Antenna Placement Research Articles

Microwave ablation of colorectal liver metastases adjacent to the cardiophrenic angle: Parallel versus non-parallel placement of the antenna relative to the diaphragm

PurposeMicrowave ablation (MWA) is difficult to perform in colorectal liver metastases (CRLMs) adjacent to the cardiophrenic angle. Therefore, a modified approach involving antenna array placement parallel to the diaphragm was initially attempted. Its safety and efficacy were compared with those involving non-parallel placement. MethodsSixty-three patients with CRLMs adjacent to the cardiophrenic angle (lesions within 10 ​mm of the diaphragm) who underwent MWA were included in the study. All patients were further classified into parallel and non-parallel groups according to the method of antenna placement. The distance between the lesion and diaphragmatic surface before MWA, complications, and local tumor progression (LTP) at the last imaging follow-up were recorded. LTPs in the two groups were compared using the log-rank test. Prognostic factors for LTP were assessed using the Cox proportional hazards regression model. ResultsThirty and 33 lesions were ablated using parallel and non-parallel antenna placement, respectively. During the mean follow-up duration of 19.7 ​± ​8.2 months, the LTP rate in the parallel and non-parallel placement groups were 3.3% (1/30) and 24.2% (8/33), respectively. The log-rank test showed that parallel antenna placement was associated with delayed LTP (p ​= ​0.018). Multivariate Cox regression analysis showed that parallel antenna placement was an independent predictor of delayed LTP after adjusting for possible risk factors, including age, sex, tumor size, and KRAS mutation (hazard ratio, 0.1; 95% confidence interval, 0.00, 0.80; p ​= ​0.034). ConclusionThe placement of the antenna parallel to the diaphragm is an alternative and effective method for MWA of CRLMs near the cardiophrenic angle and can contribute to the reduction of the LTP rate.

Arcing fault diagnosis using enhanced cross-correlation technique

This study explored the potential use of cross-correlation as a technique for detecting arcing faults in a power system distribution network. The cross-correlation technique was employed to investigate the effect of each antenna placement as a detection device, time difference of arrival (TDOA), time delay, and correlation magnitude of arcing signals detected during on-line arcing fault measurement. The arcing fault was detected using four antennas that had been set up around the arc source point in a high voltage (HV) laboratory. The measurements were taken using a digital oscilloscope. For precise results, the Discrete Wavelet Transform (DWT) denoising technique combined with cross-correlation (CC) technique were applied using MATLAB software to identify the arcing signals detected in order to diagnose the differentiation between noisy and real arcing fault signals. Further assessment was carried out by performing a cross-correlation technique on the real arcing signals obtained to find the similarities and arrival time’s delay between single arcing signals’ placement. The outcome shows that all measurements including the time difference of arrival (TDOA), correlation magnitude, time delay, and antennas’ placement towards the arcing source point are valuable in determining the arcing signals detected precisely.

Design and Realization of a Broadband Multi-Beam 1×2 Array Antenna Based on 2×2 Butler Matrix for 2.45 GHz RFID Reader Applications

This paper presents design and analysis of a beam switchable [Formula: see text] array patch antenna fed by a [Formula: see text] Butler matrix based hybrid coupler for 2.45[Formula: see text]GHz radio frequency identification (RFID) reader applications in the ISM band. The proposed beam switchable array antenna arrangement consists of two identical patch elements, a pleated quarter-wavelength impedance transformer (PQWIT), and a hybrid coupler. The concept of PQWIT has been utilized to reduce the overall implementation area of the patch elements. The overall area of the patch element is miniaturized by 50% due to the implementation of PQWIT. This miniaturized antenna is used as a radiating element for designing a beam switchable [Formula: see text] array antenna fed by a hybrid coupler. The proposed antenna prototype has been fabricated on a 1.56[Formula: see text]mm thick Rogers RT/duroid 5880 substrate with a physical area of [Formula: see text][Formula: see text]mm2. The simulation and measured results exhibit good agreements. The designed antenna offers a broad bandwidth of 844[Formula: see text]MHz (1.956–2.80[Formula: see text]GHz), peak gain of 8.86 dB, peak radiation efficiency of 99.52% and has two switchable beams in the directions [Formula: see text] and [Formula: see text]. The suggested switched beam array antenna is suitable for RFID reader applications at 2.45[Formula: see text]GHz for tracking of moving objects.

