Entire Frequency Band Research Articles

Wideband dual-polarized all-metal cross-dipole antenna with feeding column

A wideband dual-polarized all-metal dipole antenna with a novel feeding structure was proposed in this paper. The antenna mainly consists of five parts, which are metal dipole, feeding column, cross feeding sheet, coaxial line and ground plane. A new type of feeding column is introduced between the feeding coaxial and the dipole, which can improve the impedance performance of the antenna at high frequency range. To verify the design, the antenna unit was processed with the size of 0.47λ0 × 0.47λ0 × 0.31λ0. where λ0 is the wavelength of the middle frequency. From the measured results, the antenna achieves a relative bandwidth of 83.5% (3–7.3 GHz) with a reflection coefficient < -10 dB, and the port isolation is greater than 30 dB in the entire frequency band. At the same time, the measured gain of the antenna is 6–9 dBi, the antenna pattern is stable over the entire frequency bandwidth. In addition, the proposed dipole sheet is fixed on a feeding column and is therefore more suitable for working in the C-band or even higher X-band. The antenna adopts an all-metal structure, which is not only suitable for high-power applications, but also more suitable for applications under severe conditions such as strong vibration, high and low temperature.

A circular monopole antenna with uniquely packed quad T-shaped strips for WLAN/WiMAX application

Abstract This paper presents a circular monopole antenna with uniquely packed quad T-shaped strips etched on FR4 epoxy substrate having material permittivity 4.4, loss tangent 0.02, and thickness 1.6 mm. The 3.5 GHz band is achieved through this arrangement, which has return loss less than −10 dB while maintaining VSWR &lt;2. It provides a peak gain of 2.65 dBi at 3.5 GHz and average gain of 2.52 dBi in the entire operating frequency band. The radiation pattern is almost omnidirectional in E plane and bidirectional in H plane. The proposed antenna has a compact size of 41.25 mm × 30.55 mm. The simulated results of S11 parameters, gain, VSWR, radiation pattern, and efficiency are studied and verified with the measured results of fabricated antenna as well as its equivalent lumped circuit model. Investigation shows that the proposed antenna can be employed for WLAN/WiMAX applications efficiently.

High gain miniaturrized super‐wideband microstrip patch antenna

SummaryA miniaturized super‐wideband (SWB) monopole antenna is presented in this work. Electrical dimension of the presented antenna is 0.239λ × 0.239λ × 0.0147λ, where λ indicates the wavelength corresponding to the lowest operating frequency. Presented antenna displays single −10 dB operating band from 2.75 to 28 GHz with 164% percentage bandwidth and bandwidth ratio of more than 10:1. The proposed SWB antenna exhibits a large bandwidth dimension ratio (BDR) of 2871 with realized gain of 4.80 dBi. Radiating patch of the proposed antenna is designed by modifying conventional rectangular patch by loading a matching stepwise structure. Further, in order to achieve SWB characteristics, the ground plane is reduced with a loaded rectangular notch for better impedance matching. The designed antenna has the advantages of simple planar miniaturized structure, acceptable gain, and wide bandwidth to support various objectives in modern wireless communication. To boost the maximum gain further over the entire frequency band, the proposed antenna is combined with the proposed frequency selective surface (FSS) which acts as a partially reflector surface. The antenna is placed over 4 × 4 FSS at suitable distance without hampering the obtained bandwidth of the antenna. FSS combined antenna structure, having the physical volume of 56 mm × 56 mm × 26.2 mm, exhibits realized gain of 9.3 dBi which is suitable for long range communication. CST MWS (Microwave studio) for simulation results of the suggested antenna and appropriate Microwave Test bench is used to verify the same.

