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A miniaturized implantable antenna with bandwidth enhancement is proposed for cardiac pacemaker application in MICS band (402–405 MHz) and ISM band (433–434.8 MHz, 902–928 MHz) in this paper. By introducing split resonant rings, the proposed antenna has achieved ultra-wideband characteristics, which can cover from 272 MHz to 1504 MHz, and the relative bandwidth is 138.7%. Additionally, a new wireless power transfer (WPT) system is designed by integrating with a miniaturized metasurface to enhance the WPT efficiency and extend the lifetime of the implantable device. The transmission coefficient S21 of the WPT system loaded with metasurface is 11 dB higher than the initial system at the resonance point. Furthermore, biosafety is taken into consideration for practical applications. The experiments in the equivalent body environment are performed to demonstrate the reliability of the proposed antenna. The measured and simulated results are in good agreement, which shows that the proposed antenna is appropriate to be applied in wireless power transfer systems.

A high-gain superstrate antenna array is designed at 60 GHz. The proposed antenna array is extremely low in cost and possesses high performance metrics. The proposed structure can be integrated easily into many modern millimeter-wave/5G transceivers. The array boresight gain is 19.4 dBi, the relative bandwidth is 10.7%, and the maximum gain variation is 1.7 dB within the operating bandwidth.

Design and measurement of a broadband compact circular TE11 mode input coupler for gyrotron traveling wave tubes (gyro-TWTs) are presented in this article. Different from the T-junction, Y-type, and multiple-hole input couplers, the proposed coupler has a merit of compact dimensions formed by the H-plane of a rectangular cavity. The simulation results show that the port reflection $S_{11}$ is less than −10 dB within 7.9–9.93 GHz. Also, the split transmissions $S_{21}$ and $S_{31}$ are over −3.4 dB in this band. It indicates that the relative bandwidth is 22.8%, and the transmission efficiency is higher than 90%. To further broaden the bandwidth, we propose an improved input coupler with ridges achieving an excellent bandwidth of 28.6%. The designed input coupler has been measured with open boundaries and matched output ports. The simulation and measurement results are in good agreement. The compact TE11 mode input coupler had been applied in our X-band gyro-TWT design.

We have proposed a vector-sum phase shifter (VSPS) with a low phase shift error using a tunable active $g_{m}{\text {-}}{C}$ polyphase filter (PPF). The proposed VSPS realizes high insertion gain and a low phase shift error because the tunable active ${g}_{m}{\text {-}}{C}$ PPF exhibits insertion gain and low I/Q imbalance by easily controlling the transconductance of transistors. This study provides a general formula and design method based on the design equations of the tunable active ${g}_{m}{\text {-}}{C}$ PPF for VSPS. The analysis shows the limitation of the tunable frequency range of I/Q balance and the condition of the maximum insertion gain. The results also clarify that the relative bandwidth of the tunable active ${g}_{m}{\text {-}}{C}$ PPF is equivalent to that of the single-stage or multistage RC -PPF. The ${S}$ -band VSPS with the two-stage active ${g}_{m}{\text {-}}{C}$ PPF fabricated by the design method demonstrates improvement in phase shift errors lower than 0.52° rms in the 500-MHz bandwidth and high insertion gain of 13.4 dB with a frequency range of 2.2–3.2 GHz.

We propose simple designs of compact patch antennas with bandwidth enhancement. Firstly, an inverted “L” strip is loaded onto the corner of one radiating patch edge to create an additional resonant mode which can be combined with that one of the conventional patch to enhance the operating bandwidth. Secondly, the “L” strip is replaced by inverted “T” strip to improve further the bandwidth by creating two adjustable resonant modes. The two proposed patch antennas have the particularity of enhancing the bandwidth significantly without increasing their profile and their overall sizes. Two antenna prototypes are fabricated and tested. Measurements reveal that the patch antenna loaded with “L” strip has stable radiation characteristics with 5.2 times enhancement in the relative bandwidth compared with a conventional patch antenna. The antenna loaded with inverted “T” strip has wider bandwidth (6.25 times wider than the conventional patch) and covers the operating band 5.07–5.89 GHz (15%) with measured peak gain and peak efficiency of 6.25 dBi and 78%, respectively. The proposed antennas are easy to fabricate, have a low-profile, and exhibit good performances which make them good candidates to use in real wireless applications.