Positioning and Tracking of Multiple Humans Moving in Small Rooms Based on a One-Transmitter-Two-Receiver UWB Radar Configuration.

The paper aims to propose a sequence of steps that will allow multi-person tracking with a single UWB radar equipped with the minimal antenna array needed for trilateration. Its localization accuracy is admittedly limited, but on the other hand, thoughtfully chosen placement of antennas can increase the detectability of several humans moving in their immediate vicinity and additionally decrease the computational complexity of the signal processing methods. It is shown that the UWB radar measuring with high rate and fine range resolution in conjunction with properly tuned processing parameters can continually track people even in the case when their radar echoes are crossing or merging. Emphasis is given to the simplified method of the time-of-arrival (TOA) estimation and association and the novel method needed for antenna height compensation. The performance of the proposed human tracking framework is evaluated for the experimental scenario with three people moving closely in a small room. A quantitative analysis of the estimated target tracks confirms the benefits of suggested high antenna placement and application of new signal processing methods in the form of decreasing the mean localization error and increasing the frequency of correct target position estimations.

Sing-Ant: RFID Indoor Positioning System Using Single Antenna with Multiple Beams Based on LANDMARC Algorithm

RFID localization methods have been widely used in indoor positioning systems (IPS). Most localization techniques involve the use of multiple antennas and the placement of antennas and readers in order to ensure accurate positioning results. However, most localization techniques are complex and require high overhead costs in terms of needing multiple antennas and RFID readers. In this paper, we proposed a method to use a single antenna to perform all the reads and rely rather on the antenna beams to acquire multiple positioning data. A single array of antennas is configured to have multiple angles of operation and rely on different power levels as compared to regular antennas. By manipulating the beam pattern, direction and power, multiple sub-antennas can be conceived and the method utilizes antenna beams and relies mainly on one antenna to realize two-dimensional localization.

Joint Antenna Placement and Power Allocation for Target Detection in a Distributed MIMO Radar Network

Radar network configuration and power allocation are of great importance in military applications, where the entire surveillance area needs to be searched under resource budget constraints. To pursue the joint antenna placement and power allocation (JAPPA) optimization, this paper develops a JAPPA strategy to improve target detection performance in a widely distributed multiple-input and multiple-output (MIMO) radar network. First, the three variables of the problem are incorporated into the Neyman–Pearson (NP) detector by using the antenna placement optimization and the Lagrange power allocation method. Further, an improved iterative greedy dropping heuristic method based on a two-stage local search is proposed to solve the NP-hard issues of high-dimensional non-linear integer programming. Then, the sum of the weighted logarithmic likelihood ratio test (LRT) function is constructed as optimization criteria for the JAPPA approach. Numerical simulations and the theoretical analysis confirm the superiority of the proposed algorithm in terms of achieving effective overall detection performance.

Max-Min fairness-based resource allocation in massive MIMO systems

This work deals with power and spectrum allocation approaches for massive MIMO (M-MIMO) systems. An analysis is made to verify the efficiency of the solutions provided by schemes used for the spectral and energy efficiency (SE-EE) trade-off problem in massive antenna-based wireless communication systems. We first introduce the Geometry Based Stochastic Model (GBSM) channel model (One-ring model), describing the behavior of a uniform linear array of antennas (ULA) arrangement, revealing how the channel parameters affect the channel capacity. We also show that under this model, the SE still increases without boundary when the massive number of base-station (BS) antennas $M$ increases, provided that pilot contamination is substantially mitigated or eliminated but when the number of users equipment (UEs) $K$ increases with a fixed number of antennas in the BS, there is a increasing limitation from the combiners in mitigating the inter-user interference, making decoding difficult. The downlink (DL) M-MIMO scenario is analyzed, by introducing the generalized power allocation problem and derived the max-min fairness scheme from it. We propose a procedure to solve the max-min problem and

Design and Analysis of High-Capacity MIMO System in Line-of-Sight Communication.

