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This study presents a novel implementation of vanadium dioxide (VO2) phase change material in an electromagnetic (EM) surface with beam steering capabilities. For the first time, we present the design, fabrication, and measurement of a globally actuated, VO2-based beamforming reflective EM surface. We propose a design featuring complementary unit cells that enable beam steering with a single excitation, marking a pioneering use of low-loss VO2 in creating a complementary EM surface for the mmWave band. The unit cells incorporating VO2 exhibit low-loss characteristics, with −0.92 and −1.9 dB in the hot state and −0.49 and −0.25 dB in the cold state, respectively. We incorporate both positive and negative phase variants alongside two temperature-independent phase unit cells. The complementary design enables us to utilize two beam operating states, effectively exploiting the otherwise unused cold state. We experimentally demonstrated beamforming at ±5° and ±10° from the broadside. In the case of ±10°, the measured gains at 35 GHz in the cold and hot states were 19.4 and 20.3 dB, respectively, which aligned well with the simulated gains of 20.9 and 21.5 dB. Manipulation of the electromagnetic wave direction with a single excitation has the potential for imaging, sensing, and communication applications. The complementary unit cell design methodology can be further adapted for mmWave beamforming, absorbing, and cloaking reconfigurable EM surfaces. Furthermore, the use of VO2 can be extended up to sub-THz frequencies due to the wideband, low-loss characteristics compared with conventional reconfigurable devices, such as PIN diodes or MEMS switches. [ABSTRACT FROM AUTHOR]

This work reports analysis of the reverse-bias breakdown characteristics of homojunction gallium nitride (GaN) p–i–n (PIN) rectifiers fabricated on bulk GaN substrates. Sub-bandgap photoluminescence mapping at room temperature as a contactless, non-destructive wafer inspection method was performed to analyze the impact of material properties on grown GaN PIN diodes and to study the correlation between defect types and breakdown characteristics of vertical GaN PIN rectifiers. Under the sub-bandgap excitation, yellow luminescence is dominant. The premature breakdown characteristics of the fabricated kV-class vertical GaN PIN rectifiers with nitrogen-implanted floating guard rings are found to be associated with material defects and deep level complexes. Photoluminescence mapping has demonstrated its effectiveness in quantitative analysis of dislocations and other types of defects. [ABSTRACT FROM AUTHOR]

An analytical device physics model is presented for determining the energy conversion efficiency of semiconductor nanowire array-based radial (core–shell) p-i-n junction betavoltaic cells for two- and three-dimensional radioisotope source geometries. Optimum short-circuit current density J sc , open-circuit voltage V oc , fill factor F F , and energy conversion efficiency η are determined for various nanowire properties, including dopant concentration, nanowire length, core diameter, and shell thickness, for Si, GaAs, and GaP material systems. A maximum efficiency of 8.05 % was obtained for GaP nanowires with diameter 200 nm (p-core diameter, i-shell, and n-shell thicknesses of 24, 29.4, and 58.6 nm, respectively), length 10 μ m , acceptor and donor concentrations of 10 19 and 5 × 10 18 cm − 3 , respectively, and a 3D source geometry. [ABSTRACT FROM AUTHOR]

A practical quantitative model is presented to account for the I–V characteristics of pin diodes based on epitaxial Ge-like materials. The model can be used to quantify how the different material properties and recombination mechanisms affect the diode performance. The importance of dislocations, non-passivated defects, and residual intrinsic layer doping in determining the qualitative shape of the I–V curves is discussed in detail. Examples are shown covering literature diodes as well as diodes fabricated with the purpose of validating the theoretical effort. [ABSTRACT FROM AUTHOR]

In this paper, a wideband polarization reconfigurable omnidirectional antenna (PROA) based on a single-substrate active metasurface is proposed. By controlling the states of the PIN diodes, the antenna can selectively radiate an omnidirectional linearly polarized wave and an omnidirectional circularly polarized wave. The reflection coefficient, axial ratio (AR), radiation pattern, and gain of the proposed antenna have been analyzed from the perspective of simulation and measurement. The measured results show that the PROA has a wide overlapped bandwidth from 2.87 to 3.67 GHz (relative bandwidth 24.46%). To the authors' best knowledge, this is the first reported wideband PROA based on a single-substrate reconfigurable polarization converter. This study not only offers a novel approach to design PROAs, but also greatly reduces the design complexity of the feed source compared with the traditional design method of PROAs. [ABSTRACT FROM AUTHOR]

It is a formidable challenge to find the minority carrier recombination lifetime in low-dimensional devices as low-dimensionality increases the surface recombination rate and often reduces the recombination lifetime to a scale of picoseconds. In this work, we demonstrated a simple but powerful method to quantitatively probe the minority carrier recombination lifetime in silicon nanowires or microwires by fitting the experimental photoresponses with our recently established analytical photoresponse principle of photoconductors. The nanowires were passivated with small molecules and Al2O3 to suppress surface recombination, which will increase the minority recombination lifetimes. As expected, the minority carrier recombination lifetime found by this approach increases by orders of magnitude. These wires were also made into PIN diodes, the leakage of which was reduced at least 1 order of magnitude after surface passivation by Al2O3. The minority recombination lifetime found from the leakage current of these devices is largely consistent with what we found from our analytical photoresponse principle. As a further step, we performed scanning photocurrent microscopy to find the minority diffusion length from which we found that the minority recombination lifetime is close to what we found from the analytical photoresponses. In short, this work validated that our analytical response principle is a reliable method to find the minority recombination lifetime in low-dimensional semiconductors. [ABSTRACT FROM AUTHOR]