Y- shaped dielectric resonator MIMO antenna for omnidirection radiation pattern

ABSTRACT A three-port Y-shaped DRA multiple-input-multiple-output (MIMO) antenna is proposed for prospective 5 G applications. Three Rectangular DRA form a Y-shaped DRA placed on the circular ground (r = 50 mm). Each element of the DRA is fed by conformal microstrip line which generates TE11δ and TE12δ transverse modes. The symmetricity of the structure is maintained by locating three arms of DRA at a separation of 120°, which generates three-directional patterns at 0°, 120°, and 240° and offers good diversity. Antenna offers 3.7–7.19 GHz measured impedance bandwidth and isolation below −10 dB between all ports over the entire operating frequency band. 8 dBi peak gain is obtained at 5.75 GHz frequency.

A Compact Sub-GHz Wide Tunable Antenna Design for IoT Applications

This work presents a compact meandered loop slot-line 5G antenna for Internet of Things (IoT) applications. Recently, sub-gigahertz (sub-GHz) IoT technology is widely spreading. It enables long-range communications with low power consumption. The proposed antenna structure is optimized to operate at sub-GHz bands without any additional complex biasing circuitry or antenna structure. A miniaturized design was achieved by a meandered structured loop slot-line that is loaded reactively with a varactor diode. Wideband frequency reconfigurability (FR) was achieved by the use of the varactor diode. The proposed antenna resonates over the frequency band of 758–1034 MHz with a minimum bandwidth of 17 MHz over the entire frequency band. The RO4350 substrate with dimensions of 0.18λg × 0.13λg mm2 is used to design the proposed antenna design. The efficiency and gain values varied from 54–67% and 0.86–1.8 dBi. Compact planar structure, narrow-band operation (suitable for NB-IoT) and simple biasing circuitry, which allows for sub-GHz operation, are unique and attractive features of the design.

The application of a novel perfectly matched layer in magnetotelluric simulations

Truncation boundaries are needed when simulating a region in magnetotelluric (MT) modeling. As an efficient alternative truncation boundary, perfectly matched layers (PMLs) have been widely applied in many high-frequency wavefield simulations. However, the governing equation of most electromagnetic exploration methods is for the diffusion field, in which the conduction current is significantly greater than the displacement current. Because the wave and diffusion fields have completely different relations for the frequency and constitutive parameters, conventional PMLs, which are mainly designed for the wavefield, are not a good choice for the diffusion field. For this reason, we propose a formula for a PML that covers the entire frequency band, including the wave and the diffusion fields. It is based on a uniaxial PML. Moreover, we derive a simplified form for the diffusion field. To check the feasibility and application potential of the proposed formula for a PML in MT simulations, we have implemented PMLs using a finite-element method and compared our results with those for a conventional long-distance extended grid. The results of the 1D simulation demonstrate that PMLs can achieve high accuracy and stable performance and have a broad application range. In 2D and 3D models, the air layer is an obstacle in the application of a PML. By selecting appropriate parameters for the PML, 2D and 3D models can achieve satisfactory performance. Therefore, the proposed PML is useful for MT simulations and can achieve satisfactory truncation performance.

Self‐decoupled tapered slot antenna using defected radiator structure

A self-decoupled tapered slot antenna (TSA) by rejecting the coupling wave is proposed in this paper. Such TSA arrays have high isolation without introducing additional decoupling structures. And compared with the reference TSA, the self-decoupled TSA is obtained by the defected radiator structure, which is etched with multiple continuous cross grooves on the two fins of TSA. The reason why the defected radiator structure can be decoupled is that it has a band-stop characteristic within the operating frequency band of the TSA. The TSA with and without the defected radiator structure is studied that the TSA with defected radiator structure achieves ultra-wideband decoupling from 3 to 11 GHz. Moreover, the gain of the self-decoupled TSA is improved at most frequencies. A prototype of the self-decoupled TSA and the reference TSA are fabricated and measured. An excellent agreement between simulated and measured results is obtained. The isolation level of the self-decoupled TSA improves by a maximum of 12 dB at 6 GHz. The mutual coupling is reduced by 1 to 12 dB over the entire operating frequency band. In addition, the peak gain of the self-decoupled TSA is improved by up to 1.5 dBi.

