Showing papers on "Return loss published in 2018"

Tri-Polarized 12-Antenna MIMO Array for Future 5G Smartphone Applications

Abstract: A tri-polarized 12-antenna array working in the 3.5-GHz band (3.4–3.6 GHz) for future 5G (the fifth generation mobile communication) multiple-input multiple-output (MIMO) operations in the smartphone is presented. In order to reduce the mutual couplings and simplify the design process, orthogonal polarization technique is utilized. By combining a quarter mode substrate integrated wave-guide antenna and two open-end slots, a compact 3-antenna tri-polarization block operating in the 3.5-GHz band is achieved within a small volume of $17\times 17\times6$ mm3. Thanks to the orthogonal polarization features, the three antennas within the block are able to have good impedance matchings and low mutual couplings between antennas. By integrating four such tri-polarization blocks, a 12-antenna MIMO array is then designed for smartphone applications. It is also due to the tri-polarization feature, the proposed array could attain acceptable isolations and low correlations between antennas with only two additional decoupling structures. The proposed array is fabricated and tested, good antenna performances, such as return loss better than 10 dB, isolation higher than 12.5 dB, and antenna efficiencies higher than 50%, are obtained. The channel capacity of the 12-antenna array is calculated to be about 57 bps/Hz in a $12\times12$ MIMO system with 20-dB signal-to-noise ratio, which indicates the proposed array using tri-polarization technique is a good choice for future 5G terminals.

A Dual-Band Metasurface Antenna Using Characteristic Mode Analysis

Abstract: A compact metasurface-based antenna is proposed for dual-band operations. The proposed metasurface is designed on a single-layered substrate including an array of modified $3 \times 3$ squared patches. Each of the four corner patches is split into four fractional patches while the four edge patches are evolved into Malta crosses and the center patch is scaled. A substrate integrated waveguide-based Y-junction cavity-fed dual slot drives the metasurface with multiple impedance resonances. Based on the predicted modal behaviors of metasurface using a characteristic mode analysis (CMA), as an example, an antenna operating at three resonant modes at 28, 33, and 36 GHz, respectively is designed for the dual-band operation for the coming 5G. The proposed design shows that the measured impedance bandwidths (return loss larger than 10 dB) are 23.7–29.2 GHz and 36.7–41.1 GHz with the achieved gain of 4.8–7.2 dBi and 8.9–10.9 dBi, respectively. The proposed dual-band antenna features the advantages of low profile and wideband, suitable for the coming dual-band 5G applications.

A Fully Integrated Shark-Fin Antenna for MIMO-LTE, GPS, WLAN, and WAVE Applications

Abstract: In this study, a three-dimensional compact antenna solution for the automotive industry is proposed. The antenna solution is designed to fit in a shark-fin case and is easily fabricated from a printed circuit board and a metal sheet with low-cost process and materials. The antenna solution covers Long Term Evolution (LTE), GPS, WLAN, and Wireless Access in the Vehicular Environment (WAVE) bands (850 MHz, 1575 MHz, 2.4 GHz, and 5.9 GHz, respectively). The planar inverted-F antennas are used as multiple-input–multiple-output antennas for the LTE band due to their low-profile structure. Modified planar monopoles are used to obtain omnidirectional radiation patterns for WLAN and WAVE bands. Antenna characteristics such as return loss, isolation, and radiation pattern have been simulated and measured to confirm the possibility for use in automotive applications.

Wideband Substrate-Integrated Waveguide-Fed Endfire Metasurface Antenna Array

Abstract: A vertically polarized substrate-integrated waveguide (SIW)-fed endfire metasurface antenna array is proposed for wideband operation. Each of the metasurfaces consists of $3\times 3$ rectangular patches and is printed on the two surfaces of a single-layered substrate with a thickness of $0.16\lambda _{0}$ (where $\lambda _{0}$ is the wavelength at 32.65 GHz in free space). The antenna is fed at one side of metasurface by an open-end SIW for wideband endfire radiation. The proximity-coupled interdigital strips are introduced between the SIW and metasurface for fault-tolerant coupling. The wideband operating mechanism is revealed by studying the propagation mode and multiple resonant modes of metasurface. To verify the proposed antenna, a $1\times 4$ array is presented with uniform excitation including two SIW Y junctions and an SIW T junction. Moreover, the connected SIW Y junction improved the impedance matching at the low frequencies based on the cavity mode analysis. The proposed design shows that the measured impedance bandwidth (10 dB return loss) is 26.6–38.7 GHz (37%) with the achieved gain of 9.1–13.8 dBi.

