A slotted microstrip patch antenna for fifth‐generation (5G) mobile applications is presented in this paper. The proposed antenna addresses the intrinsic narrow bandwidth of patch antennas by ...introducing rectangular slots in the form of a disjointed H‐slot to broaden the bandwidth. The patch design and the slots introduce two extra resonances to broaden the bandwidth of the antenna. An impedance bandwidth of 26.6% from 24.95 to 32.6 GHz was achieved. A measured peak gain of 9.44 dBi was also achieved with a minimum half‐power beamwidth of 36° over the entire bandwidth. The proposed slotted patch antenna is implemented on a 44.6 mm × 26.3 mm × 0.8 mm RT5880 Printed Circuit Board.
Planar resonator probes have been successfully used for high-resolution near-field microwave imaging in the past. However, the reported imaging systems which were developed based on these probes ...require lengthy mechanical scanning to cover the imaging area. Such a lengthy image acquisition process is not desired in many practical applications where rapid screening is required. In this article, a 1-D imaging array of planar resonator probes is introduced for rapid near-field imaging. The strong coupling between the resonant elements in the array is conveniently controlled through active loading of each element with a p-i-n diode detuning circuit. Once the coupling is mitigated, each array element provides an independent measurement as desired to form the image. The probe and array design are detailed herein. The array response and its near-field imaging performance are thoroughly investigated using many practical samples.
The integration of antennas in composite structures is gaining popularity with advances in wireless communications and the ever-increasing demands for efficient smart structures. Efforts are ongoing ...to ensure that antenna-embedded composite structures are robust and resilient to inevitable impacts, loading and other external factors that threaten the structural integrity of these structures. Undoubtedly, the in situ inspection of such structures to identify anomalies and predict failures is required. In this paper, the microwave non-destructive testing (NDT) of antenna-embedded composite structures is introduced for the first time. The objective is accomplished using a planar resonator probe operating in the UHF frequency range (~525 MHz). High-resolution images of a C-band patch antenna fabricated on an aramid paper-based honeycomb substrate and covered with a glass fiber reinforced polymer (GFRP) sheet are presented. The imaging prowess of microwave NDT and its distinct advantages in inspecting such structures are highlighted. The qualitative as well as the quantitative evaluation of the images produced by the planar resonator probe and a conventional K-band rectangular aperture probe are included. Overall, the potential utility of microwave NDT for the inspection of smart structures is demonstrated.
Integrity assessment of metallic structures requires inspection tools capable of detecting and evaluating cracks reliably. To this end, many microwave and millimeter-wave nondestructive testing and ...evaluation (NDT&E) methods have been developed and applied successfully in the past. Detection of fatigue cracks with widths less than <inline-formula> <tex-math notation="LaTeX">5~\mu \text{m} </tex-math></inline-formula> using noncontact microwave-based inspection methods was demonstrated in the 1970s. Since their introduction, these methods have evolved considerably toward enhancing the detection sensitivity and resolution. Undertaking key application challenges has attracted considerable attention in the past three decades and led to the development of the near-field techniques for crack detection. To address a need that cannot be fulfilled by other NDT&E modalities, innovative noncontact microwave and millimeter-wave NDT&E methods were devised recently to detect cracks of arbitrary orientations under thick dielectric structures. While the reported methods share the same underlying physical principles, they vary considerably in terms of the devised probes/sensors and the application procedure. Consequently, their sensitivity and resolution as well as their limitations vary. This article reviews the various crack detection methods developed to-date and compares them in terms of common performance metrics. This comprehensive review is augmented with experimental comparisons and benchmarking aimed to benefit NDT&E practitioners and researchers alike.
This paper presents a design methodology and prototyping of an angular speed sensor based on microwave polarimetry. The detection mechanism relies on the transmission response of a dual-polarized ...circular aperture irradiating an array of regularly spaced copper traces printed on a PCB. The generated response is a regular pulse train defined by the location of the copper trace with reference to the center of the circular aperture. While the angular speed sensor can be sampled at any rate and for any time length, the detector response was acquired within a 1s duration with the circular aperture response effectively sampled at 10 kHz for demonstration purpose. The acquired response was analyzed in the frequency domain using Fast Fourier Transform (FFT) and the rotor speed was obtained from the frequency spectrum of the acquired pulse train. To demonstrate the working principle of the detection system, the printed PCB rotor which occupies an area of 84.64 cm 2 was attached to a rotary stage set to rotate at certain angular speeds including but not limited to 62 RPM. In all the speed settings, the speeds were detected in 1s with a worst-case error of ±0.625 RPM.
Detecting covered cracks in metals is critical in many applications. In this article, a single dual-polarized circular aperture antenna and synthetic aperture imaging are devised to detect ...arbitrarily oriented cracks covered under thick dielectric layer. The devised monostatic quad-polarized system facilitates measurements of the reflection (copolarized) and transmission (cross-polarized) parameters which form the basis for reliable detection. Through analysis and measurements involving dielectric covers with thicknesses ranging from 4.25 to 12.7 mm, it will be demonstrated that the background clutter and the effect of the cover are largely suppressed in the images formed using the cross-polarized parameter. On the other hand, it will be highlighted that the crack could be actually masked by the clutter in the image formed using the reflection measurements commonly used for crack detection.