A thin shared radiator based ACS‐fed orthogonal pattern diversity antenna with physical tilt for mmWave 5G access points

A low profile and compact two-port antenna is proposed for mmWave 5G access point applications. Since the overall space inside a typical mmWave 5G access point is limited, a small form factor based antenna module is proposed. The two-port antenna shares a common radiator that miniaturizes the overall antenna module. The proposed antenna comprises of single-layered asymmetric coplanar strip (ACS)-fed shared radiator with wide operating bandwidth ranging from 25 to 31 GHz that accounts for fractional bandwidth of 21.4%. The two-port antenna elements are oriented at right angles to each other for obtaining orthogonal pattern diversity (OPD) thereby obtaining wide angular coverage in the E-plane. Vertical linear corrugations with varying lengths are incorporated for decreasing mutual coupling between these two antenna elements and producing a uniform high gain end-fire radiation pattern. Isolation of around 4 dB is enhanced by insertion of these vertical corrugations. The proposed antenna attains peak gain of 7.2 dBi with high pattern integrity over the entire operational frequency band. The presented OPD antenna occupies overall area of 74.75 mm2 which is minimal. Moreover, implementation of the proposed antenna inside a typical mmWave 5G access point is also demonstrated. Simulation and measured results are presented with adequate technical explanation.

Design and Analysis of a Compact Frequency Beam-Scanning Antenna Based on Composite FHMSIW/SSPP Waveguide

In this letter, a novel compact frequency beam-scanning antenna (FBSA) using composite waveguide based on folded half-mode substrate integrated waveguide (FHMSIW) and spoof surface plasmon polaritons (SSPP) is proposed. The novel composite FHMSIW/SSPP waveguide with compact size and high field-confinement is initiated by embedding dual SSPP structures into the FHMSIW. Its transmission characteristic has flexible features from both the FHMSIW and SSPP. To excite the radiation mode from the composite slow-wave waveguide, a simple single-sided sinusoidal modulation method is designed and used. In this way, the common open stop-band problem around broadside is effectively eliminated, and the beam-scanning range of the antenna can be flexibly designed without changing the modulation structure. The presented scanning antenna owns a compact size and a simple feeding network. The experimental results indicate that the proposed FBSA can achieve continuous beam scanning from backward to forward in a wide scanning range of 60° within a bandwidth of 7.7–10.1 GHz. The stable unidirectional radiation patterns and appropriate gains are also realized in the entire operating frequency band.

Broadband Millimeter-Wave 5G Power Amplifier Design in 22 nm CMOS FD-SOI and 40 nm GaN HEMT

Three millimeter-wave (mm-Wave) power amplifiers (PAs) that cover the key 5G FR2 band of 24.25 to 43.5 GHz are designed in two different state-of-the-art device technologies and are presented in this work. First, a single-ended broadband PA that employs a third-order input matching network is designed in a 40 nm GaN/SiC HEMT (High Electron Mobility Transistor) technology. Good agreement between the measurement and post-layout parasitic extracted (PEX) electromagnetic (EM) simulation data is observed, and it achieves a measured 3-dB BW (bandwidth) of 18.0–40.3 GHz and &gt;20% maximum PAE (power-added-efficiency) across the entire 20–44 GHz band. Expanding upon this measured design, a differential broadband GaN PA that utilizes neutralization capacitors is designed, laid out, and EM simulated. Simulation results indicate that this PA achieves 3-dB BW 20.1–44.3 GHz and maximum PAE &gt; 23% across this range. Finally, a broadband mm-Wave differential CMOS PA using a cascode topology with RC feedback and neutralization capacitors is designed in a 22 nm FD-SOI (fully depleted silicon-on-insulator) CMOS technology. This PA achieves an outstanding measured 3-dB BW of 19.1–46.5 GHz and &gt;12.5% maximum PAE across the entire frequency band. This CMOS PA as well as the single-ended GaN PA are tested with 256-QAM-modulated 5G NR signals with an instantaneous signal BW of 50/100/400/9 × 100 MHz at a PAPR (peak-to-average-power ratio) of 8 dB. The data exhibit impressive linearity vs. POUT trade-off and useful insights on CMOS vs. GaN PA linearity degradation against an increasing BW for potential mm-Wave 5G applications.