The phase of the channel matrix elements has a significant impact on channel capacity in a mobile multiple-input multiple-output (MIMO) communication system, notably in line-of-sight (LoS) communication. In this paper, the general expression for the phase of the channel matrix at maximum channel capacity is determined. Moreover, the optimal antenna configuration of the 2 × 2 and 3 × 3 transceiver antenna array is realized for LoS communication, providing methods for optimal antenna placement, which can be used in short-range LoS communication and non-scattering environment communication, such as coupling train communication and inter-satellite communication. Simulation results show that the 2 × 2 rectangular antenna array is more suitable for the communication of coupling trains, while the 3 × 3 circular arc antenna array is more suitable for virtual coupling trains according to antenna configurations. Moreover, the 2 × 2 antenna rectangular configuration proposed in this paper has reached the optimal channel in inter-satellite communication, which lays a foundation for the deployment of communication systems.

2-D Printed 8-element compact UWB diversity antenna for multi-service-multi-mode applications

A 2-D compact 8-element UWB diversity antenna of dimension 28 mm × 28 mm each, is proposed to operate from (4.1–24) GHz with 141.63% IBW for multi-service-multi-mode (MS2M) applications. With self-similar antennas, the antenna design embodiment is constructed by asserting cross-coupled inter-connect bridge substrates to accomodate eight radiating elements in a compact footprint. This configuration results in good isolation between non overlapped antenna clusters, the ortho-centric antenna arrangement asserts pattern diversity and avoids the dependancy of additional decoupling network. The performance metrics consists of isolation coefficient of >20 dB at all ports, realized gain varies from (4.5–8.1) dBi and ECC from far-field magnitude < 0.08, which makes it suitable for UWB diversity applications. To validate the multi-port antenna performance, a full-wave simulation PTFE shield enclousure with volume of 40 mm × 40 mm × 40 mm has been demonstrated, which shows good results in correlation to EM-simulation. With good performance attributes in the shield enclousure, the multi-port antenna can be exported to a fully fledged plastic jacketed cage for real-time environment. Finally, a prototype antenna is fabricated and measured with good agreements to validate the overall RF performances.

A Method of Indoor Positioning by Signal Fitting and PDDA Algorithm Using BLE AOA Device

Though Global Navigation Satellite System (GNSS) has been pretty mature and widely used in our daily life, the positioning of the indoor environment cannot be realized due to the shielding of concretes or glasses by GNSS. Many positioning methods have been proposed to solve that problem, and Bluetooth Low Energy (BLE) is one of the most widely used wireless technologies. This paper takes BLE Angle of Arrival (AOA) as the research object and proposes a method based on signal fitting and Propagator Direct Data Acquisition (PDDA) angle estimation algorithm. This method can be applied to both linear antenna array and rectangular antenna array and has good positioning performance. The method proposed in this paper does not need to calculate the phase differences between antennas, making it unnecessary to calculate the intersection of cones during spatial positioning. The angle estimation is divided into two steps. Firstly, the frequency deviation of Constant Tone Extension (CTE) is calculated based on the IQ samples captured during the reference period, and the received signal matrix of all antennas is fitted based on frequency deviation. Secondly, the antenna received signal model is established based on hardware antenna arrangement, and the arrival angle is estimated by the PDDA algorithm. In order to verify the effectiveness of the proposed method, the plane and spatial positioning experiments are carried out using the BLE devices of Nordic Company, which shows a good positioning accuracy. In spatial positioning, the average positioning accuracy of BLE in channel 37, channel 38, and channel 39 is 0.59m, 0.74m, and 0.77m, respectively, which can meet the basic indoor positioning requirements and cover a large area by one receiver. Compared with the classical MUSIC algorithm, the PDDA algorithm has the same positioning accuracy but lower computational complexity, so it has certain advantages.

