Single Band Modulation Research Articles

Novel Design of a Bandwidth Enhanced and Frequency Reconfigurable, Wearable Antenna for Body Centric Communication

This paper proposes a novel design for a frequency reconfigurable and bandwidth-enhanced antenna for use in biomedical telemetry applications. Data pertaining to a patient’s body parameters, such as blood pressure, pulse, and temperature, are gathered using sensors and then transmitted to a remote place for monitoring. The proposed antenna is connected to a wearable transmitter, which transfers the body parameter data to a centrally located nearby control unit. The antenna operates in the 5.8 GHz band in single-band mode and in the 4.27 GHz (C band) and 5.8 GHz industrial, scientific, and medical (ISM) bands in dual-band mode. The use of ethylene-vinyl acetate foam as a substrate makes the structure waterproof and ultraviolet resistant. The basic antenna structure equipped with proximity coupling offers a front-to-back ratio (FBR) of 17.62 dB and a bandwidth of 122 MHz. With an additional upper patch and resonant slots, bandwidth enhancement of 82.85% and 11.57% improvement in the FBR are achieved, respectively. Overall, a maximum FBR of 19.66 dB and gain of 5.0 dBi are attained over the resonant frequency. The specific absorption rate is found to be 0.145 W/kg for 10 gram of tissue.

Dual-band higher-order topological states and four-wave mixing in plasmonic valley-Hall metasurfaces

Higher-order topological states in plasmonic metasurfaces are of great importance in practice for their tight confinements and high field enhancements, providing many promising nonlinear applications such as robust quantum light source through four-wave mixing (FWM). However, previous works are limited to single-band modes and FWM processes based on second-order topological corner states have still not been revealed. In this work, we propose a plasmonic valley-Hall topological metasurface, which is modelled based on coupled dipole approximation with dyadic Green's functions containing retarded long-range interaction terms. Simultaneous lifting of Dirac degeneracies in two bandgaps due to inversion-symmetry breaking results in dual-band second-order topological states, which are robust against structural disorder. We present a theoretical approach for considering the nonlinear interaction in dipole arrays and numerically show nonlinear generation of corner mode at signal frequency via the FWM process by pumping with edge modes. The results presented in this work will pave a broad way towards the wide applications of topological plasmonic metasurfaces.

On measurements of spurious components of heterodyne signal in radiometric receivers

With a heterodyne frequency conversion, a significant contribution to the intrinsic noise of the radiometric receiver is made by a heterodyne. The spectral components generated by the heterodyne will be present in the processed signal at the output of the radiometric receiver and may manifest themselves when analyzing the received signal in spectral lines when high frequency resolution is required for processing. The purpose of the work is to analyze various types of modulation of the heterodyne signal, including modulation with an arbitrary phase shift between the components in the lower and upper side bands of the heterodyne signal. In this article, the methods of frequency transfer used in determining the spectral composition of the signal received by a radiometric receiver are considered. For heterodyne frequency conversion, in addition to the classical types of parasitic modulation of the heterodyne signal described in the literature – amplitude, phase (frequency) and single-band modulation, modulation with an arbitrary phase shift between the components in the lower and upper side bands of the heterodyne signal is considered. It is shown that with a small deviation of the frequencies of the modulating signal, ambiguity is possible in determining the level of components when using signal analyzers to measure the characteristics of heterodynes of radiometric receivers. The results of the analysis performed in the article can be used in the design of heterodynes with multiple output frequencies, taking into account the spectral comtent of the synthesized signal. The study was carried out at the expense of the grant of the Russian Science Foundation No. 22-19-00063 dated 13.05.2022. https://rscf.ru/project/22-19-00063.

An OOK and Binary FSK Reconfigurable Dual-Band Noncoherent IR-UWB Receiver Supporting Ternary Signaling

This article presents a multiband low-power and low-complexity impulse radio ultrawideband (IR-UWB) noncoherent receiver. The proposed receiver can be digitally reconfigured in three different modes of operation, including two single-band modes and one concurrent dual-band mode. In the two single-band modes, the proposed envelope detection architecture is capable of receiving and demodulating an on–off keying (OOK) pulse stream at RF center frequencies of 2.8 or 4.8 GHz. In the concurrent dual-band mode, the proposed architecture is able to demodulate binary frequency-shift keying (FSK), in addition to OOK demodulation, at center frequencies of 3 and 5 GHz. The receiver is composed of a reconfigurable low-power differential low noise amplifier (LNA), a fully differential squarer (self-mixer circuit), low-pass filter (LPF), and variable gain baseband (BB) amplifiers. The receiver is fabricated in TSMC 130-nm CMOS process technology. The receiver can operate at up to 150 Mb/s with the ternary signaling that is enabled by the binary FSK modulation combined with the OOK modulation in concurrent dual-band mode. At its maximum gain, the receiver achieves a sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 72 dBm at a bit error rate (BER) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-3}$</tex-math> </inline-formula> at a 100-Mb/s data rate. It consumes 11.9 and 13.2 mW from a 1.2-V supply in the single-band modes and concurrent dual-band mode, respectively.

