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X band

About: X band is a research topic. Over the lifetime, 3287 publications have been published within this topic receiving 23998 citations.


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Journal ArticleDOI
TL;DR: In this paper, a method is presented for determining the complex permittivity and permeability of linear materials in the frequency domain by a single time-domain measurement; typically, the frequency band extends from VHF through X band.
Abstract: In this paper a method is presented for determining the complex permittivity and permeability of linear materials in the frequency domain by a single time-domain measurement; typically, the frequency band extends from VHF through X band. The technique described involves placing an unknown sample in a microwave TEM-mode fixture and exciting the sample with a subnanosecond baseband pulse. The fixture is used to facilitate the measurement of the forward- and back-scattered energy, s21(t) and s11(t), respectively. It is shown in this paper that the forward- and back-scattered time-domain "signatures" are uniquely related to the intrinsic properties of the materials, namely, e* and ?*. By appropriately interpreting s21(t) and s11(t), one is able to determine the real and imaginary parts of ? and ? as a function of frequency. Experimental results are presented describing several familiar materials.

2,557 citations

Journal ArticleDOI
TL;DR: In this paper, a bandpass frequency selective surface (FSS) is proposed, which is made up of periodic array of metallic patches separated by thin air-gaps backed by a wire mesh having the same periodicity.
Abstract: We demonstrate a new class of bandpass frequency selective surface (FSS), the building block of which, unlike the traditional FSSs, makes use of resonant dipole and slot structures that have dimensions much smaller than the operating wavelength. This design allows localization of bandpass characteristics to within a small area on the surface which in turn facilitates flexible spatial filtering for an arbitrary wave phasefront. The proposed FSS is made up of periodic array of metallic patches separated by thin air-gaps backed by a wire mesh having the same periodicity (Ltlambda). The array of metallic patches constitute a capacitive surface and the wire mesh a coupled inductive surface, which together act as a resonant structure in the path of an incident plane wave. Like traditional FSSs, the capacitive and inductive surfaces of the proposed FSS can easily be fabricated using printed circuit technology on both sides of microwave substrates. It is shown that by cascading such bandpass surfaces in a proper fashion, any arbitrary multipole filter or non-commensurate multiband response can be obtained. The frequency response of the proposed miniaturized-element frequency selective surface (MEFSS) is demonstrated for various incident angles and it is shown that one-pole designs are less sensitive than two-pole designs to the angle of incidence. Dual band designs are also possible based on two-pole designs, but are more sensitive to incident angle than single band designs because of their larger (in terms of wavelengths) spacing. Prototypes of single-pole and dual-pole MEFSSs are fabricated and tested in a waveguide environment at X-band frequencies and excellent agreements between the measured and simulated results are demonstrated

544 citations

Journal ArticleDOI
TL;DR: In this article, a radar absorbing structure (RAS) which can support loads and absorb the electromagnetic wave has been designed by blending conductive carbon black with the binder matrix of glass/epoxy composite.
Abstract: It is an important issue not only for military purposes but also from commercial point of view, whether or not the reflective wave from an incident electromagnetic wave can be nullified. In this research, by blending conductive carbon black with the binder matrix of glass/epoxy composite, a radar absorbing structure (RAS) which can support loads and absorb the electromagnetic wave has been designed. The RAS was specially designed so as to exhibit the optimum absorptivity for X-band of (8.2–12 GHz) frequency ranges, centered at 10 GHz. Its absorbing characteristics were also investigated. Unlike other existing measurements of reflection loss using a waveguide, the reflection loss within an anechoic chamber simulating the radar cross section method of measurement was used with a plane-wave shaped incident wave. An optimized multi-layer design of RAS using the adopted material system is described in this research.

345 citations

Journal ArticleDOI
TL;DR: Grape-like Fe3O4-multiwalled carbon nanotubes (MWCNTs) are synthesized, which have unique multiscale-assembled morphology, relatively uniform size, good crystallinity, high magnetization, and favorable superparamagnetism, and provide an effective pathway to realize excellent absorbers at elevated temperature.
Abstract: Ideal electromagnetic attenuation material should not only shield the electromagnetic interference but also need strong absorption. Lightweight microwave absorber with thermal stability and high efficiency is a highly sought-after goal of researchers. Tuning microwave absorption to meet the harsh requirements of thermal environments has been a great challenge. Here, grape-like Fe3O4-multiwalled carbon nanotubes (MWCNTs) are synthesized, which have unique multiscale-assembled morphology, relatively uniform size, good crystallinity, high magnetization, and favorable superparamagnetism. The Fe3O4-MWCNTs is proven to be a smart microwave-absorber prototype with tunable high intensities in double belts in the temperature range of 323–473 K and X band. Maximum absorption in two absorbing belts can be simultaneously tuned from ∼−10 to ∼−15 dB and from ∼−16 to ∼−25 dB by varying temperature, respectively. The belt for reflection loss ≤−20 dB can almost cover the X band at 323 K. The tunable microwave absorption i...

307 citations

Journal ArticleDOI
TL;DR: An X-band microwave life-detection system has been developed for detecting the heartbeat and breathing of human subjects lying on the ground at a distance of about 30 m or located behind a cinder block wall.
Abstract: An X-band microwave life-detection system has been developed for detecting the heartbeat and breathing of human subjects lying on the ground at a distance of about 30 m or located behind a cinder block wall. The basic principle of the system is to illuminate the subject with a low-intensity microwave beam, and then from the back-scattered microwave signal, extract the heart and breathing signals that modulate it. The circuit description of the system and some experimental results are presented. Potential applications of the system are noted.

291 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202320
202244
2021198
2020244
2019245
2018263