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This letter presents a novel millimetre‐wave (mm‐wave) on‐chip substrate integrated waveguide (SIW) filtering crossover using 0.25 µm GaAs pHEMT technology. The design methodology of the proposed crossover is thoroughly illustrated. The proposed filtering crossover employs a dual‐mode cavity with TE102 and TE201 degenerate mode resonances at the intersection, leveraging the degenerate modes for in‐band resonance and inter‐channel isolation. Additionally, four TE101 mode resonant half‐mode SIW cavities are coupled around the dual‐mode cavity to achieve two third‐order bandpass response channels and reduce the overall size. A prototype is designed, analysed, and fabricated to validate the proposed approach, with measured results showing good agreement with simulations. The presented on‐chip SIW filtering crossover offers promising potential for mm‐wave applications, demonstrating the effectiveness of the design methodology and GaAs pHEMT technology integration. [ABSTRACT FROM AUTHOR]

A compact dual‐band bandpass filter (BPF) with high selectivity based on 3D printable groove gap waveguide (GGW) for millimeter application is proposed by the authors. Two stacked dual‐mode GGW resonant cavities including TE102 and TE201 are used to realise a compact structure. The dual‐band bandpass response of the GGW BPF is developed from a split‐type coupling topology which produced two transmission zeros (TZs) between the two passbands. In addition, two TZs are generated outside the two passbands after introducing a source‐load coupling, which achieves a higher frequency selectivity. For verification, a prototype is designed, fabricated and measured. The measured results agree well with the simulated ones, which validates the proposal. [ABSTRACT FROM AUTHOR]

In this study, a direct synthesis approach is proposed to extract the coupling matrix of multi‐port filtering power divider (FPD) with arbitrary phase shift, power division as well as reference impedances, for the first time. This method provides an attractive technique to synthesise a multi‐functional device that combines the characteristics of bandpass filter, multi‐port power divider and ideal phase shifters as well as the impedance matching network, which can effectively diminish the overall size and improve the performance of the microwave front‐end network. A newly defined coupling matrix corresponding to arbitrary multi‐port topologies that introduces ideal phase shift by virtue of constant frequency‐independent reactance at the source and load is developed in FPD synthesis process. The coupling matrix is obtained directly by optimising the presented cost‐function in this paper, avoiding complex similar transformation process of coupling matrix. Finally, several numerical examples of multi‐port FPD with equal/unequal power division ratio, arbitrary phase shift and reference impedances are synthesised to well verify the proposed synthesis method, and a practical example is given to verify the validity of arbitrary phase shift and arbitrary reference impedance. [ABSTRACT FROM AUTHOR]

A new design method of the dual‐band balanced bandpass filter (BPF) using multilayer packaging dual‐mode substrate integrated waveguide (SIW) cavities is proposed. Split‐type coupling topology based on dual‐mode resonators is developed for the design. Firstly, a single‐band balanced filter with perturbed metal vias is designed. The TE201 mode and the TE202 mode perturbed by the metal vias can form a passband. Secondly, an additional metal vias perturbed SIW cavity with the same dual‐mode is placed in the lower layer for the bandstop function. A dual‐band balanced BPF with split‐type coupling topology is successfully realised. Compared with the traditional cascaded single‐mode form, the proposed dual‐mode split‐type design has more compact size and can be more easily extended to multi‐passbands. To verify the proposed method, a dual‐band balanced filter operating at 13.3 and 14.2 GHz is designed, fabricated and measured. The designed dual‐band balanced filter has good filtering performance including differential mode passband transmission and common mode rejection. Measured results show good agreements with simulated ones. [ABSTRACT FROM AUTHOR]

A new method for frequency selective surface (FSS) with high selectivity, namely, filtenna–filtenna (FA-FA)-based technique, is proposed, which consists of two filtering antennas and impedance matching network. Based on the reciprocity theorem, the radiation null of filtenna can provide a stopband of the proposed FSS. In this work, it is validated by using a periodic array of back-to-back magnetoelectronic (ME)-dipole antennas with split-ring resonators (SRRs), and a slotted GND plane is used to connect the two ME-dipole antennas for impedance matching. Bandpass response of the proposed FSS is realized by the intrinsic high-pass characteristic of ME-dipole antennas and the bandstop characteristic of SRRs. Four transmission zeros (TZs) and three transmission poles (TPs) are generated, exhibiting a high-order filtering response. TZs and TPs are analyzed by equivalent circuit model and current distributions. The 3 dB fractional bandwidth (${\mathrm {FBW}}_{\mathrm {3\,dB}}$) of 38.5% in the passband and the 20 dB fractional bandwidths $({\mathrm {FBW}}_{\mathrm {20\,dB}})$ of 8.7% in the lower rejection band and 13.8% in upper rejection band are obtained in this design. Finally, a prototype is fabricated and measured to further validate the proposed FA-FA-based technique. Simulated and measured results show that the proposed FA-FA-based FSS is with the distinct advantages, including wide passband, low profile, tunable TZs, and dual-polarized application, which verifies the proposed method of FSSs. [ABSTRACT FROM AUTHOR]

