Ultra-wideband Spectrum Research Articles

Spur line integrated single‐/dual‐/triple‐notched ultra‐wideband monopole antenna

Design and realization of spur line loaded frequency-notched planar ultra-wideband (UWB) antenna is proposed in this article. Accommodating the spur line (lines) of quarter wavelength long on the feeding microstrip line of UWB antenna, contributes to the notch-filtering action in the feeding section itself which in turn can provides single/double/triple notch (notches) within the UWB spectrum of the antenna. The proposed technique is very simple and radiator independent as the filtering is performed in the feed region and hence the UWB radiator can be independently designed. The spur line based filtering sections are first separately designed and verified by S-parameter measurements of the fabricated prototypes. Single, double, and triple spur line loaded microstrip sections are separately used as the feed section of a circular monopole antenna (MPA) to invoke single-, dual-, and triple-notched UWB response of the MPA. All the designed prototypes are fabricated and characterized in terms of impedance and radiation parameter measurements, yielding very close correspondence with that of results obtained from full wave simulation.

103 nm Ultra-Wideband Hybrid Raman/SOA Transmission Over 3 × 100 km SSMF

We report on the ultra-wideband (UWB) transmission of a 103 nm signal over 3 × 100 km of standard single mode fiber (SSMF), a widely-deployed fiber in terrestrial transmission networks. In such UWB systems, nonlinear effects such as stimulated Raman scattering (SRS) must be taken into account in the system design. We characterize the SRS impact in high power regime for this UWB spectrum. We study the evolution of SRS over the bandwidth when tilting the input spectrum to counter the inter-band power transition. We transmit 254 probabilistically constellation shaped (PCS)-64QAM channels over 300 km of SSMF and demonstrate a 107-Tb/s transmission throughput over a continuous 103 nm optical bandwidth using backward Raman pumping and SOA technology.

A CPW-fed Tomb Shaped Antenna for UWB Applications

In this paper a Coplanar Waveguide (CPW) fed tomb shaped antenna with novel broad banding techniques is proposed for Ultra-Wideband (UWB) applications. The initial design is taken as an elliptical radiator and techniques such as beveling of upper and lower half of elliptical radiator and introducing staircase in the coplanar ground plane of the antenna are used to significantly enhance the bandwidth. The proposed antenna has overall size of 50×38×1.6 mm3 and possess good radiation characteristics and return loss < -10 dB in the whole UWB spectrum from 2.8 GHz to 18 GHz. CST MICROWAVE STUDIO SUITE is employed for the design, optimization and simulation of antenna, which is based on method of finite integration technique (FIT). The performance of the proposed antenna is validated by comparing simulated and experimental results which exhibit that the designed antenna can be employed in various UWB applications.

Design methodology of the fractal annular ring antennas with the wideband operation

In this paper, a novel annular ring antenna is proposed to achieve a multi-wideband antenna. The structure is annular ring. For systematic design of the antenna, fractal shape is employed. Each iteration of the structure acts as a matching load for the previous section. Consequently, by increasing the electrical current path, multi-band and wideband performances can be achieved. For tuning the frequency bands, three slots are cut from the ground plane. The first operating band is from 1.47 GHz to 1.86 GHz (fractional band width (FBW): 23.42%), the second band is from 2.44 GHz to 3.51 GHz (FBW: 35.96%), and the third one is from 4.49 GHz to 5.34 GHz (FBW: 17.29%). Furthermore, the antenna has the ability to cover the ultra-wideband (UWB) spectrum by inserting two vias in the substrate. Using vias, impedance matching of the antenna is improved in the frequency range from 2.8 GHz to 5 GHz (FBW: 56.4%) with criteria |S11|<−10 dB. Also, it has a noticeable impedance bandwidth (FBW: 117%) from 1.3 GHz to 5 GHz with criteria |S11|<−6 dB. A prototype of the proposed antenna is fabricated and tested. The measurement and simulation results are in good agreement.

