In this paper, a balanced bandpass filter (BPF) based on dual-mode substrate integrated waveguide (SIW) is proposed. The degenerate dual-mode characteristic in the SIW cavity is utilized to construct a high-order filtering response, contributing to miniaturization and the improvement of frequency selectivity. Meanwhile, benefiting from the balanced feeding structure and the symmetry of the SIW, the balanced BPF achieves excellent differential-mode (DM) transmission while suppressing the excitation of common-mode (CM) signals. For the purpose of demonstrating the theoretical design, the proposed balanced BPF with a center frequency of 8.23 GHz was fabricated and measured. The simulated and measured results are in good agreement. The design realizes a filtering response with two transmission zeros, and its CM suppression is higher than 41 dB over an ultrawide frequency range from 6 GHz to 12 GHz.
This work reports a novel design of a proximity-fed miniaturized wideband slotted antenna operated at a higher order mode with enhanced gain. The central lambda/2 part of a 3 lambda/2 long slot is meandered so that the higher order electric field distribution throughout the slot is continuous but cancels the radiation originating from the central part. This technique reduces the side-lobes. This meander structure causes the overall length of the structure to be reduced by lambda/4, and hence, the total length of the structure becomes 1.25 lambda instead of 1.5 lambda. The higher order mode is utilized to enhance the gain of the slot antenna. The antenna shows a bidirectional radiation pattern (as no ground plane is present) with enhanced realized gain of 6dBi on one side of the bidirectional pattern and approximately 4dBi at the other side around 5.8 GHz. At the band edges, the peak gain shows 5dBi at 5.4 GHz and at 6 GHz, and it is 4.8dBi, which are not much deviated from the peak gain at the center frequency 5.8 GHz. Also, this paper proposes a novel technique of folding the central part of the 2 mm wide slot. The measured -10 dB impedance bandwidth shows 15.5% (5.3-6.2 GHz).
This paper proposes a broadband circularly polarized low radar cross section (RCS) slot array antenna incorporating a polarization conversion metasurface (PCM). First, a PCM unit comprising two dielectric substrates and three metallic patches is designed to achieve wideband cross-polarization conversion. A checkerboard PCM structure is constructed with optimized unit arrangement to obtain wideband RCS reduction. Based on this PCM, single-element and four-element array antennas are designed. Communication performance is enhanced through microstrip slot coupling feed. Simulation and physical testing validate the design's effectiveness. Simulation results indicate the array antenna exhibits impedance bandwidth from 4.61 to 9.44 GHz, peak gain of 11.82 dBi, and axial ratio bandwidth from 5.82 to 8.43 GHz. It achieves RCS reduction exceeding 10 dB across the 6.71 to 17.88 GHz band, with a relative bandwidth of 90.8%. Finally, physical fabrication and testing validated the accuracy of the simulation results. This antenna combines broadband communication capabilities with low RCS characteristics, making it suitable for scenarios requiring both electromagnetic stealth and communication performance.
This paper introduces a new approach to minimize the phase sensitivity of a reflectarray antenna by combining a genetic algorithm with pattern search optimization. The hybrid framework was proposed for selectively determining an optimized ring width and applying it to the high-sensitivity regions of the unoptimized unit-cell phase response. This adaptive ring-width optimization maintains a large phase coverage of 403 degrees and limits the phase sensitivity to 56 degrees/mm, which is 76% lower than the unoptimized configuration. A unit cell, comprising a square ring with an X-shaped cross-patch with periodicity of 0.42 lambda o, was used to verify the optimized parameters. A prototype based on 529 elements was fabricated on Rogers 5880 substrate of size 9.6 lambda o & times; 9.6 lambda o. The robustness of arrays at the array level is quantified by Monte Carlo tolerance analysis with a ring-width error of up to +/- 50 mu m in 3000 trials. The gain of the fabricated array is 28.1 dBi, aperture efficiency is 52.3%, bandwidth (1 dB) is 32%, side-lobe levels are less than -19 dB, and cross-polarization is less than -28 dB. The wideband reflectarray antenna model proposed between 10 and 16 GHz is suitable for CubeSat communications payloads.
The features of both the tag and reader in a Radio Frequency Identification (RFID) system are preferred collectively for special vehicle applications such as defense systems and traffic enforcement. This work presents a novel multifunctional antenna performing both tag and reader operations in a single unit by altering the switching status. An asymmetrical coplanar waveguide (CPW) with a meander-shaped dipole antenna is designed for a circular polarization (CP) radiation. The reader antenna is fed by a 50 ohm microstrip line, while a rectangular loop is used as a matching network for tag excitation. PIN diodes are incorporated at both feeding lines for switching between the two operations. The antenna exhibits an axial ratio bandwidth (ARBW) of (0.83-0.98) GHz for the reader function and from (0.854-0.984) GHz for the tag function. The 3 dB beamwidth and axial ratio beamwidth (ARbw) attain 135 degrees and 80 degrees, respectively, while performing as a reader, and correspondingly 135 degrees and 55 degrees, respectively, while performing as a tag. The maximum measured reading range is 6.2 m in the H-plane. The CP characteristics of the proposed design are analyzed using field component transformation and found to be in close agreement with the simulation response. A prototype of the proposed structure is fabricated, and the experimental results align with the simulated results.