This communication presents the design of 1 bit coding engineered reflector for wideband monostatic/bistatic radar cross section (RCS) reduction under a wide angle of incidence by redirecting the backscattered electromagnetic (EM) energies into wide and countless angles. The proposed surface can achieve an excellent monostatic/bistatic RCS reduction performance of more than 10 dB over a wide frequency range from 60 to 120 GHz under wide angles of incidence up to 75°. This is achieved by designing a wideband anisotropic polarization rotator unit cell with a relative polarization conversion bandwidth of 66.7% and polarization conversion efficiency of more than 99%. The unit cell and its mirrored version are used to represent the “0” and “1” coding states of an optimized 1 bit coding sequence. The distribution of the “0” and “1” coding states and the dimensions of the anisotropic unit cell are optimized carefully, such that the unit cell will have 180° ± 30° reflection phase difference between the $x$ - and $y$ -axes over the whole three frequency bands (V-, E-, and W-bands) and obtains ultrawideband and wide-angle diffusion scattering patterns under oblique incidence up to 75°. The simulation and experimental results show that the proposed coding engineered reflector has nearly uniform diffusive scattering characteristics under normal and wide-angle off-normal incidences of EM waves up to 75° over the three frequency bands. [ABSTRACT FROM AUTHOR]

A new class of 3-D integrated multiband bandpass filters (BPFs) based on substrate integrated waveguide (SIW) technology is presented in this work, for the first time. Split-type dual-extended doublet (SDED) coupling topologies are developed to propose these BPFs with a desired multiband response by the LEGO-style assembly of planar SIW resonant-mode blocks. These design schemes offer attractive and promising advantages with regard to compact size, low cost, flexible and expandable topology, as well as integration of high-density integrated circuits. For demonstration, dual- and triple-band BPFs are designed, fabricated, and measured. The measurement results are in good agreement with the simulation ones. Results indicate that the proposals can provide not only nice selective multiband signal transmission in such flexibly extensible topologies with new spatial schemes but also increase space utilization and reduce footprint. [ABSTRACT FROM AUTHOR]

The independent control of two orthogonal polarizations that possess dual functionalities is highly desirable in antenna and wireless communication technologies. Spin-decoupled metasurfaces with integrated dynamic and geometric phases have been proposed to generate two independent right-handed and left-handed circularly polarized (RCP and LCP, respectively) waves. However, the RCP and LCP phases are correlated by a linear equation of the dynamic and geometric phases. In this article, we propose a meta-atom in which the 1 b phase of two orthogonal polarizations can be controlled independently. Moreover, a high-gain broadband millimeter-wave multidimensional metasurface to generate an $x$ -polarized $l=0$ beam with a 10° beam deflection and a $y$ -polarized $l=+1$ beam independently is simulated, fabricated, and tested. The proposed metasurface operating over the frequency range of 16–28 GHz has the maximum gains of 28.7 and 23.8 dBi for the $l=0\,\,x$ -polarized waves and $l=+1\,\,y$ -polarized waves, respectively. Compared with spin-decoupled metasurfaces, the proposed metasurface provides a simpler design process to generate two independent vortex beams for the two orthogonal polarizations. The proposed vortex metasurface also has the advantages of dual polarization, high gain, wide relative bandwidth, and is broadband. The proposed metasurface has potential application in high-capacity communication systems. [ABSTRACT FROM AUTHOR]

A planar bidirectional circularly polarized (CP) antenna using orthogonal magnetic dipoles (OMDs) without an extra phase shift line is proposed in this work. It consists of a rectangular microstrip magnetic dipole antenna (MMDA) and a loop radiator with two arms directly connected to the open edge of MMDA. The working principle is revealed by the equivalent sources model to provide a clear physical insight at first. The theoretical investigations imply that by controlling the width and the feed locations of the loop antenna on the aperture, the phase and magnitude for CP radiation can be realized in both endfire and backfire directions without introducing an additional phase shift line structure. For demonstration, one antenna prototype is designed and fabricated. The experimental results indicate that an overlapping bandwidth of 5.91% from 2.30 to 2.44 GHz is attained. Compared with the counterpart using OMDs, the proposed antenna exhibits a low design complexity and improved gains of 3.56/1.83 dBic in the endfire/backfire directions. [ABSTRACT FROM AUTHOR]

