a new model based on the spherical wave expansion (SWE) theory to synthesize efficient and highly directive endfire arrays of electric dipoles, which are known to be suitable for superdirective purposes. When extremely compact dimensions are considered, the high-order spherical harmonics required to construct a directive radiation pattern become mainly dissipative, causing radiation efficiency drops. To account for the impact of the losses, the proposed synthesis procedure integrates a specific formulation of the modal dissipation factor $({\delta }_{n})$ associated with the excited spherical harmonics. The excitation coefficients, results of the optimization, demonstrate improved efficiency for endfire arrays of two, three, and four elements if compared to a superdirective solution. These results are scalable to a higher number of elements as well as other element distributions and types of radiators. In addition to the numerical validation through full-wave electromagnetic simulations, a prototype based on a four-element array is designed and experimentally characterized to validate the proposed analysis. The experimental results show a maximum gain of 9.8 dBi achieved for a radiansphere of 1.75, which is in good agreement with the theory and simulation results.

We present a differential wireless passive sensor based on a miniature antenna associated with a MEMS capacitive pressure sensor. In this configuration, a change in the external pressure results in a shift of the antenna resonance frequency and, thus, a variation in the antenna Radar Cross Section (RCS) detectable from a distance of a few meters. The MEMS and the antenna are modelled and simulated, and a co-design procedure is developed to optimize their performance. The MEMS are fabricated on a 200-mm technological platform and characterized. A specific setup was conceived to characterize the antenna sensor as a function of pressure in an anechoic chamber.

This paper introduces a compact three-bent-dipole end-fire array operating at 916 MHz, exhibiting remarkably high realized gain in relation to its electrical size. The optimization process focuses on feeding the array elements to maximize directive properties in a chosen direction while upholding high efficiency as a constraint. Complex excitation coefficients are subsequently transformed into equivalent impedance loads for implementing a parasitic array. Two antennas are designed, fabricated, and characterized. For the first prototype (loaded), the central element is actively fed, and the external elements are loaded with reactive components. A second prototype (load-less) is designed to incorporate the required complex excitations by adjusting the imaginary parts of the dipoles through modifications in their vertical length. Both array versions are matched with a T-match on the active elements. Experimental results from differentially-fed fabricated prototypes reveal outstanding agreement between simulated and measured radiation properties. In the differential mode, a peak realized gain of 8.9 dBi at 910 MHz is achieved for the parasitic loaded array, and 8.3 dBi at 911 MHz for the load-less array.