The main objective of this research work is to design a multiband, radiation pattern and frequency reconfigurable- based Two-Port Antenna Structure (TPAS) for 5G mobile terminal applications. Due to space constrain, antenna structures in the existing mobile phones are suffering from major drawback to operate in multiband including latest sub-6 GHz 5G frequency bands while performing the Frequency Reconfiguration (FRn) and Radiation Pattern Reconfiguration (RPRn) together. A novel technique of placing compact sized multiple antenna elements within a Single Port (SP) is proposed to achieve multiband, RPR and FR, while preserving the space to integrate the MIMO antenna technology in mobile terminals. As an initial design for this research, a single PIFA TPAS for mobile terminal was designed. Then, the remaining seven antenna designs were designed and categorized based on the number of antenna elements placed on a SP. Additionally, these designs were further classified under feasibility study category and DC biasing category, where artificial RF switches and PIN diode BAR50-02V are implemented, respectively. Rogers RT Duroid 5880 and FR4 material was utilized as the antenna substrate in feasibility study category and DC biasing category, respectively. Feasibility study category is divided into three stages: preliminary, analysis and optimization. Five antenna designs were designed under feasibility study: preliminary stage to analyze the effect of placing multiple antenna elements within a port in achieving multiband, FR and RPR. In addition, the influence of the slots on the antenna elements to achieve multiple bands was analyzed. Moreover, a proper technique to design microstrip-fed PIFA was analyzed to achieve sub- 6 GHz resonant frequencies. In overall, each antenna element within a port successfully achieves a minimum of dual band up to four bands. Moreover, RPR with Maximum Tilt Angle (MTA) of 248˚ between the antenna elements and FR with Maximum Frequency Range (MFR) of 10 GHz was obtained. Minimum realized gain of 2 dBi, minimum total efficiency of 62 % and Envelope Correlation Coefficient (ECC) values below 0.2 has been achieved. Next, under DC biasing category, a total of three antenna designs were designed and further analyzed by inserting the PIN diodes (touchstone blocks) and DC biasing circuit. Two prototypes were fabricated and validated with measurement results. Overall, each antenna element within a port achieves a minimum of triple band up to five bands successfully. Furthermore, RPR with MTA of 83˚ between the antenna elements and FR with MFR of 3.5 GHz is achieved.Minimum realized gain of 1.02 dBi, minimum total efficiency of 55 % and ECC values of less than 0.3 has been obtained. Furthermore, minimum multiplexing efficiency, ergodic capacity and Maximal Ratio Combining (MRC) gain of -2.48 dB, 9.6 bit/s/Hz and -3.2 dB have been achieved by these antennas. The main objective to achieve multiband, radiation pattern and frequency reconfigurable- based TPAS for 5G mobile terminal has been successfully concluded.