Ultrawideband Surface Enhanced Raman Scattering in Hybrid Graphene Fragmented‐Gold Substrates via Cold‐Etching

AbstractConventional surface enhanced Raman scattering (SERS) substrates are well known for their supreme electromagnetic enhancements and ultrahigh sensitivity in detecting molecules at low concentrations. However, large‐area quasi‐uniform SERS substrates are difficult to achieve by standard top‐down nanofabrication techniques, resulting in fluctuant SERS responses and unwanted fluorescence interferences, which severely limit their performances in practical applications. To tackle these challenges, a large‐scale quasi‐uniform hybrid graphene fragmented‐gold substrate with stable and reproducible SERS readouts as well as large enhancement factors over an ultrawideband spectrum is developed. The hybrid substrate is fabricated via cold‐etching through a controllable break up of a thin gold film followed by a graphene transfer. The stimulated localized surface plasmons interact strongly with the graphene layer, leading to spectrally and spatially modified graphene‐mediated surface enhanced Raman scattering (GSERS) responses. The perfect monolayer graphene of the GSERS substrate prevents adsorbates from the atmosphere and direct contact between bonded molecules and gold, thus reducing the catalytic activity of gold and producing clean, stable, and reproducible molecular Raman signals. The easy‐fabricated hybrid GSERS substrate not only provides a powerful platform to collect robust molecular Raman spectra but also shows great potentials for future mass production of high‐performance nanophotonic devices.

A Compact Four-Port Coplanar Antenna Based on an Excitation Switching Reconfigurable Mechanism for Cognitive Radio Applications

In this paper, we propose a compact four-port coplanar antenna for cognitive radio applications. The proposed antenna consists of a coplanar waveguide (CPW)-fed ultra-wideband (UWB) antenna and three inner rectangular loop antennas. The dimensions of the proposed antenna are 42 mm × 50 mm × 0.8 mm. The UWB antenna is used for spectrum sensing and fully covers the UWB spectrum of 3.1–10.6 GHz. The three loop antennas cover the UWB frequency band partially for communication purposes. The first loop antenna for the low frequency range operates from 2.96 GHz to 5.38 GHz. The second loop antenna is in charge of the mid band from 5.31 GHz to 8.62 GHz. The third antenna operates from 8.48 GHz to 11.02 GHz, which is the high-frequency range. A high isolation level (greater than 17.3 dB) is realized among the UWB antenna and three loop antennas without applying any additional decoupling structures. The realized gains of the UWB antenna and three loop antennas are greater than 2.7 dBi and 1.38 dBi, respectively.

A Compact Quad-Element UWB-MIMO Antenna System with Parasitic Decoupling Mechanism

This research work proposes a compact four-port multiple-input multiple-output (MIMO) antenna that operates in the whole license free ultra-wideband (UWB) spectrum of 3.1–10.6 GHz. Spatial diversity has been introduced by arranging these antennas in close proximity without developing a strong mutual coupling. Antenna elements are evolved from a conventional rectangular patch antenna whereas a customized decoupling structure is introduced on the back side of the substrate to achieve the desired isolation level. The parasitic decoupling structure consists of different features which are resonant at different frequencies offering a whole UWB coverage. In addition to the decoupling structure a dumbbell shaped stub has also been introduced to the partial ground plane to suppress the mutual coupling. The overall measured isolation among elements is more than 20 dB. Different MIMO performance parameters have also been investigated from the measured results. Whole MIMO system measures 0.41 λo × 0.44 λo at 3.1 GHz. The MIMO system is intended for high data rate and short-range communication devices used in wireless personal area networks.

VCSEL-based broadband wavelength converter for ultra-wideband flexible spectrum data routing in optical interconnects

Abstract High-speed real-time wavelength conversion at key data centre network nodes is an emerging fundamental functionality requirement for transparent content resolution, wavelength assignment and routing towards better utilization of network resources under dynamic traffic patterns. In this paper, we experimentally demonstrate the first vertical cavity surface emitting laser (VCSEL)-based broadband wavelength converter for ultra-wide wavelength routing in Datacom. An 850 nm multimode VCSEL is directly modulated with 8.5 Gbps data and successfully transmitted error-free over 100 m OM3 multimode fibre (MMF) with a receiver sensitivity of −16.04 dBm, and a total transmission penalty of 1.14 dB. The received data is then used to run two cascaded single mode VCSELs at 1550 nm within the network integration node, therefore achieving the first reported real-time inter-band wavelength converter to C-band. By exploiting VCSEL wavelength tuneability with changing bias current, we show that the converted wavelengths can be routed over 3.2 nm spectra range for integration into ITU-T 50 GHz flexible grid and beyond. The newly converted wavelengths are successfully transmitted over 24.7 km of G 655 single mode fibre, achieving a minimum receiver sensitivity of −14.28 dBm, with a maximum transmission penalty of 2.72 dB. This work offers a viable enabling development technology for broadband wavelength converters for real-time wavelength routing in optical interconnects to address content resolution and wavelength assignment problem for current and future Datacom.

