European Space Agency

Development of Diagnostic Tool - DIATOOL

Objectives

DIATOOL will be a stand-alone commercial program performing advanced electromagnetic processing of measured antenna data.

DIATOOL will read the measured field and compute the extreme near-field or the currents on the antenna surface, without the fundamental constraints of the traditional measurement systems. From the inspection of the extreme near-field and currents, DIATOOL will solve typical antenna diagnostics problems, such as identification of array element failure and antenna surface errors, but also allow to artificially remove undesired contributions, such as currents on cable and fixture, saving valuable time and resources in the antenna design and validation process.

The objective of this project is to provide a powerful data processing tool for the advanced antenna engineer. DIATOOL will allow post-processing of the measured field and reconstruct ion of the extreme near-field or the currents on the antenna surface, without the fundamental constraints of the traditional measurement systems.

The inspection of the extreme near-field and currents will identify the electrical or mechanical errors in the antenna which cause undesired anomalies in the far-field, saving valuable time and resources in the antenna design and validation process. The comparison between expected surface currents and surface currents reconstructed from measurements is not possible today. Therefore, DIATOOL will be the missing link in the antenna design loop:


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DIATOOL will be based on two field reconstruction techniques, i.e. the SWE-PWE, and a new and accurate source reconstruction technique based on an inverse Method of Moments algorithm. A high-quality GUI will guide the user through all the steps, i.e. from defining the Antenna Under Test to plotting the reconstructed fields and currents.

Challenges

DIATOOL will include two different electromagnetic models for antenna diagnostics:

  1. A SWE-PWE method, which computes a plane wave expansion of the measured field data based on full-sphere measurements. The near field can be reconstructed on a plane in the immediate vicinity of the antenna under test. The method is fast and efficient.
  2. An inverse Method of Moments (INV-MOM) which takes full-sphere or truncated measurement data as input and transforms the data by means of an integral equation back to an arbitrary three-dimensional closed surface containing the AUT. The method is very accurate but the memory requirement grows with the electrical size of the antenna.

Benefits

The DIATOOL software will provide the customer with a tool for reliable diagnosis of errors in antenna systems. This need is particularly dominant in the spacecraft manufacturing industry due to the stringent requirements found in hardware for space applications. DIATOOL will also be useful in other industries, where requirements on predicting the source of measured deviations in anechoic chambers are important. While antenna diagnostics has been studied over the last decade, there are to our knowledge no software tools available that perform the same advanced data processing as developed in this project.

The software delivered by the largest measurement facility providers includes the possibility of a simple diagnostics based on backpropagation. These software packages differ from DIATOOL in two important aspects. First, there are not available as self-contained software packages but are embedded in a specific measurement system; second, they lack the possibility of highly accurate diagnostics. In particular, they do not allow the reconstruction of the 3D currents on the antenna surface and the possibility of recovering a part of the antenna invisible spectrum.

Features

DIATOOL will read the measured field and compute the extreme near-field or the currents on the antenna surface.

A high-level description of DIATOOL in four functional parts is given below:

  1. Definition of the reconstruction surface
  2. Input of the measured field
  3. Field reconstruction
  4. Output of the reconstructed field

       


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The blue boxes in the figure involve interfaces with external programs and the measurement system.

 

A high-quality GUI will guide the user in all the steps, i.e. from defining the Antenna Under Test (AUT) to plotting the reconstructed fields and currents.

Regarding point 1, the GUI will allow the definition of planes, boxes, cylinders and spheres. The GUI will also allow importing a CAD file for the AUT geometry.

Regarding point 2, DIATOOL will support import of fields, either as a radiation pattern or as a spherical wave expansion. The recently developed EDX/EDI and traditional TICRA formats will be possible.

Regarding point 3, the algorithms implemented in DIATOOL and used to compute the extreme near-field field or the currents on the antenna surface are based on the results of two Ph.D. studies conducted in recent years by two TICRA employees. While the SWE-PWE algorithm was especially developed for antenna diagnostics purposes, more work has to be done for the INV-MOM algorithm, since the inversion of the Method of Moment code has to be developed from scratch. Special attention will be paid on the correct choice of boundary conditions, discretization and regularization.

In point 4, 2D plots for the field computed by SWE-PWE and 3D plots for the ones computed by INV-MOM will be possible. Moreover, field cuts along a user specified line will be implemented.

Plan

TICRA will adopt a customer-oriented development approach. We intend to identify and interview potential customers and providers of measurement ranges to ensure that DIATOOL will fit into the end-user's operating environment and solve the typical customer problems. When the user requirements are established, the software will be designed in multiple stages: The first design phase is aimed at arriving at a high-level design and a very minimal prototype of the software will be programmed. The second design phase will lead to the detailed software design which will finally be implemented in the final phase of the project.

Current status

The contractor has just completed the first two phases of the project, i.e. Phase 1 “User requirements” and Phase 2 “Modelling”.

In Phase 1, three potential customers and one provider of measurement ranges have been identified and interviewed, in order to obtain concise view of the requirements for the DIATOOL software.

Phase 2 has been focused on the models requirements, development and validation. First, a complete set of requirements has been established, for the INV-MOM and SWE-PWE algorithms, separately. Canonical test cases have been analyzed by both models, including cases involving synthetic data and noise. The modelling and the validation have been successful for both algorithms.

The next phase is Phase 3 “Software requirements and design”, where the high level design of the DIATOOL analysis engine and DIATOOL GUI will be established.

Status date

Wednesday, June 23, 2010 - 17:40