Microstrip Antenna Design for a non-Invasive Glucose Sensor

Diabetes Mellitus (DM) is one of the diseases with many patients in the world. The current method used by people with diabetes was an invasive approach using blood samples to monitor their blood glucose levels. The non-invasive approach that does not require blood samples would increase ease-of-use for diabetics. This research presents a microstrip antenna to monitor glucose levels in human blood non-invasively. The background concept of this approach was blood glucose variation causes variations of blood permittivity accordingly. This blood permittivity will affect the resonant frequency of the microstrip antenna. Antenna design and simulation were performed using CST Microwave Studio software. The antenna is designed on FR4 (εr = 4.3) dan NPC H220 (εr = 2.17) substrate with h = 1.6mm. A patch of microstrip antenna placed on one side and ground plane on another side, they are connected using SMA connector. The fabrication result of the designed antenna has an operating frequency of 2.17 GHz. In this research, the correlation between blood glucose and changing the microstrip antenna’s resonant frequency was observed. For this non- invasive method, the microstrip antenna is placed facing the forearm. Experimental results of both approaches, antenna placement with and without spacing to the forearm, show the shift of resonant frequency according to blood glucose changes. Based on this research’s linearity, accuracy, and sensitivity result, the microstrip antenna shows potential as a glucose- sensing device for a non-invasive method with further development.

Optimum polarization configuration of planar circular patch MIMO antenna

Multiple Input Multiple Output (MIMO) is a key technology that plays an important role in achieving the 5G requirement due to its capability to increase channel capacity. However, the increase of channel capacity is influenced by several aspects such as mutual coupling. Many methods are done to decrease the mutual coupling effect such as polarization arrangement of the MIMO antennas. This study on the polarization arrangement of a circular patch MIMO antenna at 3.5 GHz was performed. Four elements of the MIMO antenna are arranged with several polarization configurations both in Co-Polarization and Cross-Polarization. Both simulation and measurement results showed that MIMO with Co-Polarization has a slightly wider bandwidth equal to 295.25 MHz compared to Cross-Polarization with a bandwidth of 274.63 MHz, due to better return loss performed by the former. However, from the mutual coupling perspective, it is observed that MIMO with Cross-Polarization can reduce the mutual coupling from -17.6676dB into -22.462 dB compared to Co-Polarization with the same element distance.

Thinned array antenna synthesis using modified binary particle swarm optimization with minimization of sidelobes

PurposeThe purpose of this paper is to propose radiating system by avoiding electromagnetic interference in unwanted directions and to radiate the energy in the required direction with an optimization technique.Design/methodology/approachPractically, multiple, incompatible variables require concurrent boost on a synthesis of systematic antenna assemblage. The authors have worked out the main statistic penalty function to ensure all the restrictions. Here, MBPSO (Modified Binary Particle Swarm Optimization) is developed and introduced thin planar synthesis restriction. The sigmoid function is used to update the particle position. Different analytical demonstrations have been carried out, and the exhibited methods are predominant than the algorithms.FindingsA 20 × 10 planar antenna array is synthesized using modified BPSO. The authors have suppressed the PSLL in two principal planes and as well as in the entire f plane. Numerical results state that MBPSO outperforms the other binary BPSO, BCSO, ACO, RGA, GA optimization techniques. MBPSO achieved a −51.84 dB PSLL level, whereas BPSO achieved −48.57 dB with the same 50% thinning.Originality/valuePlanar array antenna formation is one of the most complex syntheses because the array gets filled with more antenna elements. The machine-like complication and implementation of such an antenna arrangement with a broad opening would be expensive. It is not easy to control the required radiation patterns shape by using a uniform feeding network. To get better flexibility for sustaining the sidelobe levelheaded along with consistent amplitude distribution. So as far as prominence has been given to the evolutionary algorithm, find an ideal solution for objective array combinational problems.

