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A dual-mode ring coupler is proposed for balanced frequency doubler application based on the microstrip technology. The proposed coupler can operate in a quasi-hybrid ring coupler mode and a T-junction power divider/combiner mode at two frequency bands with center frequencies of $f_{0}$ and $2f_{0}$ , respectively. The operating principle is analyzed, and the design procedure is described. To verify the proposed concept, a 3-/6-GHz dual-mode ring coupler is developed and fabricated. Measured results demonstrate that the proposed coupler achieves good performances with bandwidths up to 20% at both lower and upper bands. The measurements agree well with the simulations. Finally, as an application demonstration of our proposed dual-mode coupler, a 19-/38-GHz balanced frequency doubler based on this structure is also designed and fabricated. Measured results show that the conversion loss of the fabricated multiplier is less than 8.9 dB with the input frequency ranging from 17 to 21 GHz, and the minimum conversion loss is 7.3 dB at 19 GHz. [ABSTRACT FROM AUTHOR]

In this paper, a high-performance PIN diode single-pole-double-throw (SPDT) switch for W-band application is developed. By employing quasi-monolithic millimeter-wave integrated circuit (Q-MMIC) technology, the cost of the switch is significantly reduced while maintaining performance and size with conventional MMIC counterpart. A 3-D PIN diode model is used to describe the diode characteristic under both forward and reverse biasing states. In order to alleviate parasitic parameters effect on performance of the switch, compensation structures are analyzed and adopted. The measurement results show the insertion loss is less than 2 dB from 82 to 100 GHz and the isolation is greater than 32 dB from 82 to 105 GHz. The total size of the SPDT switch is 2.1 mm × 4.3 mm. [ABSTRACT FROM PUBLISHER]

ABSTRACT This article presents an inline waveguide to suspended stripline (SSL) transition. The transition adopts unilateral finline to transform the input waveguide TE10 mode to SSL Quasi-TEM mode. The module of the transition is split into two halves along the center of the waveguide E-plane. The substrate is flip mounted on the grooves of the lower half of the module. The finline is extended to the mounting groove and bonded to the waveguide channel. The waveguide feed direction is inline with the SSL wave transmission direction, and DC/IF return path is also provided by the finline. A G-band prototype is designed and fabricated. The measured results show that the insertion loss is 1.3 to 2 dB at frequencies from 140 to 213 GHz, with return loss more than 10 dB. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:729-732, 2017 [ABSTRACT FROM AUTHOR]

A novel E‐plane probe microstrip‐to‐waveguide transition for millimetre‐wave application is proposed. By introducing a fin‐line back‐short structure, tight‐tolerance machining and assembling of the waveguide back‐short commonly encountered with traditional E‐plane probe microstrip‐to‐waveguide transition are no longer necessary. A Ka‐band transition prototype is designed and fabricated to validate the design concept. Simulated and measured results agree well and both of them show the proposed transition achieved good return and insertion losses over the full Ka band. [ABSTRACT FROM AUTHOR]

Aluminum foams with different porosity are fabricated by varying processing parameters using melt foaming method. The macro–micro structure characteristics and electromagnetic interference (EMI) shielding effectiveness of aluminum foams are investigated. The results indicate that the pore walls mainly consist of aluminum matrix, Al 4 Ca phases at the grain boundary and some defects including cracks, compound particulate collections on the pore inner walls. Aluminum foams possess good EMI shielding effectiveness of 25–75 dB to the space plane electromagnetic wave within the frequency of 130–1800 MHz. Its EMI shielding effectiveness generally increases with increasing porosity and decreases with increasing frequency. Furthermore, the electromagnetic shielding mechanism is systematically explored and the EMI shielding equation applied to aluminum foams is also proposed, which is correlated to reflection loss, absorption loss, multiple reflections loss, eddy-current loss, wave–current interaction and any other factors. The experimental results can be well explained qualitatively. [ABSTRACT FROM AUTHOR]

Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen, and to carry over melt to a tailor-made apparatus that ensures directional solidification. Hydrogen is driven out of the melt, and then the quasi-cylindrical pores normal to the solidification front are usually formed. In the research, the effects of processing parameters (saturation pressure, solidification pressure, temperature, and holding time) on the pore structure and porosity of porous aluminum alloys were analyzed. The mechanical properties of Al-Mg alloys were studied by the compressive tests, and the advantages of the porous structure were indicated. By using the GASAR method, pure aluminum, Al-3wt.%Mg, Al-6wt.%Mg and Al-35wt.%Mg alloys with oriented pores have been successfully produced under processing conditions of varying gas pressure, and the relationship between the final pore structure and the solidification pressure, as well as the influences of Mg quantity on the pore size, porosity and mechanical properties of Al- Mg alloy were investigated. The results show that a higher pressure of solidification tends to yield smaller pores in aluminum and its alloys. In the case of Al-Mg alloys, it was proved that with the increasing of Mg amount, the mechanical properties of the alloys sharply deteriorate. However, since Al-3%Mg and Al-6wt.%Mg alloys are ductile metals, their porous samples have greater compressive strength than that of the dense samples due to the existence of pores. It gives the opportunity to use them in industry at the same conditions as dense alloys with savings in weight and material consumption. [ABSTRACT FROM AUTHOR]