Octa-band reconfigurable monopole antenna frequency diversity 5G wireless

&lt;span lang="EN-US"&gt;An octa-band frequency-reconfigurable antenna (28×14×1.5 mm&lt;sup&gt;3&lt;/sup&gt;) with a broad tuning range is shown. Antenna mode1 (4.31 GHz) works in one single-band mode and two dual-band in modes 2 and 3 (i.e., 3.91 and 5.9 GHz) as well as one tri-band in mode 4 (i.e., 3.09, 5.65, and 7.92 GHz) based on the switching situation of the antenna. Changing capacitance for frequency reconfigurability is accomplished with the use of lumped components. The antenna’s observed tuning spans from 3.09 GHz to 7.92 GHz. for all the resonant bands, the suggested antenna has a voltage standing waves ratio (VSWR)&amp;lt;1.45 except for one band with a VSWR&amp;lt;1.85. From 70.57% to 97.93%, the suggested structure’s radiation efficiency may be calculated. For a better understanding proposed antenna’s far field and scattering characteristics, we used CST Microwave Studio 2021. We may conclude that our suggested antenna is suitable for today’s wireless applications, which need multiband and multimode small antennas. Using a small stainless-steel wire as a switch, a prototype of the antenna design is built and tested to verify the simulation findings. The suggested reconfigurable antenna’s strong concordance between simulated and measured findings.&lt;/span&gt;

Research on the structural design and pentamodal property of three-dimensional multilayer cylindrical pentamode metamaterials for tuning acoustic waves

Pentamode metamaterial (PM) is an artificial solid form metamaterial with fluid characteristics. In this paper, a three-dimensional (3D) PMs based on multilayer cylindrical elements are proposed for increasing tunable structure parameters, obtaining great pentamodal property, reducing band gap frequency and decreasing connection overlap areas of elements. Compared with the PMs with double-cone elements, under the same parameters, the lower edge frequency of the single-mode band gaps can be reduced by 33.2%, the maximum value of figure of merit can be increased by 84.8% and the phononic band gaps can be reduced by 73.9%.

Single-/fused-band dual-mode mid-infrared imaging with colloidal quantum-dot triple-junctions

Image data acquired with fused multispectral information can be used for effective identification and navigation owing to additional information beyond human vision, including thermal distribution, night vision, and molecular composition. However, the construction of photodetectors with such capabilities is hindered by the structural complexity arising from the integration of multiple semiconductor junctions with distinct energy gaps and lattice constants. In this work, we develop a colloidal quantum-dot dual-mode detector capable of detecting, separating, and fusing photons from various wavelength ranges. Using three vertically stacked colloidal quantum-dot homojunctions with alternating polarity, single-band short-wave infrared imaging and fused-band imaging (short-wave and mid-wave infrared) can be achieved with the same detector by controlling bias polarity and magnitude. The dual-mode detectors show detectivity up to 8 × 10 10 Jones at the fused-band mode and 3.1 × 10 11 Jones at the single-band mode, respectively. Without image post-processing algorithms, the dual-mode detectors could provide both night vision and thermal information-enhanced night vision imaging capability. To the best of our knowledge, this is the first colloidal quantum-dot detector that can achieve such functionality. The operation mode can be changed at a high frequency up to 1.7 MHz, making it possible to achieve simultaneously dual-mode imaging and remote temperature sensing.

Shear strain evolution during tension-induced Lüders-type deformation of polycrystalline NiTi plates

This paper reports a new aspect of the Lüders-type deformation of NiTi. This is on the occurrence of lateral shear strains in a tension-induced Lüders deformation process. The phenomenon was studied by means of digital image correlation analysis. It was found that the lateral shear strains occurred in opposite directions within the Lüders band, apparently as an effort to self-accommodate the lateral displacement caused by the shear strains. The Lüders band propagation also changed from a single band mode to a branched mode when the lateral displacement, thus the in-plane bending moment, became too large. The branches, whilst having the same axial normal strain in the loading direction, were formed with opposite shear strains in double alternation between left and right of the sample and between the branches and the gaps between them, thus, to achieve the optimum self-accommodation. In addition, both the axial normal strain field and the lateral shear strain field were nonuniform after the Lüders-type deformation. These findings provide more insight and direct evidence for the explanation of the characteristics of Lüders deformation behaviour of NiTi.