Miniaturization of Monopole Patch Antenna with Extended UWB Spectrum via Novel Hybrid Heuristic Approach

Many of the wireless systems employ ultra wide band (UWB) for its efficient data rate and optimal power consumption. However, all the wireless devices need to have antenna size as small as possible. It is therefore important to design an antenna having the desired UWB features along with highest possible degree of miniaturization. In addition, it gives sufficient flexibility if different geometrical shaped antennas have the same physical and/or electro-magnetic characteristics. To jointly design such multi featured antennas is a complex multi objective optimization problem. These types of problems cannot be solved through classical numerical approaches; instead they require soft computing techniques to find the optimum results. This paper proposes a novel hybrid genetic particle swarm optimization algorithm to jointly optimize three printed monopole antennas for high degree of miniaturization. Moreover, attempt is also made to extend UWB spectrum to have more room for data transmission. The results are effective and promising.

Adaptive Sub-Nyquist Spectrum Sensing for Ultra-Wideband Communication Systems

With the ever-increasing demand for high-speed wireless data transmission, ultra-wideband spectrum sensing is critical to support the cognitive communication over an ultra-wide frequency band for ultra-wideband communication systems. However, it is challenging for the analog-to-digital converter design to fulfill the Nyquist rate for an ultra-wideband frequency band. Therefore, we explore the spectrum sensing mechanism based on the sub-Nyquist sampling and conduct extensive experiments to investigate the influence of sampling rate, bandwidth resolution and the signal-to-noise ratio on the accuracy of sub-Nyquist spectrum sensing. Afterward, an adaptive policy is proposed to determine the optimal sampling rate, and bandwidth resolution when the spectrum occupation or the strength of the existing signals is changed. The performance of the policy is verified by simulations.

Compact UWB Band-Notched Antenna with Integrated Bluetooth for Personal Wireless Communication and UWB Applications

A compact band-notched UWB (Ultra-Wide Band) antenna with integrated Bluetooth is developed for personal wireless communication and UWB applications. The antenna operates at the UWB frequency band (3.1–10.6 GHz) as well as Bluetooth (2.4–2.484 GHz), with band-notch characteristics at the Wireless Local Area Network (WLAN) frequency band (5–6 GHz). A new technique of integrating Bluetooth within a UWB band-notched antenna is developed and analyzed. The UWB frequency band is realized by utilizing a conventional cylindrical radiating patch and a modified partial ground plane. The Bluetooth band is integrated using a miniaturized resonator with the addition of capacitors. Further, to mitigate the interference of the WLAN frequency band within the UWB spectrum, a conventional slot resonator is integrated within the radiator to achieve the task. The antenna is designed and fabricated, and its response in each case is provided. Moreover, the antenna exhibits a good radiation pattern with a stable gain in the passband. The present antenna is also compared to state-of-the-art structures proposed in the literature. The miniaturized dimensions (30 × 31 mm2) of the antenna make it an excellent candidate for UWB and personal wireless communication applications.

Miniaturised UWB antenna with dual‐band rejection of WLAN/WiMAX using slitted EBG structure

This study presents a new slitted electromagnetic bandgap (EBG) structure to filter undesired wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) bands in the ultra-wideband (UWB) spectrum. A simple UWB antenna which consists of a microstrip tapered feed line, a circular patch and a defected ground structure is used as a reference antenna. The antenna is then integrated with a slitted EBG structure near the feed line to notch two interfering bands. The created notched bands by the EBG structure can be independently controlled. Owing to structural symmetry of the proposed antenna, the size can be reduced by approximately half to form a miniaturised antenna. The miniaturised antenna has the same full-size antenna characteristics with little change in the notched bands specifications. Frequency domain measurement results show that the full-size and miniaturised antennas have a flat transfer function, and a group delay variation of about 0.5 ns in the entire UWB band except for the notched bands.

