Abstract: In this work, we present a simple design of a compact and miniaturized wideband bandpass filter (BPF) based on substrate integrated waveguide (SIW) and microstrip line. Through the order extension, the filtering effect and the order of the Chebyshev response of the designed BPF can be indirectly controlled by preserving square notches (SNs) on the SIW. By introducing one or two SNs in the SIW structure, the resonance frequencies of different modes can be controlled, thus achieving dual- and tri-mode BPFs with wideband and low insert loss. The working principle of the designed BPFs was illustrated by modal analysis, field distribution, and equivalent circuit theory. Based on this, the dual- and tri-mode BPFs with center frequencies of 6.8 and 7 GHz were designed and demonstrated numerically. Further experimental results indicate that the proposed tri-mode BPF has low insertion loss (0.25 dB), compact size (0.27λg2), and wideband bandwidth (60%). In addition, the tri-mode BPF achieves a broadband out-of-band rejection of 1.5f0 (f0 is the center resonance frequency) below the −10 dB level, making it highly promising for various applications in related fields.

Abstract: In this communication, we present a new design for a folded reflectarray antenna (FRA) inspired by the Risley prism antenna. This innovative FRA enables circularly polarized (CP) beam scanning in both azimuth and elevation planes with low losses. The proposed CPFRA comprises of a top layer with a circularly polarized selective surface (CPSS), a bottom layer with an RA, and a planar CP antenna serving as the feed antenna. The CPSS has the capability to fully reflect the incident waves of right-hand circular polarization (RHCP) while transmitting those of left-hand circular polarization (LHCP). By mechanically rotating both the CPSS and RA, this antenna enables beam scanning in the elevation plane from 0° to 45°, as well as in the azimuth plane from 0° to 360°. At a frequency of 10 GHz, measurements show that this antenna achieves an impressive maximum gain of 21.5 dBic, corresponding to an aperture efficiency (AE) of 31.2%. This antenna offers several advantages, including its compact structure, low profile, low cost, and high gain performance. As such, it proves suitable for applications where space is limited, such as satellite communication and vehicle communication.

Abstract: This letter presents a new method for broadband attenuator design, which uses dual-branch resistors and microstrip-line-loaded slotline structure. Resistors are loaded on slotline to achieve attenuation property, and dual-branch configuration and implantable microstrip line in each branch are proposed to improve attenuation slope within broadband when the attenuation amount becomes large. To validate the proposed design method, an 11-stage attenuator is designed and measured, which has a minimum insertion loss of 1.92 dB, a dynamic attenuation range of 20 dB, and a return loss of better than 8.5 dB, within the bandwidth of 2–5 GHz. Moreover, the effect of parasitic inductance in used resistors is also investigated to clarify the attenuation fluctuation of the measured attenuator.

Abstract: This study uses annular circular rings to create multi-band applications using crescent-shaped patch antennas. It is designed to be made up of five circular, annular rings nested inside of each other. Three annular rings are positioned and merged on top of the larger rings, with two annular rings set along the bottom of the feed line. The factors that set them apart, such as bandwidths, radiation patterns, gain, impedance, and return loss (RL), are analysed. The outcomes show how compact the multi-band annular ring antenna is. The proposed circular annular ring antenna has return losses of −33 dB and operates at two frequencies: 3.1 GHz and 9.3 GHz. This design is modelled and simulated using ANSYS HFSS. The outcomes of the simulation and the tests agree quite well. The X band and WLAN resonant bands have bandwidth capacities of 500 and 4300 MHz, respectively. Additionally, the circular annular ring antenna design is advantageous for most services at these operating bands.

