Full Anechoic Chamber Research Articles

Broadband All-Metal Vivaldi Array Antenna with Pyramidal-Shaped Wings for LEO Satellite Applications

In this paper, we propose an all-metal Vivaldi antenna with pyramidal-shaped conductive wings for use in satellite signal intelligence applications. The inner metal Vivaldi antenna consists of radiating flares and a transition part between the feeder and the flares. The curvature of the inner flares is optimized, while the outer edges of the radiating flares are connected to the pyramidal-shaped wings to obtain a higher antenna gain over the entire operating frequency band. To verify the antenna’s feasibility, performance aspects such as the reflection coefficient, the radiation patterns, and the boresight gain are measured in a full anechoic chamber. The fractional bandwidth of the proposed antenna is 54%, while the boresight gain is greater than 7.3 dBi in the frequency range from 8 GHz to 12 GHz. To examine array performance aspects such as the total gain and beam steering, the proposed Vivaldi antenna is extended to a 4 × 1 linear array configuration. When the main beam is steered from 0° to 15°, the maximum gain is varied from 14.5 dBi to 13.7 dBi, while the side lobe level is decreased from 11.2 dB to 6.3 dB.

Design of an S/X-Band Single-Layer Shared-Aperture Array Antenna Using a Mutual Complementary Configuration

This paper proposes an S/X-band single-layer shared-aperture array antenna for the multifunction radars of military ships. A unit cell of the proposed antenna consists of one S-band element and four X-band elements. The S- and X-band elements are printed on the same layer to prevent a blockage effect by upper elements in the stacked shared-aperture antenna. Herein, the S-band element has a mutual complementary configuration for the X-band elements. In addition, the unit cell of the proposed antenna is designed in a symmetrical structure, which can be flexibly extended to a full array configuration. To verify the antenna feasibility, antenna performances are measured in a full anechoic chamber. The fractional bandwidths of the S- and X-band elements are 13.6% and 13.4%, respectively. Moreover, in the 2 × 2 array configuration, the S-band array gain in the bore-sight direction varies from 5.4 dBi to 3.5 dBi when the main beam is steered from 0° to 45°. Under the same conditions, the measured X-band array gain in the bore-sight direction decreases from 13.4 dBi to 11.6 dBi.

Shielding Effectiveness of a PC Case Using Three-Axis Electro-optic Sensors

This paper presents a measurement method for the shielding effectiveness (SE) of a personal computer (PC) case using three-axis electrooptic sensors and a vector network analyzer (VNA). The SE is obtained by taking the difference between the logarithmic values of the ratios of transmitted power to the input power for conditions with and without the PC case. The SE measurements versus the incident angle and polarization of incident electromagnetic fields are performed in a fully anechoic chamber (FAC) in the frequency range of 1 GHz to 4 GHz. A computer simulation is conducted to compare the experimental and numerical results. Additionally, we measured the SE of the PC case in a reverberation chamber (RC). The SE values of the PC case for the three axes in the case of FAC and RC are within 4 dB. The results show that this SE measurement technique, using electro-optic sensors and a VNA, is useful for both FAC and RC.

Design of a Dual-Polarization All-Metal Vivaldi Array Antenna Using a Metal 3D Printing Method for High-Power Jamming Systems

This paper proposes an all-metal Vivaldi array antenna with a wide-angle impedance matching (WAIM) layer for high-power jamming systems. To reduce fabrication complexity and time, the proposed array antenna is manufactured using a metal 3D printing method. The Vivaldi unit cell, composed of a radiating flare part and an inner cavity, is extended into an 8 × 8 array with a ±45° slant configuration. To further enhance the beam steering angle, the WAIM layer is placed on top of the proposed array antenna. The performances of the proposed array antenna, such as its active reflection coefficients (ARC), gains, and array radiation patterns, are investigated in a full anechoic chamber. At a steering angle of (θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 45°, ϕ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 25°), the measured and simulated average ARCs of the center element (Port 36) with the WAIM layer are –13.2 dB and –18.5 dB, respectively. At 4 GHz, the measured and simulated bore-sight gains of the proposed array antenna are 19 dBi and 20.6 dBi, respectively. In addition, the measured and simulated bore-sight gains for the (θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 45°, ϕ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 0°) steering angle in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">zx</i> -plane are 18 dBi and 21 dBi, respectively. In the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">zy</i> -plane, bore-sight gains for the (θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 45°, ϕ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 0°) steering angle are 19.3 dBi by measurement and 19.1 dBi by simulation. These results demonstrate that the proposed array antenna is suitable for high-power jamming systems because stable bore-sight gains are observed even at wide steering angles without unwanted grating lobes.

