Rectangular Metallic Cavity Research Articles

Formula for the Field Excited in a Faraday Cage With a Graphite–Epoxy Closeout

A simple, nearly exact, formula is derived for the fields excited in a rectangular metallic cavity by a plane wave incident on a graphite–epoxy (GrEpx) panel that replaces one wall. It is used to assess the accuracy of an approximate formula for the fields for the case where a GrEpx access panel covers a small aperture in a wall.

3-D-Printed Compact Bandpass Filters Based on Conical Posts

This article presents different physical arrangements of filters using conical posts as the basic element of design. The proposed resonator is similar to that of the classical combline filter, however, in this case, a conical post (truncated cone) is exploited. A hollowed enclosure is positioned on top of a rectangular metallic cavity for housing the upper part of the conical resonating post. Considering that the post upper radius is smaller than the post lower radius, an enclosure having the same dimensions as the resonating post can be taken. This results in a housing that can also work as an additional resonator for another cavity. As a result, cavities can be piled in a vertical arrangement and the conical post of each cavity is also used for housing the post of the cavity below it. Mixed vertically and/or horizontally arrangements are also feasible. More compact structures can be achieved with the possibility to obtain different footprints while maintaining similar unloaded $Q$ -factors than conventional combline filters. The structure also has the advantage of having a wider spurious-free range than the classical combline filter configuration (cylindrical post inside a rectangular cavity). Enhanced responses with higher rejections are also possible thanks to the introduction of transmission zeros. Several different filter configurations are presented in this article: 3-order filter and 4-order filter. The design procedure is explained for both of them. A 4-order filter has been manufactured using additive manufacturing techniques and measured in order to validate the proposed structure.

A low‐profile wideband planar phased array of cavity‐backed slot microstrip elements for two‐dimensional beam scanning applications

AbstractA low‐profile wideband planar phased array, working in X band and with two‐dimensional (2‐D) beam scanning characteristic is presented. In order to meet the requirements of wideband 2‐D beam scanning and low‐profile performance, a cavity‐backed slot stacked microstrip element is introduced. The array element is mainly composed of the open‐ended microstrip line printed on the bottom substrate, which backed by a rectangular metal cavity, and dual layer patches etched on the middle substrate and the top substrate, respectively. A vertical transition structure is used to feed the microstrip line and connect the active T/R module, which is similar to the coaxial probe. The thickness of the proposed element is only 4.5 mm (0.12 λL, λL is the wavelength of the lowest frequency). Based on the simulated design, an 8 × 8 planar phased array prototype has been fabricated and measured. The experimental results show that the proposed array have achieved the maximum scanning angle of ±45° in the H‐plane and ± 30° in the E‐plane across the frequency range of 8 ~ 12 GHz. Therefore, the proposed array can be used as a sub‐array of larger low‐profile wideband phased arrays for 2‐D beam scanning applications, and also validate the introduced design concept.

A novel dual‐mode patch antenna with pattern diversity and beam‐tilting for aircraft applications

A dual-mode patch antenna with pattern diversity that is beam-tilted in a specific direction is presented. By placing a rectangular metal cavity below the circular patch and simultaneously shorting one end of the patch, the antenna produces tilted beams for dual-mode radiation patterns. One pattern is excited using a proximity-fed L-shaped probe that generates a beam with a tilt angle of 25° from the broadside direction. The second pattern is excited using a coplanar waveguide (CPW)-based feeding network that generates two beams with a tilt angle of θmax = ±45° in the directions of ϕmax = 70° and − 70°. The tilt angle can be varied by adjusting the metal cavity's length. A prototype antenna for operation at 2.38 GHz was fabricated and measured. The results indicate that the overlapped bandwidth (|S11| < −10 dB) for the two patterns is 330 MHz (2.22-2.55 GHz). The measured peak gains for the two patterns are 6.74-6.94 dBi and 5.82-6.74 dBi, respectively. The isolation between the two ports is 18 dB.

Localization of Electromagnetic Interference Sources Using a Time-Reversal Cavity

In this article, we propose and implement a novel technique to locate electromagnetic interference (EMI) sources using the concept of time-reversal (TR) cavity. We show in an intuitive manner that reflections from the surfaces of a cavity can emulate an infinite number of sensors in the TR method. In order to locate EMI sources, the equipment under test (EUT) is placed in a rectangular metallic cavity, of suitable dimensions according to the considered frequency band and the EUT size, equipped with a simple monopole or dipole antenna. We demonstrate that by using only one sensor, we are able to locate EMI sources by taking advantage of the focusing properties of a TR cavity. The entropy criterion is applied to obtain the focusing time slice in which the maximum electric field determines the location of the EMI source. Both 2- and 3-D numerical simulation schemes are deployed to demonstrate the ability of the proposed technique. The validity of numerical simulations is tested against frequency-domain measurements. Compared with the conventional EMI tests in anechoic chambers and scanning methods, the proposed technique represents a simpler and cost-effective test method requiring only one sensor (a monopole or dipole antenna).