Theoretical verification of three-dimensional manufacturable pentamode metamaterial microstructure

A special kind of pentamode metamaterial, which is composed of double-cone elements and forms simple-cubic lattice, is investigated in this paper. Based on finite-element method, the phonon band structure and the transmission spectrum of the pentamode metamaterial are calculated, and then the pentamodal behavior of this structure is theoretically verified from two aspects, i.e. the physical properties and the mathematical definition. Results show that in the phonon band structure, there is a wider single-mode band gap, corresponding to the remarkable loss in the transmission spectrum. The ratio of bulk modulus B to shear modulus G is more than 300, which is obviously larger than that of traditional materials. Except for the isotropic bulk modulus B, the other mechanical moduli are all anisotropic. Five of six eigenvalues of elastic coefficient matrix are nearly zero for the microstructure, and only one is non-zero. These results demonstrate that this metamaterial microstructure performs excellent pentamodal characteristics, and also conforms to the mathematical definition of ‘pentamode’.

Core-shell pentamode metamaterials with broader mechanical response and higher sensitivity

Core–shell pentamode metamaterial is designed and its phonon band structure is calculated by finite element method. Influences of factors, including constituent material and dimensions of the core-double-cone, on the mechanical properties and single-mode band gap (i.e. single-mode frequency regime, in which only compression wave exists and shear waves are completely suppressed) of the core–shell pentamode metamaterials are systematically investigated based on the static continuum mechanics calculations. It’s found that compared with the traditional non-core–shell pentamode metamaterial, the core–shell one has broader mechanical response and higher sensitivity (ratio of bulk modulus B to shear modulus G: B/G ∼ 104). Especially when the thin-end diameter of core-double-cone is smaller, the B/G ratio exceeds 6 × 104, which is nearly 54 times than that of non-core–shell structure. The smaller Young’s modulus E c of core material and the smaller dimension of core-double-cone will be conducive to obtain single-mode band gap with lower frequency and wider bandwidth.

Switching plasmonic resonance in multi-gap infrared metasurface absorber using vanadium dioxide patches

Reconfigurable metasurface absorbers enable collecting or emitting radiation within selected frequency bands. It is thus necessary to decipher such behavior for many applications, including plasmonic energy harvesting, radiative cooling and thermal emitters. In this article, we propose a compact reconfigurable vanadium dioxide (VO2)-based metasurface absorber/emitter to demonstrate switching between dual and single-band absorption modes in the mid-infrared regime. The unit cell of the design employs a four-split gold circular ring resonator with gaps filled with VO2 patches. The phase-transition property of VO2 between semiconductor and metallic states is used to control the mode of operation of the metasurface absorber. When VO2 is in the semiconductor state, a dual-band absorption at 6 μm and 10.6 μm is obtained. When it attains a metallic state, the metasurface exhibits a single-band absorption at 8.25 μm. To achieve the maximum absorption efficiency in both single and dual-band modes, adaptive wind-driven optimization was employed as a global optimization technique. The proposed absorber provides polarization-independent behavior for both Transverse Electric and Transverse Magnetic polarizations. Moreover, the proposed design shows above 80% absorptance for incidence angle up to 45° for the dual-band mode, and up to 35° for the single-band mode. When operating the absorber as a tunable emitter, a switching of 79% in emissivity is achieved at 8.25 μm. These favorable findings may facilitate the development of important devices for temperature regulation, smart windows, and thermal imaging.

Asynchronous Chirp Slope Keying for Underwater Acoustic Communication

We propose an asynchronous acoustic chirp slope keying to map short bit sequences on single or multiple bands without preamble or error correction coding on the physical layer. We introduce a symbol detection scheme in the demodulator that uses the superposed matched filter results of up and down chirp references to estimate the symbol timing, which removes the requirement of a preamble for symbol synchronization. Details of the implementation are disclosed and discussed, and the performance is verified in a pool measurement on laboratory scale, as well as the simulation for a channel containing Rayleigh fading and Additive White Gaussian Noise. For time-bandwidth products (TB) of 50 in single band mode, a raw data rate of 100 bit/s is simulated to achieve bit error rates (BER) below 0.001 for signal-to-noise ratios above −6 dB. In dual-band mode, for TB of 25 and a data rate of 200 bit/s, the same bit error level was achieved for signal-to-noise ratios above 0 dB. The simulated packet error rates (PER) follow the general behavior of the BER, but with a higher error probability, which increases with the length of bits in each packet.