In this paper, we report a reconfigurable multifunctional polarization converter (RMPC) based on positive-intrinsic-negative (PIN) diodes, enabling to achieve different functions in different bands and states. The simulations and experiments show that when the PIN diode is off, it acts as a broadband linear polarization (LP) converter at 9.12–15.93 GHz. Simultaneously, when the PIN diode is on, the LP incident wave is converted into a left-handed circular polarization wave at 8.69–11.41 GHz and a cross-polarization wave at 13.40–14.97 GHz, whereas full reflection is obtained at 12.05–12.54 GHz. The RMPC consists of two dielectric plates and three layers of metal copper plates. Finally, a sample was fabricated and measured, the simulated and experimental results were in good agreement. Compared with other works, the RMPC has more working states and wider operating frequency bands, which has an application potential in the field of radar stealth and satellite communication. [ABSTRACT FROM AUTHOR]

PIN diodes, due to their simple structure and variable resistance characteristics under high-frequency high-power excitation, are often used in radar front-end as limiters to filter high power microwaves (HPM) to prevent its power from entering the internal circuit and causing damage. This paper carries out theoretical derivation and research on the HPM effects of PIN diodes, and then uses an optimized neural network algorithm to replace traditional physical modeling to calculate and predict two types of HPM limiting indicators of PIN diode limiters. We proposes a neural network model for each of the following two prediction scenarios: in the scenario of time-junction temperature curves under different HPM irradiation, the weighted mean squared error (MSE) between the predicted values from the test dataset and the simulated values is below 0.004. While in predicting PIN limiter's power limitation threshold, insertion loss, and maximum isolation under different HPM irradiation, the MSE of the test set prediction values and simulation values are all less than 0.03. The method proposed in this research, which applies an optimized neural network algorithm to replace traditional physical modeling algorithms for studying the high-power microwave effects of PIN diode limiters, significantly improves the computational and simulation speed, reduces the calculation cost, and provides a new method for studying the high-power microwave effects of PIN diode limiters. [ABSTRACT FROM AUTHOR]

Maintaining acceptable radiation performance over the entire operation bandwidth is a significant challenge in development of a miniaturised reconfigurable antenna. To address this issue, a new Substrate Integrated Waveguide (SIW) based reconfigurable antenna using slow wave structure is presented in this study. The proposed SIW antenna is based on a layered construction with metallic blind vias connecting to ground plane of SIW. The multi-layer structure of SIW with blind vias helps to separate magnetic and electric fields in the SIW cavity. Thus, a slow wave effect is also utilised and it leads to 36% reduction in the antenna size as compared to conventional SIW cavity. To attain the polarisation and frequency reconfiguration, a cross slot is introduced in the top metallic layer of the SIW cavity and four PIN diodes are connected into the cross-slot arms. Experimental results exhibit frequency reconfigurability in different operating regions with resonant frequencies 4.35, 5, 5.8, 6.4, and 9.6 GHz. The polarisation reconfigurability of the proposed antenna is achieved at 5 GHz with LP/RHCP/LHCP. The proposed antenna exhibits 3-dB axial ratio bandwidth of 4.8 to 5.2 GHz with peak gain of 4.2 dBi. [ABSTRACT FROM AUTHOR]

Metasurfaces have shown unparalleled controllability of electromagnetic (EM) waves. However, most of the metasurfaces need external spatial feeding sources, which renders practical implementation quite challenging. Here, a low‐profile programmable metasurface with 0.05λ0 thickness driven by guided waves is proposed to achieve dynamic control of both amplitude and phase simultaneously. The metasurface is fed by a guided wave traveling in a substrate‐integrated waveguide, avoiding external spatial sources and complex power divider networks. By manipulating the state of the p‐i‐n diodes embedded in each meta‐atom, the proposed metasurface enables 1‐bit amplitude switching between radiating and nonradiating states, as well as a 1‐bit phase switching between 0° and 180°. As a proof of concept, two advanced functionalities, namely, low sidelobe‐level beam scanning and Airy beam generation, are experimentally demonstrated with a single platform operating in the far‐ and near‐field respectively. Such complex‐amplitude, programmable, and low‐profile metasurfaces can overcome integration limitations of traditional metasurfaces, and open up new avenues for more accurate and advanced EM wave control within an unprecedented degree of freedom. [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]

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 this paper, an orbital angular momentum (OAM) mode reconfigurable antenna based on a uniform circular array (UCA) is presented. The phase superposition method is presented to overcome the limitation of the number of array units on the mode order in the conventional four‐element UCA antenna, which is limited to generating first‐order OAM beams. The unit phase is introduced by a bifilar helical antenna in this method, and the unit phase is superimposed with the feed phase of the UCA to enable the generation of 3rd‐order OAM beams from the four‐element UCA. At the same time, the DC signal‐controlled feed network assigns three distinct feed phases to the UCA, which realizes the reconfigurability of the three OAM beams. To achieve mode reconfigurability, 20 p‐i‐n diodes were integrated as switches in the feed network for controlling the ON/OFF status of p‐i‐n diodes in the feed network using DC signals. Finally, simulated and measured results show that three OAM beams (lz = −1, −2, and −3) have been generated in the frequency band from 10.6 to 11.8 GHz. [ABSTRACT FROM AUTHOR]

A broadband reconfigurable metasurface consisting of perpendicular metallic gratings and a PIN diode-driven split circular ring for polarization and propagation modes control is demonstrated. The designed metasurface possesses tunable properties in two propagation modes. In the "OFF" state, it can convert incident linear-polarized waves into transmitted cross-polarized waves with full transmission. In the "ON" state, it can reflect incident linear-polarized waves into co-polarized waves with full reflection. Without the increasing number of active elements commonly utilized in chirality-type metasurface polarizers, the equivalent transformation of the split circular ring can be achieved by switching the single PIN diode, and high polarization-conversion efficiency is guaranteed. A metasurface array with 10 × 10 unit cells is fabricated and measured. The experimental results show that the tunable transmission, reflection, and polarization properties of the proposed reconfigurable metasurface can be achieved from 4.9 to 7 GHz. [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]