Microstrip Multifunctional Reconfigurable Wideband Filtering Power Divider with Tunable Center Frequency, Bandwidth, and Power Division

Abstract: In this paper, a microstrip reconfigurable wideband filtering power divider (FPD) with tunable center frequency (CF), bandwidth (BW), and power division is presented. The proposed structure consists of two trimode stub-loaded resonators, a three-line coupled structure loaded two varactor diodes, and two output parallel-coupled lines loaded a lumped capacitor. The CF and BW of wideband filtering response can be tuned by controlling the varactor diodes loaded onto the open end of trimode resonators. Meanwhile, the power division ratio (PDR) is controlled by tuning the coupling strength between the center line and sidelines of three-line coupled structure. Compared with the conventional wideband FPDs, the capacitor loaded onto the parallel-coupled line of two output ports is to enlarge the coupling, which can increase the return loss (RL), and thus relieve the limitation of the line space between two coupled lines. A complete design procedure with analytical design equations for driving parameters of the structure is described. The measured results show that the CF can be tuned from 0.86 to 1.32 GHz with RL better than 16 dB, while the 1-dB BW can be tuned from 180 to 710 MHz. The measured isolation is better than 21 dB from dc to 2.5 GHz. Then, the achieved PDR can be tuned from 1:1 to 3:1. The proposed circuit can be also utilized as a switchless bandstop filter, where the isolation is better than 20 dB from dc to 19 GHz. The proposed tunable wideband FPD exhibits good RL, wide range of frequency and BW control, wide harmonic suppression, high isolation, and multifunctional application.

Performance of Tri-Band Multi-Polarized Array Antenna for 5G Mobile Base Station Adopting Polarization and Directivity Control

Abstract: In this paper, the performance of tri-band multi-polarized adaptive array antenna for 5G mobile base station is introduced adopting the polarization and directivity control. First, the design of multi-band circularly polarized antenna element at 28/38/48 GHz is presented. The measured results show that the designed antenna element has a reflection coefficient of less than −20 dB in the assigned frequency bands of 28/38/48 GHz with a realized antenna gain of 7.82 dB, 8.39 dB, and 7.73 dB, respectively. Based on the designed antenna element, a 32-element are distributed in an octagonal prism configuration is presented as possible candidates for the future 5G mmWave cellular networks. The antenna array performance is studied in terms of gain, radiation efficiency, return loss, and axial ratio for different scenarios, in addition, the metrics of total scan pattern and coverage efficiency are investigated. To optimize the antenna parameters and synthesizing multi-beam patterns, a modified version of hybrid gravitational search algorithm and particle swarm optimization algorithm is introduced. This enhancement has improved the global search ability and accelerates the convergence capability. The proposed array antenna achieved good S11 < −20 dB with high isolation between the array elements. Besides, an acceptable realized gain of 16.85 dB on average with a radiation efficiency of more than 82 % is obtained in the entire operation bands.

Analysis of RF MEMS shunt capacitive switch with uniform and non-uniform meanders

Abstract: This paper reports on electromechanical, switching time and performance analysis of capacitive shunt RF MEMS switch with uniform and non-uniform meanders. The MEMS switch is a freely moving membrane over coplanar wave guide. Electromechanical analysis is done for movable beam with gold as material and dielectric as Si3N4 and HfO2. For these dielectric materials pull in voltage is 2.3 and 2 V respectively with beam thickness of 0.8 µm by using COMSOL FEM Tool. Si3N4 with dielectric constant of 7.6 gives Cratio of 8.69 and 11.13 for 0.8 and 0.6 μm of beam thickness respectively. RF performance analysis is done by using HFSS software and the simulation results states that non uniform single meander has return loss as −60 dB, insertion loss −0.2 dB and isolation loss −14 dB at 20 GHz frequency and uniform 3 meander switch has return loss as −55 dB. Switching time analysis is done by using MATLAB. For uniform three meander it is 0.12 ms and for non-uniform one meander beam it is 0.7 ms. Whereas use of HfO2 with dielectric constant of 14 as dielectric gives Cratio of 14.93 and 19.66 for 0.8 and 0.6 μm of beam thickness respectively with gap between the electrode beam and dielectric as 0.8 μm.

