Showing papers on "Microstrip published in 2016"

Microstrip Antennas The Analysis And Design Of Microstrip Antennas And Arrays

Abstract: Description: Electrical Engineering/Antennas and Propagation Microstrip Antennas The Analysis and Design of Microstrip Antennas and Arrays Microstrip Antennas contains valuable new information on antenna design and an excellent introduction to the work done in the microstrip antenna area over the past 20 years. The articles are well–chosen and (are) complete with practical design information that is very useful for the working engineer. Stuart Long, University of Houston The editors have done an outstanding job in assembling this updated reprint book. It is a welcome addition to the list of books on microstrip antennas. There is no doubt that it will be a valuable source of information for graduate students, engineers and researchers the original articles are written lucidly and are very informative, and the reprint articles are well chosen. Kai Fong Lee, The University of Toledo Complete with an up–to–date tutorial overview of the field and substantial new, introductory material for each topic, Microstrip Antennas combines in one source a selection of today’s most significant and useful articles on microstrip and antenna design. Eminent experts David M. Pozar and Daniel H. Schaubert guide you through:

Submersible Printed Split-Ring Resonator-Based Sensor for Thin-Film Detection and Permittivity Characterization

Abstract: A split-ring resonator (SRR)-based sensor for the detection of solid thickness and relative permittivity characterization of solid and liquid materials is proposed. The structure is composed of two SRRs hosted in a microstrip transmission line. The sensing principle is based on the detection of the notch introduced by the resonators in the transmission coefficient. Hence, a frequency shift of the notch is related to a change in the effective permittivity of the structure when the sensor is covered with any solid or liquid material. A complete characterization of the sensor, for the three proposed applications, is performed through simulations. Finally, all simulated results are corroborated with measurements. The proposed sensor is implemented in single-layer printed technology, resulting in a low-cost and low-complexity solution. It presents real-time response and high sensitivity. Moreover, it is fully submersible and reusable.

Splitter/Combiner Microstrip Sections Loaded With Pairs of Complementary Split Ring Resonators (CSRRs): Modeling and Optimization for Differential Sensing Applications

Abstract: This paper focuses on the analysis of splitter/ combiner microstrip sections where each branch is loaded with a complementary split ring resonator (CSRR). The distance between CSRRs is high, and hence, their coupling can be neglected. If the structure exhibits perfect symmetry with regard to the axial plane, a single transmission zero (notch) at the fundamental resonance of the CSRR, arises. Conversely, two notches (i.e., frequency splitting) appear if symmetry is disrupted, and their positions are determined not only by the characteristics of the CSRRs but also by the length of the splitter/combiner sections. A model that includes lumped elements (accounting for the CSRR-loaded line sections) and distributed components (corresponding to the transmission lines) is proposed and used to infer the position of the transmission zeros. Frequency splitting is useful for the implementation of differential sensors and comparators based on symmetry disruption. Using the model, the length of the splitter/combiner sections necessary to optimize the sensitivity of the structures as sensing elements is determined. Parameter extraction and comparison with electromagnetic simulations and measurements in several symmetric and asymmetric structures is used to validate the model. Finally, a prototype device sensor/comparator based on the proposed CSRR-loaded splitter/combiner microstrip sections is presented.

Multifunctional Microstrip Array Combining a Linear Polarizer and Focusing Metasurface

Abstract: Although microstrip reflectarrays/transmitarrays have been extensively studied in the past decades, most previous designs were confined to monofunctional operations based on either transmission or reflection In this communication, we propose a scheme to design multifunctional arrays that can simultaneously exhibit the functionalities of a reflectarray and a transmitarray on the basis of the appealing feature of a polarizer we discovered (ie, constant phase difference between its cross-polarization transmission and copolarization reflection within a broadband) To demonstrate the proposed scheme, we designed and fabricated a multifunctional device comprising a $15 \times 15$ array of twisted complementary dual-split ring resonators, each carefully designed to exhibit the desired transmission phase satisfying a parabolic distribution Feeding the device by a Vivaldi antenna at its focus, we numerically and experimentally demonstrated that our system functioned as a directive emitter working in a transmission/reflection mode for cross-polarization/copolarization radiation at low/high frequencies, and it can radiate directively in both directions with different polarizations at intermediate frequencies The half-power beamwidth of the array antenna was $\sim 15^{\circ }$ , which is 40° narrower than that of a bare Vivaldi antenna Moreover, the gain was higher than 13 dB in all cases studied, which is at least 7 dB higher than that of the Vivaldi antenna