This paper presents a modified X-shaped Sierpinski fractal antenna that supports Sub-6 GHz 5 G-vehicle-to-everything communication and X-band short-range vehicular sensing. However, achieving both bands in a single compact element is challenging due to high fabrication complexity, impedance-matching difficulties at Sub-6 GHz and X-band, and performance degradation under vehicular roof mounting. This requirement is addressed through a selective diagonal iteration strategy applied exclusively to the four diagonally positioned sub-squares of the Sierpinski carpet. This modification reduces the total slot count from 73 to 21, a 71% reduction compared to the standard third-iteration design and improves fabrication repeatability while preserving dual-band resonance behavior. The proposed design integrates vertical shorting pins for independent Sub-6 GHz resonance tuning and a defected ground structure for X-band impedance optimization, fabricated on a low-cost FR4 substrate within a compact $32 imes 32 imes 1.6$32 & times;32 & times;1.6 $m{m<^>3}$mm3 footprint ($0.63{\lambda _0} imes 0.63{\lambda _0}$0.63 lambda 0 & times;0.63 lambda 0 at 5.9 GHz). Experimental validation demonstrates impedance bandwidths of 5.88-6.25 GHz (${S_{11}} = - 28.80$S11=-28.80 dB) and 8.63-9.65 GHz (${S_{11}} = - 14.00$S11=-14.00 dB), with measured gain values of 4.50 dBi and 6.30 dBi, respectively. The integration of vehicle roofs has been validated across six ground plane dimensions, ranging from $100 imes 50$100 & times;50 $m{m<^>2}$mm2 to $600 imes 300$600 & times;300 $m{m<^>2}$mm2.
This paper presents a novel dual-band dual-polarized shared-aperture antenna, which, for the first time, combines a Fabry-Perot cavity antenna (FPCA) and a microstrip grid array antenna (MGAA) within a common radiating aperture. The two antennas operate at distinct frequency bands with mutually orthogonal polarizations, effectively eliminating inter-band coupling and ensuring high isolation. The MGAA serves simultaneously as the radiating element for the upper band and as the partially reflective surface (PRS) for the Fabry-Perot cavity, thereby achieving effective aperture reuse. An air layer is introduced between the grid substrate and the ground plane to form the Fabry-Perot resonant cavity, which enhances the bandwidth of the MGAA. To simultaneously satisfy the Fabry-Perot resonance condition and the MGAA impedance-matching requirement, an artificial magnetic conductor (AMC) is employed to tailor the reflection phase of the ground plane. A prototype was fabricated and measured. The measured results show -10 dB impedance bandwidths of 1.3% (5.68-5.76 GHz) and 5.9% (8.3-8.8 GHz) for the FPCA and MGAA, respectively, with peak realized gains of 13.7 and 16.6 dBi. The proposed design achieves dual-band operation, orthogonal polarization, and compact integration, providing a low-profile and high-efficiency solution suitable for dual-band wireless communication and radar systems.
Existing chipless RFID tags are constrained by limited encoding capacity and read range, motivating compact, cost-effective, high-density designs for scalable product tracking. This work presents a 1-6 GHz chipless RFID tag comprising 18 concentric square ring resonators with corner slits, fabricated on a low-cost FR-4 substrate ($70 imes 70$70 & times;70 mm, ${\varepsilon _r} = 4.4$epsilon r=4.4, $ an \delta = 0.02$tan delta=0.02). A geometric corner-slit-loading strategy yields 13 distinct resonant dips in the simulated monostatic RCS spectrum on a flat substrate. When conformally mounted on a cylindrical metallic surface, measurement of the forward transmission coefficient ${S_{21}}$S21 reveals 14 spectral dips; rigorous harmonic and artifact analysis confirms 13 as valid data states. Mutual coupling and spectral overlap are mitigated through full-wave iterative electromagnetic optimization in CST Microwave Studio. The simulated spectral and area efficiencies are 2.6 bits/GHz and 0.265 bits/cm $<^>2$ 2, respectively. In the conformal metallic environment, measured efficiencies are consistent at 2.6 bits/GHz and 0.265 bits/cm $<^>2$ 2, with minor $Q$Q-factor degradation attributable to the metallic ground plane. Benchmarking confirms this design outperforms existing conformal chipless RFID tags in bit capacity at an 83 cm far-field read distance, demonstrating suitability for real-world, scalable product tracking on metallic surfaces.