A Compact Polarization-Reconfigurable and 2-D Beam-Switchable Antenna Using the Spatial Phase Shift Technique

Abstract: In this paper, a compact patch array antenna with reconfigurable polarizations and 2-D switchable beams is developed based on the spatial phase shift technique. A compact element antenna is proposed with switchable ports for implementing the spatial phase shift technique, which is composed of a square driven patch, two sets of perturbation segments connected to the driven patch via p-i-n diodes for polarization diversity, a parasitic patch, and three switchable feeding probes integrated with a designed single-pole triple-throw switch. For circular polarized waves, individual excitation at the three feeding probes can obtain a 90° or 180° phase difference because of the spatial relative position between the feeding probes. The radiation beam and polarization of the $2{\times} 2$ array antenna can be dynamically reconfigured among nine beams and dual-circular polarization modes by properly switching these feeding probes and perturbation segments. In addition, the 3 dB axial-ratio bandwidths are effectively enhanced by using the spatial phase shift technique. To validate the proposed concept, a prototype operating at 4.8 GHz is designed, fabricated, and measured. The measured 10 dB return loss bandwidths for all operating states can cover a frequency band of 4.63–5.07 GHz with measured gains ranging from 7.5 to 10.5 dBic.

Design and performance analysis of uniform meander structured RF MEMS capacitive shunt switch along with perforations

Abstract: This paper presents design and simulation of uniform structured RF MEMS capacitive shunt switch using FEM tool and HFSS software. The switches with different shaped meanders and perforations which result in less spring constant, less pull-in voltage, high isolation loss, high switching speed and low insertion loss have been designed. From the simulated results it is observed that the rectangular perforations gives the better results, when compared with square and cylindrical shaped perforations. Comparative study is done for zigzag, plus and three square shaped meander along with rectangular perforations on each structure. When the gap between the dielectric and the movable beam is 0.8 µm, the up state capacitance for HfO2 is 4.06fF and for Si3N4 is 3.80fF. The downstate capacitance for HfO2, Si3N4 is 49fF, 26.9fF respectively. The capacitance ratio is 120.6. Poly-tetra-fluoro-ethylene material is given for the movable beam whose young’s modulus is 0.4 GPa and the spring constant is calculated theoretically for each structure; by using this the pull in voltage and the settling time are calculated. Step switch with three square Meander has switching time 10.25 µs, pull in voltage as 2.45 V. By using HFSS 3-D electromagnetic model we observed the return loss (S11) is less than −60 dB, the insertion loss is less than −0.07 dB in the range of 1–40 GHz frequency and switch isolation (S21) is −61 dB at 28 GHz frequency.

Design of 28/38 GHz Dual-Band Triangular-Shaped Slot Microstrip Antenna Array for 5G Applications

Abstract: Nowadays, evolving an advanced technology for the next generation of wireless cellular communication networks has put a great interest for researchers over the world. This aim is to accomplish the growing demand for advanced data rates. The fifth generation (5G) promises more advantages and benefits to the world. It will create an essential difference over 4G. The design of 5G antenna providing broad bandwidth is very important to ensure the performance of 5G networks. In this paper, microstrip antennas array of single, two, four and six elements dual-band (28/38GHz) for 5G applications are discussed. The proposed antennas are printed on 1.575 mm-thick Rogers Duroid 5880 substrate with dielectric constant of e r = 2.2 and loss tangent (tan δ) of 0.0009. They consist of a triangular shaped radiating patch fed by a 50 Ω microstrip line. The antenna bandwidth is furthered by etching the triangular shaped slot on the ground plane. The highest gain is provided by the antenna with six elements array for both frequencies. The maximum gain of 7.47 dBi with return loss of −30.70 dB at 28 GHz and 12.1 dBi with return loss of −34.5 dB at 38 GHz are obtained.

