Showing papers on "Return loss published in 2020"

Isolation Improvement of MIMO Antenna Using a Novel Flower Shaped Metamaterial Absorber at 5.5 GHz WiMAX Band

Abstract: This brief demonstrates the use of metamaterial absorber (MA) to achieve high isolation between two patch antennas in a 2-element multiple-input–multiple-output (MIMO) system operating at 5.5 GHz resonant frequency useful for WiMAX application. The proposed flower shaped MA, designed on a $9\times 9$ mm2 FR-4 substrate with 1 mm thickness, exhibits near unity normalized impedance at 5.5 GHz with an absorptivity of 98.7%. A four element array of the MA is arranged in the form of a line in the middle of the two radiating patches in order to suppress the propagation of surface current between them at the operating frequency. Using the proposed flower shaped MA, an isolation of nearly 35 dB is achieved. The MIMO structure is studied in terms of return loss, isolation, overall gain, radiation pattern, envelope correlation coefficient (ECC), diversity gain (DG), total active reflection co-efficient (TARC), etc. The structure is finally fabricated and measured to show good agreement with the simulated results.

A Gain-Enhanced Slotted Patch Antenna Using Metasurface as Superstrate Configuration

Abstract: In this paper, a novel, compact, high-gain, directive, and superstrate configuration-based metasurface (MS) antenna has been designed, which incorporates a fractal-shaped slotted patch having a periodic arrangement of square patches along with a shorting via at its center and a couple of rectangular slots in the ground plane. The MS is designed over the FR4 dielectric by introducing a periodic arrangement of unit cells in which the unit cell is structured by a C-type patterned patch in the center surrounded by a couple of L-type-shaped patches. The MS is separated by a layer of Teflon from the conventional patch antenna designed over the FR4 dielectric, thereby acting as a superstrate. The proposed antenna provides good impedance matching across the frequency region of 10.14–10.94 GHz with a unidirectional radiation pattern. A fractional bandwidth of 7.6% and a maximum return loss of 24 dB have been realized at 10.44 GHz. The measured realized gain of 7.57 dBi was obtained at the same operating frequency. As the proposed antenna is more efficient, it can be promoted for $X$ -band operations, such as satellite communication, defense purpose, and medical supervision.

A Novel Dual-Band (38/60 GHz) Patch Antenna for 5G Mobile Handsets

Abstract: A compact dual-frequency ( 38 / 60 GHz ) microstrip patch antenna with novel design is proposed for 5G mobile handsets to combine complicated radiation mechanisms for dual-band operation. The proposed antenna is composed of two electromagnetically coupled patches. The first patch is directly fed by a microstrip line and is mainly responsible for radiation in the lower band ( 38 GHz ). The second patch is fed through both capacitive and inductive coupling to the first patch and is mainly responsible for radiation in the upper frequency band ( 60 GHz ). Numerical and experimental results show good performance regarding return loss, bandwidth, radiation patterns, radiation efficiency, and gain. The impedance matching bandwidths achieved in the 38 GHz and 60 GHz bands are about 2 GHz and 3.2 GHz , respectively. The minimum value of the return loss is − 42 dB for the 38 GHz band and − 47 for the 60 GHz band. Radiation patterns are omnidirectional with a balloon-like shape for both bands, which makes the proposed single antenna an excellent candidate for a multiple-input multiple-output (MIMO) system constructed from a number of properly allocated elements for 5G mobile communications with excellent diversity schemes. Numerical comparisons show that the proposed antenna is superior to other published designs.

Four‐hundred gigahertz broadband multi‐branch waveguide coupler

Abstract: Terahertz technology is a hotspot in the current academic research. In this study, a 400 GHz broadband multi-branch waveguide hybrid coupler is designed, but it is very difficult to fabricate. In order to release the processing difficulty, a modified five-branch hybrid coupler has also been designed, fabricated and measured. The hybrid coupler consists of five modified branches and has been optimised to a great performance, which increases the operation bandwidth. Compared to the traditional five-branch hybrid coupler design, this structure has a wider operation bandwidth and the bandwidth is almost the same as traditional seven-branch hybrid coupler. Based on this model, the performance of the coupler is optimised by HFSS software. The measurement results show good performance that >18 dB return loss (S 11 ) and isolation (S 23 ), 90° ± 2° phase difference and 0.3 dB amplitude imbalance are obtained in the frequency range of 380-460 GHz, agreeing well with the simulation results.

