Report on Microstrip antenna array

In this work, 28GHz microstrip patch array antennas are studied. Designs of broadside pattern microstrip antenna arrays on Duroid are presented. First, an 8-element linear array is designed and its measured resonant frequency is 27.95GHz, which deviates 0.5% from the simulation. Broadside pattern is achieved in the H-plane while a unidirectional broad beam pattern is maintained in the E-plane. Measured gain of 9.4dBi is reported. Then a 16-element planar array is designed and it resonates at 28.06GHz. The side lobe levels are below -10dB and the cross-polarization levels are below -12dB in both planes. Gain is improved to be 17.6dBi. These array antennas set as my references in such high frequency antenna. Next, the shaped-beam pattern array is studied. A new synthesis method, which only controls the excitation phases, is employed so that design of arrays can be easily implemented. First, an 8-element linear microstrip patch array is designed on Quartz by using gold as a conductor and nickel as an interlayer. The resonant frequency is measured to be 27.5GHz, which deviates 0.8% from simulation. Shaped-beam pattern is achieved with 20′ tilted from the broadside. Its first side lobe level is -5dB and the cross-polarization level is -20dB in the H-plane. The measured gain of the array is 6dBi. Then another 8-element linear array, using gold/chromium as conductor/interlayer on Quartz substrate, is designed. Besides, compensation methods for discontinuities of the microstrip lines, such as chamfering the bends and altering the line widths near the junction, are employed in this design. It resonates at 28.1GHz. Its first side lobe level is -5dB and the cross-polarization level is -20dB in the H-plane. Shaped-beam pattern is maintained with tilted angle 25° from the broadside. Gain is measured to be 9.6dBi. Finally, two 8-element linear arrays are designed on Duroid. Both use curved microstrip lines to compensate for the losses but one uses l00Ω microstrip lines as the main feeding lines and the other uses 50Ω lines. For the l00Ω case, it resonates at 28.7GHz, which has 2% deviation from the simulation. The tilted angle is 20° from the broadside and shaped-beam pattern is maintained. The first side lobe level is -10dB and the cross-polarization level is -15dB in the H-plane. Gain is measured to be 9.4dBi. While for the 50Ω case, the resonant frequency is 28.1GHz, which has only 0.3% discrepancy from the simulation. Shaped-beam pattern is achieved with 25° tilted from the broadside…

Author: Tong, Ho Yin

Source: City University of Hong Kong

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