Mohamed H. Awida

Substrate-Integrated Waveguide Ku-Band Cavity-Backed 2

A Ku-band cavity-backed microstrip patch 2 x 2 antenna array has been implemented using the substrate-integrated waveguide (SIW) technology-a low-cost multilayer printed circuit board (PCB) process. Cavities are emulated using vias, and the patches are fed using microstrip lines that are centrally fed by a shielded coaxial probe feed line. Simple design guidelines for the cavity, patch, and substrate selection are presented. The array was fabricated, and its measured results agreed very well with theoretical predictions and indicated a relatively high efficiency and wide bandwidth of greater than 70% and 9%, respectively.

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The substrate-integrated waveguide (SIW) technology is utilized as an alternative low-cost approach in fabricating cavity-backed patch antennas. The proposed antenna arrays combine the attractive features of the conventional metalized cavity-backed patch arrays like surface wave suppression, high radiation efficiency, and enhanced bandwidth, yet provide a low manufacturing cost. A previously developed design of a 2×2 SIW cavity-backed microstrip patch sub-array is extended here and used as a basic building block to attain larger arrays of 2 × 4, 4 × 4, and 8 × 8 elements. The fabricated arrays have been measured and demonstrate good agreement with their simulated performance. The design and performance of these arrays are compared to other conventional bandwidth enhancement techniques, which prove SIW as a viable alternative.

2 Microstrip Patch Array Antenna

A class of wide-scan angle wide-band microstrip patch phased arrays is proposed. The proposed phased arrays are composed of probe-fed microstrip patches backed by substrate-integrated cavities. First, a simplified 2-D numerical analysis based on Floquets theorem is presented to qualitatively demonstrate the E-plane scan performance of the cavity-backed structure compared to that of the conventional microstrip patch phased array. Second, the 3-D scan performance of the proposed phased arrays is thoroughly investigated varying both the substrate thickness and dielectric constant using commercially available EM simulation tools, which is followed by presenting simple design guidelines for the cavity, patch and substrate. A 7 × 7 prototype phased array of the proposed SIW cavity-backed patch structure was fabricated and its measured results agree well with our theoretical prediction and indicate a relatively wide-scan performance when compared to the corresponding microstrip patch phased array without cavities.

Substrate-Integrated Cavity-Backed Patch Arrays: A Low-Cost Approach for Bandwidth Enhancement

A novel family of substrate-integrated waveguide (SIW) cavity-backed antennas is proposed. The proposed SIW cavity-backed topology has the potential to be used for a bandwidth enhancement where it could widen the inherent limited bandwidth of the conventional patch (typically 2%) to about 10%. Unlike the conventional metalized cavity-backed antenna which requires two fabrication processes; a PCB process to print the patches on the substrate and a CNC machining to attain the cavity backing the patch, the proposed SIW topology has a low fabrication cost, as the whole structure could be attained using a conventional PCB process. Here the radiation could be related to both the patch and the slot elements.

Analysis and Design of Wide-Scan Angle Wide-Band Phased Arrays of Substrate-Integrated Cavity-Backed Patches

We have simulated and experimentally tested a coaxial probe measuring system to be used in distinguishing between normal (healthy) breast tissue and cancerous (often malignant) breast tissue. The system employs commercially available components including an Agilent 8363B phase network analyzer (PNA) and an Agilent 85070D dielectric probe. Instead of the Agilent software three material calibration technique, we propose a four material calibration method across the frequency range of 3–17 GHz for more robust measurements of the complex permittivity. Experimental results on human and snake tissues show the non-homogeneous nature of biological tissues and also illuminate the dependence of complex permittivity on tissue temperature. Building upon the differences and also the variation seen in complex permittivity in literature between normal and cancerous breast tissue across this frequency range, we propose a technique which utilizes a neural network where multiple measurements are input in making the final decision on whether or not the tissue under test is cancerous. Simulation results using Ansoft HFSS are provided here and show the potential of microwave diagnosis of breast cancer.

Low-cost high-efficiency substrate-integrated cavity-backed single element antenna

A Ku-band cavity backed microstrip patch antenna sub-array suitable for dual linear/circular polarization is being developed based on substrate integrated waveguide (SIW) technology for DBS applications. SIW cavities have been emulated using vias and the patches are fed using microstrip line feed network. A 3×4 sub-array has been fabricated, tested and its results demonstrated a relatively high efficiency performance along the DBS 12.2–12.7 GHz band. The design for dual polarization could be used for either dual linear or dual circular polarization and provides adequate isolation between them. Larger array designs can be easily modified to use waveguide feeds along with probes to sustain its high efficiency performance.

Open-ended coaxial probe measurements for breast cancer detection

Microwaves can be used efficiently for casting metals using specially designed industrial microwave ovens. Their designs, however, is a challenging multi-physics problem that would require addressing concurrently electromagnetic, thermal, material and chemical issues. In this paper, a simplified model has been developed to model the operation of an industrial microwave oven. Our EM and thermal results were obtained using FEM modeling and have been experimentally validated via a modular chamber using the thermal and electrical measured material properties at elevated temperatures. Such modeling success is very valuable that would help in further optimizing the microwave metal melting technology.

Development of a substrate-integrated Ku-band cavity-backed microstrip patch sub-array of dual linear/circular polarization for DBS applications

A 2×4 Ku-band cavity-backed microstrip patch antenna array has been implemented using the substrate integrated waveguide technology (SIW) –a low cost multi-layer PCB process. Cavities are emulated using vias and the patches are probe fed using a microstrip feed network. The microstrip feed network is placed in the back of the antennas to reduce the mutual coupling between the feed network and the patches. Therefore, a superior antenna performance was obtained in terms of the realized gain and the radiation pattern. The array was fabricated and its measured results agreed well with our theoretical predictions and indicated high efficiency and wide bandwidth of greater than %74 and 6% respectively.

Modeling of an industrial microwave furnace for metal casting applications

We developed a cavity backed patch 16×4 array suitable for dual polarization. The array is designed based on a cluster of eight of 2×4 sub-array that are fed using coaxial probes. Two probes are used to feed the sub-arrays, one for each polarization, meanwhile long SIW guides are used for feeding these subarrays. The large array requires three layers. The top layer has the radiating microstrip patches, i.e. 8 clusters of 2×4 sub-arrays, and the middle layer has the backing SIW cavities (located under the patches), and the bottom layer has the extra layer for the feed waveguides. For both arrays, each patch element in the subarray is dual-fed by horizontal and vertical microstrip lines at orthogonal edges of the patches. In addition, a set of four patches were added to allow staggering of the microstrip dividers to reduce coupling and simplify feed.

A 2×4 substrate-integrated waveguide probe-fed cavity-backed patch array

The microwave furnace casting process is a time and temperature dependent nonlinear process. In this paper, we present our multi-physics modeling of a microwave oven process that is based on a coupled 3D EM- thermal analysis. Our efforts include the development of the necessary procedures and tools/probes to electrically and thermally characterize all utilized materials over a wide temperature range. Specifically, our novel core thermal analysis is based on the incorporation of black body radiation and the use of temperature dependent emissivity of all utilized materials. This developed 3D-EM/thermal non-linear model, for the first time, accurately predicts the temperature profile up to the melting point of the metal—which could lead to optimizing the oven design for efficient heating operation.