Decoupling and Matching Network for Miniaturised 3-Port Antenna Arrays Based on 180° Couplers

In ordinary antenna arrays the spacing between radiators is usually chosen lambda/2. In order to use antenna arrays in small mobile platforms, the overall dimensions and hence the radiator separation must be reduced, which aggravates the problem of mutual coupling between radiators. Results are highly distorted beam patterns and greatly reduced radiation efficiency. We propose a simple method to design a decoupling and matching network for a three element antenna array with a radiator separation of lambda/4, which excites the orthogonal eigenmodes of radiation of the antenna array.