Narrowband State Research Articles

Miniaturized bandwidth reconfigurable microwave bandpass filter

PurposeModern 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/approachThe 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.FindingsThe 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/valueThe 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.

Nanosensor Based on Fano resonance in a metal-insulator-metal waveguide structure coupled with a half-ring

Herein, an ultra compact plasmonics-based refractive index nanosensor is designed consisting of a metal–insulator-metal (MIM) waveguide with a silver-bar and a triangle stub, coupled with a half-ring resonator which can excite Fano resonance. The finite element method (FEM) is used to analyze the transmission spectra of the proposed design. The transmission spectra showed that there were typical Fano resonance line shapes, which roots in a coupling between the broadband state of triangle stub and the narrowband sta te of the half-ring. The effects of structural parameters of the whole system on transmission properties were analyzed, respectively. And the maximum sensitivity (S) of the system obtains 1723 nm/RIU, and figure of merit (FOM) can obtain 51. The proposed system has promising applications for integrated circuits, especially in nanophotonic sensors.

Fano Resonance in a MIM Waveguide with Two Triangle Stubs Coupled with a Split-Ring Nanocavity for Sensing Application.

Herein, a compact refractive index nanosensor comprising a metal- insulator- metal (MIM) waveguide with symmetric two triangle stubs coupled with a circular split-ring resonance cavity (CSRRC) is theoretically presented. An analysis of the propagation characteristics of the designed structure is discussed employing the finite element method (FEM). The calculation results revealed that a Fano resonance outline emerged, which results from an interaction between the continuous broadband state of the waveguide with two symmetric triangle stubs and the discrete narrowband state of the CSRRC. The influence of geometric parameters on sensing properties was studied in detail. The maximum sensitivity reached 1500 nm/RIU with a high figure of merit of 65.2. The presented structure has great applications for on-chip plasmonic nanosensors.

Narrow Band State of Charge (SOC) Control Strategy for Hybrid Container Cranes

This paper evaluates possibility of using a new hybrid system based on variable speed diesel generator (VSDG), Li-ion battery bank and supercapacitor bank (SC) for a rubber tire gantry crane (RTGC) used in container terminals. Existing commercial hybrid systems face difficulties producing high efficiencies, higher life span, and lower initial investment cost due to inheriting characteristics of batteries and supercapacitors. In the proposed power system, a variable speed diesel generator act as the principal energy source, while a Li-ion battery bank and SC bank act as an energy storage system. The battery supports the diesel generator during steady demand and further, it absorbs a part of energy during regeneration. The energy management strategy, control the power flow from different sources while maintaining battery state of charge (SOC) level within a narrow band. Unlike most battery systems, this narrow band operation of battery system increases its life span while reducing capacity fade. The originality of this study can be emphasized from this narrow band SOC control technique. Simulation results for real operational load cycles are presented showing a stable system operating under defined current limits which can enhance lifetime of battery system and increase fuel saving by downsizing 400 kW constant speed diesel generator to 200 kW VSDG.

A Reconfigurable Filtering Antenna With Integrated Bandpass Filters for UWB/WLAN Applications

This communication presents a new reconfigurable filtering monopole antenna design with three switchable states for UWB/WLAN applications. The antenna has three independent ports for ultra-wideband state, 2.4 GHz WLAN narrowband state, and 5.8 GHz WLAN narrowband state, respectively. The narrowband state at 2.4 GHz is produced by a first-order microstrip filter using an open-loop resonator, and the narrowband state around 5.8 GHz is obtained by involving a third-order hairpin bandpass filter in the RF path. Frequency reconfiguration is achieved by RF path selection using dc controlled p-i-n diodes. As a result, narrowband filtering responses at desired frequency bands can be achieved. One antenna prototype is simulated, fabricated, and measured. Measured reflection coefficients and radiation patterns demonstrate that the proposed reconfigurable filtering antenna is an eligible candidate for future multifunctional systems incorporating both UWB and WLAN systems.

Wideband-to-Narrowband Tunable Monopole Antenna With Integrated Bandpass Filters for UWB/WLAN Applications

A novel wideband-to-narrowband tunable monopole antenna with switchable integrated feed network for ultrawideband (UWB)/wireless local area network (WLAN) applications is proposed in this letter. The integrated feed network is composed of a 50 Ω microstrip line, an open-loop bandpass filter, and a three-pole hairpin bandpass filter. The feed network can enable the ultrawideband state, the 2.4 GHz WLAN narrowband state, and 5.8 GHz WLAN narrowband state separately by selecting different RF paths. The RF path selections resulting in frequency reconfiguration are realized by dc controlled p-i-n diodes. The antenna is simulated, fabricated, and measured. Measured tuning ranges and radiation patterns indicate that the proposed reconfigurable filtering antenna is in good performance. The antenna is suitable for multifunctional systems incorporating UWB and WLAN systems.