Design of a novel ultra‐wideband dual‐polarized printed planar antenna

A novel antenna, which has a simple one-layer printed planar structure with dual-polarization and ultra-wideband (UWB) properties, is proposed in this article. The proposed antenna consists of a pair of crossed dipoles, two stacked square loops, four meander slots, and a hornlike reflecting cavity. The stacked loops positioned around the crossed dipoles are utilized to introduce a new resonant mode in the lower frequency band, which essentially widens the impedance bandwidth and realizes the miniaturization design. To further enhance the impedance bandwidth, the four meander slots are cut from the crossed dipoles to generate a new resonant mode in the higher frequency band. Therefore, the impedance bandwidth is greatly expanded. A hornlike reflecting cavity is used to enhance the unidirectional radiation pattern over the operating frequency band. A prototype is designed, fabricated, and measured. Measured results show that the proposed antenna achieves a voltage standing wave ratio (VSWR) < 2, impedance bandwidth up to 92% (from 1.05 to 2.85 GHz). The isolation between two linear orthogonal polarizations >25 dB, and stable unidirectional radiation patterns over the entire working frequency band with gain >8 dBi. Furthermore, the proposed antenna has a compact planar size of 0.25 λ L × 0.25 λ L ( λ L is the longest operating wavelength).

Design of a Broadband MMIC Driver Amplifier with Enhanced Feedback and Temperature Compensation Technique

This paper presents a broadband GaN pseudo high-electron-mobility transistor (pHEMT) two-stage driver amplifier based on an enhanced feedback technique for a wideband system. Through well-designed parameter values of the feedback and the matching structure of the circuit, a relatively flat frequency response was obtained over a wide frequency band. Simultaneously, in order to reduce the fluctuation of current caused by the environmental temperature, a bias circuit with quiescent current temperature compensation was designed. The driver power amplifier, which was implemented in the form of a monolithic microwave integrated circuit (MMIC), was designed to drive a broadband high-power amplifier. The designed broadband driver amplifier for the 6 GHz to 20 GHz frequency band had a very small die size of 1.5 × 1.2 mm2 due to the use of an optimized impedance matching structure. It exhibited a small-signal gain of 12.5 dB and output power of 26 dBm. The flatness of this driver amplifier for gain and output power was achieved as ±2.5 dB and ±1 dB over the entire frequency band, respectively. The experimental results showed up to 35 dBm in the OIP3, and the current variation range was ±5 mA after using the temperature compensation bias circuit.

Nondispersive One-Way Signal Amplification in Sonic Metamaterials

Parametric amplification---injecting energy into waves via periodic modulation of system parameters---is typically restricted to specific multiples of the modulation frequency. However, broadband parametric amplification can be achieved in active metamaterials which allow local parameters to be modulated both in space and in time. Inspired by the concept of luminal metamaterials in optics, we describe a mechanism for one-way amplification of sound waves across an entire frequency band using spacetime-periodic modulation of local stiffnesses in the form of a traveling wave. When the speed of the modulation wave approaches that of the speed of sound in the metamaterial---a regime called the sonic limit---nearly all modes in the forward-propagating acoustic band are amplified, whereas no amplification occurs in the reverse-propagating band. To eliminate divergences that are inherent to the sonic limit in continuum materials, we use an exact Floquet-Bloch approach to compute the dynamic excitation bands of discrete periodic systems. We find wide ranges of parameters for which the amplification is nearly uniform across the lowest-frequency band, enabling amplification of wave packets while preserving their speed, shape, and spectral content. Our mechanism provides a route to designing acoustic metamaterials which can propagate wave pulses without losses or distortion across a wide range of frequencies.

