Chapter 9Miniature Antennas 1




9.1. Introduction

The surge in new technologies is enabling more and more features for compact mobile terminals to be presented. Numerous wireless communication standards are being developed, some concurrent, some complementary. For example, it is well known that standards in mobile telephony present a wide coverage and allow a high mobility, while standards in wireless local area networks, such as the IEEE 802.11 standards, enable much higher throughputs, but with poorer coverage and more reduced mobility. A terminal claiming to offer a large range of services with variable throughputs and dynamics should therefore integrate send/receive modules working with several intrinsically different characteristic standards. A common characteristic will, in the case of mobile terminals, always be bulk: with user acceptance assuming a practical and aesthetically pleasing object, then, this being the case, antennas must be as discreet as possible.

Furthermore, each communication standard has been allocated a band of defined working frequencies by the regulatory authorities. As we will see later, the width of the allocated spectrum will directly influence the bandwidth of the antenna and therefore its size. The standards also induce particular characteristics in the performance of the antenna, such as its matching level, the form of radiation created, field polarization, or even a multiplication of the number of antennas for the same standard, as is the ...

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