Ultra-wideband Frequency Research Articles

Ultrawideband Frequency Synthesis Using the Compact Tunable Transmission Line (CTTL)

Due to the rapid adoption of mmW bands for 5G communications, the complexity of transceiver systems must increase to operate over ever further separated frequency bands. In more traditional sub-6-GHz bands, software-defined radio (SDR) techniques allow for unified, multiband RF front ends; however, maintaining this ultrawideband or ultrawide tunable operation at mmW frequencies poses many challenges. One such challenge is ultrawideband mmW frequency synthesis, a challenge for which we present a new lumped/distributed tunable LC structure, the compact tunable transmission line (CTTL). In this article, we observe how the CTTL enables a state-of-the-art −203-dBc/Hz FOM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{T}$ </tex-math></inline-formula> multioctave tunable mmW VCO, achieving a >4 octave tuning range with output up to 51 GHz. To analyze the CTTL in comparison to conventional tunable LC VCOs, we develop a new phase noise and oscillator figure-of-merit (FOM) model that provides an analysis framework for wide LC tuning. This new model is verified against simulation for conventional tuning and then is used to show how the CTTL provides a higher <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> and, therefore, better oscillator performance compared with existing LC tuning methods in the case of multioctave frequency synthesis. This analysis is then confirmed by the measured results of the manufactured CTTL VCO.

Triangular Director Dipole Antenna with Rectangular Impedance Balun

This study presents a triangle director dipole antenna with a rectangular impedance balun (RIB). The proposed antenna consists of a triangular director, a coplanar waveguide (CPW) to coplanar stripline (CPS) transition line, and the RIB. The proposed triangle director substitutes a typical director of a planar quasi-Yagi dipole antenna. The triangle director has modified a director of a planar quasi-Yagi dipole antenna. The triangle director generates a circular polarization. Also, the RIB has proposed to match an impedance between the CPW-fed to the CPS transition line. It obtains an ultra-wide frequency band of 4020 MHz (2160 - 6180 MHz), and a peak realized gain of 12.5 – 6.2 dBi in the operating frequency band. The proposed antenna shifts the resonant frequency to a lower frequency band of 75% than the typical planar dipole antennas. The proposed antenna uses widely for wireless medical communication, both ISM bands and C-V2X applications.

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.

An Ultrawideband Three-Dimensional Bandpass Frequency Selective Surface

A new ultrawideband frequency selective surface(FSS) is proposed, which exhibits six resonances to achieve a flat passband. It consists of a three-dimensional (3-D) configuration. However, unlike many other 3-D FSSs, the proposed structure can be assembled through simple steps involving single-layer printed circuit board (PCB) fabrication only. Its unit-cell consists of a wire-loop conducting pattern, printed on a dielectric substrate. The pattern excites four resonances while two resonances are contributed by the dielectric. These six resonances are properly tuned and coupled to form an ultrawide frequency band from 7.53 to 29.45 GHz. It translates to a <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> 3 dB bandwidth of 119 <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> . Our design guidelines and discussions are validated through both simulation and measurement results.

Performance Analysis of Metamaterial-Inspired Structure Loaded Antennas for Narrow Range Wireless Communication

Nowadays, the demand for low-cost, compact, and interference rejected antennas with ultrawideband capability has been increased. Metamaterial-inspired loaded structures have capability of providing exceptional solutions for narrow range wireless communication and low consuming power while transmitting and receiving the signal. It is a difficult task to construct ideal metamaterial-inspired antennas with a variety of features such as extremely large bandwidth, notching out undesirable bands, and frequency. Metamaterial-inspired structures such as SRR and CSRR, and triangle-shaped TCSRR are most commonly used structures to achieve optimized characteristics in ultrawideband antennas. In this paper, an extensive literature survey is accomplished to get conception about metamaterial-inspired patch antennas. This review paper elucidates variants of metamaterial-inspired structures/resonators utilized in order to acquire sundry applications such as WiMAX, WLAN, satellite communication, and radar. Various researchers have used different methodology to design, stimulate, and analyze the metamaterial-inspired structure loaded antennas. Also, the results of different metamaterial-inspired antennas such as bandwidth, gain, return loss, and resonant frequency have been also represented in this paper. This manuscript also gives brief introduction about the metamaterial, its types, and then its application in microstrip patch antenna over the last decade. This manuscript throws light over the various studies conducted in the field of metamaterial-inspired antenna in the past. It has been seen that with the inclusion of metamaterial in conventional antenna, various characteristics such as impedance bandwidth, reflection coefficient, gain, and directivity have been improved. Also, frequency rejection of narrow bands which exits in ultrawideband frequency range can be done by embedding metamaterial-inspired structures such as SRR and CSRR.