An Integrated Tri-Band/UWB Polarization Diversity Antenna for Vehicular Networks

The design, fabrication, and testing of an integrated polarization diversity antenna array for maximizing the wireless channel link in vehicular networks are presented in this paper. The diversity antenna is constructed using unit cell radiators that provide two operating modes. The mode transition is achieved using a pair of PIN diodes. In one state, the antenna provides multiband operation centered at 2.4, 3.5, and 5.8 GHz. In the other state, the antenna covers the entire ultra-wideband (UWB) spectrum. The unit cell radiators are distributed in the horizontal and vertical plane to achieve polarization diversity. Apart from offering a polarization diversity antenna, the orientation of antennas offers a reliable link with the communication devices. The prototype antenna array is fabricated and tested for diversity performance. The performance metrics such as envelope correlation coefficient, diversity gain, and mean effective gain under isotropic, indoor, and outdoor conditions are evaluated and presented.

A dual notched band UWB-BPF based on microstrip-to-short circuited CPW transition

AbstractThis paper proposes a dual notched band ultra-wideband (UWB) bandpass filter (BPF) based on hybrid transition of microstrip and coplanar waveguide (CPW). The CPW in ground plane houses a stepped impedance resonator shorted at ends, and is designed to place its resonant modes within the UWB passband. The microstrips on the top plane are placed some distance apart in a back-to-back manner. The transition of microstrip on top and shorted CPW in the ground is coupled through the dielectric in a broadside manner. The optimized design of the transition develops the basic UWB spectrum with good return/insertion loss and extended stopband. Later, defected ground structure, embedded in CPW, and split ring resonators, coupled to feeding lines are utilized to develop dual sharp passband notches. The simulated data are verified against the experimentally developed prototype. The proposed dual notched UWB-BPF structure measures only 14.6 × 7.3 mm2, thereby justifying its compactness.

A Five-Port Integrated UWB and Narrowband Antennas System Design for CR Applications

The main motive of this paper is to discuss a design of compact five-port integrated ultrawideband (UWB) and narrowband (NB) antennas system for cognitive radio applications. The proposed system composes of one UWB antenna for spectrum sensing and four NB antennas for communication. The UWB and NB antennas are printed on a very compact FR-4 substrate of dimensions 40 mm $\times36$ mm $\times1.6$ mm. The UWB antenna coupled with port 1 is designed to sense the complete UWB spectrum of 3.1–10.6 GHz approved by Federal Communications Commission in 2002. The four NB antennas operate at different single or dual bands to cover the complete UWB spectrum. In particular, the first NB antenna allied with port 2 achieves a single operating band ranges from 8.7 to 9.92 GHz. The second NB antenna associated with port 3 also covers a single band from 9.82 to 10.74 GHz. The third NB antenna linked to port 4 yields dual bands from 3.06 to 4.23 GHz and 6.33 to 8.83 GHz. The fourth NB antenna accessed at port 5 operates in a single band from 4 to 6.37 GHz. Isolation between the antennas is less than 16 dB over the antennas operating bands. Finally, the proposed integrated structure is fabricated and verified. Experimental results have a good agreement with the simulated results.

Dual-Band Skin-Adhesive Repeater Antenna for Continuous Body Signals Monitoring

We present a 35-mm diameter skin-adhesive antenna intended to operate as a gateway to relay the low power signals from a sensor implanted in the body to an external base station (BS). Such a device would be useful in the context of body area networks (BANs) for continuous body-signal monitoring. The proposed adhesive repeater is of very low profile, and it is designed for dual-band operation at the ISM band (2.4 GHz) and in the ultrawideband (UWB) spectrum (4–10.6 GHz) using a single excitation port. The ISM band is used for in-body communication with the implants and the UWB band for off-body burst communication with the BS. The antenna consists of three layers that grant it compactness and performance robustness. We assess the in-body link between the repeater and a custom-designed miniaturized implantable probe antenna. The study is performed in the frequency domain with results showing adequate input impedance matching ( s 11 ≤ −10 dB) and robustness to different body parts. We extend the analysis to time domain by transmitting a synthetized medical signal between the two antennas. In addition, we evaluate the feasibility of an off-body link for burst communication. Again, the results indicate very good performance by the repeater antenna both in terms of impedance matching ( s 11 ≤ −10 dB) and preservation of time signals (fidelity ≥ 75%), which is relevant in impulse radio systems. To the authors’ best knowledge, this is the first time this kind of dual-band adhesive antenna is being proposed for BANs, complete with performance tests using frequency- and time-domain figures-of-merit.