This work proposes a microwave angular displacement sensor with wideband matching based on a wideband impedance transformer. According to the design requirement of the microstrip impedance transformer (load‐to‐source impedance of 250‐to‐50 Ω, centre frequency of 2.40 GHz) with Chebyshev frequency response, the proposed angular displacement sensor is explored for the high bandwidth sensitivity of 11.18 MHz/degree. [ABSTRACT FROM AUTHOR]

Self‐decoupling coupled‐fed patch antennas are designed in this letter. The self‐decoupling mechanism is based on the weak‐field region formed by the T‐shaped probe feed and the radiating patch of the antenna element itself. When another identical antenna element is placed in the weak‐field region, high isolation between the two elements can be achieved without adding extra decoupling structures. To validate the decoupling mechanism, a dual‐element antenna array is initially built and an isolation level of better than 30 dB is achieved over the impedance band of 3.3–3.66 GHz with an element spacing of 0.53λ0. Next, a four‐element multiple‐input multiple‐output (MIMO) linear antenna array is presented to further verify the decoupling method and good isolation performance is also obtained, which demonstrates that the proposed designs are good candidates for 5G MIMO applications. [ABSTRACT FROM AUTHOR]

In this article, a class of wideband bandpass filters (BPFs) using triple-mode coaxial resonators has been introduced. Each triple-mode resonator is utilized with TM010 mode, TE− mode, and TE+ mode orthogonal to each other. Two L-shaped feeding probes and a loading disk are adopted to implement the miniaturization of these wideband BPFs. To observe the degree of miniaturization, we set a design specification of the same fractional bandwidth (FBW) of 40% at the same central frequency of 2.5 GHz. After employing the L-shaped feeding probes and loading disk, the efficient circuit size without cavity thickness is reduced by 80% compared with the triple-mode wideband filter without L-shaped feeding probes and loading disk. In contrast, the unloaded quality factors are slightly changed. In addition, another advantage of this work is that the upper stopband is extended to $2.5f_{0}$. Three experimental wideband BPFs in the large, medium, and small sizes are designed, manufactured, and tested for demonstration. Good agreements are obtained between simulation and experiment. [ABSTRACT FROM AUTHOR]

Transmissive and reflective metasurfaces have been extensively studied for generating an orbital angular momentum (OAM)-carrying beam. However, the existing OAM generators suffer from feed blockage, large profile, OAM mode nonreconfigurable, and narrowband. An OAM generator that integrates multiple functions into a single module is in high demand in OAM-based applications. In this study, we proposed an OAM generator based on a folded reflectarray with high-gain low-profile broadband and programmable characteristics. The proposed multifunctional OAM generator, comprising half the volume of the normal OAM metasurfaces, can generate a high-gain $l=0$ , $l=+1$ , and $l=+2$ OAM-mode-reconfigurable beams with high mode purity over the frequency range of 9.5–10.5 GHz. The proposed OAM generator-integrated multiple functions have potential applications in OAM-based wireless communications and radar detection. [ABSTRACT FROM AUTHOR]

An ultra-wideband (UWB) bandpass-filtering microstrip circuit with an embedded in-band transmission zero (TZ) for co-integrated angular displacement RF sensing is reported. It is based on a two-layer structure that exploits a combination of a UWB transversal filtering section (TFS) with a parallel-coupled-line (PCL) path and a U-shaped slotline acting as the stator and a semi-circular slotline acting as the rotor. As the rotor consisting of a semi-circular slotline rotates, the degree of coupling between the slotline of the stator and the rotor is altered in a contactless fashion, thus varying the stator slotline effective lengths and, hence, the in-band TZ location and its rejection depth that enable to perform the rotation-RF-sensing task. The equivalent circuit model of the engineered dual-functionality UWB bandpass filtering/ angular displacement sensing RF device is provided, together with a numerical/parametric evaluation to study its performance. The sensing capability is analyzed for an example circuit built with a UWB bandpass filtering transfer function centered at 1.8 GHz with a fractional bandwidth of 110%. Furthermore, a proof-of-concept microstrip prototype with an angular rotation range of 90° is developed and tested to validate this approach experimentally. The average frequency sensitivity in terms of the variation of the in-band TZ location is 2.27 MHz/°, showing enhanced linearity and contactless operation as added merits compared with prior-art TFS-based rotational angle sensors. [ABSTRACT FROM AUTHOR]