Reconfigurable and Tunable Filtenna for Cognitive LTE Femtocell Base Stations

A single-port uniplanar antenna with a built-in tunable filter is presented for operation in multiple LTE bands for cognitive femtocell applications. The antenna is based on a monopole microstrip patch fed by coplanar waveguide. The frequency reconfigurability is achieved by using two PIN diodes to couple or decouple a ring slot resonator filter from the antenna feed line. By switching the PIN diodes, the proposed design can operate in either wideband or narrowband modes. When the antenna operates in the narrowband state, two varactor diodes are used to continuously tune the narrowband frequency from 2.55 to 3.2 GHz, while the wideband state is obtained over the 1.35–6.2 GHz band. The diodes and their biasing networks have nearly no severe effect on the antenna characteristics. Prototypes of the proposed structure using ideal and real switches, with and without varactors, are fabricated and tested. Measured and simulated results are in good agreement, thus verifying the good performance of the proposed design. The obtained results show that the proposed antenna is very suitable for cognitive radio applications, in which the wideband mode is used for spectrum sensing and the narrowband mode for transmission at different frequency bands.

Frequency Reconfigurable Antenna for Wireless Communications Using GaAs FET Switch

A compact frequency reconfigurable antenna which could be easily switched between a narrowband state and a dual-band state is presented in this letter. The narrowband covers the WLAN (2.4-2.48 GHz) and WiMAX (2.5-2.69 GHz), while the dual-band supports the PCS (1.85-1.99 GHz) and WiMAX (3.4-3.69 GHz). The reconfigurability is achieved by using a single GaAs field effect transistor switch to change the length of the current flow path. The switch can be directly driven by digital signal, and no bias network is needed. The simulated results are in agreement well with the measured results. The proposed antenna is well suited to be integrated within the wireless handheld devices.

A Wideband-to-Narrowband Tunable Antenna Using A Reconfigurable Filter

A novel microstrip circular disc monopole antenna with a reconfigurable 10-dB impedance bandwidth is proposed in this communication for cognitive radios (CRs). The antenna is fed by a microstrip line integrated with a bandpass filter based on a three-line coupled resonator (TLCR). The reconfiguration of the filter enables the monopole antenna to operate at either a wideband state or a narrowband state by using a PIN diode. For the narrowband state, two varactor diodes are employed to change the antenna operating frequency from 3.9 to 4.82 GHz continuously, which is different from previous work using PIN diodes to realize a discrete tuning. Similar radiation patterns with low cross-polarization levels are achieved for the two operating states. Measured results on tuning range, radiation patterns, and realized gains are provided, which show good agreement with numerical simulations.

A NOVEL DEFECTED GROUND STRUCTURE WITH BOTH ADJUSTABLE CENTER FREQUENCY AND RECONFIGURABLE BANDWIDTH

A new defected ground structure (DGS) with tunable working frequency and reconflgurable bandwidth is proposed in this paper. The prototype combines the conventional DGS with T-shaped patch featuring narrow bandwidth and two such units located symmetrically featuring wide bandwidth. The proposed structure is designed, simulated and measured. By embedding two reversely-set PIN diodes and four varactors, the proposed structure achieves a narrow bandwidth with a tuning range of 21.1% and a wide bandwidth with a tuning range of 24.6%. In comparison, the bandwidth (i10dB) is about 13.6% for the narrowband state and 49.2% for the broadband state, where an approximately 4-times extension is obtained.

Pairwise quantum correlation formed in an ensemble of atomic two-level systems storing squeezed light

This paper characterizes a quantum correlation formed in an ensemble of atomic two-level systems that stores a narrow-band squeezed state of light by coherently trapping an electron in an atomic superposed state $a|1⟩+b|0⟩$. In the storage process, a photonic quantum correlation in the squeezed light is transformed into an atomic quantum correlation between $N$ atoms in an adiabatic way. If we regard the atomic superposed state as a 1/2-spin state and adopt the framework of a pairwise spin entanglement to analyze the atomic quantum correlation, we can identify a certain entangled state of a spin pair as the atomic signature of the squeezed light. The pairwise spin entangled state reflects all the physical properties of the squeezed light. By following the dissipative time evolution in the pairwise entangled state, we can describe the degraded properties of the squeezed light in retrieval.