2.45/5.8 GHz 무선전력전송 시스템에 적용 가능한 광대역 고이득 인쇄형 안티포달 비발디 안테나 설계

This paper proposed a broadband, high-gain antipodal Vivaldi antenna for 2.45 GHz and 5.8 GHz wireless power transmission systems. The proposed antenna consists of a radiator with two flares and diagonal slots which are inserted at the edges of the radiator to improve the bore-sight gain. The diagonal slots reduce radiation gain in undesired directions, thus enhancing the bore-sight gain by 4.1 dB at 2.45 GHz. The directors between two upper flares concentrate the E-field, resulting in increased bore-sight gain at 5.8 GHz. The performance of the proposed antenna is measured in a full anechoic chamber, and it is confirmed that reflection coefficients are less than −10 dB in ISM bands, with bore-sight gains of 8.31 dBi and 13.1 dBi at 2.45 GHz and 5.8 GHz, respectively.

Design of a Compact Indirect Slot-Fed Wideband Patch Array with an Air SIW Cavity for a High Directivity in Missile Seeker Applications

This research proposes a compact indirect slot-fed wideband patch array antenna for a missile seeker application. The proposed single antenna consists of three dielectric layers for a radiator, an air substrate-integrated waveguide (SIW) cavity, and an indirect feeding network. The rectangular patch is used as a radiator on the first substrate layer, and the air SIW cavity (ASIWC) is employed to obtain high directivity and low mutual coupling characteristics in the second substrate layer. In the third layer, an indirect feeding structure is used to achieve the wideband characteristics in the Ka-band. The single element is extended to a 4 × 1 linear array with fabrication, and the fabricated array characteristics are measured in a full anechoic chamber. The measured operating fractional frequency bandwidth is 9.2%, and the measured array gain is 11.7 dBi at the bore-sight direction (θ0 = 0∘).

Shielding Effectiveness Measurements of Drywall Panel Coated with Biochar Layers

Shielding against electromagnetic interference (EMI) is a critical issue in civil applications generally solved with metal screens. In recent years, the properties of many composite materials filled with carbon nanotubes or graphene or materials with a carbon-based coating have been analysed with the aim of using them for electromagnetic shielding applications. Among other carbon materials, biochar, derived from biomass and characterized by high carbon content, emerges as a sustainable, renewable, environmentally friendly, and inexpensive material. In this paper, commercial biochar thermally treated at 750 °C is used to coat with several layers common building components such as drywall panel. Shielding effectiveness is measured in the frequency band 1–18 GHz for normal incidence and skew angles 10, 20 and 30 deg in a full anechoic chamber with double ridged, vertically and horizontally polarized broadband horn antennas. The results show that the proposed biochar-coated drywall panels provide a good shielding effectiveness compared to similar solutions, with the advantage of a less expensive and easier to realize building material.

