Optimized Annular Leaky Wave Antenna Architectures for Vehicular Communication

Leaky travelling wave antennas that use the first microstrip higher-order mode are analysed. The antennas investigated here are only half the width of previous leaky wave designs and utilise a structure that inherently suppresses the fundamental mode. Since mode purity is assured, the need for an elaborate feed structure is eliminated. A means for extracting the complex propagation constant of a leaky wave antenna is presented using the finite difference time domain (FDTD) method. Agreement is shown between the resulting propagation constant and another established theoretical method, the transverse resonance method. Representative measured far-field patterns are included, which are consistent with the computed propagation constants. The properties of curving the leaky wave structure are also studied.

A wideband high gain (>20dBi) beam scanning microstrip antenna array is presented for remote vital sign monitoring utilizing Doppler radar technique at 60 GHz-band. The array is designed by 32 (8×4) extended size patch elements where 8 elements are fed in series in four columns. Beam scanning is achieved by tuning the operating frequency across 58-63 GHz operating frequency band. Since a narrow frequency band is required for Doppler radar in vital sign monitoring, the beam scanning property is employed to detect vital signs of a person changing locations to different angular positions. Remote health monitoring measurements are taken with two identical antennas at 1-2 m distance from the subject. It is shown that both the breathing rate (BR) and heartbeat rate (HR) can be successfully detected within 20° of the angular range by tuning the operating frequency from 58-63 GHz.

In millimeter wave (mmWave) vehicular communications, beam scanning is usually used for beam alignment. However, beam scanning takes a long time, which makes it unsuitable in the mmWave vehicular communications with high-speed nodes. Moreover, the existing research on mmWave vehicular communications is usually based on one-hop transmission. However, due to a limited transmission range of mmWave, in many cases, multi-hop transmissions are required to transmit information from a source node to a destination node. To solve these problems, we propose an opportunistic routing protocol based on position information for beam alignment in mmWave vehicular communications. Beam alignment is performed based on the location information of neighbor nodes instead of beam scanning, which avoids the increase of network load and delay caused by beam scanning. In addition, the interference in concurrent transmissions is considered in order to optimize beamwidth and forwarding priorities. When the opportunistic routing is used, even if one candidate forwarder (CF) fails to forward a packet, the other CFs receiving the packet can still forward it, avoiding an increase in the network load and unicast delay caused by a large number of retransmissions. In an experiment, we extend the existing one-hop communication protocols into multi-hop communication protocols. Compared with these protocols, the proposed protocol yields lower end-to-end delay, higher packet delivery ratio and network throughput.

A shared ground shared radiator with wide angular coverage for mmWave 5G smartphones is proposed in this paper. A four-element corporate-fed array with conventional impedance matched power divider is designed. Stepped impedance transformers are integrated with the corner most elements to achieve pattern diversity with wide angular coverage without significant compromise in gain. The proposed three-port shared radiator conformal commercial antenna could be easily integrated with commercial mmWave 5G smartphones. All the three ports’ excitations operate in the 28 GHz band. Radiation pattern bandwidth of the multi-port system is high. The gain variation is from 6 to 11 dBi amongst the ports and across the operating spectrum. The highest mutual coupling is 10 dB, in spite of the electrically connected structure. The proposed shared radiator element has a wide angular coverage of 100°, maintaining high front-to-back ratio when the respective port is excited. Simulation and measurement results for the proposed structure are illustrated in detail.

An array of surface-wave launcher (SWL) sources is presented for surface-wave (SW) control and beam steering on a grounded dielectric slab (GDS). Specifically, a four element array configuration of non-directive SWLs is investigated. By varying the relative phase difference and magnitude between SWL elements, the excited SW field distribution on the guiding surface can be steered and controlled. Simulations and measurements of a single SWL element are provided along with simulations of the proposed array. If metallic gratings or strips, or additional dielectric layers are placed on top of the GDS, the bound SWs can be transformed into radiated leaky-waves (LWs) and directive beam patterns can be generated in the far field. Examples are provided illustrating that broadside beam steering and circular polarization can be achieved at a single frequency. These slotted SWL arrays can be useful for novel SW beam scanning designs and other LW or cavity based antennas.

