It is common nowadays to add a cover to your mobile phone, both for protection and esthetical reasons. They are available in many different stores including the mobile operator branded stores. The material and form varies considerably from one cover to another. You can get everything from plastic and rubber covers to silicon or metal. Of course the different materials have pros and cons. Some are more protective, even against the delivery of data. The question that follows is; how does a cover affect the performance of the antenna?