In this paper, a W-band single pole single throw (SPST) switch based on a novel PIN diode model is presented. The PIN diode is modeled using a full-wave electromagnetic (EM) simulator and its parasitic parameters under both forward and reverse bias states are described by a T-network. By this approach, the measurement-based model, which is usually a must for high performance switch design, is no longer necessary. A compensation structure is optimized to obtain a high isolation of the switch. Accordingly, a W-band SPST switch is designed using a full wave EM simulator. Measurement results agree very well with simulated ones. Our measurements show that the developed switch has less than 1.5 dB insertion loss under the 'on' state from 88 GHz to 98 GHz. Isolation greater than 30 dB over 2 GHz bandwidth and greater than 20 dB over 5 GHz bandwidth can be achieved at the center frequency of 94 GHz under the 'off' state. [ABSTRACT FROM AUTHOR]

Vitamin B1 (VB1) is a commonly used additive in the food and pharmaceutical industries. However, VB1 is typically in a powdered form during its production and processing. Experiments were conducted to determine the explosion characteristics of VB1 dust. The results showed that the minimum ignition energy (MIE) was 200 mJ and the minimum ignition temperature (MIT) was 410°C. Meanwhile, P max and K st were 5.7 bar and 143 bar m/s, respectively. To mitigate the explosion hazards of VB1 dust, powdered melamine polyphosphate (MPP) was chosen as an inhibitor. When the addition of MPP reaches 30 wt%, no VB1 dust explosion occurs. The inhibitory performance and mechanism of MPP on VB1 dust explosion were systematically investigated by combining the thermal characteristic curves of MPP and VB1 dust. The polyphosphate produced by the decomposition of MPP reacted chemically with VB1 dust, which indicated the formation of a compact carbon layer. [Display omitted] • This study reveals the explosion risk of VB1 dust. • Melamine polyphosphate (MPP) can effectively suppress VB1 dust explosion. • The inhibition performance and mechanism of MPP on VB1 dust were revealed by TG-DSC and TG-FTIR. [ABSTRACT FROM AUTHOR]

A high Q‐factor substrate integrated waveguide (SIW) cavity resonator and its application of X‐band low phase noise oscillator is proposed. Complementary split‐ring resonators are used to improve the Q‐factor of the proposed resonator. The size of the resonator is reduced by using quarter‐mode circular SIW cavity. The oscillator based on the proposed SIW cavity resonator can be easily designed and tested. Measured results demonstrate an output frequency of 10.11 GHz and a phase noise of −108.7 dBc/Hz at 100 kHz offset. The oscillator is also able to deliver an output power of 4.6 dBm and harmonic rejection of better than 30 dBc. The proposed oscillator is suitable for low‐cost high‐frequency systems. [ABSTRACT FROM AUTHOR]

Sulphuric Acid Anodic Oxide (AAO) film is a common method for corrosion protection of 5083 Al alloys, and cracks may occur in the AAO film due to stress damage. In this study, cracks in the AAO film on 5083 Al alloy were pre-prepared by mechanical tension, and the cracks on the corrosion protection property of AAO film were in-situ investigated by scanning electrochemical microscopy (SECM). The morphology and composition of the AAO film were measured by SEM, XRD and XPS. The results show that the corrosion protection performance of AAO film for 5083 Al alloy decreases with the increase of cracks, which is due to the fact that cracks can act as diffusion channels for corrosive media, resulting in serious corrosion reaction. SECM shows the local current at the cracks of the AAO film first increases and then decreases due to the cracks being gradually repaired by the deposited corrosion products (Al(OH) 3 , Al(OH) 2 Cl, and AlOOH). A repair mechanism of cracks in AAO film on 5083 Al alloys is revealed during the corrosion process. • The corrosion process of the damaged AAO film is observed in situ by SECM. • The cracks of damaged AAO film on Al alloy can be repaired by the corrosion products. • A corrosion model is proposed to reflect the repair mechanism of cracks in AAO on 5083 Al alloys. [ABSTRACT FROM AUTHOR]

A broadband transition from microstrip line to spoof surface plasmon (SP) waveguide is proposed. The transition transforms the guided wave into a spoof SP polariton in a broad microwave frequency band. A back‐to‐back transition sample is fabricated using the proposed method. Good agreement between the measurement and simulation is obtained. The measured results show an insertion loss <2 dB and a return loss below −11 dB from 2.2 to 10 GHz. The proposed broadband transition may pave a way for advanced conventional plasmonic integrated microwave devices and circuits. [ABSTRACT FROM AUTHOR]