A single port frequency reconfigurable antenna for underlay/interweave cognitive radio

&lt;span&gt;A frequency reconfigurable antenna is presented in this paper as a novel single port system gathering the functionalities of both underlay and interweave cognitive radio. This 25×30×0.8 mm&lt;sup&gt;3&lt;/sup&gt; system involves a wide slot antenna to cover the ultra wide band (UWB) range with resonating stubs that are used to prohibit/work-only-in specific bands within the UWB frequencies. Here, six positive intrinsic negative (PIN) diodes are used to decide the active sections of the antenna that leads to select its operation as UWB/filtering/multiband antenna. Diodes' configuration results in eight useful operation modes that include a scanning mode, four single band-notch modes and three dual band communication modes. The scanning mode covers the entire UWB range while one of the bands allocated for WiMax, Cband, WLAN or Xband is to be excluded in each of the band-notch modes. On the other hand, each communaication mode is able to work in one of the ranges that cover WiMax/Cband, Cband/WLAN or Xband/international telecommunication union (ITU). S11, realized gain, voltage standing wave ratio (VSWR) outcomes of this design that is simulated by computer simulation technology (CST) v.10 all confirms the proposed system's ability to work in the intended modes. Its novelity to work as interweave/underlay cognitive radio system, highly candidates this design to address many of the UWB communication issues related interference and multiband operation&lt;/span&gt;

Design and Optimizing of Compact Ultra-Wide Band Printed Patch Antenna Employing Different Optimization Algorithms Based on Plant Inspiration

In this paper, a compact ultra-wide band (UWB) printed patch antenna is designed and optimized using four biologically and plant inspired optimization algorithms. These algorithms are the newly adopted Moss Rose Optimization Algorithm (MROA), Runner Root Algorithm (RRA), Sunflower Optimization Algorithm (SFOA) and Particle Swarm Optimization (PSO). These algorithms are modified in an optimizer software, which merges the attributes of the design of electromagnetic environment of CST Microwave Studio with those of the technical programming environment of MATLAB. A compact (12 × 21.5) mm2 printed patch antenna has been proposed and simulated over the whole UWB frequency range using these four optimization algorithms. The simulation results show the superiority of the antenna design using MROA, which has the widest covered frequency range, the lowest reflection coefficient and the lowest standing wave ratio.

Compact dual-band MIMO cubical antenna for automotive applications

ABSTRACT There is a strong demand for compact and multiband antennas as wireless technologies become more integrated into automobiles. These antennas must be able to serve multiple services without compromising the size and installation space. In addition, the antenna incorporated should not affect the aesthetic appearance of the vehicle. This paper presents a compact multiple-input-multiple-output (MIMO) antenna working at 2.45 GHz (Wi-Fi/Bluetooth/RFID) and ultra-wideband (UWB) frequencies. A basic rectangular monopole with a self-complementary structure is used to design the antenna element. The size of the antenna element is 20 × 22 mm2. The proposed MIMO cube is developed with four antenna elements in cubical orientation to achieve compactness and better isolation. The overall dimension of the MIMO antenna is 35 × 22 mm2. The diversity antenna shows impedance bandwidth of 2.4–11.5 GHz and isolation of more than 20 dB. The envelope correlation coefficient (ECC) of the MIMO antenna is less than 0.2, diversity gain (DG) is greater than 9 dB, and total active reflection coefficient (TARC) and channel capacity loss (CCL) are less than −10 dB and 0.4 bits/s/Hz, respectively. The gain and efficiency are found to be greater than 1 dBi and 72%, respectively.

Theory of Emergent Inductance with Spin-Orbit Coupling Effects.

We extend the theory of emergent inductance, which has recently been discovered in spiral magnets, to arbitrary magnetic textures by taking into account spin-orbit couplings arising in the absence of spatial inversion symmetry. We propose a new concept of spin-orbit emergent inductance, which can be formulated as originating from a dynamical Aharonov-Casher phase of an electron in ferromagnets. The spin-orbit emergent inductance universally arises in the coexistence of magnetism and the spin-orbit couplings, even with spatially uniform magnetization, allowing its stable operation in wide ranges of temperature and frequency. Revisiting the widely studied systems involving ferromagnets with spatial inversion asymmetry, with the new perspective offered by our work, will lead to opening a new paradigm in the study of spin-orbit physics and the spintronics-based power management in ultrawideband frequency range.

