title: MIMO antennas for mobile phone applications
Creators: name: Al Ja'Afreh, Saqer
Publisher: name: University of Liverpool Repository
Year: 2015

description: Recent evolutions in wireless mobile communications have shown that by employing multiple inputs and multiple outputs (MIMO) technology at both the transmitter and receiver, both the wireless system capacity and reliability can be enhanced without the need for increasing the power transmitted or using more spectrum. Despite a considerable amount of research have been done on the design of MIMO and diversity handset antennas, the design of low profile, small footprint and multi-standard (wideband or multiband) diversity antennas on handset devices remains a challenging issue. Therefore, the purpose of this thesis is to present new antenna structures for handset MIMO and diversity applications. As the MIMO antenna design can be conducted either using multiple element antennas (MEA) or isolated mode antenna technology (IMAT), the work in this thesis is fallen in these two general design themes (areas). The first area under investigation concerns multiport antennas (IMAT antennas). It has the following two contributions: • A novel dual-feed water-based antenna is designed from a low cost liquid material with a very high dielectric constant (pure water ). The isolation between feeds is achieved by two back to back L-shaped ground plane strips. A prototype is made and the optimised diversity parameters are obtained, the results show that this design has a good diversity performance over the frequency range of 2.4 – 2.7 GHz. • A new and low profile (h = 3 mm) planar inverted-F antenna (PIFA) with a coplanar-feed is presented. It has a wideband response over the frequency range of 2.35 – 3.25 GHz. The design is based on a comparative study on the mutual coupling between different feed arrangements. As a result, the coplanar feed is employed in the proposed antenna; the polarization diversity is achieved by exciting two orthogonal radiation modes. The isolation between the feeds is achieved by an L-shaped ground plane slot. Both simulated and measured results demonstrate that the design is a very good candidate for mobile diversity and MIMO applications. The second investigation area concerns multiple element antenna (MEA) systems for wideband and multiband handset applications. It includes the following contributions: • Three antenna systems of the planar inverted-L (PILA) antenna (h = 5 mm) are employed for wideband handset diversity applications over the frequency range of 1.7 – 2.85 GHz: 1) The first design has a dual-element PILA in which both the pattern and spatial diversities are employed; one antenna element is located on the upper edge of the ground plane while the other is located on the lower edge. 2) The second design represents a more compact dual-element PILA antenna in which the two elements are placed on the same ground plane edge (collocated on the same edge). The antenna isolation is achieved using a parasitic decoupling element inserted between the two elements. A novel approach for the design of the parasitic decoupling element is proposed. It is based on stepped impedance resonator circuit theory. As a result, more space is saved with this design (footprint = 385 mm2) over the first design (footprint = 702 mm2). 3) The third design is a four-element PILA system in which two antenna pairs (one pair at the upper edge which the other pair is located on the lower edge on the system PCB). All the prototypes are made and evaluated; the results show excellent diversity performance over the applications in the frequency range of 1.7-2.7 GHz. • A dual-element hexa-band antenna is proposed for smartphone MIMO applications. It consists of two elements: a hexa-band metallic frame antenna and a hepta-band PILA antenna coupled with a meandered shorted strip as an internal antenna. The isolation is achieved due to the resulted orthogonal radiation patterns, especially, at 0.85 GHz. The optimized antenna is made and tested and the results show that this design covers a hexa-band and is particularly suitable for GSM850/ DCS1800/ PCS1900/ UMTS2100/ LTE2500/ LTE3600 smartphone applications.