Compact Wideband Wide-Angle Polarization-Free Metasurface Lens Antenna Array for Multibeam Base Stations

Abstract: A compact wideband wide-angle polarization-free metasurface lens (MSL) antenna array is proposed for a multibeam base station operating over the band of 1.71–2.2 GHz. The MSL element comprises of a planar wideband wide-angle polarization-free reflectionless MSL and three feeding sources of ±45° polarized cross-dipole antennas. With the shared lens aperture, the antenna achieves the three beams in the directions of 0° and ±30° in a horizontal plane. A five-layer patch-based metasurface loaded with metal poles are introduced to achieve consistent performance for wide-angle response. To reduce spillover loss, the feeding antennas are loaded with a metasurface and four directors for narrow beamwidth and low profile. With the optimized feeding antennas and MSL, a section of array with $1\,\,\times \,\,4$ MSL elements is prototyped for validation. The measured results show that an impedance bandwidth for return loss ≥ 10 dB is 1.63–2.24 GHz with the isolation larger than 22.3 dB. The measured gain ranges for 0° and 30° beams are 11.8–13.5 and 10–12.2 dBi with the sidelobe levels less than −22.6 and −13.6 dB, respectively.

A Dielectric Resonator Antenna with Enhanced Gain and Bandwidth for 5G Applications

Abstract: In this paper, a dielectric resonator antenna (DRA) with high gain and wide impedance bandwidth for fifth-generation (5G) wireless communication applications is proposed. The dielectric resonator antenna is designed to operate at higher-order TEδ15x mode to achieve high antenna gain, while a hollow cylinder at the center of the DRA is introduced to improve bandwidth by reducing the quality factor. The DRA is excited by a 50Ω microstrip line with a narrow aperture slot. The reflection coefficient, antenna gain, and radiation pattern of the proposed DRAs are analyzed using the commercially available full-wave electromagnetic simulation tool CST Microwave Studio (CST MWS). In order to verify the simulation results, the proposed antenna structures were fabricated and experimentally validated. Measured results of the fabricated prototypes show a 10-dB return loss impedance bandwidth of 10.7% (14.3-15.9GHz) and 16.1% (14.1-16.5 GHz) for DRA1 and DRA2, respectively, at the operating frequency of 15 GHz. The results show that the designed antenna structure can be used in the Internet of things (IoT) for device-to-device (D2D) communication in 5G systems.

Broadband Septum Polarizer With Triangular Common Port

Abstract: This article presents a novel broadband septum polarizer with a relative bandwidth (BW) of 37.8%. This is significantly more than the approximate 25% BW of square and circular waveguide polarizers. It is enabled by using an equilateral triangular common port waveguide, which guarantees the largest possible frequency range between fundamental and next higher order mode cutoff. The transition between the triangular section and the rectangular input waveguides, which includes the septum, is designed to accommodate this large BW. The simulation is validated using a polarizer designed for 75–110 GHz and fabricated by conventional precision milling. A second polarizer is realized for the 18-to-26 GHz range by employing additive manufacturing to demonstrate the advantages of this technology in this context. In both cases, the axial ratio remains below 1.3 dB, whereas the input port isolation and the input return loss exceed 17 and 15 dB, respectively.

Wideband 4 × 4 Butler Matrix in the Printed Ridge Gap Waveguide Technology for Millimeter-Wave Applications

Abstract: A wideband printed ridge gap waveguide $4\times 4$ Butler matrix at 30 GHz is presented. The printed ridge gap technology is used as it has very low losses and supports the propagation of quasi-TEM mode. Each component of the Butler matrix has been designed and analyzed where a superior performance is achieved in terms of bandwidth and size. The designed components are combined to form the Butler matrix. The Butler matrix has a wideband performance where the return loss and isolation levels are higher than 10 dB in the frequency range from 26.9 to 33.3 GHz, the output amplitude imbalance is ±1.6 dB, and the phase error is ±10°. The measured radiation patterns are in a good agreement with the simulated ones, beam directions are at ±13° and ±36° at the center frequency. The gain is ranging from 10.2 to 11.35 dBi for excitation from port 1 and ranging from 8.4 to 10.2 dBi for excitation from port 2.