The novel application of microwave directional couplers to develop angular‐displacement microwave sensors is reported. The proposed sensor approach employs as stator a branch‐line‐type coupler arranged in transversal mode by loading its direct and coupled ports with two distinct‐length open‐ended stubs. Thus, by taking the isolated port of the coupler as the stator output node, a bandpass filtering transfer function with transmission zeros (TZs) is created. Then, a rotor made up of an angularly‐moveable open‐ended stub is attached to a curved section of the longest loading stub of the stator through physical contact, so that their interconnection point varies with the angular‐displacement of the rotor. In this manner, the sensor transfer function is altered with the stub rotation through TZ reallocation, angular‐displacement sensing capabilities are achieved. The theoretical operational foundations of the conceived branch‐line‐coupler‐based microwave angular‐displacement sensor, which features single/multi‐band sensing properties in terms of inter‐TZ spacing and stop band attenuation levels, along with design examples and curves are provided. The extrapolation of this sensor principle to other classes of power‐distribution circuits, such as the rat‐race‐type directional coupler, is also demonstrated. Finally, for experimental‐validation purposes, two 920 MHz microstrip prototypes of the conceived branch‐line‐coupler‐based angular‐displacement microwave‐sensor approach are built and measured. [ABSTRACT FROM AUTHOR]

A novel rotational angle microwave sensor with a high dynamic range and sensitivity for detecting angular displacement is presented. It exploits the spectral separation between two notch frequencies or transmission zeros that are generated in its transfer function, and whose value varies as a function of the rotation angle to be measured. The sensor is based on a bi-path transversal-signal-interference (TSI) circuit configuration that is implemented on microstrip technology, where a rotor comprised of an open-circuit-ended stub is loaded onto a stator of this transversal circuit with equal-length electrical paths. The mechanical rotation of the rotor changes the contact point of the open-circuit-ended line to the stator, thus effectively modifying one of the overall paths of the stator and, hence, the inter-transmission-zero separation. Design guidelines for the synthesis of the proposed rotation sensor with a specified dynamic range and sensitivity are provided. Furthermore, a proof-of-concept microstrip-substrate-based prototype with an angular rotation range of 180° is developed at 920 MHz and tested to validate this approach experimentally. [ABSTRACT FROM AUTHOR]

A tilted bi‐sense circularly polarized (CP) antenna and its application for UHF radio frequency identification (RFID) system is proposed. A planar concial monopole working as the electric dipole is designed at first. When a shorting pin is added, a loop radiator would be generated, and thus a pair of orthogonally oriented complementary dipoles is realized. In this way, both right‐handed circularly polarized (RHCP) and left‐handed circularly polarized waves (LHCP) are generated simultaneously in tilted directions within one hemisphere. Then, closed‐form formulas are derived to reveal the tunability mechanism of bi‐sense property and provide a design guideline for system application. It is demonstrated that flare angle of conical monopole has a linear relationship and sine function to CP beam direction and 3‐dB axial ratio (AR) beamwidth, respectively. Finally, antenna prototypes are fabricated and tested for validation. It is also demonstrated that at the tilted direction of θ = ± 45°, a 3‐dB AR bandwidth of 4.9%, and gain up to 5 dB are realized. Comparing with conventional microstrip patch antenna, an enhanced reading range over 5 m can be obtained in the tilted range from 40° to 75° and − 75° to −40° in UHF RFID sytem application. [ABSTRACT FROM AUTHOR]

In this brief, the design methodology of microstrip impedance transformers with extreme (i.e., extremely high and extremely low) impedance transforming ratios is proposed by deploying the cross-shaped structure (CSS) configuration. The proposed impedance transformer can significantly eliminate the line width limitation of traditional quarter-wave impedance transformer and hence an extremely wide range of impedance transformation can be easily realized. At the same time, the impedance transformer provides a good frequency selectivity, especially in the narrowband regime. To demonstrate the outstanding performance of proposed CSS impedance transformer, two examples, with the load-to-source impedances of 2000-to-50 $\Omega $ and 5-to- $50~\Omega $ , respectively, are presented and prototyped. The measurement results are in good agreement with the simulated counterparts and hence, the outstanding performance of extreme impedance transforming ratios is validated. [ABSTRACT FROM AUTHOR]

In this paper, the design methodology of a microstrip angular displacement sensor based on an impedance transformer with a quasi-Chebyshev frequency response is proposed. This sensor with impedance transforming function can realize the angular displacement detection by bandwidth sensing, and matching sensing simultaneously. The insertion loss in stopband achieves 24.9 dB to 32.6 dB with an average bandwidth selectivity of 2.25 MHz/degree of the sensor centered at 2.4 GHz with two poles of 1.71 GHz and 2.81 GHz. Meanwhile, the average matching level of return loss for displacement sensitivity are 0.18 dB/degree and 0.15 dB/degree, respectively. It is the first time to apply an impedance transformer into the angular displacement sensor design for both bandwidth and matching level sensing among reviewed literatures. In this design, the load-to-source impedance transformation is designed for 250-to- $50~\Omega $ , and by adding a rotated stub on the proposed microstrip transformer, the sensing function is developed with angular displacement. [ABSTRACT FROM AUTHOR]

