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Summary: Developing wireless communication systems depends on reconfigurable microwave filters (MF) and dielectric resonator antenna (DRA) because the functionality of the various filters and antennas available for a wireless communication system is limited, and reconfigurable DRA and MF are utilized to overcome these limitations. The throughput of a multiantenna system can be achieved with reconfigurable DRA and filter. Various switching strategies and classifications of reconfigurable DRA and MF are presented. The electrical reconfiguration technique is most suitable for developing a reconfigurable DRA and filter among all the switching techniques. In this approach, reconfigurability may be accomplished by utilizing a PIN diode, a varactor diode, and a radio‐frequency microelectromechanical switch (RF‐MEMS). These switches are more reliable, highly efficient, and easily integrated with the microwave circuit. Reconfigurable DRA with machine learning is demonstrated. The application of reconfigurable DRA and filters in cognitive radio (CR) is also demonstrated. Also, the review article focused on the performance parameters, design, and challenges of reconfigurable antenna and MF. [ABSTRACT FROM AUTHOR]

Summary In today's intricate wireless communication environment, ensuring system quality demands the use of a reliable and versatile antenna system. This research article introduces a polarization reconfigurable antenna integrated with a 4 × 4 Artificial Magnetic Conductor (AMC) surface. The AMC unit cell exhibits a triple‐band reflection phase response at 1.8GHz, 4.5GHz, and 5.5GHz, demonstrating double negative metamaterial behavior. The antenna features two distinct C‐shaped metal strips connected to two PIN diodes, enabling dynamic current distribution adjustment. Consequently, the proposed antenna offers three reconfigurable states, facilitating seamless switching between dual circular polarization (left and right‐hand circular polarization) and linear polarization. With a frequency coverage ranging from 1.29 to 2.52GHz and 3.59 to 6.15GHz, the antenna boasts a maximum axial ratio (AR) bandwidth of 31.96%. Additionally, it achieves a maximum peak gain of 5.5 dB and maintains front‐to‐back ratio (FBR) values exceeding 25 dB, while recording a minimum specific absorption rate (SAR) value of 0.1059 W/kg. The integration of the AMC surface ensures enhanced performance of the antenna. Experimental results from constructed prototypes closely align with simulation outcomes, validating the effectiveness of the proposed antenna. Consequently, this antenna holds significant promise for next‐generation wireless applications. [ABSTRACT FROM AUTHOR]

In this paper, a transmissive reconfigurable polarization converter (RPC) based on an active metasurface is proposed, which can regulate the ideal plane wave and the spherical wave as a cladding of the horn antenna. The metasurface unit is composed of a single-layer F4B dielectric substrate and two double-cross metal strips with a p–i–n diode on the top and seven vertical metal strips on the bottom. One RPC prototype with 15 × 15 units has been fabricated and measured when it regulates an ideal plane wave. By controlling the states of diodes, the RPC can realize the linear-to-circular polarization conversion (LCPC) or the linear polarization maintaining (LPM) function from 2.5 to 3.64 GHz. Furthermore, the RPC is used as the cladding of a horn antenna for high integration in practical applications. The measured results show that this RPC-antenna system can still achieve LCPC or LPM function from 3.1 to 4.5 GHz. It is worth mentioning that the 3 dB axial ratio beam width of RPC can cover from −65° to 65° in LCPC. The proposal has advantages of a wideband, simple biasing network, and easy fabrication and integration, which can be widely applied in modern wireless communication systems. [ABSTRACT FROM AUTHOR]

A reconfigurable metamaterial multiband antenna operating an octa-band resonating mode is designed for IoT wireless applications. Metamaterial cell split ring resonator (SRR) and quasi-complementary split ring resonator (CSRR) are printed on the back and front sides of the proposed antenna design to achieve the multiband characteristics. The PIN diode is implemented in a slotted ground section of the antenna structure to get different wireless standards by switching the diode ON/OFF. During reverse biased (OFF) mode of diode antenna operating at eight resonant frequencies 2.42, 4.34, 5.81, 8.45, 11.02, 13.98, 16.12, and 18.87 GHz covering the IoT wireless standards such as S, C, X, Ku, and K band to identify a variety of wireless applications such as WLAN, WAIC, ITU, Satellite, and radar communication. Simple structure, stable radiation pattern, multiband operation, frequency band reconfigurability feature, reasonable gain, and efficiency are the significant features of the proposed metamaterial multiband antenna. [ABSTRACT FROM AUTHOR]

This letter presents a wideband multi-linear polarization reconfigurable antenna, which has the ability to switch among four linear polarizations at rotation angle of 45°, namely 0°, 45°, 90°, and -45°. Its main structure consists of three layers of substrates and a reflective cavity. Four pairs of crossed bow-tie dipoles are used as the primary radiators, and the polarization switching is realized by controlling the ON/OFF states of four pairs of PIN diodes between feeding source and the dipoles. In addition, circular ring and reflective cavity structures are used for enhancing the operating bandwidth, stabilizing the radiation patterns, and increasing the gain. Finally, the simulation and measurement results both demonstrate that the antenna exhibits an overlapped impedance bandwidth of 42.6% (2.4 GHz-3.7 GHz) for all polarization states, and it remains a steady radiation pattern within the operating bandwidth. With these features, the design can be used in wireless communication systems in the 5G sub-6 GHz band. [ABSTRACT FROM AUTHOR]

Wireless communication systems have grown rapidly, moving towards being highly compact, intelligent, and flexible to adapt to changing operating requirements. Multifunctional and highly versatile antennas are key in this development to ensure system quality. Reconfigurable antennas, particularly regarding polarization, allow frequency reuse and enable the mitigation of fading effects. This work presents a square microstrip patch antenna operating in the ISM 5.8 GHz band with reconfigurable polarization by controlling its feeding. This antenna has four different states through the application of a symmetrical DC voltage that controls an RF circuit with PIN diodes. As a result, the microstrip patch can operate with three different polarizations: linear polarization and both circular polarizations (right-handed and left-handed). The antenna was fabricated to validate the proposed concept. The good agreement between the measurement and the simulation results was possible to observe regarding its polarization behaviour, impedance adaptation and radiation pattern. [ABSTRACT FROM AUTHOR]

In the current prevalent complex electromagnetic (EM) environment, intelligent methods for versatile and integrated control of EM waves using compact devices are both essential and challenging. These varied wave control objectives can at times conflict with one another, such as the need for broad absorption to remain inconspicuous, while also requiring enhanced backward scattering for highly reliable tracing and secure communication. To address these sophisticated challenges, a microwave‐frequency reconfigurable tri‐mode metasurface (RTMM) is introduced. The proposed innovation enables three distinct operational modes: broadband low observation, enhanced EM wave tracing, and backscatter communication over a wide‐angle range by simple control of the PIN diodes embedded in each meta‐atom. The proof‐of‐concept demonstration of the fabricated prototype verified the switchable tri‐mode performance of the RTMM. This proposed RTMM can be adapted to various applications, including EM shielding, target detection, and secure communication in complex and threatening EM environments, paving the way for environmentally‐adaptive EM wave manipulation. [ABSTRACT FROM AUTHOR]