A Compact Microstrip-Fed Patch Antenna With Enhanced Bandwidth and Harmonic Suppression

Abstract: A single-layer microstrip-fed patch antenna with capabilities of both bandwidth enhancement and harmonic suppression is proposed. For this purpose, a pair of $\lambda $ /4 microstrip-line resonators is introduced and coupled in proximity to a rectangular patch. The wideband property can be obtained by making effective use of the two resonances introduced by the radiating patch and nonradiating $\lambda $ /4 resonators. Different from other reported dual-resonance patch antennas, the proposed antenna does not require the electrically thick substrate, so it has attractive low-profile property. Thanks to the good features of $\lambda $ /4 resonators and capacitive feeding scheme, harmonic radiating modes of the patch antenna can be significantly suppressed as highly demanded in modern highly integrated communication systems. The working principle, equivalent circuit, and design procedure are extensively described. Finally, a prototype antenna operating at 4.9 GHz is designed and fabricated. The measured results show that its bandwidth is 2.7 times wider than that of the traditional insert-fed patch counterpart, and the harmful spurious radiation from other higher order radiating modes has been effectively suppressed.

Low-Loss Spoof Surface Plasmon Slow-Wave Transmission Lines With Compact Transition and High Isolation

Abstract: The symmetric spoof surface plasmon (SSP)-based slow-wave transmission line (SW-TL) with compact transition, low ohmic loss, and low crosstalk between SW-TLs is proposed and investigated. First, the SSP cells are modeled by equivalent circuit elements. The proposed equivalent circuit model is appealing for the integration of SW-TLs with other microwave circuits. With the symmetricity, the SW-TLs are readily realized by a compact mode converter providing gradual impedance, momentum, and polarization matching from guided waves to spoof microwave plasmons. Then, simulation studies and experiments verify that the proposed SSP SW-TL features as low as half the ohmic loss of the traditional counterparts. After that, the low mutual coupling between the proposed SSP SW-TLs is numerically and experimentally substantiated and showed to be up to 10 dB lower than that between conventional microstrip TLs. The proposed low loss, highly isolated and compact SW-TL along with the reliable circuit model enables the further exploitation of promising spoof plasmon modes in microwave technology.

Absorptive frequency selective surface using parallel LC resonance

Abstract: A frequency selective surface with absorptive/ transmissive property is represented. It allows waves at high frequency around 10 GHz to transmit with very low insertion loss by using the resonance between a parallel microstrip LC structure. It also possesses a wide absorption over lower band by inserting lumped resistors into elements. The absorption band is over 3–9 GHz. A prototype is fabricated and its absorptive/ transmissive performance is measured.

Design of Compact F-Shaped Slot Triple-Band Antenna for WLAN/WiMAX Applications

Abstract: This communication presents a small, low-profile planar triple-band microstrip antenna for WLAN/WiMAX applications. The goal of this communication is to combine WLAN and WiMAX communication standards simultaneously into a single device by designing a single antenna that can excite triple-band operation. The designed antenna has a compact size of $19 \times 25\;\text{mm}^{2}$ ( $0.152 \lambda_{0}\;\times 0.2 \lambda_{0}$ ). The proposed antenna consists of F-shaped slot radiators and a defected ground plane. Since only two F-shaped slots are etched on either sides of the radiator for triple-band operation, the radiator is very compact in size and simple in structure. The antenna shows three distinct bands I from 2.0 to 2.76, II from 3.04 to 4.0, and III from 5.2 to 6.0 GHz, which covers entire WLAN (2.4/5.2/5.8 GHz) and WiMAX (2.5/3.5/5.5) bands. To validate the proposed design, an experimental prototype has been fabricated and tested. Thus, the simulation results along with the measurements show that the antenna can simultaneously operate over WLAN (2.4/5.2/5.8 GHz) and WiMAX (2.5/3.5/5.5 GHz) frequency bands.