Electronically Tunable Reflection Type Phase Shifters

Abstract: This brief presents a low loss reflection-type phase shifter (RTPS) using a single varactor diode as the load. A parallel combination of an open-circuited stub and a varactor loaded stub are used at the load terminal. This arrangement greatly improves the response of the phase shifter. A transmission line based analysis shows real part of the load plays an important role on both phase variation and insertion loss. Based on the analysis, design guidelines are provided for controlling maximum insertion loss of the phase shifter. A prototype phase shifter is fabricated at 10 GHz. Measurement results of the RTPS show a relative phase variation of 190° with a maximum insertion loss of 2 dB when varactor capacitance is varied over 0.1 pF–0.2 pF. Moreover, the return loss is always better than 20 dB over the entire tuning range of the RTPS.

Loss Compensated PCM GeTe-Based Latching Wideband 3-bit Switched True-Time-Delay Phase Shifters for mmWave Phased Arrays

Abstract: This article reports the first implementation of 3-bit millimeter-wave switched true-time-delay (TTD) phase shifters based on phase-change material (PCM) germanium telluride (GeTe). Two TTD phase shifters are presented. The first phase shifter is designed using four monolithically integrated PCM single-pole triple-throw (SP3T) switches to route the signal through delay lines. The insertion loss variation between various states is minimized by integrating two fixed PCM GeTe elements maintained in the crystalline state, along with the optimized width of the delay lines. The PCM switching cells are latching type, thus, consume no static dc power. The SP3T switches are connected back-to-back in two stages to provide a 3-bit phase shift with 20° precision. The second phase shifter is designed using two back-to-back connected PCM single-pole eight-throw (SP8T) switches. Both phase shifters are designed to operate over an 8 GHz wide frequency band with a center frequency of 30 GHz. The devices are fabricated in-house using an eight-layer microfabrication process. The proposed devices are highly miniaturized with an overall device area of 0.42mm 2 and 1.4mm 2 for the first and second phase shifter, respectively. The first phase shifter exhibit a measured average loss of 4.3 dB with a variation of ±0.3 dB and a return loss better than 20 dB, while the second phase shifter demonstrates low average measured loss of 3.8 dB with only ±0.2 dB loss variation and returns loss better than 17 dB at 30 GHz. Both phase shifters provide 180° linear phase shift with lower than 18 ps delay in the worst case.

Wideband Bandpass Frequency-Selective Structures on Stacked Slotline Resonators: Proposal and Synthetic Design

Abstract: This article presents the proposal, synthetic design, and implementation of a class of wideband bandpass frequency-selective structures (FSSs) with multiple in-band transmission poles. Each FSS element is formed by introducing parallel-coupled stepped-impedance slotline resonators (SISRs) on a printed circuit board (PCB). By periodically printing the FSS elements in long PCB pieces and then stacking them together with a certain distance, the incident spatial waves in free space can be converted into guided waves propagating along the slotline resonators of our proposed FSS and can be reconverted from guided waves into spatial waves. Therefore, the slotline resonators are designed to manipulate the incident spatial waves by controlling the filtering response of the guided waves within the FSS. An equivalent transmission-line (TL) model is then established to explain the manipulation mechanism. In order to systematically synthesize the filtering response, the transfer function of the equivalent TL model is mapped to the generalized Chebyshev equal-ripple response. The closed-form equations are derived, where all of the electrical and physical parameters are determined by the design specifications of in-band equal-ripple return loss (RL) and fractional bandwidth (FBW). To verify the theoretically predicted performances, three examples with different RLs (20, 30, and 10 dB) and FBWs (90%, 60%, and 120%) are designed, fabricated, and measured, respectively. The experimental results demonstrate that the proposed FSSs can achieve a desirable and stable wideband bandpass performance under oblique incidences. Our proposed method can also be applied to the design of other high-order wideband FSSs.