We propose a binary amplitude-modulated conformal meta-surface with every meta-element capable of functioning as the leaky wave passage or the null radiating spot through dynamically tuning the PIN diodes over the meta-elements with ON or OFF states. In particular, the staggered arrangement of the meta-elements forms a dense radiating array with 0.1 wavelength periodicity and every radiating patch consists of dual hourglass shaped slots stacked over the coupled feed of substrate integrated waveguide slits. Such a design, on the basis of binary amplitude-modulated conformal meta-surface frames, can achieve wide-angle steerable fan-beam scanning, while possessing the precise beam direction with less than one tenth of the 3 dB beamwidth. Thus, this should pave the way for building up more advanced contemporary conformal wireless communication systems over different platforms. [ABSTRACT FROM AUTHOR]

In this article, the design and analysis of a compact octa‐band antenna employing the PIN diode to realize frequency reconfigurable characteristics is presented. The presented antenna is backed by a partial ground plane and printed on top of a 1.53 mm thicker FR4 substrate. The antenna size is very compact (25 mm × 14 mm × 1.53 mm), and can be readily incorporated with many other RF front‐end circuits. The presented antenna consists of a semi‐heptagonal, semi‐hexagonal, inverted L‐shaped, and inverted Z‐shaped monopoles. Depending on the position of the lumped element switch, the presented antenna can operate in eight different frequency modes. The investigated antenna realizes Penta/Triple band characteristics by turning ON/OFF the PIN diode positioned between the inverted L‐shaped monopole and feedline. While in ON state, the investigated antenna covers five unique frequencies 1.82 GHz (DCS/5G NR n70), 2.43 GHz (Bluetooth/RFID), 3.75 GHz (LTE 42–43/5G NR n77/Wi‐MAX), 5.4 GHz (U‐NII‐2A & ‐2B), and 5.84 GHz (U‐NII‐3 & V2X) and in OFF state, the antenna covers three unique frequencies 1.95 GHz (PCS/UMTS/LTE 34–37), 2.59 GHz (LTE 2500 & WLAN 2.4 GHz), 4.71 GHz (5G NR n79 & WLAN 5GHz) for wireless applications. The investigated antenna exhibits excellent impedance bandwidths of 1.69–1.9 GHz (BW = 11.6%), 1.8–2.1 GHz (BW = 15.4%), 2.37–2.56 GHz (BW = 7.7%), 2.4–2.7 GHz (BW = 11.8%), 3.49–4.2 GHz (BW = 18.4%), 4.3–5.55 GHz (BW = 25.4%), 5.2–5.52 GHz (BW = 6%), and 5.78–5.9 GHz (BW = 5.5%) at 1.82/1.95/2.43/2.59/3.75/4.71/5.4, and 5.84 GHz, respectively. The measurements demonstrate that the designed antenna has omnidirectional radiation characteristics with 1.15–4.4 dBi gain. The proposed design's simulated and measured results are compared, and show good agreement. [ABSTRACT FROM AUTHOR]

A multifunctional transmission line (TL) based on spoof surface plasmon polaritons (SSPPs) is proposed for dynamical switching features among bandpass, band‐stop, and dual‐band phase shifting functionalities. Different operating modes can be controlled in real‐time by changing the states of the Positive Intrinsic Negative (PIN) diodes synchronously. The dispersion properties of the spoof plasmonic unit cell and transmission characteristics of the tunable PIN‐diodes‐loaded spoof plasmonic TL are investigated to highlight the basic theory and method. A prototype of the proposed TL composed of five cascaded unit cells is fabricated and tested for proof‐of‐concept validation. In the ON state of the PIN diodes, the measured −3 dB transmission frequency bandwidth ranges from 3 to 8.1 GHz for the bandpass characteristic. In the OFF state, the measured −10 dB rejection band spans from 3.7 to 5.6 GHz for the bandstop characteristic. When the diodes are switched between ON and OFF states, the measured dual‐band phase shifts vary from 192° to 203° and 248° to 292° in the 3.1–3.4 GHz and 6.1–9.4 GHz frequency bands, respectively. The validated switchable features of the TL pave the way for applications of tunable SSPPs in large‐scale integrated circuits and smart wireless communication systems. [ABSTRACT FROM AUTHOR]

Currently, various microwave filter designs contend for the use in wireless communications. Among several microstrip filter designs, the tunable filter presents more advantages and better prospects for wireless communication applications, being compact in size, cost effective, and light in weight. These reconfigurable microwave filters can reduce the number of switches between the electronic components. The number of switches among the electronic devices can be decreased using tunable BPF. The tunable BPF is designed for X-band satellite communication applications as well as n77, n78, and n79 5G applications, and HSCH 3486 PIN diode is used to achieve the filter's tunability. An impedance bandwidth of 2.4 GHz and 2 GHz (fractional bandwidth of 25%) has been achieved with an S21 less than -1.5 dB, -2 dB and S11 of -22 dB and -31 dB at both the resonating frequencies. Semicircular cavity bandpass filter has been designed with the center frequency of 3.7 GHz. Switching between the two passbands has been obtained by attaching a PIN diode between the input and output feed lines. [ABSTRACT FROM AUTHOR]

In the proposed communication, a 2 × 2 and 4 × 4 antenna array with the capability of rejecting dual interfering bands is presented for multiband wireless applications including Ultrawideband (UWB) and X-band. Reconfiguration of notched bands is controlled using high-frequency switching devices (RF-PIN diodes). MIMO antenna configuration is formed by the combination of the Fork-shaped patch providing wideband bandwidth with Γ-T-shaped stub attached with the patch, which acts as bandstop filters for WiMAX and WLAN bands on one plane. Novel Ω-shaped ground is printed on the opposite plane, which provides good matching of impedance. The good matching of the results suggests accuracy in simulation and measurement environment with prototype in terms of frequency, time-domain, far-field and diversity MIMO performance. [ABSTRACT FROM AUTHOR]

With the continuous advancement of technology, there is an increasing need for innovative solutions that can handle complex applications such as haptic communications, Internet of Things for smart cities, automation, and manufacturing. One technology that has received much attention is the phase reconfigurable metasurface for reconfigurable intelligent surfaces (RISs). The RIS demands low-power consumption, simple configuration, angular stability, and polarization insensitivity. The use of phase reconfigurable metasurfaces provides benefits such as low cost, low power consumption, and improved communication coverage and quality. This article introduces a reconfigurable combined-loop metasurface that can effectively manipulate phase reflection. This is achieved by incorporating four PIN diodes between two meta-atoms of a 2 × 2 periodic array within a single-layer metallic structure. By controlling the state of the PIN diodes, which can be switched into 16 different states, the metasurface can achieve various phase reflections. The proposed structure has validated a 32× 32 metasurface through numerical simulations and experiments that exhibit promising results, demonstrating its potential for use in 6G applications. [ABSTRACT FROM AUTHOR]