The paper considers a method for increasing the relative throughput of requesting airspace surveillance radar systems, in which it is proposed to use broadband signals as request and response signals. Thanks to the use of broadband signals, it is possible to reduce significantly the detection range of such response signals with the required quality indicators by means of radio reconnaissance, which practically excludes the possibility for the interested party to use the response signals of an aircraft responder both for long-range detection of air objects and for measuring their coordinates. And, as a result, it makes it possible to exclude unauthorized use of an aircraft responder of requesting radar systems for airspace monitoring by an interested party to suppress the response channel, and, consequently, increase the relative throughput of the considered information systems., В работе рассматривается метод повышения относительной пропускной способности запросных радиолокационных систем наблюдения воздушного пространства, в котором в качестве сигналов запроса и ответа предложено использовать широкополосные сигналы. Благодаря использованию широкополосных сигналов удается значительно снизить дальность обнаружения таких ответных сигналов с требуемыми показателями качества средствами радиоразведки, что практически исключает возможность заинтересованной стороне использовать сигналы ответа самолетного ответчика как для дальнего обнаружения воздушных объектов, так и для измерения их координат. И, как следствие, позволяет исключить несанкционированное использование самолетного ответчика запросных радиолокационных систем наблюдения воздушного пространства заинтересованной стороной для подавления канала ответа, а, следовательно, позволяет повысить относительную пропускную способность рассматриваемых информационных систем., У роботі розглядається метод підвищення відносної пропускної здатності запитальних радіолокаційних систем спостереження повітряного простору, в якому як сигнали запиту та відповіді запропоновано використовувати широкосмугові сигнали. Завдяки використанню широкосмугових сигналів вдається значно знизити дальність виявлення таких сигналів відповіді з необхідними показниками якості засобами радіорозвідки, що практично виключає можливість зацікавленій стороні використовувати сигнали відповіді літакового відповідача як для далекого виявлення повітряних об'єктів, так і для вимірювання їх координат. І, як наслідок, дозволяє виключити несанкціоноване використання літакового відповідача запитальних радіолокаційних систем спостереження повітряного простору зацікавленою стороною для подавлення каналу відповіді, а, отже, дозволяє підвищити відносну пропускну здатність розглядаємих інформаційних систем.

Algorithm for the realization of the broad range of values of wide relative bandwidth (RBW) bandpass filter is introduced. Algorithm is based on periodic ideal cells each with short-ended stub. Theory is developed for a symmetrical cell with proportional transmission lines, nonuniform or uniform, in term of characteristic impedance. The theory is applied for the uniform transmission lines. Simple equation of the ratio between characteristic impendence of the short-ended stub and the characteristic impendences of the main lines is given for the broad range of RBW. Realizable filters are for the very wide RBW up to over 1.5 (150%). Technology is chosen in microstrip with vias for the short ends. It is without coupling, without defected ground structure (DGS) and only with a single layer. The procedure is tested on the fabricated filters for very wide RBW of 1.5 (150%). Agreement between measurements and simulations is excellent.

Seismic metamaterials (SMs) are expected to assist or replace traditional isolation systems owing to their strong attenuation of seismic waves. In this paper, a one-dimensional inverted T-shaped SM (1D ITSM) with an ultra-wide first bandgap (FBG) is proposed. The complex band structures are calculated to analyze the wave characteristics of the surface waves in the SMs. We find that the FBG of the 1D ITSM is composed of two parts; part 1 with surface evanescent waves and part 2 with no surface modes. Similar results are found in the complex band structure of the FBG of the SM consisting of periodically arranged pillars and substrate. The propagation of seismic surface waves in the 1D ITSM is different in these two frequency ranges of the FBG. In part 1, the seismic surface waves are significantly attenuated in the 1D ITSM, while in part 2, the surface waves are converted into bulk waves. Finally, the ultra-wide FBG is verified by using a kind of the two-dimensional ITSM in large-scale field experiments., 30 pages,15 figures