Abstract: This work offers an optimized design of a reconfigurable microstrip patch antenna coupled with RF MEMS shunt capacitor switches to improve performance at 3.4 GHz. The antenna, with dimensions of $40 \times 45 \times 1.6 \mathrm{~mm}$, was constructed and simulated using the HFSS (High-Frequency Structural Simulator). By utilizing RF MEMS technology to achieve frequency agility in HFSS, the antenna allows for dynamic reconfiguration of its operating frequency. Comparing the simulation results to prior designs, a significant improvement in return loss of $-40 \mathrm{~dB}$ and gain of 4.1dBi, as well as enhanced impedance matching and frequency coverage, is observed. These results underscore the potential of the proposed approach for multiband applications in contemporary wireless communication systems. Future optimization and application-specific modifications of the optimized antenna design are highly promising. Subsequent investigations may focus on optimizing design parameters to achieve superior performance measures such as reduced size, radiation efficiency, and bandwidth. Additionally, the antenna's reconfigurable feature enables its use in various applications, including cognitive radio, satellite communications, and Internet of Things (IoT) devices. Exploring these possibilities could drive the evolution of wireless communication technology to meet the changing requirements of diverse applications.

Abstract: In this work, a small planar microwave sensor based on a band-stop filter is proposed for measuring the relative permittivity of the materials. The operation frequency of the presented sensor is 2.24 GHz. It is composed of a microstrip line and an M-shaped slot as the host and sensing area respectively. This structure has been fabricated with printed circuit board (PCB) technology on the RO4003c. The sensing performance has been verified through the fabrication and measurement of a prototype to characterize the solid and the liquid samples. The correlation between the resonance frequency and relative permittivity is almost linear. The resonant frequency variation of the proposed sensor (2.24 GHz to 1.97 GHz) is proportional to dielectric constant of samples under test which is in a wide from 2.43 to 80 This sensor illustrates superior performances in comparison with similar structures in the fields of broad-range permittivity for Material under test (MUT) and the size of the transducer. The experimental results for solid-liquid materials indicate that the normalized sensitivity is 1.43% - 0.95% which is better than most similar structures. The size of the proto-type sensor (7mm $\times 14$ mm $\times 0.508$ mm) is smaller than those reported in the literature.

Abstract: A cascade Class-F power amplifier (PA) is proposed for smart parking solutions. Input and output matching network are designed and analyzed using Microstrip line (MSL), suspended shielded lines (SSL) and shielded inverted line (SIL). Class-F PA design is based on the harmonic termination of an even and odd harmonic for improved efficiency. Class-F PA produces non-overlapping drain current of half sinusoidal form and voltage waveforms of half square form to reduce power dissipation. Suspended shielded (SSL) and shielded inverted lines (SIL) have low attenuation, low propagation loss, low insertion loss (S11) and low dielectric constant as compared to Microstrip line (MSL). The main objective of the work is to compare the transmission line like MSL, SSL and SIL for better performance of Class-F PA in terms of high efficiency and bandwidth. Design is based on even and odd harmonic termination to get non-overlapping current and voltage waveform. Simulation is performed using advanced design system (ADS) software using gallium nitride high electron mobility transistor (GaN HEMT) device from CREE. The results show improved power added efficiency (PAE) of 80 to 85%, gain of 15dB and output power (Pout) of 44dBm with suspended shielded (SSL) and shielded inverted (SIL) line as compared to Microstrip line (MSL) at 0 to 3GHz frequency.

Abstract: In recent years, wireless communications have evolved significantly, and many mobile devices have reduced in size. The antennas used in mobile terminals must be lowered in size to fulfil the downsizing standards. Planar antennas, like microstrip and printed antennas, have a low profile, compact size, and conformability to mounting hosts, making them particularly desirable candidates for achieving these needs. Additionally, planar antennas are also being used in communication devices for 2.4 GHz (2400 – 2484 MHz) and 5.2 GHz wireless local area network (WLAN) systems (5150). In wireless applications, an antenna is a crucial component. At the transmitter, it transforms electrical signals into RF signals, and at the receiver, it converts RF signals to electrical signals. The patch inside the antenna is made of a conducting material such as Cu (Copper) or Au (Gold), and it can be rectangular, round, triangular, or elliptical. Two unique designs of microstrip planar antennas with an operating frequency of 5.2 GHz having S11 parameters as -16.0 dB and -15.7 dB have been offered and their performance has been studied in this research article.