To improve the threshold voltage and gate reliability of conventional enhancement-mode p-GaN-gated AlGaN/GaN high electron mobility transistors while maintaining a low on-resistance, an improved design solution for p-GaN HEMTs with P-I-N junction gate (PIN-HEMTs) has been proposed. Simulation results show that energy band modulation is achieved by adjusting the doping concentration and thickness of each layer of the PIN junction, and high-performance p-GaN gate HEMTs with adjustable threshold voltages ranging from 0.56 V to 4.75 V and gate breakdown voltages ranging from 19.8 V to 30.3 V would be prepared. The PIN-HEMT has a quasi-self-alignment property, which means that good gate control is independent of gate metal alignment. This not only improves the production efficiency but also solves the problems of weak gate control and electric field aggregation at the gate edge caused by the gate misalignment in conventional p-GaN gate HEMTs, thus realizing lower on-resistance and higher gate breakdown voltage, which demonstrates this proposed structure has excellent potentials for realizing effective and reliable high-power transistors. [ABSTRACT FROM AUTHOR]

The Zener–Klein (ZK) interband tunneling in graphene layers (GLs) with the lateral n-i-n and p-i-n junctions results in the specific characteristics that can be used for the rectification, detection, amplification, and generation of the terahertz (THz) signals. The transit-time delay of the tunneling electrons and holes in the depletion regions leads to the phase shift between the THz current and THz voltage causing the negative dynamic conductance in a certain frequency range and resulting in the so-called transit-time (TT) instability. The combination of the ZK tunneling and the TT negative dynamic conductance enables resonant THz the amplification and generation of THz radiation. We propose the THz devices based on periodic cascade GL p-i-n structures exhibiting the TT resonances and evaluate their potential performance. Such structures can serve as THz amplifiers and, being placed in a Fabry–Pérot cavity, or coupled to a THz antenna or using a ring oscillator connection, as THz radiation sources. [ABSTRACT FROM AUTHOR]

GaN devices play a major role in modern electronics, providing high-power handling, efficient high-frequency operation, and resilience in harsh environments. However, electric field crowding at the edge of the anode often limits its full potential, leading to single-event effects (SEEs) at lower bias voltages under heavy ion radiation. Here, we report on the performance of homojunction GaN vertical PiN diodes with a hybrid edge termination design under heavy ion irradiation, specifically, oxygen ions, chlorine ions, Cf-252 fission fragments, and alpha particles from an Am-241 source. The unique hybrid edge termination (HET) design provides better electric field management, preventing breakdown from occurring at the edge of the anode at lower voltages. The results of this study reveal that these devices exhibit excellent tolerance to 12-MeV oxygen and 16-MeV chlorine ions, owing to their low linear energy transfer (LET) and range in GaN. However, single-event burnout (SEB) is observed during the Cf-252 exposure at about 50% of the diodes' electrical breakdown voltage due to the presence of higher LET and longer-range ions. Optical and scanning electron microscopy (SEM) reveal that the damage that caused by SEB lies close to the center of these devices rather than the anode edge. Devices with junction termination extension (JTE) instead of HET edge termination also show similar SEB when irradiated with Cf-252 fission fragments. Physical damage due to SEB occurs at the edge of the anode for these devices. These comparative results show the benefits of HET for enhancing the resistance of GaN-based PiN diodes to heavy ion irradiation. [ABSTRACT FROM AUTHOR]

Summary: This article introduces a novel and groundbreaking approach combining multiple‐input‐multiple‐output (MIMO) technology with radio frequency (RF) energy harvesting. The proposed antenna consists of two semi‐circular monopole antenna components, optimized with dimensions of 89 × 51.02 × 1.6 mm3, that share a common ground plane to achieve MIMO characteristics. A series of split‐ring resonators on the ground plane significantly enhances the isolation between the two radiating components. Band‐notched features are performed in the 3.5 GHz WiMAX and 5.5 GHz WLAN bands through modified C‐shaped slots in the radiating patch and two rectangular split‐ring resonators serving as parasitic devices near the feed line. The reconfiguration of band‐notching is made possible by controlling the modes of the embedded PIN diodes. The two antenna elements maintain mutual coupling below −18 dB from 1.5–13 GHz, achieving an impressive 158.62% impedance bandwidth. The antenna's efficiency and gain experience significant drop, indicating effective interference suppression at the center frequencies of the notch bands, and its performance in MIMO systems is assessed through parameters including envelope correlation coefficient, port isolation, radiation patterns, efficiency, gain, and diversity gain. The simulated properties of the designed antenna closely align with the measured outcomes, demonstrating its reliability and consistency. Moreover, the article evaluates the antenna's potential for RF energy harvesting, achieving a maximum harvested energy of 4.88 V. This proposed antenna can be used in multiple applications, like wideband, band‐notching MIMO, and RF energy harvesting. This proposed antenna is an efficient, reconfigurable wideband MIMO antenna with novel RF energy harvesting capability. [ABSTRACT FROM AUTHOR]