Pentamode metamaterials with ultra-low-frequency single-mode band gap based on constituent materials

An effective method for realizing ultra-low-frequency single-mode band gap in pentamode metamaterials is proposed based on constituent materials. Results show that the decreasing ratio E/ρ (stiffness/mass density) of constituent material can significantly lower the frequency range of single-mode band gap. By merely replacing the constituent material from Al to rubber, the center frequency f c of single-mode band gap can be reduced nearly 600 times (from 3621 Hz to 6.5 Hz), while the normalized bandwidth Δf/f c and the ratio of bulk modulus B to shear modulus G of pentamode structure keep substantially stable. The nonlinear fitting demonstrates that the relation between f c and E/ρ satisfies the logarithmic function. The two-component pentamode structure is designed to further explore the ultra-low-frequency single-mode band gap. The effects of thick-end diameter D of double-cone, diameter D 0 and material type of additional sphere, on single-mode band gap of two-component system are analyzed. This work is attractive for several ∼Hz acoustic/elastic wave regulations using pentamode metamaterials.

The Design of a Switchable Infrared Hybrid Plasmonic Metasurface Absorber for Energy Harvesting Applications

A plasmonic switchable polarization-insensitive metasurface absorber is proposed. The design provides two modes of operation by employing phase-change material in semiconductor and metallic phases. In this paper, we study the switchable absorption behavior of the metasurface operating in a dual-band and single-band modes targeting the mid-infrared range suitable for energy harvesting applications such as thermophotovoltaics. The design is optimized using a global optimization technique.

A miniaturized frequency reconfigurable antenna with half-mode CRLH-embedded metamaterial arm

Metamaterial properties of a novel half-mode CRLH unit cell are investigated and hence a compact dual-wideband antenna is designed using an array of four unit cells. The negative refraction of the metamaterial cell is utilized to miniature the antenna. A via-free open stub, in combination with an interdigital capacitor, makes the half-mode CRLH unit cell. The proposed antenna operates at both C-band (6.2–6.8 GHz) and X-band (8.5–9.2 GHz). The dual-wideband antenna is enabled with frequency reconfigurability by incorporating RF PIN diode in its ground plane in the next design step. The ON–OFF conditions of the PIN diode electrically switch the antenna into dual-band and single-band modes, respectively. In OFF state of the diode, the antenna behaves as a monopole and operates in single-band mode resonating at C-band (5.9–6.5 GHz) only. The measured results of the fabricated sample are in good agreement with the simulated ones.

Design of a multimode tunable low noise amplifier for software defined radios

This Letter presents the design and analysis of a tunable low noise amplifier (LNA) capable of achieving single band, dual band and wideband operations. The circuit features a modified tunable open stub matching to achieve a reconfigurable multiband response. The LNA adopts a varactor diode in the input matching stage to achieve reconfigurable modes. Two bias conditions for the varactor diode are analysed. The forward bias condition yields a wideband mode (1.6 to 2.5 GHz) and zero bias results in a concurrent dual band mode (0.9 and 1.7–2.5 GHz). In reverse bias condition, the bias voltage of varactor diode () can be tuned to achieve one single band mode (1 GHz), and a tunable concurrent dual band mode, where the first band is fixed at 1 GHz and the second band is continuously tunable from 1.7 to 2.5 GHz. The LNA is fabricated in microwave integrated circuit process on an FR-4 board. The measured power gain is 7–15 dB and noise figure is 1.2–2.2 dB across all bands. The measured 1 dB compression () is , and at 0.9, 1 and 2.4 GHz, respectively.