A novel RF MEMS switch on frequency reconfigurable antenna application

Abstract: This paper presents the design, analysis, simulation of a novel radio-frequency micro electromechanical system (RF MEMS) switch on the frequency reconfigurable antenna application. The switch uses coplanar waveguide transmission line for signal transmission, which designed with special mechanical structures, the size of the switch beam is 320 × 120 μm2. The design of RF MEMS switch was simulated using ANSYS. Its simulation voltage is 14 V for 1 µm beam thickness. The electromagnetic performance is optimized and computed by ANSYS EM software. The switch working bandwidth is 40 GHz, the insertion loss is 0.1 dB, return loss of 30 dB and isolation of 26 dB over 30 GHz. In the frequency band, the isolation degree more than 15 dB, and the maximum isolation is 45.3 dB. The switch is mounted on the antenna, and the frequency of the antenna can be reconstructed by using ANSYS EM simulation.

Broadband Transition of Substrate-Integrated Waveguide-to-Air-Filled Rectangular Waveguide

Abstract: A single-layer right-angle broadband transition between the substrate-integrated waveguide and air-filled standard rectangular waveguide is proposed and demonstrated at the V-band. An aperture coupled patch with two pairs of inductive posts is employed to form the transition. An impedance bandwidth wider than 48% for return loss less than −10 dB is achieved. The proposed back-to-back transition is fabricated on a single layer substrate using the printed circuit board technology. The measured results of back-to-back prototype show that the insertion loss of a single transition is less than 0.5 dB. The measured results show a good agreement with HFSS simulation results. This transition with compact size, wide bandwidth, and low cost can be used for a variety of millimeter-wave circuits and systems.

A Compact Microstrip Patch Antenna at 28 GHz for 5G wireless Applications

Abstract: A compact planar inset-fed microstrip antenna applicable for 5G Wireless system at millimeter wave frequency (28 GHz) is described. The antenna parameters are optimized using the CST Microwave Studio. Simulated return loss plot, far-field radiation pattern and polar plot gain is achieved at 28 GHz frequency. The simulation result met the 3GPP Release-15 operating in 28 GHz frequency band for 5G Wireless applications. The simulated results shows a return loss of -17.4dB, gain of antenna is 6.72 dB and the voltage standing wave ratio VSWR < 2 at 28 GHz indicating that the antenna has minimum reflection at this frequency.

Graphene Microstrip Patch Ultrawide Band Antennas for THz Communications

Abstract: Future generation local communication systems will need to employ THz frequency bands capable of transferring sizable amounts of data. Current THz technology via electrical excitation is limited by the upper limits of device cutoff frequencies and by the lower limits of optical transitions in quantum confined structures. Current metallic THz antennas require high power to overcome scattering losses and tend to have low antenna efficiency. We show here via calculation and simulation that graphene can sustain electromagnetic propagation at THz frequencies via engineering the intra- and interband contributions to the dynamical conductivity to produce a variable surface impedance microstrip antenna with a several hundred GHz bandwidth. We report the optimization of a circular graphene microstrip patch antenna on silicon with an optimized return loss of -26 dB, a -10 dB bandwidth of 504 GHz and an antenna efficiency of -3.4 dB operating at a frequency of 2 THz. An improved antenna efficiency of -0.36 dB can be found at 3.5 THz but is accompanied by a lower bandwidth of about 200 GHz. Such large bandwidths and antenna efficiencies offers significant hope for graphene based flexible directional antennas that can be employed for future THz local device-to-device communications.

Orthomode Transducers With Folded Double-Symmetry Junctions for Broadband and Compact Antenna Feeds

Abstract: Orthomode transducers (OMTs) using folded six-port waveguide junctions are presented for obtaining the maximum compactness in antenna feeds with very wide performance. The proposed junctions are based on the well-known turnstile and Boifot configurations, having two symmetry planes for keeping the isolation between orthogonal polarizations and the control of higher order modes. The folded arms provide a combined effect: good matching with very significant size reduction, especially in the transversal plane, reducing mass in satellite systems and allowing feeding eventual dense horn antenna arrays. Two Ku-band OMTs are presented in order to illustrate the advantages of the introduced junctions. The first design covers the band 10.4–18.8 GHz (57.5%) with 24 dB return loss. The second OMT, for the 12.60–18.25 GHz band, has measured return loss better than 29 dB in the design band and insertion loss smaller than 0.11 dB for both polarizations.