Real-time detection of small anomaly from limited-aperture measurements in real-world microwave imaging

This study concerns a subspace migration technique used to identify the shape and location of an unknown anomaly from scattered parameter data collected within the scattering matrix for a limited-aperture inverse scattering problem. The mathematical theories of subspace migration are partially understood in terms of limited-aperture inverse scattering problems, but little investigation of real-world applications, such as microwave imaging, has taken place. Hence, we perform further research to analyze the subspace migration and explain the reasons for a number of unexplained phenomena. For theoretical corroboration, we prove that the imaging function of subspace migration is composed of an infinite series of integer-order Bessel functions of the first kind, and we outline the arrangement and the total number of antennas for transmitting and receiving signals. This is based on the application of the Born approximation to the identification of an anomaly and the uniform convergence of the Jacobi–Anger expansion formula. Various results of numerical simulations with synthetic and real data are exhibited to support the theoretical results of the imaging function and explain the reasons for a number of phenomena as well as the fundamental limitations. Further, we suggest a method of antenna arrangement to obtain better results and confirm the improvements through simulations.

Nano-antenna array for high efficiency sunlight harvesting.

Solar rectennas are promising devices for energy harvesting. Capability of rectennas to convert incident light into useful energy depends on the antenna efficiency, that is the ratio between the power transferred to the load vs the incoming power. In this work, we first emphasize that for the efficiency to be calculated accurately, antennas need to be treated as receiving devices, not as transmitting ones. Then, we propose an arrangement of antennas that differs from those published so far in three respects: (1) the proposed arrangement is formed by an array of nano-antennas with sub-wavelength inter-element spacing, (2) it comprises a reflecting mirror, and (3) it allows for dual polarization operation. Through numerical simulations, we show that the small lattice pitch we use is responsible for frequency flattening of the lattice impedance over the whole solar spectrum, eventually allowing for excellent matching with the antennas' loads. Also, the small pitch allows for a smooth dependence of the receiving efficiency on the angle of incidence of sunlight. Finally, we show numerically that the reflecting mirror also allows for an almost complete cancellation of light scattered by the receiving antennas. The final result is a polarization insensitive receiving theoretical efficiency larger than 70% over the whole 300-3000nm spectral range, with a less than 10% energy wasting due to back-scattering of sunlight.

Navigation Improves Tumor Ablation Performance: Results From a Novel Liver Tumor Simulator Study.

The efficacy of microwave ablation in treating hepatic tumors requires advanced ultrasound skills. Failure of proper technique has the potential for either under- or over-treatment and possible harm to the patient. Emprint SX™ navigation provides surgeons with intra-operative, real-time navigation through augmented reality localization of the ablation antenna and the expected ablation zone. We hypothesize that incorporating this technology leads to improved targeting and optimizes ablation coverage. This study utilizes a simulated model to evaluate ablation outcomes using Emprint SX™ navigation vs standard ultrasound. Surgical residents and faculty were recruited from a single institution. Using a novel tumor ablation simulator, participants performed ablations via 2 modes: standard ultrasound guidance (STD) and Emprint SX™ navigation (NAV). Primary outcome was the percentage of under-ablation. Secondary outcomes included percentage of over-ablation, time to complete trial, and number of attempts to position antenna. 281 trials were performed by fifteen participants, with 47% female and 60% novice ablationists. Under-ablation volume decreased by a mean of 16.3% (SEM ±12.9, P < .001) with NAV compared to STD. Over-ablation volume decreased by a mean of 14.0% (±8.2, P < .001). NAV time was faster by a mean of 32 seconds (±24.9, P < .001) and involved fewer antenna placement attempts by a mean of 1.3 (±1.0, P < .001). For novice ablationists, all outcomes were improved with NAV and novices saw larger improvements compared to experienced ablationists (P = .018). In a simulated model, NAV improves ablation efficacy and efficiency, with novices gaining the greatest benefit over standard ultrasound.

Transmit Antenna Placement Based on Graph Theory for MIMO Radar Detection

Optimal antenna placement for target detection using multiple-input multiple-output (MIMO) radar system with widely separated antennas is studied in this paper. Considering the problem of placing a limited number of transmit antennas in a given space to maximize the detection performance, an optimization problem is formulated with the output signal-to-noise ratio (SNR) indicator as the performance metric. The initial problem is a nonlinear integer programming problem, and with the increase of the number of antennas, the computational complexity using traditional methods can be huge. In this paper, we discretize the feasible space into several grid points and employ graph theory to handle the problem. The antennas and grid points can be viewed as vertices in a bipartite graph, so that the antenna placement problem can be viewed as seeking for a proper matching between two vertex sets. We transform the problem into a stable matching (SM) problem and a maximum weighted matching (MWM) problem respectively, and propose Gale-Shapley (GS)-based and Kuhn-Munkres (KM)-based algorithms to deal with them with polynomial complexity. Numerical examples are provided to evaluate the effectiveness of the proposed methods.