Recently, reconfigurable coding metasurfaces have attracted extensive attention due to their dynamic and flexible manipulation of electromagnetic (EM) waves, making them an effective solution to connect physical reality and information science. Nevertheless, most previously reported reconfigurable metasurfaces suffer from limited applications, as they solely possess either phase or amplitude modulation. In this article, we propose a reconfigurable coding metasurface that can regulate both phase and amplitude response independently. In the field of the metasurface, the phase response can tailor the wavefronts, and the amplitude response can adjust the redistribution of the energy of the EM waves. Specifically, by integrating a PIN diode into the meta-atom and controlling its bias voltage, the reflection phase can be switched between two opposite phases with a phase difference of about 180°, and the reflection amplitude can be manipulated from 0.02 to 0.98 continuously at 11 GHz. The unit element consists of simple multi-layer structures, reducing its production cost and processing difficulty. By loading 1-bit phase code and multi-bit amplitude code to each unit element severally, this metasurface can modulate the distribution of reflected EM waves in two-dimensional (2-D) space while simultaneously suppressing the sidelobes for any quantity of scattered beams over a wide operating band ranging from 10.5 to 11.5 GHz. This metasurface exhibits promising potential for manipulating the distribution of EM wave energy and shaping of EM beams, which can be expected to facilitate wireless communication technology. [ABSTRACT FROM AUTHOR]

In this paper, we propose a reconfigurable intelligent surface (RIS) that can dynamically switch the transmission and reflection phase of incident electromagnetic waves in real time to realize the dual-beam or quad-beam and convert the polarization of the transmitted beam. Such surfaces can redirect a wireless signal at will to establish robust connectivity when the designated line-of-sight channel is disturbed, thereby enhancing the performance of wireless communication systems by creating an intelligent radio environment. When integrated with a sensing element, they are integral to performing joint detection and communication functions in future wireless sensor networks. In this work, we first analyze the scattering performance of a reconfigurable unit element and then design a RIS. The dynamic field scattering manipulation capability of the RIS is validated by full-wave electromagnetic simulations to realize six different functions. The scattering characteristics of the proposed unit element, which incorporates two p-i-n diodes have been substantiated through practical implementation. This involved the construction of a simple prototype and the subsequent examination of its scattering properties via the free-space measurement method. The obtained transmission and reflection coefficients from the measurements are in agreement with the anticipated outcomes from simulations. [ABSTRACT FROM AUTHOR]

This study introduces innovative designs for frequency-reconfigurable antennas that utilize ring resonators combined with either PIN diodes or RF switches. These designs enhance the versatility, adaptability, and overall performance of the antennas in wireless communication systems. By controlling the switches and ring resonator, the antenna's resonant frequencies and bandwidths can be adjusted, allowing for compatibility with various communication standards and frequency ranges. The proposed antenna exhibits four distinct operational states, each characterized by different resonance frequencies and operating frequency bands. Return loss, radiation pattern, radiation efficiency, and surface current distribution are analyzed for each state. State-1 (ON-ON) and State-2 (OFF-ON), which are characterized by resonance frequencies of 2.4 GHz and 3.33 GHz respectively, offer ranges suitable for Wi-Fi, Bluetooth, ISM, and IoT applications. State-3 (ON-OFF), with a resonance frequency of 3.0 GHz and bandwidth spanning from 2.59 GHz to 3.643 GHz, complies with Wi-Fi, Wi-Fi 6, and IoT requirements. State-4 (OFF-OFF) covers the band centered around 3.45 GHz. It is compatible with many applications such as 5G mid-band, Wi-Fi 6E, IoT, and cellular systems. The proposed antenna designs are versatile and compact since the overall antenna dimensions are 25 × 18 × 1.6 mm3. The radiation efficiency of the antenna configuration varies depending on operational states. By utilizing the advantages of both ring resonators and RF switches, the proposed antenna configurations offer new solutions that enhance their performance in wireless communication systems. This study compares the effects of using PIN diodes and SPDT switches on the performance of antennas and also examines the DC biasing effect on antenna characteristics. The simulation results are validated by the experimental analysis. The proposed antenna designs offer a new approach for wireless communication systems by using both ring resonators and RF switches. [ABSTRACT FROM AUTHOR]

In order to meet the increasing demand for adjustable devices in the modern wireless communication system, a compact bandpass filter with active switchable passband is proposed. The filter is based on the half mode substrate integrated waveguide (HMSIW), and uses its cut-off characteristics to form the lower stopband. The resonant characteristics of a quarterwavelength shorted stub generates a transmission zero (TZ) at higher frequency, which forms the upper stopband. The active control of DC power supply determines the biased states of PIN diodes to change the electrical size of the filtering parts. When the diodes are reverse biased, the filter works in C band with the passband of 3.9-5.2 GHz; when the diodes are forward biased, the passband shifts to S band of 2.7-3.6 GHz. The 28.6% relative bandwidth in both frequency bands remains constant. The simple design realizes the active switching between bands, providing a promising idea for active adjustable devices. [ABSTRACT FROM AUTHOR]

A quad-element reconfigurable radiation pattern Multiple Input Multiple Output (MIMO) antenna is designed for WLAN and 5G applications suitable for indoor wireless communications. It consists of four radiating elements that operate over triband frequencies 2.4, 3.5, and 5.5 GHz. Moreover, the pattern diversity is obtained by introducing two diagonally crossed slots in the radiator to steer the main beams of the antenna in 8 different angular directions using eight PIN diodes. The overall physical dimension of the proposed antenna is about 0.55 × 0.55λ0. In addition, an Acrylonitrile Butadiene Styrene (ABS) enclosure is designed, and the performance of the proposed antenna is evaluated. The measurement results show that the proposed antenna has an impedance bandwidth of 4.18%, 14.13%, and 28.5% at the said frequencies, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a compact tuned reconfigurable microstrip antenna for fifth generation (5G) mobile communications is designed to operate at 28 GHz or 38 GHz or both frequencies. The proposed antenna can be reconfigured by using a group of PIN diodes switches across a slit in the upper traditional patch antenna or through the ground plane side. The tuning between the 28 GHz and 38GHz frequency bands can be achieved through ON/OFF states of the PIN diodes switches. The tuned reconfigurable antenna is simulated using CST software package and then fabricated and measured. The simulated and measured results show good agreement with a little deviation. The proposed tuned antenna is small in size with 18×11.25 mm² overall area. [ABSTRACT FROM AUTHOR]