Control of Beam Direction for Substrate-Integrated Waveguide Slot Array Antenna Using Metasurface

Abstract: The method to control the aperture phase distribution of antenna using a metasurface is proposed to point the antenna beam to desired directions. A $1\times 10$ substrate-integrated waveguide (SIW) slot array antenna directly integrated with the metasurface of double-layer miniaturized framed Jerusalem crosses is, for example, designed to achieve the oblique radiation beam in 30° at $Ka$ -bands. In order to achieve a full 360° transmission phase range, part of SIW slots are inverted to obtain additional 180° phase shift so that more than 400° phase shift range is realized. The measured results show that the beam directions are within 29.3 ± 1° from 34.25 to 35.75 GHz with a return loss better than 15 dB. The measured maximum gain is 12.1 dBi at 34.75 GHz. The combination of the array antenna and the metasurface features a low profile, simple structure, and flexible design for oblique beam application.

Balanced Antipodal Vivaldi Antenna With Asymmetric Substrate Cutout and Dual-Scale Slotted Edges for Ultrawideband Operation at Millimeter-Wave Frequencies

Abstract: This communication examines how to improve the squinted radiation patterns produced by the balanced antipodal Vivaldi antenna (BAVA) while retaining its cross-polarization levels. In particular, we propose discarding the redundant substrate between the metal flares of the BAVA and implementing dual-scale slotted edges to improve the radiation characteristics. The gain at both the lower and the higher end of the band is significantly enhanced without increasing the antenna size. Moreover, significant reduction in the beam squint relative to the conventional BAVA designs is achieved. A microstrip-to-stripline transition is also introduced to improve low-end matching. The final design operates over 10–40 GHz with return loss <−10 dB, providing sufficient bandwidth and match for a variety of applications at millimeter-wave frequencies. Numerical and experimental assessments to validate the proposed antenna design are conducted.

An Optimal Design of Fractal Antenna with Modified Ground Structure for Wideband Applications

Abstract: This paper premeditates an optimal design of fractal antenna with modified ground structure for wideband applications. The proposed antenna has been designed by taking numerous iterations started from 0th to 3rd. To attain the wideband characteristics, the partial ground plane has been introduced in the 3rd iteration, and the length of the ground plane has been varied to enhance the bandwidth. The maximum value of bandwidth has been adorned in the final iteration as 1.88 and 0.20 GHz. Further, this bandwidth has been improved and embellished as 2.48 GHz within the frequency range of 3–6 GHz by employing horizontal and vertical extensions in the partial ground plane. Antenna is simulated by using HFSS and performance parameters of antenna like return loss (S11 ≤ − 10 dB), gain and radiation efficiency are in the acceptable limits. The maximum value of gain is reported as 5.1 dB and radiation pattern is also omnidirectional. The proposed antenna is useful for the wireless applications as WiMAX (3.4–3.69 GHz) and WLAN (5.15–5.35 and 5.72–5.82 GHz) Simulated and experimental results are also juxtaposed and found in good agreement with each other.

A Novel Dual-Band Decoupling and Matching Technique for Asymmetric Antenna Arrays

Abstract: A novel dual-band decoupling and matching technique for asymmetric two-element antenna arrays is proposed. Decoupling and matching at two widely separated frequencies is accomplished by using a two-layer (level) network approach. Unlike previous works, analytical solution is readily available and prematching of the radiating elements is no longer required. Simulation and experimental results show that the proposed method can offer improved port isolation and input return loss, enhanced efficiency, and increased radiation pattern diversity in both frequency bands.

Detection of Salt and Sugar Contents in Water on the Basis of Dielectric Properties Using Microstrip Antenna-Based Sensor

Abstract: This paper presents a microstrip antenna-based sensor for detecting salt and sugar in water. The patch antenna is low-cost and low-profile and is modeled to transmit and receive an electromagnetic signal. The presented antenna consists of a crescent-shaped patch and slotted partial ground. The compact size of the antenna is 32 mm $\times22$ mm. High-frequency structure simulator and computer simulation technology are used to simulate and analyze the characteristics of the antenna. The presented antenna achieves a 10 dB return loss from 2.50 to 18 GHz with 6.10 dBi of maximum gain, considerable efficiency, and consistent radiation patterns. The presented antenna is used as a sensor to detect salt and sugar in water in terms of reflection coefficient based on the dielectric properties of the solution. The percentage of salt and sugar in water changes the dielectric properties of the solution and the reflection coefficients subsequently. Results during the practical observations show that the reflection coefficient decreases with the increment of salt and sugar contents in the solution. With the excellent basic wideband antenna performances, the antenna shows good sensitivity to detect salt and sugar content in water. The presented antenna is suitable to be used in wideband wireless communications as well as wideband sensor applications.