In this paper, a broadband and high-efficiency RCS reduction enhancement by employing a polarization-conversion coding metasurface is demonstrated in the terahertz region. A symmetric linearly polarized conversion metasurface with a relative bandwidth of 74% and a polarization conversion ratio (PCR) over 90% from 0.24 THz to 0.52 THz is designed as the 1-bit coding block. By applying the Golay-Rudin-Shapiro (GRS) polynomials on the coding series, a highly effective RCS reduction paradigm averaged below -20 dB has been achieved with a cross-polarization enhancement. Compared to the co-polarized counterpart, a -10 dB enhancement is attained by the cross-polarized coding array. It paves a promising path to terahertz RCS reduction and polarized wave regulation.

In this article, analytical, empirical, and numerical techniques are integrated for analyzing and synthesizing circuit analog (CA) absorbers based on a single-layer frequency-selective surface (FSS). The proposed design approach dramatically reduces the number of full-wave simulations required for global optimization, so that the potential of fundamental FSS geometries can be exhaustively exploited. With the semi-analytical algorithm, the near optimal bandwidth-thickness can be quickly and reliably calculated for a given single-FSS-layer topology. To demonstrate the robustness of our semi-analytical approach, a square-patch and square-ring FSS absorbers at 10 dB level of absorption are revisited and optimized. The designs are constrained by available materials and standard tolerances for experimental validation. A manufactured prototype achieves a relative bandwidth of 144.15% and a normalized thickness of 0.0972λL, which is superior to existing designs with more complicated FSS patterns in the literature.

In this letter, a wide-angle narrowband leaky-wave antenna (LWA) based on substrate integrated waveguide-spoof surface plasmon polariton (SIW-SSPP) structure is proposed. Periodic slots are etched on both the top and bottom surfaces of SIW to introduce an SSPP mode. The periodic slots on the top surface are sinusoidally modulated to realize bidirectional LWA radiation. The problem of open stopband is solved by the asymmetrical design of the top and bottom slots. Thus, a wide bidirectional scanning range from −60° to +63° is achieved. Besides, the relative bandwidth of the fabricated antenna is reduced to only 9% by introducing the slow-wave effect of SSPP. It means the proposed antenna has a large scanning rate, or equivalently beam scanning range/bandwidth ratio.

A scheme to extend the beam number of Butler matrices (BMs) by utilizing reconfigurable couplers is presented and illustrated with experimental verification. The beam number of a traditional $2^{N} \times 2^{N}$ BM can be increased to $3\cdot 2^{N}$ by substituting reconfigurable couplers for all hybrids while maintaining the structure and other components as the original. Moreover, only N sets of different parameters are required for these couplers. The principle, properties, and the generalized expressions for the N sets of parameters are discussed and exhibited. The properties of the extended beams are illustrated in terms of beam directions and crossover levels. As an example, a switchable 12-beam forming network extended from a $4\, \times \, 4$ BM for 2.4 GHz applications is fabricated and tested. Over a 30% relative bandwidth is achieved with phase errors less than ±12°, amplitude unbalances lower than ±1.7 dB, isolations better than −15.5 dB, and a return loss better than 11.5 dB.

A linear-to-linear 2.5-dimensional polarization conversion metasurface (2.5-D PCM) with a high polarization conversion ratio (PCR) in ultrawideband is proposed. The unit cell of the 2.5-D PCM is composed of a superstrate etched with metal strips and a substrate attached with a metal ground. The 2.5-D PCM can efficiently convert the polarization of x -polarized or y -polarized wave to its cross direction after reflection. The PCRs are higher than 96% within a relative bandwidth of 99.5% for the x - and y -polarized vertically incident waves. In addition, the 2.5-D PCM can be applied to reduce the in-band and out-band radar cross section (RCS) of different antennas. A circularly polarized antenna is chosen as an example. Compared to the reference antenna, the monostatic and bistatic RCSs of the proposed antenna are decreased in an ultrawideband without the performance degradation of the antenna. The prototypes of the 2.5-D PCM and the antennas are fabricated, and the measurements are in reasonable accordance with the simulations.

