A full-wave approach is proposed to evaluate the shielding performance of metallic rectangular double-stage cascaded enclosures with apertures. The analysis has been carried out by means of the mode-matching technique and the mixed potential integral equation solved with the Method of Moments. The effects of the dimension of enclosures, the orientation of apertures, the polarization direction of the incident wave, the aperture thickness and the high-order modes propagating in enclosures are taken into account. The accuracy of the proposed approach is validated by comparing with other methods and numerical simulation results can derive some conclusions: the shielding performance of cascaded enclosures is better than that of single-stage enclosures, the shielding effectiveness can be improved with increasing the distance between stages in the range, and the shielding performance of the double-stage enclosure with parallel-pattern apertures in horizontal polarization case is better than that in vertical polarization case.
To meet the requirements for broadband operation, high port-to-port isolation, and miniature chip area, a doubly balanced monolithic microwave ring mixer with an advanced IF extraction fabricated using 0.15 μm GaAs pHEMT process is presented. A miniature Marchand-like spiral balun with low-pass filter is used to extract IF signals and maintain balun performance simultaneously. The low-pass filter can filter out both the RF and LO signals. This miniaturized mixer design can mitigate layout complexity, improve port-to-port isolations suitable for ultra-broadband Ku-, K-, and Ka-band applications. Subsequently, the LO/RF-to-IF isolations are greater than 43.2 and 32 dB from 11 to 40 GHz, respectively. The LO-to-RF isolation is between 26.9 and 50.7 dB within the same swept range. The conversion loss is 7.2-12.4 dB within the operating bandwidth.
A novel compact square slot antenna design with coplanar waveguide (CPW)-fed for dual-band operation is presented. The proposed antenna is simply composed of a square slot resonator and a monopole radiator. By employing the special square slot structure, the antenna can achieve a new resonance while maintaining a small size. Based on this concept, a prototype of dual-band antenna is designed, fabricated and tested. The experimental results show the antenna has the impedance bandwidths of 400 MHz (2.33-2.73 GHz) and 1020 MHz (3.27-4.29 GHz), covering both WiMAX in the 2.5/3.5 GHz bands and WLAN in the 2.4 GHz band.
In this paper, a reflectarray antenna composed of a combination of double-petal loops of variable size is presented. To evaluate the performance of the designed element, a parametric study is carried out using Ansoft HFSS. For the optimal parametrics, the proposed structure shows an almost linear behavior, while the phase range is in excess of 500°. Then, a prime-focus 77-element reflectarray with this type of element has been designed and implemented. The measured results show that the obtained 1-dBi gain bandwidth of the reflectarray with double-petal loop elements can reach as large as 25% and the highest gain is about 19.3 dBi. Compared with the existing single layer elements (cross and rectangle loop, double rings, etc), microstrip reflectarray with this double-petal loop element can obtain a larger bandwidth.
A novel TM21-mode circularly polarised (CP) annular-ring microstrip antenna (ARMSA) is presented. The annular ring is designed working at TM21 mode, and conical radiation pattern is obtained. At the inner of annular ring, a simple ring-shaped feeding line is arranged to implement impedance matching and CP operation. Therefore, the antenna has good impedance and CP performance, as well as a compact structure. The measured results indicate that the antenna has high low-elevation gains and omnidirectional azimuth coverage. The peak gain reaches 4.3 dBic at elevation angle of 47°, and in the range of 10°-70°, the gain is above 0 dBic. The impedance bandwidth for S11≤-10 dB is 2.3% at 1.601GHz. The proposed antenna can be used in mobile earth-station equipment for satellite positioning and communication systems in global or local.
This paper presents a novel wideband planar dipole antenna with parasitic patches. Of which, acting primarily as directors, the parasitic elements aim to improve the radiation patterns in terms of gain especially at the higher frequencies. For verification, the proposed novel structure was fabricated and measured. The proposed antenna is well-matched with achieved VSWR<2 and has a good radiation performance across the entire operating frequency range of 3-8 GHz.
This paper proposes two novel broadband microstrip antennas using coplanar feed-line. By feeding the patch with a suitable shape of the coplanar line in the slot of the patch, the broadband character is achieved. Compared with the antenna fed by a U-shaped feed-line, the antenna with L-shaped feed-line not only has wider bandwidth but also achieves the circular polarization character. The measured bandwidths of 25% and 34% are achieved, and both of the antennas have good radiation characteristics in the work band.