Design and Implementation of Microstrip Patch Antenna for 5G applications

Abstract: There is a need for uninterrupted high streaming online education around the world especially in developing countries like India, that requires high data rate and high bandwidth. Hence, in this research paper, authors have designed a microstrip patch antenna for high-quality online education and other 5G applications using 5G millimeter wave bands at a resonant frequency of 26 GHz. In this proposed design, authors have used a rectangular patch having a dielectric constant of 2.2 and dielectric loss tangent of 0.0010. The design is simulated and analyzed using FEKO software. Thus, after simulation authors have found a good return loss of −33.4 dB, good bandwidth of 3.56 GHz, VSWR < 2, high gain of 10 dB and antenna radiation efficiency of 99.5%. This proposed design has benefit during ongoing lockdown situation around the world.

Single-Layer Dual-Band Balanced Substrate- Integrated Waveguide Filtering Power Divider for 5G Millimeter-Wave Applications

Abstract: A single-layer substrate-integrated waveguide (SIW) filtering power divider (FPD) with fully differential operation at 28 and 39 GHz is proposed in this letter. This FPD consists of three SIW cavities where the differential and common modes of each cavity were properly designed to form three-pole dual passbands, facilitate deployment of isolation resistors, and introduce transmission zeros while attaining high in-band common-mode rejection. To improve the output return loss and isolation in dual bands, a novel and simple approach to find the proper location of isolation resistors is presented. At operating frequencies, the measured differential-mode input or output return loss, minimum insertion loss, isolation, and common-mode suppression are >14.1 dB, 14.9 dB, and >30.3 dB, respectively. The amplitude and phase imbalances between outputs are < 0.48 dB and <4.2°, respectively.

A Novel High Gain Monopole Antenna Array for 60 GHz Millimeter-Wave Communications

Abstract: This paper presented the design and implementation of a 60 GHz single element monopole antenna as well as a two-element array made of two 60 GHz monopole antennas. The proposed antenna array was used for 5G applications with radiation characteristics that conformed to the requirements of wireless communication systems. The proposed single element was designed and optimized to work at 60 GHz with a bandwidth of 6.6 GHz (57.2–63.8 GHz) and a maximum gain of 11.6 dB. The design was optimized by double T-shaped structures that were added in the rectangular slots, as well as two external stubs in order to achieve a highly directed radiation pattern. Moreover, ring and circular slots were made in the partial ground plane at an optimized distance as a defected ground structure (DGS) to improve the impedance bandwidth in the desired band. The two-element array was fed by a feed network, thus improving both the impedance bandwidth and gain. The single element and array were fabricated, and the measured and simulated results mimicked each other in both return loss and antenna gain.

A compact lowpass filter for satellite communication systems based on transfer function analysis

Abstract: This paper presents a very efficient design procedure for a high-performance microstrip lowpass filter (LPF). Unlike many other sophisticated design methodologies of microstrip LPFs, which contain complicated configurations or even over-engineering in some cases, this paper presents a straightforward design procedure to achieve some of the best performance of this class of microstrip filters. The proposed filter is composed of three different polygonal-shaped resonators, two of which are responsible for stopband improvement, and the third resonator is designed to enhance the selectivity of the filter. A holistic performance assessment of the proposed filter is presented using a Figure of Merit (FOM) and compared with some of the best filters from the same class, highlighting the superiority of the proposed design. A prototype of the proposed filter was fabricated and tested, showing a 3-dB cut-off frequency (fc) at 1.27 GHz, having an ultrawide stopband with a suppression level of 25 dB, extending from 1.6 to 25 GHz. The return loss and the insertion loss of the passband are better than 20 dB and 0.25 dB, respectively. The fabricated filter has a high FOM of 76331, and its lateral size is 22.07 mm × 7.57 mm.

