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A high‐performance dual‐polarized horn antenna for a 5G millimeter wave compact antenna test range system (CATR) is proposed in this article. The feed antenna is mainly composed of a double‐ridged waveguide junction orthomode transducer (OMT), mode converter, and corrugated horn antenna. Among them, the OMT is the key device for the feed antenna to achieve dual polarization characteristics, and adopts a modular design method to apply the multi‐section impedance transformer in the vertical and horizontal polarization channels with good transmission characteristics. The corrugated horn antenna generates a symmetrical radiation pattern mainly in six corrugated slots. The proposed dual‐polarized corrugated horn antenna impedance matching bandwidth (VSWR < 2) is 24–50 GHz. Moreover, the measured gain is 10–12 dBi, and the measured cross‐polarization level is less than −30 dB within the operating frequency range. Meanwhile, the half‐power beamwidth radiation pattern in the whole operating band has a good symmetry and the beamwidth in both E‐ and H‐plane remains stable. As a practical application, the designed antenna is used as the feed of the CATR system. The measured results show that the amplitude distribution in the quiet zone (QZ) is within ±1 dB, the phase distribution is within ±8°, and the cross‐polarization isolation is better than 27 dB. The performance of the QZ is conducive to the use of the CATR system. [ABSTRACT FROM AUTHOR]

In this letter, to verify that the shaped beam feed can enhance the aperture usage efficiency of a single‐offset parabolic reflector compact antenna test range (CATR), a shaped beam horn is proposed. First, we obtain the radiation intensity function of the feed. Then, a coaxial cavity horn feed with a half‐ring is designed to shape the illumination that reaches the main reflector. Measured results demonstrate that, with no edge treatment, the quiet zone size can be up to 75% of the main reflector diameter under 1.20 dB amplitude variations and 12° phase variations at 102.40 GHz, and 70% aperture usage efficiency ranging from 102 to 103 GHz with phase variations less than 12° and amplitude variations less than 1.40 dB. The design verifies that the shaped beam feed can enhance the aperture usage efficiency of a single‐offset CATR. [ABSTRACT FROM AUTHOR]

Traditional multi-channel active noise control (MCANC) is based on adaptive filtering and usually uses a separate control unit for each channel. This paper introduces a deep learning based approach for multi-channel active noise control (ANC). The proposed approach, called deep MCANC, encodes optimal control parameters corresponding to different noises and environments, and jointly computes the multiple canceling signals to cancel or attenuate the primary noises captured at error microphones. A convolutional recurrent network (CRN) is employed for complex spectral mapping where the summated power of error signals is used as the loss function for CRN training. Deep MCANC is a fixed-parameter ANC approach and large-scale multi-condition training is employed to achieve robustness against a variety of noises. We explore the performance of deep MCANC with different setups and investigate the impact of factors such as the number of loudspeakers and microphones, and the position of a secondary source, on ANC performance. Experimental results show that deep MCANC is effective for wideband noise reduction and generalizes well to untrained noises. Moreover, the proposed approach is robust against variations in reference signals and works well in the presence of nonlinear distortions. [ABSTRACT FROM AUTHOR]

A compact antenna test range (CATR) system based on a planner stepped‐edged reflectarray antenna is proposed in this article. The parameters of the reflectarray antenna are determined by the design method of a single reflector system. Physical Optics (PO) method is used to calculate the unit phase of the reflectarray. The performance of the quiet zone is improved by optimizing the array shape. A 4320‐element reflectarray antenna with a dual‐ring structure is proposed and fabricated. The measured results show that the amplitude distribution of the designed reflectarray compact range is within ±1 dB, the phase distribution is within ±10°, and the cross‐polarization isolations are greater than 24 dB in the region of 50% at 10 GHz. The performance of the quiet zone is favorable for the usage of CATR systems. [ABSTRACT FROM AUTHOR]

Traditional active noise control (ANC) methods are based on adaptive signal processing with the least mean square algorithm as the foundation. They are linear systems and do not perform satisfactorily in the presence of nonlinear distortions. In this paper, we formulate ANC as a supervised learning problem and propose a deep learning approach, called deep ANC, to address the nonlinear ANC problem. The main idea is to employ deep learning to encode the optimal control parameters corresponding to different noises and environments. A convolutional recurrent network (CRN) is trained to estimate the real and imaginary spectrograms of the canceling signal from the reference signal so that the corresponding anti-noise can eliminate or attenuate the primary noise in the ANC system. Large-scale multi-condition training is employed to achieve good generalization and robustness against a variety of noises. The deep ANC method can be trained to achieve active noise cancellation no matter whether the reference signal is noise or noisy speech. In addition, a delay-compensated strategy is introduced to solve the potential latency problem of ANC systems. Experimental results show that deep ANC is effective for wideband noise reduction and generalizes well to untrained noises. Moreover, the proposed method can achieve ANC within a quiet zone and is robust against variations in reference signals. [ABSTRACT FROM AUTHOR]