$E$ -Band Substrate Integrated Waveguide Orthomode Transducer Integrated With Dual-Polarized Horn Antenna

Abstract: This paper presents an E-band substrate integrated waveguide (SIW) dual-polarized antenna system, which consists of an orthomode transducer (OMT) and a dual-polarized horn antenna. On the basis of a two-layer substrate design, the function of OMT is realized by utilizing an SIW section to excite TE10 mode for the vertical polarization, a quasi-coaxial stripline to excite quasi-TEM mode for the horizontal polarization. And also, a slot line transition is placed at the common port of the two structures for impedance matching with the ridge SIW dual-polarized horn antenna. In this way, the dual-polarized horn antenna is designed with an exponential ridge structure simultaneously for better impedance matching and higher efficiency of the antenna. To verify the functionality of the proposed integrated OMT-antenna structure, an experimental prototype is fabricated and measured, and a good agreement is found between its simulation and measured results. Over the frequency range of 83–87 GHz, return loss better than 10 dB at all ports and cross-polarization less than −25 dB are obtained. The maximum antenna gain is about 14 dBi for the horizontal polarization and 15.2 dBi for the vertical polarization. It is believed that the proposed OMT-antenna design is suitable for ultrahigh capacity millimeter-wave backhaul applications in future wireless communication systems.

Compact Ultra-Wide Band MIMO Antenna System for Lower 5G Bands

Abstract: This paper presents a novel compact 2 × 2 planar MIMO antenna system with ultra-wide band capability. Antenna system is specifically designed to target lower 5th generation operating bands ranging from 2 GHz to 12 GHz. This band also covers the IEEE 802.11 a/b/g/n/ac. The antenna array geometry has been simulated using CST MWS. The design is extremely miniaturized with total structure size of mm3. The simulated and measured results have been presented. Measured and simulated return loss values for designed antenna are less than −10 dB over the operating band and lowest values of −35 dB and −32.5 dB can been seen at 5.2 GHz and 9.2 GHz, respectively, whereas at the center frequency the return loss is −25.2 dB. The mutual coupling between both elements is less than −20 dB over the transmission bandwidth. Simulated and measured radiation patterns in E and H planes at center frequency show nearly isotropic far fields. The maximum gain is measured as 4.8 dB. Promising results of Envelope Correlation Coefficient and gain diversity of the design have been achieved. Simulated and measured results are found in good agreement. The fractional bandwidth of antenna is measured as 143.2% which satisfies its ultra-wide band response.

Microstrip Four-Way Reconfigurable Single/Dual/Wideband Filtering Power Divider With Tunable Frequency, Bandwidth, and PDR

Abstract: In this paper, a microstrip reconfigurable four-way filtering power divider (FPD) with tunable center frequency (CF), bandwidth (BW), and power division ratio (PDR) is presented. A novel coupling scheme is proposed based on four stub-loaded quad-mode resonators (SL-QMRs), two three-line coupled structures, and two quarter-wavelength transformers, which can achieve tunable CF, BW, PDR, and wide isolation BW. Switchable single/dual/wideband filtering response and the CF and BW of a dual-band FPD can be tuned by controlling the varactor diodes loaded onto the open-ends of SL-QMRs. Meanwhile, the PDR is controlled by varying the coupling strength between the center line and sidelines of a three-line coupled structure. Compared with the conventional wideband FPDs, the capacitor loaded onto the parallel coupled line of two outputs enlarges the coupling, which can improve the return loss and, thus, relieve the limitation of the line space. Based on the coupled resonator theory, the parameters of the resonators and coupling sections are analytically determined. For the dual-band FPD, the measured results show that the 3-dB fractional BW of the lower passband can be tuned from 23.4% to 30.9%, while the one of the upper passbands is tuned from 12.3% to 18.5%. The measured CF for the upper passband can be tuned independently from 1.98 to 2.21 GHz, while the lower one remains fixed. Then, the measured PDR is controlled from 1:1:1:1 to 1:2:1:2. The proposed four-way reconfigurable FPD exhibits switchless single/dual/wideband filtering responses, high isolation level, wide isolation BW, and the control of CF, BW, and PDR.