Abstract: Microwave devices using printed gap waveguide technology, such as inverted microstrip gap waveguide (IMGW), are essential for millimeter-wave applications. In this article, a new wideband monopulse comparator composed of four wideband rat-race hybrid couplers is proposed. The complete theory behind the couplers is presented using even-odd mode analysis. To demonstrate the potential of the proposed monopulse comparator, the structure has been designed, fabricated, and measured. Measured results show a bandwidth of nearly 50% for a reflection coefficient of better than 10 dB, an isolation of better than 27 dB between the ports. There is an imbalance of −1.25/+0.25 dB and 2.5° in magnitude and phase at the output ports, respectively. The measured results show that the phase and power dividing performance between output ports is satisfactory across the entire frequency range.

Abstract: 5/6G is anticipated to address challenges such as low data speed and high latency in current cellular networks, particularly as the number of users overwhelms 4G and LTE capabilities. This paper proposes a microstrip patch antenna array comprising six radiating patches and utilizing a microstrip line feeding technique to facilitate the compact design crucial for 5G implementation. ROGER 3003, chosen for its advanced and environmentally friendly features, serves as the dielectric material, ensuring suitability for 5G and B5G applications. The designed antenna, evaluated at a resonating frequency of 28.8 GHz with a −10 dB impedance bandwidth of 1 GHz, offers a high gain of 9.19 dBi. Its compact array, cost-effectiveness, and broad impedance and radiation coverage position it as a viable candidate for 5G and future communication applications.

Abstract: Nanoscale magnetic resonance imaging (NanoMRI) is an active area of applied research with potential applications in structural biology and quantum engineering. The success of this technological vision hinges on improving the instrument's sensitivity and functionality. A particular challenge is the optimization of the magnetic field gradient required for spatial encoding and of the radio frequency field used for spin control, in analogy to the components used in clinical MRI. In this work, we present the fabrication and characterization of a magnet-in-microstrip device that yields a compact form factor for both elements. We find that our design leads to a number of advantages, among them a 4-fold increase of the magnetic field gradient compared to those achieved with traditional fabrication methods. Our results can be useful for boosting the efficiency of a variety of different experimental arrangements and detection principles in the field of NanoMRI.

Abstract: A co-linearly polarized wideband microstrip antenna with a single shared patch feeding by two parallel L-probes is proposed in this letter. The shared patch introduces a new coupling path for the L-probes. The coupling coefficients of the two L-probes, as well as the L-probe and the patch, are quantitatively derived based on the coupled resonators theory. It is proved that by adjusting the geometries and dimensions of the two L-probes and the patch, a natural wideband high isolation can be obtained. A demonstration example is designed and measured to validate the feasibility of the proposed scheme. The results show that the proposed antenna can achieve impedance matching of −10 dB and high isolation of 20 dB in the frequency range from 3.2 GHz to 4 GHz. Besides, the measured efficiency ranges from 91% to 99% with an average realized gain of 7.4 dB. Furthermore, another example with a lower height is also designed to justify the practical usefulness, showing 19.8% decoupling bandwidth.

Abstract: This study compares microstrip antennas, microstrip antenna arrays, and slotted microstrip antenna arrays for 5G communication. Emphasizing the compact size and compatibility with 5G devices, microstrip antennas are explored. The research delves into the specialized designs of slotted microstrip arrays for improved signal quality, considering factors like gain and radiation patterns. The study highlights the advantages of antenna arrays over individual microstrip antennas and suggests areas for future research. Overall, the research contributes to enhancing 5G systems, emphasizing the benefits of these antennas for faster, more capable, and dependable communication.

Abstract: A four-layer antenna array is presented for lower microwave frequency band. The Evanescent coupling mode is applied for reduction of distance between adjacent resonators. The electrical parameters are obtained by 3D computer simulation. It was confirmed that novel design provides higher characteristics together with effective size reduction for circularly polarized plane antenna array at lower frequency band 2.8 GHz.

