A T-matched meander line passive Radio Frequency Identification (RFID) tag is designed for near-field Ultra High Frequency (UHF) communication. A new method is introduced to effectively limit the read range of the UHF RFID tag, ensuring its functionality within near field region. The proposed RFID tag antenna, with overall dimensions of 43 x 10 x 1.6 mm³, demonstrates a strong electric and magnetic field in the near-field region. The tag incorporates the Higgs 4 IC chip from Alien Technology, which provides enhanced sensitivity and a rapid read rate for storing unique identifiers. The designed tag is platform-tolerant. Comprehensive read range measurements were conducted for various common mountable platforms. Key performance metrics, including impedance, radiation pattern, bandwidth, and the impact of ground size on gain, were thoroughly analyzed. Experimental results confirm that the proposed tag exhibits robust identification capabilities in the near-field zone, making it well-suited for item-level tagging applications.

In this paper, a low profile, ultrathin, wide passband, polarization insensitive, wide angular stable frequency selective surface (FSS) is proposed. The structure is realized on a two-sided copper on Roger’s RT 5880 substrate with 0.51 mm thickness. The top layer design consists of a combination of slotted circle with quad arcs along with cross bars at the center with diagonal tilts at the corner. On the bottom layer, an elliptical-shaped patch is placed at the center. This elliptical patch at the bottom layer of FSS helps to realize the wide pass-band response. The pass-band bandwidth ranges from 8.45 to 9.45 GHz centered at 8.96 GHz. The proposed FSS is polarization insensitive. The structure provides angular stability till 45° of incident angle for Transverse Electric (TE) and Transverse Magnetic (TM) modes of operation. The prototype of FSS is fabricated with an array of 10 x 10 unit cells. The simulated and measured results are found to be in good agreement.

A combline microwave cavity filter has been developed to generate the 2.856 GHz radio frequency (RF) tone to be used as the master reference of SPARC_LAB electron linac facility at the Frascati National Laboratories of the National Institute for Nuclear Physics (LNF-INFN). The filter must select the 36th harmonic from a frequency comb with a repetition frequency of 79.33MHz and reject the other harmonics. The comb is generated by the electric conversion of the laser pulse train from the oscillator of the photocathode laser. Since a filter for this very specific application is off-the-shelf, it was designed, manufactured, and tested in-house at LNF-INFN. The measured insertion loss at the center frequency is 2.2 dB, the bandwidth is 30MHz (percentage fractional bandwidth is 1.1 %). This narrow bandwidth is required to ensure effective rejection (insertion loss > 65 dB) of adjacent harmonics in the frequency comb, specifically at frequencies of 2.77633 GHz and 2.93533 GHz. The purpose of filtering is to ensure that the tone, distributed in the low-level RF system, remains clean and can be used to synchronize the most crucial machine subsystems, such as RF power units, accelerating cavities, diagnostic systems, and lasers.

The probability of antenna array failure or malfunctioning cannot be ruled out, and hardware replacement of faulty elements is not always a viable solution. Therefore, academic and industrial interest in self-healing phased arrays are on the rise. In this work, the phase-only genetic algorithm (GA) optimization flow for the radiation pattern correction of a 4 × 4 phase faulty planar antenna array is proposed. Initially, a reference array pattern at the desired scan angle is generated. Then random phase faults are introduced across the 1 × 4 antenna elements in any one of 4 sub-arrays to produce maximum distortion in the reference radiation pattern of 4 × 4 planar array. The proposed GA re-computes the new excitation weights for the remaining non-faulty 3 sub-arrays to correct the overall radiation pattern of 4 × 4 array. This is achieved by calculating the array output power for reference and GA computed weights. The GA corrected patterns fairly follow the desired array patterns in terms of peak gain and reducing sidelobe levels for the desired scan angle. The efficiency of the optimized radiation patterns was evaluated in full-wave HFSS model and measurements validation. In this way, maintenance cost can be reduced with recovery of acceptable level of radiation pattern using software instead of physically replacing faulty antenna elements in the array.

This paper proposes a dual-band metamaterial microwave absorber operating at 2.5 GHz and 5.8 GHz. The absorber consists of a ring and a circular patch with slits resonator structures printed on a FR4 dielectric substrate backed by a ground layer. The main advantage of the absorber lies in its design flexibility in which each absorption band is independent and can be individually tuned by changing the dimensions of each resonator structure. The absorber unit cell is simulated and parametrically optimized using Computer Simulation Technology (CST) software. The absorption mechanism is analyzed through surface current analysis. The absorber prototype, with dimensions of 200 × 200 × 1.6 mm3 and consisting of an array of 7 × 7 unit cells, is fabricated and experimentally investigated using antennas in free-space measurement. The absorber exhibits over 97% absorption at both resonance frequencies. Furthermore, the absorber is demonstrated to be applicable in sensing applications for dielectric constant determination. With its design simplicity, wide-angle receptive, and polarization insensitive behavior, it is envisaged that the proposed absorber will find practical use in absorbing and sensing applications.