Miniaturized suspended strip-line bandpass filter based on spoof surface plasmon polaritons

In this letter, we propose the design of miniaturized suspended strip-line (SSL) filters based on spoof surface plasmon polariton (SSPP), a sub-wavelength mode confined tightly around artificial structures. To avoid using high-density lossy dielectric fillings, we place a periodic corrugated metallic strips (PCMS) structure in a rectangular metallic cavity. Two probes are positioned near the two ends of PCMS structure. Since PCMS structure support SSPP with shorter wavelength, it can be treated as low-loss artificial dielectrics with high permittivity εr equivalently. The cut-off frequency f lower of waveguide modes in the cavity will be reduced, which, plus the cut-off frequency f upper of SSPP, will produce a pass band between f lower and f upper. Due to high εr, low insertion loss and light weight of the PCMS structure, miniaturized band-pass filters can be implemented using such a configuration. We demonstrated a prototype operating a bandpass filter in 2.7–4.6 GHz. The cross-section of cavity is reduced by more than 75%. The filter is with quite low insertion loss only 0.1–0.3 dB. Both simulation and measurement results verify this design. This work provides an alternative to miniaturized, light-weight, high-efficiency SSL filters.

Tri‐band dual‐polarised omnidirectional antenna with high isolation for unmanned aerial vehicle applications

A new tri-band dual-polarised omnidirectional antenna is proposed. The dual-polarised antenna consists of a metal cuboid body with a vertical slot for horizontal polarisation (HP) and a rectangular back metal cavity with two folded horizontal slots for vertical polarisation (VP). A metal HP feedline is employed to coupling feed the vertical slot while a metal VP feedline is used to excite the two horizontal slots. Due to the coupling feed and the orthogonality between the vertical and horizontal slots, the dual-polarised antenna features three bands and a high isolation. Experimental results show that the tri-band dual-polarised antenna covers the Chinese Unmanned Aircraft System bands (840.5–845, 1430–1444 and 2408–2440 MHz) with reflection coefficients 32 dB. Good omnidirectional radiation patterns are observed for both HP and VP.

A Circularly Polarized Cavity-Backed Slot Antenna With Enhanced Radiation Gain

A class of circularly polarized (CP) cavity-backed slot antennas with enhanced gain is formed up. All the proposed antennas are implemented in a single rectangular metal cavity. One slot is formed at the bottom side of this cavity as a feeding slot to excite two orthogonal resonant modes. The slot antenna is then constituted at the opposite side of the feeding slot to radiate electromagnetic wave. A two-element array is further implemented to improve the radiation gain with 3 dB enhancement without size increment of the original antenna. Finally, two CP cavity-backed slot antennas are fabricated and tested for experimental verification of the proposed design methodology. A good agreement between measurement and simulation shows the feasibility of the proposed cavity-backed slot antenna.

Triple-mode wideband bandpass filter using simple perturbation in metallic-loaded rectangular waveguide cavity

ABSTRACTThis paper presents a simple perturbation technique using an off-centered metal cylinder in rectangular waveguide cavity to realize a triple-mode wideband bandpass filter. A TM mode along with two degenerate hybrid modes namely HM+ and HM-, are excited by an off-centered perturbation in a single rectangular metal cavity. The filter operates at central frequency of 2.4 GHz with fractional bandwidth of 58%. Finally, the filter is fabricated using brass. Measured results are in good agreement with the simulated results.

Quasi-planar K-band push-push low phase noise oscillator stabilized by cavity resonator

The results of developing a K-band (24 GHz) push-push low phase noise transistor oscillator have been presented. This oscillator is stabilized by a rectangular resonant metallic cavity. The power level of output signal is −9.5 dBm, the fundamental harmonic suppression is 21 dB. Single sideband (SSB) phase noise spectral density of −98 dBc/Hz at 10 kHz and −128 dBc/Hz at 100 kHz offset from the carrier frequency is at the level of dielectric resonator oscillators (DRO) scaled to the same frequency. The oscillator features a compact size, low cost quazi-planar design and it is built using commercially available off the shelf parts.