Design of a High-Durability X-Band Patch Antenna with a CPW Feeding Network Based on a Durability Evaluation Analysis

In this paper, we propose a high-durability X-band patch antenna with a coplanar waveguide (CPW) feeding network that can directly connect the upper antenna and the lower transmitting receiver modules without additional cabling. To improve the durability of the antenna, both the sub miniature push-on (SMP) connector and the feed-pin are separated through the CPW layer. This separated structure can minimize the deterioration of the antenna performance when the unwanted movement of the SMP connector occurs from external shocks. To verify the design feasibility, the reflection coefficient and radiation patterns of the proposed antenna are measured in a full anechoic chamber. The reflection coefficient of the proposed antenna is −27 dB at 10 GHz, and the operating frequency bandwidth (|Γ| &lt; −10 dB) is 4.7% (9.82~10.29 GHz) in X-band. The proposed antenna has a maximum gain of 5.7 dBi at the bore-sight direction. In addition, the durability evaluations of the proposed design according to unwanted SMP connector movements provoked by external shocks are investigated using Monte Carlo simulations. The results demonstrate that the proposed high-durability antenna design is suitable for military ship applications that involve exposure to various external shocks.

Design of a Polarization-Selective EM Transparent Mesh-Type E-Shaped Antenna for Shared-Aperture Radar Applications

In this paper, we propose a polarization-selective electromagnetic (EM) transparent mesh-type E-shaped antenna unit-cell in a shared aperture. The proposed antenna unit-cell, which can be expanded to a larger array in a modular way, has one S-band antenna on the upper layer and nine X-band antennas on the lower layers. The simple E-shaped structure, which has a low profile with a good bandwidth, is used for the antenna elements. However, due to the limited aperture size of the stacked configuration, the lower-layer elements can be physically blocked by the upper-layer element. To reduce this blockage effect, the S-band element is rotated 90 degrees with respect to X-band elements so that the polarizations between the S- and X-band elements are perpendicular to each other. Moreover, to minimize performance degradation due to the blockage effect, a mesh structure is applied for S-band elements for EM transparent characteristics, thereby improving EM transparency from −30 dB to −1.5 dB. The extended via cavity wall is also employed outside the nine X-band elements to minimize the mutual coupling and to reduce antenna size. To confirm the effectiveness of the proposed design, the proposed antenna unit-cell is fabricated, and the radiation characteristics are measured, in a full anechoic chamber. The average bore-sight gains in the S- and X-band are 5 dBi and 4.5 dBi, respectively. The results confirm that the proposed design is suitable for shared-aperture radar applications.

Design of a Printed 5G Monopole Antenna With Periodic Patch Director on the Laminated Window Glass

This letter proposes a printed fifth-generation (5G) monopole antenna with a periodic patch director that can be applied to a laminated window glass of a vehicle. The proposed monopole antenna is printed on the laminated window glass, which does not require additional mounting space. The rectangular disk is loaded at the end of the monopole to improve a bore-sight gain. To further improve the gain characteristic, the periodic patch director elements are arranged with optimized array spacing. To verify the antenna performances, such as reflection coefficients and radiation patterns, the proposed antenna is fabricated and measured in a full anechoic chamber. The results demonstrate that the proposed monopole antenna with the periodic patch director is suitable for applying in vehicle 5G communication band of n257.

Interlaboratory comparison of radiated emission measurements using a tubular dipole

This paper presents an interlaboratory comparison of radiated emission measurements in the frequency range of 30-1000 MHz. A tubular dipole was specifically designed and employed as a reference emitting source. The most important for a tubular dipole is stability in the testing process. The stability is not the performance of the sample, but the emission signal of the sample is stable. In addition, two ways of determining the reference value of the electromagnetic field strength are considered. The first reference value is obtained by using robust analysis. It is a robust average value that is calculated by averaging the measurement results provided by the participating testing laboratories. The other reference value is obtained through the simulation-experimental results of the tubular dipole in the semi-anechoic chamber or full anechoic chamber, for horizontal and vertical polarizations and 3 m distance measurement, respectively. In addition, this value is assigned by the coordinator. Measurement results are compared using the robust z-scores and -scores, respectively.