Fixed-Frequency Beam Steering of Microstrip Leaky-Wave Antennas Using Binary Switches

Abstract: This paper presents a novel, easy-to-fabricate and operate, single-layer leaky-wave antenna (LWA) that is capable of digitally steering its beam at fixed frequency using only two values of bias voltages, with very small gain variation and good impedance matching while scanning. Steering the beam of LWAs in steps at a fixed frequency, using binary switches, is investigated, and a new half-width microstrip LWA (HW-MLWA) is presented. The basic building block of the antenna is a reconfigurable unit cell, switchable between two states. A macrocell is created by combining several reconfigurable unit cells, and the periodic LWA is formed by cascading identical macrocells. A prototype HW-MLWA was designed, fabricated, and tested to validate the concept. To achieve fixed-frequency beam scanning, a gap capacitor in each unit cell is independently connected or disconnected using a binary switch. By changing the macrocell states, the reactance profile at the free edge of the microstrip and hence the main beam direction is changed. The prototyped antenna can scan the main beam between 31° and 60° at 6 GHz. The measured peak gain of the antenna is 12.9 dBi at 6 GHz and gain variation is only 1.2 dB.

Mutual Coupling Reduction for High-Performance Densely Packed Patch Antenna Arrays on Finite Substrate

Abstract: This paper reports on an effective mutual coupling suppression technique in which a metamaterial superstrate is placed in between the elements of densely packed microstrip phased array. Modified complementary split ring resonators are printed on the decoupling superstrate slab which caters for both surface and space wave effects. A detailed analysis of this proposed scheme is carried out on a low as well as on a high-permittivity substrate. Coupling suppression of 27 and 11 dB is achieved experimentally on the low- and high-permittivity substrates, respectively, with an element separation of $\lambda_{o}/8$ . The design is compact and easy to realize and it removes drawback of poor front-to-back ratio previously reported in other decoupling techniques. In addition to high-coupling suppression, the decoupling slab can be added or removed in real time which makes this technique versatile for various applications having stringent performance requirements.

Design of a Reconfigurable Miniaturized Microstrip Antenna for Switchable Multiband Systems

Abstract: In this letter, a novel printed frequency-reconfigurable microstrip square slot antenna for switchable Bluetooth, WiMAX, and WLAN applications is presented. The proposed antenna has a small size of $20 \times 20~\hbox{mm}^2$ in order to be able to cover lower frequencies; as for Bluetooth applications, miniaturization techniques such as modification of the ground plane and inserting an adjustable backplane cross-shaped sleeve have been employed. Moreover, by implementation of p-i-n diodes within the antenna structure, switchable frequency responses are achieved. The presented antenna has a small size while providing suitable switchable radiations at 2.3–2.51 GHz $({\rm BW} = 8.7\%)$ Bluetooth, 3.35–3.75 GHz $({\rm BW} = 11.2\%)$ WiMAX, and 4.95–5.53 GHz $({\rm BW}=11\%)$ WLAN.

Design of rectangular microstrip patch antenna

Abstract: The purpose of this paper is to design a microstrip rectangular antenna in Advance Design System Momentum (ADS). The resonant frequency of antenna is 4.1GHz. The reflection coefficient is less than −10dB for a frequency range of 3.1GHz to 5.1 GHz. The proposed rectangular patch antenna has been devise using Glass Epoxy substrate (FR4) with dielectric constant (er = 4.4), loss tangent (tan δ) equal to 0.02. This rectangular patch is excited using transmission lines of particular length and width. Various parameters, for example the gain, S parameters, directivity and efficiency of the designed rectangular antenna are obtained from ADS Momentum.

Gain Enhancement of Circularly Polarized Dielectric Resonator Antenna Based on FSS Superstrate for MMW Applications

Abstract: In this communication, a high gain circularly polarized (CP) dielectric resonator antenna (DRA) is proposed. The radiating DR is coupled to a $50~\Omega $ microstrip line through an X-shaped slot etched off the common ground plane. Using a frequency selective surface superstrate layer, a gain enhancement of 8.5 dB is achieved. A detailed theoretical analysis is given and used to optimize the superstrate size and the air gap height between the antenna and superstrate layer. The proposed DRA is designed, simulated, implemented, and tested. The high gain CP DRA has the potential to be used for millimeter wave wireless communication and imaging systems.