High-Accuracy Indoor Localization Based on Chipless RFID Systems at THz Band

Highly accurate indoor localization based on significantly low complex infrastructure has recently gained great interest for a variety of innovative location-based applications. In this regards, the chipless radio frequency identification (RFID) system is presented to be the low-cost solution, while time-based ranging using the ultrawide-band spectrum is promising to offer precise ranging capability. However, the current wide-band systems suffer from the spectrum and power limitations, which restrict the function of chipless RFID-based localization systems. Therefore, we propose terahertz (THz)-based chipless RFID localization system that enables a smart object localizing itself using the infrastructure composed from reference chipless tags. In more details, THz band offers huge bandwidth providing superior-resolution localization and large coding capacity. Moreover, we utilize the combination between dielectric resonator (DR) and lens to be designed as a frequency-coded chipless tag, where this combination increases the radar cross section of the chipless tags and, hence, extends their coverage zone. This cost-efficient design of the tag enables the dense deployment of low-cost infrastructure acting as reference anchors. Furthermore, we investigate the link budget of the proposed system in order to characterize the tag and distance-dependent spectral windows that are feasible for RFID-based localization. Afterward, the time-domain backscattered signal from a DR-Lens tag is analyzed in order to perform ranging and to calculate the relative distances between the DR-Lens tags and the reader leading to determining the reader position. Measurements are performed to prove the concept of the DR-Lens tag, while the numerical simulation is conducted to evaluate the proposed localization system. Simulation results show that the proposed system can reach superior accuracy of millimeter-levels.

Design of Compact Quad-Band Notched UWB-MIMO Antenna

With quad-notched band characteristic, a compact ultra-wideband (UWB) multiple-input-multiple-output antenna is proposed in the article. There are two identical monopole elements in the system. By inserting symmetrical L-shaped slots, complementary split-ring resonators) and C-shaped stubs in each element, four notched bands are achieved to filter 3.5 GHz WiMAX, 5.25 GHz lower WLAN, 5.8 GHz upper WLAN, and 7.5 GHz X-band. Without decoupling structures, the antennas were placed vertically to obtain high isolation. Results indicate that the antenna operates from 2.6 to 13 GHz except four rejected bands, and port isolation (S21) is better than −25 dB, envelope correlation coefficient is below 0.002 in UWB spectrum frequency of 3.1–10.6 GHz.

Dual band monopole antenna based on metamaterial structure with narrowband and UWB resonances with reconfigurable quality

In this article, an Ultra Wide Band (UWB) monopole antenna based on Metamaterial (MTM) unit cell with reconfigurable feature has been developed. The proposed antenna covers 3.1–10.6GHz for UWB applications and it has a reconfigurable narrow-band for L-band (1.27GHz) and wireless applications. The gaps in Split Rings Resonator (SRR) element are made for the Left-hand capacitance and Ω-shape strip layer by four via junctions are used for Left-hand inductance. The antenna is printed on FR-4 low cost substrate with relative permittivity of 4.4 and thickness of 1.6mm. The total size of the antenna is 40mm×40mm. The simulation is carried out using HFSS commercial full-wave software. In addition, the experimental results are presented and compared with simulated results. The antenna gives a maximum peak gain of 6dBi with Omni-Directional radiation pattern and high efficiency of more than 70%. By embedding four switches in Ω-shape strip layer, a reconfigurable antenna has been successfully designed for wireless applications with sufficient qualification. The monopole part covers the UWB spectrum and the CRLH is responsible for the controllable narrowband resonance. The simulation and experimental results are confirmed by the numerical results.

VO2‐Based Reconfigurable Antenna Platform with Addressable Microheater Matrix

This study reports on a reconfigurable antenna platform based on vanadium dioxide (VO2), a phase‐change material (PCM) with low transition temperature, integrated with an addressable microheater matrix. For the first time, it is shown that an entire planar antenna can be thermally reconfigured virtually to any pattern by switching the phase of the selected regions of the VO2 layer from insulator to metallic state by indirect thermal stimuli generated by individually addressable nichrome resistive microheaters. Careful selection of the individual pixels to start the phase transition from insulator (OFF) to metallic (ON) state allows creating different antenna patterns with unique resonance properties. Reconfiguring the antenna into different patterns, operating frequency can be tuned from C‐band (4–8 GHz) to X‐band (8–12 GHz), and S‐band (2–4 GHz) frequencies which cover the entire ultra wideband spectrum (3.1–10.6 GHz). The proposed approach provides a promising platform for designing monolithically integrated reconfigurable antennas, radio frequency devices, and circuits for various applications.