Ultrawideband Radiation Research Articles

A large-aperture, high-power ultrawideband radiation system with beam broadening capacity.

Due to the limited maximum output power of the pulsers based on avalanche transistors, high-power ultrawideband (UWB) radiation systems usually synthesize plenty of modules simultaneously to achieve a high peak effective potential (rEp). However, this would lead to an increased aperture size as well as a narrower beam, which would limit their applications in intentional electromagnetic interference fields. In this paper, a high-power UWB radiation system with beam broadening capacity is developed. To achieve beam broadening in the time domain, a power-law time delay distribution method is proposed and studied by simulation, and then the relative excitation time delays of the modules are optimized to achieve higher rEp and avoid beam splitting in the beam broadening mode. In order to avoid false triggering of the pulser elements when implementing the beam broadening, the mutual coupling effect in the system is analyzed and suppressed by employing onboard high-pass filters, since the mutual coupling effect is much more severe in the low-frequency range. Finally, a radiation system with 36 modules is developed. Measuring results indicate that in the high-rEp mode, the developed system could achieve a maximum effective potential rEp of 313.6kV and a maximum pulse-repetition-rate of 20kHz. In the beam broadening mode, its half-peak-power beam width in the H-plane is broadened from the original value of 3.9° to 7.9°, with a maximum rEp of 272.9kV. The polarization direction of the system could be flexibly adjusted by a built-in motor.

Pulse Radiation Characteristics Prediction Method of Vivaldi Antenna based on Dipole Array

This paper presents a theoretical method to estimate the pulse radiation characteristics of Vivaldi antennas. Based on the surface current distribution and the ultra-wideband radiation principle, Vivaldi antenna is equivalently modeled as a dipole array, and the pulse radiation characteristics of a single Vivaldi antenna are brought out utilizing the spatial superposition approach. Then, the influences and results of the Vivaldi antenna pulse characteristics prediction with different construction ways of the dipole array and element numbers are furthermore investigated. Next, a quadratic spatial superposition technique is employed to complete the theoretical prediction for time-domain radiation characteristics of Vivaldi antenna arrays. Experiments and simulations are conducted separately to verify the proposed method for both single Vivaldi antenna and array. The validated results demonstrate that the dipole array-based theoretical prediction method can effectively capture the pulse radiation characteristics for both individual Vivaldi antenna and array operating in different modes, thereby addressing challenges associated with estimating radiation characteristics in ultra-wideband pulse applications.

A High-Power Source of Ultrawideband Radiation of Subnanosecond Duration with Controllable Characteristics

A High-Power Source of Ultrawideband Radiation of Subnanosecond Duration with Controllable Characteristics

Design of dipole array MIMO antenna for multiband and ultrawideband radiation applications in WiFi/Zigbee/WiMAX/satellite and mobile communications

Design of dipole array MIMO antenna for multiband and ultrawideband radiation applications in WiFi/Zigbee/WiMAX/satellite and mobile communications

SYNCHRONIZED ACTIVE ANTENNA ARRAYS FOR STUDYING THE PASSAGE OF ULTRA-WIDEBAND SIGNALS IN THE ATMOSPHERE AND IONOSPHERE

Active synchronized antenna arrays generating ultra-wideband radiation with an electric field strength of about 1 V/m at a distance of several hundred kilometers have been studied. They are designed to study the passage of ultra-wideband signals in the surface layer of the atmosphere and through ionosphere. Synchronous antenna arrays with 4 and 9 radiating modules have been created. Their radiation has a symmetrical radiation pattern along the X and Y axes with a pulse duration at half-height of about 100 ps. They have a pulse energy potential (E × R) of about 60 and 150 kV, with a gross weight of 50 and 100 kg, respectively. Such characteristics allow these arrays to be placed on air carriers. The option of using air balloons when radiating in the surface layer of the atmosphere and the option of the meteorological rockets placing when radiating from a height of 300 km to the Earth surface is considered.

Integrated Narrow Band (NB) and UWB MIMO Antenna for IoT Applications

In this work, we integrated narrow band (NB) and Ultra-Wide Band (UWB) four-port MIMO antennas designed and implemented in IoT applications. The designed antenna consists of two quarter-wavelength asymmetrical NB radiators and a reverse P-shaped UWB radiator. The two NBs are generated by two quarter-wavelength non-identical radiators, and the UWB is generated by a semi-circle-shaped monopole radiator. Further, the NB radiators and UWB radiators are connected in a 3-mm-wide feed line. The antenna is designed to operate at 1.8 GHz (3G), 2.4 GHz (WLAN), and 3.1–12 GHz (UWB) for IoT applications. In this designed four-port MIMO antenna, two proposed NB and UWB radiators are mounted on the front side of the FR4 substrate and the other two on the rear side of the FR4 substrate. The proposed MIMO antenna has a dimension of 65 × 65 × 1.6 mm 3 . The antenna performance and MIMO performance are analyzed. The diversity metrics such as ECC, DG, TARC, MEG, and CCL are computed, and their values are 0.26, 9.87 dB, −22 dB, −6 dB, and 0.27 bits/Hz/s, respectively, within the bounds. The real-time implementation of the designed antenna is demonstrated at 2.4 GHz for smart home applications.