A wideband filtering phase shifter offering low phase deviation and high selectivity is proposed in this letter. The design incorporates phase-slope-compensation networks that allow flexible adjustment of the phase slope through impedance variation, effectively counteracting slope variations caused by changes in the delay line's electrical length, thereby yielding a low phase-shift error. Three pairs of coupled lines and two half-wavelength microstrip lines are employed to achieve a wide passband. Multiple transmission zeros (TZs) are introduced by the parallel coupling, source and load coupling, and quarter-wavelength short-circuit stubs, significantly improving the selectivity. Through codesign of the high-selectivity filtering structure with the phase-slope-compensation network, wide bandwidth, high selectivity, and low phase deviation can be simultaneously achieved. To demonstrate the design methodology, three prototypes were fabricated and measured, showing phase deviations in the passband of 90 +/- 3.4 degrees, 45 +/- 4.2 degrees, and 22.5 +/- 2.3 degrees, along with a rectangular coefficient of 81.2%, which validates the effectiveness of the proposed codesign approach.
In this paper, input reflectionless filtering power dividers (FPDs) for single and dual wideband operation are proposed. The basic FPD design is primarily realized by cascading a pair of step impedance resonators (SIRs) with open-ended stubs to achieve a wide band response. Further, a dual wideband response is obtained by adjusting the transmission line parameters of the single band design. To achieve reflectionless behavior in both configurations, an absorptive branch is incorporated at the source end. Additionally, a short-circuited stub is introduced in each section of FPD to further enhance reflectionless performance. To validate the proposed designs, prototypes of a wideband reflectionless FPD operating at 3.8 GHz with 18.4% 3-dB fractional bandwidth (FBW) and a dual band FPD operating at 3.1/4.1 GHz with 3-dB FBWs of 19.2% and 12.9%, respectively, with effective reflectionless performance are designed, fabricated, and measured.
A monolithically integrated on-chip THz emitter is demonstrated by directly bonding an InGaAs/InP uni-traveling-carrier photodiode (UTC-PD) onto a silicon carbide (SiC) substrate and coupling it to a series-fed microstrip patch array (MPA) antenna. The device is fabricated using an adhesive-free flip-wafer bonding technique that transfers the InGaAs/InP epitaxial layers of the UTC-PD onto the SiC platform, overcoming the lattice and thermal mismatch limitations. The SiC substrate provides both C-band optical transparency and high thermal conductivity, allowing efficient backside illumination and stable high-power operation of the UTC-PD. The UTC-PD performs optical heterodyne mixing of two laser tones to generate a tunable signal in the 0.6 THz band, which is guided and radiated through a weakly leaky traveling-wave MPA array. The eight-element MPA array produces a directional fan-beam with a mainlobe angle of 14 degrees, exhibiting a passive beam squint of about 10 degrees as the beat frequency varies from 0.60 to 0.62 THz. The total radiated power at 0.6 THz is estimated to be 22 & micro;W at a photocurrent of 15 mA under a -1 V bias. This monolithic SiC-based integration enables on-chip optical-to-THz conversion and free-space THz radiation, offering a compact platform for beam-scannable THz transmitters in next-generation photonic THz wireless systems.
A low-profile circularly polarized (CP) handset antenna with end-fire and wide-beam radiation is proposed for S-band satellite communication. The antenna consists of an edge-mounted metal-strip dipole and a zeroth-order mode (ZOM) patch mountable on the backcover of mobile handset, generating a CP beam through combing two orthogonal field components with right phases. The upward end-fire CP beam is realized by optimizing the spatial configuration of the elements. A prototype was fabricated and measured, demonstrating a-6 dB impedance bandwidth of 120 MHz (2.108-2.238 GHz, 5.5%), axial ratio (AR) bandwidth of 31 MHz (2.184-2.216 GHz, 1.45%) and half power beam width (HPBW) of 148 degrees and 150 degrees in the horizontal and vertical planes at 2.2 GHz. The proposed antenna achieves a wide-beam end-fire CP radiation while preserving the integrity of the terminal's metal bezel.