A compact helix structure implementation and associated design formula of lumped element second-order bandpass filter circuit for high power frequency-hopping filter are proposed in this paper. The filter schematic provides one, two or three finite transmission zeros (Tzs), and these Tzs locates in the upper stopband to improve the rejection above the center frequency, especially the suppression of second harmonic with two Tzs. The filter schematic is built on a common grounded helix coil of inductive coupled resonator tanks whose suspectance is tunable. Due to the parasitical capacitance of the helix coil, the filter has a feedback capacitor between input and output. Its working mechanism is revealed both mathematically and graphically. The measured results have a good agreement with the 3D full-wave electromagnetic simulation responses. The experimental filter has a insert loss < 1.5 dB , return loss > 15 dB, a 3-dB bandwidth of 5%~8.5% over entire operating range with the power handling capability greater than 49 dBm and the suppression of second harmonic better than 56 dB.
A high-gain and broadband printed Yagi-Uda antenna is proposed. The microstripline-to-balance microstripline technique is adopted in the feeding mode of the active dipole, which can help to realize the balanced-unbalanced transformation. The ground of the microstrip feeding line can function as a reflector, and both the longer reflector and the shorter director can also help the antenna achieve wideband. By altering the area of the substrate, the antenna gain can be effectively improved. A printed Yagi-Uda antenna operating at 3.5 GHz has been designed and manufactured. Both the simulated and measured results indicate that there is a high positive correlation between antenna gain and the substrate area extended from the front of the director, and antenna broadband characteristic would not be changed at the same time. Moreover, the impedance bandwidth of the proposed antenna can achieve 27.4%, and the maximum gain in the operating band can reach 10.6 dBi.
Violations of the process of methylation reveal itself at the early stages of malignant transformation of cells, and the content of 5-methylcytosine can serve as a diagnostic test for tumor formation and treatment of disease. The carried out studies revealed the correlation of antitumor activity of MM-therapy (the coherent millimeter electromagnetic waves of low intensity) with inhibition of methylation of tumor DNA in vivo. It is established that an half-hour exposure of MM-radiation results in the tumor growth inhibition by 33,5% and a sharp suppression of the level of DNA-methylation -2.5 times. The results obtained in this experiment indicate the prospects of working out the MM-therapy for clinical oncology in the treatment of malignant neoplasms.
The nonlinear absorption of a strong electromagnetic wave caused by electrons confined in cylindrical quantum wires is theoretically studied by using the quantum kinetic equation for electrons. An analytic expression of the nonlinear absorption coefficient of a strong electromagnetic wave caused by electrons confined in a cylindrical quantum wire with a parabolic potential for electron-optical phonon scattering is obtained. The dependence of the nonlinear absorption coefficient on the intensity E0 and the frequency Ω of the external strong electromagnetic wave, the temperature T of the system and the radius R of the wires is strong and nonlinear. Analytic expression is numerically calculated and discussed for a GaAs/GaAsAl quantum wire. The results are compared with those for normal bulk semiconductors and quantum wells to show the differences.
A novel G-shaped slot ultra-wideband (UWB) bandpass filter with a very narrow notched band is proposed. The basic ultra-wideband filter is short-circuited stub bandpass filter consisting of shunted λ/4 short-circuited stubs and λ/4 connecting lines. To avoid the interferences such as WLAN signals. The G-shaped slot embedded in the stub filter is used to obtain the notched band inside the UWB passband. Additional U-shaped defected ground structures are adopted to improve the out-band suppression. Measured results show that the proposed filter has an ultra-wide bandwidth from 3.1 GHz to 10.6 GHz, and the insertion loss is less than 1 dB. Specifically, the fabricated filter possesses a 10 dB notched fractional bandwidth (FBW) of 2.36% at the notched center frequency of 5.8 GHz. It also achieves a stop band with 20 dB attenuation.
This paper presents a cavity backed slot antenna design with high gain and relatively small size. The large ground plane of the original design is cut 75%. Mushroom cells, ground plane orientation, and bending edges in the ground plane have been employed to improve the antenna gain. A 19.25 dB maximum gain is obtained with an average gain of 18.2 dB in the entire operating band.