This letter constitutes a novel triple-band reconfigurable filtering antenna used for Bluetooth, WiMAX and WLAN applications. First, a compact triple-band reconfigurable filter is instigated which is composed of two pairs of Stepped Impedance Resonators (SIRs) and a pair of Uniform Impedance Resonators (UIRs). The SIRs are entrenched at the upper and lower half of feed lines operating at 2.4 and 5.4 GHz, respectively. A pair of UIRs operating at 3.5 GHz is folded and enclosed near the upper SIR. A shunt stub is tapped at the source-load feeding lines to upgrade the selectivity of the filter. The proposed filter uses four PIN diodes to initiate different reconfigurable multiband operations. A fractal antenna is implemented with a modified binary tree topology. The ground plane of the proposed antenna is reformed with a stub. The improved antenna structure enables three radiating bands with enhanced performance. Later, the designed filter is integrated into the antenna to implement the intended triple-band reconfigurable filtering antenna. [ABSTRACT FROM AUTHOR]

In recent years, reconfigurable intelligent metasurface (RIS) has gained much attention due to its flexibility in modulating the phase, amplitude, and polarization of electromagnetic waves. It is widely used for wireless power and information transmission. However, RIS requires an external wired power supply or batteries to activate their modulation capabilities, as they do not generate the required energy themselves. This paper presents a self‐powered RIS that does not require an external wired power supply or batteries. The modulation capability is activated by harvesting radio frequency (RF) energy. The self‐powered RIS consists of an energy‐metatom, which is loaded with a PIN diode for flexible phase modulation. The inclusion of an absorber/energy port on the energy‐metatom allows for independent RF energy harvesting. The RIS consisting of energy‐metatoms can cut out all wired power supplies and batteries so that it can dynamically regulate electromagnetic waves by self‐powered means. As a proof‐of‐concept, a prototype composed of 10 × 10 energy‐metatoms is fabricated. The measured results are in good agreement with the simulated. This self‐powered RIS can be used as an "infinite‐lifetime" power supply for dynamic electromagnetic modulation in the RIS. [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, a novel frequency reconfigurable antenna for Wi-Fi and WiMAX applications is proposed. The antenna uses PIN diodes for frequency reconfigurability, allowing it to seamlessly switch between two distinct frequency bands centred around the resonant frequencies of 4.1 GHz in the ON state and 5.2 GHz in the OFF state. The input reflection coefficient obtained from the designed antenna is below −10 dB. The measured and simulated gain of the antenna is 4 dBi and 2.65 dBi at resonating frequencies 4.1 GHz and 5.2 GHz the measured and simulated gain is 3.2 dBi and 2.93 dBi, respectively. The radiation pattern exhibits the same for both states. Optimization of the antenna’s dimensional parameters is done with the help of CST simulation software and the electrical parameter such as input reflection coefficient is measured using a Vector Network Analyzer to validate the prototype. The proposed antenna is fabricated on FR-4 substrate material with a thickness of 1.6 mm and a relative permittivity of 4.4. The proposed antenna’s size is 30 × 30 × 1.6 mm3 which is compact and suitable for smartwatch applications. The proposed antenna is compact and remains a good candidate for integration with the smartwatch. [ABSTRACT FROM AUTHOR]

In this paper, a wideband 1-bit reconfigurable transmit array antenna (RTA) is proposed. The 1-bit RTA element consists of a passive receiving antenna and a reconfigurable radiating antenna, which adopt a proximity-coupled feed method to broaden the transmission bandwidth. Two p-i-n diodes are integrated into the reconfigurable receiving antenna to control the current distribution. By switching the states of the p-i-n diodes, the reconfigurable radiating antenna can achieve a 1-bit phase shift. Element simulation results show that the proposed RTA element can achieve a 3 dB transmission bandwidth of 21.5%. A 100-element RTA prototype with 200 p-in diodes is designed, fabricated and measured. The measured results show that the peak gain is 18.8 dBi at 5.05 GHz, corresponding to an aperture efficiency of 20.8%, and the 3 dB gain bandwidth is 17.1%. Furthermore, the scanned beams can reach −32° and −36°, respectively, in the E- and H-planes. [ABSTRACT FROM AUTHOR]

This paper presents a novel method for identifying and tracking PocketQube satellites: the MRC-100 satellite is a model, and this method is based on a resonant radar reflector. The resonant reflector’s basic concept is that the resonant reflector uses a VHF/UHF communication subsystem antenna; there is no radiated RF signal, which means the power consumption is only some Milliampere (mA). The continuous wave (CW) illuminator RF source is on the ground, and the onboard antenna receives the CW RF signal from the Earth. The microcontroller (uC) periodically switches PIN diode forming BPSK modulated signal reflection so that another Earth station can receive the backscattered Binary Phase Shift Keying (BPSK) modulated signal. Also, it can detect the satellite if the ground station receiver can use a matched filter like a correlation receiver. If the ground station receiver knows the BPSK code of the satellite, it can detect it. If not, there is no way to detect the satellite. This method is similar to Radio Frequency Identification (RFID) applications, but the reader is the ground station, and the tag is the satellite. [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]

In this letter, a novel design of electrically tunable substrate integrated waveguide (SIW) equalizer, based on PIN diodes, is proposed. Compared to previous SIW equalizers, this one introduces PIN diodes that exhibit varying impedance under different direct current (DC) voltages. The equalizing values of the SIW equalizer are directly linked to the DC voltage applied to the PIN diode within a specific voltage range. This feature allows it to be considered as an electrically tunable SIW equalizer. The experimental results demonstrate that the equalizing values are consistently monotonic and adjustable within the range of 1.59–7.56 dB in Ku‐band. This adjustment is attained through a DC voltage step of −0.01 V, applied within the range of 1.23–1.11 V. Additionally, the microwave equalizer is a planar structure that can be conveniently implemented on traditional printed circuit board, resulting in lower costs, easier realization, and integration. This SIW equalizer can be applied in amplitude compensation circuits and networks to compensate flatness dynamically. [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]