Ultrathin Antenna-Integrated Glass-Based Millimeter-Wave Package With Through-Glass Vias

Abstract: This article presents the design and demonstration of a high-bandwidth antenna-in-package (AiP) module focusing on low-loss interconnects and Yagi–Uda antenna performance fabricated on a 100- $\mu \text{m}$ low coefficient-of-thermal-expansion (CTE) glass for the 28-GHz band. It shows the modeling, design, and characterization of key technology building blocks along with the process development of advanced 3-D glass packages. The building blocks include impedance-matched antenna-to-die signal transitions, Yagi–Uda antenna, and 3-D active–passive integration with backside die assembly on 100- $\mu \text{m}$ glass substrates. The design and stack-up optimization of antenna-integrated millimeter-wave (mm-wave) modules is discussed. Process development to achieve high-density interconnects and precise dimensional control in multilayered thin glass-based packages is also described. The characterization results of the key technology building blocks show an insertion loss of 0.021 dB per through-package via (TPV), leading to the whole-chain loss of less than 1 dB and a return loss lower than 20 dB. The fabricated Yagi–Uda antenna features high repeatability of wide bandwidth due to the process control enabled by glass substrates. The antenna measurements show a bandwidth of 28.2%, which covers the entire 28-GHz fifth-generation (5G) frequency bands (n257, n258, and n261). The flip-chip assembled low-noise amplifier with 80- $\mu \text{m}$ solder balls shows a maximum gain of 20 dB as desired. The performance of the glass-based package integrated antennas is benchmarked to other 5G substrate technologies, such as organic laminates or co-fired ceramic-based substrates.

Compact Metamaterial Based $4\times4$ Butler Matrix With Improved Bandwidth for 5G Applications

Abstract: This paper proposes a novel compact 4 × 4 butler matrix (BM) with improved bandwidth based on open-circuit coupled-lines and interdigital capacitor unit-cell to develop composite right/left handed (CRLH) transmission-line (TL) metamaterial structure. The BM is implemented by the combination of compact 3dB quadrature hybrid couplers, 0dB crossover and 45° phase shifter on a single FR4 substrate (er = 4.3 and h = 1.66 mm). The simulated and measured result shows that the return loss and isolation loss are better than 14 dB at all the ports, good insertion loss of -7 ± 2dB, which cover the frequency range of 3.2 GHz to 3.75 GHz. The phase difference of -45°, 135°, -135° and +45° are achieved with a maximum average phase tolerance of 5°. The overall dimension of the BM is 70mm × 73.7mm, which shows the compactness of the proposed design that is 75% size reduction and 8.2 times improvement in the bandwidth (550MHz) as compared to conventional BM. The CST microwave studio is used to design and perform the simulations. Additionally, the simulated and measured scattering parameters and phase differences show that they are in good agreement. This compact and improved bandwidth of the proposed BM is suitable for 5G antenna array beamforming network.

Ultraminiaturized Wideband Quasi-Chebyshev/-Elliptic Impedance-Transforming Power Divider Based on Integrated Passive Device Technology

Abstract: This article presents the ultraminiaturized wideband quasi-Chebyshev and -elliptic low-pass power dividers (PDs) with an impedance-transforming function using integrated passive device (IPD) technology, occupying only the sizes of $1.1\times1.2$ mm2 and $1.1\times1.6$ mm2, respectively. The generalized quasi-Chebyshev low-pass matching network with the detailed design procedure is utilized to construct the circuit schematic of the proposed wideband PD. In order to further improve stopband rejection, a quasi-elliptic network is introduced, resulting in an extra transmission zero (TZ). For demonstration, the quasi-Chebyshev and -elliptic PDs based on IPD technology are designed, manufactured, and measured, respectively. Measurements indicate that the quasi-elliptic PD with TZ shows good electrical responses, including lower than 1.08-dB insertion loss, all better than 15-dB return loss and isolation from 2.49 to 5.0 GHz.

Multilayer Topology Optimization of Wideband SIW-to-Waveguide Transitions

Abstract: This article utilizes a topology optimization approach to design planar multilayer transitions between substrate integrated waveguides (SIWs) and rectangular waveguides (RWGs). The optimization problem is formulated based on the modal field analyses and Maxwell’s equations in the time domain solved by the finite-difference time-domain (FDTD) method. We present a time-domain boundary condition based on the Klein–Gordon equation to split traveling waves at homogeneous waveguide ports. We employ the boundary condition to compute portal quantities and to devise an adjoint-field system that enabled an efficient computation of the objective function gradient. We solve design problems that include more than 105 000 design variables by using less than 400 solutions of Maxwell’s equations. Moreover, a new formulation that effectively combats the development of in-band resonances in the design is presented. The transition configuration allows the direct mount of conventional RWG sections on the circuit board and aims to cover the entire K-band. The guiding structure of the optimized transition requires blind vias, which is realized by a simple and cost-efficient technique. In addition, the transition is optimized for three different setups that can be used to provide different field polarizations. The proposed transitions show less than 1-dB insertion loss and around 15-dB return loss over the frequency interval 18–28 GHz. Several prototypes are fabricated with an excellent match between the simulation and measurement results.