Hybrid Decoupling Structure Based on Neutralization and Partition Schemes for Compact Large-Scale Base Station Arrays

This letter proposes a hybrid decoupling structure consisting of a neutralization dielectric board, metal baffle, and feeding network to enhance the isolation in a compact large-scale base station array. Both the neutralization- and partition-based schemes are utilized to reduce the mutual coupling between antennas. The neutralization dielectric board provides a new signal path to cancel the original mutual coupling, and the metal baffle is employed to suppress the propagation of the space electromagnetic wave. The antenna elements in the vertical direction are excited by a feeding network. A 4×4 dual-polarized antenna array with a horizontal edge-to-edge distance of 0.38 free-space wavelength is designed and fabricated to demonstrate the effectiveness of the proposed structure for large-scale arrays for base station application. Simulated and measured results show that the voltage standing wave ratio is less than 1.7, and the isolation between any two ports in the array is better than 20 dB within the entire operating frequency band. Stable radiation patterns with a good front-to-back ratio and cross-polarization ratio are achieved.

Wideband Monostatic Co-Horizontally Polarized Simultaneous Transmit and Receive Antenna Subsystem With Integrated Beamforming Network

A wideband monostatic simultaneous transmit and receive (STAR) antenna subsystem with high isolation and Co-horizontally polarized (Co-HP) omnidirectional radiation is presented. The antenna subsystem consists of a STAR antenna and a beamforming network (BFN). The STAR antenna consists of a planar circular array having four printed dipole elements surrounded by two groups of parasitic strips. The parasitic strips are used to improve the impedance bandwidth (IMBW) and reduce the gain variation in transmit (TX) and receive (RX) modes. To achieve high isolation, the four ports of the STAR antenna are excited with two orthogonal phase modes for TX and RX using the BFN. The BFN is a six-port network consisting of two 180&#x00B0; hybrid couplers, one 90&#x00B0; hybrid coupler, and a Wilkinson power divider. The 180&#x00B0; hybrid coupler is elaborately designed with low imbalances since it is most key to achieve high TX/RX isolation. Measured results show that the proposed STAR subsystem achieves a TX/RX overlapping IMBW of 4.71&#x2013;6.2 GHz, and a 40 dB TX/RX isolation bandwidth of 4.81&#x2013;5.88 GHz, while maintaining horizontally polarized omnidirectional radiation patterns for TX and RX over the entire operating frequency band.

A Miniaturized Wideband Dual-Polarized Planar Antenna Based on Multiresonance

In this letter, a miniaturized wideband dual-polarized antenna with a simple structure is proposed. The proposed antenna includes two stacked square loops, which are positioned around the cross-dipole, these loops are utilized to introduce a new resonant mode at a relatively low frequency band, which essentially widens the impedance bandwidth and realizes the miniaturization design. It also includes metallic plates that are vertically positioned on the reflector. These parasitic vertical metallic plates, operating in coincidence with the coupling energy from the nearby radiators, serve to generate an additional resonant mode outside the original impedance passband of the cross-dipole antenna. This enables further expansion of the impedance bandwidth. A prototype was fabricated and tested, where the measured results demonstrated that the proposed antenna ability to achieve a wide impedance bandwidth, i.e., up to 91% (0.98 to 2.6 GHz) with VSWR <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ &lt; $</tex-math></inline-formula> 2. Additionally, the isolation between the two linear orthogonal polarizations was greater than 20 dB. The unidirectional radiation patterns are stable over the entire operating frequency band, with an average gain of 7.5 dBi. Furthermore, the overall size of the proposed antenna is very compact, amounting to only approximately <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\ 0.36\;{{\mathrm{\lambda }}_{\mathrm{L}}} \times 0.36\; {{\mathrm{\lambda }}_{\mathrm{L}}} \times 0.13\; {{\mathrm{\lambda }}_{\mathrm{L}}}$</tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\mathrm{\lambda }}_{\mathrm{L}}}$</tex-math></inline-formula> is the longest operating wavelength.