Aliasing Artifacts Suppression in MIMO Millimeter-Wave Imaging Systems Based on K-Space Analysis

This paper focuses on dealing with aliasing artifacts in millimeter-wave imaging systems. To address the challenges and complexities of designing multi-static arrays, sparse arrangements are utilized in practical imaging systems. Depending on the arrangement of antennas, such arrays may present severe aliasing artifacts. Some techniques have already been introduced to tackle such artifacts and enhance the image quality. These techniques may either distort the target image by causing some loss in parts of the image, impose high computational/system costs or suffer from the lack of generalizability. One of these techniques uses non-uniform arrays. Such arrays are designed by optimizing the point spread function (PSF). The PSF is a suitable representative of the system&#x2019;s performance provided that the system is shift-invariant. Since non-uniform arrays are shift-variant, these techniques are unreliable, especially in the case of off-center targets. As a consequence, there are no frameworks to design non-uniform arrays on a reliable basis to suppress aliasing artifacts in the whole region of interest (ROI). To address this issue, based on the k-space analysis of aliasing in multi-static arrays and non-uniform Fourier transform concept, we propose a small random displacement to be applied to antennas&#x2019; location in sparse periodic arrays. This displacement prevents the aliasing components from coherently accumulating. Nevertheless, due to the imposed non-uniformity, it is impossible to use FFT-based algorithms in this case. A subsequent resampling or the use of non-uniform FFT can address this problem. The provided simulations and experimental measurements show that the proposed method can efficiently lower the peak level of aliasing artifacts by around 3dB compared to sparse periodic arrays. So, the proposed method can be used as an effective way to suppress aliasing artifacts in real-time multi-static millimeter-wave imaging systems.

Influence of User Mobility and Antenna Placement on System Loss in B2B Networks

In this paper, the influence of user mobility and on-body antenna placement on system loss in body-to-body communications in indoor and outdoor environments and different mobility scenarios is studied, based on system loss measurements at 2.45 GHz. The novelty of this work lies on the proposal of a classification model to characterise the effect of user mobility and path visibility on system loss, allowing to identify the best set of on-body antenna placements. To quantify the influence of visibility and mobility on the average system loss, a combined score is proposed, allowing to map system loss onto the degree of visibility and mobility that depends on the scenario being considered and on on-body antenna placements. Overall, a good agreement is observed between the proposed classification model and the average measured values of system loss, with the higher values of combined scores being associated with lower values of systems loss. For the cases under study, the average values of system loss are 61.6 dB for the cases of the antennas being positioned only on the front of the body and/or the head, and 64.5 dB if at least one of the antennas is placed on an arm.

Quantitative evaluation of electromagnetic wave environment before and after re-laying of leaky coaxial cable for wireless medical telemeter

For the safe use of wireless medical telemeter, it is important to manage electromagnetic wave such as appropriate channel management and antenna placement. However, many hospitals have reported reception problems caused by inappropriate electromagnetic wave management. In our hospital, the cause of the reception failure of wireless medical telemeter that occurred May 2020 was presumed to be a mistake in the leaky coaxial cable. In this study, we measured the electromagnetic waves before and after the re-laying of the leaky coaxial cable to quantitatively evaluate and examine the electromagnetic wave conditions of the wireless medical telemeter. Before re-laying of the leaky coaxial cable, as a result of measuring the electromagnetic wave strength around the booster where the reception failure occurred, the carrier to noise ratio (CNR) was lower than 30 dB recommended by the manufacturer. Therefore, it was found that the electromagnetic wave received by the antenna was not sufficiently amplified by the booster. After re-laying of the leaky coaxial cable and changing the position of the booster, the CNR exceeded 30 dB at all measurement points and the reception problem disappeared.