Frequency: Quarterly E- ISSN: 2277-6265 P- ISSN: Awaited Abstracted/ Indexed in: CNKI Scholar (China National Knowledge Infrastructure), Ulrich's International Periodical Directory, Google Scholar, SCIRUS, getCITED, Genamics JournalSeek
"Inventi Impact: Microwave" focuses on the research and development aspects of radio frequency technology. Published quarterly in print and online, it aims to cater to the professionals and policy makers in the field, as well as the general public.
A novel circular polarized rectenna with out-of-band suppression is proposed in this paper. The circular polarization is realized by\ncorner perturbation on a rectangular radiation patch and enhanced by a diagonal slim slot etched at the center of the patch. An\nopen stub connecting to the quarter wavelength impedance transformer is used to suppress out-of-band wave through harmonics\nnotching. The results of simulations and experiments agree very well, which show that the rectenna obtained âË?â??19 dB return loss at\n2.4GHz and âË?â??15.5 dB, âË?â??18.1 dB, and âË?â??11.4 dB suppression on second, third, and fourth harmonic frequency bands, respectively.The\nreflection coefficient in overall out-of-band, up to 10GHz, is limited up to âË?â??3 dB. Integrated with a voltage doubling rectification\ncircuit, the proposed rectenna can obtain 75.5% RF-to-DC conversion efficiency....
This paper presents a dual-band band-pass filter using modified cross-coupled step-impedance and capacitively loaded hairpin resonators for WLAN systems. The proposed filter has been designed to operate at a fundamental frequency of 2.4?GHz and the first harmonics frequency of 5.2?GHz. The techniques of step impedance and load capacitor are combined in the design of the proposed filter. In particular, the techniques of modified cross-coupling and overlap resonators are applied to improve the response of insertion losses S 21 at the first harmonic frequency of 5.2?GHz. The simulated and experimental results of insertion losses and return losses are better than 3?dB and 20?dB, respectively, at the operating frequencies....
A dual-band SiGe HBT frequency-tunable and phase-shifting differential amplifier has been developed for the future active phased\r\narray antennas with a multiband, multibeam, and multitarget tracking operation. The amplifier uses varactor-loaded, stacked\r\nLC resonators in the design of the output circuit in order to provide frequency-tunable and phase-shifting capabilities for dual\r\nfrequencies. By utilizing the varactor-loaded LC resonator, which has a variable resonant frequency and a large insertion phase\r\nvariation, frequency-tunable and phase-shifting performances become available. Moreover, by using the stacked configuration,\r\nthe frequency and insertion phase can be varied independently for dual frequencies. A dual-band SiGe HBT differential amplifier\r\nhas achieved a lower-frequency tuning range of 0.56 to 0.7 GHz for a higher fixed frequency of 0.97 GHz as well as a higherfrequency\r\ntuning range of 0.92 to 1.01 GHz for a lower fixed frequency of 0.63 GHz. A lower-frequency phase variation of 99? and\r\na higher-frequency phase variation of 90.3? have been accomplished at 0.63 and 0.97 GHz, respectively. This is the first report on\r\nthe dual-band differential amplifier with frequency-tunable and phase-shifting capabilities....
Performance evaluation is an important aspect in the study of microwave-absorbing\nmaterial coatings. The reflectivity of the incident wave is usually taken as the performance indicator.\nThere have been various methods to directly or indirectly measure the reflectivity, but existing\nmethods are mostly cumbersome and require a strict testing environment. What is more, they cannot\nbe applied to field measurement. In this paper, we propose a scheme to achieve field performance\nevaluation of microwave-absorbing materials, which adopts a small H-plane sectoral horn antenna\nas the testing probe and a small microwave reflectometer as the indicator. When the size of the\nH-plane sectoral horn antenna is specially designed, the field distribution at the antenna aperture can\nbe approximated as a plane wave similar to the far field of the microwave emitted by a radar unit.\nTherefore, the reflectivity can be obtained by a near-field measurement. We conducted experiments\non a kind of ferrite-based microwave-absorbing material at X band (8.2ââ?¬â??12.4 GHz) to validate the\nscheme. The experimental results show that the reflectivity is in agreement with the reference data\nmeasured by the conventional method as a whole....