Modeling and Applications of Metamaterial Transmission Lines Loaded With Pairs of Coupled Complementary Split-Ring Resonators (CSRRs)

Abstract: This letter is focused on the modeling, analysis, and applications of microstrip lines loaded with pairs of electrically coupled complementary split-ring resonators (CSRRs). Typically, these epsilon-negative (ENG) metamaterial transmission lines are implemented by loading the line with a single CSRR (etched beneath the conductor strip) in the unit cell. This provides a stopband in the vicinity of the CSRR resonance. However, by loading the line with a pair of CSRRs per unit cell, it is possible to either implement a dual-band ENG transmission line (useful, for instance, as a dual-band notch filter), provided the CSRRs are tuned at different frequencies, or to design microwave sensors and comparators based on symmetry disruption (in this case by using identical CSRRs and by truncating symmetry by different means, e.g., asymmetric dielectric loading). The design of these CSRR-based structures requires an accurate circuit model able to describe the line, the resonators, and the different coupling mechanisms (i.e., line-to-resonator and inter-resonator coupling). Thus, a lumped element equivalent circuit is proposed and analyzed in detail. The model is validated by comparison to electromagnetic simulations and measurements. A proof-of-concept of a differential sensor for dielectric characterization is proposed. Finally, the similarities of these structures with coplanar waveguide transmission lines loaded with pairs of SRRs are pointed out.

Wideband, Wide-Scan Planar Array of Connected Slots Loaded With Artificial Dielectric Superstrates

Abstract: Microwave broadband wide-scan antenna arrays are typically implemented resorting to vertical arrangements of printed circuit boards (PCBs). Here, we propose a planar solution realized with a single multi-layer PCB, with consequent reduction in cost and complexity of the array. It consists of an array of connected slots backed by a metallic reflector and loaded with superstrates. Artificial dielectric layers (ADLs) are used in place of real dielectrics to realize the superstrates, as they are characterized by very low surface-wave losses. For the unit-cell design, we developed an analysis tool based on closed-form expressions and thus requiring minimal computational resources. Finite-array simulations are also performed by generalizing the analysis method to account for the truncation effects. The presence of the ADL superstrate allows reducing the distance between the array plane and the backing reflector while maintaining good matching performance. A realistic feed structure is also proposed, which consists of a microstrip line connected to a coaxial feed. Such a solution does not require balanced-to-unbalanced transitions, which often limit the achievable bandwidth. The proposed structure achieves in simulations more than an octave bandwidth (6.5–14.5 GHz), within a scanning range of $\pm 50$ ° in all azimuth planes.

Transmission Lines Loaded With Pairs of Stepped Impedance Resonators: Modeling and Application to Differential Permittivity Measurements

Abstract: Differential techniques are widely used in communication and sensor systems, as these techniques have been shown to improve the performance. This paper shows how differential sensing of permittivity can be conducted in a simple way. For that purpose, a microstrip line loaded with a pair of stepped-impedance resonators is used in two different resonator connections: parallel and cascade. Each resonator is individually perturbed dielectrically so that: 1) when the two individual permittivities are identical, the structure exhibits a single resonance frequency and 2) when the permittivities are different, resonance frequency splitting occurs, giving rise to two resonances (all these resonances are seen in the form of transmission zeroes). The two sensing approaches are successfully validated through electromagnetic simulations and experiments. By virtue of a differential measurement, robustness against changing ambient factors that may produce sensor miscalibration is expected.

Electrically Driven and Thermally Tunable Integrated Optical Isolators for Silicon Photonics

Abstract: Optical isolators are required to block undesired reflections in many photonic integrated circuits (PICs), but the performance of on-chip isolators using the magneto-optic effect has been limited due to high loss of such materials. Moreover, they require precise positioning of a permanent magnet close to the chip, increasing footprint and impeding packaging. In this paper, we propose an optical isolator on the silicon-on-insulator platform with record performance and without the use of any external permanent magnets. A metallic microstrip above the bonded silicon microring (MR) is used to generate the magnetic field required for the nonreciprocal behavior. Simultaneously, the microstrip can be used to provide 0.6 nm of thermal tuning while preserving over 20 dB of isolation. We measure 32 dB of isolation near 1555 nm with only 2.3 dB excess loss in a 35 μm radius MR. The tunability, compactness, and lack of permanent magnets suggest this device is a major step towards integration in PICs.