An ultra‐wideband 3 × 3 Butler matrix with unique Vivaldi array structure for high‐range resolution radars

Steerable antenna beam capability is an outstanding expectation for the development of automatic tracking systems and target detection. A switched beam array antenna, which can generate multiple fixed beams with enhanced sensitivity, emerges as a solution for beamforming tracking. On the other hand, it is known that the target can be detected with high-range resolution thanks to ultra-wideband (UWB) systems. In this work, a compact switched beam Vivaldi array antenna based on a Butler matrix for a UWB application capable of target detection with accurate target tracking is presented to meet the high gain and low side lobe level requirements. Based on a three-element antenna array, two methods have been applied to obtain small grating lobes and it has been shown that significant improvements can be achieved. Designed with a 3 × 3 UWB Butler matrix, the UWB array antenna can direct its beams in three directions in a direction range from −42 to 42°. The measured result showed that the group delay was less than about 4.5 ns with variation of less than ±0.7 ns over the entire operating frequency band.

Adaptive broadband frequency invariant beamforming using nulling-broadening and frequency constraints

The performance of conventional adaptive broadband beamforming algorithms is degraded because of rapidly moving interferences and look-direction errors. In this paper, a number of techniques are proposed to overcome this issue. By proposing an adaptive frequency invariant beamformer (FIB) that uses frequency constraints, we can obtain undistorted responses to broadband signal of interests (SOIs) and constant beamwidths over an entire frequency band without pre-steering delays. And the influence of look-direction errors can also be receded. Furthermore, a singular value decomposition of the frequency constraints is added to the proposed algorithm in view of releasing numerous degrees of freedom (DOFs), as this approach can simultaneously maintain the enhanced anti-interference performance and hold the undistorted response to SOIs. Finally, the nulling-broadening method involving the use of virtual interferences is adopted to construct a taper matrix and ensure robust performance versus rapidly moving interferences. This robust response to rapidly moving interferences and look-direction errors allows the proposed algorithm to achieve satisfactory broadband beamforming performance. Simulation results highlight the correctness and effectiveness of the proposed methods.

A vehicle‐mounted high power LPDA design for 8‐22 MHz applications

AbstractThe design of high‐power vehicle‐mounted log periodic dipole antenna for 8‐22 MHz use was discussed. It is shown that the antenna has a power endurance of 150 kW. With the application of the coefficients variation method, the total size of the proposal was shrunk to 12 × 18 m so that it can be mounted on a vehicle of 10 m long by an elevation tower. The voltage standing wave ratio over the entire frequency band is lower than 2.0 without utilizing any match network.

A compact and miniaturized implantable antenna for ISM band in wireless cardiac pacemaker system

A tiny and compact implantable antenna for wireless cardiac pacemaker systems is designed. The antenna works in the Industrial Scientific Medical (ISM) frequency band (2.4–2.48 GHz). The size of the antenna is greatly reduced with the adoption of a high dielectric constant medium and a folded meander structure. The volume of the antenna is 4.5 mm3, and the size is only 3 mm × 3 mm × 0.5 mm. Based on the literature research, it was found that the design was the smallest among the same type of implanted antenna. The antenna is optimized and loaded with a defective slotted structure, which improves the efficiency of the overall performance of the antenna and thus the gain thereof. The antenna maintains good impedance matching in the ISM frequency band, covering the entire ISM frequency band. The actual bandwidth of the antenna is 22%, with the peak gain of − 24.9 dBi. The antenna is processed and manufactured in such a manner that the simulation keeps consistent with the actual measurement. In addition, the specific absorption rate of the antenna is also evaluated and analyzed. The result shows that this kind of antenna is the best choice to realize the wireless biological telemetry communication in the extremely compact space of the wireless cardiac pacemaker system.