This paper investigates on the rarely studied negative group delay (NGD) RF circuit with innovative stop-band (SB) behavior. In difference with the classical filter, the SB-NGD function is identified in function of frequency bands where the group delay (GD) presents negative sign. The ideal diagram specifying the SB-NGD function is introduced by indicating all the appropriate parameters. The S-parameter analytical model of the circuit is established. The SB-NGD analysis is developed. The main specifications of the SB-NGD circuit are expressed in function of its constituting components. Then, the design synthesis equations enabling to determine the SB-NGD circuit in function of the desired specifications as the center frequency and GD are built up. To illustrate concretely the feasibility of the SB-NGD function, a circuit proof-of-concept composed of LC-series network is theoretically analyzed. A parametric analysis on the SB circuit elements is accomplished to appraise the influence of each element on the SB-NGD specifications. To validate the unfamiliar SB-NGD theory, a prototype is fabricated and tested. The GD measured response of the considered circuit is compared by simulations and analytical calculations. SB-NGD responses showing a good agreement between the calculation and simulation are obtained with a 15 MHz center frequency, 44 ns GD and 3 MHz bandwidth.

This paper develops new integral formulas intended for detailed studies of electromagnetics normal modes in spherical and spherical annular cavities.

The work carried out the calculation and synthesis of antenna arrays used in radio-electronic complexes on unmanned aerial vehicles. The analytical model is designed to find asymptotic estimates of the polarization components of the electric field of the grating in the far zone of the carrier surface; the results obtained with its use are the initial data for constructing a technique for the numerical solution of a boundary value problem for a grating on a carrier surface in the CST MWS electrodynamic simulation environment. The synthesis of gratings with the maximum achievable coefficient of directional action is carried out with the control of radiation patterns at a given set of angles. A two-mirror antenna system has been calculated. It is shown that with an increase in the number of re-reflections taken into account, the convergence of the result for the calculated characteristics of the antenna is observed. To test the proposed method, the same antenna was calculated using the integral equation method. The comparison showed a high degree of agreement between the results obtained by two different methods. The results of the simulation based on a software algorithm designed to quantify the input matching at the input of a multichannel frequency-scanning antenna array power divider are presented. It was found that when performing wide-angle scanning in a relative frequency band of more than a few percent, the disadvantage of the known method for eliminating the normal effect is a sharp deterioration in matching in the lower and upper frequencies of the operating range. A new method is proposed based on an automated iterative process of optimizing the divider geometry, which makes it possible to obtain an acceptable match over the entire operating frequency band. The feasibility of switching from a serial power divider construction scheme to a series-parallel scheme is analyzed for wide-angle scanning in a relative frequency band of about 5%.

In this paper, we propose three kinds of substrate-integrated waveguide (SIWs) based chamfered bend power divider junctions provide equal power distribution to all output ports while maintaining high isolation and operating in the 54 GHz to 60 GHz frequency band. The advantages of the SIW technology are ease of design, fabrication and low form and full integration with planar printed circuits. In this case, the concept of the SIW H-plane power divider is implemented using a rigorous two-dimensional quick finite element method (2D-QFEM) programmed by MATLAB software. The numerical performance of this method is the Quick simulation time for using the mesh with Delaunay regularization in two dimensions, if we increase the mesh the FEM gives better results. This paper presents the transmission coefficient, return loss and the electric field distribution. The results obtained from QFEM were compared with those provided by HFSS for validation. When using the discretization with the Delaunay procedure only in two dimensions, we notice that the calculated simulation time decreases with good precision.

A compact high-isolation diversity and circular polarized (CP) multiple-input multiple-output (MIMO) fabric antenna for 2.4 GHz ISM band applications is presented. A metamaterial (MTM)-inspired radiating element is used for the miniaturization of the presented fabric antenna. The proposed antenna is fabricated on a denim substrate and has a dimension of 58 mm x 23 mm x 1.6 mm. The circular polarization is achieved by trimming the two diagonal corners of the radiating elements. A defected ground structure (DGS) comprising two U-slots is placed underneath each radiator to increase the bandwidth of the presented antenna. The isolation characteristics between the two antenna elements are increased by 20 dB by cutting a slit in a ground plane. The proposed CP-MIMO antenna incorporates an artificial magnetic conductor (AMC) layer to limit backward radiation towards the human body and hence enhances the gain. This antenna has been created on a denim substrate with permittivity εr =1.6 and 1.6 mm thickness. The proposed antenna offers a fractional bandwidth of 6.6 % (2.38-2.54 GHz), and an impedance bandwidth about 160 MHz. The antenna has a peak gain of 2.5 dBi without AMC and 4.5 dBi with AMC. To validate the simulation results, a prototype for the proposed antenna has been fabricated and experimentally characterized. Due to its small size, low specific absorption rate (SAR), ease of integration, and robustness, this antenna is a good option for wireless body area network (WBAN) applications.