A uniform circular array with dual orbital angular momentum (OAM) modes is proposed for in-band full-duplex applications. The proposed scheme includes two concentric ring subarrays for transmitting and receiving, respectively, where all elements are operated under the same linear polarization. To suppress the self-interference resulting from the mutual coupling, an OAM mode-selection method related to the proposed configuration is discussed. Results indicate that good isolation performance between the transmitter and receiver can be achieved by using the proposed scheme. To validate the performance, a demonstrator with OAM modes of −1 and −2 at Ku-band is developed, fabricated, and measured. Measurements show a relative bandwidth of 21.3% from 13.5 to 16.7 GHz, referring to a 40 dB suppression level, is achieved and the desired radiations are found.

The present work is devoted to the miniaturization of a conventional three branch line coupler device in UHF band. The procedure for designing miniature structures based on replacing the microstrip transmission line segment with equivalent structures with the same phase shift is described. These structures are placed in free space inside the coupler. The proposed coupler operates at 1 GHz (UHF band), with good specifications. The area of the manufactured prototype of the three-branch line coupler with open-circuit conditions stubs is 909 mm2, which is 76% less than the size of the conventional device and relative bandwidth is 23.7%. The area of the manufactured prototype of the three-branch line coupler with high-resistance lines with a high-resistance segment in the form of U symbol is 1169.7 mm2, which is 69.1% less than the size of the conventional device and relative bandwidth is 34.1%.

The paper analyzes the principles of construction and structure of "friend or foe" identification systems. It is revealed, that the party, interested in the existing system, has the ability of unauthorized use of this information resource for long-range determination of air objects coordinates, on the one hand, and distortion of information of this information resource, on the other hand, which leads to unpredictable consequences. It is shown, that the most vulnerable place in the "friend or foe" identification systems is the aircraft transponder, which significantly affects noise stability and noise immunity of the identification systems of air objects. The paper proposes a method of hereditary transition to noise-immune "friend or foe" identification systems based on synchronous networks of identification systems, which allows expanding significantly the methods of servicing requests and methods of constructing systems. This method of constructing identification systems eliminates the existing problem of dispersed identification systems, as well as the problem of temporal matching of signals coming from primary and secondary radar systems. The proposed method of hereditary transition to noise-immune "friend or foe" identification systems makes it possible to exclude the possibility of unauthorized access to identification information resources by an interested party, significantly increases the noise immunity of the identification system as a whole., Проанализированы принципы построения и структура систем идентификации «свой-чужой» и выявлено, что в существующей системе заинтересованная сторона имеет возможность несанкционированно использовать данный информационный ресурс для дальнего определения координат воздушных объектов, с одной стороны, и искажения информации этого информационного ресурса, с другой стороны, что приводит к непредсказуемым последствиям. Показано, что наиболее уязвимым местом в системах идентификации «свой-чужой» является самолетный ответчик, который существенно влияет на помехоустойчивость и помехозащищенность идентификационных систем воздушных объектов. В работе предложен метод наследственного перехода к помехоустойчивых систем идентификации «свой-чужой» на основе синхронных сетей систем идентификации, который позволяет существенно расширить методы обслуживания заявок и методы построения систем. Такая методика построения идентификационных систем исключает имеющуюся проблему рассредоточенных идентификационных систем, а также проблему временного согласования сигналов, поступающих из систем первичной и вторичной радиолокации. Предложенный метод наследственного перехода к помехоустойчивых систем идентификации «свой-чужой» позволяет исключить возможность несанкционированного доступа заинтересованной стороной в идентификационные информационные ресурсы, в значительной мере повышает помехозащищенность идентификационной системы в целом., Проаналізовано принципи побудови і структуру систем ідентифікації «свій-чужий» та виявлено, що у існуючій системі зацікавлена сторона має можливість несанкціоновано використати даний інформаційний ресурс для дальнього визначення координат повітряних об’єктів, з одного боку, та перекручування інформації цього інформаційного ресурсу, з другого боку, що призводить до непередбачуваних наслідків. Показано, що найбільш вразливим місцем в системах ідентифікації «свій-чужий» є літаковий відповідач, який істотно впливає на завадостійкість та завадозахищеність ідентифікаційних систем повітряних об'єктів. Запропоновано метод спадкоємного переходу до завадостійких систем ідентифікації «свій-чужий» на основі синхронних мереж систем ідентифікації, який дозволяє істотно розширити методи обслуговування заявок та методи побудови систем. Така методика побудови ідентифікаційних систем виключає наявну проблему розосереджених ідентифікаційних систем, а також проблему часового узгодження сигналів, що поступають з систем первинної та вторинної радіолокації. Запропонований метод спадкоємного переходу до завадостійких систем ідентифікації «свій-чужий» дозволяє виключити можливість несанкціонованого доступу зацікавленої сторони до ідентифікаційних інформаційних ресурсів, що значною мірою підвищує завадозахищеність ідентифікаційної системи в цілому.