Subjective acoustic survey of Korean traditional wind instruments, piri and daegeum, in a concert hall using auralisation techniques

In this study, acoustics of piri and daegeum, which are representative traditional Korean wind instruments, was investigated objectively and subjectively. The acoustic directivity patterns of piri and daegeum were measured in a full anechoic chamber. A subjective acoustic survey of piri and daegeum solo performances was conducted with 60 music students using an auralised concert hall with a volume of 18,838 m3. The sound produced by piri had extensive high-frequency harmonics and strong forward and downward directivity. In addition to a strong lateral and upward directivity, the sound produced by daegeum exhibited more explicit fundamental notes than those produced by piri. The reverberance, loudness, and envelopment of piri and daegeum were affected by early decay time (EDT), sound pressure level (SPL), and lateral energy fraction (LF80), respectively. The clarity of piri showed no explicit relationship with the clarity index (C80), but the clarity of daegeum was affected by the C80. Room acoustical conditions around a reverberation time of 2.6 s were preferred for the piri solo. However, for the daegeum solo, room acoustical conditions around a reverberation time of 1.7 s were preferred. The overall impression of piri was highly correlated with loudness and mid-treble balance. However, the overall impression of daegum did not show a strong linear correlation with other subjective attributes, such as piri (r > 0.6).

Experimental Research on Noise Load Characteristics of Supersonic Jets in Rectangular Nozzles with Different Mach Numbers

Aiming at the jet noise problem of the rectangular supersonic nozzle, rectangular nozzle test models with Mach numbers of 1.35 and 1.65 were designed and processed. Using the jet noise test platform in a full anechoic chamber, the nozzle supersonic jet noise characteristic test was carried out. The test results show that the surface noise load of the model gradually increases along the nozzle axis; the unsteady flow field structure at the nozzle exit position has complex evolution, with strong turbulent pulsation and high noise load; the directivity trend of the far-field noise total pressure level of the two nozzles is basically the same, and the directivity is obvious in the upstream and 90° direction of the nozzles; from the far-field sound pressure spectrum, it can be seen that the far-field noise is composed of broadband noise and discrete frequency noise. The amplitude of the second order frequency varies significantly from 70° to 90° of upstream, and the fourth harmonic frequency of the whistling mode is captured in the direction of 90°.

A novel methodology for time-domain characterization of a full anechoic chamber for antennas measurements and exposure evaluation

&lt;p&gt;In this paper we present a novel methodology for time-domain characterization of a full anechoic chamber using the finite integral method. This approach is considered fast, accurate and not intensive for computer resources. The validation of this approach is carried out on CST-microwave studio for a full anechoic chamber intended for antennas measurement applications and electromagnetic exposure evaluation for cellular network. Low, medium and high gain sources are used in this study. The simulations are realized on a personal computer of medium performances (i7 CPU and 16 GB of RAM). The stability and the convergence of our approach are obtained thanks to local mesh and auto-regressive linear filtering techniques. The minimization of the simulation time is based on use of the Huygens sources in the place of the antennas. The maximum error of the chamber as well as the wave depolarization into the chamber are at one with the previous work and the catalogs of the principles chambers manufacturers for the proposed tests in this paper. The Full simulations time is about 15 hours in average.&lt;/p&gt;

Influence of span-wise coherence on the acoustic radiation in a cylinder wake

The aim of this study is to detect and visualise the influence of span-wise coherence on propagating sound waves emanating from a flow around circular cylinders with span-wise variations of the local radius. Synchronous particle image velocimetry (PIV) and microphone measurements are performed in a circular wind tunnel with a nozzle size of 0.4 m×0.4 m at a maximum flow speed of U∞ = 43m s−1 . The test section is surrounded by a full anechoic chamber of approximately 9 m×9 m×5 m.

Design of an On-Glass 5G Monopole Antenna for a Vehicle Window Glass

In this paper, we propose a design for an on-glass 5G monopole antenna for a vehicle window glass. The proposed antenna consists of a monopole resonator, an inductive line, and a co-planar waveguide (CPW), which can adjust the phase so that the current in each resonator is close to in phase. Therefore, although the vehicle window glass has a high dielectric loss, the proposed monopole with an inductive line can obtain an antenna gain that is suitable for applying to vehicle 5G communications. To verify the antenna characteristics, the reflection coefficients and the radiation patterns are measured in a full anechoic chamber. The results demonstrate that the proposed on-glass antenna is suitable for applying in vehicle 5G communications.