We propose a miniaturized frequency-reconfigurable multiband antenna with bandwidth enhancement. The main radiating patch is shorted from one edge to reduce the antenna footprint. An inverted U-shape microstrip line is integrated onto the antenna structure to excite more resonant frequencies. Indeed, by shorting the U-shape's arms, seven frequency bands can be created and controlled. The activation of the two p-i-n diodes is ensured by employing a simple symmetrical DC bias network. Furthermore, by adjusting the arms' lengths, two resonances are combined to enhance the working bandwidth. Measurements reveal that the antenna resonates around the operating frequencies of 2.91 GHz, 3.55 GHz, 3.69 GHz, 3.83 GHz, 4.14 GHz, 4.18, and 4.24 GHz. The antenna exhibits stable patterns, with a measured peak gain and efficiency of 5.5 dBi and 86%, respectively. The antenna is compact; thus, it is recommended in wireless systems requiring multiband function with stable patterns and a reduced area. [ABSTRACT FROM AUTHOR]

Due to its ability to adapt to a variety of electromagnetic (EM) environments, the sensing‐enabled metasurface has garnered significant attention. However, large‐scale EM‐field sensing to obtain more information is still very challenging. Here, an adaptive information metasurface is proposed to enable intelligent sensing and wave manipulating simultaneously or more specifically, to realize intelligent target localization and beam tracking adaptively. The metasurface is composed of an array of meta‐atoms, and each is loaded with two PIN diodes and a sensing‐channel structure, for polarization‐insensitive and programmable beamforming and sensing. By controlling the state of the PIN diode, the proposed meta‐atom has 1‐bit phase response in the designed frequency band, while the sensing loss keeps higher than ‐10 dB for both "ON" and "OFF" states. Hence there is nearly no interaction between the beamforming and sensing modes. Experiments are conducted to show multiple functions of the metasurface, including intelligent target sensing and self‐adaptive beamforming, and the measured results are in good agreement with the numerical simulations and theoretical calculations. [ABSTRACT FROM AUTHOR]

Reconfigurable metasurfaces have shown unprecedented capabilities in controlling electromagnetic (EM) waves in recent years and play an essential role in information manipulation. However, most research on reconfigurable metasurfaces is limited to planar rigid structures, with only one control function and suitable for specific single polarization. Achieving simultaneous control of phase, polarization, and frequency in the conformal structure has significant practical implications in many applications, but remains obviously challenging. In this paper, a flexible multifunctional time‐varying phase‐modulated metasurface (MTPM) with orthogonal polarization control is proposed for conformal applications to manipulate the spectrum distribution. It enables time encoding capability in controlling the phase characteristics of x‐ and y‐polarized EM waves individually by switching the bias voltage of the PIN diode in two directions. Discrete harmonic spectrum and continuous Doppler frequency shifts are implemented separately on two orthogonal polarizations by applying different time coding sequences. As a practical application, a conformal MTPM for radar feature transformation is explored. Multiple discrete false targets and defocusing phenomena can be realized respectively for x‐ and y‐polarized waves. Both simulated and measured results verify the validity of the proposed method and prototype. [ABSTRACT FROM AUTHOR]

P-i-N and Schottky P-i-N diamond diodes are a promising technology for high-power limiters. Receivers, solid-state amplifiers, and detectors commonly use P-i-N and/or Schottky diodes for protection from high power incident signals. Here, we report on the RF power handling and power dissipation capability of diamond P-i-N and Schottky P-i-N diodes. We fabricate P-i-N diodes as vertical structures, with both majority and minority carriers involved in charge transport. Similarly, we fabricate vertical Schottky P-i-N diodes, with the doping in the n-layer reduced compared to P-i-N diodes such that the n-layer becomes fully depleted during operation, resulting in a majority-carrier device with a fast recovery time. Both P-i-N and Schottky P-i-N diodes were packaged in shunt-configuration and matched for 3 GHz operation, with a small signal insertion loss of ∼1.25 dB. P-i-N diodes operated up to 40 dBm before failing nondestructively at 45 dBm, demonstrating power dissipation handling that exceeds that of commercially available Si P-i-N diodes by more than a factor of five. Schottky P-i-N diodes operated up to 49 dBm before non-recoverable failure at 50 dBm. [ABSTRACT FROM AUTHOR]

With the rapid development of information and communication technology, intelligent wireless systems have a huge demand for devices with multi‐function integration and multi‐degree of freedom electromagnetic control. In this paper, a multifunctional folded transmitarray antenna (MFTA) using a reconfigurable metasurface is proposed to achieve simultaneous and independent modulation of beam and polarization. The beam scanning, arbitrary wave generator, and polarization conversion functions can be achieved only by adjusting the PIN diode bias on the reconfigurable metasurface. In order to prove the feasibility of the proposed method, a prototype is fabricated and verified by experiments. Both simulated and measured results verify the excellent performance of the MFTA. This work opens a door to multi‐functional integration and multi‐degree of freedom electromagnetic manipulate devices, which have great prospects in areas such as radar detection and wireless communication. [ABSTRACT FROM AUTHOR]

This paper outlines the design and validation of a four-port compact Multi-Input Multi-Output (MIMO) antenna engineered to provide reconfigurable band notches within the ultra-wideband spectrum. The antenna features a circular monopole engraved with split ring slots along its radiating section, while a U-shaped slot is etched onto the feed line to facilitate band notches at specific frequencies—4.3 GHz (corresponding to INSAT), 6.8 GHz (aligned with Wi-Fi-6E), and 8.3 GHz (pertaining to X-band satellite). To ensure proper isolation, the MIMO elements are arranged orthogonally, and a decoupling periodic structure is strategically interposed between these elements to enhance isolation further. The incorporation of a PIN diode within the U-shaped slot introduces reconfigurability into the band notching mechanism. The MIMO antenna operates in two distinct modes depending upon the state of the PIN diode, either activated (ON) or deactivated (OFF). In the former mode, the antenna offers switchable band notches across three frequencies, while in the latter mode, it offers band notches at two specific frequencies. The validity of the antenna's performance is validated through real-time fabrication and measurement. Both simulated and measured results exhibit a notable correlation. The antenna stands as an appropriate candidate for future cognitive radio applications. [ABSTRACT FROM AUTHOR]