This paper presents a novel frequency reconfigurable antenna design for sub-6 GHz applications, featuring a unique combination of antenna elements and control mechanisms. The antenna is composed of an outer split-ring resonator loaded with an inner spiral resonator, which can be adjusted through the remote control of PIN diode or Single Pole Double Throw (SPDT) switches. The compact antenna, measuring 22 × 16 × 1.6 mm3, operates in broadband, or tri-band mode depending on the ON/OFF states of switches. The frequency reconfigurability is achieved using two BAR64−02V PIN diodes or two CG2415M6 SPDT switches acting as RF switches. SPDT switches are controlled remotely via Arduino unit. Additionally, the antenna demonstrates an omni-directional radiation pattern, making it suitable for wireless communication systems. Experimental results on an FR-4 substrate validate the numerical calculations, confirming the antenna's performance and superiority over existing alternatives in terms of compactness, wide operating frequency range, and cost-effectiveness. The proposed design holds significant potential for applications in Wi-Fi (IEEE 802.11 a/n/ac), Bluetooth (5 GHz), ISM (5 GHz), 3G (UMTS), 4G (LTE), wireless backhaul (4G and 5G networks), WLAN (IEEE 802.11 a/n/ac/ax), 5G NR n1 band, and Wi-Fi access points due to its small size and easy control mechanism. The antenna can be integrated into various devices, including access points, gateways, smartphones, and IoT kits. This novel frequency reconfigurable antenna design presents a valuable contribution to the field, paving the way for further advancements in wireless communication systems. [ABSTRACT FROM AUTHOR]

The realization of dynamic polarization rotation based on the metamaterial or metasurface is always a concerned issue in electromagnetic manipulation. In this Letter, a transmission-type switchable metasurface is proposed, which can rotate the linear polarized (LP) wave to arbitrary angle among ±45° in a wide frequency band. The polarization rotation metasurface (PRM) consists of a polarization conversion surface and a partially reflective surface. By controlling the resistances of PIN diodes, the PRM can change the polarization angle of transmitted LP wave. To verify the design, a prototype of the proposed PRM is fabricated and tested, and the simulated and measured results are in good agreement. According to the measured results, the fractional bandwidth at each state of prototype is larger than 20.4%. The overlapping operational band of the prototype is from 3.03 to 3.60 GHz, where the transmission coefficient remains higher than –2 dB, and the axial ratio of transmitted wave is higher than 15 dB. The proposed design may have the application potential in target detection, wireless communication, and polarimetric imaging. [ABSTRACT FROM AUTHOR]

In this article, the proposed antenna structure is designed for modern wireless communication systems. The antenna structure is consistent with 11‐unit cells of composite right–left‐hand (CRLH) inclusions mounted on an FR4 substrate. Therefore, the antenna size is miniaturized effectively to 30 × 20 mm2 to cover the frequency bands around 2.45 GHz, for Wi‐Fi, and 4.2–6 GHz, for sub‐6 5G, networks. The design process is conducted on a circuit model and numerical simulations by evaluating the unit cell transmission phase spectra. For this, a comparison between the circuit model and the numerical simulations is invoked for validation. Such an antenna is found to provide a maximum gain of 6.2 dBi at 4.6 GHz. Next, 11 PIN diodes control the current motion between the antenna patch and the CRLH array. Therefore, PIN arrays are connected to the patch and the ground plane to maintain the surface current motion that realizes main lobe beam steering. The proposed antenna performance is simulated numerically using the CSTMWS software package. Then, it is fabricated and tested experimentally for validation. An excellent agreement is achieved between the simulated and measured results. Finally, it is found this antenna provides excellent beam steering −92° to 92° to suit many modern networks. [ABSTRACT FROM AUTHOR]

This paper presents, a novel cactus shaped frequency reconfigurable antenna for sub 10 GHz wireless applications. PIN diode is utilized as an electrical switch to achieve reconfigurability, enabling operation in four different frequency ranges. In the switch ON state mode, the antenna supports 2177-3431 and 6301-8467 MHz ranges. Alternatively, the antenna resonates within 2329-3431 and 4951-6718 MHz while in the OFF state mode. Radiation efficiency values, ranging from 68% to 84%, and gain values, ranging from 1.6 to 4 dB, in the operating frequency bands. the proposed antenna satisfy the practical requirements and expectations. The overall planner dimensions of the proposed antenna model is 40 × 21 mm2. Moreover, the measurement results from the prototype support the simulation results. Based on the frequency ranges supported by the antenna, it can be used for multiple wireless standards and services, including Worldwide interoperability and Microwave Access (WiMAX), Wireless Fidelity (Wi-Fi), Bluetooth, Long Term Evolution (LTE) and satellite communications. This increases its applicability for use in mobile terminals. [ABSTRACT FROM AUTHOR]

In this paper, a new design of reconfigurable stop-band in UWB band-pass filter based on resonator-loaded slot-line is presented and implemented. The obtained stop-band response is performed by embedding a single PIN diode in the resonator. When the PIN diode state is OFF, a UWB response is achieved. Nevertheless, when the diode is in ON, a notch is created in the UWB filter. In addition, the obtained notch-band could be adjusted by modifying the length of the microstrip resonator-loaded slot-line. Then, a stop-band, created at 5.8 GHz for wireless communication (WIFI), is designed. The obtained results show that insertion loss is less than 0.3 dB, return loss is greater than 14 dB and the group delay is 0.23 ns at the entire UWB band. [ABSTRACT FROM AUTHOR]

This article presents a circular microstrip patch antenna loaded with three complementary split rings (CSRRs) on the ground plane for pattern agility features. The antenna resonated at 5.3 GHz and accommodated the frequency spectrum from 5.1–5.7 GHz for different CSRR combinations. The reconfigurable pattern feature has been produced with three p-i-n diode combinations integrated with the CSRR slot on the ground patch. The CSRR combinations are utilized to change the radiation phase concerning the primary radiating circular patch. The proposed antenna radiation beam can steer from ±15°, 180°, and 0° of the broadside pattern in the elevation plane with a satisfactory gain of 3 dBi. The phase variation for various CSRR combinations concerning the primary antenna is presented. The presented antenna is fabricated on an FR4 substrate and tested in an anechoic environment; the tested results verify the pattern agility of the antenna. The demonstrated antenna is suitable for modern wireless communications like LTE and Cognitive radios. The compact size, simple biasing, and low cost are added advantages of the antenna. [ABSTRACT FROM AUTHOR]