This work investigates the characteristic mode analysis (CMA) along with the performance evaluation of a circularly polarized Hexa-Slot circular patch antenna integrated with an annular ring construction for millimeter-wave (mmWave) 5G communication. The proposed antenna geometry design combines six symmetrically distributed slots with an annular ring resonator to make a wideband circular polarization and strong mode excitation. CMA performed at 24 GHz, through CMA identifies 10 dominant modes contributing significantly to radiation, with modal significance values close to unity and characteristic angles aligned near 180 degrees that confirming effective modal resonance. The single-element configuration attains a gain of 8 dBi and a radiation efficiency of 93.9%, while the 2 x 2 MIMO arrangement enhances the peak directivity to 10.5 dBi and efficiency to 96.7%. The design is made on a Rogers RT5880 substrate that is 2.8 lambda(0) x 2.8 lambda(0) x 0.15 lambda(0) in size. It has a wide impedance bandwidth from 23.32 GHz to 43.84 GHz and an axial ratio below 3 dB from 27 to 36 GHz. The envelope correlation coefficient (ECC) stays below 0.00133, which means that MIMO diversity is quite good. These properties make the suggested architecture a good choice for mmWave 5G frequency bands like n257, n258, and n260.
In this paper, a reconfigurable GYSEL Power Divider (GPD) is proposed and designed using the Computer Simulation Technology (CST) simulator. The reconfigurability of the proposed GPD is insured using varactor diodes. To enhance the performance of GPD in terms of matching and miniaturization, the first two-quarter wavelength transmission lines are replaced by a T-type structure. This structure includes three varactor diodes and a stub. The varactor diodes are used to tune the frequency range of our GPD. To increase the GPD's isolation, we replaced the other quarter-wave transmission lines with an isolation network composed of two coupled lines and two isolation resistors. The use of the coupled lines offers many advantages, compared to the conventional GPD, in terms of high isolation and miniaturization. Isolation resistors also serve to dissipate power and further increase insulation. The designed structure is printed on a FR-4 substrate with dimensions of 45 & times; 35 & times; 0.8 mm3. To show the performance of the proposed GPD, simulation results of reflection, transmission, and insulation coefficients are presented. The experiment results are approximatively matched compared to the simulation results especially at the frequency 2.3 GHz and 3.5 GHz. Measurement results show that the proposed reconfigurable GPD exhibits a good adaptation at 5G mid-bands.
Proximity fed design of circular microstrip antenna backed by U-slot cut ground plane is proposed for wideband circular polarized response. The wideband response is attributed to the mutual coupling between degenerated TM11 and modified TM21 resonant modes of the circular patch. With a 900 MHz frequency spectrum and a substrate thickness of 0.088 lambda cAR, antenna offers an axial ratio bandwidth of 115 MHz (12.57%), with a reflection coefficient bandwidth of 132 MHz (14.56%). Against the U-slot in the patch, the slot in the ground plane achieves more than two times the % axial ratio bandwidth. A reduction in the substrate thickness is achieved either by using the bow-tie shape of the ground plane or by employing a shorted microstrip line feed. The U-slot cut bow-tie shape of the ground plane achieves an optimum response at a substrate thickness of 0.069 lambda cAR, and yields an axial ratio bandwidth of 94 MHz (10.21%), whereas the shorted microstrip line-fed design achieves an optimum response at a substrate thickness of 0.042 lambda cAR and yields an axial ratio bandwidth of 28 MHz (3.2%). Both the designs achieve reflection coefficient bandwidths of greater than 13% with a broadside radiation pattern and a gain of above 6 dBic. An experimental validation of the obtained results has been carried out that shows close agreement against the simulations. With the obtained results, the proposed antennas can find applications in various GSM frequency band applications.
This paper develops a complicatedly curved three-dimensional (3D) tensor holographic impedance (THI) metasurface (MTS). To the knowledge of the authors, for the first time a complicatedly ly curved 3D THI MTS is developed. The proposed THI MTS generates dual circular polarization (CP) pencil beams: (RHCP, theta = 30 degrees, phi = 0 degrees), and (LHCP, theta = 30 degrees, phi = 180 degrees). The developed THI MTS simultaneously possesses the following advantages: complicatedly curved 3D surface, wideband (measured 12.84%/13.33%) and high AE (measured 25.26%). The simulated and measured results agree well. The proposed design method can be used in designing complicatedly curved 3D THI MTS for autonomous, marine, and aerial vehicles for navigation or surveillance.
In this paper, a broadband Bessel vortex wave array antenna based on a 1-bit reflective metasurface is designed. By adopting an H-shaped fractal metasurface unit, multiple resonances can be excited to extend the bandwidth. Furthermore, by placing the metasurface unit at +/- 45 degrees along the X-axis to achieve 1-bit encoding, the phase difference of 180 degrees +/- 5 degrees and a reflection amplitude higher than 0.9 are obtained within the frequency range of 8-18.7 GHz. The reflective metasurface consists of 28 & times; 28 fractal H-shaped elements. Experiment results demonstrate that the proposed metasurface can effectively generate l=+1 OAM Bessel vortex beams in 11-18 GHz, with a maximum gain of 20.7 dBi, a peak mode purity of 84%, and non-diffraction distance of up to 108 lambda 0.
