1. CIRCE-Centro Tecnológico (Research Centre for Energy Resources and Consumption), Zaragoza, Spain
2. Department of Information and Communication Technologies, Universidad Politécnica de Cartagena, Cartagena, Antigones, Spain
3. Fricke und Mallah Microwave Technology GmbH, Peine, Germany
4. Department of Communications Engineering, Universidad de Málaga, Málaga, Spain