Analysis software has broadband appeal

Deltenna has used Micro-Stripes electromagnetic analysis software to design a 16-beam, leaky mode dielectric resonator antenna in one-fifth the time of using the conventional build and test method.

Deltenna has used Micro-Stripes electromagnetic analysis software from Flomerics to design a 16-beam, leaky mode dielectric resonator antenna in one-fifth the time that would have been required using the conventional build and test method.

The antenna plays a crucial role in Radiant Network's Meshworks technology, a new generation of broadband access technology that allows customers to connect via adjacent customers, rather than a basestation.

"The challenge in designing this type of antenna is to pick a shape and dielectric constant for the elements that will provide sufficient gain and operate in the right bandwidth", said Dr Andrew Fox, Managing Director of Deltenna.

Deltenna engineers began by simulating a single ceramic element in Micro-Stripes, changing the dielectric constant and geometry of the model until they achieved their design objectives.

They tested a sample element to verify its performance then used a similar iterative process to design the array.

"The rapid progress that we made on this project was largely due to the predictable simulation/build/test cycle made possible by the use of a simulation tool that allowed us quickly to predict the performance of each design iteration", Fox said.

Meshworks uses roof-mounted nodes with steerable, directional antennas.

Each node transmits to and receives from other nodes, routing around obstacles and eliminating the problems of line of sight, unlike traditional point-to-multipoint solutions.

The key to the performance of Meshworks was the development of a custom antenna that could deliver the level of gain required while meeting tight space and cost requirements.

Meshworks selected Deltenna because of its expertise in developing leaky mode dielectric resonator antennas that can be manufactured at a lower cost than more conventional patch antennas.

"We had our work cut out for us in developing an antenna that could meet Radiant Network's tight performance specifications within a timeframe of only six months", Fox said.

Micro-Stripes is Deltenna's design tool of choice because it uses the transmission line matrix (TLM) method that solves for all frequencies of interest in a single calculation and therefore captures the full broadband response of the system in one simulation cycle.

"We started with a single element and gave it an arbitrary profile, thickness and dielectric constant", Fox said.

"The simulation showed that the bandwidth was too narrow".

"So we changed the model to reduce the dielectric constant and reran the simulation".

"The bandwidth was still too narrow so we reduced the thickness of the element, furthering increasing the bandwidth range".

"We continued in an incremental process until we had achieved our design objectives".

"Finally, we simulated a four-by-two array of elements to evaluate the performance of the complete array with beam steering".

The largest problem identified in the initial system simulation was that the side lobes were too high.

Deltenna engineers weighted the aperture to reduce the side loads, increasing the drive to the middle columns and reducing the drive to the outside columns.

They continued with additional adjustments until they had met all of the customer's requirements.

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