The quality factor of the inductor in the matching network, which is one of the keys to realize a broadband PA, needs to be decreased for expanding the bandwidth. The paper presents multilayer inductors, which have low quality factor and can tolerate large current, for expanding the bandwidth. The multilayer inductors (MIs) are used in a CMOS PA, which reaches a good performance in the measured 133% relative bandwidth.

In this paper, a Halo antenna with four parasitic elements is proposed as a horizontally polarized wideband antenna. The characteristics of the proposed antenna are analyzed through simulation. The results demonstrate that the antenna offers a small diameter and wideband performance. The relative bandwidth of the antenna is 12.1%, respectively. In addition, its radiation patterns are omnidirectional.

International audience; Acoustic metasurfaces can reshape a reflected wavefront rather arbitrarily, despite being much thinner than the wavelength, thus allowing on-demand wavefront modulation in a variety of applications. Recent passive metasurfaces, however, have suffered from bandwidth limitations, thus restricting their range of operation. In this work, we propose the systematic design of ultra-broadband passive metasurfaces by combining the broadband local reflection rule with an optimization method. The validation of the technique is demonstrated by fabrication and measurement of an ultra-broadband carpet cloak. Numerical and experimental results show that the relative bandwidth of the optimized carpet cloak, thinner than one fifth of the maximum wavelength, can exceed 93.33%, a value that is much larger than that of previous passive metasurfaces. Furthermore, multi-frequency pulse incidence tests reveal the excellent time-domain broadband characteristics of the metasurface over a wide range of angles of incidence. The proposed strategy opens a new route for the design of advanced passive metasurfaces for ultra-broadband wave manipulation and thus promotes practical applications of broadband acoustical devices.