Compact X-band Stepped-Thickness Septum Polarizer

Abstract: This paper presents the results of development of a X-band compact stepped-thickness septum polarizer. All electromagnetic characteristics of the polarizer have been simulated and optimized numerically. A prototype of the polarizer has been designed, fabricated and tested. It has been shown that the use of a stepped-thickness septum instead of a constant-thickness one improves the return loss and XPD of the septum polarizer by 5 and 7 dB, respectively. Measured VSWR of the designed compact septum polarizer is less than 1.4 in the operating frequency band 7.70-8.50 GHz. Tested differential phase shift varies from 83° to 100°. Suggested compact septum polarizer is designed for a quasi-monopulse feed of a dual-polarized ground station antenna system. Measured XPD of the polarizer in an assembled feed system is higher than 30 dB.

Metasurface Lens for Ultra-Wideband Planar Antenna

Abstract: In this article, an ultra-wideband metasurface lens is designed and integrated into an antipodal Vivaldi antenna (AVA) to improve its radiation directivity without affecting its efficiency and return loss characteristics. The metasurface lens consists of high permittivity metamaterial unit cells which resonate at frequencies far away from the operation bandwidth of 1–6 GHz. Electric field distributions of the antennas show that the near-field behaves more planar for the metasurface lens loaded AVA, as compared to conventional AVA. Both the original antenna and the newly proposed antenna are simulated, fabricated, and tested. The measurements are found in very good agreement with the simulation results. In the operation bandwidth of 1–6 GHz, the return loss is less than −10 dB for both antennas. As verified by far-field measurements, the metasurface loaded AVA has achieved higher gain in the operation bandwidth. Additionally, the half power beamwidth of the AVA is significantly reduced by the inclusion of the metasurface lens.

Design of a Circularly-Polarized UHF Antenna for Partial Discharge Detection

Abstract: In this work, a circularly-polarized ultra-high frequency (UHF) partial discharge (PD) antenna is proposed to detect the PD in 0.6 GHz - 1.7 GHz. The proposed PD antenna consists of an Archimedean spiral antenna, a balun, and a cavity. The Archimedean spiral antenna is embedded by FR-4 as substrate and superstrate for miniaturization. The microstrip-to-paired strips balun is designed to yield good performance in the return loss, insertion loss, and amplitude and phase imbalances which are of great necessity for low axial ratio. The cavity is employed to obtain unidirectional radiation patterns and prevent external signal interference. However, it is found that the originally-designed cavity-backed antenna does not work properly near 1.35 GHz due to resonance phenomena in the cavity. In this work, the cavity is modified to tackle this problem. The proposed UHF PD antenna is fabricated and measured and the results show that it provides good impedance matching, realized gain, radiation pattern, and circular polarization.

Design and Optimization of Microstrip Patch Antenna for UWB Applications Using Moth–Flame Optimization Algorithm

Abstract: The design of microstrip patch (MP) antenna using Moth–Flame optimization (MFO) algorithm for UWB applications is presented in this article. MP antennas are designed to operate in dual and multi-band application as it possess the following advantages such as low cost, light weight and easy installation. To reduce the microstrip patch cross-polarized radiation and to attain the essential radiation parameters, the MP antenna is designed with a defected ground structure. The substrate of liquid crystal polymer is used here to reduce the material cost and the applicable geometry parameters are used to improve antenna performance. The MFO optimized antenna represents 50 mm × 50 mm compact size, which improves the performance of antenna. However, the simulation procedure is done by the MATLAB tool along with high frequency structure simulator for parameter optimization and performance analysis respectively. The operational bandwidth of the antenna is 3.1 GHz and the return loss is − 20 dB that covers the UWB (3.1–10.6 GHz) applications. The simulation outcomes exhibit good impedance bandwidth, radiation pattern, directivity, and relatively constant gain over the entire band of frequency comparing with the earlier methods. Finally, the proposed system can be a better option for the design of microstrip antenna in the communication system, to cover Bluetooth operations, Wi-Fi, Wi-MAX, Telemedicine and UWB applications.