Abstract: Abstract In this paper, two second-order electronically tunable bandpass filters are presented. The filters are implemented in microstrip technology using barium–strontium–titanate (BST) varactors and digitally tunable capacitors (DTC) for tuning the frequency response of the bandpass filters. The filter realized using BST varactors has a 35% tuning range from 900 MHz to 1.275 GHz with an insertion loss variation from 3.1 to 2.6 dB. The absolute bandwidth is nearly constant over the entire tuning range, varying from 64 to 72 MHz (around ±5% variation). The filter realized using DTCs also has a 36% tuning range from 850 MHz to 1.225 GHz with an insertion loss variation from 3.1 to 1.5 dB. The absolute bandwidth is constant over the tuning range, varying from 88 to 98 MHz (around ±5% variation). The bandpass filters are tuned using a single control signal. The tunable bandpass filters are proposed for use in reconfigurable radios.

Abstract: Abstract The electromagnetic compatibility analysis of RF circuitry is essential due to the adverse effects on sensitive components. Two metamaterial unit cells with slow‐wave properties are presented for cross‐talk reduction in transmission lines. The analytical expressions for computing equivalent lumped elements of the lines are then provided. The dispersion diagram is obtained from the parameters extracted from the measurement. A microstrip as the generator line and five identical CRLH unit cells as the receptor line are then used and a significant reduction in cross‐talk is observed in comparison to conventional lines. A non‐uniform transmission line with two different CRLH unit cells as the receptor line is then employed and found effective in further cross‐talk reduction between the lines. The lengths of the lines and numbers of cells are kept the same in all lines for comparison. The simulated results are validated by measurements.

Abstract: The present study outlines the development and execution of a unique, condensed, ultrawideband microstrip patch antenna through the utilization of CST Microwave Studio software. The aforementioned antenna, with dimensions of 15 × 18.30 × 1.6 mm3, has been designed with a particular focus on its utility in the context of satellite communication applications. The substrate utilized in its construction is Rogers RT5880 material. The antenna exhibits a noteworthy characteristic of achieving a wide range of bandwidth coverage, estimated to be around 140.39%. The system exhibits versatility in fulfilling diverse communication needs as it functions through three distinct frequency bands, specifically the C, X, and Ku bands. The antenna demonstrates exceptional transmission capabilities, achieving maximum efficiency of 93%. Remarkably, the antenna demonstrates a noteworthy gain of 4.8 dBi, indicating its exceptional ability to amplify signals, despite its diminutive size. The device's expansive frequency range, condensed physical dimensions, and noteworthy amplification render it appropriate for a diverse array of wireless implementations. Given these characteristics, the aforementioned antenna presents itself as a highly appropriate option for applications in satellite communication.

Abstract: This work demystifies the role that packaging boundary conditions (both physically and electromagnetically) can play in a nematic liquid crystal (NLC)-based inverted microstrip (IMS) phase shifter device operating at the 60 GHz band (from 54 GHz to 66 GHz). Most notably, the air box radiating boundary and perfect electric conductor (PEC) enclosing boundary are numerically examined and compared statistically for convergence, scattering parameters, and phase-shift-to-insertion-loss ratio, i.e., figure-of-merit (FoM). Notably, the simulated phase tunability of the radiating air box boundary structure is 8.26°/cm higher than that of the encased (enclosed) PEC boundary structure at 60 GHz. However, the maximum insertion loss of the encased PEC structure is 0.47 dB smaller compared to that of the radiant air box boundary structure. This results in an FoM increase of 29.26°/dB at the enclosed PEC limit (relative to the less-than-optimal airbox radiation limit). Arguably, the NLC-filled IMS phase shifter device packaging with metals fully enclosed (in addition to the default ground plane) enhances the symmetry of the structure, both in the geometry and the materials system. In electromagnetic parlance, it contributes to a more homogenously distributed electric field and a more stable monomodal transmission environment with mitigated radiation and noise. Practically, the addition of the enclosure to the well-established NLC-IMS planar fabrication techniques provides a feasible manufacturing (assembling) solution to acquire the reasonably comparable performance advantage exhibited by non-planar structures, e.g., a fully enclosed strip line and rectangular coaxial line, which are technically demanding to manufacture with NLC.