A simple metasurface integrated with horn antenna exhibiting wide bandwidth, covering\nfull Ku-band using 3D printing is presented. It consists of a 3D-printed horn and a 3D-printed\nphase transformation surface placed at the horn aperture. Considering the non-uniform wavefront\nof 3D printed horn, the proposed 3D-printed phase transformation surface is configured by unit\ncells, consisting of a cube in the centre which is supported by perpendicular cylindrical rods from its\nsides. Placement of proposed surface helps to improve the field over the horn aperture, resulting in\nlower phase variations. Both simulated and measured results show good radiation characteristics\nwith lower side lobe levels in both E- and H-planes.,......
The absorbent resin for Cu2+ removal was prepared under microwave irradiation through grafting acrylamide (AM) and acrylic\nacid (AA) to cellulose. The initiator is a kind of redox system composed of potassium persulfate/sodium thiosulfate. The\ncrosslinking agent is...................
Amultifrequency radar system for detecting humans and classifying their activities at short and long ranges is described.The shortrange\nradar system operates within the S-Band frequency range for through-wall applications at distances of up to 3m. It utilizes\ntwo separate waveforms which are selected via switching: a wide-band noise waveform or a continuous single tone. The long-range\nradar system operating in the W-Band millimeter-wave frequency range performs at distances of up to about 100m in free space\nand up to about 30m through light foliage. It employs a composite multimodal signal consisting of two waveforms, a wide-band\nnoise waveformand an embedded single tone, which are summed and transmitted simultaneously.Matched filtering of the received\nand transmitted noise signals is performed to detect targets with high-range resolution, whereas the received single tone signal is\nused for the Doppler analysis. Doppler measurements are used to distinguish between different human movements and gestures\nusing the characteristic micro-Doppler signals. Our measurements establish the ability of this system to detect and range humans\nand distinguish between different human movements at different ranges....
This article presents a new approach to determining liquid concentration using a new\nmicrowave sensor and polarity correlator...........................
A new method of designing circularly symmetric shaped dual reflector antennas using distorted conics is presented. The surface of\nthe shaped subreflector is expressed using a new set of equations employing differential geometry.The proposed equations require\nonly a small number of parameters to accurately describe practical shaped subreflector surfaces. A geometrical optics (GO) based\nmethod is used to synthesize the shaped main reflector surface corresponding to the shaped subreflector. Using the proposed\nmethod, a shaped Cassegrain dual reflector system is designed.The field scattered fromthe subreflector is calculated using uniform\ngeometrical theory of diffraction (UTD). Finally, a numerical example is provided showing how a shaped subreflector produces\nmore uniform illumination over the main reflector aperture compared to an unshaped subreflector....
A novel technological method to improve the quality factor (Q) of RF-integrated inductors for wireless applications is presented in this paper. A serious reduction of substrate losses caused by capacitive coupling is provided. This is realised by removing the oxide layers below the coils with optimized underetching techniques. This special etching procedure is used to establish an environment in the inductor substructure with very low permittivity. A set of solid oxide-metal-columns placed below the metal windings stabilize the coil and prevent the hollowed out structure from mechanical collapse. The oxide capacitance is lowered significantly by the reduction of the permittivity er from values around 4 to nearly 1. Capacitive coupling losses into substrate are decreasing in the same ratio. The resulting maximum Q-factors of the new designs are up to 100% higher compared to the same devices including the oxide layers but shifted significantly to higher frequencies. Improvements of Q from 10 up to 15 have been obtained at a frequency of 3?GHz for a 2.2?nH inductor with an outer diameter of 213?�µm. The resonance frequency (f res) and frequency at maximum Q( f(Qmax)) are shifted to higher frequencies, caused by the shrunk total capacitance of the structure. This enables the circuit designer to use the inductors for applications working at higher frequencies. Coils with different layouts and values for inductance (L) were verified and showed similar results....
Loading....