This paper presents a novel low-voltage single stage CMOS RF Variable Gain Amplifier (RFVGA) designed in 130 nm IBM CMOS process technology using current feed-back gain-independent impedance matching. The proposed RFVGA has a nearly constant gain over the 400 MHz–1 GHz frequency band. Also, it has a 70 dB gain variation (-40 dB to 30 dB) which is decibel-linear within this frequency band for a control voltage in the range of 0.41 V–0.81 V. The RFVGA demonstrates high linearity (THD ≈ -60 dB) and noise immunity (average Noise Figure ≤ 6 dB). It has an input referred third-order intercept point (IIP3) of -1.5 dBm, and an input reflection coefficient (S11) under -8 dB within the frequency band of interest. Also, it dissipates around 5 mW using a 1.2 V power supply. Further, Monte Carlo simulations incorporating process, supply voltage and temperature variations (PVT variations) as well as mismatch between devices (based on width and length of devices) indicate that the design is quite robust. The proposed RFVGA is highly suitable for mobile digital television (DTV) tuner applications.

Functional hubs with disproportionately extensive connectivities play a crucial role in global information integration in human brain networks. However, most resting-state functional magnetic resonance imaging (R-fMRI) studies have identified functional hubs by examining spontaneous fluctuations of the blood oxygen level-dependent signal within a typical low-frequency band (e.g., 0.01-0.08 Hz or 0.01-0.1 Hz). Little is known about how the spatial distributions of functional hubs depend on frequency bands of interest. Here, we used repeatedly measured R-fMRI data from 53 healthy young adults and a degree centrality analysis to identify voxelwise frequency-resolved functional hubs and further examined their test-retest reliability across two sessions. We showed that a wide-range frequency band (0.01-0.24 Hz) accessible with a typical sampling rate (fsample = 0.5 Hz) could be classified into three frequency bands with distinct patterns, namely, low-frequency (LF, 0.01-0.06 Hz), middle-frequency (MF, 0.06-0.16 Hz), and high-frequency (HF, 0.16-0.24 Hz) bands. The functional hubs were mainly located in the medial and lateral frontal and parietal cortices in the LF band, and in the medial prefrontal cortex, superior temporal gyrus, parahippocampal gyrus, amygdala, and several cerebellar regions in the MF and HF bands. These hub regions exhibited fair to good test-retest reliability, regardless of the frequency band. The presence of the three frequency bands was well replicated using an independent R-fMRI dataset from 45 healthy young adults. Our findings demonstrate reliable frequency-resolved functional connectivity hubs in three categories, thus providing insights into the frequency-specific connectome organization in healthy and disordered brains.

Planar antenna designs that utilize surface waves (SWs) for leaky wave (LW) excitation are investigated for millimeter wave frequencies of operation. Surface-wave launchers (SWLs) are employed as the antenna source generating cylindrical SWs for bound propagation on a grounded dielectric slab (GDS). By the addition of a segmented circular strip grating configuration, a partially reflecting surface (PRS) can be realized, providing suitable conditions for 2-D leaky-wave radiation. Directive pencil beam patterns at broadside, with gain values greater than 12 dBi at 19.5 GHz, can be achieved.

In this paper, an Ultra-Wide-Band (UWB) printed monopole antenna based Hard Surface (HS) is proposed for RF energy harvesting to serve the application of the Internet of Things (IoT). The proposed antenna is constructed of a monopole of an open mouth flower patch mounted on an FR4 substrate and followed by an HS array. The antenna is backed with a partial ground plane to enhance the antenna bandwidth. The stability in the antenna radiation pattern over the entire frequency band is achieved by introducing three rows of the proposed HS based on H-Resonators (HS-HR) next to the patch edge. Such arrays provide an Omni directional antenna at several frequency bands that suit the application of RF energy harvesting. The array of the proposed HS-HR provides high electromagnetic impedance within the frequency band of interest toward the patch length. Numerical simulations are accompanied using CST MWS and HFSS software packages to evaluate the antenna performance. Finally, the related measurements to the antenna performance and RF harvesting are conducted at 2.45GHz. It is found that the proposed antenna provides a conversion efficiency of 35% with an acceptable gain-bandwidth product.

The design of dielectric loaded microstrip antenna (MSA) is presented in this paper. The substrate and dielectric load of MSA are made up of silicone rubber polymer, which has measured dielectric constant of 5.01 at 1 GHz. The resonant frequency of MSA is 24.35 GHz (K Band). Significant gain improvement of over 3 dB is obtained when the MSA is loaded with dielectric. The value of VSWR is also less than 2 in frequency range from 24.25 to 24.45 GHz. Measured results indicate that efficient directive radiation pattern is generated by the antenna in the frequency band of interest and is suitable candidate for Digital Electronic Message Service (DEMS) applications such as two-way high-speed communication and transfer of graphic images. The design and simulation of the MSA is carried using Computer Simulation Technology studio suite.

