GHz Frequency Bandwidth Research Articles

Super-resolution diffractive neural network for all-optical direction of arrival estimation beyond diffraction limits

Wireless sensing of the wave propagation direction from radio sources lays the foundation for communication, radar, navigation, etc. However, the existing signal processing paradigm for the direction of arrival estimation requires the radio frequency electronic circuit to demodulate and sample the multichannel baseband signals followed by a complicated computing process, which places the fundamental limit on its sensing speed and energy efficiency. Here, we propose the super-resolution diffractive neural networks (S-DNN) to process electromagnetic (EM) waves directly for the DOA estimation at the speed of light. The multilayer meta-structures of S-DNN generate super-oscillatory angular responses in local angular regions that can perform the all-optical DOA estimation with angular resolutions beyond the diffraction limit. The spatial-temporal multiplexing of passive and reconfigurable S-DNNs is utilized to achieve high-resolution DOA estimation over a wide field of view. The S-DNN is validated for the DOA estimation of multiple radio sources over 5 GHz frequency bandwidth with estimation latency over two to four orders of magnitude lower than the state-of-the-art commercial devices in principle. The results achieve the angular resolution over an order of magnitude, experimentally demonstrated with four times, higher than diffraction-limited resolution. We also apply S-DNN’s edge computing capability, assisted by reconfigurable intelligent surfaces, for extremely low-latency integrated sensing and communication with low power consumption. Our work is a significant step towards utilizing photonic computing processors to facilitate various wireless sensing and communication tasks with advantages in both computing paradigms and performance over electronic computing.

A compact dual-sense circularly polarized SIW textile antenna for body-centric wireless communication

In this communication, a dual-sense circularly polarized textile antenna that operates at the centre frequency of 5.8 GHz is presented for body-centric wireless communication. The proposed textile antenna is realized using a substrate integrated waveguide (SIW) cavity. Circular polarization is achieved by exciting two orthogonal quarter mode apertures in 900 phase differences. A metallic via is employed to control the magnetic field coupling between the two orthogonal quarter mode apertures. The feed point and dimensions of two-quarter mode apertures can be changed to realize both left-hand and right-hand circular polarization. The proposed textile antenna has a 4.8 % impedance bandwidth covering from 5.62 to 5.90 GHz. Moreover, the textile antenna has a 2.9 % 3 dB axial ratio bandwidth covering from 5.725 to 5.875 GHz frequency bandwidth. The textile antenna has exhibited good reflection characteristics when bent on the surface of a cylindrical structure. The textile antenna has a lesser than 1.27 W/Kg SAR value in the proximity of the human phantom model for a 1 W source and also has exhibited a minimum peak gain of 5 dBi, making it conducive for integration with body-centric wireless communication.

Facile preparation and properties of polybenzoxazine/graphene porous nanocomposites for electromagnetic wave absorption

AbstractPolybenzoxazine/graphene porous nanocomposites were prepared by sol–gel and subsequent thermal curing. The porous nanocomposites showed low densities ranging from 0.154 to 0.204 g/cm3. The chemical structures and microscopic morphology of the porous nanocomposites were studied using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The electromagnetic wave absorbing ability of the porous nanocomposites was investigated, and the results showed that the minimum reflection loss for the porous nanocomposite with 15 wt% of graphene (PBG‐15) can reach −35.72 dB at a thickness of 2.6 mm with a 1.5 GHz frequency bandwidth. The excellent absorption ability was due to the conductivity loss in the porous nanocomposite. Also, PBG‐15 exhibited good heat resistance with a thermal deformation temperature near 220°C and a char yield of 56%. In addition, the addition of graphene could increase the compressive strength and compressive modulus of the porous nanocomposites by up to 126% and 364%, respectively. These polybenzoxazine/graphene porous nanocomposites have good potential application in light electromagnetic wave absorbing materials.