DIRECT EXPERIMENT ON THE PASSAGE OF ULTRA-WIDEBAND PULSES OF SUBNANOSECOND DURATION IN THE EARTH’S ATMOSPHERE

The results of the first direct experiments on the passage of pulses of ultra-wideband radiation of subnanosecond duration in the Earth’s atmosphere at a distance of more than 10 km are presented. In contrast to the calculated work, the preservation of the amplitude-time shape of the pulses in the process of increasing the distance is shown. The establishment of this fact is of decisive importance in the practical application of ultra-wideband pulses in new technological developments.

High power balanced TEM horn antenna for ultra wide band radiator

AbstractA balanced transverse electromagnetic (TEM) horn type antenna is designed and developed for a 120 kV, 66 Ω high power ultra wideband (UWB) radiator. This antenna consists of a coaxial to parallel plate unzipper BALUN followed by an exponentially tapered TEM horn structure. Analysis of this antenna in time and frequency domain is performed using CST Microwave Studio. This antenna is having a power handling capacity of 1000 MW, with percentage bandwidth of 167%. This antenna has a gain of ~10 dB at 1 GHz frequency. Return loss performance of better than −10 dB is observed in 150 MHz to 1 GHz frequency range. Effective radiation of short pulses (<5 ns) with very fast rise time (300–500 ps) has been demonstrated using this high‐power antenna. Practical results at 220 MW power are presented in this article. Directional performance of this antenna is practically established through peak power patterns in horizontal and vertical plane.

Amplitude–Temporal and Spectral Characteristics of Pulsed UHF-SHF Radiation of a High-Voltage Streamer Discharge in Air under the Atmospheric Pressure

A special experimental setup with a three-electrode discharge gap was used to study the dynamic characteristics of the ultra-high- and super-high-frequency (UHF-SHF) electromagnetic radiation of a high-voltage discharge having the streamer form with reference to the dynamics of individual streamers at the nanosecond time resolution. We performed synchronous detection of the radiation waveforms using a wideband horn antenna, on the one hand, and high-speed photography of the discharge development in the discharge gap using an ICCD camera, on the other hand. It was found that the high-voltage discharge is a source of radiation in the frequency band up to 10 GHz, which is a series of individual ultrawideband (UWB) bursts having durations of less than 1 ns and leading fronts less than 100 ps long and appears when the streamers moving from the discharge anode (thin wire) meet the discharge cathode (plane). By the order of magnitude, the number of radiation bursts corresponds to the number of streamers that reach the electrode, according to the high-speed photography data. The qualitative data confirmed by simple theoretical estimations show that the sources of UWB radiation pulses are individual streamers at the moment of their contact with the electrode, and the radiation of the streamers can be regarded as transition radiation.

A novel Vivaldi antenna for UWB detection

AbstractThis paper presents a modified structure of the Vivaldi antenna based on an FR4 dielectric substrate of 0.8 mm thickness and 110 mm × 96 mm dimensions for ultra‐wideband (UWB) detection systems. The modified Vivaldi antenna has two major novelties. (1) Bottle‐shaped slots are etched on both sides of the classic Vivaldi antenna to extend the surface current path length and concentrate electromagnetic energy. (2) Rectangular metal strips are implemented in front of the exponential slot to guide the UWB radiation waveform in the desired direction. The modified Vivaldi antenna is evaluated using the CST 2020 software and measured using the vector network analyzer ranging from 3 to 8 GHz. The obtained results show that a maximum peak gain of nearly 9 dBi at 4 GHz can be achieved, the radiation efficiency is improved to 80%, the main lobe level is increased, and the side lobe level is decreased. To further demonstrate the performance of the proposed Vivaldi antenna, a UWB imaging experiment is designed. The imaging results show that the imaging system using the proposed antennas can obtain images with good resolution, which indicates that the antenna has good radiation characteristics and can be used for UWB detection applications.

Arrays of combined antennas with equal-amplitude distribution of bipolar voltage pulses

The paper presents the comparative characteristics of the radiation pattern of the combined antenna arrays excited by a bipolar pulse and harmonic oscillations near the central frequency of the spectrum of ultrawideband radiation. Particular attention is paid to the 3x3 array radiation source with maximum efficiency.