Active metasurfaces with dynamically reconfigurable functionalities are highly demanded in various practical applications. Here, we propose a wideband low-scattering metasurface that can realize an in-band reconfigurable transparent window by altering the operation states of the PIN diodes loaded on the structures. The metasurface is composed of a band-pass frequency selective surface (FSS) sandwiched between two polarization conversion metasurfaces (PCMs). PIN diodes are integrated into the FSS to switch the transparent window, while a checkerboard configuration is applied in PCMs for the diffusive-reflective function. A sample with 20×20 elements is designed, fabricated, and experimentally verified. Both simulated and measured results show that the in-band functions can be dynamically switched between beam-splitting scattering and high transmission by controlling the biasing states of the diodes, while low backscattering can be attained outside the passband. Furthermore, the resonant structures of FSS also play the role of feeding lines, thus significantly eliminating extra interference compared with conventional feeding networks. We envision that the proposed metasurface may provide new possibilities for the development of an intelligent stealth platform and its antenna applications. [ABSTRACT FROM AUTHOR]

Summary: In this communication, an asymmetric co‐planar waveguide (ACPW)–fed composite right–left‐handed transmission line (CRLH‐TL)–based frequency band and polarization reconfigurable antenna (RA) is presented. The reconfigurability is achieved by using a PIN diode. When the diode is in OFF state, meander line works as part of ground. Hence, the antenna is like a circular patch antenna working at 5.15 GHz. In the ON state, the antenna works as a CRLH‐TL‐based antenna with an additional lower band resonating at 2.45 GHz. The antenna also has circular polarization (CP) property. The lower 2.4 GHz band is covering for IEEE 802.11 b/g/n/ax/be applications, whereas the higher band is covering the WiFi bands of IEEE 802.11a/h/n/ac/ax/be applications with CP radiation (upper band). This antenna is effective in a scattering environment such as in urban areas and indoor communication. [ABSTRACT FROM AUTHOR]

This paper presents the design of multiband frequency reconfigurable patch antenna with switchable radiation pattern and polarization states. The antenna design is based on a circular patch radiator with a pair of metallic strips placed on diametrically opposite sides of it. Circular polarization (CP) from the antenna is excited by etching a pair of slots with a coaxial feed. When the diodes are OFF, the antenna resonates at 4.2, 6.6 GHz, (C band) and 8.07 GHz (X band) and the main beam is located at 0⁰ with CP at X band. The resonance at 4.2 and 8.5 GHz are observed when one of the diode is ON. The main beam at X band is being shifted from −30⁰ to 0⁰ and +30⁰ in the elevation plane during the change in operating modes. Peak gain of the antenna is 6 dBi in all the operating modes. [ABSTRACT FROM AUTHOR]

A Fabry-Pérot (FP) antenna with wideband dual-polarization and radar cross section- (RCS-) reconfigurability adopting water-based frequency selective surface (FSS) is presented. The feed antenna is designed to switch between horizontal polarization (HP) and vertical polarization (VP) by controlling the on/off states of two PIN diodes. By optimizing the height of the FP resonant cavity, the proposed FP antenna achieves wideband and high-gain properties. In addition, the incident wave can be absorbed when the polymethyl methacrylate (PMMA) container is filled with water, which reduces the monostatic RCS. This design can be selected to be in stealth mode or radiation mode by injecting water into or extracting water from the water container. The measured results indicate that in stealth mode, the 10-dB RCS reduction band is from 4.5 GHz to 6.4 GHz, and the peak RCS reduction is 31.5 dB at 5.2 GHz. In the radiation mode, the realized gains of the FP antenna in both HP and VP at 5.2 GHz reach 16.6 dBi. Simulated and measured results verify the realizability and operational concept of the designed FP antenna. [ABSTRACT FROM AUTHOR]

In quantum dots (QDs), the Auger recombination is a non-radiative scattering process in which the optical transition energy of a charged exciton (trion) is transferred to an additional electron leaving the dot. Electron tunneling from a reservoir is the competing process that replenishes the QD with an electron again. Here, we study the dependence of the tunneling and Auger recombination rate on the applied electric field using high-resolution time-resolved resonance fluorescence (RF) measurements. With the given p–i–n diode structure and a tunnel barrier between the electron reservoir and the QD of 45 nm, we measured a tunneling rate into the QD in the order of ms−1. This rate shows a strong decrease by almost an order of magnitude for decreasing electric field, while the Auger emission rate decreases by a factor of five in the same voltage range. Furthermore, we study in detail the influence of the Auger recombination and the tunneling rate from the charge reservoir into the QD on the intensity and linewidth of the trion transition. In addition to the well-known quenching of the trion transition, we observe in our time-resolved RF measurements a strong influence of the tunneling rate on the observed linewidth. The steady-state RF measurement yields a broadened trion transition of about 1.5 GHz for an Auger emission rate of the same order as the electron tunneling rate. In a non-equilibrium measurement, the Auger recombination can be suppressed, and a more than four times smaller linewidth of 340 MHz (1.4 μeV) is measured. [ABSTRACT FROM AUTHOR]