The paper synthesizes the optimal structure of data processing of the aircraft transponder of the “friend or foe” identification system based on the Neumann-Pearson criterion. It is also shown, that when synthesizing and analyzing the optimal structure of signal data processing in aircraft transponders of "friend or foe" identification systems, it is necessary to take into account the multichannel reception of request signals and limitations of relative throughput of the aircraft transponder, which is caused by the existing principle of constructing the system as single-channel queuing system with failures. The proposed models make it possible to implement the structures of data processing of request signals for situations of inter-channel merging of previous channel decisions on the detection of request signals or pulse components of the request signals. In the proposed structure, the optimization of data processing is carried out not only in time but also in the spatial parameters of the request signals, and also takes into account the relative bandwidth of the aircraft responder. It is shown that the inter channel merging of the results of detecting the component pulses of the query signals is more preferable compared to the existing algorithm of merging the results of detecting the query signals, as it improves the quality of query signal detection and reduces the dependence of query signal detection of relative response., Синтезирована оптимальная структура обработки данных самолетного ответчика системы идентификации «свой-чужой», на основе критерия Неймана-Пирсона. Также показано, что при синтезе и анализе оптимальной структуры обработки сигнальных данных в самолетных ответчиках систем идентификации «свой-чужой» необходимо учитывать многоканальность приема сигналов запроса и ограничения относительной пропускной способности самолетного ответчика, которая обусловлена имеющимся принципом построения системы как одноканальной системы массового обслуживания с отказами. Предложенные модели позволяют реализовать структуры обработки данных сигналов запроса для ситуаций межканального слияния предыдущих канальных решений об обнаружении сигналов запроса или импульсных составляющих сигналов запроса. В предложенной структуре оптимизация обработки данных осуществляется не только по времени, но и по пространственным параметрам сигналов запроса, а также учитывается относительная пропускная способность самолетного ответчика. Показано, что межканальные слияния результатов выявления составляющих импульсов запросных сигналов более предпочтительно по сравнению с существующим алгоритмом слияния результатов обнаружения запросных сигналов, так как позволяет повысить качество обнаружения запросных сигналов и снизить зависимость вероятности обнаружения запросных сигналов от относительной пропускной способности самолетного ответчика., Синтезована оптимальна структура обробки даних літакового відповідача системи ідентифікації «свій-чужий», на основі критерію Неймана – Пірсона. Показано, що при синтезі та аналізі оптимальної структури обробки сигнальних даних у літакових відповідачах систем ідентифікації «свій-чужий» необхідно враховувати багатоканальність прийому сигналів запиту та обмеження відносної пропускної здатності літакового відповідача, яка зумовлена наявним принципом побудови системи як одноканальної системи масового обслуговування з відмовами. Запропоновані моделі дозволяють реалізувати структури обробки даних сигналів запиту для ситуацій міжканального злиття попередніх канальних рішень про виявлення сигналів запиту або імпульсних складових сигналів запиту. В запропонованій структурі оптимізація обробки даних здійснюється не тільки за часовими, але й за просторовими параметрами сигналів запиту, а також враховується відносна пропускна здатність літакового відповідача. Показано, що міжканальне злиття результатів виявлення складових імпульсів сигналів запиту більш переважне в порівнянні з існуючим алгоритмом злиття результатів виявлення сигналів запиту, так як дозволяє підвищити якість виявлення сигналів запиту та знизити залежність ймовірності виявлення сигналів запиту від відносної пропускної здатності літакового відповідача.

In this paper, a modified structure of the susceptance component loaded coupled line complex impedance transformer is presented for the purpose of easy connection. It is composed of two transmission lines, a parallel coupled line and a susceptance element. The design equations are derived by using the even-odd mode analysis. Using the equations, the circuit parameters for different source and load impedances are given. To verify the proposed structure, a prototype is designed and fabricated at 1 GHz. The measured relative bandwidth is 50 % (0.84 ~ 1.34 GHz) under the criterion of |S11| < - 15 dB, which verifies the effectiveness of the proposed structure.

Substrate integrated waveguide (SIW) to rectangular waveguide (RWG) transition plays a significant role in mmW applications. Unlike conventional broadband transitions, they often use multi layers or insertion structures. In this paper, a single-layer right-angle transition between SIW and RWG is presented. The impedance bandwidth of the single transition $(|\mathbf{S} 11|\lt -15 \mathbf{d B})$ is from 50.2 to 65.2 GHz, or a relative bandwidth of 26%. A back-to-back transition is also designed for verification. Its impedance bandwidth $(|\mathbf{S} 11|\lt-15 \mathbf{d B})$ is from 52.5 to 64.5 GHz (20.5%).

© 2020 IEEE. An extension of the basic concept of a self-oscillating non-Foster cross-dipole to a self-oscillating Huygens radiator has been developed theoretically and studied numerically. A proof-of-concept prototype has been built. The realized antenna consists of two orthogonal dipole-loop pairs, a negative impedance converter, and a tuning LC circuit. In this paper we report the basic concepts and the initial results obtained with a scaled RF demonstrator operating in the 60 MHz regime. The preliminary results have demonstrated self-oscillations with nearly-perfect admittance matching over a tuning bandwidth of 1:1.35. The familiar cardioid-like radiation pattern was achieved as designed across the 10% relative bandwidth. These results confirm the efficacy of the basic idea of self-oscillating non-Foster Huygens radiators.