A class of angular-displacement microwave sensor based on a microwave signal-interference transversal filtering section (TFS) with unequal-electrical-length paths is reported for the first time. It consists of a bi-path TFS composed of two in-parallel transmission-line segments with distinct lengths, which is modified by adding a rotational open-circuit-ended stub as the rotor to a curved section as the stator of one of its line segments. In this manner, the spectral positions of the transmission zeros, which are produced in its filtering transfer function through destructive signal-energy interactions, are modified with the rotation of this additional stub. This allows single/multi-band angular-displacement microwave-sensing capabilities in terms of transmission-zero inter-spacing variation for passbands/stopbands and stopband-peak-level modification to be attained by means of the mechanical rotation of the rotor. The theoretical operational principles of this type of bi-path-TFS-based angular-displacement microwave sensor and design curves for specific values of its electrical parameters are provided. Moreover, for experimental validation purposes, a proof-of-concept prototype of the devised TFS-based microwave-sensor approach operating at 961 MHz with 180° dynamic range is prototyped in microstrip technology and measured. A comparative analysis of the developed angular-displacement microwave sensor with the state-of-the-art is also presented. [ABSTRACT FROM AUTHOR]

Based on a novel microstrip terminated cross-shaped resonator (TCSR), the dual-band bandpass filters (DB-BPFs) with fixed and reconfigurable bandwidths are proposed in this brief. In addition to the basic TCSR’s three poles and four zeros, the extra four poles and three zeros can be introduced with the help of a pair of symmetrical parallel-coupled lines and open-ended stubs. Therefore, a planar DB-BPF with multiple transmission poles and zeros can be realized. To achieve the reconfigurable bandwidths, a capacitor is inserted into the basic TCSR’s lower stub. It is found that the lower bandedge of the first passband can be tuned while the other three bandedges are kept unchanged. Two prototypes, including fixed-bandwidth filter (Filter I) with 3-dB fractional bandwidths (FBWs) of 20.8% and 17.3%, and reconfigurable-bandwidth filter (Filter II) with 3-dB FBW variation from 22.5% to 34.7% for the first passband and 19.8% for the second passband, are designed, fabricated, and experimentally characterized. The experimental characterizations of these two filters verify the proposed design. [ABSTRACT FROM AUTHOR]

This paper presents a novel class of multilayered ultra-broadband bandpass filters based on high-impedance slotline resonators. The equivalent circuit and electrical properties of the proposed high-impedance slotline resonator realized on a low-permittivity substrate are first discussed. To largely remove the radiation losses of the devised high-impedance slotline resonator, two identical shunt-connected folded low-impedance slotline sections are utilized to replace one short-circuited high-impedance slotline section. Through the synthesis design of an ultra-broadband microstrip-to-microstrip vertical transition, the effective impedance of the conceived shunt-connected low-impedance slotline sections is confirmed and the impedance variations of this proposed high-impedance slotline resonator are quantitatively determined by the means of the extracted turns ratios of the employed transformers. To further demonstrate the effectiveness of the engineered slotline resonator in terms of radiation reduction and verify its equivalent circuit model, a new type of multilayered high-order bandpass filters with ultra-broadband Chebyshev equiripple filtering response is theoretically presented. Furthermore, for experimental validation purposes, a 2-GHz two-layered bandpass filter prototype is fabricated and measured. It exhibits a seven-pole ultra-broadband filtering response, high in-band amplitude/group-delay flatness, highly reduced radiation losses, and sharp-rejection upper-stopband characteristics. [ABSTRACT FROM AUTHOR]

A novel design approach to circularly polarized (CP) complementary antenna with a tilted beam is proposed. First, an operational principle of the proposed antenna is theoretically analyzed to explore the relationship between a pair of orthogonal complementary dipoles. It is demonstrated that two 8-shaped patterns are generated in the elevation plane while the CP characteristic can be realized where they are overlapped with each other. Then, a CP tilted beam can be obtained by reinforcing one direction while suppressing the remainders. Finally, prototype antennas, mainly consisting of a planar conical monopole, a loop antenna, and an L-shaped ground plane, are designed and fabricated for an experimental validation. Measurement results show that a 3 dB axial-ratio bandwidth of 6.19% at θ = 30°, ϕ = 90° is obtained by the design approach, as well as a low complexity and stable radiation pattern. [ABSTRACT FROM AUTHOR]