This paper presents the design of a triband antenna that can be electronically configured to operate at different frequencies. The proposed antenna is design to operate at sub-6GHz bands at 2.45 GHz (ISM, Wi-Fi, and WLAN), 3.3, 3.5 & 3.9 GHz (WiMAX), and 4.1 & 4.9 GHz (4G & 5G). This is achieved by connecting two open-ended stubs to a modified triangular patch radiator using PIN diodes. The antenna's performance was optimized using a 3D electromagnetic solver and its performance was verified through measurements. Moreover, the conformal analysis done on the antenna shows that the proposed technique can be used in moderately flexible wireless devices without compromising the antenna's gain, radiation efficiency and radiation patterns. These characteristics makes the proposed antenna applicable for various wireless communication systems and devices. [ABSTRACT FROM AUTHOR]

Featured Application: The proposed metasurface in the article can be used in millimeter wave sensing and 5G wireless communications. A programmable coding metasurface provides unprecedented flexibility to manipulate electromagnetic waves dynamically. By controlling the peculiarity of subwavelength artificial atoms, devices with metasurfaces perform various functionalities. In this paper, a compact programmable coding metasurface with PIN diodes is proposed to realize the beam steering in the Ka band. The phase distribution on the metasurface can be actively controlled by switching the states of each meta-atom. By tuning the phase gradient along the metasurface plane, the reflective beam can scan all directions in the upper half-plane. In addition, the compact metasurface is easier to integrate, which could expand the fields of applications. The full-wave simulation results show that the radiation direction of the main lobe is consistent with the theoretical calculation results, and the maximum steering angle of simulation is 60°. As experimental verification, a prototype was processed and the functionality of beam steering in the xoz plane and in the yoz plane was tested. Experimental results show that the designed metasurface can achieve beam steering in both planes, and the maximum scan angle is 45° in the xoz plane. The proposed metasurface opens a new way of beam steering in half space, which may have potential applications in sensing and wireless communications in millimeter waves. [ABSTRACT FROM AUTHOR]

This article proposes a novel multifunctional wideband reconfigurable antenna with a frequency selective surface (FSS) reflector to improve gain across all operating bands. Initially, a wideband trapezoidal monopole antenna with a 138% impedance bandwidth (1.53–8.45 GHz) on a FR‐4 substrate with a thickness of 0.80 mm and an area of 51 × 56 mm2 was designed. In order to achieve multifunctionality, two inverted L structures with two rectangular slots were introduced at the ground plane. Each slot functions as a filter, producing various resonating bands. To obtain the desired resonating frequency bands, the effective length of the slot was changed by strategically placing RF switching element PIN diodes. The proposed reconfigurable antenna can switch between 10 different frequency bands. To improve the gain of the proposed reconfigurable antenna, a novel FSS reflector with a 5 × 5 array of elements is placed 1.01λ (34.54 mm) below the proposed antenna. The application of the FSS results in a 3–6 dBi improvement in antenna gain, not only for the wideband range, but also for all operating frequency bands. Over the entire operating bandwidth, the radiation efficiency ranges from 93% to 75%. For GPS, RADAR, LTE42/43, WLAN, WiMAX, STM‐Link, and UMTS applications, the proposed antenna operates in a wideband state, three single band states, four dual band states, and three tri band states. This work provides more antenna functionality at a lower cost, as well as significantly reduced size and space requirements. The proposed antenna can be easily integrated into portable electronic devices for a variety of wireless applications due to its broad switching capability and unique feasibility. [ABSTRACT FROM AUTHOR]

The present work demonstrates the design of a wideband 2 x 1 reconfigurable beam steering array for wireless communication systems. The designed antenna is powered by a microstrip line and consists of a two rectangular-shaped radiating elements and a rectangular planar ground. Its dimensions are as follows: 0.67A0 x 0.53A0 x 0.03A0. It executes three reconfigurable operating states by turning on and off two PIN diodes to change the direction of the main beam, as well as a beam tilt ranging from (±30°) to (±38°). A progressive analysis in order to enhance the antenna characteristic performances is furnished. The proposed reconfigurable antenna bandwidth is 18.18% (simulated), 18.84% (theoretical), and 19.42% (measured). The presented antenna has a maximum gain of 8.62dB (simulated) and 8.45dB (measured), and a higher efficiency ratio of 80% to 86% over the operating band (5GHz-6GHz). The designed antenna is fabricated using a low loss Rogers RT5880 substrate of 2.2 relative permittivity. The simulated, theoretical, and measured results are presented and exhibit a good accord, including the Su parameter and radiation patterns. In addition to the pattern reconfiguration, the obtained results are useful in order to improve the overall gain, antenna bandwidth and efficiency. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a design of a reconfigurable printed antenna circuitry for 5G portable devices is proposed based on a miniaturized structure. Thus, the proposed antenna is structured as a printed circuit monopole with a coplanar waveguide port (CWP). The ground proposed CWP is designed as an L‐shaped reflector in order to increase the directivity of the proposed antenna toward a certain direction. A matching circuitry based on a fractal Minkowski structure of the first order is inductively attached to the antenna design to increase the antenna bandwidth. To control the antenna performance, the matching circuit is connected to the L‐shaped reflector through four PIN diodes. The effects of different switching scenarios on the antenna performance are tested numerically and experimentally for validation. It is found that when all diodes are switched ON, such antenna shows two frequency bands, S11 < −10 dB, from 3.5 to 3.7 GHz and from 5.08 to 6.9 GHz. Nevertheless, the antenna gain is found to be about 3.47 dBi at 3.6 GHz and 3.69 dBi around 5.1 GHz. The other switching scenarios are tested and presented in this work. It is observed that the PIN diodes' switching affects significantly on the antenna directivity and the radiation patterns. The antenna performance is parametrically analyzed using CST MWS based on a numerical technique and based on an analytical circuit model. The proposed antenna is fabricated and tested to be compared against the theoretical results. An excellent agreement was obtained between the simulated and measured results. [ABSTRACT FROM AUTHOR]

The concept of dual-polarized reconfigurable reflectarray (RRA) featuring dual-polarized beam control is proposed and demonstrated using a dual-channel programmable metasurface. The p-i-n diodes are incorporated into each metasurface element as the active components to provide independent phase control in two orthogonal polarization channels. By altering the working states of each p-i-n diode, well-defined beam scanning can be obtained. Element design, focal diameter ratio selection, and discretized phase distributions are carefully optimized to ensure stable radiation performance of the proposed RRA. As verification, a prototype consisting of 20 $\times20$ elements is fabricated and measured, which is controlled by a field programmable gate array-based controller. Measured results show that wide-angle beam scanning up to ±40° can be obtained around 7.45 GHz, with peak gains of 21.13 and 20.89 dBi in dual channels, corresponding to aperture efficiencies of 16.35% and 15.47%. The proposed dual-polarized RRA brings a new freedom in polarization manipulations for versatile beam scanning, which provides promising applications in wireless communication and tracking/detecting systems. [ABSTRACT FROM AUTHOR]