The presence of undesirable solid contaminants can have adverse effects on the integrity of gas pipelines. One of the most common contaminants in such pipelines is black powder. Developing predictive ...maintenance protocols, including online quality monitoring, is imperative to ensure the on-spec supply of gas to customers and to avoid severe consequences such as pipeline blockage. In this paper, a microwave sensing system that utilizes resonant probes for the detection and monitoring of solid contaminants, is presented. The proposed probe is essentially a conventional circular waveguide with a resonant iris structure attached to the aperture. The concentration of solid contaminants in gas flows is assessed by analyzing the scattering parameters of transmitting/receiving probes at a resonant frequency, which are coupled non-intrusively to the pipeline. 3D electromagnetic simulations are performed for sensitivity analysis of the proposed sensing system. Furthermore, the detection and evaluation of solid contaminants are experimentally validated using air/sand flow in a 51 mm inner diameter pipeline. The efficacy of the proposed system is demonstrated following the successful detection of solid contaminants in the dual-phase flow. Additionally, it is also illustrated that inclusion of a resonating iris structure in the aperture of the circular waveguide results in enhanced sensitivity when compared to a non-resonant counterpart.
The utility of wideband high field nuclear magnetic resonance (NMR) spectrometers is significant in many applications. Wideband radio frequency (RF) front-ends are critical for the realization of ...multi-nuclei spectrometers. To realize such systems, wideband Transmit-Receive (TR) switches and low noise amplifiers (LNA) should be implemented at the RF front-end (FE) of the system. Most of the common designs used nowadays on NMR spectrometers are either inherently narrowband and/or of relatively high noise-figure which limit the overall system performance to a large extent. To improve upon the conventional FE performance, a new design of wideband high-power TR switch which could be devised for multi-nuclei NMR spectrometers is introduced in this brief. The developed wideband TR switch employs PIN diode switching technique and a dual-driver circuit. A prototype was constructed and experimentally characterized. The small-signal measurement results show that the switch has a bandwidth from 30 - 200MHz where the return loss is maintained below 18 dB with insertion loss of 0.09 - 0.2dB in the transmit mode and 0.11 - 0.37dB in the receive mode. It also exhibits a very high isolation of 63 - 80dB over the entire bandwidth. It is demonstrated that the switch can withstand continuous-wave RF input with power levels as high as 125 W while maintaining low insertion loss and high isolation.
Portable Real-Time Microwave Camera at 24 GHz Ghasr, M. T.; Abou-Khousa, M. A.; Kharkovsky, S. ...
IEEE transactions on antennas and propagation,
02/2012, Letnik:
60, Številka:
2
Journal Article
Recenzirano
This paper presents a microwave camera built upon a two-dimensional array of switchable slot antennas. The camera borrows from modulated scattering techniques to improve isolation among the array ...elements. The camera was designed to measure vector electric field distribution, be compact, portable, battery operated, possess high dynamic range, and be capable of producing real-time images at video frame-rate. This imaging system utilizes PIN diode-loaded resonant elliptical slot antennas as its array elements integrated in a simple and relatively low-loss waveguide network thus reducing the complexity, cost and size of the array. The sensitivity and dynamic range of this system is improved by utilizing a custom-designed heterodyne receiver and matched filter for demodulation. The performance of the multiplexing scheme, noise-floor and dynamic range of the receivers are presented as well. Sources of errors such as mutual-coupling and array response dispersion are also investigated. Finally, utilizing this imaging system for various applications such as 2-D electric field mapping, and nondestructive testing is demonstrated.
Accurate displacement measurement is critical for many applications. Recently, a variety of radio frequency-based linear displacement sensing techniques were introduced. However, the application of ...the previously proposed techniques was either not fully demonstrated toward realizing the sensor and/or they were limited in measurement range to less than 4 cm. This article introduces a fully characterized wide-range radio frequency-based contactless linear displacement sensor. The sensor consists of a short-circuited 50-<inline-formula> <tex-math notation="LaTeX">\Omega </tex-math></inline-formula> microstrip line and a movable current-sensing resonant probe. The probe accurately measures the sinusoidal magnetic field distribution along the short-circuited transmission line from a certain distance above it. The measured normalized field values are mapped to displacement using the inverse of the sinusoidal function in the postprocessing stage. The proposed technique is comprehensively validated using simulations and measurements of a compact sensor prototype operating at 727.5 MHz. Furthermore, the merits of the proposed sensor compared to the widely accepted linear variable differential transformer (LVDT) displacement transducer are highlighted here. The metrological characterization of the proposed sensor shows that it offers a very wide dynamic range of 68 mm with a standard deviation of the estimation error of less than 0.09 mm (0.13% of the full range). It is also demonstrated that the proposed sensor outperforms the commercial LVDT transducer in terms of overall displacement measurement accuracy. In general, the proposed sensor is scalable and has a theoretical dynamic range of <inline-formula> <tex-math notation="LaTeX">\lambda </tex-math></inline-formula>/2 making it suitable for a wide range of applications.