3D printed waveguide step-twist with bandpass filtering functionality

Abstract: A novel waveguide step-twist integrated with a bandpass filter is presented in this Letter. The twist is composed of four equally rotated cavities to achieve polarisation rotation and filtering functionalities simultaneously. Such step-twist can achieve a significant reduction in size and weight. The design is demonstrated at Ka-band using waveguide technology and is fabricated using a stereolithography apparatus 3D printing together with metal plating. The device is designed to have a centre frequency of 32 GHz and a bandwidth of 1 GHz. The measured result shows good agreement with simulations, with a measured average insertion loss of 0.84 dB and a return loss better than 15 dB across the passband.

Frequency Reconfigurable Antenna Designs Using PIN Diode for Wireless Communication Applications

Abstract: In this paper a compact reconfigurable antenna with switchable slot is designed and proposed, the slot is etched on the rectangular patch and inclusion of PIN diode which is used to switch the slot in ON and OFF states, the patch is fed by a probe coaxial (50 Ω), this type of antenna permits to have multiple frequencies. In this study, it is observed that frequency diversity can obtained by controlling the bias voltage with unchanged antenna, unchanged feeding probe and unchanged geometric shape of the patch, the thing that was not previously feasible of the unslotted patch antenna. The results in terms of return loss and radiation pattern are given and good performances are obtained and show that the proposed antenna operates at different frequencies which can be used for several applications, especially in wireless communication systems, according to the bias voltage and the location of the slot.

Balun-Fed Dual-Polarized Broadband Filtering Antenna Without Extra Filtering Structure

Abstract: A dual-polarized filtering antenna without using extra parasitic element or filtering circuit is proposed. The proposed antenna consists of two pairs of dipole arms and baluns. The balun feeding scheme is used to form two half-wavelength resonators, which introduce two radiation nulls in the upper stopband. Meanwhile, in the lower stopband, another radiation null is generated by the radiation cancellation between the dipoles and the baluns. As a result, a bandpass filtering response is realized owing to these three radiation nulls. For demonstration, a prototype is fabricated and measured. The prototype has an impedance bandwidth of 50% (return loss >15 dB within the band 1.65−2.75 GHz). The average measured gain is 8.1 dBi. Within the lower stopband of 0−1.25 GHz, the out-of-band suppression level is more than 30 dB. Furthermore, the suppression level is over 16 dB in the upper stopband of 3.3−5 GHz. Such features make the proposed antenna suitable for multiband array applications to reduce the mutual coupling between elements operating at adjacent frequencies.

Silicon Micromachined D-Band Diplexer Using Releasable Filling Structure Technique

Abstract: A D-band waveguide diplexer, implemented by silicon micromachining using releasable filling structure (RFS) technique to obtain high-precision geometries, is presented here for the first time. Prototype devices using this RFS technique are compared with devices using the conventional microfabrication process. The RFS technique allows etching large waveguide structures with nearly 90° sidewall angles for the 400- $\mu \text{m}$ -tall waveguides. The diplexer consists of two direct-coupled cavity six-pole bandpass filters, with the lower and the upper band at 130–134 and 141–148.5 GHz, respectively. The measured insertion loss of the two bands is 1.2 and 0.8 dB, respectively, and the measured return loss is 20 and 18 dB, respectively, across 85% of the passbands. The worst case adjacent channel rejection is better than 59 dB. The unloaded quality factors of a single cavity resonator are estimated from the measurements to reach 1400. Furthermore, for the RFS-based micromachined diplexer, an excellent agreement between measured and simulated data was observed, with a center frequency shift of only 0.8% and a bandwidth deviation of only 8%. In contrast to that, for the conventionally micromachined diplexer of this high complexity, the filter poles are not well controllable, resulting in a large center frequency shift of 3.5%, a huge bandwidth expanding of over 60%, a poor return loss of 6 and 10 dB for the lower and the upper band, respectively, and an adjacent channel rejection of only 22 dB.