Abstract: This paper presents the design of the microstrip series-fed antenna array for 60GHz millimeter-wave radar applications. It utilizes a Dolphe-Chebyshev distribution to reduce the side lobe level (SLL) and adopts a grounded coplanar waveguide (GCPW) as feeding structure. The designed antenna array is fabricated and tested, and the measure results align well with the simulation results. Building upon this, a 20-element antenna array is designed. Simulation results indicate that the −10dB impedance bandwidth is 880MHz, SLL is less than −17dB, and the half-power beamwidth (HPBW) is 4.6°. The demonstrated high gain, narrow HPBW, and low SLL make this antenna suitable for 60GHz narrow beam millimeter-wave radar applications.

Abstract: In this paper a comprehensive comparative study of three distinct microstrip patch antenna (MPA) designs, each optimized for the sub-6 GHz applications, is presented. The initial design phase utilized a Rogers RT 5880 substrate with a permittivity (εr1) of 2.2 and a thickness(H1) of 1.42 mm. The proposed model achieved a resonance band ranging from 4.8 to 7 GHz, with a bandwidth of 2.2 GHz and a return loss (S11) of -20 dB. Subsequent enhancements involved integrating a Barium Strontium Titanate (BST) thin film (εr2 = 250, thickness(H2) = 0.005 mm), effectively shifting the operational band to 3.5-5.3 GHz. The final design iteration, which incorporated both BST and a Defective Ground Structure (DGS), represented a substantial advancement, achieving wideband operation from 1.8 to 6 GHz, expanding the bandwidth to 4.2 GHz, and improving the S11 to -25 dB. This integration also resulted in a compact antenna size of 30 x 26.5 x 1.42 mm³. These findings underscore the synergistic impact of BST and DGS in enhancing MPA design, marking a significant progression in antenna technology, vital for a range of wireless communication.

Abstract: This study introduces a microstrip patch antenna array with a defective ground structure, arranged in a 4X4 square configuration. The antenna array is specifically developed for wireless communication applications within the frequency range of 4 GHz to 8 GHz. The resonant frequency of the antenna is measured to be 5.82 GHz, resulting in a maximum gain of 2.7218 dBi. Additionally, the antenna exhibits a significant bandwidth of 881 MHz. The design demonstrates enhanced performance by using the concepts of a λ/4 transformer for square patch antennas. The antenna is constructed utilising a FR-4 Epoxy substrate, and it is subjected to thorough testing and comparison with a 4X4 rectangular microstrip patch antenna. The results indicate that there are extensive potential uses for these discoveries in the field of new communication technology.

Abstract: In this article, a novel in-band and out-of-band low radar cross section (RCS) circularly polarized (CP) antenna array based on a hybrid mechanism of absorption and phase cancellation is proposed. The antenna scattering-reduction unit is a frequency-selective absorber-polarization converter (FSAPC) unit comprising a resistive metasurface (RM) unit, four frequency-selective surface (FSS) units, and four polarization-conversion metasurface (PCM) units arranged in cascade. The RM employs a parallel resonant structure comprising metal rings and parallel lines to create an in-band transmission window for the radiation while simultaneously absorbing the out-of-band electromagnetic waves. The modified PCM configuration is arranged in a diagonal configuration with cutting round arcs and serves two distinct functions. Primarily, it converts the co-polarized component of in-band incidence into a cross-polarized one. Second, the decomposition of the electric field enables the metal square to facilitate the conversion of the antenna-radiated wave from linear to circular polarization. Furthermore, the implementation of a counterclockwise feeding network is expected to enhance the circular-polarization performance. To verify the functional properties of the FSAPC structure, the properties of the constituent units and the FSAPC unit are elucidated and investigated in two dimensions: field and circuit, which are done based on the principles of double-port equivalent circuit and coupler theory. Furthermore, the slot antenna array is directly integrated with the metal reflector of the FSAPC in a chessboard configuration, thereby enabling the realization of the desired radiation performance. The simulation and measurement results demonstrate that the FSAPC-based antenna array is capable of achieving good left-handed CP radiation characteristics and also adept at reducing the RCS by over 10 dB across the 5.73–17.5-GHz range. The results demonstrate that the antenna array is capable of simultaneously achieving both stealth and radiation functions, rendering it an apt candidate for integration into modern weapon platforms.

