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  • Final Activity Report Summary - ECEMSIM (Evaluation and customisation of electro-magnetic (EM) simulation tools for use in advanced antenna array applications)

Final Activity Report Summary - ECEMSIM (Evaluation and customisation of electro-magnetic (EM) simulation tools for use in advanced antenna array applications)

The project has resulted in a parallel mute, i.e. non-graphical, version of the QW simulator, an electromagnetic simulator, property of the QWED company. It has been tested under Windows XP, Linux, and Solaris, and no serious problem is expected porting it to other operative systems. Except versatility regarding the operative system, it is also possible to use on different hardware as 32 and 64 bit variants and different memory access schemes of the PC architecture as well as Sun Sparc processors.

As there are fundamentally different types of parallel computers, the code developed has two versions (selected using conditional compilation). One of them is based on parallel threads and can be used on multiprocessor and multi core machines with shared memory (all processors in the machine can access the memory in principally the same way as in a single processor computer). The other version uses 'Message passing interface' (MPI), a de-facto standard for communication in distributed memory computers, i.e. parallel computers which are divided into nodes, each one either a single processor or a multiprocessor shared memory machine.

In a distributed memory computer, the communication between nodes is handled with messages and sent over either standard ethernet or, preferably, special fast communication hardware. A common type of distributed memory machine is a cluster built with PCs as nodes. The advantage with the MPI standard is that it also can be used on shared memory machines. Accordingly, the MPI version of the simulator is executable both on distributed and shared memory computers. In the simulator a method called 'Finite difference time domain' (FDTD) is used. Principally, it is relatively easy to distribute this kind of simulation on several parallel processors. However, the QW simulator is an advanced tool which can model complicated structures, and with many options for sampling and special tasks. The data structure is complicated, and initially the efficiency of the parallel program was poor. However, a large work on restructuring of data was made, which resulted in a very efficient code. This means that the calculation time is proportional to the number of simulators. In some cases it is possible to get even faster execution due to better utilisation of cache memory.

In order to study the results produced by the parallel simulator, it samples the results such as S parameters (transmission and reflection coefficients of the microwaves) and antenna pattern (the distribution of the electromagnetic fields in different directions) during the simulation. The format of the exported data is such that it can be easily shown graphically with the normal graphical and interactive QW simulator. The input data for the simulator is created using QW editor, where the geometry of the simulated device is described together with material data, ports where microwave energy is fed in and captured out, properties of the boundaries, desired output data etc. For the parallel simulator, the simulated structure is divided into subcircuits. To permit the creation and export of them to the simulator, the editor was modified.

All these programs have been used in simulations of an antenna, which consists of a lens and a feeder horn. The lens has the diameter of 1.2 m and is made up of a metal disc with 1272 intersecting tubes. It is placed at a distance of 1.2 m from the feeder horn. Using the symmetry of the antenna only a quarter is necessary to simulate.

The working frequency of this antenna is between 10 and 15 GHz, corresponding to a wavelength between 3 (10 GHz) and 2 cm (15 GHz). This means that the structure is larger than 60 wavelengths at the higher frequency in all directions. The simulation time is in the order of 48 hours on a machine, where eight CPUs are used in parallel. It is very memory demanding, requiring about 32 GB of memory. But, notwithstanding, it has been shown that it is a feasible tool for evaluation of extremely big and complicated microwave systems.

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