In this paper, a problem of the evaluation of the far-field (Fraunhofer) zone (FZ) threshold of the frequency diversity arrays (FDA) for multipurpose using is presented. It is shown, that because of space-time dependency of the array field, such parameters of partial signals as a relative bandwidth, a spectrum overlap factor and an amplitude distribution should be taken into account for FZ threshold evaluation. Criteria for FZ threshold based on the relative errors of the evaluation of the time-dependent directivity factor is proposed. As an example of the linear equidistant FDA, estimates of the FZ threshold by proposed criteria are obtained. The results can be useful to the design of processing algorithms of cognitive control for FDA radars, as well as in experimental and simulation studies.

A transmitting array antenna for both long- and medium- range automotive radar application is proposed in this paper. The array antenna consists of six linear series-fed patch subarrays and a network based on substrate integrated waveguide (SIW). With adoption of the broadband self-compensating phase shifter, the antenna has a good performance in wide band. Simulation results show that impedance bandwidth is from 23.9GHz to 25.1GHz, the relative bandwidth with flat-shoulder pattern is 2%.

In this paper, a three-dimensional (3-D) frequency selective surface (FSS) based on spoof surface plasmon polaritons (SSPPs) is presented, which can realize ultra-wideband bandstop performance. The proposed FSS is composed of two single 3-D bandstop FSSs, and dielectric substrates they use have different relative dielectric constants, which have different stopband response. Then, two FSSs are stacked to form a new FSS structure, which has ultra-wideband bandstop performance. The simulation results indicate that the relative bandwidth of −10 dB stopband of this FSS is about 110.3% (4.8-16.6 GHz).

This paper presents the design of a wideband dual-polarized microstrip antenna array working at C-band. The antenna adopts a multi-layer structure using additional parasitic patch, in order to achieve better port isolation and wide-band characteristics. The 1*4 array antenna is simulated and optimized, which is fed by the coplanar microstrip lines. The results show that the VSWRs of the antenna ports are less than 2 in the frequency range of 4.9 GHz to 6.1 GHz, with a relative bandwidth of about 21.8%. The designed antenna also has a gain of over 13.4 dB at the frequency of 5.5 GHz.

A microstrip antenna with a simple structure for S-band is presented in this letter. The proposed antenna consists of a circular patch, a partial annular ring and an I-shaped ground plane. By loading a shorting pin between the circular patch and the ground plane, a significant reduced antenna size is achieved. The proposed antenna has an operating impedance bandwidth ranges from 2.45 to 3.65GHz, which corresponds to relative bandwidth of 40% and almost covers entire S-band range. The simulation and experimental results of the proposed antenna are presented and discussed. This antenna is suitable for indoor communications, satellite communications, radars, etc.

This paper proposes a low-profile wideband antenna composed of trapezoidal plates element arranged in Y-shape, a circular element and three short elements. The characteristics of the proposed antenna are analyzed through simulation. The results demonstrate that the proposed antenna offers a low-profile and wideband performance. The height and the relative bandwidth of the proposed antenna are 0.035λ and 48.0%, respectively. In addition, its radiation patterns are omnidirectional.

This work introduces a flat coupling backward-wave directional coupler based on a printed ridge gap waveguide (PRGW) technology for mm-wave applications. The construction of the proposed coupler is based on a coupled PRGW lines connected by a central rectangular junction. The coupler is demonstrated to have 8% relative bandwidth at 30 GHz. The prototype of the proposed coupler is fabricated and measured, where the measured and simulated results show good agreement.

In this paper, a design method of reconfigurable broadband bandpass filter, with the advantage of adjustable bandwidth, is proposed by fabricating a hybrid sharing waveguide which is consist of half mode substrate integrated waveguide (HMSIW) and spoof surface plasmon polarization (SSPP). By adding a U-shaped resonant unit and a container structure to the bandpass filter, then through the movement of the slide on U-shaped groove and the alteration of the medium parameters in the container, the lower cut-off frequency of HMSIW and upper cut-off frequency of SSPP can be independently controlled by the fine tuning of the structures easily without changing the filter parameters. A prototype sample is fabricated to demonstrate and confirm the validity of the proposed method. The measured largest passband ranges from 11.5 to 14.5 GHz with the relative bandwidth of 23% which can be adjusted within a certain scope. The design of reconfigurable filter is realizing by the combination of HMSIW–SSPP structure and the concept of tunable filter. The proposed method can be used to develop different broadband bandpass filters.