Abstract: In this article, a compact wideband microstrip‐to‐microstrip (MS‐to‐MS) vertical transition designed with a slotline stepped‐impedance resonator (SIR) is first presented. Compared with the existing wideband transitions, this proposed transition centered at f0 can tremendously extend its upper stopband via two introduced transmission zeros around 3f0 and 5f0. With the designed equivalent circuit, the working principle is theoretically discussed. To realize the size compactness of this proposed wideband transition, the slotline SIR is replaced by two back‐to‐back connected slotline Y‐junctions. Finally, a prototype wideband transition is simulated and fabricated. A wideband filtering response with its upper stopband up to 6.06 GHz under attenuation better than 15 dB is experimentally achieved as expected in the simulation. [ABSTRACT FROM AUTHOR]

In this paper, outage performance of hybrid automatic repeat request with incremental redundancy (HARQ-IR) is analyzed. Unlike prior analyses, time-correlated Nakagami- $m$ fading channel is considered. The outage analysis thus involves the probability distribution analysis of a product of multiple correlated shifted Gamma random variables and is more challenging than prior analyses. Based on the findings of the conditional independence of the received signal-to-noise ratios, the outage probability is exactly derived by using conditional Mellin transform. Specifically, the outage probability of HARQ-IR under time-correlated Nakagami- $m$ fading channels can be written as a weighted sum of outage probabilities of HARQ-IR over independent Nakagami fading channels, where the weightings are determined by a negative multinomial distribution. This result enables not only an efficient truncation approximation of the outage probability with uniform convergence but also asymptotic outage analysis to further extract clear insights, which have never been discovered for HARQ-IR even under fast fading channels. The asymptotic outage probability is then derived in a simple form, which clearly quantifies the impacts of transmit powers, channel time correlation, and information transmission rate. It is proved that the asymptotic outage probability is an inverse power function of the product of transmission powers in all HARQ rounds, an increasing function of the channel time correlation coefficients, and a monotonically increasing and convex function of information transmission rate. The simple expression of the asymptotic result enables optimal power allocation and optimal rate selection of HARQ-IR with low complexity. Finally, numerical results are provided to verify our analytical results and justify the application of the asymptotic result for optimal system design. [ABSTRACT FROM PUBLISHER]

This paper first presents two types of wideband microstrip-to-microstrip equal ripple vertical transitions designed with the uniform and folded slotline structures, respectively. By solving the characteristic function with differential calculation, the condition for realizing the constant equal ripple frequency response but different bandwidths (BWs) for the proposed transition is determined with resorting to the characteristic impedances of the coupled open-circuited microstrip line and slotline. Then, a vertical transition with the uniform slotline is synthetically analyzed and designed with Chebyshev polynomial function and another similar vertical transition with the same in-band ripple level but different BWs is also comparatively presented. By modifying the normalized impedances of the proposed transition to make the theoretical result close to the simulated one with the initial normalized impedances, the transformer turns ratios of the microstrip-to-slotline intersection is exactly calculated by the impedance ratios between two corresponding sets of normalized impedances. Due to the degraded high-frequency performance caused by the radiation loss of the uniform slotline, two vertical transitions with the folded slotline structure are further analyzed and the related turn ratios are extracted with the proposed approach. To verify the effectiveness on the reduction of radiation loss for the folded slotline structure, a six-pole wideband bandpass filter is presented with high-frequency performance greatly improved. In final, wideband vertical transitions with different slotline structures and a six-pole wideband bandpass filter are synthetically designed, simulated, fabricated, and measured. [ABSTRACT FROM AUTHOR]

In this paper, an ultra-wideband (UWB) filter with a notch band using T-shaped step impedance resonator loaded with cross-shaped open stubs has been presented. The notch band is formed by utilizing intrinsic zero. The characteristics of the new quad-mode resonator have been analyzed using odd-even mode analysis method. It can be shown that it is the intrinsic zero that generates the notch band. In addition, wide tunable notch band form 5–9.3 GHz can be achieved. A UWB filter with a notch band centered at 6.25 GHz using the proposed quad-mode resonator has been designed, fabricated, and tested. Experiment results show that the attenuation in notch frequency is >22 dB while the return loss of the simulation and measurement results are 22 dB/20 dB and 14.5 dB/11.2 dB in the lower and upper passband, respectively, which illustrate that the simulation and measurement results are in agreement. [ABSTRACT FROM PUBLISHER]