Orthogonally polarized meandered fed multiple input multiple output antenna array for C‐band sub‐6GHz 5G and unlicensed Wi‐Fi smart‐phone applications

An eight-element meandered fed concentric annular ring slot resonator MIMO (multiple input multiple output) antenna array with dual-band operation is presented for sub-6 GHz 5G and unlicensed C-band Wi-Fi applications. The annular slot radiators are fed by meandered elements designed for operation at 3.15–3.9 and 6.27–6.6 GHz frequency bandwidth with enhanced isolation of more than 20 and 15 dB in the respective bands. The resonator rings are placed on the four corners of the smart-phone PCB with orthogonal meandered elements. The double-band operation is because of two rings and the isolation has been improved by meandered feed elements. The performances of the proposed MIMO antenna was analyzed and validated experimentally. The design offers sufficient gain of more than 5 dBi and efficiencies of upto 75% with better radiation coverages. The measured results of the MIMO antenna are found to be in good agreement with the simulated results. Further, the antenna has been studied for SAR effects as well as radiation coverages in the proximity of users head and hand-head. The antenna housed on 130 × 70 mm 2 1.47 λ 0 × 0.79 λ 0 common ground plane has provided good characteristics making it a potential candidate for sub-6 GHz C-Band 5G and unlicensed Wi-Fi smart-phone applications.

A Novel TDoA-Based Method for 3D Combined Localization Techniques Using an Ultra-Wideband Phase Wrapping-Impaired Switched Beam Antenna

This paper presents a novel Time Difference of Arrival-based approach suitable for single-anchor positioning systems, implemented by phase wrapping-impaired array antenna. With the latter being a typical occurrence in large Switched Beam Antenna (SBA) operating in the low microwave range. The proposed method takes advantage from the large bandwidth of radio link, established between the anchor and the positioning target, by generating an unambiguous equivalent phase relationship between antenna array elements. The technique is validated by adopting a relatively large SBA antenna operating in the 4.75–6.25 GHz bandwidth, and capable to position a target in a 3D domain. Experimental data, carried out in the 4–7 GHz frequency bandwidth, show that by dealing properly with the inherent constraint of phase wrapping issues, it is possible to get a significant improvement on the elevation angle with respect to methods not capable to deal with phase reconstruction and thus operating in a phase-less context. Combining range and angle errors, the associated cumulative distribution function error in 90% of cases shows an error of 0.13 m.

Design of an Inverter-Base, Active-Feedback, Low-Power Transimpedance Amplifier Operating at 10 Gbps

In this paper, a low-power structure as an inverter-base circuit is reported for broadband applications. The focus in this study is in obtaining a low-power structure. By applying cascoded structure to an inverter as a feedforward network in the structure, the DC current and hence the power dissipation are decreased. Also, by adding a two-stage active feedback, which yields no miller capacitance, to the cascoded inverter, the structure of the TIA is completed. Simulation results in HSPICE using 90[Formula: see text]nm CMOS technology parameters show 41[Formula: see text]dB[Formula: see text] transimpedance gain, 6.5[Formula: see text]GHz frequency bandwidth and 2.7[Formula: see text][Formula: see text]Arms input referred noise, which consumes only 1.67[Formula: see text]mw power at 1[Formula: see text]V supply. Results and analysis indicate that the proposed TIA is suitable to work as a low-power 10 Gbps transimpedance amplifier in an optical receiver.

Evaluation of Common Building Wall in See-Through-Wall Application of Ultra-wideband Synthetic Aperture Radar

This paper presents the reproduced images of various objects from synthetic aperture radar (SAR) technique with ultra-wideband (UWB) signals to evaluate the performance of common building walls in the see-through-wall capability regarding security applications, object along with human detection. The walls were designed from four materials, i.e., drywall, wood, insulation, and brick, which are used in real environments. The images of the objects behind the walls were performed using the commercial UWB radar with 2.2 GHz frequency bandwidth, 2 ns of pulse width, 10 MHz of internal repetition frequency, as well as an image reconstruction algorithm. From the measurement result, the insulated wall degraded the SAR image quality. Consequently, a material that enhance the UWB signal as Frequency Selective Surface should be considered to enable SAR for disaster applications.

Utilization of a cascoded-inverter in an RGC structure as a low-power, broadband TIA

A low-power circuit structure is reported in this paper as a broadband TIA, in which the DC current and hence the power dissipation is lessened by applying cascoded structure to an inverter as an active-feedback network to a conventional Regulated Cascode (RGC) circuit. The improved RGC structure also benefits from an added active-inductor at the output node, which resonates with the output capacitance and provides extra bandwidth without the requirement of excessive current. Results for the proposed RGC-based TIA, which operates at 10 ​Gb/s, show only 1.6 ​mW power dissipation for obtaining 40 ​dBΩ transimpedance gain, 6.4 ​GHz frequency bandwidth and 25pA/√Hz input referred noise. Analysis indicate that the proposed TIA is suitable to work as a transimpedance amplifier in low-power, broadband optical communication receivers.