An UWB Hemispherical Vivaldi Array

We report the first conformal ultra-wide band (UWB) array on a doubly curved surface for wide angle electronic scanning. We use a quadrilateral mesh as the basis for systematically arraying UWB radiators on arbitrary surfaces. A prototype consisting of a 52 element, dual-polarized Vivaldi array arranged over a 181 mm diameter hemisphere is developed. The antennas and SMP connectors are 3D printed out of titanium to allow for simple fabrication and assembly. We derive the theoretical gain of a hemispherical array based on the antenna size and number of elements. The measured realized gain of the prototype array is within 2 dB of the theoretical value from 2-18 GHz and scan angles out to 120{\deg} from the z-axis. This field of view is twice that of a planar array with the same diameter in agreement with theory. This work provides a baseline performance for larger conformal arrays that have more uniform meshes. Furthermore, the basic concept can be extended to other UWB radiating elements.

A 1.35-kV/500-kHz Sub-Nanosecond Pulser With High Time Base Stability

In many fields, e.g., ground-penetrating radar and ultra-wideband radiation, a high-pulse-repetition-frequency (PRF) and high-time-base-stability sub-nanosecond pulser is required, and its output waveform should be close to a gaussian pulse. In this article, the transistorized pulser is studied and optimized to improve its output parameters. The printed circuit board circuit parameters of the pulser are first optimized, which is beneficial for the amplitude and the rise time. To improve the time base stability, the collector voltage ramp triggering mode is adopted to replace the conventional base triggering mode for the pulser. For higher PRF, the pulser with the capacitance–transistor parallel structure is immersed in the fluorinert liquid. Moreover, the deficit-charge method is adopted, and small charging capacitances are used in the last few stages to weaken the oscillation in the pulse falling edge. From experimental results, the amplitude of the optimized pulser is 1.35 kV, its rise time is reduced from about 200 to 135 ps, the maximum PRF is improved from 250 to 500 kHz, the pulse jitter is reduced to 22 ps, and the pulse drift is reduced from hundreds of ps/min to 47 ps/min. Meanwhile, the oscillation in its falling edge is greatly suppressed.

Double-mode and double-beam staggered double-vane traveling-wave tube with high-power and broadband at terahertz band

In this paper, a 220 GHz broadband and high-power staggered double-vane traveling-wave tube has been designed and verified. Firstly, a planar double-beam staggered double-vane slow-wave structure is proposed. By using the double-mode operation scheme, the transmission performance and bandwidth have been almost increased with twice as the single mode. Second, to satisfy the high output power requirement and improve the stability of the traveling-wave tube, a double pencil-beam electron optical system has been designed, the 20–21 kV driven voltage and the 2 × 80 mA current are set as the design target. By using the mask portion and the control electrode in the double beam gun, the two pencil beams can be focused with a compression ratio of 7 along their respective centers with narrow distances of about 0.18 mm with good stability. The uniform magnetic focusing system has also been optimized. The stable transmission distance of planar double electron beams could reach 45 mm with the focusing magnetic field of 0.6 T, which was long enough to cover the whole high-frequency system (HFS). Then, to verify the availability of the electron optical system and the performance of the slow-wave structure, particle-in-cell (PIC) simulation has also been carried out with the whole HFS. Results demonstrate that the beam-wave interaction system can get a nearly 310 W peak output power at 220 GHz with a 20.6 kV optimized beam voltage and beam current of 2 × 80 mA, the gain is of 38 dB with the 3-dB bandwidth over 35 dB about 70 GHz. Finally, the high precision microstructures fabrication has been carried out to verify the performance of the HFS, the results show that the bandwidth and the transmission properties are in good agreement with simulation result. Thus, the proposed scheme in this paper is expected to develop the high-power and ultra-wideband terahertz band radiation source with potential applications in the future.

A modularized high-power ultra-wideband radiation system based on the space-synthesis method.

In this paper, a high-power ultra-wideband radiation system, composed of multiply radiation modules, is developed based on the space-synthesis method. The radiation module mainly consists of a transistorized pulser, a 2 × 2 combined antenna array, and a power divider. To improve the out parameters [the amplitude, the pulse repetition frequency (PRF), and the rise time] of the transistorized pulser based on the Marx circuit, the influence of the traveling wave process on the output pulse must be concerned. Based on the theoretical analysis, the printed circuit board circuit parameters and the circuit structure of the pulser are optimized. To improve the power synthesis efficiency, the pulse jitter characteristic of the pulser is improved by replacing the conventional base triggering mode with the collector voltage ramp triggering mode for the first-stage avalanche transistor in the pulser. The previous optimized antenna array is utilized in this radiation system, which has a better radiation performance in the prescribed aperture area. In addition, based on the gradient microstrip structure, the power divider integrated with the pulser is designed, which has the advantages of wide bandwidth, low loss, and light weight. Experimental results show that the peak effective potential rEp of the radiation system of 20 radiation modules is 221.8 kV, the maximum PRF could reach 10 kHz, and the half-power radiation angles of its radiation field are about 5° in both the E plane and the H plane. More radiation modules could be integrated into the system to achieve a higher electric field in the future.