Data Transmission Enhancement Using Optimal Coding Technique Over In Vivo Channel for Interbody Communication.

Wireless in vivo actuators and sensors are examples of sophisticated technologies. Another breakthrough is the use of in vivo wireless medical devices, which provide scalable and cost-effective solutions for wearable device integration. In vivo wireless body area networks devices reduce surgery invasiveness and provide continuous health monitoring. Also, patient data may be collected over a long period of time. Given the large fading in in vivo channels due to the signal path going through flesh, bones, skins, and blood, channel coding is considered a solution for increasing the efficiency and overcoming inter-symbol interference in wireless communications. Simulations are performed by using 50 MHz bandwidth at Ultra-Wideband frequencies (3.10-10.60 GHz). Optimal channel coding (Turbo codes, Convolutional codes, with the help of polar codes) improves data transmission performance over the in vivo channel in this research. Moreover, the results reveal that turbo codes outperform polar and convolutional codes in terms of bit error rate. Other approaches perform similarly when the information block length is increased. The simulation in this work indicates that the in vivo channel shows less performance than the Rayleigh channel due to the dense structure of the human body (flesh, skins, blood, bones, muscles, and fat).

Circular ring shaped ultra-wideband metamaterial absorber with polarization insensitivity for energy harvesting

&lt;span&gt;A circular ring-shaped metamaterial (CRM) absorber was designed to harvest radio frequency (RF) energy in the ultra-wideband (UWB) frequency band applications. The proposed metamaterial unit cell features a circular shaped structure, with rectangular strip lines connected in the form of a cross leaving a square shaped slot at center. The unit cell dimensions are 15×15×1.6 mm. The absorber was etched on a low cost FR4 substrate having a dielectric constant of 4.4. Ansys high frequency structure simulator (HFSS) software was used for simulation and the analysis were carried out for unit cell, 2×2, 3×3, and 4×4 array structures. The absorber parameters plotted are absorption characteristics and reflection characteristics. Also, the metamaterial parameters (μeff) and (εeff) are also retrieved from the absorber parameters and analyzed. From the analysis, the values (μeff) and (εeff) were found to be negative, leaving refractive index also negative (n&amp;lt;0), which proved the metamaterial property. The proposed CRM absorber showed good absorption characteristics of more than 80% and also metamaterial property in the entire UWB band (4-13 GHz). Hence the absorber proves to be a good candidate in powering low power sensors/microcontrollers for internet of things (IoT) applications.&lt;/span&gt;

On the Modeling and Multi-objective Optimization Design of Compact Planar Ultra-wideband Impedance Transformer

Abstract A versatile scheme for design of planar ultra-wideband impedance transformer is proposed by using fragment-type structures (FTS) for modeling and MOEA/D-GO for optimization. To improve the optimization efficiency, non-uniform FTS cells are applied. To find the optimal planar FTS transformer, two objective functions characterizing the return loss and the insertion loss of the impedance transformer, respectively, are defined on a ultra-wide bandwidth. For demonstration, a 25-ohm to 50-ohm FTS impedance transformer is designed, which acquires reflection coefficient lower than -20 dB and extra insertion loss less than 0.27 dB in ultra-wide frequency band of 0.89-5.00 GHz.

A 3–5-GHz, 385–540-ps CMOS true time delay element for ultra-wideband antenna arrays

This paper proposes an all-pass filter-based true time delay (TTD) element covering a 3–5-GHz ultra-wideband (UWB) frequency. The proposed TTD element designed in a standard 0.18-μm CMOS technology achieves a tunable delay range of 385–540 ps with 6-ps delay steps and maximum 11% absolute delay error over a 3–5-GHz frequency band. It exhibits an average 3.6–4.6-dB noise figure (NF) within the whole bandwidth. A four-channel beamforming receiver realized by the proposed TTD element is designed and examined in this paper, as well. With the maximum delay of 540 ps and 6-ps average delay resolution, a maximum steering angle of ±45° with 5° (18 steps) steering resolution is demonstrated for the beamforming receiver with 2-cm antenna spacing.