In this paper, a compact frequency and polarization agile patch antenna is presented. The antenna comprises a square patch with truncated corners along with a triangular slot etched at the center of the patch. Pin diodes are used to bridge the gap between the truncated corners and center triangular region with a radiating square patch. By appropriately biasing the pin diodes the antenna achieves frequency and polarization diversity. The antenna achieves five distinct states with three linear polarization (LP) states operating at three different frequencies and two circular polarization (LHCP/RHCP) states operating at the same frequency. The antenna gives a −10 dB impedance bandwidth of 95 MHz (1.825–1.92 GHz) in the GSM band for LP state 1, 115 MHz (2.365–2.48 GHz) in the ISM band for LP state 2, 145 MHz (2.08–2.225 GHz) in UMTS band for LP state 3, 100 MHz (2.1–2.2 GHz) UMTS band for CP state 4 and 5. The antenna attains a measured peak gain of ∼4.8 dBi at LP states and ∼4.54 dBi at CP states in its operating band. [ABSTRACT FROM AUTHOR]

Reconfigurable antennas are the suitable candidates for modern wireless communication systems because of various advantages viz. compact size, low front-end processing, good isolation, sufficient out of band rejection and multifunctional capabilities. So, here we have presented a new compact frequency and pattern reconfigurable antenna (FPRA). Parametric analysis, design and results of the FPRA are discussed in detail. The FPRA has a circular patch surrounded by a ring stub on top layer and a slotted defected ground structure (DGS) on bottom layer. The microstrip feed line is used to feed FPRA. To achieve frequency and pattern reconfiguration, the ring stub is attached or detached from the feed line with the help of two HPND-4005 PIN diodes. In frequency reconfiguration mode, the FPRA is able to switch among UWB (3.05 to 11.45 GHz), Multiband (4 GHz, 6.5 GHz, and 9.2 GHz) and Narrowband (7.1 GHz) modes. The radiation pattern is nearly omni-directional in UWB and narrowband operation whereas in multiband case the pattern can be reconfigured without affecting the operating frequency bands. The reflection coefficient of FPRA is less than − 15 dB and the gain is more than 2 dBi for all operating modes. The proposed FPRA is fabricated and verified. The measured reflection coefficient graphs and group delay graphs show adequate alignment with the simulated results. Nearly constant group delay over a UWB frequency range confirms good time domain characteristics of the FPRA. So, the proposed FPRA is suitable for Ultra-wideband (UWB) and Cognitive Radio (CR) applications. [ABSTRACT FROM AUTHOR]

Purpose: Modern wireless communications need novel microwave components that can be effectively used for high data rate and low-power applications. The operating environment decides the severity of the noise coupled to the transceiver system from the ambient environment. In a deep fading environment, narrowband systems fail where the wideband systems come for rescue. Thus, the microwave components are ought to switch between the narrowband and wideband states. This paper aims to study the design of a bandpass filter to meet the requirements by appropriately switching between the dual narrowband frequencies and single ultra-wideband frequency band. Design/methodology/approach: The design and implementation of a compact microwave filter with reconfigurable bandwidth characteristics are presented in this paper. The proposed filter is constructed using a hexagonal ring with shorted perturbation along one corner. The filter is capacitively coupled to the external excitation source. External stubs are connected to the corners of the hexagonal resonator to obtain dual passband characteristics centred at 2.1 and 4.5 GHz. The external stubs are configured to achieve bandwidth reconfigurable characteristics. PIN diodes are used with a suitable biasing network to obtain reconfiguration. In the reconfigured state, the proposed two-port filter offers a continuous bandwidth from 2.1 to 5.9 GHz. The roll-off rate along the band edges is improved by increasing the order of the filter. Findings: The proposed filter operates in two states. In state 1, the filter operates with dual frequencies centred around 2 and 4.5 GHz with insertion loss less than <1 dB and return loss greater than 13 dB with a peak return loss of 21 and 31 dB at 2.1 and 2.15 GHz, respectively. In state 2, the filter operates from 2.1 to 5.9 GHz with insertion loss less than 1 dB and return loss greater than 12 dB. The filter exhibits four-pole characteristics with a peak return loss greater than 22 dB. Thus, the fractional bandwidth of the proposed filter is 17% and 16% in state 1, whereas the fractional bandwidth is 95% in state 2. Originality/value: The proposed filter is the first of its kind to simultaneously offer miniaturization and bandwidth reconfiguration. The proposed second-order filter has two-pole characteristics in the narrowband state, whereas four-pole characteristics are realized in the wideband state. The growing interest in 4G and 5G wireless communications makes the proposed filter a suitable candidate for operation in the rich scattering environment. [ABSTRACT FROM AUTHOR]

Space-time-modulated metasurfaces can manipulate electromagnetic waves in space and frequency domains simultaneously. In this article, an analytical design of space-time-modulated metasurfaces with modulation elements composed of two paths, In-phase (I) and Quadrature (Q), is proposed. The model is derived analytically, the space-/frequency-domain manipulations are achieved by designing the dimension and time sequence of I and Q paths. In the specular reflection direction, an objective frequency shift of the reflected first-order harmonic can be obtained. While, in other directions, the opposite first-order harmonic can be easily controlled by changing the dimension of I/Q paths, and the objective first-order harmonic remains unchanged. Furthermore, with a small dimension of I/Q paths, the first-order harmonic can be used for beam scanning by predesigning the start time of the modulation element. To realize the space-time-modulated metasurface with the required periodically time-varying responses, 2 bit unit cells loaded with dynamically switchable pin diodes are used as I/Q modulation. Both the analytical and numerical results demonstrate that space- and frequency-domain manipulations of the reflected fields by the first-order harmonics can be simultaneously obtained. The proposed designs have potential applications in wireless communications, radar camouflaging, and cloaking. [ABSTRACT FROM AUTHOR]

This paper addresses the growing need for multifunctioning microwave components by proposing a miniaturized reconfigurable stopband filter. The compact size is the outcome of the novel metamaterial split-ring resonator used for realizing this filter. Six PIN diodes are used to achieve real-time frequency and mode reconfigurability. This filter is designed to reject three important frequencies in wireless communication systems: 1.9, 2.4, and 3.6 GHz. Moreover, depending on the use, it is possible to reject one, two, or all the three frequencies, which resulted in seven different cases with three possible modes: single, dual, or triple stopbands. A prototype was manufactured for this filter, and strong agreement between simulation and measurement results is observed. Due to its target bands, this reconfigurable stopband filter is suitable for various cellular communication technologies from 3 G and 4 G up to 5 G and many other S-band applications. [ABSTRACT FROM AUTHOR]