Frequency selective absorbing property of nanoring-shaped polyaniline with broadband absorption

Frequency selective absorbing property (FSAP) is a key to realize radar frequency selective surfaces' stealth technology, which has great application prospects in national military industry. Different from traditional metal materials, herein, through the design of polyaniline microstructure as well as doping modification of the polymerization, polyaniline nanorings (PANI NRs) with certain electrical conductivity have been constructed. By constructing nanoring-shaped morphology, PANI NRs achieve strong reflection and great absorption of electromagnetic waves (EMWs) in different frequency ranges. These two properties are vital for realizing high-efficient FSAP. PANI NRs demonstrate negative permittivity within 50–1000 MHz frequency range where they can show strong EMWs reflection, and the negative permittivity is attributed to the plasma-like behavior of conductive network formed by plenty of overlapping nanorings. In addition, this porous structure also contributes to increase reflection and refraction of incident EMWs and then continuously consuming their energy, ensuring outstanding EMWs absorption property during 2–18 GHz frequency bandwidth.

A RGC-based, low-power, CMOS transimpedance amplifier for 10Gb/s optical receivers

ABSTRACTIn this paper, a new low-power transimpedance amplifier (TIA) based on a modified Regulated Cascode (RGC) circuit structure followed by a closed-loop post-amplifier is proposed for 10 Gb/s applications. The main objective of this work is to reduce the power consumption while, the frequency bandwidth of the proposed amplifier is increased considerably. The booster of a conventional RGC is modified by a cascoded transistor and its effect on the performance of the circuit is studied mathematically, which are verified by simulations. The bandwidth extension is occurred due to increasing the gain of the booster amplifier in the RGC stage, which isolates further the input capacitance and results in a reduced input resistance value hence, a higher input pole frequency is obtained in comparison with other conventional RGC structures. On the other hand, by using an active inductive peaking technique, the frequency of the output pole is also increased which results in a further extension of the frequency bandwidth for the proposed circuit. The proposed TIA is simulated using 90 nm CMOS technology parameters, which shows a 50.5 dBΩ transimpedance gain, 7.3 GHz frequency bandwidth and 1.22 µArms input referred noise value for only 1 mW of power consumption at 1.2 V supply voltage.

Design and implementation of microstrip rotman lens for ISM band applications

This work presents the design and implementation of Rotman lens as a beam steering device for Industrial, Scientific, and Medical (ISM) applications. 2.45 GHz is considered as a center frequency design with (2-6) GHz frequency bandwidth. The beam steering is examined to cover ±21o scan angle with maximum main lobe magnitude 10.1 dBi, rectangular patch antennas are used as radiation elements to beam the output far field. The work is extended to compare between the tapered line which is used for matching between 50-Ω ports and lens cavity. CST microwave simulation studio results show that the rectangular taper line can yield 2 dB return loss less than linear taper line with a little bit shifting in responses for same input and load impedance.

An Inverter-Based, CMOS, Low-Power Optical Receiver Front-End

ABSTRACTIn this paper, a low-power optical receiver front-end which consists of a transimpedance amplifier (TIA) and three stages of limiting amplifier (LA) for 2.5 Gb/s applications is proposed in 0.18 µm CMOS technology. The proposed TIA benefits from a modified inverter structure, in which the input resistance is properly reduced due to the use of diode-connected transistors in comparison with conventional inverter circuit. Also, an active inductor is used in parallel with a diode-connected transistor at the output node, which provides a low output resistance, while it resonates with the load capacitance to extend the −3 dB frequency bandwidth. Moreover, three stages of LAs are used to obtain extra gain, in which each LA cell uses active inductor load. However, HSPICE simulations for the proposed TIA circuit show a 42.24 dBΩ transimpedance gain, 1.96 GHz frequency bandwidth, 11.7 pA/√Hz input referred noise, and only 972 µW of power consumption at 1.5 V supply. Also, simulation results for the whole receiver system show a 75.6 dB gain, 1.7 GHz frequency bandwidth, and 6.54 mW of power consumption at 1.5 V supply. Finally, simulation results indicate that the proposed receiver system has good performances to be used as a low-power optical receiver front-end.