Abstract: It goes without saying that Antenna design is decisive for wireless communication technology progression. As we know that Microstrip antennas, widespread for microwave frequencies, have been considered in this paper to increase their gain and bandwidth. Experiments which has been done show that raising substrate height and patch length can increase the gain and bandwidth of a rectangular microstrip patch antenna. The antenna's design and progress were made possible using 3D printing technology. The antenna's reliability and appropriateness for wireless communication technologies could momentously profit from its use. Antenna design is crucial to the advancement of wireless communication technology. The design of an antenna can significantly affect how well a wireless communication link performs. Microstrip antennas, occasionally denoted to as printed antennas, are among the many assortments of antennas that have become progressively standard due to their use in microwave frequencies. Researchers have looked into ways to increase the microstrip or patch antennas' gain and bandwidth. In order to upsurge the gain and bandwidth of a rectangular microstrip patch antenna, that is the main prominence of this work. Trials have shown that the rectangular microstrip patch antenna's bandwidth and gain may be efficaciously amplified by floating both the substrate height and the patch length. The design and development of the microstrip antenna was the first step in the multi-stage research process. Particularly, the antenna's concluding structure was made possible by the use of 3D printing technology. The printed antenna was then put through a thorough testing process using a Vector Network Analyzer at an antenna laboratory. The outcome of this extensive examination and testing shows that a microstrip antenna optimized for microwave frequencies has been developed, and it is very suited and reliable. The field of wireless communication technologies could benefit greatly from the use of this antenna.

Abstract: A compact simple structure bandpass filter based on terminated three coupled line structures with high selectivity is introduced through odd and even-mode analysis. The proposed filter consists of three coupled lines loaded by open and short circuit stubs. The parallel-coupled lines structure is used to obtain high selectivity with transmission zeros near the passband. Meanwhile, simultaneously tuning on bandwidth and center frequency are introduced by coupled line. One type of bandpass filter based on terminated coupled line structure is theoretically analyzed, simulated, and measured. The stepped impedance structures at the input and output ports have been used to improve the attenuation level at the stopband region and create the multiple attenuation poles. The center frequency of 1.3 GHz, the fractional bandwidth (FBW) of about 65%, the low insertion loss of 0.25 dB, and the high return loss of 30 dB are obtained. Also, a flat group delay lower than 1.4 ns is achieved. Experimental and simulated results are presented, which are in good agreement.

Abstract: A single-layer low-profile dual-band patch antenna is proposed in this letter. A Π-shaped slot is engraved on the radiating patch, separating it into a main patch and a parasitic patch to achieve the dual-band characteristics. The purpose of loading five shorting pins between the two vertical slots on the main patch is to turn down the two frequencies, which can generate TM01 mode and TM11 mode. To improve the impedance matching in the lower band and broaden the dual-band bandwidth, four shorting pins are placed on the edge of the long side of the parasitic patch, which can excite the TM10 mode. The combination of the TM01, TM11, and TM10 modes achieves the 3.45–3.7 GHz and 4.7–5.33 GHz dual band. Manufacturing and measuring a prototype. The results of the measurements indicate that the antenna achieves a dual-band with reflection coefficient less than −6 dB, which are 3.5–3.75 GHz (250 MHz, 7.0%) and 4.73–5.41 GHz (680 MHz, 13.4%) with peak gains of 6.23 and 5.06 dB in the low and high bands, respectively. The average total efficiencies in the dual bands are 64.2% and 77.3%, respectively.