This work presents a novel proposal for a dual wideband circularly polarized (CP) reconfigurable antenna for wideband wireless communication applications. The circularly polarized characteristic is achieved by introducing a gap in the annular ring, which leads to the generation of traveling waves in circular patterns. The concentric annular ring patch is fed using a tapered 50 Ω microstrip line. Dual wideband characteristics are obtained by incorporating concentric annular rings and additional DGS (defective ground structure) to achieve wideband characteristics. By employing PIN diodes, the proposed approach facilitates reconfiguration, allowing for both left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) in either single or dual wideband operations. The CP antenna exhibits an impressive measured axial ratio bandwidth (ARBW) of 35 % (3438–4900 MHz) and 18.75 % (5154–6252 MHz). The measured return loss bandwidths of the proposed antenna are 18.40 % (3990–4799 MHz) and 35.17 % (5161–7364 MHz). The antenna, fabricated using FR4, is compact in size, measuring 0.56 λ o *0.56 λ o *0.01 λ o , and has a peak gain of 6.33 dBic. The simulated outcomes and hardware measurement findings agreed well. [ABSTRACT FROM AUTHOR]

This paper presents a dual-polarized bidirectional electronically reconfigurable beam-steering array (DBSA) for the first time, which integrates the beam-scanning capabilities of both dual-polarized reconfigurable transmitarray and dual-polarized reconfigurable reflectarray. First, a novel phase and direction reconfigurable dual-polarized element is proposed. Four PIN diodes are soldered onto the symmetric transmitting patches to tune the 1-bit transmission phase, while two PIN diodes are soldered onto the reflecting patches to tune the 1-bit reflection phase. By controlling the states of the PIN diodes, the DBSA element can achieve 1-bit reconfigurable phase in both transmission and reflection modes. Second, based on the proposed element, a 100-element DBSA prototype is fabricated and measured. At dual-polarization, the angles of the scanned beams can reach 45 ∘ and 222 ∘ in forward- and backward-spaces. Therefore, the proposed novel method opens a new avenue to designing a dual-polarized electronically reconfigurable spatially fed array antenna with full-space beam-scanning capabilities, and the proposed design is suitable for dual-polarized bidirectional wireless communication applications. [ABSTRACT FROM AUTHOR]

Fractal and reconfigurable antennas are the need of modern wireless communication systems that operate under dynamic scenarios catering to the diversified needs of modern wireless applications. In this dissemination, a novel multiband Fractal Reconfigurable Antenna (FRA) is presented and discussed using two RF PIN diodes as switching elements for electronic reconfiguration. It is analyzed using equivalent circuit concept and investigated in terms of various antenna performance parameters. The proposed FRA can operate in various frequency bands resonating at four different frequencies with switchable bandwidth and gain. The highest gain is observed to be about 8.37 dB at 9.68 GHz while the highest bandwidth is about 540MHz in the X-band. The simulation and measurement results obtained are found in agreement. The multiband characteristics of the proposed FRA make it useful for smart wireless communication applications in the S (2{4 GHz), C (4{8 GHz), and X (8{12 GHz) microwave bands. [ABSTRACT FROM AUTHOR]

We propose a theoretical mechanism and new coding strategy to realize extremely accurate manipulations of nonlinear electromagnetic harmonics in ultrawide frequency band based on a time-domain digital coding metasurface (TDCM). Using the proposed mechanism and coding strategy, we design and fabricate a millimeter-wave (mmWave) TDCM, which is composed of reprogrammable meta-atoms embedded with positive-intrinsic-negative diodes. By controlling the duty ratios and time delays of the digital coding sequences loaded on a TDCM, experimental results show that both amplitudes and phases of different harmonics can be engineered at will simultaneously and precisely in broad frequency band from 22 to 33 GHz, even when the coding states are imperfect, which is in good agreement with theoretical calculations. Based on the fabricated high-performance TDCM, we further propose and experimentally realize a large-capacity mmWave wireless communication system, where 256 quadrature amplitude modulation, along with other schemes, is demonstrated. The new wireless communication system has a much simpler architecture than the currently used mmWave wireless systems, and hence can significantly reduce the hardware cost. We believe that the proposed method and system architecture can find vast application in future mmWave and terahertz-wave wireless communication and radar systems. [ABSTRACT FROM AUTHOR]

This article presents a multiband antenna with the implementation of a metamaterial split-ring resonator (SRR), quasicomplementary split-ring resonator (CSRR), and slots to achieve octaband characteristics for wireless standards. Multiband features are accomplished by the implementation of the slot approach within the radiating section part and loading the SRR and CSRR cells. The electrical dimension is 0.256λ × 0.176 λ × 0.0128λ (32 × 22 × 1.6 mm3) of the proposed design, at a lower frequency of 2.4 GHz. The proposed design indicates the frequency-band reconfigurability nature by using the switching PIN diode placed at the slotted section of the ground plane. During the OFF state of switching, the element structure resonates in eight wireless communication bands covering various high-speed multiple applications of Internet of Things (IoT) regarding wireless standards S-band WLAN (WiFi, Bluetooth, Z-wave, wireless HART, and WBAN), lower C-band (WAIC, satellite communication transmission application), C-band WLAN, X-band (ITU region 2), Ku-band (direct broadcast satellite system and terrestrial microwave communication system service), and K-band (radar communication application) at 2.4, 4.3, 5.8, 8.5, 11.1, 13.9, 16.1, and 18.9 GHz, respectively, with S11 ≤ −10 dB. The antenna achieves an optimum peak gain of 4.23 dBi and radiation efficiency of 82.78% at operating frequency regarding wireless standards. The average efficiency of the proposed design is more than 70% for all resonant modes. The radiation characteristics (gain/efficiency/patterns/impedance matching) are shown in the stable and improved form at achieved wireless modes. [ABSTRACT FROM AUTHOR]

A new design of a frequency reconfigurable pentagon patch antenna for wireless communications is presented in this paper. Four PIN diodes, BAR63-02V, have been used on the ground plane to achieve the desired reconfigurability. The proposed patch antenna having dimensions of 26mm x 15mm has been designed using CST Microwave. The antenna is alimented by coaxial-probe and Rogers 3003 has been used as a substrate. Center frequencies are 2.44 and 4.52 GHz in operating Mode M1, 2.83 and 7.11 GHz in operating Mode M2, 2.68 and 4.66 GHz in operating Mode M3, 3.24 and 6.19 for operating Mode M4, 3.32, 6.32 and 6.62 GHz for operating Mode M5. [ABSTRACT FROM AUTHOR]

In the present day scenario, the need for 5G technology is increasing daily, so we design a reconfigurable antenna working in the millimeter-wave range (25 GHz-30 GHz). The antenna is designed using HFSS software, and the antenna is loaded with compact planar metamaterial. This design includes 9 unit cells arranged in a 3×3 array, and each unit cell is made up of a hexagonal patch surrounded by a split ring resonator. Apart from this two unit cells are connected using pin diodes. By operating these two pin diodes in different modes, we get four different characteristics. The designed antenna radiates at 27 GHz with a gain of 2.6 dB to 4 dB. The designed antenna is compact and easy to fabricate with dimensions of 30mm × 23 mm. [ABSTRACT FROM AUTHOR]