A 1-bit phase reconfigurable fixed-frequency beam steering leaky-wave antenna (FBSLWA) with wide-angle steering is proposed in this paper. By controlling two p–i–n diodes on the branches of the element, a stable 180° phase difference is realized. Moreover, the open stop-band effect at the broadside radiation is suppressed by reducing the reflection coefficients of the element. The proposed FBSLWA can achieve wide-angle steering within a frequency bandwidth of 10.4 GHz–11.8 GHz. As for the measured results, they show that the achievable beam steering ranges of the FBSLWA at 10.4 GHz, 11.0 GHz, and 11.8 GHz are −61° to +59°, −64° to +71°, and −62° to +58° respectively, with measured peak gains of 12.1 dBi, 13.9 dBi, and 11.7 dBi. [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]

Purpose: In wireless communication system, use of multiple antennas for different requirements of system will increase the system complexity. However, reconfigurable antenna is maximizing the connectivity to cover different wireless services that operate different frequency range. Pattern reconfigurable antenna can improve security, avoid noise and save energy. Due to their compactness and better performance at different applications, reconfigurable antennas are very popular among the researchers. The purpose of this work, is to propose a novel design of S-shaped antenna with frequency and pattern diversity. The pattern and frequency reconfiguration are controlled via ON/OFF states of the PIN diode. Design/methodology/approach: The geometrical structure of the proposed antenna dimension is 18 × 18 × 0.787 mm3 with εr = 2.2 dielectric constant. Three S-shaped patches are connected to a ring patch through PIN diodes. The approximate circumference of ring patch is 18.84 mm and length of patch is 5 mm, so approximate length of radiating patch is 14.42 mm and effective dielectric constant is 1.93. Conductor backed coplanar waveguide (CPW) is used for feeding. The proposed antenna is designed and simulated on CST microwave studio and fabricated using photolithography process. Measurements have been done in anechoic chamber. Findings: Antenna shows the dual band operation at 2.1 and 3.4 GHz frequency. The first band remains constant at 2.1 GHz resonant frequency and 200–400 MHz impedance bandwidth. Second band is switched at seven different resonant frequencies as 3.14, 3.45, 3.46, 3.68, 3.69, 3.83 and 3.86 GHz with switching of the diodes. The −10 dB bandwidth is more than 1.4 GHz. Research limitations/implications: Pattern reconfigurability can be achieved using mechanical movement of antenna easily but it is not a reliable approach for planar antennas. Electronic switching method is used in proposed antenna. Antenna size is very small so fabrication is very crucial task. Measured results are deviated from simulation results due to fabrication error and effect of leads of diodes, connecting wires and battery. Practical implications: The reconfiguration of the proposed antenna is controlled via ON/OFF states of the three PIN diodes. The lower band of 2.1 GHz is fixed, while second band is switched at five different resonant frequencies as 3.27, 3.41, 3.45, 3.55 and 3.88 GHz, with switching of the PIN diodes with all state of diodes and exhibit pattern reconfigurability at 2.1 GHz frequency. At second band center frequency is significantly changed with state of diodes and at 3.4 GHz pattern is also changed with state of diodes, hence antenna exhibits frequency and pattern reconfigurability. Originality/value: A novel design of pattern and frequency reconfigurable antenna is proposed. Here, work is divided into two parts: first is frequency reconfiguration and second is radiation pattern reconfiguration. PIN diodes as switch are used to select the frequency band and reconfigure the radiation pattern. This proposed antenna design is novel dual band frequency and pattern reconfigurable antenna. It resonates at two distinct frequencies, i.e. 2.1 and 3.4 GHz, and has a pattern tilt from 0° to 355°. The conductor backed CPW feed technique is used for impedance matching. [ABSTRACT FROM AUTHOR]

A single‐sheet structure‐based switchable broadband FSR/absorber is proposed. The lossy layers I, II, and the FSS are printed along the direction of electromagnetic (EM) wave propagation (z‐direction) at the top, middle, and bottom positions of the substrate, respectively. A PIN diode is used in the lossy layer II and the FSS to switch their operating states. By activating or deactivating the PIN diodes, the design can operate as either an FSR or absorber. The FSR achieves a passband with an insertion loss of 0.64 dB at 3.9 GHz, and two absorption bands with fractional bandwidth of 87.6% and 20.8%, respectively. The absorber has a wide absorption band from 1.6 to 5.4 GHz (109%). It is transparent to EM waves of orthogonal polarization. The measured and simulated results are in close agreement, which exhibits stable performance under 30° of oblique incidence in both the xz‐ and yz‐planes. [ABSTRACT FROM AUTHOR]

In this letter, a composite energy selective surface (CESS) using diode to induce VO2 is proposed. The CESS is composed of periodic metal meshes connected with PIN diodes and VO2 in rows and the CESS is embedded in a metal window. VO2 can be induced by using the properties of uneven distribution of induced electric field on the CESS and the conduction field of diode is smaller than that of VO2, so as to reduce the metal‐insulator transition field of it. When the shielding efficiency (SE) reaches 10 dB, the incident field of CESS would be reduced by 72.95% compared with the ESS using VO2 (V‐ESS). Meanwhile, compared with the ESS using diode (D‐ESS), the number of diode in CESS is reduced by 92%, greatly reducing the manufacturing cost. Furthermore, the design of CESS with different incident field when SE reaches 10 dB can be realized more flexibly according to different structures, while the maximum SE can reach 20.94 dB. [ABSTRACT FROM AUTHOR]

This work intends to investigate the impact of silicon layer thickness and substrate biasing on the UV photodetection efficiency of PIN diodes fabricated with ultra-thin body and buried oxide (UTBB silicon-oninsulator [SOI]) technology, aiming to verify their behaviour on an ultimate commercial technology. UV photodetectors are applied in different fields, such as environmental and biomedical ones, and their implementation in UTBB SOI could enable the design of mixed circuits where data acquisition and processing could be made in the same chip, enhancing systems' performance. It is shown that a 20-nm-thick silicon layer can be applied for UV photodetection and enhanced generated current is obtained when substrate bias is set to guarantee a depletion regime in the entire active layer. [ABSTRACT FROM AUTHOR]