In this Letter, a frequency‐controlled wide‐angle beam scanning antenna operating at 0.3 THz was proposed based on metasurface. The antenna formed by H‐shape cells is periodical, and its’ scanning property is analysed by the Floquet theorem. To widen the scanning angular scope, higher order mode's diffraction wave was proposed. A systematic method was developed for the design of a practical frequency‐controlled beam scanning antenna in THz band, in which the optimisation of scanning range, linearity and the avoidance of beam blocking are comprehensively considered. Additionally, a coherent enhancement mechanism for improving the mode competition efficiency of the high‐order diffraction mode was implemented. The proposed antenna and optimisation method was verified by the measured wide‐angle beam scanning at the frequency band 0.25–0.3 THz, the measured beam scanning range of the main lobe covers from −41.7° to −25.5° with a good linearity, which is much wider than that of the first‐order mode. The diffraction efficiency of the main lobe measured is 74% on average, which indicates the remarkable inhibition of the unwanted diffraction.

In this paper, an active integrated circularly polarized leaky wave antenna (AICPLWA) is proposed. The proposed design works in X-band. The leaky wave antenna is designed using half-mode substrate integrated waveguide technique, that provides circularly polarized beam. The proposed active integrated antenna consists of a leaky wave antenna section which is cascaded with active device to make a self-oscillating radiating structure. The leaky wave antenna has beam scanning ability by varying the input signal frequency and hence the oscillator section is modified using an active tunable reactance to provide a voltage tunable oscillation frequency to the leaky wave antenna section to achieve automatic beam scanning ability. The proposed active tunable reactance provides wider tuning range than commercial varactor for a small range of variation of tuning voltage. The proposed leaky wave antenna has a wide operating range covering the whole X-band and has axial ratio of better than −4.5 dB throughout the frequency range of interest. The oscillation frequency range provided by the active section is 10.5-10.95 GHz with the variation of tuning voltage from −4 V to −1.1 V. The AICPLWA covers an automated beam scanning range from 34°-40° for the 10.5-10.95 band. The proposed AICPLWA can be used in various applications such as microwave imaging, sensing radars requiring automotive beam scanning module.

Leaky wave antennas using periodic microstrip lines are natural choices for versatile beam scanning applications. In this work, a shorted stub and an open stub are simultaneously used in the same unit cell to generate resonant frequencies dependent on the stub dimensions. Placing one such resonant frequency at the second Bragg stop band, a single wideband response is obtained. Next, the stub lengths are tuned to obtain two resonant frequencies which are placed at the second and fourth Bragg stop bands, respectively to obtain a dual wideband response. Design guidelines are outlined for obtaining these wide bands and corresponding radiation regions. Two such geometries with single and dual-band nature are fabricated. The single wide-band antenna has a pass-band from 5.89 to 11.57 GHz with a beam scanning range of −56° to 33°. The dual-band antenna has two pass-bands radiating in the frequency range 5-6.5 GHz and 10.7-14.7 GHz. Beam scanning range in the first pass-band is −72° to −5°. The second pass-band, in part, demonstrates a dual-beam nature with the forward beam scanning from 28.9° to 54.5° and backward beam scanning from −54.5° to 14.76° as the frequency varies from 12 to 14.5 GHz.

Beam scanning leaky wave antenna based on liquid crystals with gesture-controlled system

Bearing faults are by far the biggest single source of motor failures. Both fast Fourier (frequency based) and wavelet (time-scale based) transforms are used commonly in analyzing raw vibration or current data to detect bearing faults. A hybrid method, Empirical Wavelet Transform (EWT), is used in this study to provide better accuracy in detecting faults from bearing vibration data. In the proposed method, the raw vibration data is processed by fast Fourier transform. Then, the Fourier spectrum of the vibration signal is divided into segments adaptively with each segment containing part of the frequency band. Next, the wavelet transform is applied to all segments. Finally, inverse Fourier transform is utilized to obtain time domain signal with the frequency band of interest from EWT coefficients to detect bearing faults. The bearing fault related segments are identified by comparing rms values of healthy bearing vibration signal segments with the same segments of faulty bearing. The main advantage of the proposed method is the possibility of extracting the segments of interest from the original vibration data for determining both fault type and severity.