Over-the-air (OTA) measurement is mandatory for 5G mm-wave wireless devices. The compact antenna test range (CATR) is the baseline method in the current version of TR 38.810 in 3rd generation partnership project (3GPP) and cellular telecommunications industry association (CTIA) millimeter-wave (mm-Wave) test plan. For CATR, both amplitude and phase variations inside the quiet zone (QZ) could affect the final OTA results significantly and hence need to be characterized carefully. Especially in the phase validation of QZ, even slight misalignments between sampling plane and incident plane wavefront due to the limited precision of the positioner or tolerance in antenna fixture could result in large phase variations, which is not the true phase property of QZ. This letter presents a method to remove the effect of the angular error due to misalignment when measuring the phase variation inside QZ. By adopting the proposed method to the measured phase data, any angular error due to misalignment with respect to the incident plane wavefront will be eliminated mathematically, leaving the true phase variations of QZ only. In the meanwhile, the proposed method can alleviate the requirements of fixture manufacture and alignment precision and reduce the test cost. [ABSTRACT FROM AUTHOR]

Amplitude and phase distribution inside the quiet zone (QZ) of a far-field antenna measurement chamber are important indicators for the quality of antenna measurements therein. Both amplitude and phase can be further subdivided into intuitive quality parameters such as linear taper, parabolic taper, and ripple. In order to retrieve these parameters from QZ spherical near-field measurements, the transmission formula is adapted to the case where the output signal of a virtually positioned output probe-antenna can be calculated on arbitrary locations inside the QZ. The output probe-antenna can be a measured or theoretically defined antenna and can be rotated in any direction of interest. This paper will show that this method provides similar results as industry standard linear field-probing by comparing amplitude taper and ripple extracted from both measurements. Further the advantages of using QZ spherical near-field scanning (QZSNFS) in combination with the adapted output transmission formula will be shown by calculating multiple projections not available by standard field-probing. [ABSTRACT FROM PUBLISHER]

The separation of South America from Africa during the Cretaceous is poorly understood due to the long period of stable polarity of the geomagnetic field, the Cretaceous Normal Superchron (CNS, lasted between ∼121 and 83.6 Myr ago). We present a new identification of magnetic anomalies located within the southern South Atlantic magnetic quiet zones that have arisen due to past variations in the strength of the dipolar geomagnetic field. Using these anomalies, together with fracture zone locations, we calculate the first set of magnetic anomalies-based finite rotation parameters for South America and Africa during that period. The kinematic solutions are generally consistent with fracture zone traces and magnetic anomalies outside the area used to construct them. The rotations indicate that seafloor spreading rates increased steadily throughout most of the Cretaceous and decreased sharply at around 80 Myr ago. A change in plate motion took place in the middle of the superchron, roughly 100 Myr ago, around the time of the final breakup (i.e., separation of continental–oceanic boundary in the Equatorial Atlantic). Prominent misfit between the calculated synthetic flowlines (older than Anomaly Q1) and the fracture zones straddling the African Plate in the central South Atlantic could only be explained by a combination of seafloor asymmetry and internal dextral motion (<100 km) within South America, west of the Rio Grande fracture zone. This process has lasted until ∼92 Myr ago after which both Africa and South America (south of the equator) behaved rigidly. The clearing of the continental–oceanic boundaries within the Equatorial Atlantic Gateway was probably completed by ∼95 Myr ago. The clearing was followed by a progressive widening and deepening of the passageway, leading to the emergence of north–south flow of intermediate and deep-water which might have triggered the global cooling of bottom water and the end for the Cretaceous greenhouse period. [ABSTRACT FROM AUTHOR]