Wideband dipole antennas are proposed using the multi-mode resonance concept. By symmetrically introducing one-pair or two-pair of stubs at the nulls of current distribution of the second odd-order mode, two radiation modes are excited in a single, center-fed dipole resonator. Using these stubs, the second odd-order mode gradually moves down to its first counterpart, resulting to achieve a wideband radiation with two resonances. Prototype antennas are then fabricated to experimentally validate the design approach. Compared with a reference dipole with a bandwidth of 17%, the proposed dipole's bandwidth can be effectively increased to 49.7%. [ABSTRACT FROM PUBLISHER]

Operation principle and design approach of a novel planar end-fire circularly polarized (CP) complementary antenna is proposed. A vertically polarized printed magnetic dipole and a horizontally polarized printed dipole are combined on the same substrate, and a planar CP antenna with end-fire beam in parallel with its plane is thus designed. Prototype antennas centered at 5.80 GHz are then fabricated and measured to validate the operation principle and the design approach. The experimental prototype reported that the impedance bandwidth (20\textlog \vert\textS11\vert< - 10 {\text{dB}}) is about 1.90%, from 5.75 to 5.86 GHz and the 3-dB axial ratio (AR) bandwidth is about 14.48%, from 5.19 to 6.00 GHz. Therefore, the proposed design is applicable as a low-profile handheld reader antenna in radio-frequency identification (RFID) systems. [ABSTRACT FROM PUBLISHER]

In this paper, performance of hybrid automatic repeat request with incremental redundancy (HARQ-IR) over Rayleigh fading channels is investigated. Different from prior analysis, time correlation in the channels is considered. Under time-correlated fading channels, the mutual information in multiple HARQ transmissions is correlated, making the analysis challenging. By using polynomial fitting technique, probability distribution function of the accumulated mutual information is derived. Three meaningful performance metrics including outage probability, average number of transmissions, and long term average throughput (LTAT) are then derived in closed-forms. Moreover, diversity order of HARQ-IR is also investigated. It is proved that full diversity can be achieved by HARQ-IR, i.e., the diversity order is equal to the number of transmissions, even under time-correlated fading channels. These analytical results are verified by simulations and enable the evaluation of the impact of various system parameters on the performance. Particularly, the results unveil the negative impact of time correlation on the outage and throughput performance. The results also show that although more transmissions would improve the outage performance, they may not be beneficial to the LTAT when time correlation is high. Optimal rate design to maximize the LTAT is finally discussed and significant LTAT improvement is demonstrated. [ABSTRACT FROM PUBLISHER]

This paper presents the concept and demonstration of harmonic diversity for wireless communication, which makes use of multiple harmonic radio frequency (RF) channels with respect to the carrier frequency. Rather than frequency and space diversities widely used today to improve multipath fading, signal quality and spectral efficiency, the proposed scheme does not require multiple RF transceiver front-ends. The advantages of inherent RF device nonlinear characteristics are harnessed to produce and process harmonics within single transceiver. Even though distinct harmonic channels will exhibit different order of phase shifts, the analysis shows that such phase offsets can be compensated by adjusting the phase of local oscillator (LO) at receiver end. Extending the framework of the Shannon theorem, an M-channel harmonic communication system is shown to reduce the minimum required signal-to-noise ratio (SNR) at the input of receiver by M-times. In addition, this work indicates that the power consumption of transmitter can be significantly reduced up to 66% than the conventional ones. Through the analysis of channel capacity, the harmonic system is proved to outperform the single channel counterpart especially when SNR is low. To validate the correctness of the proposed concept, a series of experiments are carried out to emulate the developed theoretical models. For instance, a three-channel harmonic communication system is prototyped, involving certain RF harmonic components designed for demonstration. The retrieved signal strengths are examined with different phase setting of receiving LO, and various modulation techniques are applied for estimating the system performances. All measured results are in agreement with their simulated counterparts, thereby demonstrating the correctness and usefulness of the proposed theories and techniques for nonlinear communication systems of harmonic diversity. [ABSTRACT FROM PUBLISHER]

ABSTRACT A wideband vertical microstrip-to-micrstrip transition is presented by utilizing the composite microstrip/slotline resonators. With the coupling between two 50-Ω microstrip lines on top and bottom layers, respectively, and a uniform slotline resonator on the common ground plane, a proposed three-pole wideband filtering performance for the signal transmission through different layers can be achieved. To verify the expected results, a vertical transition prototype is simulated, fabricated and measured. Good agreement between the simulation and measurement results is gained. An operating band from 3.51 to 8.25 GHz with maximum insertion loss of 1.5 dB and group delay < 0.4 ns is achieved in measurement. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2213-2216, 2015 [ABSTRACT FROM AUTHOR]