Microstructured neutron detectors have the benefit of enhanced neutron detection efficiency as compared to planar devices, achieved by etching 6LiF-filled trenches on the top surface of a silicon PIN diode. This sensor geometry results in a complex electric field distribution and depletion characteristics within the diode under reverse bias. For the first time on record, the effects of a fixed oxide charge on the microstructured device depletion characteristics and mobile carrier transport is investigated. Prototype detectors were fabricated with non-conformal surface doping. Capacitance voltage and current voltage measurements were performed for these prototypes and compared with COMSOL Multiphysics simulations. A spectral response from an 241Am alpha particle source was acquired and analyzed. It was found that monoenergetic alpha particles produce three prominent peaks in the pulse height spectrum output by the device. The peaks were confirmed by simulations to correlate with dead layers and incident trajectories into the microstructure. It was also found that significant differences in pulse rise time result, corresponding with events arriving in a low-field region in the fins and a high-field region in the bulk. Geant4 was utilized for radiation transport, interaction modeling, and benchmarking the spectral data. The results of this simulation work provide confidence in the ability to attain and benchmark electrical characteristics and spectral data for semiconductor radiation detectors employing complex microstructures. [ABSTRACT FROM AUTHOR]

The study of the electroluminescence of silicon vacancy color centers (SiV centers) in the diamond p-i-n diode at high current density of 500 A/cm2 is presented. To create color centers, the internal region of the diode was doped with silicon. In the electroluminescence spectrum, the bright emission line at 738 nm corresponding to the SiV color center in a negative charge state was observed. Such bright emission is due to high current density. Additionally, the 946 nm line corresponding to the emission of the color center in a neutral charge state was observed in electroluminescence. Nanosecond voltage pulses were applied to study electroluminescence in a pulsed regime. Short emission pulses at 738 nm were demonstrated, showing the potential of creating electrically driven single photon source with "photon on demand" capability. By comparing the intensities of photoluminescence and electroluminescence, the possibility of obtaining single photon emission rate in a diode exceeding 106 photon/s is shown. [ABSTRACT FROM AUTHOR]

A singly fed reconfigurable circular loop antenna is proposed for millimeter-wave (mmWave) communication systems. This antenna's distinctive feature lies in its capacity to adjust both polarization and bandwidth characteristics, a capability made possible by the strategic integration of two PIN diodes. These diodes are engineered to function in various modes, allowing for three distinct polarization states and accommodating two distinct bandwidths. A meticulous alignment of these PIN diodes enables the utilization of a single DC bias network as a highly effective RF choke, which simplifies the design and reduces the associated losses. Additionally, a planar biasing network that consists of coplanar strip-lines (CPS) has been employed eliminating the need for lumped elements. The simple and totally planar configuration offers a choice of right-hand circularly polarized (RHCP) radiation or left-hand circularly polarized (LHCP) radiation at 28 GHz. This is accompanied by impedance matching and axial ratio (AR) bandwidths of 12.9% and 8%, respectively, over the same frequency range with a gain of 7.5 dBic. Moreover, when the PIN diodes are unbiased, the antenna offers linear polarization (LP) over two narrow bandwidths at 27 GHz and 29 GHz featuring a maximum gain of 7.2 dBic. Therefore, the proposed configuration offers three operating modes: wide-band RHCP, wide-band-LHCP, and LP over dual narrow bands. Significantly, simulated results closely align with the measured outcomes, affirming the robustness and accuracy of this design. [ABSTRACT FROM AUTHOR]

This paper discusses the design and performance of a frequency reconfigurable antenna for Internet of Things (IoT) applications. The antenna is designed to operate on multiple frequency bands and be reconfigurable to adjust to different communication standards and environmental conditions. The antenna design consists of monopole with one PIN diode and 50Ω feed line. By changing the states of the diode, the antenna can be reconfigured to operate in a dual-band mode and a wideband mode. The performance of the antenna was evaluated through simulation. The antenna demonstrated good impedance matching, acceptable gain, and stable radiation patterns across the different frequency bands. The antenna has compact dimensions of (26×19×1.6) mm³. It covers the frequency range 2.95 GHz -8.2 GHz, while the coverage of the dual- band mode is (2.7-3.8) GHz and (4.57-7.4) GHz. The peak gain is 1.57 dBi for the wideband mode with omnidirectional radiation pattern. On the other hand, the peak gain of the dual-band mode is 0.87 dBi at 3 GHz and 0.47 dBi at 6 GHz with an omnidirectional radiation pattern too. [ABSTRACT FROM AUTHOR]

Metasurface has been applied as one critical platform for electromagnetic modulation devices. Here, a programmable metasurface loaded with positive-intrinsic negative (PIN) diodes is proposed to realize dynamic switching of arbitrary multi-beam. Furthermore, the multi-beam coding sequence is optimized by a genetic algorithm (GA) to achieve dual- to nine-beam with different scattering directions. As a proof of concept, a programmable metasurface prototype that operates around 8 GHz is designed and fabricated to be tested in far-field measurements. The beam splitter has been verified by theoretical analysis and numerical simulation to have a power efficiency of over 70%. In the measurement system, multi-beam splitting phenomena are obtained using DC control of the PIN diodes "on" and "off", which is consistent with the simulation results. The proposed beam splitter can be designed with real-time multi-beam switching and intelligently provides coding sequences with multiple directive angles, thus providing potential benefits for next-generation antennas. [ABSTRACT FROM AUTHOR]