Traditionally, tapered chambers are constructed using a square based pyramidal shaped taper. The taper is then shaped into an octagon and finally transformed into a cylindrical launch section. This approach is related to the manufacturability of different absorber cuts. This paper introduces a chamber where the conical shape of the launch in continued throughout the entire length of the tapered chamber. The results of the free space VSWR test over a 1.5 m diameter quiet zone (QZ) are presented at different frequencies. The conical taper appears to have a better illumination wave front and better QZ levels even at frequencies above 2 GHz than the standard traditional approach. This design was implemented in Singapore and the actual chamber was designed to have a secondary near field range for planar and spherical scans. As with all antenna chambers, as the frequency increases, the usable or far field illuminated QZ is reduced. At a 12 m distance from the feed to the turntable, the quiet zone at 8 GHz is reduced to 45 cm. The chamber includes a near to far field range to allow the use of the chamber at higher frequencies when testing electrically large antennas. Another solution implemented to extend the quiet zone at high frequency is to use a large dielectric lens to improve the phase distribution of the field. A light weight, broadband lens with a diameter of 2 m was developed by Matsing Pte Ltd. The parameters of the lens were specially customized for the tapered chamber built. The RF lens, weighing just 35 kg, has a focal length of 10 m. It was installed in front of the turn table. The performance of the tapered chamber with the RF lens is presented. The usable far field QZ was increased by using a dielectric RF lens that allows for electrically larger antennas to be measured in the tapered range of the chamber. [ABSTRACT FROM AUTHOR]

Abstract: Most active noise control (ANC) systems are designed and analyzed in ideal sound fields, where ANC performances are predictable with acceptable accuracies. In many ANC applications sound fields are non-ideal with significant differences between real ANC performances and theoretical predictions. If one uses an ideal model to optimize locations of actuators or error sensors for an ANC system in a non-ideal sound field, the actual quiet zone is inevitably different from its theoretical prediction. It is desired that users of ANC systems can tune quiet zones by adjusting ANC configurations, such as locations of secondary sources or error sensors. Model-independent ANC (MIANC) systems are preferred for this purpose. In this study, a model-independent ANC system is improved, implemented and applied to create a quiet zone in a non-ideal sound field. Users of the system can adjust locations of actuators or error sensors to tradeoff between sizes of quiet zones and levels of noise attenuations. Experimental results are presented to demonstrate observations and effects of quiet zone tuning using the improved ANC system. [Copyright &y& Elsevier]

Two complementary numerically efficient frequency-domain methods for locating stray-signal sources in anechoic chambers are investigated and applied in combination to actual measurement data. Both methods use single-frequency near-field data collected on a planar surface and process them to reconstruct field values (images) elsewhere. The first method, which is based on the fact that the probe output satisfies the Helmholtz equation, uses plane waves to backpropagate the scan-plane data and is well suited for fast-Fourier-transform (FFT)-based rapid reconstruction of images on planar surfaces parallel to the scan plane. The second method uses the simple spherical-wave focusing technique and is flexible, in that, it can be used to generate images on either planar or nonplanar surfaces from the data collected on either planar or nonplanar surfaces. When data and image points are both located on a regular grid, the method can be implemented using the FFT-based fast convolution technique. Both methods include a spatial filter for isolating selected plane-wave spectrum components. The two methods are used in combination to successfully locate the strong multiple-bounce stray signals that degrade the quiet zone of a near-field bistatic radar cross-section facility. Subsequent scan data confirm that the suppression of these stray signals indeed substantially improves the quality of the quiet zone. The spherical-focusing method is also used to evaluate the effectiveness of the various absorber configurations applied to selected edges of the reflector to control edge-diffracted fields. It is shown that the reduction of the edge-diffracted fields further improves the quiet zone. [ABSTRACT FROM AUTHOR]

A compact radar cross section (RCS) test range based on a phase hologram has been developed for scale-model measurements. The phase hologram converts the feed-horn radiation to a plane wave needed for RCS determination. The measurements are performed at 310 GHz using continuous-wave operation. A monostatic configuration is realized using a dielectric slab as a directional coupler. The main advantage of a scale-model RCS range is that the dimensions of radar targets are scaled down in proportion to the wavelength. Therefore, RCS data of originally large objects can be measured indoors in a controlled environment. Test objects such as metal cylinders and simplified targets have been measured. The feasibility of the phase-hologram RCS range has been verified. The operation and measurement results of the monostatic measurement range are reported here. A comparison with simulated results is also included [ABSTRACT FROM PUBLISHER]

The quality of the sonic environment in major cities is becoming increasingly important owing to growing concerns regarding noise pollution and the need to preserve the soundscape as intangible cultural heritage. The objective of the present study is to demonstrate the use of a smartphone as a platform to collect sound data and generate a sound map based on soundwalks in major European cities. The sonic environments of the five major cities namely Paris, London, Amsterdam, Prague and Milan are presented and compared with those of two smaller European cities: Trondheim and Aachen. Among these seven European cities, Aachen is the quietest city, with equivalent and maximum sound pressure levels (SPLs) of about 66.5 dBA and 85.8 dBA, respectively. [ABSTRACT FROM AUTHOR]