A Multiband/Multistandard 15–57 GHz Receive Phased-Array Module Based on 4 × 1 Beamformer IC and Supporting 5G NR FR2 Operation

This work presents a 15&#x2013;57 GHz multiband/ multistandard phased-array architecture for the fifth-generation (5G) new radio (NR) frequency range 2 (FR2) bands. An eight-element phased-array receive module is demonstrated based on two four-channel wideband beamformer chips designed in the SiGe BiCMOS process and flipped on a low-cost printed circuit board. The SiGe Rx chip employs RF beamforming and is designed to interface to a wideband differential Vivaldi antenna array. Each channel consists of a low-noise amplifier (LNA), active phase shifter with 5-bit resolution, variable gain amplifier (VGA), and differential-to-single-ended stage. The four channels are combined using a wideband two-stage on-chip Wilkinson network. The beamformer has a peak electronic gain of 24&#x2013;25 dB and a 4.7&#x2013;6.2 dB noise figure (NF) with a &#x2212;29 to &#x2212;24 dBm input <inline-formula> <tex-math notation="LaTeX">$P_{\boldsymbol {1\,dB}}$ </tex-math></inline-formula> at 20&#x2013;40 GHz. The eight-element phased-array module also achieved ultra-wideband frequency response with flat gain and low-system NF. The phased array scans &#x00B1;55&#x00B0; with <inline-formula> <tex-math notation="LaTeX">$ &lt; -12$ </tex-math></inline-formula>-dB sidelobes demonstrating multiband operation. A 1.2-m over-the-air (OTA) link measurement using the eight-element Rx module supports 400-MHz 256-QAM OFDMA modulation with &#x003C; 2.76&#x0025; error vector magnitude (EVM) at multiple 5G NR FR2 bands. To the author&#x2019;s knowledge, this work achieves the widest bandwidth phased array enabling the construction of multistandard systems.

A Planar Four-Element UWB Antenna Array with Stripline Feeding Network

This paper proposes a four-element ultrawideband (UWB) planar antenna array with elliptical-shaped radiators and a stripline excitation network designed for the 6–8.5 GHz UWB frequency band allowed in Europe by the European Commission. The designed antenna array has a symmetrical structure in which the radiators are placed along one line in the central conducting layer, arranged between two layers of a dielectric. Radiating elements are fed by the stripline excitation network that provides uniform power distribution. The dimensions of the elliptical radiators’ axes are 14 mm × 16 mm. Two variants of array are proposed. The distance between the radiators’ centers is L = 19 mm for a shorter variant and L = 24 mm for a longer one. The presented antenna array structures have a size of 81 mm × 41 mm and 96 mm × 41 mm. These arrays present a measured gain of 6.4–10.6 dBi for the shorter variant and 8.5–10.8 dBi for the longer one and a fair impedance matching. The measured |S11| is less than −8.7 dB and −9.7 dB for the shorter and longer corresponding variants.

Dual-Polarized Keratin-Based UWB Chipless RFID Relative Humidity Sensor

In this paper, we realize a non-invasive, bio-compatible, reliable and compact sensor to measure relative humidity (RH) levels by depositing keratin bio-polymer on a dual-polarized ultra wide band (UWB) chipless radio frequency identification (RFID) tag. The bio-compatible and hydrophilic properties of keratin make the proposed sensor an appropriate solution for monitoring RH level in different food and pharmaceutical industries, where non-toxic materials are in high demand. The proposed sensor comprises two main parts: a three-armed Fermat spiral resonator and the keratin bio-polymer mounted on the surface of the resonator. Keratin is extracted through the alkaline hydrolysis process and analyzed using X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) methods. The three-armed Fermat spiral resonator acts as a scatterer, generating both co- and cross-polarized resonant responses when interrogated by a signal in a UWB frequency range. Having a cross-polarized response increases the robustness of the proposed sensor in the presence of interference and helps enhance the reliability of the sensor by offering three additional parameters. Amplitude, quality factor, and resonant frequencies are three main parameters that have been extracted from the responses of the proposed RH sensor at both co- and cross-polarization by modelling its responses as a function of frequency. To examine the performance of the sensor, laboratory measurements are carried out in the Esky box. The results show that the proposed sensor can be used to monitor RH changes from 54% to 74% at 26° Celsius.