Dual-Band Circularly Polarized Split Ring Resonators Loaded Square Slot Antenna

Abstract: A dual-band circularly polarized (CP) microstrip line fed slot antenna using a set of split ring resonators (SRRs) is proposed in this communication. Outer ring connected SRRs are placed on the back side of the slot to create the CP upper band. Diagonally opposite corners of the slot are truncated, which together with the SRRs give CP response in the lower band. The proposed dual-band CP antenna provides design flexibility to control the resonance frequency and sense of polarization at the dual bands, independently. The proposed antenna is designed to operate at 3.1 and 4.7 GHz, which is fabricated and tested. The experimental results show the −10-dB impedance bandwidths of 400 MHz in both the bands and the 3-dB axial ratio bandwidth of 3.1% (from 3.05 to 3.15 GHz) and 4.2% (from 4.65 to 4.85 GHz) in lower and upper bands, respectively. Finally, a metallic cavity is used with the antenna to achieve a unidirectional radiation pattern with front-to-back ratio of more than 15 dB without affecting the impedance bandwidth and CP performance of the antenna.

Characteristic Mode Analysis of a Class of Empirical Design Techniques for Probe-Fed, U-Slot Microstrip Patch Antennas

Abstract: In this paper, characteristic mode analysis (CMA) of three empirical design techniques for the probe-fed, symmetrically located, U-slot microstrip patch antenna, on a single-layer grounded substrate, is presented with supporting experimental data. The first method, resonant frequency (ResF), utilizes the existence of the four distinct ResFs, while the second one, dimensional invariance (DI), relies on the property of DI, for the design of the U-slot microstrip patch. In both these methods, the optimization of the probe location is necessary for further enhancement of the 10-dB return loss bandwidth. The third method, dimensionally invariant ResF, that optimally combines the features of the previous two is developed here and shown to yield better bandwidth performance with minimal or no probe location optimization, and hence is superior to the other two for rapid prototyping. CMA is carried out for critical parameters, such as substrate electrical thickness, slot width, probe radius, and feed location variations, to assess their dominant influence on the characteristics of the U-slot microstrip patch antenna.

Compact Low-Profile Circularly Polarized Fabry–Perot Resonator Antenna Fed by Linearly Polarized Microstrip Patch

Abstract: A novel compact low-profile circularly polarized Fabry-Perot resonator (CP-FPR) antenna fed by a linearly polarized microstrip patch tilting by 45 ° with respect to the axes is presented. The FP cavity consists of a partially reflective surface formed by cross-slot frequency selective surface (FSS) and a nonstandard artificial magnetic conductor (AMC) acting as reflective ground plane. Its profile is reduced to a quarter of a wavelength. For verification, a prototype antenna is designed and simulated by HFSS. Reasonable agreement between the simulated and measured results is observed. The prototype has a common frequency bandwidth of 6.4% for S 11 ≤ - 10 dB, gain-drop ≤ 3 dB, and axial ratio ≤ 3 dB.

Novel Printed Filtenna With Dual Notches and Good Out-of-Band Characteristics for UWB-MIMO Applications

Abstract: A novel filtenna with good out-of-band characteristics is presented for UWB-MIMO applications. Aimed to work within the frequency range of 3.1-10.6 GHz, a band-pass filter (BPF), consisting of shunt short-circuited stubs and three inter digital edge coupled microstrip lines, are incorporated in the feedline of the printed antenna to achieve an efficient frequency cutoff and improve the selectivity. A complementary split-ring resonator (CSRR) is incorporated into the patch to achieve the dual notched band charactersitics. The measured impedance bandwidth ( $S_{11} dB) is from 3.1-10.65 GHz, except the dual notched bands of 3.35-3.55 GHz and 5.65-5.95 GHz. The measured Envelope Correlation Coefficient (ECC) is less than 0.002.

