Adel Saad Emhemmed

200GHz broadband proximity coupled patch antenna

In this paper, we have successfully designed a broadband elevated patch antenna using a new feeding technique. The antenna scheme offers a large operational bandwidth, compatibly with MMICs, eliminates the undesired substrate effects, and maximizes antenna performance on high dielectric substrates. A rectangular patch, elevated above the high dielectric substrate (semi-insulating-GaAs), is used as the main radiator. The patch is excited by electromagnetic coupling using a loop slot, which is formed in the antenna ground plane and located below the patch at the end of the 50 Ω CPW feed line. With this configuration a broadband patch antenna can be realized, and a low dielectric substrate constant can be created, since the antenna substrate is essentially air which is the lowest possible dielectric constant. The antenna was designed to operate at 200GHz for G-band applications. The simulation and measurement data have shown superior performance over conventional designs with a 10dB bandwidth of about 13GHz, from 190.8GHz to 203.8GHz, with nearly constant broadside radiation pattern over antenna bandwidth.

Integrated micromachined millimeter wave patch antenna

We have proposed 3-D micromachined elevated patch antenna for G-band (140GHz to 220GHz) applications. The antenna is consisted of coplanar waveguide (CPW) feed line, a feeding post, air-bridge, supporting posts, and elevated patch. The antenna topology effectively creates a low dielectric substrate and undesired substrate effects can be eliminated, since the antenna substrate is essentially air which the lowest possible dielectric constant. This will increase the radiation efficiency, gain, and the radiation bandwidth. The measurement result shows the bandwidth is about 7GHz, from 170GHz to 177GHz with nearly constant broadside radiation pattern. Also, this work has demonstrated the capability of fabricating a high performance antenna design in a MMICs compatible process.

Cantilever Beam Metal-Contact MEMS Switch

We present a new design of a miniature RF microelectromechanical system (MEMS) metal-contact switch and investigate various aspects associated with lowering the pull-down voltage and overcoming the stiction problem. Lowering the pull-down voltage in this design is based on reducing the spring constant by changing the cantilever beam geometry of the RF MEMS switch, and the stiction problem is overcome by a simple integrated method using two tiny posts located on the substrate at the free end of the cantilever beam.

EC-CPW fed elevated patch antenna

This paper presents a novel G-band (140GHz - 220GHz) integrated antenna. The antenna incorporates a newly proposed elevated center coplanar waveguide (EC-CPW) fed elevated patch antenna on a high dielectric substrate (GaAs). The proposed antenna consists of an (EC-CPW) feed line, λ/4 transformer used for matching, supporting posts, and a 5.5μm height elevated radiating patch. The antenna topology effectively creates a low-substrate dielectric constant and hence eliminates undesired substrate effects, since the antenna substrate is essentially air, the lowest possible dielectric constant. This increases the radiation efficiency, gain, and the radiation bandwidth. Close agreement between simulated and measured data have shown a good match of -20dB at 172GHz and bandwidth of 7.9GHz from 169.2GHz to 177.1GHz (return loss<;10 dB). Furthermore, the presented antenna exhibits an excellent constant broadside radiation pattern which makes it ideal for array antennas applications where directionality is an important factor avoiding pixels interferences. In addition the proposed antenna fabrication process is compatible with III-V MMICs process technology. This makes it ideal for fully integrated millimeter wave focal plane arrays applications.

Frequency reconfigurable proximity coupled patch antenna

This paper present a new design of frequency reconfigurable elevated patch antenna without using RF MEMS switch. It is well known that the patch height of the elevated patch antenna is one of the major factors in determining the antenna resonant frequency. By decreasing the patch height, the fringing fields from the patch edges will decrease, which decreases the extension in the patch length and hence the effective length of the patch, thereby increasing the resonance frequency. Therefore, the basic idea of this design is based on electrostatically adjusting the patch height to control the resonate frequency of the antenna. The measured return loss of the fabricated antenna in the up-position 0 volt, the resonant frequency of the antenna is about 189.2GHz with 18.7dB return loss. As the height of the patch reduced by applying the dc voltage, the resonant frequency shifts to 191GHz at 42volt dc voltage and with nearly the same bandwidth.

New Method to Fabrication 3D Micro-Device Structures

This paper present a new approach for fabricating 3D micro structures based on the elevated structures. The new fabrication method involves combinations of several basic techniques, but a key enabling techniques for the successful development of the fabrication process is combining the photolithography with e-beam lithography processes to create 3-D structures

Dual-radios hypermesh network based on CSMA protocol

Recently, multi-radio mesh technology in wireless networks has been put under extensive research. This is because of its potential to overcome the inherent wireless multi-hop throughput, scalability and latency problems caused by the half-duplex nature of the IEEE 802.11. This paper introduces a design and modelling of different elements on a distinct type of multicomputer networks, the dual-radio wireless hypermesh (DIWH), based on SystemC methodology. The hepermesh is a well-known topology that belongs to the hypergraph family of networks. Hypermeshes have been proposed as potential alternatives to the graph networks for the future System Area Networks (SAN). In this work, we consider a two dimensional DIWH network, where each router node is equipped with two radio interfaces and two non-overlapping channels are available for each node. we address the problem of assigning channels to communication links in the network with the objective of keeping overall network latency low and provide a relatively high throughput. The simulations and analysis have shown that our design achieves a significant increase in network throughput with less average network latency for large number of communication nodes, compared with the CSMA shared channel model, which is currently the de facto MAC protocol for most wireless networks. Our simulations have been validated analytically to show the accuracy of the developed model. In addition, simulation results have shown that the wireless hypermesh outperforms shared medium wireless networks under the constant total bandwidth argument, especially in large networks.

Surface waves reduction in microstrip antennas

This paper presents a survey of reducing surface waves in printed and microstrip antennas on substrates which may be electrically thick, as would be the case for printed antennas at millimeter wave frequencies. The surface wave loss is one of the well-known problems that researchers around the world are trying to overcome. This paper defines the problem and describes the main techniques proposed to reduce surface waves in MSAs.