On the effect of S-parameter stability of antenna and coupler on electrical balance duplexing

Electrical Balance Duplexers (EBDs) provide transmit-receive isolation to implement a form of self-interference cancellation to facilitate simultaneous transmission and reception from a single antenna in systems like In-Band Full-duplex (IBFD) transceivers. EBD works by coupling transmitter, receiver, antenna, and balancing impedance using a hybrid coupler. In recent pieces of literature, antenna impedance variations are considered the main factor limiting the EBD isolation bandwidth, while the EBD balancing impedance needs to be equal as much as possible to the antenna impedance to achieve high isolation. But hybrid couplers are also not ideal elements, and their S-parameters are not stable in the frequency domain. In this work, five broadband RF devices (two antennas, two couplers, and a 50-Ohm RF-load) are used to form four EBD set-ups. One of the antennas, designed by the authors, has more impedance stability in the frequency domain than the other one, which is a commercial antenna. Also, one of the couplers, designed by the authors, has more S-parameter stability in Ultra-Wideband (UWB) frequency domain than the other one, which is a commercial UWB coupler. The implemented EBDs show that when both antenna and coupler have strong S-parameter stabilities in the frequency domain, wider isolation bandwidth (UWB 1.5–3.5 GHz range) and higher EBD isolation are obtained.

A 0.023–12 GHz ultra-wideband frequency synthesizer with FOMT of −251.8 dB

A fully integrated ultra-wideband fractional-N frequency synthesizer is presented in this paper. Ultra-wideband quadrature signals can be generated by an octave-wide fractional-N phase-locked loop (PLL) and an ultra-wideband local oscillator (LO) signal generator. An optimized dual-core voltage-controlled oscillator (VCO) is employed to maintain relatively constant loop parameters in the octave-wide operating range, while a negative-capacitance VCO (NC–VCO) is proposed to solve the frequency gap problem and enhance the design freedom of the wideband VCO. Moreover, a wide-range programmable multi-modulus divider (PMMD) with seamless switching and fractional division resolution is proposed for error-free division operation and quantization noise compensation in the fractional-N mode, respectively. Power-efficient design is mainly achieved by the presented hybrid LO generator with optimized divider topologies for different frequency ranges. Fabricated in a 55 nm CMOS process, 0.023–12 GHz continuous quadrature LO signals can be generated by the proposed frequency synthesizer which occupies an active area of 0.55 mm2 and consumes 75–104 mW from a 1.2 V supply. The measured phase noise is −108.1 dBc/Hz at 1 MHz offset from a 12 GHz carrier, and the I/Q phase error is less than 2.7° with FOMT of −251.8 dB.

A Highly Miniaturized Ultra-Wideband Antenna with a Triple-Band Notch for Wearable Applications

In this paper, a compact UWB antenna with a triple-band notch for wearable applications is designed and simulated for Ultra-Wideband (UWB) applications with the operating frequency from 3.1GHz to 10.6GHz. The antenna can be used for UWB applications, while at the same time, is able to reject the narrowbands namely, WiMAX (3.2GHz to 3.6GHz), C-band (3.7GHz to 4.2GHz) and WLAN (5.15 GHz to 5.35GHz). Two slots are introduced on the radiating patch of the antenna to notch the three narrowbands, instead of three slots to notch each narrowband. The antenna is designed on a semi-flexible Rogers Duroid RO3003TM substrate. The final outcomes indicate that the antenna can operate over the UWB frequency from 3.09 GHz to 11.09GHz. The antenna is able to notch the WiMAX and C-bands with a frequency range from 3.16GHz to 4.20 GHz and the WLAN band with a frequency range from 5.14 GHz to 5.34GHz. The performance of the antenna in bending condition is also examined with the antenna bent over a varying diameter of vacuum cylinder starting from 50mm, 80mm and 100mm. It is shown from the reflection coefficient of each diameter that the performance of the antenna is not affected by bending and thus, is particularly useful to be worn on body for wearable applications, other than its compact size of 19mm×14mm. The SAR results obtained shows that the antenna obeys the guidelines for 1mW of input power.

8-Port MIMO Antenna Having Two Notched Bands for Chipless UWB-RFID Tags

An 8-element Multiple Input Multiple Output (MIMO) antenna is implemented for Chipless-RFID Tags (CRT) that function in the Ultra-Wideband (UWB) frequency range. The single UWB antenna contains a rectangular radiator in which two ellipses are cut from the two lower corners. Also, two circles are etched from the upper corners of the ground. This antenna is designed by placing eight antenna elements at 45&#x2218; direction (clockwise and anticlockwise) and a thin line-shaped decoupling structure is used to enhance isolation at lower frequencies. Also, a T-shaped structure is used to enhance the notched band characteristics. The working frequency of the antenna is from 3.5 GHz to 10.5 GHz with WiMAX and WLAN notched bands using U-slot and Split Ring Resonator (SSR) metamaterial, respectively. The antenna obtains a peak gain of 5 dB (single element). This antenna has radiation efficiency from 76.4% to 92.7%. This antenna design will inspire the designers of chipless RFID (CRFID) to produce low-cost tags.