Wideband Microstrip Leaky-Wave Antennas With Two Symmetrical Side Beams for Simultaneous Dual-Beam Scanning

Abstract: Wideband microstrip leaky-wave antennas (LWAs) that radiate two symmetrical side beams are described. The two beams are steered simultaneously by sweeping the operating frequency. To achieve this, the second higher order mode of the microstrip is excited. Two electric field nulls are created between the microstrip and the ground plane using via arrays to suppress lower order modes. To test the concept, one of the antenna designs was prototyped. The prototyped antenna is capable of steering two symmetrical beams within a range of 37° when frequency is swept between 6.92 and 8.75 GHz. The measured peak gain of the antenna is 12.7 dBi and the variation of gain from 6.92 to 8.75 GHz is 3.1 dB. The measured 10-dB return loss bandwidth is 23%, which is very large for a dual-beam microstrip LWA. Such a wide impedance bandwidth is essential to achieve beam scanning over a wide angular range by sweeping frequency. Another advantage is that this single-layer antenna is easy to fabricate.

Smaller-loss planar SPP transmission line than conventional microstrip in microwave frequencies

Abstract: Transmission line is a basic component in all passive devices, integrated circuits, and systems. Microstrip is the most popular transmission line in the microwave and millimeter-wave frequencies, and has been widely used in current electronic devices, circuits, and systems. One of the important issues to be solved in such applications is the relatively large transmission loss of microstrip. Here, we propose a method to reduce the loss of microwave transmission line based on the designable wavenumber of spoof surface plasmon polaritons (SPPs). Using this characteristic, we analyze and experimentally demonstrate the low-loss feature of the SPP transmission line through the perturbation method and S-parameter measurements, respectively. Both simulation and experimental results show that the SPP transmission line has much smaller transmission loss than traditional microstrip with the same size in the microwave frequencies. Hence, the spoof SPP transmission line may make a big step forward in the low-loss circuits and systems.

Microwave gas sensing with a microstrip interDigital capacitor: Detection of NH3 with TiO2 nanoparticles

Abstract: This work presents new developments in the microwave transduction and its application to gas sensors. Microwave measurements were extended to reflection/transmission coefficients through the use of a microstrip interdigital capacitor design. A sensitive layer composed of commercial TiO2 nanoparticles was deposited on the sensor surface, in order to detect the ammonia target gas. A complete analysis methodology is proposed. It allows to identify without ambiguity all the sensor frequencies of interest, as well as a full characterization of usual gas sensor parameters such as reproducibility, stability, response time, etc. Furthermore, it involves a new method of representation which significantly limits the amount of unexploited data collected during microwave measurements. The proposed sensor exhibits a strong correlation between response values and injected ammonia concentration between 100 and 500 ppm, with a good reversibility and stability of the measure.

Microstrip Patch versus Dielectric Resonator Antenna Bearing All Commonly Used Feeds: An experimental study to choose the right element.

Abstract: Microstrip patches and dielectric resonators (DRs) are two low-profile variants of modern microwave and wireless antennas. However, the DR antenna (DRA) is relatively new and still passing through the stages of development. Both variants are quite similar in terms of performance and characteristics. This article focuses on a meaningful comparative study where we have considered all commonly used feed mechanisms such as coaxial probe, microstrip line, and rectangular aperture for both antennas operating near the same frequency. Circular geometry, i.e., cylindrical DRA (CDRA) and circular microstrip patch antenna (CMPA), have been chosen, and a systematic investigation based on thorough experiments has been executed. Multiple sets of prototypes have been fabricated and measured at 4 GHz. All available data have been furnished and compared, indicating relative advantages and disadvantages. This comparative study should provide qualitative and quantitative instructions to a designer for choosing the right element and corresponding feed based on design requirement and feasibility.

