Improvement of System Compatibility through Coupling Reduction

Abstract

This paper deals with various techniques in the form of modifications or additions which were developed to produce additional coupling reduction in existing systems. Although this has been the prime purpose, due consideration has been given to the effects of the different methods on the original objectives of the systensa Some of the techniques alter the radiation patterns and gains of the antennas involved. Consideration has been given to developing techniques which are operable over a broad band of frequencies in order not to restrict the operational requirements of the systems involved.Both analytical and experimental results are presented. Experiments were performed in convenient microwave frequency bands. However, by proper scaling with respect to frequency, it is possible to use the results given in this paper at other frequencies.One of the methods of coupling reduction described here is the compensating bridge. This bridge is formed with the addition of a cancellation link between two interfering systems. The bridge is balanced by adjusting the amplitude and phase of the power transmitted through the link to obtain high isolation. The distinct achievement here is the reduction of interference between two systems over a broad range of frequencies. This method is one of the most versatile since it can be readily extended to almost any frequency band.The use of corrugations in the form of circumferential trenches around the aperture of an antenna was found to offer a substantial reduction in coupling. The application of these trenches not only decreases the interference between two systems, but also increases the gain of each of the antennas involved. This method has been found successful when applied to slots, monopoles, spirals and horns as shown in the paper.Parasitic linear elements in the form of fences erected on the ground plane between two slot antennas have produced an additional isolation of 35 db over a 25 percent bandwidth. Finally, results are presented showing the possibility of combining different decoupling methods such as the bridge and corrugations to achieve greater system isolation.Quite obviously, many of the results of this paper are immediately applicable to the problem of intra-system interference. It is also believed that the bridge method can be easily applied to inter-system interference,where the systems involved are under the control of the same personnel. IntroductionEarlier work by the authorsl involved the study and acquisition of data dealing with the level of electromagnetic coupling present between two systems. This paper has a different objective. Rather than present information to be incorporated in a mathematical model to evaluate the interference problem between systems, methods to reduce coupling are presented. In approaching the problem of modifying an electromagnetic field situation in order to reduce coupling it is necessary, first of all, to consider the primary objectives of the various systems involved. Emphasis must be placed on the possible effect of different ...