This work presents the design and analysis of a beam switching antenna for VANET, Wi-Fi, and WiMAX wireless communication systems. The proposed reconfigurable antenna is powered by a coaxial cable and consists of a circular patch, six fish-shaped radiating elements, and a circular planar ground. The antenna was constructed on a Rogers RT5880 substrate. Its dimensions are as follows: 0.81λ0 × 0.81λ0 × 0.03λ0. It performs six reconfigurable operating states, at the same frequency, by controlling the activation and deactivation of six PIN diodes to change the beam's direction. A theoretical equivalent circuit model of the antenna is extracted. A progressive analysis of improving the antenna characteristic performances is provided. The bandwidth of the proposed antenna is 9.07% (measured), 9.62% (simulated), and 9.31% (theoretical). The designed antenna has a maximum gain of 9.57 dB for all pattern states and a superior efficiency ratio from 85% to 95% over the operating range (5.54 GHz–6.10 GHz). The proposed reconfigurable antenna is fabricated. Measured, simulated, and theoretical results are given and show good agreement, including reflection coefficient (S11) and radiation patterns. [ABSTRACT FROM AUTHOR]

A 2 × 2 circularly polarized array is presented whose polarization diversity can be electronically controlled. The antenna array utilizes 180° rat-race and two pair of hybrid couplers. The antenna's CPW feed-line comprises of a reconfigurable sequentially rotated network. Reconfigurable property is achieved by employing two pairs of PIN diodes that determine the right-handed and left-handed circular polarization, known as state1 and state2 respectively. Moreover, vias are used to provide a good transition among CPW feed-line to microstrip-line. Measurements confirm presented array exhibits broadband operation which makes the antenna applicable for C band and IEEE 802.16.a systems. The measured improved and optimized impedance bandwidth of the proposed arrays structure is 3.2–8.0 GHz in state#1 and 3.1–7.7 GHz in state#2 for S11 ≤ − 10 dB and its 3 dB axial ratio is 4.8–7.31 GHz in state#1 and 4.9–7.2 GHz in state#2. The approximately maximum gain of antenna is about 7dBi. The Proposed antenna array with its optimized and modified feed-network is outstanding candidate for wireless communication systems. [ABSTRACT FROM AUTHOR]

Recently, programmable metamaterials or metasurfaces have been developed to dynamically edit electromagnetic waves for realizing different functions in the same platform. However, the proposed programmable metasurfaces can only control reflected or transmitted wavefronts in half‐space. Here, a "Janus" digital coding metasurface with the capabilities to program various electromagnetic functions in the reflected (with R‐codes) and transmitted (with T‐codes) waves simultaneously is presented. Three PIN diodes are employed to design the metaparticle, and the state of the PIN diodes can be switched to change the reflected and transmitted phases independently. Three schemes achieved by the proposed programmable metasurface are provided as illustrative examples, including anomalous deflections, beam focusing, and scattering reduction in the full space. As a proof‐of‐concept, a prototype composed of 10 × 20 metaparticles is fabricated and the measured results are in good agreement with the designs and numerical results, validating the full‐space modulations enabled by the programmable metasurface. It is expected that the new programmable metasurface can broaden the applications in stealth technologies, imaging systems, and the next generation of wireless communications. [ABSTRACT FROM AUTHOR]

To meet the requirements of miniaturization, multi-functions, and anti-interference of the antenna, this paper proposes a compact dual notch band frequency reconfigurable ultra-wideband (UWB) antenna. The antenna consists of an angle-cut rectangular radiation patch, a coplanar waveguide (CPW) structure, and a defective ground structure (DGS). A C-slot and an inverted U-slot are introduced to eliminate the interference of the Indian National Satellite band (INSAT), 5G band, and X satellite communication band. By controlling the PIN diodes across the two slots, the antenna can work in four states: UWB, two single notch bands, and one dual notch band. The impedance bandwidth in UWB mode is 2.9-12 GHz, with a relative bandwidth of 122%. The notch frequencies are 4.2-5.2 GHz and 6.2-8.1 GHz, respectively. In the passband of the antenna, the maximum gain is 7.17 dBi, and the group delay is less than 1 ns. The antenna size is 18x17x 1:6mm³, which is easy to integrate with the communication systems. The antenna can be freely switched between the UWB mode and each notch band mode, which can be applied to the UWB wireless communication systems. [ABSTRACT FROM AUTHOR]

This work discusses the effect of reconfigurability on a Sierpinski-carpet fractal microstrip patch antenna. The implementation of reconfigurability is achieved by modeling a PIN diode as a lumped RC element on HFSS (High Frequency Structure Simulator) simulation tool. The proposed antenna design is also fabricated and tested. It is highly miniaturized having a dimension of 9:5mm x 7:4mm and a significantly high impedance bandwidth which is desirable for most wireless communication applications. The resultant Fractal Reconfigurable Antenna (FRA) exhibits good performance parameters having frequency reconfigurability rendering it useful for Ku/K/Ka band applications. [ABSTRACT FROM AUTHOR]

In this letter, a novel wideband circularly polarized (CP) crossed dipole antenna with frequency reconfiguration is proposed. By introducing two quasi‐Sierpinski fractal orthogonal dipoles printed on both sides of the substrate, compact, broadband and low cross‐polarization characteristics are achieved. The proposed antenna can be switched flexibly over two frequency bands via controlling the states of the PIN diodes inserted in each arm of the crossed dipole. The measured −10 dB impedance bandwidths of the antenna are 63% in 2.23–4.27 GHz and 12.5% in 4.04–4.58 GHz, respectively. Meanwhile, the 3 dB axial ratio bandwidths are 34.7% in 2.5–3.55 GHz and 4.16% in 4.23–4.41 GHz, respectively. The proposed antenna is desired to be applied in the future wireless communication systems. [ABSTRACT FROM AUTHOR]

We present a novel X-band 1-bit reconfigurable transmitarray with excellent polarization conversion. The basic element consists of two layers of metal patterns connected by a metal through-hole and feed structures. The top layer is used to realize a 1-bit phase response by controlling the states of two PIN diodes; the bottom layer is composed of a rectangular patch with a U-slot to realize conversion from linear polarization to cross polarization. The agreement between simulation and measurement results indicates that when the diode states are switched in turn, this unit achieves the phase difference of cross-polarized transmitted waves within 180° ± 15° and high transmittance in a broad band. The scattering patterns demonstrate that beam splitting or multi-beam generation can be achieved by controlling the different coding sequences of each column unit. The element offers low transmission loss, wide bandwidth of 1-bit phase control, and small thickness for easy integration. Thereby, it has numerous potential applications in radar and wireless communications. [ABSTRACT FROM AUTHOR]