Dual-Band Filtering Power Divider With High Selectivity and Good Isolation

Abstract: A novel microstrip dual-band filtering power divider (FPD) is presented in this letter. By introducing a proper coupling topology between the quarter-wavelength ( $\lambda $ /4) short-ended microstrip line and two multi-mode resonators, the dual-band FPD is constructed. Meanwhile, good isolation of this FPD is attained by installing an isolation resistor between the resonators. Additionally, two $3\lambda $ /4 open-ended stubs are attached in the output coupled lines to improve its frequency selectivity and obtain a wide upper stopband. For validation, a prototype FPD operating at 1.57 and 2.89 GHz is designed, fabricated and measured. Both the simulated and measured results are in good agreement. Results indicate that the proposed FPD exhibits not only a sharp frequency selectivity and good harmonic suppression with the help of the six inherent transmission zeros, but also better than 21 dB isolation within the entire dual operation bands.

Asymmetric Geometry of Defected Ground Structure for Rectangular Microstrip: A New Approach to Reduce its Cross-Polarized Fields

Abstract: A shaped defected ground structure (DGS) that is asymmetric in a specific radiating plane of a microstrip element has been explored with a view to addressing the cross-polarization (XP) issues. The asymmetric configuration has been conceived from an insight of the inherent asymmetry of the modal fields underneath a probe-fed microstrip patch and has been experimentally demonstrated as the best possible design compared to its predecessors in terms of the reduction in XP fields, angular span of suppression around boresight, and the space occupied by the defects. Different orientations of the defects with reference to the patches of different aspect ratio values have been thoroughly examined. More than 28-dB isolation between co-pol and cross-pol has been achieved over 190° angular range, which is indeed 140° more if compared with a conventional ground plane. Its superior characteristics with respect to the earlier designs have also been documented.

Single-conductor co-planar quasi-symmetry unequal power divider based on spoof surface plasmon polaritons of bow-tie cells

Abstract: In this paper, the spoof surface plasmon polaritons (SSPPs) transmission line (TL) of periodical grooved bow-tie cells is proposed. The complex propagation constant and characteristic impedance of the SSPPs TLs and microstrip lines (MLs) are extracted using the analytical method of generalized lossy TL theory. The properties of the SSPPs TLs with different substrates and the same geometrical configuration are experimented. Then, for comparison, two ML counterparts are also experimented, which shows that the SSPPs TL is less sensitive to the thickness, dielectric constant and loss tangent of the chosen substrate below the cutoff frequency, compared with the ML ones. The single-conductor co-planar quasi-symmetry unequal power divider based on this SSPPs TL is presented in microwave frequencies. For experimental validation, the 0-dB, 2-dB, and 5-dB power dividers are designed, fabricated, and measured. Both simulated and measured results verify that the unequal power divider is a flexible option, which offers massive advantages including single-conductor co-planar quasi-symmetry structures, wide-band operation, and convenient implementations of different power-dividing ratios. Hence, it can be expected that the proposed unequal power dividers will inspire further researches on SSPPs for future design of novel planar passive and active microwave components, circuits and systems.

A Novel Single-Fed Wide Dual-Band Circularly Polarized Dielectric Resonator Antenna

Abstract: A new single-fed wide dual-band circularly polarized (CP) dielectric resonator antenna (DRA) is presented in this letter. The DRA is excited by a microstrip line through the narrow underneath rectangular aperture, and its HE 111 and HE 11δ (2 <; δ <; 3 ) modes are utilized for the dual-band design. To achieve CP fields, two notches are truncated from the cylindrical DRA at φ = 45 ° and 225 ° . A pair of equal arc-shaped slots are used to improve the axial-ratio (AR) and impedance bandwidths. The antenna features impedance bandwidths (|S 11 | <; -10 dB ) of 26.25% and 11.17%, and 3-dB AR bandwidths of 15.8% and 5.02% in the lower and upper bands, respectively. To verify the simulation, the antenna is designed and measured. Reasonable agreement between measured and simulated results is obtained.

Fully Printed Gap Waveguide With Facilitated Design Properties

Abstract: An improved concept is introduced to facilitate the design of low-loss planar circuits using printed gap waveguide technology. The method is based on using separate layers to realize the EBG cells and the lines. As a result, the operating bandwidth of the waveguide is increased compared to the printed ridge gap waveguide. Also, the design process is simplified regarding the placement of the cells around the resonators and lines. Measured results of a line with two 90° bends and a quadruplet bandpass filter are presented that prove the concept. A transition to microstrip line is used in order to acquire the ability to use test probe fixture.