Development of a wideband compact leaky wave cavity antenna

As operating frequencies decrease, the aperture size of leaky wave antennas increases significantly – rendering them unsuitable for many sophisticated applications requiring small-sized communication antennas. In this article, a compact leaky wave cavity antenna with wide impedance bandwidth, using tapered cavity with substrate integrated waveguide is proposed. The antenna consists of a substrate and a rectangular metallic cavity fed by an L-shaped feed element. The metallic strips are placed along the sides of the substrate to fabricate a substrate integrated waveguide. The cavity is tapered to steer the beam in the desired direction. The tapering of the cavity causes the placement of the L-shaped feed element near the back wall of the cavity, producing input impedance mismatching. This problem of input impedance mismatching is resolved by the substrate integrated waveguide. It is demonstrated that the proposed antenna is compact (2λ0), and is wideband with voltage standing wave ratio (VSWR) bandwidth of 24% for 2:1 VSWR and a gain of 8.4 dBi. The experimental results for the designed antenna are in close agreement with the simulation results. The proposed antenna can be utilized in different wireless applications such as mobile communications, road vehicle communications and other applications.

Long Range UHF RFID Tag with a Rectangular Metallic Cavity Structure

A long range UHF RFID tag with a rectangular metallic cavity structure is proposed for various applications with metallic objects. The proposed tag consists of a rectangular metallic cavity structure and a folded dipole antenna which is located on top of the cavity. The tag is designed for Korean UHF RFID band(910~914 ㎒) and the bandwidth, which satisfies the-10 ㏈ input reflection coefficient requirement, is approximately 1.3 %(904~916 ㎒). Measurement demonstrates that the proposed tag shows long reading range up to 15 m when it is placed on a metallic plate.

Spectral Efficiency for MIMO UWB Channel in Rectangular Metal Cavity

Wireless communication in confined metal environment such as rectangular metal cavity has attracted more and more attentions recently. The channel characteristics in such an environment are different from those in the traditional wireless communication environments: extremely rich multipath components make communication very challenging. Multiple input multiple output (MIMO) plus ultra-wideband (UWB) technique is promising for wireless communication in confined metal environment, since it can fully employ radio resources not only in space domain but also in frequency domain. This paper considers the fundamental limit about MIMO UWB channel in rectangular metal cavity when different spectrum-shaping schemes such as water filling, constant power water filling, time reversal, channel inverse, constant power spectrum density and minimum mean square error are employed at the transmitter. Meanwhile, the measured channel transfer function is used in this paper for analysis.

무선통신용 초소형 대역통과 필터의 설계

본 논문은 무선통신 시스템에 사용되는 저 손실 소형 대역통과 필터를 새로운 프로브 구조를 적용하여 설계 제작하였다. 필터의 저 손실 특성을 위해 Q값이 높은 Ba(Co, Nb)O₃계 세라믹 유전체 공진기를 사용하였으며, TE<SUB>01δ</SUB> 모드의 공진을 이용하여 금속 캐비티의 도체손실 영향을 줄였다. 소형화를 구현하는 방법으로는 캐비티의 양옆의 공간을 줄이도록 정사각형 캐비티의 코너 공간을 적극 활용하였으며, 12×12×8[mm]의 초소형 필터를 제작하였다. 제작된 소형 필터의 주파수특성을 측정한 결과, 중심주파수 f?는 9.95358[GHz], 삽입손실은 -1.9[dB], 3[dB]_대역폭은 14.9[MHz], 부하Q는 664로 저손실 대역통과 필터의 특성을 만족하고 있다.

Modeling of microwave applicators with an excitation through the wave guide using TLM method

In this paper, a real microwave applicator with a wave guide used to launch the energy from the source into the cavity is analyzed using 3D TLM method. In order to investigate the influence of the positions and number of feed wave guides to the number of the resonant modes inside the cavity, obtained results are compared with analytical results and results obtained by using TLM software with an impulse excitation as well. TLM method is applied to the both empty and loaded rectangular metallic cavity, and a very good agreement between simulated and experimental results is achieved.

Study of distributions of modes and plane waves in reverberation chambers for the characterization of antennas in a multipath environment

AbstractA rectangular metallic cavity is known to support a number of resonant cavity modes. Each of these modes can be described as a sum of eight plane waves incident from different angles. This paper studies how these plane waves are angularly distributed in space, which is of interest when the cavity is used to simulate multipath environment. The results show that the angular distribution in space is uniform provided that the three linear dimensions of the chamber are sufficiently large, and do not deviate too much from each other. As an example, two rectangular cavities with dimensions 1 m×0.8 m×1 m and 5.5 m×2.5 m×3.5 m are analyzed in detail, and are shown to have uniform plane‐wave distributions. We also demonstrate how the chamber geometry may be chosen in order to weight the angular plane‐wave distribution in the elevation plane. A result of the study is that we detect a 25 MHz frequency band with very few modes in a small chamber designed for use with reduced accuracy in the GSM 900 MHz band. We also propose how this chamber can be modified to obtain uniform mode distribution over this frequency band. © 2001 John Wiley &amp; Sons, Inc. Microwave Opt Technol Lett 30: 386–391, 2001.