In this paper, a low cost measurement system with high accuracy for radiated emission evaluation has been proposed. By combining the test data of the current probe at different positions on the harness, the measurement accuracy is improved compared with conventional single probe method For the sake of high accuracy, a transfer function is built to map the relationship between anechoic chamber method and current probe method. Based on experiments for evaluation, the final estimation of radiated emission agrees well with the measured results in anechoic chamber. For the cases tested, the difference between the current probe method and the anechoic chamber method is less than 3 dB.
Analytical investigations of the problem of dielectriccoated thin-wire antenna structures have invariably focused on the physics of developing appropriate models for the dielectric insulation on the thin-wire conductors that serve as antenna for the structure. These include the frequency domain moment-method-based approaches in which the dielectric insulation is replaced by equivalent volume polarization currents; and the time-domain analysis based on the `equivalent radius' concept. An earlier paper gave a physical interpretation to the frequency-domain solutions to suggest that the volume polarization currents derive from an equivalent static charge distribution, which excites an essentially radially-directed quasi-static field, confined to the region associated with the dielectric insulation. It is the main objective of this paper to investigate the veracity of the claims made in open literature as they concern the physics of the model for the dielectric insulation in terms of the electric field excited in the dielectric region. And to that end, simulation experiments were carried out, using a commercial Transmission Line Matrix (TLM) Method code, with which the characteristic features of the radial and axial components of the electric field within the dielectric region were investigated. The simulation results obtained from the experiments suggest that the field in question is not only of the quasi-static variety, but that it is also characterized by an axial component that meets the boundary condition of vanishingly small values on the surface of the conducting wire, to support the theory proposed.
A novel printed dipole antenna was designed for the L-band satellite communication system INMARSAT (Downlink: 1525--1559 MHz, Uplink: 1626.5--1660.5 MHz). Several structural parameters were experimentally studied with care to establish a design procedure. The measured results show that the impedance bandwidth for return loss below -10 dB is about 170 MHz and that the half-power bandwidth (HPBW) can be up to 110°. The antenna can be used in high latitudes because of wider HPBW.
In this paper, a large signal equivalent circuit empirical model based on Anglov model for ceramic packed high power AlGaN/GaN HEMT has been proposed. A temperature-dependent drain current model, including self-heating effect, has been presented, and good agreement is achieved between measurement results and the calculated results at different temperature. The nonlinear capacitance models are modeled by the directly measured microwave scattering (S) parameters and multi-bias small signal equivalent model (SSECM) of packed device. A power amplifier based on large size AlGaN/GaN HEMT with a total gate periphery of 36 mm has been designed by using the proposed model for validation purpose, and the simulated results fit the measurement results well at different temperature.
A simple finite difference time domain (FDTD) scheme is proposed for modeling three-dimensional (3D) nondispersive chiral media. Based on the recently reported new BI-FDTD mesh method and rearranged curl equations, this scheme implements a simple leapfrog algorithm. By adding the mirror layer, the perfect electric conductor (PEC) condition is implemented in the BI-FDTD mesh method of 3D problem. Results of this scheme are presented for the scattering coefficients of discontinuity in waveguides, which are partially filled with chiral or achiral media. The validation is performed by comparing the results with those obtained from the literature and software simulation.
A highly miniaturized simplified composite right/left handed (SCRLH) mushroom zeroth-order resonator (MZOR) is proposed for bandpass filter (BPF) design. By introducing the U-slot etched around the metallic via (UEAV), more flexible selection of the shunt inductance value can be achieved compared with the original one. As the length of UEAV increased, zeroth-order resonant frequency of the MZOR decreased, even 88% size reduction can be achieved. Finally, a bandpass filter based on the proposed MZOR is designed, fabricated and measured. The simulated and measured results are presented and good agreement is obtained.
A novel bandwidth enhancement design of planar F-shaped dipole antenna for RFID tag is proposed. With the use of two parasitic strips inset along the closed loop of the input IC chip in this proposed tag antenna, a new resonant mode close to 900 MHz band is excited to enhance the operating bandwidth. The obtained impedance bandwidth across the operating band can reach about 104 MHz for UHF band. With omni-directional reading pattern, the measured reading distance is about 2.8 m as the tag antenna mounted on the glass object.
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