A Compact Grounded Asymmetric Coplanar Strip-Fed Flexible Multiband Reconfigurable Antenna for Wireless Applications

A compact grounded asymmetric coplanar strip (GACS)-fed flexible multiband frequency reconfigurable antenna with two PIN diodes is proposed. The investigated antenna is backed by a flexible polyamide substrate with compact dimensions of 24 mm $\times19$ mm and a thickness of 1.53 mm. The investigated antenna structure contains a monopole patch that facilitates operation for wireless LAN applications, whereas inverted L-shaped and F-shaped monopoles facilitate operation for Bluetooth and 5G NR applications. The investigated antenna operates at 2.4, 3.8, and 5.6 GHz with measured impedance bandwidths of 5.8%, 6.3%, and 6.6%, respectively, over the three frequency bands, thus facilitating coverage for Bluetooth, 5G NR, and WLAN standards. The two PIN diodes are employed to tune the investigated antenna among four modes, including a single band mode (WLAN 5.5 GHz), two dual-band modes (5G NR 3.8/5.6 GHz, and Bluetooth 2.48/5.6 GHz), and one multiband mode with Bluetooth (2.4 GHz), 5G New Radio (NR) N77 band (3.8 GHz), and WLAN (5.6 GHz) modes. The investigated antenna radiates unidirectionally with a peak gain of 3.73 dBi at 5.6 GHz. Measurements are carried out on the human body to investigate the behaviour of the wearable antenna. The simulated SAR values are in a safe limit of 1.6 W/kg for 1 g of tissue, according to the FCC. Moreover, the investigated antenna shows extremely low vulnerability to degradation in performance as a result of bending effects concerning impedance matching with acceptable acquiescence between measurements and simulations.

A Photonics-Based Coherent Dual-Band Radar for Super-Resolution Range Profile

We propose and demonstrate a photonics-based coherent dual-band radar for super-resolution range profile in this paper. This radar cannot only generate coherent dual-band linear frequency modulated signals with large bandwidths, but also realize a paralleled coherent de-chirping processing to the dual-band echoes simultaneously based on a single compact photonics-assisted transceiver. The sharing of a single transceiver for signals with different bands ensures perfect stability and coherence among the waveforms, which makes it possible to realize a super-resolution range profile by fusion of dual-band signals without heavy computation on phase compensation. In the experiment, the radar operates in S -band with a bandwidth of 1.5 GHz and X -band with a bandwidth of 3 GHz, and results show its range resolution is up to 1.6 cm by coherent fusion processing, which is nearly corresponding to the resolution gotten by a linear frequency modulated wave with a bandwidth of 9.5 GHz ranging from 2 GHz to 11.5 GHz, much higher than the scenario when the radar is operated in the single-band mode. This technology would improve the accuracy of classification and recognition of the targets.

Design and analysis of a hexa-band frequency reconfigurable antenna for wireless communication

A compact (33 × 16 × 1.6 mm3) and novel shaped hexa-band frequency-reconfigurable antenna with a very wide tuning band is proposed. The proposed antenna operates at two single band modes (i.e., 3.5 GHz and 4.8 GHz) and two dual band modes (i.e., 2.10 GHz, 4.15 GHz and 2.4 GHz, 5.2 GHz) depending upon the switching states. The lumped elements are used in the simulation environment to achieve tunable capacitance, which is responsible for frequency reconfigurability. The measured tuning capability of the fabricated antenna ranges from 2.1 to 5.2 GHz. The proposed antenna has a VSWR < 1.3 for all the resonant bands. The radiation efficiency of the proposed structure ranges from 80.41% to 96% at the corresponding frequencies. The far field and the scattering parameters of the proposed antenna are analyzed using Computer Simulation Technology (CST) Microwave Studio 2014. The designed antenna, due to its compact and affordable geometry, can be easily integrated in the modern communication devices such as smart phones, laptops and other portable electronic devices. A prototype of the designed antenna is fabricated and measured using PIN diode switches to validate the simulation results. The proposed reconfigurable antenna demonstrates a reasonable agreement between the measured and simulated results.

Single-mode large-mode-area double-ring hollow-core anti-resonant fiber for high power delivery in mid-infrared region

Abstract A novel hollow-core anti-resonant fiber with a large mode area and good single mode performance is proposed for high power delivery in mid-infrared region. The structure consists of two-layer circular tubes as the cladding. By optimizing structure parameters, a broad low-loss single-mode band, in which the fundamental mode loss is lower than 4 × 10−3 dB/m and the high order mode extinction ratio (HOMER) is higher than 1000, is achieved in the wavelength region from 2.5 to 3.3 μm in which the lowest loss of 2.87 × 10−4 dB/m occurs at 3.1 μm. The effective mode area is up to 2314 μm2 with the highest HOMER of 16,600 at the wavelength of 2.8 μm. In addition, this fiber also has good bend resistance characteristics. When the fiber is bent at the bending radius of 18 cm, the mode area reaches to 2268 μm2 with the HOMER above 100 at the wavelength of 2.8 μm. Furthermore, the effective mode area can be further increased to 4714 µm2 by increasing core radius at the cost of sacrificing single mode performance and bending resistance.