Compact dual-band monopole antenna with defected ground plane for Internet of things

Abstract: Internet of things (IoT) is a complex network of physical objects capable of wirelessly communicating with each other. For implementing such an enormous network, the authors design a compact dual-band antenna with simple structure. By folding the radiating element and resetting the ground plane, the whole size of the designed antenna is only 14 mm × 14 mm same as a thumbnail, which makes the designed antenna easy to fabricate. The fabricated antenna can operate (return loss S 11 <;-10 dB) at two operating bands of 3.4-3.6 GHz for 5G and 5.725-5.825 GHz for 5.8G Wi-Fi, which means it is able to connect the IoT nodes to the Internet through 5G and Wi-Fi network. Simulation and measured results demonstrate that (i) folding the L-shaped stub into U-shaped can reduce the dimension of antenna, and resetting the ground plane structure to parallel to the feed-line can achieve better impedance matching between the designed antenna and the sub-miniature-A (SMA) connector in both operating bands; (ii) the fabricated antenna is able to fully cover the operating bands of 5G at 3.4-3.6 GHz and Wi-Fi at 5.725-5.825 GHz, and can achieve nearly omnidirectional radiation patterns over the two operating bands.

Reliable and Compact 3- and 4-Bit Phase Shifters Using MEMS SP4T and SP8T Switches

Abstract: This paper presents radio frequency (RF) micro-electromechanical system-based 3- and 4-bit phase shifters using single-pole-four-throw (SP4T) and single-pole-eight-throw (SP8T) switches. The design is fabricated on $635~\mu \text{m}$ alumina substrate using a surface micromachining process. SP4T and SP8T switches demonstrate measured return loss of >16 dB, worst case insertion loss of 1.66 dB, and isolation of >13.6 dB up to 40 GHz. Total area of the SP4T and SP8T switches is 0.98 mm2 and 1.66 mm2, respectively. Switches are capable of handling 1 W of incident RF power and can sustain up to 1 billion cycles at 85°C. Finally, 3- and 4-bit phase shifters deliver measured return loss of >12 dB, average insertion loss of 1 billion cycles with 0.1 W of power in cold switching. In addition, phase shifters also worked satisfactory up to >400 million cycles with 0.5 W of power at 85 °C in hot switching condition. Devices were enclosed within a low-cost package and characterized them systematically. [2017-0104]

Compact Design of Planar Quadrature Coupler With Improved Phase Responses and Wide Tunable Coupling Ratios

Abstract: This paper presents a compact planar tunable quadrature coupler with improved phase responses. Wide coupling-tuning ratio is achieved by using two varactors loaded on the center of the transmission lines of the modified coupler. Closed-form equations are derived for design parameters. For verification, a 1-GHz tunable coupler is designed and measured. The measured results agree well with the simulated ones. The measured power-dividing ratio can be tuned in a range from 16.2 to −35 dB (from 42 to 3.2E-4) with better than 20-dB return loss and isolation, while the phase imbalance is smaller than 10°. The coupler size is $0.21\lambda \text{g}\,\,\times \,\,0.08\lambda \text{g}$ and reduced by 73.1% compared with the conventional branch-line coupler. The theoretical analysis shows that the phase imbalance and insertion loss are mostly caused by the loss from varactors. Then, a tunable coupler with improved phase and loss responses is proposed, where the additional phase difference and insertion loss resulting from the varactors are compensated for by introducing a negative resistance from the negative impedance converter. Measured results of a demonstrative 1-GHz coupler show a power-dividing ratio tuning range from 24.4 to −22.2 dB (from 275.4 to 6E-4) while maintaining 20-dB return loss and isolation. The phase imbalance is smaller than 1° and the insertion loss is improved by 1 dB and nearly close to theoretical values across the tuning range.

Four-Way Microstrip Lumped-Element Reconfigurable Dual-Mode Filtering Power Divider

Abstract: In this paper, a novel four-way microstrip lumped-element reconfigurable dual-mode filtering power divider (FPD) is proposed. The two operating states are a four-way FPD with constant return loss, and a stopband filter (SBF) with high isolation, respectively. This switchless two operating states can be switched by selecting appropriate voltage without using switches. The tunable filtering response of four-way FPD based on a novel coupling scheme is realized by two pairs of varactor-tuned LC resonators. The measured four-way FPD can be tuned from 0.98 to 2.08 GHz with return loss better than 18 dB. Its frequency tuning range (FTR) is 72%. The measured isolation is better than 19.5 dB from dc to 5.7 GHz. Apart from the bandpass FPD application, the proposed circuit can also be utilized as an SBF, which is different that of conventional SBF by tuning off diodes to obtain isolation. By staggering the resonant frequencies of four lumped-element resonators and decrease mutual coupling between resonators, an SBF with high isolation can be obtained between two nonadjacent ports. The measured isolation is better than 40 dB from dc to 6 GHz and better than 45 dB from 1.1 to 4.8 GHz. The proposed four-way reconfigurable dual-mode FPD exhibits wide isolation bandwidth and FTR, good return loss, high isolation level, and compact size.