Loop-Shaped Patch Antenna for Conformal Arrays to Minimize the Effects of Adjacent Conducting Skin

This article proposes a novel method of designing a loop-shaped slot patch antenna using an extended cavity structure to reduce the influence of adjacent conducting vehicle skin. The proposed antenna consists of the radiating patch, loop shaped slot, and an extended cavity structure. The radiating patch is directly connected to a hybrid chip coupler to achieve a circular polarization property, and the extended cavity structure is employed to confine the near-field within the radiating patch that allows to have less influence of the conducting skin and to increase the effective permittivity of the proposed antenna. To verify the effectiveness of the proposed conformal array antenna, we fabricate 2 × 2 array antenna with and without an adjacent conducting skin, and its performances, such as bore-sight gains and 2-D radiation patterns are measured in a full anechoic chamber. The results confirm that the proposed antenna structure is suitable for elements of the conformal array, which is less affected by the conducting skin of the airframe.

Design of a Monopulse System Using a Single Patch Radiator with a Simple Multi-Mode Substrate Integrated Waveguide Feeding Network

This paper proposes the design of a single radiator monopulse antenna with a substrate integrated waveguide (SIW) multi-mode feeding system to reduce the aperture size and simplify the feeding structure. The proposed antenna can effectively reduce the overall system size by using a single patch radiator, compared to conventional systems that require multiple radiators. In addition, to simplify the structure of the pattern comparator we use a SIW multi-mode feeding system with TE10 and TE20 modes. To verify the feasibility, the patch antenna with the SIW multi-mode feed is fabricated, and its antenna characteristics of reflection coefficients, mutual coupling, and radiation patterns are measured in a full anechoic chamber. The accuracy of the direction of arrival (DOA) estimation is further improved by applying the derived calibration factor to the resulting sum and difference ratio. The results demonstrate that the proposed antenna is suitable for compact and lightweight monopulse systems with the single radiator and the simple multi-mode feeding network.

High Aperture Efficiency Array Antenna for Wireless Power Transfer Applications

We propose a novel array antenna with high aperture efficiency by employing an array element operating in a high-order mode to improve the transmission efficiency of wireless power transmission applications. The proposed array element, operating at a frequency of 5.8 GHz, consists of a square patch with four metallic shorting pins, an extended cavity, and a high dielectric superstrate. The four metallic shorting pins derive the high-order operation, which can enhance the bore-sight gain, resulting in the high aperture efficiency of the array. The extended cavity structure can help further improvement the aperture efficiency and minimize the mutual coupling strength between adjacent elements. The proposed antenna element is extended to 2 × 2 and 4 × 4 arrays, resulting in aperture efficiencies of 74.2% and 80.5%, respectively. For the 2 × 2 array, maximum measured gains of 19.9 dBi in the zx-plane and 18.8 dBi in the zy-plane are observed. For the 4 × 4 array, the maximum measured gains of 24.3 dBi in the zx-plane and 24.5 dBi in the zy-plane are obtained in a full-anechoic chamber. Finally, the transmission efficiency of 6% with a distance of 0.8 m between the transmitter (Tx) and the receiver (Rx) is measured when setting up the wireless power transfer system, which consists of the Tx with the proposed 4 × 4 array and the Rx with a single element.

Design of a Small Array Antenna with an Extended Cavity Structure for Wireless Power Transmission

This paper proposes a design of a small array antenna with an extended cavity structure for wireless power transmission. The proposed array element consists of a square radiating loop, which is designed to resonate at 5.8 GHz, and an extended cavity structure to reduce the mutual coupling between adjacent elements. We derive the optimal element number in a limited space by considering the input power for each element, fabrication cost, and aperture efficiency of the system. To verify the suitability of the proposed a small array with an extended cavity structure, a 2 × 2 downscaled array antenna is fabricated and measured in a full anechoic chamber. The results confirm that the proposed antenna element with an extended cavity structure is suitable for wireless power transmission systems; the proposed array has a transmission efficiency of about 1% at a distance of 2 m when the array is applied to both transmitting and receiving antennas.