Codesign of ${K}$ a-Band Integrated GaAs PIN Diodes Limiter and Low Noise Amplifier

In this paper, a novel concurrent design of integrated PIN-diode based limiter and low noise amplifier (LNA) is presented for Ka-band MMICs fabricated using a combined PIN/0.15-μm-pHEMT technology. To improve the small-signal performance and the power-handling capability of the limiter-LNA, the improvement of the PIN-limiter circuit structure and the survivability of the LNA network are proposed. In addition, the total chip area is 2.5 mm × 1.2 mm with an equalizer integrated on chip behind the limiter-LNA to improve the bandwidth with a minimum impact on overall NF. The measurements show that the proposed limiter-LNA with only two-stage limiter structure tolerates up to 38 dBm continuous wave (CW) input power without failure, and the average gain and the noise figure for the limiter-LNA are 17 dB and 2.2 - 2.6 dB, respectively, on the 30 - 38 GHz frequency bandwidth.

1-6.3 GHz 주파수 대역폭을 갖는 능동 인덕터 기반 가변형 이퀄라이저 설계

본 논문에서는 능동 CMOS 인덕터를 이용한 주파수 가변형 이퀄라이저를 제안하고자 한다. 1-6.3 GHz 주파수 범위에서 높은 인덕턴스 값을 유지하기 위해 피드백 저항 및 전류 블리딩을 추가하여 이퀄라이저의 이득을 향상시켰다. 설계한 주파수 가변 이퀄라이저는 65 nm 공정 파라미터를 사용하였다. 모의 실험결과 전류 블리딩 역할을 하는 트랜지스터 및 피드백 저항의 사이즈 조절을 통해 인덕턴스를 6.3 GHz 영역까지 조절할 수 있으며, 크기는 1.2 GHz 기준 최대 25 nH 수준까지 튜닝이 가능하게 하여 다양한 특성을 갖는 채널에 적용할 수 있다.

Wideband dual‐polarised SAW spiral antenna for monopulse system

This study proposes a new technique for generating dual polarisation in spiral antennas. The proposed antenna is achieved by creating stair discontinuities in spiral antenna arms, entitled stair arm width (SAW) spiral antenna. Commonly, the spiral antenna is activated in direction finding systems, especially in wideband monopulse systems. Capability of generating sum and difference beams over a wide bandwidth is another feature of the proposed antenna. Radiation characteristics and generated modes of a wideband dual polarised four-arm SAW antenna in comparison with the modulated arm width (MAW) and conventional spiral antennas are presented. The cross-polarisation gain of SAW antenna, compared to MAW antenna, is decreased in difference pattern, which improves the antenna circular polarisation purity. Moreover, the input impedance of the proposed antenna with high n s is more stable than MAW antenna over a wide bandwidth due to gradual discontinuities. Finally, a prototype four-arm SAW spiral antenna is built and evaluated with an available beamformer for 5.8-10 GHz frequency bandwidth. Simulated and measured radiation characteristics proved dual circularly polarised and wideband properties of the antenna.

A CMOS Low-Power Optical Front-End for 5 Gbps Applications

ABSTRACTIn this paper, a new low-power optical receiver front-end is proposed in 90 nm CMOS technology for 5 Gb/s AApplications. However, to improve the gain-bandwidth trade-off, the proposed Trans-Impedance Amplifier (TIA) uses an active modified inverter-based topology followed by a common-source amplifier, which uses active inductive peaking technique to enhance the frequency bandwidth in an increased gain level for a reasonable power consumption value. The proposed TIA is analyzed and simulated in HSPICE using 90 nm CMOS technology parameters. Simulation results show a 53.5dBΩ trans-impedance gain, 3.5 GHz frequency bandwidth, 16.8pA/√Hz input referred noise, and 1.28 mW of power consumption at 1V supply voltage. The Optical receiver is completed using three stages of differential limiting amplifiers (LAs), which provide 27 dB voltage gain while consume 3.1 mW of power. Finally, the whole optical receiver front-end consumes only 5.6 mW of power at 1 V supply and amplifies the input signal by 80 dB, while providing 3.7 GHz of frequency bandwidth. Finally, the simulation results indicate that the proposed optical receiver is a proper candidate to be used in a low-power 5 Gbps optical communication system.