This paper presents a novel balanced dual-band bandpass filter with in-band common-mode suppression via multiple transmission zeros from the doubly short-ended coupled line. Through the analysis of coupled line structures, the transmission zeros in the differential- and common-mode equivalent circuits are extensively studied. In differential-mode, the transmission zeros, produced by both short-ended coupled line and open stub, are independently controlled, and the desired two resonant frequencies of the dual-band bandpass filter are achieved by studying the characteristics of the doubly short-ended half-wavelength resonator. For the common-mode suppression, the intrinsic transmission zeros of short-ended coupled line in differential-mode structure appear in the same frequency locations due to the proposed common-mode strcuture. With proper adjustment of the impedances and electrical lengths of the terminated stepped-impedance resonators (SIRs) on the symmetric plane, additional transmission zeros are introduced and relocated at the differential-mode resonant frequencies, thus producing good in-band common-mode signal attenuation as highly expected. As the attractive advantage of proposed balanced structure, the common-mode performance is independent of differential-mode one. To verify the proposed design method, a prototype balanced dual-band filter is theoretically analyzed, simulated, and experimentally measured, good agreements between simulated and measured results are obtained. The measured balanced dual-band bandpass filter is centered at 900 MHz and 2.49 GHz, and in-band common-mode rejection for first and second passbands are presented with higher than 30 and 40 dB, respectively. [ABSTRACT FROM PUBLISHER]

In this paper, two kinds of wideband differential filters with intrinsic common-mode (CM) rejection are proposed. Both these filters are realized based on the multimode slotline resonators under the dual- and triple-mode resonance, respectively. For Filter 1, the microstrip lines with a pair of differential ports at the two sides are directly tapped on a slotline resonator. For Filter 2, the slotline resonator is connected with two pairs of microstrip open-ended stubs both at top and bottom layers at the beginning. In these two filters, the CM signals are effectively rejected during electromagnetic field conversion. Only the differential-mode performances are left to be focused on. A systematic design method is then presented with simplified circuit models in differential mode, and frequency responses of these models are synthesized and further mapped into physical dimensions. Transformers are used in the mapping procedure and their turn ratios are calculated to find the exact final dimensions or are properly used to realize desired performance with some unattainable impedance values in synthesized simplified models. Finally, two filters are designed, fabricated, and measured to support the design method. [ABSTRACT FROM AUTHOR]

A wideband bandpass filter (BPF) with reconfigurable bandwidth (BW) is proposed based on a parallel-coupled line structure and a cross-shaped resonator with open stubs. The p-i-n diodes are used as the tuning elements, which can implement three reconfigurable BW states. The prototype of the designed filter reports an absolute BW tuning range of 1.22 GHz, while the fractional BW is varied from 34.8% to 56.5% when centered at 5.7 GHz. The simulation and measured results are in good agreement. Comparing with previous works, the proposed reconfigurable BPF features wider BW tuning range with maximum number of tuning states. [ABSTRACT FROM PUBLISHER]

In this letter, a wideband microstrip-to-microstrip vertical transition using open-circuited slotline stepped-impedance resonator (SIR) is proposed. By controlling the impedance ratio of the slotline SIR, two transmission zeros (TZs) can be properly created and relocated to improve the passband selectivity. To determine the characteristic of this transition, its transmission-line circuit model is presented for analysis and design. Finally, a prototype transition is designed and fabricated for experimental verification. Not only high filtering selectivity via emergence of these TZs but also wideband filtering response with out-of-band suppression of about 22 dB in a frequency range up to 2.51f0 is experimentally achieved. [ABSTRACT FROM PUBLISHER]

In this communication, a novel highly integrated antenna-triplexer on a two-layer printed circuit board is proposed for multiband communication systems. This integrated three-port component operated at triple frequency bands (0.85, 1.65 and 2.45 GHz) simultaneously utilizes a single slot antenna and its rectangular loop as the radiating elements. Good three-port isolations are achieved by the multi-mode excitations including even, odd and bi-directional modes. These modes are intrinsically orthogonal and therefore the isolations are guaranteed. Compared with the conventional counterparts that use additional bandpass filters to assure the port isolations, the proposed antenna-triplexer preserves the simplicity and compactness of the antenna itself, and it is suitable for the practical portable applications. To demonstrate the significance of this new antenna-triplexer, a prototype measured with compact size is implemented and the experimental results show the good agreements with the simulations. The antenna gains of 0.85, 4.00 and 4.23 dBi are obtained and an average isolation in three ports is as good as 22.7 dB at operating frequencies. [ABSTRACT FROM PUBLISHER]