Радиофизический метод исследования деформации сверхширокополосных импульсов при распространении в атмосфере

Field experiments have been carried out to measure ultra-wide-band subnanosecond radiation pulses in the time domain, taking into account the influence of reflection from the Earth's surface. Received results allow us to prepare experiments in a free atmosphere on real ranges of 10 kilometers or more in length. The optimal technical solution in terms of weight and size characteristics and elevation to heights up to 1000 meters is the using a single-channel ultra-wideband radiator with a pulse duration of about 50 ps and a specially designed measuring antenna in the form of a passive antenna array with high sensitivity.

Numerically Efficient Miniaturization-Oriented Optimization of an Ultra-Wideband Spline-Parameterized Antenna

Design of ultra-wideband radiators for modern handheld applications is a challenging task that involves not only selection of an appropriate topology, but also its tuning oriented towards balancing the electrical performance and size. In this work, a low-cost design of a compact, broadband, spline-parameterized monopole antenna has been considered. The framework used for the structure design implements trust-region-based methods, space mapping correction mechanisms, and a meta-optimization loop that permits a gradual increase of the problem dimensionality. The optimized structure is characterized by small dimensions of 11.4 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times17.2$ </tex-math></inline-formula> mm and an overall footprint of only 195 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The radiator operates within 3.1 GHz to 12 GHz bandwidth with the reflection coefficient amplitude level of around–10 dB. The computational cost of the structure design amounts to just 163 simulations of the high-fidelity EM model, which is low having in mind that the antenna is represented by a total of 38 adjustable parameters. The optimized radiator has been compared against state-of-the-art structures from the literature. Benchmarking of the presented optimization algorithm has also been performed. Numerical results have been confirmed by measurements of the fabricated antenna prototype.

Radio-physical method for studying the deformation of ultra-wideband pulses during propagation in the atmosphere

Field experiments have been carried out to measure ultra-wide-band subnanosecond radiation pulses in the time domain, taking into account the influence of reflection from the Earth's surface. Received results allow us to prepare experiments in a free atmosphere on real ranges of 10 kilometers or more in length. The optimal technical solution in terms of weight and size characteristics and elevation to heights up to 1000 meters is the using a single-channel ultra-wideband radiator with a pulse duration of about 50 ps and a specially designed measuring antenna in the form of a passive antenna array with high sensitivity. Keywords: ultra-wideband pulses, propagation through atmosphere, reflected signal influence.

ИСПОЛЬЗОВАНИЕ РАДИОЛОКАЦИОННЫХ СИГНАЛОВ С ОРТОГОНАЛЬНЫМИ ПОЛЯРИЗАЦИЯМИ В ЗАДАЧЕ ОБНАРУЖЕНИЯ НАХОДЯЩИХСЯ ЗА ПРЕГРАДОЙ БИОЛОГИЧЕСКИХ ОБЪЕКТОВ

In recent decades, there has been a great interest in the use of ultra-wideband (UWB) radar methods for detecting living biological objects hidden behind various barriers. The wide frequency band of the UWB radiation makes it possible to provide a high penetrating power along with a spatial resolution sufficient to detect oscillations characteristic of the respiration of a living organism. This article considers a model of an ultra-wideband radar for detecting a living biological object located behind an optically-nontransparent obstacle. The considered radar model consists of two channels, each of which has two independent antennas with orthogonal polarizations, that supports implement processing orthogonal polarization echo signals. A method is proposed to increase the information content by using the amplitude, phase and polarization characteristics of the reflected signals. This is done in order to isolate the signals reflected from biological objects against the background of interfering reflections. The use of the proposed method leads to reduce amount of processed data and a decrease the probability of false detection.

Lightweight, Solderless, Ultrawideband Transmitarray Antenna With True-Time-Delay Line

An ultrawideband (UWB) transmitarray antenna (TA) using receiving–transmitting scheme is presented in this letter. The TA overcomes its narrowband limitations by combining UWB radiators and integrated grounded coplanar transmission polylines. To reduce the manufacturing cost and the assembly complexities, all metallic components of the TA element are printed on a vertically oriented single-layer substrate, leading to a lightweight and solderless slat structure. The proposed TA element achieves true-time-delay phase responses over a fractional bandwidth of 116%, i.e., from 4.2 to 15.8 GHz, with maximum transmission loss of 1.6 dB at normal incidence. The dimensions of the designed 21 × 21 element TA aperture are 189 × 189 × 28 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , corresponding to 10 × 10 × 1.47 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ_h</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , where <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ_h</i> is the free-space wavelength at the highest operating frequency. A prototype is manufactured and measured to validate the feasibility. The experimental results agree reasonably well with simulations.