Circularly Polarized Antennas

Chapter 4

Multi-Band Circularly Polarized Antennas

4.1 Introduction

Many wireless systems operate at several different frequency bands. For example, modern GNSS systems employ signals at several frequency bands including L1 (1.575 GHz), L2 (1.227 GHz), E5a and E5b bands (1.164–1.215 GHz), and so on. Satellite communication systems also employ different frequency bands for uplink and downlink applications: 6 and 4 GHz are the uplink and downlink frequencies used in C-band satellite communications; 14 and 12 GHz are the uplink and downlink frequencies used in Ku-band; and 30 and 20 GHz are the uplink and downlink frequencies used in Ka-band satellite communications. For these systems, it is possible to employ several single-band CP antennas with one antenna covering each frequency band separately. This, however, will lead to a large size, mass and high cost of antenna and wireless systems. It is far more desirable if a single multi-band CP antenna can be employed for these applications, as it can result in a significant reduction in size, mass, complexity and cost of wireless systems. Thus, multi-band CP antennas have become a hot research topic in recent decades, and a variety of techniques have been developed.

This chapter reviews different techniques for designing multi-band CP antennas, including multi-band CP microstrip patch antennas, multi-band CP slot antennas, multi-band CP DRAs, multi-band QHAs and PQHAs, and so on. Some other antennas such as dual-band dual-sense CP antennas ...