Low-cost three-dimensional millimeter-wave holographic imaging system based on a frequency-scanning antenna.

In this paper, a closed-form two-dimensional reconstruction technique for hybrid frequency and mechanical scanning millimeter-wave (MMW) imaging systems is proposed. Although being commercially implemented in many imaging systems as a low-cost real-time solution, the results of frequency scanning systems have been reconstructed numerically or have been reported as the captured raw data with no clear details. Furthermore, this paper proposes a new framework to utilize the captured data of different frequencies for three-dimensional (3D) reconstruction based on novel proposed closed-form relations. The hybrid frequency and mechanical scanning structure, together with the proposed reconstruction method, yields a low-cost MMW imaging system with a satisfying performance. The extracted reconstruction formulations are validated through numerical simulations, which show comparable image quality with conventional MMW imaging systems, i.e., switched-array (SA) and phased-array (PA) structures. Extensive simulations are also performed in the presence of additive noise, demonstrating the acceptable robustness of the system against system noise compared to SA and comparable performance with PA. Finally, 3D reconstruction of the simulated data shows a depth resolution of better than 10cm with minimum degradation of lateral resolution in the 10GHz frequency bandwidth.

Monostatic ultra-wideband GPR antenna for through wall detection

The aim of this paper is to present a monostatic arc-shaped ultra-wideband (UWB) printed monopole antenna system with 3-16 GHz frequency bandwidth suitable for through-wall detection. Ground penetrating radar (GPR) technique is used for detection with the gain of 6.2 dB achieved for the proposed antenna using defected ground structure (DGS) method. To serve the purpose, a simulation experiment of through-wall detection model is constructed which consists of a monostatic antenna act as transmitter and receiver, concrete wall and human skin model. The time domain reflection of obtained result is then analysed for target detection.

High dynamic range single channel sampling of wideband RF signals using ultra‐fast nanoscale photoconductive switching

This Letter reports on new experimental high dynamic range sub-sampling performances obtained from nanoscale microwave photoconductive switches operating under a 0.8 µm wavelength pulsed illumination. Experimental results have been performed on different samples benefiting of a low temperature grown Gallium Arsenide absorbing layer on GaAs substrate, coplanar microwave electrode profile optimisation, and the use of an ultra-low noise jitter optical source delivering optical pulses of 1 to10 ps pulse width at a 2 GHz repetition frequency at 0.8 µm optical wavelength. Thanks to carrier lifetime tunability achievement from 1 to 20 ps, in association with a carrier mobility of 3900 cm²/V.s, experimental demonstrations of 54 and 45 dB signal-to-noise ratio microwave signal sampling for signals at 5,76 and 20 GHz frequency bandwidth respectively confirms submicron devices functionality as a new class of single channel photonic analogue to digital converters.

Wideband Dual-Polarized Cross-Shaped Vivaldi Antenna

This communication presents a wideband, dual-polarized Vivaldi antenna or tapered slot antenna with over a decade (10.7:1) of bandwidth. The dual-polarized antenna structure is achieved by inserting two orthogonal Vivaldi antennas in a cross-shaped form without a galvanic contact. The measured $- 10\,\hbox{dB}$ impedance bandwidth ( ${S_{11}}$ ) is approximately from 0.7 up to 7.30 GHz, corresponding to a 166% relative frequency bandwidth. The isolation ( ${S_{21}}$ ) between the antenna ports is better than 30 dB, and the measured maximum gain is 3.8–11.2 dB at the aforementioned frequency bandwidth. Orthogonal polarizations have the same maximum gain within the 0.7–3.6 GHz band, and a slight variation up from 3.6 GHz. The cross-polarization discrimination (XPD) is better than 19 dB across the measured 0.7–6.0 GHz frequency bandwidth, and better than 25 dB up to 4.5 GHz. The measured results are compared with the numerical ones in terms of $S$ -parameters, maximum gain, and XPD.