Proposal and Synthesis Design of Wideband Filtering Differential Phase Shifters With a Pair of Out-of-Band Transmission Zeroes

Abstract: In this paper, a new class of wideband filtering phase shifters with a pair of controllable out-of-band transmission zeroes is presented for the first time. The proposed wideband filtering differential phase shifter consists of two stub-loaded multimode resonators (SLMMR) in the main and reference branches, which can provide a constant phase shift and self-realized generalized Chebyshev filtering function with controllable transmission zeroes by properly setting the impedance ratio $R_{\mathrm {z}}$ of the loaded stub. On the one hand, the prescribed phase shift value, phase deviation, and phase shift bandwidth are deduced that basically dominated by resonant modes of SLMMR together with electrical lengths of the phase-shifting lines. On the other hand, the phase properties of transmission zeroes are systematically investigated to demonstrate that they arouse little effect on the phase shift performance, but highly improve the frequency selectivity in theoretical analysis. Based on the presented synthesis method which simultaneously considers wideband phase shift and bandpass filtering function, the circuit parameters of the entire proposed phase shifter can be synthesized with prescribed phase shift value, phase deviation, bandwidth, return loss, and transmission zero positions. Besides, the phase shift and return loss bandwidth can be determined in the design process. As design examples, two 90° wideband filtering phase shifters with different specifications are synthesized, designed, and fabricated to validate our proposed approach.

Efficient Millimeter-Wave Antenna Based on the Exploitation of Microstrip Line Discontinuity Radiation

Abstract: In this paper, a new design perspective utilizes microstrip line discontinuities radiation losses to create an efficient, high-gain millimeter-wave low-profile antenna at 60 GHz. A very compact structure with dimensions of $1.14 \lambda _{o} \times 0.82 \lambda _{o}$ and a substrate thickness of $0.0508 \lambda _{o}$ is proposed. A gain of 11.5 dBi boresight and a 10 dB return loss relative bandwidth of 3.66% (equivalent to 2.2 GHz of bandwidth) have been achieved. Qualitative analysis with simple transmission line theory was used to model the structure. An increase in the relative bandwidth to 11.67%, covering the 60 GHz ISM band (57–64 GHz), has been achieved by tuning the antenna to resonate at multiple resonances within the band of interest. A very high efficiency of 98% has been achieved. The proposed antenna possesses a significant advantage, where it can be employed in a linear antenna array, with a center-to-center distance between adjacent elements greater than half of the free-space wavelength, without producing grating lobes, this reflects positively on reducing the mutual coupling between elements, and gives higher flexibility in the design of feeding network.

Dual-Band Dual-Sense Circularly Polarized Substrate Integrated Waveguide Antenna

Abstract: A dual-band dual-sense circularly polarized (CP) antenna is presented in substrate integrated waveguide technology. The proposed antenna consists of four V-shaped asymmetrical resonators that are placed on a circular substrate symmetrically with respect to its center. The antenna is excited by a probe on the central axis. A dual-band CP antenna is designed and fabricated. The antenna provides left-hand circular polarization (LHCP) in the lower band and right-hand circular polarization (RHCP) in the upper band. Total size of the antenna is 1963.5 mm2 on a 0.787 mm thick RT/Duroid 5880 substrate. Measured axial ratios are below 3 dB over 8.78–8.90 and 9.52–9.66 GHz. Over the bands, the return loss is more than 10 dB. Measured cross-polarization levels are 31.1 and 24.65 dB, and front-to-back ratios are 14.93 and 18.35 dB over the LHCP and RHCP bands, respectively. Depending on application requirements, the band ratio can be tuned. Also, the sense of polarization can be interchanged. The antenna does not use any ground plane perturbation. Thus, it can be directly attached to a microwave circuit.